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Essays arrive in groups rather than one at a time. The most recent group is below in full, and every earlier one after it, newest first.

Essays arrive in groups rather than one at a time, and a group usually opens up a subject not covered before. Between one group and the next nothing changes, so a reader who has seen the most recent group has seen everything.

30 October 2026

16 essays on fluids at work, transition and turbulence, ideal flow, flows and fields, viscosity, circulation and lift, what is taught wrongly, compressible flow and regimes and numbers

A travelling bubble's B-factor grows as the square root of its age, and the bubble turns heat-limited when it reaches B*. The vapour a growing bubble has made over the liquid it has cooled, against its age, in water at 80 °C under a tension 10 kPa below the vapour pressure, while inertia limits its growth; the dashed line is B, at which the cooling would use up the whole tension. B is 4.3 at a microsecond and 136 at a millisecond, and meets B = 31.6 at 53.8 µs, when its radius is 0.141 mm.

Fluids at work

A bubble is throttled by its age, and a sheet by its length

A cavity cools the liquid it boils, and the cooling lowers the vapour pressure it needed. Whether that matters was a question about one number, the B-factor — vapour made over liquid cooled — and no real cavity's was known. Computed, the two kinds a pump has are nothing alike. A travelling bubble cools a thin shell that thins further as it stretches, so its B grows as the square root of its age and reaches the critical value at Brennen's thermal time: a millisecond in water at 60 °C, four microseconds at the boiling point. An attached sheet keeps renewing the liquid it cools, so its B is a few, fixed by its length and speed. In warm water the bubbles are suppressed forty degrees before the sheet.

6 figures

The second gradient separates the layer soonest after a short release, latest after a dozen thicknesses, and sooner again after a long one. The distance past the second gradient's start at which the layer separates, in its thickness there, against the release's length in the thickness at the first release: Green's lagged layer, the same layer restarted at the second gradient with no memory, and the shape-only layer. Lagged: 2.91 after no release, 5.07 after 12 thicknesses, 3.95 after 60; with no memory, 3.16, 4.81 and 3.91.

Transition and turbulence

A layer's memory of one gradient helps it through the next, unless the next comes too soon

A turbulent layer released from an adverse gradient keeps the gradient's eddies for a dozen thicknesses, entraining more than its shape asks. Decelerate it again before they fade — behind the next compressor stage, or past a flap — and the question is whether that memory helps or hurts. Both, depending on when. A second gradient that arrives within about three thicknesses of the release meets a layer whose entrainment is still catching up, and it separates eight per cent sooner than a layer of the same shape with no history. One that arrives later meets eddies still working from the first gradient, and the layer holds on up to five per cent longer. The crossing sits at three thicknesses for every pair of gradients tried.

6 figures

On a NACA section thickness multiplies the lift by more than on a Joukowski section, by nearly one plus its thickness. The lift of a NACA four-digit section by panels over thin-aerofoil theory's, against its thickness: the 2412-type at 4°, and the symmetric section's lift slope over 2π; beside the Joukowski law 1 + 0.77 t/c. At 12 per cent the cambered section's factor is 1.115 and the symmetric slope's 1.101, against Joukowski's 1.092; at 18 per cent, 1.174 and 1.152.

Ideal flow

A NACA section multiplies its lift by nearly one plus its thickness, and a nose correction cannot supply it

On Joukowski's exact sections, thickness — which lifts nothing alone — multiplies the lift of camber and incidence by 1 + 0.77 t/c. Solved by panels, the NACA four-digit sections that real wings use do more: their lift slope grows as about 1 + 0.84 t/c, and a cambered 2412 lifts 11.5 per cent more than thin-aerofoil theory says. The more of the thickness sits near the nose, the more it multiplies. Added as thin-aerofoil theory adds them, the parts lose a quarter of the suction peak and put the centre of pressure two hundredths of the chord too far aft. Riegels's nose factor, the classical repair, makes the nose speed finite and moves the peak, and adds no lift at all: the missing lift is not a nose effect.

6 figures

A stagnation point hangs above the skin friction's saddle while the saddle is a separation, and is gone once it is not. Streamlines in the plane y = 0 of a wall flow with no axis of symmetry, at μ = 0.4: the wall's saddle of skin friction at x = -0.632, its node at 0.632. An interior stagnation point sits at height 0.15 above x = −0.5, and the saddle is a separation: the flow leaves the wall there.

Flows and fields

A stagnation point off the axis can land only on a saddle or a node, and turns it inside out

In a swirling flow onto a plate every stagnation point lived on the axis, so one sinking to the wall always met the wall's single critical point. Without the symmetry it might seem free to land anywhere — on an ordinary stretch of skin-friction line, leaving a pair of new points behind. It cannot. Divided by the height, the velocity is continuous down to the wall, where it becomes the skin friction, so a point can only reach the wall where the skin friction already vanishes. It lands on a saddle or a node, and the count does the rest: the point it lands on turns from separation to attachment. An oil-flow picture of the wall, which shows the same pattern before and after, cannot tell which it is looking at.

5 figures

Ideal flow

A block's front face is pulled upstream by its own lip

A forward-facing step's face is pushed at its foot and pulled at its lip by exactly equal amounts. Give the step a back — make it a block on the floor — and the balance goes. The two lips, a short top apart, each sit in the other's fast flow, and the suction at the front lip grows while the push at the foot hardly changes: a block as long as it is tall has its front face pulled upstream by three tenths of the dynamic pressure times its height, a block a quarter as long by two thirds. The back is pulled downstream by exactly as much, so the ideal block still has no drag; but every force that ideal flow assigns is now on the wrong face for separation to undo.

6 figures $Kicked at ninety per cent of its peak flow, the compressor is held only when both modes have an actuator. The flow through the compressor, as a fraction of the peak flow, after a stall cell of amplitude 0.05 is started at 90 per cent of the peak flow, at B = 2, under four controllers: a tip injector of gain 0.7 and capacity 2 per cent of the peak flow with the throttle fixed; the injector with a pressure-driven throttle; the pressure-and-flow throttle with no injector; and both. injector, throttle fixed: surges or runs away; injector, pressure throttle: surges or runs away; throttle pair, no injector: stalls; injector and throttle pair: recovers.$ Fluids at work

A compressor needs one actuator for each way it can fail

A throttle alone cannot hold a compressor left of its peak in a large plenum: it has one degree of freedom and the machine has two ways to fail, and the throttle's own surge gain runs into a ceiling that the plenum's size does not move. Give the stall cell its own actuator — air injected at the rotor tips against the cell — and give the throttle a second signal, the flow, and a machine at B = 2 is held at ninety per cent of its peak flow, recovering from a kicked cell nearly three times the injector's capacity. Let the injection lag the cell by a radian and the line still holds, but almost no disturbance is survived.

6 figures

A sphere two per cent larger overtakes its neighbour round a path that is its own mirror image, and leaves at the offset it came in at. The centre of a sphere two per cent larger than its neighbour, relative to the smaller sphere, as it overtakes it in a viscous liquid, from four horizontal offsets; the circle is the distance at which they would touch. Each path bulges outward as it passes and is symmetric about the smaller sphere's level: from 0.85, 1.5, 2.5, 4 radii the larger sphere leaves at 0.8499, 1.5, 2.5, 4, after closest approaches of 2.27, 2.83, 3.74, 5.15 radii.

