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Divergence of ducted propeller simulation using MRF simpleFoam |
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January 13, 2020, 06:58 |
Divergence of ducted propeller simulation using MRF simpleFoam
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#1 | |||
Senior Member
Kmeti Rao
Join Date: May 2019
Posts: 145
Rep Power: 8 |
Dear Foamers,
I am simulating a propeller enclosed within a duct. The case is similar to what I have described in this thread One half propeller simulation with MRFSimpleFoam crashing, and the only difference from previous case to this case is that I have a duct enclosing the propeller. In both cases I am simulating only half of the propeller as the simulation area is symmetric. I am using OpenFOAM 6 from openfoam.org, with RANS K-omegat SST to solve the turbulence and the solver algorithm is simpleFoam with MRF(by defining static and dynamic regions using cyclicAMI). So far I have had success in the simulation of the propeller using this method and got satisfying results which were similar to the analytical results, obtained from BEMT method. Now the introduction of duct have resulted in divergence(attached the images and settings in the end) To study the cause of divergence, I have done difference simulations, which includes the following setup. 1) The duct being outside the MRF domain 2) The duct inside the MRF domain In both cases I didn't get any success. I have crosschecked my checkMesh results as well as yPlus values and it seems to be ok. Since I got success with open rotor simulation, I have maintained most of the settings as it is. Please let me know if any of you have faced similar problems, and what are the methodologies you have used to overcome the above mentioned problem. I will be open to any other suggestions as well. fvSchemes: Quote:
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open_rotor.png ducted_rotor.png Thank you all in advance, Kmeti Rao |
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January 13, 2020, 10:35 |
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#2 |
Senior Member
Kmeti Rao
Join Date: May 2019
Posts: 145
Rep Power: 8 |
In the above result presented I have my Duct placed inside the simulation domain, with this settings, however good the mesh is I never achieved the convergence.
Therefore I have started the simulation by placing the Duct outside the MRF region. For this I have to make the MRF region so small that the propeller just fits inside the MRF region. This has also resulted in divergence. Therefore I have carried out a test to study the influence of MRF region diameter on the simulation results. As expected the simulation of single propeller with smaller MRF diameter did not converge, while increasing the MRF domain size a little by 10% has resulted in periodic oscillation of results about a value. By increasing the MRF domain by 20% and more I started to get stable, results. Therefore placing the duct outside the MRF region has also resulted in poor convergence. It would be great if any of the experts in this field gives me a small hint, with which I can carry out my simulations further. Thank you Kmeti Rao |
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convergence failure, duct, mrf simplefoam, propeller, rotor |
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