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Negative pressure values 2D laminar tube flow

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Hello community!
I do model 2D laminar air flow within compliant (flexible) tube with a constriction by introducing gauge pressure (relative pressure) boundaries (inlet pressure = 400[Pa] and outlet pressure pressure = 0[Pa]). I do so because velocity boundary condition at the inlet would not reflect the physics appropriately (it would prescribe mass flow eintering the tube what is not the case). The simulation runs stable. I do observe altering pressure values (with zero crossing) in the middle of the channel. A pressure drop within the constriction is plausible but what do negative pressure values mean? What does COMSOL relate the pressure to? Is it always the zero pressure boundary or outlet?

Many Thanks in advance!

With kind regards

Alexander

0 Replies Last Post 13.02.2017, 09:38 GMT-5
COMSOL Moderator

Hello Alexander Werth

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