Obtaining swirl number from UDF

    • jack forster

      I am simulating flow into a combustion chamber. I am trying to obtain the swirl number at multiple cross sectional planes. I have compiled the UDF source code with no errors but I do not know how to extract the value at a specific plane. Is this done within report definitions? 

      This is the UDF code I am using:

      include "udf.h"
          Thread *t;
          cell_t c;
          real rho, mu, U_axial, U_radial, U_circumferential, Swirl_Number;
          real angular_momentum = 0.0, axial_momentum = 0.0;
          d = Get_Domain(1);
          /* Get the density and viscosity of the fluid */
          rho = RP_Get_Real("operating-density");
          mu = RP_Get_Real("operating-viscosity"); 
          /* Loop over all cells in all threads */
          thread_loop_c (t, d)
              begin_c_loop (c, t)
                  /* Get the axial, radial, and circumferential velocities */
                  U_axial = C_U(c,t);
                  U_radial = C_V(c,t);
                  U_circumferential = C_W(c,t);
                  /* Calculate the angular momentum and axial momentum */
                  axial_momentum += rho * U_axial * C_VOLUME(c,t);
                  angular_momentum += rho * (C_UDMI(c,t,0)) * C_VOLUME(c,t);
              end_c_loop (c, t)
          /* Calculate the swirl number */
          Swirl_Number = 2 * angular_momentum / (axial_momentum * mu);
          /* Print the swirl number to the console */
          Message("Swirl Number: %g\n", Swirl_Number);

      Any help would be greatly appreciated.



    • Rob
      Ansys Employee

      Have you looked in the Contour plots? Under Velocity you'll find axial & tangential velocity. In Mesh you'll find Axial and Radial positions. These are relative to the local cell zone axis (set in the Cell Zone panel(s)). You may want a Custom Field Function. You can then report these using the surface reports and/or plot the contours. 

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