How to access the local residuals through UDF

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Valérie Gelbgras
Valérie Gelbgras Member, Employee Posts: 157
Name Dropper First Comment Photogenic First Anniversary
edited June 2023 in Fluids

How to access the local residuals through UDF

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  • Valérie Gelbgras
    Valérie Gelbgras Member, Employee Posts: 157
    Name Dropper First Comment Photogenic First Anniversary
    Answer ✓
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    In the TUI of Fluent, type: solve/set/expert and answer 'yes' to 'Save cell residuals for post-processing?'

    You can now access the residuals in the post-processing.

    It is also possible to access the residual values in a UDF. An example is provided below.

    In this example, a first DEFINE_ON_DEMAND stores the residual values of Pressure (= Mass Imbalance) X,Y and Z velocity, and the temperature in 5 UDMs.

    A second DEFINE_ON_DEMAND use a general way to access any post processing variable with C_POST_VAR. In this second macro, "temperature-residual" can be replaced by the name you would enter in the TUI if you were to use TUI commands to produce e.g. a contour plot...

    #include "udf.h"
    DEFINE_ON_DEMAND(report_residuals)
    {
        cell_t c;
        Thread *ct;
        Domain *d=Get_Domain(ROOT_DOMAIN_ID);
        
        if(RP_Get_Boolean("save-cell-residuals?"))
        {
            Message("\nSaving Residuals in UDMs...\n");
            thread_loop_c(ct,d)
            {
                begin_c_loop(c,ct)
                {
                    C_UDMI(c,ct,0) = C_STORAGE_R(c,ct, SV_P_R);
                    C_UDMI(c,ct,1) = C_STORAGE_R(c, ct, SV_U_R);
                    C_UDMI(c,ct,2) = C_STORAGE_R(c, ct, SV_V_R);
                    C_UDMI(c,ct,3) = C_STORAGE_R(c, ct, SV_W_R);
                    C_UDMI(c,ct,4) = C_STORAGE_R(c, ct, SV_T_R);
                }
                end_c_loop(c,ct)
            }
        }
        else
        {
            Message("\nResiduals are not set to be saved.\n");
        }
    }
    DEFINE_ON_DEMAND(alternative)
    {
        Domain *domain = Get_Domain(1);
    #if !RP_HOST
        Thread *t;
        cell_t c;
    #endif
        Cell_Function_Values(domain, "temperature-residual");
    #if !RP_HOST
        if (RP_Get_Boolean("save-cell-residuals?"))
        {
            Message0("\nSaving Residuals in UDMs...\n");
            thread_loop_c(t, domain)
            {
                begin_c_loop(c, t)
                {
                    C_UDMI(c, t, 4) = C_POST_VAR(c, t);
                }
                end_c_loop(c, t)
            }
        }
        else
        {
            Message0("\nResiduals are not set to be saved.\n");
        }
    #endif
    }