Viscosity

A larger sphere overtakes its neighbour and leaves on the line it came in on

Two equal spheres settling together never change their shape. Make one of them two per cent larger and the pair becomes an encounter: the larger sphere sinks past the smaller round a path that bulges out and comes back, slowed sixteenfold at contact but never stopped, and it leaves at exactly the offset it arrived with. The smaller sphere swings seven radii sideways while the larger is above it and gives every radius back while the larger is below. In Stokes flow, meeting a neighbour displaces nothing — unless the spheres touch, and a hundredth of a radius of roughness is enough to make every touching path leave on the same line.

6 figures

Circulation and lift

A stiffness floor keeps the span and gives the tips their load back

A spar sized by strength alone thins to nothing at the tips, and charged as lift it stops the best span where it weighs a quarter of everything the wing carries, with the tips a little unloaded. A real outer wing is sized by stiffness, and stiffness sets a floor under the spar's weight that no reduction of the tip load can lower. Put that floor in and the tips get their load back — the best loading slides from a sixth of the way to the bell towards the ellipse — the quarter does not survive, rising to two fifths as the floor spreads over the outer two thirds of the span, and the span itself barely moves. A weight per metre cannot stop a span.

6 figures

An oval that sheds its fluid is braked less, so the pair sinks further and stops later, until it sheds too fast to stop at all. The depth of a trailing vortex pair below its starting level, in spacings, against time in spacings over its initial speed, in air of N = 0.22: Saffman's oval, which keeps its fluid, and one detraining with α = 0.05. Saffman's stops at depth 6.75 after 10.6; this one at 6.93 after 12.4.

What is taught wrongly

A wake that sheds its fluid sinks further, and past a point does not stop

In stable air the pair of trailing vortices behind a wing carries a column of lighter air down with it, and buoyancy pushes the column back until the pair has given up its momentum and stops. That picture keeps every parcel of the column. A real pair sheds the light air as it sinks, and shedding does two things at once: it takes away part of the momentum the buoyancy had to return, and it takes away the buoyancy that was returning it. The second wins. A pair that sheds a little stops later and deeper; one that sheds faster than a threshold loses its column before buoyancy can stop it. The shed air keeps a quarter of the momentum swinging up and down behind the aeroplane.

6 figures

At its design Mach number the biplane's channel lifts nothing: all its lift is on the two outer faces. The lift coefficient of the pair at 2° incidence against Mach number, per unit of one element's chord, beside what the two outer faces give alone, 4α/β, and two isolated flat plates, 8α/β. At the design Mach number, 1.944, the pair's lift is 0.08378 and the outer faces' 0.08378: the channel's net lift is zero to rounding. At Mach 1.7 the channel adds 13.9 per cent, at 2.2 21.1.

Compressible flow

Busemann's biplane lifts only on its outer faces, and its channel turns the lift into a quarter-chord load

Tilt Busemann's biplane to make it lift and the same cancellation that removed its wave drag removes the lift of its channel: at the design Mach number the waves the incidence sends across the gap meet and cancel just as the thickness's did, and every bit of lift is carried by the two outer faces — half what two separate plates would give. The channel does not go idle. It carries a couple, lift on the front half and download on the rear, which moves the centre of pressure from mid-chord, where every supersonic plate has it, to the quarter chord. The pair pays for its lift two and a half times as steeply as flat plates do, and still beats a diamond fourfold.

7 figures $A flicker of a few per cent empties the suspension band and drains Stommel's traps more slowly. The share of a cloud released over one cell that is still within four cells of its start after the run, against the flicker's standard deviation as a fraction of the cells' mean strength, with a memory of three turnovers: inertialess particles falling at 0.3 of the cells' speed in still air, held in Stommel's traps, and particles of Stokes number 3 falling at 0.1, held in the suspension band. Stommel's traps hold 0.52, 0.41, 0.33, 0.16, 0.03, 0; the suspension band 0.22, 0.055, 0.015, 0.015, 0.005, 0, at flickers of 0, 0.05, 0.1, 0.2, 0.35, 0.5.$ Regimes and numbers

Flickering vortices cannot hold a settling particle up, and still make it fall faster

A steady lattice of vortices can do two things to a heavy particle settling through it: hold it up, on closed paths or on orbits of its own, and speed its fall, by flinging it into the down-draughts. Let the vortices strengthen and fade at random, as real eddies do, and the two come apart. A flicker of five per cent of the cells' strength empties three quarters of the band of particles held up by their inertia; a flicker of a third drains Stommel's traps almost entirely. The speed-up hardly notices a flicker of a tenth, and is halved only when the cells swing by half their strength and remember it for a few turnovers. Trapping needs a steady cell; the speed-up does not.

5 figures

Surges merge down the chute until about four hundred time units, and then the train stops merging. The number of surges on a periodic chute 200 units long against time, after uniform flow at Froude number 3 is seeded with depth noise, at two resolutions, eddy viscosity 0.05. At the finer the count is 71, 55, 45, 45, 45 at times 100, 200, 400, 700 and 1000 — a spacing of 4.44; at the coarser, 63, 45, 32, 30, 30, a spacing of 6.67.

Flows and fields

Roll waves stop merging at a spacing their fronts choose

On a steep chute the uniform flow breaks into a train of surges, and the train coarsens: a taller surge runs faster, catches the one ahead and swallows it, so the spacing grows down the chute. If the merging never stopped, the spacing in a photograph would only record how far the water had come. Marched down a long channel from noise, it stops. After a few hundred units of travel the surges stop catching each other and the train keeps its spacing for as long as it is followed. The spacing it keeps is not set by the chute or the noise but by the dissipation inside the surge fronts — which is the one part of the flow the shallow-water equations describe only roughly.

5 figures

Through the transitional range Nikuradse's sand pipe runs below Colebrook's curve by up to a fifth. The friction factor against the Reynolds number for a pipe of relative roughness 1/120, with Nikuradse's roughness function and with Colebrook's, beside the smooth pipe. Nikuradse's falls furthest below Colebrook's, 21.9 per cent, at a Reynolds number of 11318, where the roughness is 6 wall units; both reach 0.0356 when fully rough.

Transition and turbulence

Sand and a commercial pipe part company at six wall units

A rough wall shifts the logarithmic velocity profile down by an amount that depends on the roughness height in wall units, and once the wall is fully rough every kind of roughness shifts it the same way. Before that they disagree. Nikuradse's uniform sand stays smooth until its grains reach four wall units and then rises steeply; Colebrook's commercial pipes feel grains a fifth of a wall unit high and rise smoothly. Put both into one log law and the friction factor of a pipe through its transitional range differs by up to a quarter, always at the same roughness in wall units, about six. The Moody chart, drawn from Colebrook, is the upper of the two.

5 figures

A five per cent distortion gives six blades a tone that no longer falls with the tip's speed, and two blades hardly notice. The sound power of the blade-passing fundamental against tip Mach number, thrust and shaft power held, for two and six blades: from the steady load, and from the thrust's fluctuation as each blade cuts an inflow distortion of 5 per cent rms. At tip Mach 0.4 six blades give 100 dB from the steady load and 113 from the distortion; two blades 127 and 109. The six-bladed steady tone overtakes its distortion tone at tip Mach 0.593.

