[Lilly]

Hello,
I am pretty new with cfd-simulations and I have got a problem with the type of grid I am using for my simulation:
When I am using a structured hexahedral volume mesh my results differ a lot from the results I am getting using an unstructured tetrahedral volume mesh. I already tried using grids with a different number of elements (from about 50.000 up to a few million elements) for both cases. The results are converging in each case, but the difference in the order of magnitude of the results comparing both grid types is up to two!
The parameter I am interested in is the area weighted mass fraction of contrast agent in blood. Since the velocity profiles look almost(!) the same for both cases, could it be some problem with the diffusion-convection-equation, which doesn’t get along with the tetrahedral mesh (just a stupid thought of me)? Do you have any idea how I can fix this problem?
It would be really nice, if one of you could help me!
Thanks a million,
Lilly