Learning Forum

[seung mook park]

i only change density constant to ideal gas.

i don't know why it become supersonic.

it is PBS and my inlet condition is 

[NickFL]

First thing, check your dimensions. Sometimes when importing the mesh we accidentally import it in mm when we want m or something. This is typically a consequence of such a mistake. In the first image you are also at 700 m/s. I do not know what material and pressure you are at, but I would image this should be a compressible flow. What did your hand calculations give you for a max velocity?

[seung mook park]

 

working fluid is air, inlet condition is 192 kPa, 2067K, 0.007551m^2 and my hand calculation result is 673m/s.

it is not supersonic at inlet.

 

[NickFL]

it is not supersonic at inlet.

If it is not supersonic at the inlet, then go back and review the boundary conditions. The outlet boundary is supersonic in your calculation. This means, if you were expecting subsonic flow, that there is a problem here. When the flow is supersonic it uses the upstream inlet conditions and the downstream is swept away (the characterstics of the equations do this).

[seung mook park]

you mean i have to change my outlet boundary conditions?

 

[NickFL]

Review: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v221/en/flu_ug/flu_ug_sec_compress_inputs.html?q=modeling%20inputs%20for%20compressible%20flow

[seung mook park]

Thank you for answering!