Compressible flow

A distorted inflow gives back the tone more blades took away

A propeller's steady thrust sings through a Bessel function whose order is the number of blades times the harmonic, and that function is exponentially small at low tip speeds — which is why six blades are quieter than two. But a blade that cuts a non-uniform inflow carries a thrust that changes round the circle, and its s-th harmonic radiates through a Bessel function of order six minus s. The sixth needs no tip speed at all. A distortion of five per cent turns six blades' tone into one that hardly falls as the tips slow, fills the axis where the steady tone is silent, and cuts the six-blade advantage over two from twenty decibels to thirteen. Two blades never notice.

6 figures

Pressed with one load, a steeper blade leaves a thinner film, and without a land a steep one cannot float at all. The film a loaded scraper leaves on the surface, in micrometres, against the angle its face makes with the surface, at a load of 100 N per metre of span on an ink of 0.1 Pa·s moving at 5 m/s: with a flat land 0.1 mm long under the edge, and with none. With the land the film is 110 µm at 10°, 1.69 at 30° and 0.268 at 60°. Without one it is the whole gap, 145 µm at 8°, and above 44° the gap the load needs is below a ten-thousandth of a nanometre: the edge is in contact.

Viscosity

A pressed blade floats on its land and leaves half the gap behind

A scraper or a doctor blade is not held at a gap; it is pressed on with a load, and it rises until the liquid it lets through carries that load. Without a flat land under its edge the liquid can carry it only through the corner's logarithm, so the gap falls exponentially with the load, and a blade steeper than about forty-four degrees cannot float at a working load at all — its edge is in contact. Give it a land a tenth of a millimetre long and the film becomes half the gap, falls as one over the load, and is a quarter of a micrometre at sixty degrees. The land is also why a blade's film grows as its edge wears.

6 figures $A strut two fifths of the way out halves the spars of a box wing; near the root or the tip it buys little. The flange volume of both spars of Prandtl's best box at a gap of a fifth of the span, with one strut on each side joined rigidly to both spars, over the volume with none, against the strut's station as a fraction of the semi-span, for struts a tenth as stiff in bending as a spar, as stiff, and ten times stiffer. For a strut as stiff as a spar the least is 0.5 at 0.4 of the semi-span; at 0.1 and 0.9 it is 0.839 and 0.929.$ Circulation and lift

A strut inside a box wing is invisible to the wake, and halves the spar

Prandtl's best box wing has, everywhere inside it, air moving straight down: no sideways flow at all. A strut joining its two wings anywhere along the span therefore meets no flow it could turn, carries no load, and leaves the induced drag exactly where it was — the wake cannot see it. The spar can. A strut two fifths of the way out, as stiff as a spar and rigidly joined, halves the flange material of both spars, though it is pushed and pulled by almost nothing: the two wings lift equally and bend together, so the strut works through its joints, and a pinned one does nothing. Its only aerodynamic price is friction, and a slim strut pays it.

6 figures

Before that

Everything published earlier, newest first. Titles only — the cards are on the full listing.

25 October 2026

18 essays on flows and fields, viscosity, fluids at work, ideal flow, compressible flow, what is taught wrongly, regimes and numbers, circulation and lift and transition and turbulence

A gas's viscosity ignores its pressure until the free path reaches the walls — flows and fields
A levitator lifts by its amplitude, not its gas — viscosity
The layer every airway restarts bends Murray's cube towards the turbulent pipe's — fluids at work
Thickness carries no load of its own and still moves the load forward — ideal flow
A driver reaches the best drive only by striking upward — fluids at work
A flap that closes the mouth starts Busemann's biplane below its design point — compressible flow
A mica sheet hides its glue only at the smallest gaps, and changes how the false slip falls — what is taught wrongly
A round jet hands its wall jet a strength proportional to its throw — viscosity
A stagnation point can leave the flow through the wall, and the count is kept by halves — flows and fields
A step's face is pushed at its foot and pulled at its lip, equally — ideal flow
A thinning gas flows least at one free path across, and then more without end — regimes and numbers
A wing that cannot hold its suction gains little from its span — circulation and lift
Noise in every frame is a memory of zero, and the run cannot measure it at its own pace — transition and turbulence
A liquid with one relaxation time rings in a tube, and a spectrum of times silences it — regimes and numbers
A prior chosen from noisy pictures keeps most of its gain, and a wrong one loses its alibi — what is taught wrongly
A spar that must lift itself stops the span at a quarter of the weight — circulation and lift
The shock layer is Hill's vortex, and it heats the nose a tenth harder than Newton says — compressible flow
Two spheres settling at a slant keep their slant for ever, and three do not — viscosity

21 October 2026

18 essays on flows and fields, viscosity, ideal flow, fluids at work, compressible flow, transition and turbulence, circulation and lift, regimes and numbers and what is taught wrongly

A bowed meniscus keeps most of its slip until the groove floods — flows and fields
A scraper held flat is pushed off the wall it scrapes — viscosity
Plating that gives way slows the water that slams it, but only on a flat bottom — ideal flow
The run moves the best drive below the ridge that carries furthest — fluids at work
A blunted nose delays its cone's transition only so far, and the correlation decides how far — compressible flow
A layer released from a gradient overshoots the shape it left — transition and turbulence
A pivoted wingtip follows the lift only with no spring stiffness and no camber — circulation and lift
A stalled plate keeps a quarter of its lift slope and moves its centre aft — ideal flow
A trip deeper than the film's window flips the bearing twice a cycle — viscosity
An edge no observer can move still depends on what it is averaged against — flows and fields
Below separation a cylinder's drag is a Stokes layer, and KC stops deciding the force — regimes and numbers
Free to rise and fall, a ground-effect craft rides its own cushion over the swell — what is taught wrongly
The cheapest fork loses only its sideways speed, and pricing it closes the fork — fluids at work
A camera zoomed into the cascade needs frames faster than its window remembers — transition and turbulence
Followed rather than held, the parcels near a wing nearly tie — what is taught wrongly
Inertia empties the vortices that would hold a settling particle, and then speeds its fall — regimes and numbers
More blades hush a propeller only while its tips are slow — compressible flow
Sweep slows a wing root's gust cycles and leaves their excess over the lift — circulation and lift

19 October 2026

20 essays on ideal flow, transition and turbulence, regimes and numbers, what is taught wrongly, flows and fields, fluids at work, viscosity, compressible flow and circulation and lift

A hull bottom feels the slam it has time to answer — ideal flow
A wandering forcing leaves the averaged four-fifths law alone — transition and turbulence
Over a plate in mercury the warm layer flows as if inviscid — regimes and numbers
Stable air takes back the momentum a wing pushes down — what is taught wrongly
A cloud folds where a saddle is strong, not when — flows and fields
A drive's best spin falls where players hit it only because lift tires and drag grows — fluids at work
A jet striking a plate leaves a stronger wall jet the further it travelled — viscosity
A swell lifts a ground-effect wing more at its crests than it takes in its troughs — what is taught wrongly
Compression behind the lip is bought by opening the throat — compressible flow
Laid flat, a warm plate is pushed by the pressure of its own layer — regimes and numbers
One wing root feels the rolling gust its lift cannot — circulation and lift
The camera needs the window's memory, not the probe's — transition and turbulence
The sea-breeze front runs till evening only near the equator — ideal flow
A blunted cone eats its nose's sheath in a few hundred radii — compressible flow
A layer whose stress lags the gradient separates sooner — transition and turbulence
A wand that lags its sea makes flying level the better bet — fluids at work
A wing that twists with its speed washes out the wrong way — circulation and lift
Above a warm wire the plume speeds up as it rises — regimes and numbers
The side that turns turbulent first decides who arrives first near the wall — what is taught wrongly
A wire sings with the force on it, not the flow round it — compressible flow

