Fall velocity for a small Reynolds number

When the Reynolds number is small, the dominant term in [3.9] is the viscous term. The Euler number has the order of the reciprocal of the Reynolds nmnber, ( 1 / Re). The dynamics of the flow is governed by equilibrium between 

The equihbrium between the forces exerted on the ball (equation [3.13]) leads to the dimensional form of Stokes law  

An exact calculation of the flow past the ball shows that the value of the constant is = 1/18. 

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