Amateur Aerodynamics

Last time, we went through a brief overview of cooling systems: what parts constitute the "cooling package," some of the issues in cooling system design, and a breakdown of the cooling airflow into stations for analysis.   Now, let’s move on to that analysis. We’ll follow the path of air from some upstream location as it enters and passes through the cooling system. The first obstacle it will encounter is the inlet, and on most cars today that inlet comes with an obstruction: the grill. Even in the central "open" portion of this Kia Telluride grill, inlet flow will encounter significant obstructions due to the styling elements. These dissipate energy and reduce total pressure. Grill/Inlet: State a to State 1   If your car has a grill, there will be a loss in total pressure between a and 1 due to friction and separation around the slats. This can be significant—on the order of 10-20% (normalized to freestream velocity), according to Aerodynamics of Road Vehicles —a...

Modern car shapes are approaching the limits of low drag, were it not for details such as wheels, drivelines, suspensions, brakes, and cooling. This is good news for home modifiers. If your starting point is a car with a good basic shape, such as a Prius (as opposed to a car with a horrible basic shape, like my pickup), things like wheel drag and cooling system drag are likely responsible for a larger fraction of overall aerodynamic drag. These areas, then, are good targets for drag reduction. In the next few posts, I’ll address the cooling system.   Cooling airflow is responsible for a significant drag fraction on modern cars. Yes, even on EVs! EVs require more cooling than a lot of people think; they are very much not  "no cooling air necessary," as some online aerodynamics aficionados seem to think (and we’ll see later on why it might be beneficial to use a large heat exchanger even on an EV). This ZR1 cutaway shows two of its many heat exchangers; unlike most cars, the c...