14 October 2026

19 essays on ideal flow, regimes and numbers, flows and fields, what is taught wrongly, transition and turbulence, viscosity, circulation and lift, compressible flow and fluids at work

A light hull slams softly, and a round one does not — ideal flow
A steel wall lengthens a sodium entrance by half — regimes and numbers
A stronger strain folds a cloud only if it lasts — flows and fields
Inside the layer the upper parcel leads by more — what is taught wrongly
What holds the shear decides whether the waves last — transition and turbulence
A nose at incidence makes its vorticity along the flow — flows and fields
A slow bush quickens the hunt it cannot start — viscosity
At higher orders the bottleneck hides intermittency — transition and turbulence
Behind a finite wing the wake face keeps its share — what is taught wrongly
Between fixed ends the transparent tree is the quiet one — regimes and numbers
One twist is chosen for the speed flown per metre — circulation and lift
The last shock should be the weakest — compressible flow
The meniscus slows the finger and hardly moves it — ideal flow
Two small pumps carry two big discs — fluids at work
A bending moment never chooses a span — circulation and lift
A jet along a wall keeps the flux of its momentum flux — viscosity
A noisy flame is still speeding up a hundred wavelengths wide — flows and fields
Moody's fifth root is true at one size — fluids at work
The cowl caps what the ramps can buy — compressible flow

5 October 2026

20 essays on viscosity, what is taught wrongly, fluids at work, transition and turbulence, regimes and numbers, ideal flow, flows and fields, circulation and lift and compressible flow

A point force makes a jet only when it is strong — viscosity
A wing over the sea barely touches it — what is taught wrongly
The terminal speed sets the best launch angle — fluids at work
The wake is a tenth of the velocity and a third of the displacement — transition and turbulence
Viscosity lets a jet break, later and into bigger drops — regimes and numbers
Water climbs a falling wedge, and the load comes from the climbing — ideal flow
Wobbling saddles keep the quarter, and raise it — flows and fields
A load carried to the trailing edge needs a hook — circulation and lift
A spinning ball should leave low — fluids at work
A swept wall makes vorticity along its isobars, not across its flow — flows and fields
An adverse gradient grows the wake, not the log law — transition and turbulence
Busemann's biplane has to be flown past its design point — compressible flow
The air shortens a jet's fastest ripple, and the drops follow — regimes and numbers
The fastest finger is set by the gap and one number — ideal flow
The upper parcel leads by the circulation — what is taught wrongly
The warm side pulls a bubble with no force on it — viscosity
A cap that slows a rising bubble stops a migrating one — viscosity
The cheapest turbulent pipe follows two and a half, not three — fluids at work
The more small bubbles a cloud holds, the later it turns fast — compressible flow
Washout is right at one lift coefficient — circulation and lift

2 October 2026

20 essays on transition and turbulence, flows and fields, what is taught wrongly, fluids at work, ideal flow, circulation and lift, viscosity, regimes and numbers and compressible flow

A thin interface keeps its waves past a quarter — transition and turbulence
A lattice of vortices folds a cloud at the saddles' quarter — flows and fields
A soft wall is read as slip only at second order — what is taught wrongly
A throttle can hold the peak only in a small plenum — fluids at work
A trailing wake hurries a pair together — ideal flow
No elevon reaches past a quarter chord — circulation and lift
The gas sets a squeeze film's loss, not its stiffness — viscosity
The longest thermal entrance belongs to neither metal nor gas — regimes and numbers
The summit forgets the forcing before the dissipation does — transition and turbulence
A cold wall holds its layer on longer — compressible flow
A crevice keeps the nucleus a free bubble loses — what is taught wrongly
A foil in a random sea follows it up to its peak — fluids at work
A sloping shelf puts the swell's current three Ekman depths down — flows and fields
A strained vortex loses its ring at the limit of what it holds — ideal flow
A thousandth of a monolayer holds a bubble still — viscosity
A wake held at the stern keeps the bulb and loses the lean — regimes and numbers
A wing averages a gust through its own loading — circulation and lift
Decaying flows end on the sinh side — transition and turbulence
A wandering flock passes no error down the V — circulation and lift
Above their resonance, bubbles make water faster — compressible flow

30 September 2026

20 essays on transition and turbulence, what is taught wrongly, flows and fields, viscosity, circulation and lift, fluids at work, ideal flow, regimes and numbers and compressible flow

A cloud grows out of its bursts and keeps their shape — transition and turbulence
A crown dissolves its nuclei or breaks on them, and fast — what is taught wrongly
Drag decides whether a cloud folds, and the air decides at what — flows and fields
A bulk viscosity holds a shock together until it splits — viscosity
A coast sends the drift back, or sends it along — flows and fields
A flapping follower can drift fore and aft, but not sideways — circulation and lift
A foil flies level through a short sea and follows a long one — fluids at work
A viscous nanometre reads as slip until the gap is ten of it — what is taught wrongly
Drag makes every free pair meet — ideal flow
Frames that share their eddies count as one — transition and turbulence
The stern's wake puts the bulb at the bow — regimes and numbers
A free waist needs half the depth, and the sweep costs it nothing — ideal flow
A post holds liquid back by its radius, a stripe by its length — flows and fields
A prior the pictures can refute is the one worth having — what is taught wrongly
A tree transparent at every junction is not the quietest — regimes and numbers
A warm bush stops the bearing hunting — viscosity
The air a cavity releases is capped by the cavity — fluids at work
The sheath outlasts the body — compressible flow
The tail a canard needs costs more than the canard saves — circulation and lift
The gas a reflected shock refuses is inside the layer — compressible flow

28 September 2026

20 essays on what is taught wrongly, regimes and numbers, viscosity, flows and fields, transition and turbulence, ideal flow, circulation and lift, fluids at work and compressible flow

A river drifts right, and only a reach can show it — what is taught wrongly
A sliding drop is held harder the faster it goes — regimes and numbers
A slow sensor makes the bearing cycle — viscosity
A squeezed tube is held open by its own fluid — flows and fields
Bursts and memory pull a cloud both ways — transition and turbulence
A free pair turns, and forty-five degrees decides — ideal flow
A parcel goes straight while the streamlines curve — flows and fields
A rounded edge spills before its line goes round — what is taught wrongly
A snapshot counts areas, and a flow counts its edge — transition and turbulence
A stratified sea blocks a current sooner and traps less — regimes and numbers
A third surface is worth a square — circulation and lift
An ejector's nozzle exit is a condition, not a choice — fluids at work
The heat of a squeeze leaves across the gap — viscosity
A foil under the surface flies with a phantom — fluids at work
A tailored tube buys its test time with its driver — compressible flow
A waist moves the overspeed and cannot remove it — ideal flow
Four vortices bend faster, and bend the wrong one — circulation and lift
The hull Michell's integral prefers — regimes and numbers
The largest bulk viscosity is the first to expire — viscosity
A cone intake's shock sees the whole capture — compressible flow

