Tutorial 4 - Overlapping Overset Grids

[JezSw]

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[JezSw]

@yslan added as been helping @kzscisoft with general information

[kzscisoft]

• Removed genmap step as not required.
• Mesh definition is identical to periodic hill

void UDF_Setup() {
  auto mesh = nrs->meshV;

  const dfloat A{4.5}, B{3.5}, C{1./6};

  // mesh modification
  for(int i{0}; i < mesh -> Nlocal; ++i) {
    const dfloat argx{B * (std::abs(mesh->x[i] - A) - B)};
    const dfloat A1{C * (1. + std::tanh(argx))};
    mesh->y[i] = mesh->y[i] + A1 * (3. - mesh->y[i]);
  }
}

• userf translated to an array fill.
• Not sure if the statement "Currently, applying a constand mass flux of param(54) and param(55).." still applies:

void userf(double time) {
  const dfloat ffx{0.052};

  // Get x component of non-linear momentum array
  // using offset of 0
  auto o_FUx = nrs->o_NLT + 0 * nrs->fieldOffset;
  platform->linAlg->fill(nrs->meshV->Nlocal, ffx, o_FUx);
}

void UDF_Setup() {
  nrs->userVelocitySource = &userf;
}

• Values in usrdat not yet defined, not sure if these need to be added somewhere yet. Mention of value 2 in original tutorial, likely means setting boundaryEXTOrder in parameter file?
• Initial conditions also defined within UDF_Setup(), I thought maybe these could be defined within __okl__ but the result seems differ, will try this again in future:

void UDF_Setup() {
  // initial conditions
  for(int i{0}; i < mesh -> Nlocal; ++i) {
    nrs->U[i + 0 * nrs->fieldOffset] = 1.0;
    nrs->U[i + 1 * nrs->fieldOffset] = 0.0;
    nrs->U[i + 2 * nrs->fieldOffset] = 0.0;
}

• Conditional boundary conditions require duplication of the UDF file as the boundary index for int (interpolated) boundary is not the same for lower and upper. This is not ideal, I would prefer to have a single UDF file (also note last part of logic for temperature still needs to be addressed):

#ifdef __okl__
void codedFixedValueVelocity(bcData *bc) {
  if(bc->id == 3) {
    bc->u = bc->uinterp;
    bc->v = bc->vinterp;
    bc->w = bc->winterp;
  } else {
    bc->u = 0.0;
    bc->v = 0.0;
    bc->w = 0.0;
  }
}
#endif

• Use two .par files of form:

[GENERAL]
polynomialOrder = 7
stopAt = endTime
endTime  = 200
variableDT = yes
dt = targetCFL = 0.4 + initial=1e-1
timeStepper = bdf2
checkpointControl = steps
checkpointInterval = 20
udf = "hillnn.udf"

[PROBLEMTYPE]
equation = navierstokes

[VELOCITY]
residualTol = 1e-8
density = 1
viscosity = -100

[NEKNEK]
boundaryEXTOrder = 2

[MESH]
file = "upper.re2"

• The SIZE file content has also been overlooked, need to verify this is correct.
• Run using a sesssion file:

lower:1;
upper:1;

$ nrsbmpi hillnn.sess 1

[yslan]

• codeFixedValueVelocity shouldn't touch bc->s. It won't be used.

• I suggest to name re2, par and udf the same name so your can remove the following from par

  udf = "hillnn.udf"
  
  [MESH]
  file = "upper.re2"
  

• This should be 2 based on your sess file

  $ nrsbmpi hillnn.sess 2
  

[kzscisoft]

@yslan I tried with 2 and it threw an error, only seems to run with 1