Stokes number

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The Stokes number, named after Irish mathematician George Gabriel Stokes, is a dimensionless number corresponding to the behavior of particles suspended in a fluid flow. Stokes number is defined as the ratio of the stopping distance of a particle to a characteristic dimension of the obstacle, or

Stk = \frac{\tau\,U_o}{d_c}

where τ is the relaxation time of the particle, Uo is the fluid velocity of the flow well away from the obstacle and dc is the characteristic dimension of the obstacle. For Stk\gg 1, particles will continue in a straight line as the fluid turns around the obstacle therefore impacting on the obstacle. For Stk\ll1, particles will follow the fluid streamlines closely.

[edit] References

  • Fuks, N. A. (1989). The mechanics of aerosols. New York: Dover Publications. ISBN 0-486-66055-9. 
  • Hinds, William C. (1999). Aerosol technology: properties, behavior, and measurement of airborne particles. New York: Wiley. ISBN 0-471-19410-7. 

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