Allow skipping a chosen interval in JouleHeatingAux

include/auxkernels/JouleHeatingAux.h

@@ -18,6 +18,9 @@ class JouleHeatingAux : public AuxKernel
   /// The electrical conductivity
   const Real _sigma;
 
+  /// Time interval after which the kernel starts computing
+  const Real _skip;
+
   /// Whether to take the time average
   const bool _avg;
 };

src/auxkernels/JouleHeatingAux.C

@@ -7,9 +7,13 @@ JouleHeatingAux::validParams()
 {
   InputParameters params = AuxKernel::validParams();
   params.addClassDescription("Computes (optionally, the time average of) the differential form of "
-                             "the Joule heating equation (power per unit volume).");
+                             "the Joule heating equation (power per unit volume). "
+                             "The user may specify a time interval only after which the kernel "
+                             "starts computing. If computing the time average, the right endpoint "
+                             "rectangle rule is used for integration.");
   params.addCoupledVar("vector_potential", "The vector potential variable");
   params.addParam<Real>("sigma", 1, "The electrical conductivity");
+  params.addParam<Real>("skip", 0, "Time interval after which the kernel starts computing");
   params.addParam<bool>("average", true, "Whether to take the time average");
   return params;
 }
@@ -18,13 +22,15 @@ JouleHeatingAux::JouleHeatingAux(const InputParameters & parameters)
   : AuxKernel(parameters),
     _electric_field(coupledVectorDot("vector_potential")),
     _sigma(getParam<Real>("sigma")),
+    _skip(getParam<Real>("skip")),
     _avg(getParam<bool>("average"))
 {
 }
 
 Real
 JouleHeatingAux::computeValue()
 {
-  Real beta = _avg ? _dt / _t : 1;
-  return (1 - beta) * _u[_qp] + (beta * _sigma * _electric_field[_qp] * _electric_field[_qp]);
+  Real p = _sigma * _electric_field[_qp] * _electric_field[_qp];
+  Real w = _t > _skip ? _avg ? _dt / (_t - _skip) : 1 : 0;
+  return (1 - w) * _u[_qp] + w * p;
 }