KNOWN ISSUE: Adaptive timestepping cases run in parallel use the wrong RMS Courant number (Class 3 Error)
Transient cases which use the Adaptive option for Timesteps and use the RMS Courant Number option to control the timestep adaption will show different RMS Courant Numbers and therefore potentially different adaptive timesteps depending upon the number of partitions being used for a parallel run.
For parallel runs, the calculation of RMS Courant Number is incorrect and will produce a result that is too small. This means that the CFX-Solver will potentially increase the timestep when it should not, resulting in loss of accuracy. Serial runs are correct.
No workaround is currently available.
ANSYS CFX Release 13.0. A custom executable for ANSYS CFX Release 12.1 is available on request.