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Interface between the moving and stationary zones generates wrong results as the moving zone rotates #2255
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Are you able to reproduce this behaviour with any other cases, say a rotating cylinder perhaps? To me it looks like the strange behaviour develops from the area in your mesh where the mesh density along the interface is visibily different (north and south of the image shown). This could be a discretization issue rather than a bug with the solver? |
I just found a heap buffer overflow in the interface code, mentioning it here in case it is related #2246 (comment) |
I have tried two additional simulations with the same cylinder mesh: 1. Stationary cylinder The settings are almost identical, except: su2Config.cfg:
zone_rot.cfg:
In other words, this is a transient stationary cylinder simulation with two zones. As the axial velocity and eddy viscosity evolutions show below, the simulation runs smoothly and no discontinuities or unphysical flow result is observed around the zone interface. 2. Slowly rotating cylinder I also tried a very slowly rotating cylinder to see if the error will occur even with a slow rotation. The rotational speed of the inner zone is around 0.03 rad/s, which corresponds to a surface angular speed (0.025 m/s) equal to the 0.25% of the freestream velocity (Uinf=10 m/s). zone_rot.cfg:
The time step is set as the one used for the stationary cylinder. Each time step corresponds to a 0.01 deg rotation of the inner zone. The below animation shows the movement of the cells on the interface: The below animations show the axial velocity and eddy viscosity evolution. The results should not deviate much from the stationary cylinder results as the angular speed of the cylinder is quite low compared to the freestream. However, it is not the case for this simulation. Also, the discontinuity on the downstream part of the interface is quite apparent even at the earlier time steps. As the simulation progresses, unphysical flow results (non-zero eddy viscosity at the top part of the interface) appear, and eventually, the simulation diverges. |
I ran your test case with the fixes from #2246 and the address sanitizer, it still shows the behaviour that you describe and the address sanitizer did not detect anything else. So it's probably not related to the aforementioned overflow. |
Does it also occur without turbulence, so for INC_NAVIER_STOKES and Re=50-180? |
There are 2 cases in the testcases repository, both are using the Euler solver. Maybe also check if your case is running correctly with the settings from those testcases. |
Earlier, I was defining the mesh movement for the static zone as:
since it was stationary. However, after checking the test cases, I found that the stator zones should also be defined as moving as
even though the mesh stays stationary. In that case, the unphysical flow results I presented earlier vanished. Earlier, I tried the cylinder test case with the inner zone having
and the outer zone having where the simulation gave physically viable results. I guess the zone interface may not accurately work if the Also, the sliding_interface/rotating_cylinders test case diverges with the given .cfg files. At around the 775th time step, I received the following error message:
However, it works just fine if the simulations are done in subsonic flow (e.g. |
Summary
The fluid should freely pass a fluid interface between RANS zones. However, in some unsteady 2D simulations, I encountered the interface generating unexpected flow solutions which is observed through the increased eddy viscosity and unphysical velocity as the inner zone rotates with respect to the stationary outer zone.
I have tried using
however the problem persisted.
Setup
Mesh
File:
vawt_ami.su2
Configuration files
su2Config.cfg:
zone_sta.cfg:
zone_rot.cfg:
Simulation results
Velocity
Eddy viscosity
Desktop
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