26 September 2026

20 essays on what is taught wrongly, ideal flow, transition and turbulence, viscosity, circulation and lift, flows and fields, compressible flow, fluids at work and regimes and numbers

A melt's slip length has an exponent it cannot choose — what is taught wrongly
A pair set free in a stream collides or parts — ideal flow
A pair's memory shapes the cloud it spreads into — transition and turbulence
A rotor's inertia slows the jump and cannot make it ring — viscosity
The follower beats in time with the wake, not the bird — circulation and lift
The pressure a parcel remembers keeps it finite — flows and fields
A box wing's fins earn their keep in the spar — circulation and lift
A broken line empties at the pace of its friction — compressible flow
A degassed siphon is as tall as its largest nucleus allows — what is taught wrongly
A duct beats Betz only on the area it chooses — fluids at work
A flame's speed limit holds only in silence — flows and fields
A fuselage lowers its wing root's critical Mach number — ideal flow
A thin fibre coats by its own radius, and beads by it — viscosity
Forcing at the integral scale leaves the cascade alone — transition and turbulence
Murray's law passes the pulse where the pulse is viscous — regimes and numbers
A canard pays for its stability in induced drag — circulation and lift
Air at a valve softens the hammer only in quantity — fluids at work
At thirty degrees the Earth keeps time with the sea breeze — ideal flow
The gas beside a hypersonic body remembers its nose — compressible flow
An overexpanded nozzle lets go before its shock arrives — compressible flow

25 September 2026

19 essays on circulation and lift, viscosity, transition and turbulence, flows and fields, fluids at work, ideal flow, what is taught wrongly, regimes and numbers and compressible flow

A fair V is a curved V — circulation and lift
A motor turns the runaway into a jump — viscosity
A sloping ceiling drips downhill, or not at all — transition and turbulence
A vortex pair carries eddies no snapshot can see — flows and fields
A washed filter works as long as it rests — fluids at work
The paradox is for the pair, not for each body — ideal flow
The throttle plate is a wet bulb for petrol — what is taught wrongly
A hydrofoil loses most lift on the way up — what is taught wrongly
A strained vortex holds until it has no shape to hold — ideal flow
A torn film still pulls — viscosity
A wrinkled flame has one cusp and a speed limit — flows and fields
Leapfrogging rings end by merging, not by parting — circulation and lift
Murray's law is not the rule for a pulse — regimes and numbers
One fast pump or two slow ones — fluids at work
Oxygen makes a boom's crack, nitrogen its rise time — compressible flow
The streamfunction says which relaxed state — transition and turbulence
A hypersonic body leaves a line explosion behind it — compressible flow
The force a contact line holds is a range — regimes and numbers
The plenum decides whether a compressor surges — fluids at work

24 September 2026

18 essays on fluids at work, flows and fields, compressible flow, viscosity, circulation and lift, transition and turbulence, what is taught wrongly, ideal flow and regimes and numbers

A duct is worth the square root of two — fluids at work
A flat flame is unstable at every size — flows and fields
A pipe cannot hold its gas at the wall's temperature — compressible flow
A viscosity the flow cannot decide — viscosity
A wake ends by bending, not by fading — circulation and lift
How far apart a ceiling drips — transition and turbulence
The Earth bends every river a little — what is taught wrongly
Two eddies can stand behind a cylinder, but not for long — ideal flow
A filter is slowed by what it has caught — fluids at work
A lost steady state still holds the film — viscosity
A vortex is a waveguide — ideal flow
Carburettor ice is made by the fuel, not the venturi — what is taught wrongly
Every snapshot says vortex, and every particle leaves — flows and fields
The best estimate of a scale assumes its shape — transition and turbulence
The bird at the point pays for the V — circulation and lift
The fireball is hollow — compressible flow
The hill a slow current will not climb — regimes and numbers
Hull speed is not the hump — regimes and numbers

23 September 2026

16 essays on flows and fields, circulation and lift, what is taught wrongly, ideal flow, regimes and numbers, transition and turbulence, viscosity, fluids at work and compressible flow

A gradient left to itself — flows and fields
The aeroplane rises out of its own gust — circulation and lift
The borrowed mass that goes negative — what is taught wrongly
The cell draws a larger cylinder — ideal flow
The drop falls at a fold — regimes and numbers
The further apart, the faster they part — transition and turbulence
A flow pinned between two guesses — viscosity
A law that is exact as an average — regimes and numbers
A record is as long as its integral scales — transition and turbulence
An edge holds any angle it is given — what is taught wrongly
The air flows in against the heat — flows and fields
The rudder pays for the keel's wake — fluids at work
The shock that passes without an echo — compressible flow
The span takes away the infinity, not the gust — circulation and lift
Thickness costs a fuselage far less than a wing — ideal flow
A drop rings like a bell — regimes and numbers

19 September 2026

20 essays on viscosity, transition and turbulence, what is taught wrongly, compressible flow, regimes and numbers, fluids at work, flows and fields, circulation and lift and ideal flow

A damper that turns into a spring — viscosity
A ball that bounces in water and not in oil — viscosity
A cascade that arrives as stripes — transition and turbulence
A length you can only measure by squeezing — what is taught wrongly
One curve for every thickness — compressible flow
The best a tube can do is its own radius — regimes and numbers
The current that runs across the river — fluids at work
The tangent that sizes a plant — flows and fields
A drag that needs a discontinuity — compressible flow
A stroke is worth the area it encloses — viscosity
An equilibrium a three-dimensional flow cannot have — transition and turbulence
One coefficient, two errors — circulation and lift
The depth at the edge is not the critical one — fluids at work
The drag that can only see one curve — ideal flow
The wall a melt really does slip on — what is taught wrongly
Transport with nothing transported — regimes and numbers
When the flux outruns the pressure — flows and fields
A cavity that cools the water it came from — fluids at work
A shock that will not stand still — compressible flow
Two drags, or nothing swims — viscosity

17 September 2026

17 essays on what is taught wrongly, flows and fields, fluids at work, regimes and numbers, compressible flow, circulation and lift, transition and turbulence and ideal flow

A choked throat buys time, not silence — what is taught wrongly
The drift that turns a current into rolls — flows and fields
The nozzle that is best at one thing — fluids at work
The pulse that has to travel — regimes and numbers
The floor that gives the drift back — flows and fields
The pulse that grows as it leaves the heart — regimes and numbers
The spot a local theory cannot see — what is taught wrongly
The wall the suction puts in the curve — fluids at work
A boom is aged in the thin air it starts in — compressible flow
A choke that belongs to two streams — fluids at work
A lighter spar turns a box wing into a biplane — circulation and lift
Four cameras and a field they cannot see — what is taught wrongly
The decay inside the four-fifths law — transition and turbulence
The heat the eddies do not carry — regimes and numbers
The pump that is better the more it squeezes — flows and fields
Past three, an ellipse is a shear layer — ideal flow
Two rings leapfrog only if they start alike — circulation and lift

