Why Don't Cars Have Long Tails?
The drag force cars create as they move through air is generated largely by a pressure imbalance. Cars are bluff bodies as opposed to streamlined; that is, airflow separates over them and, in modern cars, this separation usually occurs most prominently at the very back and creates a large wake (even fully streamlined shapes like wings have wakes, too, but they tend to be a lot smaller). This large wake results in negative gauge pressure acting on whatever body surface is exposed to it which, since it’s the back of the car, tends to be a large vertical surface (we call this the base )—so the low pressure ( base pressure ) results in a force acting almost directly backward. One way to reduce the drag of cars is to make this wake area and its resulting pressure drag smaller by tapering the rear part of the car in a long tail; this allows the flow to recover pressure so long as it does not detach prematurely and reduces the vertical surface area exposed to low gauge pressure. Alt...