unsteady flow problem

Hellodeutsch · May 10, 2017, 09:18

Hello guys, im using an openfoam software to do my master project at the moment. And my simulation is about DNS on Internal combustion engine. So i need to make the inlet velocity time dependent.But in my result, the flow value like velocity in the flowfield except inlet place dont have obvious change. It looks like the change of value at other place cannot catch up the change of inlet velocity.If i made the inlet velocity invarient to do a steady simulation, the result is reasonable.
Could you please give me some possibilities on this problem?
Thanks in advance

piu58 · May 10, 2017, 09:54

Are you sure that you want (and are be a able) to solve such a complicated problem with DNS?

We cannot give an answer if we don't know, which solver you use, and how your boundary conditions are set.

Hellodeutsch · May 11, 2017, 07:07

My solver is a self-made DNS simulation software made by our lab. Maybe it's hard to describe it detailly in such a short Message. But still thanks for your reply!

May 10, 2017, 09:18	unsteady flow problem	#1
Hellodeutsch New Member ke Li Join Date: May 2017 Posts: 2 Rep Power: 0	Hello guys, im using an openfoam software to do my master project at the moment. And my simulation is about DNS on Internal combustion engine. So i need to make the inlet velocity time dependent.But in my result, the flow value like velocity in the flowfield except inlet place dont have obvious change. It looks like the change of value at other place cannot catch up the change of inlet velocity.If i made the inlet velocity invarient to do a steady simulation, the result is reasonable. Could you please give me some possibilities on this problem? Thanks in advance

May 10, 2017, 09:54		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	Are you sure that you want (and are be a able) to solve such a complicated problem with DNS? We cannot give an answer if we don't know, which solver you use, and how your boundary conditions are set. __________________ 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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May 11, 2017, 07:07		#3
Hellodeutsch New Member ke Li Join Date: May 2017 Posts: 2 Rep Power: 0	My solver is a self-made DNS simulation software made by our lab. Maybe it's hard to describe it detailly in such a short Message. But still thanks for your reply!