15 September 2026

9 essays on transition and turbulence, viscosity and compressible flow

Universal, and one of five — transition and turbulence
The constant that travels — transition and turbulence
The solution that keeps its nonlinear term — viscosity
One channel, one flux, two flows — viscosity
The carpet an accelerating aeroplane folds — compressible flow
The fraction that is really four thirds — transition and turbulence
A relation with no turbulence in it — transition and turbulence
The edge is a rumble, not a quieter bang — compressible flow
Why the list is this long — viscosity

14 September 2026

18 essays on compressible flow, what is taught wrongly, flows and fields, fluids at work, transition and turbulence and regimes and numbers

A cone finishes its turn after the shock — compressible flow
The face Newton left in shadow — what is taught wrongly
The sign a stagnation point carries in space — flows and fields
Twice the margin, on top of the hammer — fluids at work
Matched at one speed and at no other — fluids at work
The drag a wake keeps however it rolls up — what is taught wrongly
The drift a rotating planet takes back — flows and fields
The profile Rayleigh cleared and viscosity did not — transition and turbulence
Three readings, and the one each answer leans on — compressible flow
Between hover and twice the hover inflow — fluids at work
The column the chord rule cannot settle — flows and fields
The gradient the heat never hears — compressible flow
The venturi that stops listening downstream — what is taught wrongly
A wave on the wall is a pump — flows and fields
The boom that turns back before the ground — compressible flow
The drop a no-slip wall would never let spread — what is taught wrongly
The gusts that cancel along the chord — regimes and numbers
The specific speed a pump spends its life at — fluids at work

12 September 2026

20 essays on what is taught wrongly, fluids at work, flows and fields, compressible flow and transition and turbulence

Where a liquid does pull — what is taught wrongly
A breaking strength that is the size of a flaw — what is taught wrongly
The margin friction lends a siphon — what is taught wrongly
The air that breaks a siphon nothing else can — what is taught wrongly
A cushion that changes its physics — what is taught wrongly
A tank that turns a hammer into a swing — fluids at work
The borrowed mass the boundary decides — what is taught wrongly
The better tunnel needs the bigger tank — fluids at work
The vorticity a clean surface cannot refuse — flows and fields
The window every vector is averaged over — what is taught wrongly
A breeze the boat cannot use — fluids at work
One view is enough, and the axis pays for it — what is taught wrongly
The jet a cone sprays sideways — compressible flow
Twice as slippery along as across — flows and fields
A keel flies wherever the course puts it — fluids at work
A wall puts in exactly its own speed — flows and fields
Friction moves the sonic point past the throat — compressible flow
The teapot effect is a tension, not a pressure — what is taught wrongly
The truncation that cannot carry three times the heat — transition and turbulence
Hexagons remember how the heat was turned up — transition and turbulence

10 September 2026

20 essays on what is taught wrongly, fluids at work, flows and fields and compressible flow

The one place the atmosphere pushes — what is taught wrongly
The siphon that does not break — what is taught wrongly
A roll that feeds itself — what is taught wrongly
A stall that is a place — what is taught wrongly
A force forgets the datum, a stress cannot — what is taught wrongly
The only theory simple enough to optimise — what is taught wrongly
Weighing what is missing — what is taught wrongly
The cushion that is there after all — what is taught wrongly
An instrument that takes a derivative — what is taught wrongly
The paint that measures the wrong field — what is taught wrongly
The duty that had no machine — fluids at work
The count computed on a body — flows and fields
The group with no head in it — fluids at work
Two kinds is a plane flow's privilege — flows and fields
What a turning frame keeps — fluids at work
The line the dye actually draws — flows and fields
The stress that picks the aerodynamics — fluids at work
The curve that measures a gradient — flows and fields
The skin that lags the flight — compressible flow
The thermometer that heats itself — compressible flow

5 September 2026

50 essays on what is taught wrongly, flows and fields, fluids at work, compressible flow, transition and turbulence, viscosity, regimes and numbers, circulation and lift and ideal flow

A calculation with no memory in it — what is taught wrongly
The shutter is part of the answer — what is taught wrongly
The same statistics, and a different load — what is taught wrongly
The bath that was only ever a wait — what is taught wrongly
Two strainings, and the order they came in — flows and fields
A scalar is a record of where its fluid was — flows and fields
The part of the closure a pipe cannot see — fluids at work
A drift made of two things that average to zero — flows and fields
The outlet is the inlet, a while ago — fluids at work
A boundary that only exists over a window — flows and fields
A gas that has not finished being shocked — compressible flow
A threshold that is also a duration — fluids at work
A surface that remembers the diaphragm — compressible flow
The ball that never forgets its spin — fluids at work
What a mean profile cannot tell anybody — flows and fields
How long the fluid has been in there — flows and fields
The sound now is the source then — compressible flow
A duct that cannot be run backwards — compressible flow
A puff that does not know how old it is — transition and turbulence
A gas that has not decided to react yet — compressible flow
How far downwind a surface is remembered — transition and turbulence
A dissipation that lags its production — transition and turbulence
Two totals, one of which a shock cannot touch — compressible flow
A closure with no memory at all — transition and turbulence
A dissipation correlated across every scale — transition and turbulence
The drag that integrates a whole history — viscosity
Two forces, and only one of them remembers — regimes and numbers
A wake that keeps the drag and forgets the body — transition and turbulence
The state a machine was started into — regimes and numbers
The wall the fluid is listening to — viscosity
A wake told what to do — regimes and numbers
The fluid that has not finished its last deformation — viscosity
A layer that is an integral of everything upstream — viscosity
Slip is a memory of one mean free path — regimes and numbers
The lag that makes flutter possible — circulation and lift
A particle is a low-pass filter — regimes and numbers
How long a fluid takes to forget it was not rotating — viscosity
The drift was the instrument — ideal flow
Two lifts at one incidence — circulation and lift
A duct that forgets everything but one number — viscosity
A spiral is a legible record — ideal flow
A wake that says what made it — circulation and lift
Every memory number is one time over another — regimes and numbers
A blade that flies through what it shed — circulation and lift
Reversible, and unusable — ideal flow
A row that meets the row before it — circulation and lift
Everything about the start, except one vector — ideal flow
Nothing in the present picks the flow — ideal flow
The inflow that takes time to arrive — circulation and lift
The theory with no memory in it — ideal flow

3 September 2026

20 essays on what is taught wrongly, fluids at work, flows and fields, compressible flow, transition and turbulence, regimes and numbers, viscosity, circulation and lift and ideal flow

A right total from a wrong picture — what is taught wrongly
The effect that is real, and where it stops — what is taught wrongly
Four Bernoullis and one name — what is taught wrongly
The wing that is flat, and flies — what is taught wrongly
The section that decides the river — fluids at work
A permeability that is only the geometry — fluids at work
The mesh that makes its own mass — flows and fields
The angle a junction chooses — fluids at work
Two averages of one flow — flows and fields
The profile a meter cannot see — fluids at work
The jump does not ask what made it — compressible flow
Slower than either of them — compressible flow
The scalar has its own cascade — transition and turbulence
Three buffer layers, one friction — transition and turbulence
Exact in the total, free in the profile — regimes and numbers
Four profiles, one drag — viscosity
The groups are not the only groups — regimes and numbers
The stress a pipe knows — viscosity
Three numbers out of a camber line — circulation and lift
The inside a flow does not decide — ideal flow

1 September 2026

20 essays on what is taught wrongly, fluids at work, flows and fields, compressible flow, transition and turbulence, viscosity, regimes and numbers, circulation and lift and ideal flow

