Front inner fender drag reduction idea?

[woodstock74]

So I came across this concept today, one I had never seen before:


Found it in this document:

http://www.diva-portal.se/smash/get/...FULLTEXT01.pdf

Which compares full scale vs model (1/5th scale) in same wind tunnel. Results from above front inner fender concept are:

-.003 to -.006 drag reduction. (-.003 what the full scale model showed, -.006 what the 1/5 scale model showed)

Has anyone ever done/considered this?

[Vman455]

What happens when the wheels turn?

[19bonestock88]

I imagine that you’d momentarily lose the benefit of the ribs as you steer the car... what I’m curious about, however, is whether or not it’s important that the wheel gap be that tight... it looks almost as if the ribs are touching the tire... it wouldn’t be terribly hard to implement something like it on some of our old beaters though... (though for only .003 reduction in drag I’m not sure if it would be worth the effort)

[Ecky]

Originally Posted by Vman455

What happens when the wheels turn?

I'm imagining the ribs are roughly triangular, and when you turn the wheels, the clear the tabs on the edges. The one in the middle might have to go.

[19bonestock88]

Originally Posted by Ecky

I'm imagining the ribs are roughly triangular, and when you turn the wheels, the clear the tabs on the edges. The one in the middle might have to go.

In the article in the link, the manufacturer specifies a rectangular cross section... is a good point though, with a very wide tire it wouldn’t work without rubbing... now the rear wheel wells would be good for such a device but we usually skirt those here on EM...

[woodstock74]

Ruberized conveyor belt material pulled taunt. That's what I'm using for my side skirts underneath my car. Poke the belt thought a couple of places in the inner fender and make a metallic braket to attach on the back side. Job done. Tire rubs up against the converyor belt, no worries. Hardest part of this is figuring out how to get the inner fender out to work on it.

[freebeard]

Lower right corner — Vortex traps. Just applied to the fender well.

[Otto]

Originally Posted by freebeard

Lower right corner — Vortex traps. Just applied to the fender well.

Seems to me, such vortex traps could be easily and inexpensively made with Coroplast, cut with a compass device to match the round curvature of the tire, then mounted to the inner fender liner.

This application appears to have some conceptual semblance to a ducted fan, where the duct necessarily has a very small gap between the spinning propeller blade tips, to prevent spillage of air from the positive pressure behind the blade, i.e., to act as a flow fence to prevent vortices and associated loss of efficiency. In other words, the spinning tire acts as a crude turbine, and the vortex trap flow fences act to contain the vortices, rather than have them escape outboard only to bugger the airflow past the wheel well opening.

I wonder how such vortex traps would compare with air curtains' efficiency?

[kach22i]

Those wheel well ribs as pointed out would probably be made of a flexible material like conveyor belt material.

Somewhere a study would have to be done on cost/maintenance/friction in turns/and perhaps retractability and operable vanes/fins. Possible tire rubber wear would also be a possible liability.

Overall I like the concept and see it as a sort of rear diffuser for wheel wells.

Aside topic from paper regarding:
SECTION 5.2.1
Wake Pumping Mode...........................

Absolutely fascinating as I think anyone that has rode a motorcycle has felt their open jacket whipping about, or driven in a car with windows rolled down and suffered cabin buffeting has experienced.

I wonder if Wake Pumping Mode is what causes some hovercraft to "Porpoise", that is to say suffer from bow to stern up and down bobbing or "heave" (longitudinal instability) not caused by surface wave action but caused by aerodynamic forces.

[oil pan 4]

What if you have a regular small car and the wheels are relatively tiny compared to the wheel wells?