oh you mean i should choose a time step (dt) that will give me a CFL = 1 according to the equation U dt/dx. I get it. For the velocity it initializes from (322 m/s), the required time step that gives me a CFL of 1 is 4.86e-5 s. So in order to simulate 1 second of flow, I need 20,573 time steps? That's huge.n