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Calculate the Drag Coefficient


The drag coefficient cd is is a dimensionless measure for drag (fluid or air resistance). Density here is the density of the medium in which an object moves. 1.2 kg/m³ is an approximate value for air, water has 1000 kg/m³. Reference area is the projected frontal area of the object. Drag coefficient cd, also called flow resistance coefficient, is an important parameter for cars, for example, and has a particular impact on the consumption of energy in the form of electricity or fuel, with a lower value reducing consumption.

drag force = density * cd * reference area * velocity² / 2
Fd = ρ * cd * A * v² / 2

drag force: Newton
density: kg/m³
cd:
reference area:
velocity:

Please enter four values, the fifth will be calculated. The usual physical value for speed is meters per second (m/s), but it can also be calculated in kilometers per hour (km/h) or miles per hour (mph).

Example: a car has a drag coefficient of 0.267 and a frontal area, as the reference area of ​​cars is also called, of 2.36 square meters. These are the values ​​of the Volkswagen ID.3. At a speed of 50 kilometers per hour, it experiences a drag force of just under 74 Newtons. At 100 kilometers per hour, it is already 295 Newtons and at 150 km/h, it is almost 664 Newtons. This disproportionate increase is due to the fact that the speed is included in the calculation as a square. This is why consumption increases sharply at high speeds. And therefore a good, i.e. low drag coefficient is particularly important for vehicles that are intended to reach high speeds.

A good drag coefficient is achieved by a shape that allows the wind to flow around the object in question as well as possible without creating turbulence. This is achieved primarily by having surfaces that are as slanted as possible in the direction of the wind or the direction of travel.




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