Discussion Forum

COMSOL has several types of solvers to choose from. If you choose a segregated solver, then that is what will occur. However, if you choose a stationary solution type, then pick PARDISO or UMFPACK solvers, this is a fully coupled direct solver, which is the best you can get for full coupling. However, if your problem is too large to fit in the computer memory, such as the case for most 3D problems, you will need to choose one of the iterative solvers to reduce memory. You have a choice, and it is not a fixed set of options.

thanks James for the help.

I am solving the time dependant or unsteady case, for steady case I have got good results. Can we have coupled solver for time dependant simulations?

Nadeem

if both models (time/steady state) are the same, try to use the solution of the steady state as the initial values for the time dependent computation. This can help convergence.

Cheers

thnks guys for ur help.

But the time dependant model is different from the steady state one. Also I am interested in the evolution of the solution with the time. The solvers seems to solve the equations in segregated form not in couple form. I can't find any option in comsol where i can used coupled solver. Also is there any option of implicit solver for time-dependant simulations? If i want to use dual time stepping is it avaiable in comsol?

cheers

Nadeem

The set up for the solver type is the same for steady-state as is the time-dependent or transient. For the transient case, there is an additional menu and parameters to control the time stepping. You can use the fully-coupled direct solver in the transient case as well.

Perhaps you should follow some of the tutorials or read in the manual if it is not intuitive from the GUI.

James i have looked at the documentation but i am not sure if the direct solver uses dual time stepping? can you suggest the solver and additional options for the coupled solver. I think I have not been able to explain the segregated and coupled solvers. For example Fluent solves all the equations together in coupled solver where as in segregated solver it solves momentum first and then updates the rest of the field variables in a sequence of steps.
Also i cant see any implicit solver options in the comsol. I can't find any option which can give me implicit and explicit solver options.

Looking for a detail reply.

Nadeem