Quote:
Originally Posted by Daox
Very good points Otto, and just what I had planned. Just yesterday I was wondering how many pieces I'll need for the tuft testing and thinking about what colors to use on the body and windshield for maximum viewability.  But, I hadn't thought about the reintroduction of airflow. I was kind of thinking that with the bellypan the only exit for air will be the wheel wells. This is what Basjoos is currently doing. |
Tuft testing on a motorcycle is easy since you can sit there and see the yarn. On a car, you'd presumably need a photographer in another vehicle at highway speed. At the nose, only a dozen or so tufts required.
Lots of cars (including my Porsche 944 Turbo) unnecessarily bugger the airflow around the nose by marginal installation of fog lights, too many inlets in the grill, etc.. At some point, I may start from scratch with a new nose cone, with one elliptical inlet, etc..
NACA tech papers can be found online, but I don't have a link. Radiused outlet geometry is key to gathering and venting the used cooling air back into the slipstream with minimal drag. The air molecules communicate with each other all along the stream. That sounds nuts, and may be, but it's true. So, downstream molecules influence upstream ones, which then wander off the path. Cooling needs to be holistic, i.e., input, throughput, and output all smoothly mated and compatible. Efficient outlet design may be more critical than inlet, since a good outlet will draw air into and through the cooling system, whereas a good inlet can get the cooling air
to the radiator, but then the air may be jammed for lack of proper outlet, so stop flowing well. This is certainly the case with my Porsche intercooler, which has a superb inlet diffuser duct to the heat exchanger, but then leaves the spent air trying to find its way back to the slipstream
somehow. I may install a cowl flap.
Heat rises, so vents along the sides of the hood about half way back may be pretty efficient, inducing Venturi suction of hot air from the engine compartment.
FWIW, in the P-51, the belly cooler was pretty efficient, and actually gave the plane a bit of thrust as heated air rejoined the slipstream.