Quote:
Originally Posted by aerohead
1) Free flow, outside the boundary layer IS considered inviscid flow.
I stated that we're looking at 2-D flow. Which is basically what your looking at when you do your centerline pressure profiles.
2) And of course, we don't live in a d' Alembert's Paradox world of non-viscosity.
3) The value of the schematic, was the example of a body experiencing positive pressure downstream of 'lift', which is germane to streamlined bodies.
4) You like wings, Hucho goes on elsewhere to show the same thing for a RAF 101 symmetrical airfoil, at 4-degrees angle-of-attack, and zero lift. This is a real foil in a real laboratory, and real air, at supercritical Reynolds number.
5) And as I shared with you many months ago, Abbott and Von Doenhoff's book demonstrates zero-lift conditions for every extant airfoil known at the time of their publication. Your aeronautical engineer friend will have that. My aeronautical engineer friend Larry Mauro does.
' The drag and lift of a body depend strongly upon the angle of attack.' Hucho, page 202, Re: Stollery & Burns Ref. 4.83.
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Normal mix of Aerohead irrelevancies and the justifiable of the unjustifiable.
Fact 1: Aerohead cited the diagram and said of it:
The Cadillac poses only a small perturbation. It's virtual lack of rear lift is a testament to the pressure-producing capability of a streamlined shape.
If you'll revisit Figure 2.4, page 51 of Hucho, you can see how,over the last 14.5% of the body, local pressure rises all the way back to local barometric pressure. Depending on rear overhang, and low pressure under the body, due to a diffuser, rear lift can be zero, like the VSPORT's
Fact 2: The diagram is for an imaginary, viscous-free (inviscid) fluid. The accompanying body text says of the diagram:
On the rear part of the vehicle's upper surface a steep pressure rise occurs, and it is in this region where considerable differences exist between the real flow of a viscous fluid and the inviscid flow shown here.
Fact 3: Aerohead's description of what the diagram shows is completely contradicted by the text, which makes the clear point that the diagram does not apply to real cars, especially in terms of pressures on the rear half (exactly the area Aerohead references).