# Flow past a sphere

1. Aug 11, 2009

### germana2006

1. The problem statement, all variables and given/known data
Considering a unsteady, incompressible flow past a sphere placed in a channel. The sphere is offset somewhat from the center of the flow to destabilize what otherwise would be steady-state symmetrical flow. Calculate the tangencial rotational force at the sphere.

2. Relevant equations

3. The attempt at a solution
My attempt is to make use of the Stoke's friction law for rotational motion of a sphere:
$$F=-8 \pi \eta_0 a^3 \Omega$$
with $$\eta_0$$ the viscosity, $$a$$ sphere radius, $$\Omega$$ sphere velocity.
But this is the total force and I have to calculate only the tangencial.

2. Aug 17, 2009

### germana2006

The friction force is a tangential force, then if I have to calculate the tangential rotational force, then I have only to calculate the friction force written above?