hi, I have developed a code for cartesian grid method. It gives good results for flow past circular cylinder. Now I want to simulate flow past an impulsively started airfoil. Can any one help me in specifying boundary condition for velocity for an impulsively started flow? Thanks for your advice

You apply U=1, and V=0 as an Initial condition in the domain keep the boundary conditions as it is. Sachin

hi sachin, thank you for your reply.. but by applying U=1 and V=0 how can we represent the impulsive motion? shouldn't the boundary condition be time dependent?

Assuming a Galilean transformation, it doesn't really matter whether you start the fluid impulsively past a fixed boundary (Sachin's approach) or you impulsively start the body into a fixed fluid (your approach). Sachin's recommendation is easier.