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How do I analyse the odd results (with porousSimpleFoam) ?

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Old   November 28, 2017, 12:54
Default How do I analyse the odd results (with porousSimpleFoam) ?
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Deep
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Hi,

I am trying to run a very simple simulation (a little more explanation may be found here) for flow through and over a porous medium using the porousSimpleFoam solver. I'm running the case for a short duration of time as I first want to confirm if it runs okay. There are quite a few observations I made and I want to understand how to tackle such odd/weird results. I'd be glad if someone can point me in the correct direction with some explanation or links.

  1. Initial residual and the Final residual remains exactly same in every iteration after the first resulting in No Iterations 0. What could be the reason for this? Is this normal behaviour?
  2. There are two velocity inlets and the velocities are 0.4 m/s and 0.04 m/s, yet the velocities in the flow region are going as high as 68 m/s. Why!!? Where do I look for the error?
  3. Subquestion to above question... in the log file, I never see any status line for U (only for p, epsilon and k). This is true for at least a few other solvers too. Why not for U? Is there something that I'm missing?
  4. porousSimpleFoam apparently doesn't solve energy equation and hence does not create any T fields in subsequent time step folders. Why does it need T file in the 0 folder then!? The tutorials for porousSimpleFoam have T file in their 0 folder.
  5. I'm running the case only for 10 time steps of 1s each yet while post-processing the results, paraview freezes in-between two time steps and screen greys out. I'm wondering if this is because I'm running this on single processor. Even then 10 steps is literally nothing to cause such intense resource consumption.
  6. Which is the best solver if I want to take into account temperature variations as well?
Pardon me if am asking silly questions, I'm not very experienced with OF yet.
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Old   January 15, 2018, 05:46
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Can anyone answer this please?
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Old   January 16, 2018, 14:54
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Çağatay Emre Ayhan
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Hello Deep, Did you solve the high velocity problem,second problem,? I have the same problem.
Quote:
Originally Posted by deepbandivadekar View Post
Hi,

I am trying to run a very simple simulation (a little more explanation may be found here) for flow through and over a porous medium using the porousSimpleFoam solver. I'm running the case for a short duration of time as I first want to confirm if it runs okay. There are quite a few observations I made and I want to understand how to tackle such odd/weird results. I'd be glad if someone can point me in the correct direction with some explanation or links.

  1. Initial residual and the Final residual remains exactly same in every iteration after the first resulting in No Iterations 0. What could be the reason for this? Is this normal behaviour?
  2. There are two velocity inlets and the velocities are 0.4 m/s and 0.04 m/s, yet the velocities in the flow region are going as high as 68 m/s. Why!!? Where do I look for the error?
  3. Subquestion to above question... in the log file, I never see any status line for U (only for p, epsilon and k). This is true for at least a few other solvers too. Why not for U? Is there something that I'm missing?
  4. porousSimpleFoam apparently doesn't solve energy equation and hence does not create any T fields in subsequent time step folders. Why does it need T file in the 0 folder then!? The tutorials for porousSimpleFoam have T file in their 0 folder.
  5. I'm running the case only for 10 time steps of 1s each yet while post-processing the results, paraview freezes in-between two time steps and screen greys out. I'm wondering if this is because I'm running this on single processor. Even then 10 steps is literally nothing to cause such intense resource consumption.
  6. Which is the best solver if I want to take into account temperature variations as well?
Pardon me if am asking silly questions, I'm not very experienced with OF yet.
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Old   January 17, 2018, 06:15
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Unfortunately, no.
Am trying out other solvers now.
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