dynamicsoar's log


ANSYS Fluent: you should probably not use hybrid initialisation for transient, if there are 2 or more outlets

Effect of the initialisation methods on streamlines.

Where there are two outlets, and you are computing transient simulation with ANSYS Fluent, you should probably not use hybrid initialisation. Or at least you should be careful and check the resulting flow field before proceeding. The hybrid initialisation, as far as I understand it, can be "smarter" guess of the initial flow field so the convergence would possibly be quicker. However, as shown in the figure, where I just wanted the uniform flow to be slanted so the wing (too tiny to see) experiences some positive (or negative) AoA, the hybrid initialisation can result in unwanted flow field, whereas the standard one results in appropriate flow field.

This behaviour is apparently independent of the mesh density. Actually the figure shown above is the one computed in the student version of ANSYS (I initially encountered the problem in the "real" simulation but just wanted to test with much simpler situation as it's much quicker for debugging).