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Old   July 8, 2013, 09:53
Question negative pressure
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Hi all.
I simulated one heat sink that has some microchannels. and boundary conditions:
1 velocity inlet for fluid inlet
2 pressure outlet for fluid outlet.
and two thermal boundary for heat sink.
when converge my RUN pressure @ out let become negative.!????
please help me.
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Old   July 10, 2013, 03:43
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You mean the pressure at the pressure outlet becomes negative?
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Old   July 10, 2013, 15:28
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Quote:
Originally Posted by RodriguezFatz View Post
You mean the pressure at the pressure outlet becomes negative?
yes.pressure @ outlet becomes negative
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Old   July 11, 2013, 03:03
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But this doesn't make any sense to me. If you set the outlet pressure to some value (as a BC), how can this value change during your simulation?
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Old   July 11, 2013, 04:17
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It is possible if there were massive reversed flow at the outlet but then the appropriateness of outlet B.C. might be in question.
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Old   July 11, 2013, 04:19
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Quote:
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It is possible if there were massive reversed flow at the outlet but then the appropriateness of outlet B.C. might be in question.
Yes, but he says "converge" in his initial post. I doubt he will get convergence in such a case.
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Old   July 12, 2013, 02:14
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yes my RUN become converge. But pressure value @ outlet is negative.for example pressure @ inlet B.C be 5687 Pa. and @ Outlet B.C be -879 Pa.
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Old   July 12, 2013, 03:33
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Please post images of the velocity and pressure contours and of the residuals.
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Old   July 12, 2013, 04:37
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Quote:
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yes my RUN become converge. But pressure value @ outlet is negative.for example pressure @ inlet B.C be 5687 Pa. and @ Outlet B.C be -879 Pa.
Generally, negative pressures are no problem, since your pressures are gauge pressures. There is a large positive offset of 1e5 Pa to them...
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