local time stepping and pseudo time
 

Hi,

I am trying to understand the basic methods of NUMECA but there are still some things not clear to me. I really hope somebody will help me. So, let's start:

1. NUMECA uses a four-stage explicit Runge-Kutta method to solve the equation: int(dU/dt dV) + sum(F_I*D_S) + sum(F_V*D_S) = int(Q dV) (F_I, F_V: inviscous and viscous fluxes; U: solution vector). What happens if the computed problem is "steady"? 2. On the numeical model page, the user has to specify a CFL-number, which is basically v*Delta_t/Delta_x. I have heard of methods that use a time stepping for steady computations to increase stability. How does it work with NUMECA? 3. Moreover to the general Navier-Stokes equation, a term with pseudo time is added. What does it mean? Is the pseudo time defined by the CFL number?

Thanks-.