Results of the boundary integral (B_INT) are not written for each time step

[ktbolt]

Description

The results of the boundary integral (B_INT) are only written for the first time step and not for the remaining time steps.

Reproduction

For a fluids simulation add the following lines to the solver XML file

   <Output type="B_INT" >
     <Pressure> true </Pressure>
   </Output>

The B_NS_Pressure_average.txt file contains only a single set of values

 lumen_inlet  lumen_outlet  lumen_wall
 1.249e+01  1.249e+01  3.766e+02 

Expected behavior

Values should be written for each time step.

Additional context

No response

Code of Conduct

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[ktbolt]

The values in the B_NS_Pressure_average.txt file were actually face areas, values would follow later.

The original code used a std::vector<bool> wtn(3) to implicitly indicate output for spatial[0], boundary[1] or volume[2]. When in the code you are wondering what wtn might mean and see its obscure use like

if (!output.wtn[0]) {

for (int i = 0; i < 2; i++) {
  if (!wtn[i]) {
    continue;
  }

  if (i == 0) {

I've replaced std::vector<bool> wtn(3) with an OutputOptions class encapsulating Booleans for spatial, boundary and volume output types so you can do lEq.output[k].options.boundary_integral = true rather than lEq.output[k].wtn[1] = true.

The code originally computed and wrote both boundary and volume quantities in a single function. I've separated that code into two functions. I've also added a time step and time to the values written. For example: B_NS_Pressure_average.txt file

# svMultiPhysics boundary integral results file. 
# Quantities represent averaged scalar or flux values over each mesh face.
#        
# Format 
# ------ 
# face areas: [list of mesh face areas]  
# step time [list of mesh face names] 
# [time step] [time] [list of computed values for each mesh face]
face areas:  2.957e+00  2.973e+00  4.644e+01 
step   time   lumen_inlet  lumen_outlet  lumen_wall 
 1   5.0000000000e-03  4.6318356113e+02  1.3745997101e+02  3.0236471504e+02 
 2   1.0000000000e-02  -6.7384998121e+01  1.7091915172e+02  4.8689056707e+01