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-   -   3-D Water Flow in Fluent to Evaluate Pressures (https://www.cfd-online.com/Forums/fluent/67953-3-d-water-flow-fluent-evaluate-pressures.html)

 ahammack September 1, 2009 15:16

3-D Water Flow in Fluent to Evaluate Pressures

I am trying to simulate a water flow, and there are some problems with the pressures and velocity magnitudes. I have one inflow boundary and one outflow boundary. All other surfaces have wall boundary conditions with a specified shear stress of zero in all directions. I am trying to get my reference pressures correct. Therefore, I am running no flow through the model (by specifying zero velocity through my inflow boundary), and the pressures in the flow domain should be hydrostatic. When I look at my results, I am getting velocity magnitudes up to 5 m/s and pressure that are hydrostatic but do not have the correct magnitudes for the given z-location. What can I check to find out what is wrong with my solution? Does my boundary condition setup sound wrong? Any ideas why the velocity magnitudes are so far from the prescribed inflow velocities? Are there any solver options/tolerances I need to be sure to check?

 Chris D September 1, 2009 19:37

Have you tried to change your "inflow" and "outflow" boundary conditions to "wall" so that you, essentially, have a tank filled with water (i.e., no flow)? Also, I think you need to turn gravity on if you want to solve a hydrostatic problem (it's off by default.)

 ahammack September 1, 2009 22:41

3-D Water Flow in Fluent to Evaluate Pressures

Chris D,

Thanks for your reply! Yes, I have tried running a simulation with "wall" boundary conditions for all surfaces. I also have gravity turned on.

Another interesting thing I'm finding with my solution is that not only are the pressures not the hydrostatic values that I calculate analytically for the bottom of my flow domain (although I am getting a hydrostatic pressure distribution) the pressures are not constant for the same depths. This leads me to believe that the solver is not converging, but I can't seem to get any better solution behavior with the options I have changed so far.

Any suggestions?

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