Random Wind Tunnel and Smoke Pictures Thread

[Piotrsko]

Since I'm not familiar with the AST-III contour, I have to ask if it has that ugly drag depression behind the drivers section like the supra picture shows?

[aerohead]

Originally Posted by Piotrsko

Since I'm not familiar with the AST-III contour, I have to ask if it has that ugly drag depression behind the drivers section like the supra picture shows?

You'll have to help me out with this expression. I'm uncertain as to the meaning of 'drag depression.'

[freebeard]

Since I'm not familiar with the AST-III contour, I have to ask if it has that ugly drag depression behind the drivers section like the supra picture shows?

TLDR; it's a half-body of revolution.

There's that new hypercar that I can never remember* that has a spoon-shaped depression where the Supra has a convex window. It obtains downforce without a wing.

*[citation needed]

[Piotrsko]

Originally Posted by freebeard

TLDR; it's a half-body of revolution.

There's that new hypercar that I can never remember* that has a spoon-shaped depression where the Supra has a convex window. It obtains downforce without a wing.

*[citation needed]

The supra has a mini wing also so the downforce must be high. Does not downforce increase drag? I just do not know of any low drag airfoils that have a convex shape aft of the high point. Apparently, my knowledge is lacking. Even google returns liver anomalies for an AST search string.

[freebeard]

In theory, either lift or downforce will increase drag, but you know what they say about theory and practice.

This isn't the example I was thinking of, but similar. Downforce with no wing, possibly increased underbody drag[?]

www.roadandtrack.com: Aston Martin and Red Bull's Hypercar Generates 4000 Pounds of Downforce with No Wing

[Piotrsko]

Lambo countach (spelling)? Looks like that aston, must be an areo trend.

[aerohead]

Originally Posted by Piotrsko

The supra has a mini wing also so the downforce must be high. Does not downforce increase drag? I just do not know of any low drag airfoils that have a convex shape aft of the high point. Apparently, my knowledge is lacking. Even google returns liver anomalies for an AST search string.

1) If a spoiler re-attaches flow, then it has reduced drag/lift due to separation.
2) If a spoiler is positioned in a region of attached flow, then it is a 'direct-downforce' device, and will introduce induced drag.
3) Wing sections, aft of maximum thickness have convex surfaces of proportionally- increasing radii as they approach the trailing edge.
4) Some profiles 'null' as a 'convex' surface, then 'reflex' as a 'von Mises' profile.
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5) The AST is the aerodynamic streamlining template, intended as a 1st- Principles / 1st- Approximation tool for attached-flow aft-body elongations.
It requires a 'blueprint' / true-length, technical drawing for each specific vehicle. It's here on page-1 of the AERO Forum. It is derived from a three-dimensional, streamline half-body of revolution, completing a streamline body of revolution mirror-image, produced through reflection from the roadway.

[freebeard]

Originally Posted by Piotrsko

Lambo countach (spelling)? Looks like that aston, must be an areo trend.

Lamborghini Countach
lamborghini.com/en-en/brand/masterpieces/countach
The Lamborghini Countach is a rear mid-engine, rear-wheel-drive sports car produced by the Italian automobile manufacturer Lamborghini from 1974 until 1990. It is one of the many exotic designs developed by Italian design house Bertone, which pioneered and popularized the sharply angled "Italian Wedge" shape.Wikipedia

The Countach is a brick, compared. The underbody is completely undeveloped. Look at the AM-RB 001's front wheelwells.

[kach22i]

Ron Will’s Turbo Phantom
Ron Will’s Turbo Phantom – Dean’s Garage

I had also been working at the GM Tech Center’s Harrison Wind Tunnel on Chevy designs to lower their drag coefficients. So my next step was to do the same with my three wheel design. It was shaped like a wing, so I was a little afraid that it might try to fly at higher speeds. Also, I needed to find a place to locate a radiator. The first Honda Gold Wing water cooled 4-cylinder touring bike had just been introduced, so that was my engine of choice. I built a much larger 3/8 scale model this time. The guys running the tunnel were excited to run something different and ran it after hours. They even modified the tunnel base to accept a three wheel design. The results were all positive. It didn’t lift, the radiator would cool in the back of the fender, and our Cd was .31—not great, but not bad either.

[freebeard]

I've predicted that Blender will become a platform to perform CFD on consumer-grade hardware.

That's based on their support for OpenVDB and the aggressive development cycle. OpenVDB has been included since about 2.8, and now with 3.0 (currently 3.2 is in Beta) there're Geometry Nodes.

TLDR; a node based editor for meshes and curves. It's above my pay grade, but I can appreciate the progress. Here is a tutorial that gives the flavor of working in Geometry Nodes, putting streamlines around a car body.

Blender 3.1 Geometry Nodes Lightbeams [Raycast Node is amazing!]

The shortfall is the lines are all horizontal instead of regressively seeking the lower pressure's direction. With that, it would show the bounded layer. OpenVDB would enable modelling the adjacent voxels/streamlines.