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-   -   Shock structure blurred in rhoPimpleFoam kEpsilon model. (https://www.cfd-online.com/Forums/openfoam-solving/224146-shock-structure-blurred-rhopimplefoam-kepsilon-model.html)

kim4545 February 9, 2020 01:43

Shock structure blurred in rhoPimpleFoam kEpsilon model.
 
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Hi, Foamers!

I'm simulating the 2D axisymmetric busemann intake for scramjet intake design

rhoPimpleFoam and kEpsilon turbulence model was used, but in result the shock wave structure is somewhat blurred than the laminar model.

So i tried to compare the result with ANSYS FlUENT.

In ANSYS FLUENT, the shock structure is not blurred even though the number of the mesh and quality are almost same (80,000)

Is there any reason that rhoPimpleFoam kEpsilon model cannot resolve the shock wave structure(Density gradient, Schileren image) well?

Than, what solver or turbulence model should i use to capture the shock wave?

Density gradient plots of ANSYS FLUENT and rhoPimpleFoam are attached

kim4545 February 10, 2020 00:13

solved
 
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I might find the reason.

The inlet and wall turbulence dissipation rate(Epsilon) boundary condition was 1 order of magnitude smaller than the actual value.

I messed up calculating the initial Epsilon value by setting the characteristic length as an inlet diameter.

I substituted it with the order of the turbulent boundary layer thickness.

Maybe, the low epsilon value leads to overestimating k, making the shock structure blurred.


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