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Submerged intake: Reverse flow in inlet outlet, turbulent viscosity limited

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Old   September 13, 2019, 07:08
Post Submerged intake: Reverse flow in inlet outlet, turbulent viscosity limited
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Hi all,

I am new using ansys fluent. For my thesis project my task is to analyse a NACA submerged inlet in cruise conditions: 39000 ft, Mach 0.8.

Due to the shape of the inlet, a pair of vortices will be generated. For this type of submerged intake, it is important that the boundary layer is accurately resolved. This is the reason that I've applied an inflation layer at every physical wall.

The computational domain is divided into 7 parts. See file attached. The incoming air goes from right to left. The upper part consists of 3 blocks. Mapped mesh has been applied to those blocks. For the 3 blocks near the fuselage which is a physical wall, which is an inflation layer, the blocks are filled with tetrahedrons. Ansys doesn't allow mapped mesh and inflation layer, so I use tetredrons. For the last part, which is the duct downstream of the submerged intake, somehow an inflation layer can be combined with a mapped mesh. Since it works, I left it as it is. The inlet and outlet are around 6-7 times characteristic length of the submerged intake away from the submerged intake in the middle of the domain. The mesh consists of 5.6M cells.

The boundary conditions are as follows: pressure inlet, pressure outlet, pressure outlet with target mass flow (at the end of the duct downstream of the submerged intake), the far-field is a free slip-wall. For the simulation I changed the pressure outlet with target mass flow as wall.

I've tried to run different simulations at other conditions: 0 ft, Mach 0.20, such that it is faster to check if the settings are correct or not. I've run laminar, k-e, k-omega models.

The errors (log file attached) that are shown during the simulation are:

reversed flow in xxxx faces on pressure-inlet 6.
reversed flow in xxxx faces on pressure-outlet 7.
turbulent viscosity limited to viscosity ratio of 1.000000e+05 in xxxxxxx cells
Stabilizing pressure correction to enhance linear solver robustness.

Divergence detected in AMG solver: k
Divergence detected in AMG solver: omega
Error at host: floating point exception
Error at Node 0: floating point exception
Error: floating point exception
Error Object: #f


And then the simulation aborts.

Does anyone know the reason why it went wrong, or anyone that has tips on mesh/solving those problems?

Thanks in advance!

Steve
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File Type: txt logfile.txt (72.6 KB, 2 views)
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