ishaandesai
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March 20, 2018 at 11:03 am in reply to: Fluctuations in velocity profile at inlet for turbulent channel flow setup #2814ishaandesaiMember
Hey Marc,
thanks for the explanation. I now understand what you are suggesting but am having difficulty in correlating how this would represent my channel flow. In the Poisuelle example, using periodic boundaries in streamwise direction makes sense if you wish to simulate a portion of pipe/channel after the developing length. If I give periodicity in my case and also specify the value of pressure drop between inlet-outlet, it is as good as simulating a flow beyond the developing length, which I do not know in my duct case as the geometry is not very simple. This is my difficulty, please correct me if there is any gap in physical understanding. I wish to simulate real flow and see the behavior as in transition state as it is going towards a steady state.
March 18, 2018 at 9:00 am in reply to: Fluctuations in velocity profile at inlet for turbulent channel flow setup #2811ishaandesaiMemberHello Marc,
Sorry for the very late reply, I was on a short vacation. I cannot grasp the strategies you are suggesting there entirely, “use periodic boundaries in span and streamwise direction” and “body force to drive the flow”. I think by the first comment you mean I should make my inlet and outlets periodic, but then do I also give periodicity to the walls in all directions ? I did not understand the second comment
ishaandesaiMemberThank you for your response Marc, I understand the limitations of my machine with respect to the case I am trying to set.
Regards
IshaanishaandesaiMemberHello Marc,
Right now I am using bounceback wall boundary as the Bouzidi implementation is giving me a similar error as I stated earlier. I have implemented an inlet condition of constant velocity, but after some length of my duct, I see velocity fluctuations. This is what they look like: https://ibb.co/cAM3Ax
My case setup is as follows:
Inlet velocity = 10 m/s
Characteristic viscosity = 1e-6 m2/s (water at 23 degrees)
Reynolds Number = 183000
Lattice velocity = 0.05
LatticeL = 0.001
I wish to further refine my case by reducing LatticeU and LatticeL, but the computing power of my machine is restricting me from doing so. I cannot find a good explanation for the velocity fluctuation. I am guessing that such fluctuations (like sound waves) will affect my analysis of finding high pressure zones and recirculation areas in my duct geometryThanks and Regards
IshaanishaandesaiMemberHello Marc,
thanks for your reply, I checked for overlap of inlet, outlet nodes and boundary nodes and indeed I found some errors. Restoring those errors and changing the boundary condition from offLattice Bouzidi implemendation to Bounceback implementation has got my simulation running. The issue now is that my STL has curved sections so is it advisable to stick with Bounceback boundaries ? Or should I attempt to go with Bouzidi offLattice ?
I am also having some issues with the inlet conditions but unfortunately I am not able to attach an image on my reply in this forum, if you can help me there that would be great. I can explain my problem much better then.
Thanks and Regards
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