{Automotive Aerodynamics #13} - Wheelhouse Aerodynamics

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Wheelhouses have quite complex aerodynamics. In this video we go through the general aerodynamics of a wheelhouse as well as how to reduce its drag through flow control devices.
Automotive Aerodynamics textbook by Joseph Katz: amzn.to/3noTCXK (Affiliate link)
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#CFD #Aerodynamics #Drag #AutomotiveAerodynamics #Wheelhouse #WheelhouseAerodynamics

[@mikedonlon3351]

Thank you for the informative video. Regarding the deflectors: I have seen them installed as you sketched them; relatively short and perpendicular to the air flow. I would guess that the air would be deflected to both sides; both outboard and inboard. Would there be a benefit to angling these deflectors to guide the air outboard or is the idea that the inboard / center air flow pressure (what is going down the center-line of the car) is enough to ensure the bulk of the air is deflected outward even with perpendicular deflectors?

[@PremierAerodynamics]

There are a couple of things to consider. The first is that deflecting a lot of air out to the side results in a greater wake developing down the side of the car. That will increase the drag.
The second thing is that often, the flow under the car is migrating towards the outside a little as well. So, a perpendicular angle won't necessarily result in a 50-50 split of air inboard to outboard.
Surprisingly, perpendicular is often the best angle for drag reduction (at least that is tested).

[@iggyppup]

Thanks 4 this. Felt tiped pen, biger drawings would b better, easier to c!

[@PremierAerodynamics]

Thanks!

[@tturi2]

so a front mudflap? and salad bowl caketin?

[@PremierAerodynamics]

Redirecting the flow around the wheel is definitely important and you have to do it in a way that doesn't increase the drag because of the object you put there.

[@terencepoon1915]

can rear mud flaps do the job for housing the rear end of rear tire in order to lower the drag?

[@PremierAerodynamics]

Good question.
Overall, no.
One major reason is that it is more the front of the wheel that should be covered. Also, for the rear wheels, the diffuser follows. So, putting this vertical sheet behind the wheels without blending it into the underbody means that the part of the diffuser directly following won't have any real flow going over it.
So, in order for the diffuser to work, it then needs to get flow from elsewhere.
That, overall, increases the drag.
If you blend the mud flap into the rest of the underbody, then you can get that drag reduction from the diffuser, as well as potentially from the rear wheel.

[@米空軍パイロット]

My Subaru has what they call a "splash guard", behind the wheels, and they claim it reduces drag. These splash guards are narrower than the wheel and taper in both dimensions as you get further from the car body. But they are quite small. Too small to be a real mud flap.

[@PremierAerodynamics]

​@@米空軍パイロット They definitely do serve the purpose of reducing the drag because you now have geometry taking up the space that a wake would usually exist in.
The wake from the wheel still exists, but now it is squashed in with the rest of the flow, which helps reduce its effects.

[@米空軍パイロット]

@@PremierAerodynamics Yes. And it is quite useful for my vehicle in particular because of how much ground clearance it has.