An hour for every tenfold — what is taught wrongly
A number that is only the shape of the hole — fluids at work
The area that must not move — flows and fields
The drift a closed box will not allow — flows and fields
A compression that costs nothing in the end — compressible flow
Two numbers that do not change — compressible flow
Every unstable wave is inside one circle — transition and turbulence
Sufficient, and not necessary — transition and turbulence
Equal on average, and nothing else — transition and turbulence
The core that does not move — viscosity
The gap that carries the most — viscosity
The three that never converge — regimes and numbers
Exactly similar, and one number short — viscosity
Where a pure number comes from — regimes and numbers
One formula, and it does not ask what the shape is — circulation and lift
How much more than the least — ideal flow
The optimum that does not matter — circulation and lift
The mass a body has to borrow — ideal flow
The speed where the damping is exactly zero — circulation and lift
The lowest pressure is on the body — ideal flow

31 August 2026

20 essays on transition and turbulence, flows and fields, ideal flow and viscosity

A second length at the wall — transition and turbulence
The knot a flow cannot untie — flows and fields
The stretching rate that is not one number — flows and fields
What decay never forgets — transition and turbulence
The range a real Reynolds number does not have — transition and turbulence
The exponents that stop being thirds — transition and turbulence
A flux that runs both ways — transition and turbulence
Where the inverse cascade stops — transition and turbulence
The constant that makes a variance negative — transition and turbulence
A sheet that cannot stay a sheet — ideal flow
The shape a vortex keeps — ideal flow
The flow with no solution — viscosity
The part of the flow inside the body — ideal flow
The singularity a layer makes for itself — viscosity
The swirl that holds a wave still — ideal flow
The constant a hole leaves behind — ideal flow
The drag that is made of waves — ideal flow
What a point vortex is not — ideal flow
The corners that can be done with mirrors — ideal flow
The length the limit invents — ideal flow

30 August 2026

20 essays on regimes and numbers and circulation and lift

A solid, if it is not given time — regimes and numbers
The frequency a wake chooses — regimes and numbers
The number that cannot break a drop — regimes and numbers
Long enough to make a wake — regimes and numbers
The half that carries nothing — circulation and lift
A disc that knows no blades — circulation and lift
The number that is an answer — regimes and numbers
A transition that needs a second number — regimes and numbers
The side that cannot keep up — circulation and lift
A row is not a set of aerofoils — circulation and lift
A speed nobody imposed — regimes and numbers
One group, three exponents — regimes and numbers
The condition that can be bought — circulation and lift
An exponent dimensions cannot give — regimes and numbers
More lift than weight — circulation and lift
One formula for both ends — regimes and numbers
Where the line stops being a line — circulation and lift
The sweep a root does not have — circulation and lift
Two answers to one question — circulation and lift
The control that works backwards — circulation and lift

29 August 2026

20 essays on flows and fields and compressible flow

The picture belongs to whoever is watching — flows and fields
Every flow is two flows — flows and fields
A rate of change that will not hold still — flows and fields
Longer, with nothing pulling it — flows and fields
The other branch of the same curve — compressible flow
When a shock cannot bounce — compressible flow
Where a vortex stops — flows and fields
Incompressible is not a property of the fluid — flows and fields
The spin a shock leaves behind — compressible flow
A shock that lies on the body — compressible flow
The one number that runs out at three dimensions — flows and fields
A wave nothing in it travels with — flows and fields
The equation that changes type inside its own answer — compressible flow
Steady, three-dimensional, and mixing anyway — flows and fields
When gamma stops being a number — compressible flow
The signature that forgets the shape — compressible flow
A radius that gives the energy away — compressible flow
The least drag a volume can have — compressible flow
The discontinuity that has a thickness — compressible flow
Every compression becomes a shock in the end — compressible flow

27 August 2026

15 essays on ideal flow and circulation and lift

The flow with the least energy in it — ideal flow
The mirror that is a circle — ideal flow
Drag in the theory that forbids it — ideal flow
Where the unknown boundary is the known one — ideal flow
The momentum with no value — ideal flow
Inviscid does not mean irrotational — ideal flow
The one rotational solution anybody can write down — ideal flow
The vorticity nothing decides — ideal flow
The exact theory, drawn by viscosity — ideal flow
The body the outer flow actually sees — ideal flow
Three is the most that can be predicted — ideal flow
A finite force from an infinite speed — circulation and lift
Nothing turns a sharp corner — ideal flow
The pressure that depends on the past — ideal flow
The one thing that does not add up — ideal flow

26 August 2026

15 essays on viscosity

The price of a gradient — viscosity
Where the heat of a drag is made — viscosity
The cheapest shape the walls allow — viscosity
A force without the flow that makes it — viscosity
The last of the oil — viscosity
The film that heats itself — viscosity
What a plate takes with it — viscosity
A viscosity that depends on the question — viscosity
A viscosity made of particles — viscosity
The surface that moves with the flow — viscosity
The third thickness — viscosity
The energy a vortex cannot have — viscosity
A swimmer that cannot go backwards — viscosity
The viscosity nobody uses — viscosity
What a fluid takes out of a swing — viscosity

24 August 2026

15 essays on regimes and numbers and transition and turbulence

What "of order one" is worth — regimes and numbers
Where a fluid stops being one — regimes and numbers
Slow enough to be steady — regimes and numbers
How small is small enough — regimes and numbers
The size a drop is allowed — regimes and numbers
The drop that is not a tear — regimes and numbers
Which speed goes in the number — regimes and numbers
The balance that is its own error — regimes and numbers
The tracer that is not one — regimes and numbers
The threshold the walls decide — transition and turbulence
Where the parabola goes — regimes and numbers
Five numbers, one name — transition and turbulence
How far before the heat arrives — regimes and numbers
A limit nothing reaches — regimes and numbers
The number that really is one — regimes and numbers

22 August 2026

15 essays on flows and fields, what is taught wrongly, transition and turbulence, ideal flow, viscosity, compressible flow and circulation and lift

The mean is not the flow — flows and fields
The drift in a wave that has none — flows and fields
A wall that is not quite there — flows and fields
The randomness that is not in the equations — what is taught wrongly
The layer with no length in it — transition and turbulence
What a code says to a wall — transition and turbulence
What the far field remembers — ideal flow
An oscillation with somewhere to go — viscosity
The moment a spectrum cannot hold — transition and turbulence
The sound is what does not cancel — compressible flow
The one exact result — transition and turbulence
The limit that is not the value — transition and turbulence
How far a parcel gets — transition and turbulence
Turbulent some of the time — transition and turbulence
The lift at the mean angle — circulation and lift

21 August 2026

15 essays on flows and fields, regimes and numbers, what is taught wrongly, ideal flow, viscosity, compressible flow and circulation and lift

How many things a flow must be told — flows and fields
The other layer, and the one number that separates them — regimes and numbers
Where vorticity comes from — flows and fields
The cushion that is not there — what is taught wrongly
The wing the equation is really solving — regimes and numbers
Ask for the pressure, and see what shape that is — ideal flow
The air a wing does not carry — what is taught wrongly
Where the reaction to a wing's lift is — ideal flow
A body with no lift, and a moment anyway — ideal flow
The layer that stops at a depth — viscosity
The wall that heats itself — compressible flow
How far before a duct forgets what was fed into it — viscosity
The sound that only leaves — compressible flow
A wake that closes on itself — circulation and lift
The walls are in the answer — circulation and lift

