Winglets and bumpy paint?

[kitcar]

Sorry, I should have been more clear. The relatively slow landing and takeoff speeds of the MiG-29 at 161 to 170 miles per hour, the ingestion of the particles into the engine inlet and the root cause being the bumpy paint causing vortexes around the engine inlets show the stuff worked at near automotive speeds but is the effect detrimental to the energy needed to propel the vehicle?

We can't use the golf ball analogy here because it isn't correct.

A perfectly smooth ball suffers from a flow separation around its surface, a large wake and this causes large pressure drags. A smooth ball has low skin friction, but really really high pressure drag, because even though the flow is straight, it separates from the ball very early in flight during its acceleration. If you put dimples on the ball to roughen the surface, the pressure turns turbulent and the resulting higher energy flow stays "attached" to the ball longer, making a smaller wake and reducing the pressure drag. What you have done is traded friction drag for a drop in pressure drag which allows the ball to go further through the air. Spheres are very special cases in aerodynamics and simply can't be applied to vehicles.

What I'm actually refining the theory into is a way to reduce the wake of the vehicle by the use of irregular surface areas by using a turbulent boundary layer. I.E., reducing the pressure drag (wake) of the vehicle.

I guess I could have been more technical in explaining the concept for turbulent boundary layers but this stuff can glaze eyes over and make grown men weep in confusion:

We know that the air stream follows the curves (shape) of the vehicle as it passes through the air. Conventional wisdom says that the smoother the surface the better the vehicle slips through the air (closing of gaps, removal of wipers, etc.). In the same vein, an introduction of a surface with less surface area would produce less wind resistance. It should be a matter of degrees. If a Mach 2 aircraft needs tiny bumps to achieve this (which it turns out worked at 161 to 170 mph), then vehicle with a lower terminal velocity (say 60 mph to keep the formulas as simple as possible) would need larger bumps. However, that is the problem with fluid stream dynamics; logic doesn't always apply. Over the years, I've thought about the concept a lot since the interview and on the surface it makes all the sense in the world. What you're attempting to do is make the surface that pushes through the air irregular in that the surface area varies with the use of protrusions into the fluid (air) stream which in turn causes the air that you travel through to "think" that your vehicle is smaller than it really is. Taken to the n th degree, that is what we do with air dams, side skirts and such. We're taking away surfaces that the air would normally be traveling over and thus making the air "think" that the vehicle has a smaller aspect area or cd than it really does. Boiled down, let's reduce the pressure on the vehicle by introducing a lower pressure boundary layer of air in certain areas of the vehicle.

Now I wish we had a way to put formulas into our posts. That would be handy at this point. However:

This is called the boundary layer and what we are looking at is called turbulent boundary layer effect, which is expressed as the RANS (Reynolds averaged) formula. This is assuming that the density of the air is constant (which we know it isn't but we can simplify the entire deal a lot by assuming it is). What we are looking at is a combination of force, viscous stress, isotropic stress and apparent stress due to a fluctuating velocity field (which is what the irregular surface - or bumps - is) and for that we can use the Reynolds stresses formula; (Re)= ((fluid velocity*distance from leading edge)/kinematic viscosity).

How's that for a convoluted explanation to my silly little idea?

Maybe I'll just stick with canards on the wheel wells.