[hillehillea]

Hello CFD-Friends.
Does anyone know if there´s a possibility to start a transient simulation from a converged steady-state solution. Up to now, I managed it by copying the U,p,k,epsilon files to the time-directory of a turb foam case with the same mesh. Although I have very low final residuals in both, the transient and the steady-state case, the values of the pressure loss ,this is what I´m looking for, differ a lot.

[hjasak]

Yes, easy: just set your startTime and startFrom parameters in system/controlDict to start from the steady-state result.

Enjoy,

Hrv

[hillehillea]

Thank you for your quick response but I´m having a little trouble understanding your message. Problem 1: I use simpleFoam for the steady state solution and turbFoam for the transient simulation, so I have to create a new case, either by cloning the steadystate case, or by building a new case with turbFoam and copying the field data piece by piece.
Problem 2: Analysing the solution brought out big differences between the 2 simulations. Have you ever experienced huge differences (pressure loss nearly twice as high) between steady-state and transient simulation although the final residuals are of order 1e-7. The flow is obviously unsteady.
A short problem description:
flow through a baffle, simple geometry like an elbow divided in several channels, Newtonian, incompressible,2D,inlet-velocity = 24.9 m/s, pressure outlet, fine and good mesh,structured in near wall regions, discretisation scheme: only first-order accurate, nu = 2,8e-5.

[jballen]

Hello,

Suppose I wanted to compose an unsteady case, in which the acceleration due to gravity was changing with respect to time (ie: changing each time step).
Would it be possible to simply create say a /0/"g" file, in which a separate data file is called?
What would be a good way to accomplish this?

Resp.
Jeff