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mirror boundary condition

sriluta

I am running a transient simulation of an axial turbine with 10 stators without rotors. I am actually simulating two shock waves, after 180 degrees the shock wave is repeated or the second shock wave appears, as you can see in the picture. Therefore, I only want to simulate half the annulus, i.e. 180 degrees, and thus 5 stators to save computing resources.
To do this, I selected  in the geometry context  under  row 10 for periodicity   and in the meshing context  5 for meshing passages , thus creating a mesh for half the annulus. In the simulation context I then define hub and shroud as mirror,
that should be the procedure, right ?

greetings 

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  • Gaurav
    0


    In the meshing context 5 for meshing passages, thus creating a mesh for half the annulus -This is correct.

    In the simulation context define the hub and shroud as mirrors- not required. The hub and shroud are selected as walls.
    Only periodic surfaces as periodic walls

  • sriluta
    0 in reply to Gaurav

    thx for you're answer but I dont understand or the following option would be better ?  So since the flow of the 360 degree is axisymmetric, I thought I will use something like  a symmetry Plane at 180 degree and declare this symmetry plane as a mirror,  so that the results are transferred to the other 180 degrees, so that I just have to simulate the half of my annulus in the end. But yes, setting the hub and shroud as a mirror would have been wrong. 

Reply
  • sriluta
    0 in reply to Gaurav

    thx for you're answer but I dont understand or the following option would be better ?  So since the flow of the 360 degree is axisymmetric, I thought I will use something like  a symmetry Plane at 180 degree and declare this symmetry plane as a mirror,  so that the results are transferred to the other 180 degrees, so that I just have to simulate the half of my annulus in the end. But yes, setting the hub and shroud as a mirror would have been wrong. 

Children
  • Colinda
    +2 in reply to sriluta

    Are you sure the flow is symmetric and not periodic? These are not the same so if is important to understand the difference between these two and the impact on how the solution is transferred to the other 180 degrees. If you find it difficult to imagine, a very coarse simulation with each of these options could help to visualize the difference.

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