Ansys Learning Forum Forums Discuss Simulation Fluids Cyclone (Stairmand) simulation using RSM Reply To: Cyclone (Stairmand) simulation using RSM

Sem B.
Subscriber

Thank you again, Rob, for your help. 

These results include RSM results as well. The Euler number increased slightly to 6.3. (SSTCC: 6.2, Experiment: 5.1).

 

Ansys' guide on best practices for turbulence models explains that most of the benefits of RSM can also be achieved by enabling curvature correction in two-equation models EVMs. The results above seem to agree with this. Also, in literature I found that tangential/axial velocity profiles in cyclone simulations are often very similar between SSTCC and RSM. SST without CC produces results that clearly deviate (as expected). 

I have two ideas regarding the mismatch between experimental data and CFD results:

1) The polyhedral mesh makes it hard to capture this very narrow inner part at the center where the tangential velocity is low. A 'structured' hexahedral mesh might be a solution. However, I think that further refinement of a polyhedral mesh in that case should have also resulted in closer agreement, which is not seen in my grid convergence study (that shows that results are already (close to) grid indepedent.

2) The pseudo-transient simulations might be struggling with the vortex precession and therefore not able to capture this very narrow inner part with low tangential velocity. A transient simulation with averaged profiles over time could increase agreement to experimental data. However, would this result in closer agreement of Euler number to experimental data too? In the end, I would like to show that this approach can be used for optimization study, so transient simulations with high computational cost are not beneficial for that. 

 

Â