Fluids

Fluids

About the use of SBES shielding function in stirred tank

    • ztjia
      Subscriber

      The stirred tank is simulated by K-omega SST-SBES in fluent.The stirred tank is divided into two parts, sationary part and rotate part. SM(sliding mesh) was used to simulate the rotating of impeller.The sationary part and rotate part are connected by the way of interface.

      After transient simulation, The schematic diagram of the shielding function from the monitored y=0 plane reveals that the shielding function appears to be 1 at the junction of the slip grid, which should normally be 0 at all locations except for the boundary. How can this phenomenon be eliminated?

      I have checked the residual, all components reach the creteria 10e-3. The mesh quality of minimum Orthogonal Quality is 0.47, and I have improved the poor Quality cells, all the cells with orthogonal quality are above 0.667. but the phenomenon still exists.

      Thank you in advance.

    • Konstantine Kourbatski
      Ansys Employee
      Hello artest Is this a sliding mesh simulation where stationary and rotating zones are separated via non-conformal interfaces? If this is the case, then a possible problem is with the interface intersection. If interfaces are not completely intersect, e. g. there are locations with significant enough gaps between the interfaces, then walls will be created at those locations instead of an interior interface. These walls are just that - walls, so shears are calculated on them and the blending functions will have a value consistent with the walls, which is 1.
      Can you plot the same blending function, but with node values off to see true cell centered values calculated by the solver? Which version of Fluent are you using?
    • ztjia
      Subscriber
      thanks for your reply,Keaton.
      (1)the simulated domain consist of stationary and rotating zones. I firstly divide the conformal node mesh, and then decompose the region in Fluent and then assemble, so stationary and rotating zones are separated via conformal interfaces. but after I set "mesh interface, there appear two more wall zones and the two wall zones have the same id with interface zone as in follow picture. Why does this happen? Do this lead to the phenomenon that blending functions have a value consistent with the walls, which is 1.
      (2) The fluent version is 2021R1. I donot know how to plot the same blending function, but with node values off to see true cell centered values calculated by the solver. Hope for more help from you, thank you sincerely.


    • ztjia
      Subscriber
      more details about same blending function, but with node values off

    • Konstantine Kourbatski
      Ansys Employee
      the picture didn't come through. Please also check velocities and pressures at those locations at they are primary primitive variables. Also, refer to to Sec. 6.5. of Fluent's User guide on non-conformal interfaces, which will answer your questions about extra wall created during the interface set up.
      My recommendation in your case is to delete the non-conformal interface and then manually re-create it with Matching option for better calculation of the intersect. Also check what transferring motion across a mesh interface is set to.
    • DrAmine
      Ansys Employee
      Likely not 100% overlap. Remove snd recreate the interface as mentioned. You csn for sure list the interface before doing that to see if there is small non overlap portion being detected
    • ztjia
      Subscriber
      Thanks for your reply,Keaton and Dr Amine.
      After I transfer to "many to many interface method" by using "define/mesh-interfaces/one-to-one-pairing? "text command, mesh interface is created manually by matching method. And then the non-overlapping wall dispears. thanks for your help again.
    • DrAmine
      Ansys Employee
      great!
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