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Static pressure results all over the place

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Old   January 12, 2016, 04:53
Default Static pressure results all over the place
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a m s
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***SOLVED**** Reference value of pressure was set to the sinusoidal inlet. Moved the reference value location to somewhere far away in the domain


I am modelling the following:
  • The domain is a large rectangle (to negate any inlet, outlet and edge effects)
  • It is axisymmetric about the bottom edge
  • It has a pipe inlet protruding into the domain running very close to the axis with a sinusoidal velocity profile (to model a periodic flow)
  • The rest of the inlet face is zero gauge pressure, zero velocity, atmospheric air
  • A short way down from the end of a pipe is an aerofoil type shape
  • The model is for an unsteady ejector where with each periodic pulse of flow, a vortex rolls up from the edge of the pipe exit, entraining the surrounding ambient air
  • the vortex then moves down below the ejector with the overall aim to increase the thrust of the jet of fluid.

I have run the simulation for a number of cycles of the jet pulse (to obtain stable results) and with a large number of iterations per timestep.

When I come to read the results in CFD post the velocity plot looks ok but the static pressure plot is all over the place. The surrounding 'ambient air' pressure keeps changing when it should be ~constant and at the start of the cycle the values are very negative. To be able to see the actual vortex, the contour range has to be changed for each frame to a suitable range.

One note is that when running the calculation the property values are referenced to the ambient air inlet (which is constant anyway).

Any ideas as to what I'm doing wrong to have such erratic static pressure plots? Can provide further details if necessary.

Thank you for any help in advance!

Last edited by Easyqus; January 12, 2016 at 06:53.
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Old   January 12, 2016, 05:37
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a m s
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From looking at the results it appears that the sinusoidal inlet is at a constant static pressure throughout but the rest of the domains changing static pressure constantly.

What should I use for the reference values when setting up the solver?
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aerofoil, ansys, fluent, pressure, static

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