Free surface flow modelling using SPH with periodic boundary condition

hosseinbasser · February 14, 2018, 21:12

Hi all,
I am trying to simulate a free surface flow over an inclined surface with explicit incompressible SPH and periodic boundary conditions in x-direction. The flow is driven by gravity in x direction (gsin(theta)). But I can't get the analytical solution and the velocity keeps increasing until it converges to a value which is not what I expect (as you can see in the figure). Does any of you have any idea what could cause this problem?
Thanks a lot

piu58 · February 15, 2018, 00:33

I don't know how you set up your case. Inclined and periodical b.c. does not fit. Do you use inclined gravity?

Periodic b.c. couples the outlet with the inlet. You have to ensure, that from physics both sides are real equal. If the outlet transforms energy to the inlet, your velocity will increase until blowup.

hosseinbasser · February 15, 2018, 00:42

Thank you for your response.
What I did was I set up a horizontal domain and inserted a body force in horizontal direction to account for the gravity (g*sin(theta)).
Best regards

February 15, 2018, 00:33		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	I don't know how you set up your case. Inclined and periodical b.c. does not fit. Do you use inclined gravity? Periodic b.c. couples the outlet with the inlet. You have to ensure, that from physics both sides are real equal. If the outlet transforms energy to the inlet, your velocity will increase until blowup. hosseinbasser likes this. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

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February 15, 2018, 00:42		#3
hosseinbasser New Member Victoria Join Date: Feb 2018 Posts: 3 Rep Power: 8	Thank you for your response. What I did was I set up a horizontal domain and inserted a body force in horizontal direction to account for the gravity (g*sin(theta)). Best regards