Copyright © A. Filippone (1999-2003). All Rights Reserved.

Characteristic Numbers

Below is a list of the most important dimensionless parameters used in aerodynamics. A list of all known parameters in the applied sciences (about 280 of them !) is available in Ref. 1.

1. Reynolds number

Reynolds number

Field of Use: Dynamic similarity

2. Mach Number

Mach number

Field of Use: Compressible flows

3. Prandtl number

Prandtl number

Field of Use: Convective heat transfer

4. Knudsen number

Knudsen number

Field of Use: Hypersonic flows.

5. Strouhal number

Strouhal number

Field of Use: Unsteady flows.

6. Froude number

Froude number

Field of Use: Wave and surface flows

6. Reduced Frequency number

Reduced Frequency

Field of Use: Dynamic Stall and other oscillatory flows.

7. Eckert number

Eckert number

Field of Use: High-speed flows with heat exchange.

a =Speed of Sound
g =Acceleration of gravity
u =Speed
L =Length Scale
k =Coeff. of Thermal Conductivity
V =Velocity
= Molecular mean path
= frequency

Selected References

  • Parker SP. (editor). Fluid Mechanics Source Book, McGraw-Hill, 1987 (ISBN 0-07-045502-3).

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Copyright © A. Filippone (1999-2003). All Rights Reserved.