Institut für Informatik Scientific Computing in Computer Science Practical Course SC & V Time Discretisation Dr. Miriam Mehl

Time Discretisation Euler step for momentum equations pressure ensures mass conservation –poisson equation –correction of velocities

Time Step – Stability small reynolds number: dt < dx 2 high reynolds number: dt < dx

Algorithm (One Time Step) (1)compute time step dt (2)set boundary values (3)compute preliminary velocities (4)solve pressure equation (5)compute final velocities

Debugging simple setup: –one(!!!) time step –external forces zero test preliminary velocities at boundaries test residual of the pressure equation

Debugging enhanced setup: –initialize velocities constant but with nonzero boundary values test preliminary velocities