Fluids

Fluids

Convergence?

    • hugo CFD
      Subscriber

      I simulated a flow of air going through a plate heat exchanger. The duct has fins of triangular section. The simulation is performed for steady state.


      The mesh data is:


      Skewness: 0.79        Aspect ratio: 3.19        Orthogonal quality: 0.43


      The convergence residues obtained were:



      What is the reason associated with the irregularity of the lines? Although the mesh is of good quality, can the poorer elements still cause this effect? May I consider that there is convergence of the solution?


       


      Thank you

    • Rob
      Ansys Employee

      Have a look at the flow field and plot images every few iterations to compare: I suspect the flow is marginally transient. 

    • hugo CFD
      Subscriber

      What do you mean by flow field?

    • Rob
      Ansys Employee

      Velocity, pressure etc.  You're usually looking for flow separation or regions where the Coanda effect may occur. 

    • hugo CFD
      Subscriber

      The charts of velocity and pressure in direction of the flow.


            


      Variations in velocity and pressure are a consequence of the flow through the fins.


      I just want to add one point. The following figure shows the geometry of the fins placed as a flow obstruction.


       


      However I did the same analysis for the following fins.



       


      All dimensions and analysis conditions are the same as the previous example. However the residues obtained are quite different.



      Why is there such a difference?

    • DrAmine
      Ansys Employee

      Increase resolution of the triangular fines and pseudo transient coupled solver. Mesh not ideal.

    • hugo CFD
      Subscriber

      yes. The pseudo transient and coupled solver was thar i used.


      Why mesh is not ideal?

    • DrAmine
      Ansys Employee
      Curvature and angle are not well resolved along the obstacles
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