Fluids

Fluids

Flow through a porous media

    • ganesh2516822
      Subscriber

      I'm trying to find out the thrust generated by an air bearing that I've designed. For that I need to know the pressure drop across the porous graphite. Below figure shows the inlet portion of the graphite section (porous media).

    • Rob
      Ansys Employee
      How well resolved is the mesh? Please plot a velocity contour across the device so we can see what's going on.
    • ganesh2516822
      Subscriber
      Thank you for your response
      I'll give you some mesh metrices Aspect ratio: 1.82
      Orthogonal quality: 0.78
      Skewness: 0.22

      The velocity contours are given below I've a hard time believing these results since there is zero velocity throughout the entire porous medium and also the residuals starts to diverge after about 350 iterations

    • Rob
      Ansys Employee
      I don't like the streaking in the lower image. Please zoom in on one of the narrow sections in the top image and replot with node values off.
    • ganesh2516822
      Subscriber
      You mean like this ? I don't know how to turn off the node values
    • Rob
      Ansys Employee
      More or less. Zoom in more on the higher velocity region. Top left of the contour panel you'll see an option for node values, deselect it.
    • ganesh2516822
      Subscriber
      There is no option to toggle node values. Or Is it the Vertex value/ face value option as seen below ? I tried to export only the cell centre values from Fluent, but unfortunately that option is also not available there.
    • Rob
      Ansys Employee
      OK, that's the image I want, but do the post processing in Fluent.
    • ganesh2516822
      Subscriber
      Alright. Turned off nodal values in fluent's post processor and this is what I got
      Do I need to refine the mesh at the top and send another plot ?
    • Rob
      Ansys Employee
      That looks like you have only two cells across the high(er) velocity region. You want at least 6, possibly more depending on the flow.
    • ganesh2516822
      Subscriber
      Here you go
    • Rob
      Ansys Employee
      Better. How's the solver behaving now?
    • ganesh2516822
      Subscriber
      The convergence plot follows this trend
    • Rob
      Ansys Employee
      That's a weird looking convergence plot. Try with a velocity inlet and see how it behaves.
    • ganesh2516822
      Subscriber
      Tried it already - yielded more or less the same plot


    • Rob
      Ansys Employee
      What are you using to initialise the model? I think you've got energy on; what is the gas density and how does the temperature field look?
    • ganesh2516822
      Subscriber
      I do have energy turned on. I'm using a density based solver, because the inlet air is actually from a compressor - (60psi , 450K compressed air) and I assumed the density is going to change further in its flow. I'll attach the temperature and density contour plot


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