periodic boundary condition-profile

Lilly · May 24, 2012, 10:20

Dear all,

we want to simulate a periodic boundary condition using FLUENT for a straight tube. Inlet and outlet of the tube should be "connected" via this periodic boundary condition and we finally managed to reach this connection.
Our problem is that we wanted to use a sinusoidal pressure variation (pressure variation in time) at the "connected" boundaries. Therefore we created a profile-file, but we cannot set it with the periodic boundary condition (we can just set flow direction, pressure gradient and mass flow there). Is there any way to set our profile as periodic bc?
Thanks a million for all your help and ideas!
Lilly

sbaffini · May 24, 2012, 17:49

If your grid has identical cells distributions on both inlet and outlet then the periodic condition can be set in fluent by grid/modify/make-periodic, as you probably already figured out.

However, i don't understand why your sinusoidal pressure variation is not compatible with periodic b.c.s (say, fixing the pressure gradient). If the problem is the time variation you can simply put the pressure gradient equal to 0 in the relative periodic boundary condition panel and then add an x-source term via UDF which is the exact replica of the pressure gradient (in UDFs you can add the time-variation).

May 24, 2012, 10:20	periodic boundary condition-profile	#1
Lilly Senior Member Join Date: Feb 2011 Posts: 140 Rep Power: 15	Dear all, we want to simulate a periodic boundary condition using FLUENT for a straight tube. Inlet and outlet of the tube should be "connected" via this periodic boundary condition and we finally managed to reach this connection. Our problem is that we wanted to use a sinusoidal pressure variation (pressure variation in time) at the "connected" boundaries. Therefore we created a profile-file, but we cannot set it with the periodic boundary condition (we can just set flow direction, pressure gradient and mass flow there). Is there any way to set our profile as periodic bc? Thanks a million for all your help and ideas! Lilly

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May 24, 2012, 17:49		#2
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,151 Blog Entries: 29 Rep Power: 39	If your grid has identical cells distributions on both inlet and outlet then the periodic condition can be set in fluent by grid/modify/make-periodic, as you probably already figured out. However, i don't understand why your sinusoidal pressure variation is not compatible with periodic b.c.s (say, fixing the pressure gradient). If the problem is the time variation you can simply put the pressure gradient equal to 0 in the relative periodic boundary condition panel and then add an x-source term via UDF which is the exact replica of the pressure gradient (in UDFs you can add the time-variation).