Learning Forum

[atulsingh92]

How do we get the total pressure at a surface? I tried something like followsnvoid dynamic_pressure()nnt = Lookup_Thread(domain, id);? //outlet edge (for a 2D case) is at id=6;nbegin_f_loop(f,t)n{n Amag = NV_MAG(area);n vsquared = pow(C_U(f,t), 2)+ pow(C_V(f,t),2) + pow(C_W(f,t),2);n velocity_squared += vsquared * Amag;n d = C_R(f,t);n density += d * Amag;n}nend_f_loop(f,t)nreturn dynamic_component;nafter the PRF_GRSUM() command on these values, I divide with global area values to get the area averaged quantities as shwon in the examples of the manual.nI then add this to the C_P(f,t), however it did not give the correct result. (the one that area averaged results in fluent console is obtained from the results section)nCould you recommend something else, on how can I obtain the total pressure. I require this via udf to print to an external file, because I want to assign this pressure to another inlet with perhaps the F_PROFILE command, after some other calculations.n

[DrAmine]

What about defining a report definition for it and then accessing that report definition elsewhere in UDF?n

[DrAmine]

Moreover the dynamic pressure is calculated for each facet and not as average over all facets. Density is not available on boundary just refer to cell next to the facet.n

[atulsingh92]

The customization manual has one example n 3.8.3, but it gives the following errornc(12):error C2099:initializer is not a constantnhere line 12 is the first declaration ofnint rv = Get_Report_Definition_Values(pressure_outlet, 0, &nrOfvalues, NULL, NULL,NULL);ncould you help, how can I solve this error?nThe example was used as it is, with just the name of the report-definition changed.n

[YasserSelima]

make itint rv;nrv = Get_Report_Definition_Values(pressure_outlet, 0, &nrOfvalues, NULL, NULL,NULL);nn

[YasserSelima]

but is it integer ??n

[atulsingh92]

So, the pressure_outlet report definition is defined so that I could obtain the total pressure at my outlet, after convergence, so no it is not an integer.nhence I tried with the below, and get the errornfloat rv;nn..\..\src\reportdef.c(12): warning C4142: 'rv:benign redefinition of typen..\..\src\reportdef.c(10): note: see declaration of 'rv'n..\..\src\reportdef.c(12): error C2099: initializer is not a constantnnso help is appreciated.n

[YasserSelima]

it seems that you declared it twice ... once as integer and once as floatremove the line nint rv;nhave only the original declaration nfloat rv;nand the line nrv = Get_Report_Definition_Values(pressure_outlet, 0, &nrOfvalues, NULL, NULL,NULL);nn

[atulsingh92]

Thank you for your response, Yasser.nThat is not the case, I have run the example as it is from the 3.8.3 example in fluent customization manual shown as followsnn#include udf.hnn  int nrOfvalues=0;n  real *values;n  int *ids;n  int index;n  int counter;n  float rv;nn  rv = Get_Report_Definition_Values(pressure_outlet, 0, &nrOfvalues, NULL, NULL,NULL);nn  if (rv==0 && nrOfvalues)n{n  Message(Report definition evaluated at iteration has %d values, nrOfvalues);n n  values = (real*) malloc(sizeof(real)* nrOfvalues);n  ids = (int*) malloc(sizeof(int)* nrOfvalues);n n  rv = Get_Report_Definition_Values(pressure_outlet, 0, NULL, values, ids, &index);n n  Message(Values correspond to iteration index:%d, index);n n  for ( counter = 0; counter < nrOfvalues; counter++ )n    {n      Message(report definition values: %d, %f, ids[counter], values[counter]);n    }n  free(values);n  free(ids);nn  elsen{n  if (rv == 1)n    {n      Message(report definition: %s does not exist, pressure_outlet);n    }n  else if ( nrOfvalues == 0 )n    {n      Message(report definition: %s not evaluated at iteration level, pressure_outlet);n    }nThe error is the same.ninitializer is not a constantn

[YasserSelima]

initializer is not a constant means that you declare variable and put it in equation on the same step ... I can not see you doing this in this coden

[atulsingh92]

What about defining a report definition for it and then accessing that report definition elsewhere in UDF?/forum/discussion/comment/107260#Comment_107260

Could you suggest how can I do this?.

[Surya Deb]

Hello, nI think you will need to include this API within the DEFINE_REPORT_DEFINITION_FN UDF. Also keep the int rv = .. definition from the API example. nSomething like this should work. n#include udf.hnDEFINE_REPORT_DEFINITION_FN(UDF_name)n{ n...(include the rest of the API structure here)nn}nGive this a try. nRegards,nSDn