20 August 2026

15 essays on what is taught wrongly and circulation and lift

Not half a venturi — what is taught wrongly
An angle, not a speed — what is taught wrongly
The bee that cannot fly — what is taught wrongly
Where lift starts — circulation and lift
Nothing but the edge — circulation and lift
A slot is not a nozzle — circulation and lift
The wind a swept wing feels — circulation and lift
Which part of a wing stalls first — circulation and lift
The loading nobody used — circulation and lift
A wing that leaves the plane — circulation and lift
Two wings and it does not matter where — circulation and lift
The lift beside a wing — circulation and lift
Where the wake ends up — circulation and lift
The shake that is not resonance — circulation and lift
The surface in the wake — circulation and lift

19 August 2026

15 essays on flows and fields, regimes and numbers, viscosity, ideal flow, circulation and lift, transition and turbulence and compressible flow

No randomness, and it mixes anyway — flows and fields
Where a jet stops being a jet — regimes and numbers
The count a pattern cannot break — flows and fields
Two slow things make a fast one — regimes and numbers
Too fast for a profile — regimes and numbers
Nothing but the shape of the gap — viscosity
Three dimensions are kinder — ideal flow
Lift out of a failure — circulation and lift
The eddies nobody stirs — viscosity
What survives being wound up — ideal flow
The cascade that runs backwards — transition and turbulence
What a jet keeps, and what it collects — viscosity
The number that stops the mixing — transition and turbulence
The wall that cancels its own waves — compressible flow
What viscosity cannot take away — viscosity

18 August 2026

15 essays on what is taught wrongly and fluids at work

The effect that explains nothing — what is taught wrongly
The bath does not know the hemisphere — what is taught wrongly
The siphon that does not need the air — what is taught wrongly
The hole that halves the flow — fluids at work
What a jet cannot push sideways — fluids at work
Half the jet speed takes everything — fluids at work
The price of knowing the flow rate — fluids at work
The instrument in the answer — fluids at work
Stopping water costs more than moving it — fluids at work
A pump with no engine — fluids at work
Mixing is a pump — fluids at work
One number picks the machine — fluids at work
A velocity nobody has — fluids at work
Where Darcy stops — fluids at work
The bed that weighs itself — fluids at work

16 August 2026

15 essays on what is taught wrongly, regimes and numbers, flows and fields, viscosity, ideal flow, circulation and lift, transition and turbulence and compressible flow

The theory that forbade flight — what is taught wrongly
Nothing sucks — what is taught wrongly
Counting what matters — regimes and numbers
What a parcel does in the first instant — flows and fields
The spin that feeds itself — flows and fields
Whether the droplet turns — regimes and numbers
The wall that shakes — viscosity
Vortices move each other — ideal flow
A ring moves because it is bent — circulation and lift
Pressure has no speed — ideal flow
The layer that stops growing — viscosity
The lift that arrives late — circulation and lift
Every mode decays and it grows anyway — transition and turbulence
One diaphragm, every wave — compressible flow
Two ways to choke — compressible flow

15 August 2026

15 essays on fluids at work

The most a disc can take — fluids at work
A big slow push — fluids at work
The wake that has to spin — fluids at work
The roughness a wall cannot feel — fluids at work
A loss with no viscosity in it — fluids at work
The shock in a river — fluids at work
The depth that costs least — fluids at work
The drag that falls as it speeds up — fluids at work
A ball that swings without spinning — fluids at work
Faster than the wind that drives it — fluids at work
The fastest way is not the straight one — fluids at work
The radius that costs least — fluids at work
When a body tears the water — fluids at work
The bubble that hammers — fluids at work
Work out of a change of swirl — fluids at work

13 August 2026

15 essays on transition and turbulence and viscosity

The solutions stop being chosen — transition and turbulence
The number that is not a number — transition and turbulence
A layer with a kink in it — transition and turbulence
Every wavelength at once — transition and turbulence
What averaging costs — transition and turbulence
The ladder that never closes — transition and turbulence
A guess with a constant in it — transition and turbulence
Where the energy goes — transition and turbulence
The gradient that does both — viscosity
The grid nobody can build — transition and turbulence
A threshold with a closed form — transition and turbulence
The cost of going turbulent — viscosity
Three numbers left of a fluid — transition and turbulence
A millionth is enough — transition and turbulence
The street a steady calculation cannot draw — transition and turbulence

11 August 2026

15 essays on compressible flow, what is taught wrongly and regimes and numbers

What a signal travels at — compressible flow
When the warning cannot arrive — compressible flow
Energy instead of pressure — compressible flow
The duct that works backwards — compressible flow
The throat that stops listening — compressible flow
What the airspeed indicator believes — what is taught wrongly
One area, two answers — compressible flow
The jump the equations allow — compressible flow
The pocket on top of the wing — regimes and numbers
The only law that forbids it — compressible flow
What a shock costs — compressible flow
A shock that leans — compressible flow
When the wedge is too blunt — compressible flow
Turning the other way is free — compressible flow
Drag with nothing to rub — compressible flow

4–10 August 2026

46 essays on what is taught wrongly, regimes and numbers, flows and fields, ideal flow, viscosity and circulation and lift

The story about air meeting up again — what is taught wrongly
One number decides which physics applies — regimes and numbers
Streamlines are not the paths particles take — flows and fields
The theory that solves everything — ideal flow
Everything happens in a layer you cannot see — viscosity
What actually holds a wing up — circulation and lift
Mass has nowhere to go — flows and fields
The exact theory says nothing has any drag — ideal flow
The sharp edge decides — circulation and lift
The Reynolds number, and the length in it — regimes and numbers
When the flow lets go — viscosity
Where Bernoulli's equation applies — what is taught wrongly
Air must be pushed down, and the usual sum is wrong — what is taught wrongly
Flows add up — ideal flow
The two theories, side by side — viscosity
The lift curve, and why it is a straight line — circulation and lift
What a flow is — flows and fields
When air stops being incompressible — regimes and numbers
Steady does not mean nothing is happening — flows and fields
How thick is thin — viscosity
Lift with no wing at all — circulation and lift
Fast means low pressure — ideal flow
The angle that does not care — regimes and numbers
What a photograph of a flow shows — what is taught wrongly
One function instead of two — ideal flow
Spin is not the same as going round — flows and fields
The model that cannot be matched — regimes and numbers
The two drags a wing pays — viscosity
The vortex a wing leaves behind — circulation and lift
Bodies made out of nothing — ideal flow
How much uphill a layer can take — viscosity
The number on a streamline is a flow rate — flows and fields
The world with no inertia — regimes and numbers
Where the lift acts — circulation and lift
A wall made by reflection — ideal flow
Circulation is vorticity, added up — flows and fields
The price of having ends — circulation and lift
Where the straight line stops — viscosity
From a circle to a wing — ideal flow
How much circulation is too much — circulation and lift
The cheapest way to stay up — viscosity
The number that does not depend on the tunnel — ideal flow
The wall that pushes back — circulation and lift
The force of getting going — ideal flow
What a flap does, and what it does not — circulation and lift
The span is the whole story — circulation and lift

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