Learning Forum

[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"
DEFINE_ON_DEMAND(calculate_swirl_number)
{
    Domain*d;
    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]

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.