If you are using Fluent, define your velocity contours in Results-> Graphics-> Contours. Then go to Calculation Activities -> Solution Animations and define new animations. In there, you can specify the frequency with which you store your contours. The velocity results will be instantaneous velocities for each specified time step. Also, you may save the results by going to Calculation Activities -> Autosave (Every Time Steps) and save the desired quantities in desired time steps.n