Dimensional Analysis

• Drag force (FD) depends on the pressure/shear stress distributions and should scale to the flow kinetic energy: (1/2)rU2 and the surface area of the model: D2.

• The drag coefficient is a dimensionless variable, therefore, the new function g must be consisting of dimensionless variables only. Otherwise, a choice of different unit systems will provide different results for the same system.

• It can be shown, by using the Buckingham Pi theorem, that the new function consists of one dimensionless variable only, that is, the Reynolds number, Re.

See golf ball aerodynamics

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