Slipstreaming is a technique used, especially by cyclists, to take advantage of the airflow around fast-moving objects in an effort to reduce drag. As a high-speed vehicle travels forwards it encounters air resistance, or drag, which works against the direction of travel.
Cyclists racing in a velodrome travel as fast as possible, but the faster the bike goes the greater the drag. To combat this, two or more cyclists can slipstream, or draft. It all comes down to aerodynamics of an object through a fluid (note: gases, like air, are referred to as fluids).
The lead cyclist in a race pushes through the air ahead of them, which diverts the air stream around the sides of the bike. This disturbance in the airflow creates turbulence and a pocket of reduced or negative air pressure in the wake of the bicycle. This area of lower pressure (a partial vacuum) is the slipstream and a cyclist pedalling in this region requires less effort as they encounter less drag, and in some cases they will even experience forward suction.
The symmetrical 250-metre (820-foot)-long velodrome track consists of two straights with two 180-degree turns at either end. While the straights slope inwards slightly, the summit of the two turns are banked steeply with the slope reaching up to 42 degrees at its highest on the outside edge.
The inclined sides enable cyclists to stay on these death-defying circular tracks with the help of centripetal force. This force, created by gravity, pulls the riders inwards and stops them shooting off in a straight line. The arena’s distinctive shape, like a Pringle crisp, also helps the riders stay upright – ie perpendicular to the track.