Hi,

I am new to CFD in Fenics and am currently going through the tutorial examples. Particularly interested in the 2d flow over the cylinder example. For a course I am doing, I have. a slight variation of this problem - the cylinder is rotating. (If there is fenics code available for this - please direct me).

Given the angular velocity and radius of the cylinder and coordinates of each point on the boundary, I can estimate the Dirichlet boundary condition for that point. I am unable to understand how to implement this is fenics. Basically, is it possible to get all the points of a boundary (cylinder wall here). Then use this to compute the value of the Dirichlet BC (this computation requires these coordinates) for each such point - then apply the computed Dirichlet BC to each point.

If w = angular velocity of cylinder, r = radius of cylinder => v = rw = velocity at cylinder surface.

Next for a point (x,y) on the cylinder surface, theta = tan(y/x) gives the counterclockwise angle from the horizontal wrt center of the cylinder.

Ux = -v*sin(theta) and Uy = v*cos(theta), [resolving vectors].

At each point on the boundary, x,y change so theta and hence Ux and Uy are different. So, how do I define these functions and then apply Ux and Uy as Boundary Conditions.

Thanks,

Abhay.