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2d flow.

submitted by usedoilanalysis to Fluiddynamics 2.5 yearsOct 15, 2022 08:54:06 ago (+11/-0)     (Fluiddynamics)

Doesn't exist, it's trying to simplify and approximate the truth. Flow is 5 dimensional, we assume 2 orthogonal axis of spin, and we call the other stuff secondary flow. Flow is locally structured in 3 dimensions, and translated in another 2. Locally structured in x, y, and z planes, and the other 2 dimensions are borrowed from electromagnetism, divergence and curl. Divergence is basically pressure gradient, and curl is basically vorticity.

Aerodynamicists create formulas and approximations to encapsulate all 5 dimensions of airflow. Prandtl's lifting line theory, Martin Kutta's theories regarding circulation, and the subsequent Kutta-Jukowski theorem. Which is really just a description of flow around a cylinder, with an applied Fourier transformation. As we all know Fourier transformations are 2-d projections of more complex phenomena.

The problem is we are pea-brained, it's difficult for us to see the nested donuts in airflow, and the 5 dimensions they encompass. It's bad enough we can't see the wind, but worse our tools for analyzing it are dependent on butchered approximations.

A while ago I saw a new propeller design, and then it hit me like a ton of bricks.

https://www.youtube.com/watch?v=MNnB_50Z20I

This thing is just ribbons of a torus.

https://i.ytimg.com/vi/px5kZn_hPbU/maxresdefault.jpg

The vortex ring is a torus, a non-destructive interference pattern. The vortex ring encapsulates all 5 dimensions of flow. X,Y,Z planes of symmetry, divergence and curl, all in one.


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[ - ] deleted 2 points 2.5 yearsOct 15, 2022 09:48:35 ago (+2/-0)

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[ - ] usedoilanalysis [op] 1 point 2.5 yearsOct 15, 2022 10:28:56 ago (+1/-0)

There's no 2d flow, because there's a boundary layer in the walls of the hose which causes the flow to locally slow down, while the flow at the center has less friction/obstruction and moves faster, this adds vorticity.

[ - ] deleted 1 point 2.5 yearsOct 15, 2022 11:12:48 ago (+1/-0)

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[ - ] usedoilanalysis [op] 0 points 2.5 yearsOct 15, 2022 11:19:26 ago (+0/-0)

If the water flow is fast enough, the pressure difference between the wall and the center is such that cavitation occurs. There will be pockets of water where the pressure drops enough to change the phase of water into vapor.

[ - ] deleted 0 points 2.5 yearsOct 15, 2022 11:26:34 ago (+0/-0)

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[ - ] deleted 0 points 2.5 yearsOct 15, 2022 11:27:50 ago (+0/-0)

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[ - ] usedoilanalysis [op] 0 points 2.5 yearsOct 15, 2022 11:28:55 ago (+0/-0)

I work in fluid mechanics, mostly in validation of compressors

[ - ] deleted 0 points 2.5 yearsOct 15, 2022 11:33:43 ago (+0/-0)

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[ - ] usedoilanalysis [op] 0 points 2.5 yearsOct 15, 2022 13:28:34 ago (+0/-0)

Roots or twin screw. Roots is the simpler design but has lower efficiency. Roots blower is the log manifold of the compressor world. The twin screw is much more efficient because the two screws are vortex shaped. Funny enough the housing cross section on blowers is toroidal.

[ - ] deleted 0 points 2.5 yearsOct 16, 2022 01:51:01 ago (+0/-0)

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[ - ] usedoilanalysis [op] 0 points 2.5 yearsOct 16, 2022 08:12:39 ago (+0/-0)

You mean centrifugal or axial compressors? The casing is almost air tight, from there, it's just a matter of making sure your intake pipes don't leak too badly. Every elbow, every coupler, every inch of tubing adds its own issues. A lot of time boost piping hits a resonant frequency and stuff starts either coming off, or outright breaking. That's why you use aluminum at the bends over carbon fiber, even if you have the money. You hit the resonant frequency on a bend of a carbon pipe and that baby will shatter. Aluminum is more ductile, so even though there is a slight weight penalty you have more reliability and less cost.
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[ - ] Rebooted 1 point 2.5 yearsOct 15, 2022 10:50:39 ago (+1/-0)

The torus observation is interesting.

[ - ] usedoilanalysis [op] 0 points 2.5 yearsOct 15, 2022 10:54:10 ago (+0/-0)

I feel that we're just scratching the surface. I wouldn't be surprised if bird wings can be extrapolated from the surface of a torus.

[ - ] Teefinyomouf 0 points 2.5 yearsOct 15, 2022 10:33:06 ago (+1/-1)

None of it exists. All are merely mathematical formulations. All are trying to "simplify and approximate the truth". 2D flow is an accurate formulation in certain conditions. This post is mumbo jumbo, like African Airplane and Flat Earth had a baby.

[ - ] usedoilanalysis [op] 2 points 2.5 yearsOct 15, 2022 10:58:25 ago (+2/-0)*

It takes less effort to dismiss something than to engage it. It's a common strategy of the slow, or dull witted. Explain why turbomachinery housings use toroidal housings if the torus shape is just mumbo jumbo? The flow around a torque converter is toroidal as is the housing, why isn't it square or some other shape?