# Velocity potential for wind over a semi cylinder

1. Apr 28, 2010

### MaxManus

1. The problem statement, all variables and given/known data
A wind flows along the horizontal ground with strength U and over a long semi cylinder. The flow can be described using two dimensional potential theory
Find the velocity potential

2. Relevant equations

3. The attempt at a solution

I'm not sure what to do.

The equations for velocity potential are
vr = $$\frac{d\phi}{dr}$$ and v$$\theta$$ = $$\frac{d \phi}{rd \theta}$$

Can I say that there is no wind flowing trough the walls so vr = 0
and that v$$\theta$$ = U because air is incompressible?

I'm not sure at all.

3. The attempt at a solution