Fluids

Fluids

Topics relate to Fluent, CFX, Turbogrid and more

Convergence issue in Supersonic Simulation

    • Ashwin Subramanian Murugan
      Subscriber

      Hello, Im trying to simulate a supersonic isolator. I have attached a picture of my mesh.

      The inlet conditions - Pressure inlet - total pressure = 207kpa, gauge pressure is 42kpa total temp = 310 k

      outlet - pressure outlet - gauge pressure = 1pa

      density based solver, k-w sst 

      However, I'm no matter what I do, I'm not able to get a good steady solution.

      Any advice on how to solve this problem?

    • Essence
      Ansys Employee

      Hello,

      By looking at the mesh, I am assuming the aspect ratio is well in the limits. Could you please share the screenshots of the k-w SST panel, Methods and Controls panel? 

    • Ashwin Subramanian Murugan
      Subscriber

       

      Hello, I've attached all of it. I've also added mesh metrics of the aspect ratio.

       

       

    • Essence
      Ansys Employee

      Hello,

      Select High Order Term Relaxation in Methods. Reduce the Courant number to 2.75 for initial iterations. Reduce the URFs to 0.5 (k and omega). Disable the Compressibility effects in k-w SST and try running. Also, let me know the net mass flow rate, net heat transfer rate and apply a variable report definition to judge the convergence. Use Green-Gauss node based gradient.

    • Ashwin Subramanian Murugan
      Subscriber

      Hello i tried all the suggestions you had mentioned. I set the courant number to 2.75 for about 1000 iterations and then changed it back to 5. I selected higher order term relaxations, disabled compressibility effects in k-w sst, reduced urfs, used green gauss node based gradient. The walls are adiabatic so heat flow was 0. But I'm still no where near convergence. I also used outlet pressure as a monitor . Pls help, thanks. 

    • RK
      Ansys Employee

       

       

      Hello, 

      You can refer to this tutorial: Chapter 7: Modeling Transient Compressible Flow (ansys.com)

      You can use high speed numerics ( see the user's guide for more info) to get a stable solution. The Mach number associated with pressure values can also be run using the pressure based solver. I suggest trying wth PBNS. 

       

       

Viewing 5 reply threads
  • You must be logged in to reply to this topic.