Address Peter's reviews- tests and doc #28951

framework/doc/content/source/linearfvkernels/LinearFVEnergyAdvection.md

@@ -2,15 +2,15 @@
 
 This kernel adds the contributions of the energy advection term to the matrix and right hand side of the energy equation system for the finite volume SIMPLE segregated solver [SIMPLE.md].
 
-This term is described by $\nabla \cdot \left(\rho\vec{u} c_p T \right)$ present in the energy equation conservation for an incompressible/weakly-compressible formulation. Currently, the kernel only supports constant specific heat values for $c_p$ and solves for a temperature variable. The specific heat value needs to be prescribed, otherwise it will default to its default value of $c_p=1$.
+This term is described by $\nabla \cdot \left(\rho\vec{u} c_p T \right)$ present in the energy equation conservation for an incompressible/weakly-compressible formulation. Currently, the kernel only supports +constant specific heat values+ for $c_p$ and solves for a temperature variable. The specific heat value needs to be prescribed, otherwise it will default to its default value of $c_p=1$.
 
 For FV, the integral of the advection term over a cell can be expressed as:
 
 \begin{equation}
 \int\limits_{V_C} \nabla \cdot \left(\rho\vec{u} c_p T \right) dV \approx \sum\limits_f (\rho \vec{u}\cdot \vec{n})_{RC} c_p T_f |S_f| \,
 \end{equation}
 
-where $T_f$ is a face temperature. The temperature acts as the advected quantity and an interpolation scheme (e.g. upwind) can be used to copmute the face value. This kernel adds the face contribution for each face $f$ to the right hand side and matrix.
+where $T_f$ is a face temperature. The temperature acts as the advected quantity and an interpolation scheme (e.g. upwind) can be used to compute the face value. This kernel adds the face contribution for each face $f$ to the right hand side and matrix.
 
 The face mass flux $(\rho \vec{u}\cdot \vec{n})_{RC}$ is provided by the [RhieChowMassFlux.md] object which uses pressure
 gradients and the discrete momentum equation to compute face velocities and mass fluxes.

framework/include/linearfvkernels/LinearFVSource.h

@@ -35,5 +35,5 @@ class LinearFVSource : public LinearFVElementalKernel
   const Moose::Functor<Real> & _source_density;
 
   /// Scale factor
-  const Real & _scale;
+  const Real _scale;
 };

modules/navier_stokes/doc/content/source/linearfvkernels/LinearFVMomentumBoussinesq.md

@@ -1,6 +1,6 @@
 # LinearFVMomentumBoussinesq
 
-This kernel adds the contributions of the Boussinesq buoyancy treatment for density through a force/source term to the right hand side of the momentum equation system for the finite volume SIMPLE segregated solver [SIMPLE.md].
+This kernel adds the contributions of the Boussinesq buoyancy treatment for density through a force/source term to the right hand side of the momentum equation system for the finite volume SIMPLE segregated solver [SIMPLE.md]. The Boussinesq buoyancy treatment is applicable for low changes in density, and assumes constant density value in all other equation terms.
 
 This term is described by $-\rho_{ref}\alpha\vec{g}(T - T_{ref})$ present in the momentum equation conservation when describing an incompressible fluid, where $\rho_{ref}$ is the reference density, $\alpha$ is the thermal expansion coefficient, $\vec{g}$ is the gravity vector, $T$ is the temperature, and $T_{ref}$ is a reference temperature. The Boussinesq buoyancy model assumes the changes in density as a function of temperature are linear and relevant only in the buoyant force term of the equation system. The Boussinesq kernel allows for modeling natural convection.
 

modules/navier_stokes/include/linearfvkernels/LinearFVMomentumBoussinesq.h

@@ -32,17 +32,17 @@ class LinearFVMomentumBoussinesq : public LinearFVElementalKernel
 
 protected:
   /// Fluid Temperature
-  MooseLinearVariableFV<Real> & getTemperatureVariable(const std::string & vname);
+  const MooseLinearVariableFV<Real> & getTemperatureVariable(const std::string & vname);
 
   /// Index x|y|z of the momentum equation component
   const unsigned int _index;
   /// Pointer to the linear finite volume temperature variable
-  MooseLinearVariableFV<Real> & _temperature_var;
+  const MooseLinearVariableFV<Real> & _temperature_var;
   /// The gravity vector
   const RealVectorValue _gravity;
   /// The thermal expansion coefficient
   const Moose::Functor<Real> & _alpha;
-  /// Reference temperature at which the value of _rho was measured
+  /// Reference temperature at which the reference value of the density (_rho) was measured
   const Real _ref_temperature;
   /// the density
   const Moose::Functor<Real> & _rho;

modules/navier_stokes/src/executioners/SIMPLE.C

@@ -443,7 +443,6 @@ SIMPLE::execute()
                                                            _energy_equation_relaxation,
                                                            _energy_linear_control,
                                                            _energy_l_abs_tol);
-
       }
       _problem.execute(EXEC_NONLINEAR);
       // Printing residuals

modules/navier_stokes/src/linearfvkernels/LinearFVMomentumBoussinesq.C

@@ -46,12 +46,11 @@ LinearFVMomentumBoussinesq::LinearFVMomentumBoussinesq(const InputParameters & p
     _ref_temperature(getParam<Real>("ref_temperature")),
     _rho(getFunctor<Real>(NS::density))
 {
-  _temperature_var.computeCellGradients();
   if (!_rho.isConstant())
     paramError(NS::density, "The density in the boussinesq term is not constant!");
 }
 
-MooseLinearVariableFV<Real> &
+const MooseLinearVariableFV<Real> &
 LinearFVMomentumBoussinesq::getTemperatureVariable(const std::string & vname)
 {
   auto * ptr = dynamic_cast<MooseLinearVariableFV<Real> *>(

modules/navier_stokes/test/tests/finite_volume/ins/channel-flow/linear-segregated/2d/2d-boussinesq.i

@@ -9,10 +9,10 @@ alpha_b = 1e-4
   [mesh]
     type = CartesianMeshGenerator
     dim = 2
-    dx = '1.5'
-    dy = '0.3'
-    ix = '55'
-    iy = '20'
+    dx = '1.'
+    dy = '0.2'
+    ix = '10'
+    iy = '5'
   []
 []
 

modules/navier_stokes/test/tests/finite_volume/ins/natural_convection/diff_heated_cavity_linear_segregated.i → modules/navier_stokes/test/tests/finite_volume/ins/natural_convection/linear_segregated/2d/diff_heated_cavity_linear_segregated.i

@@ -34,8 +34,8 @@ walls = 'right left top bottom'
     xmax = 1
     ymin = 0
     ymax = 1
-    nx = 40
-    ny = 40
+    nx = 30
+    ny = 30
   []
 []
 

modules/navier_stokes/test/tests/finite_volume/ins/natural_convection/linear_segregated/2d/tests

@@ -0,0 +1,10 @@
+[Tests]
+  design = 'LinearFVEnergyAdvection.md LinearFVMomentumBoussinesq.md'
+  issues = '#28951'
+  [diff_heated_cavity_linear_segregated]
+    type = 'Exodiff'
+    input = 'diff_heated_cavity_linear_segregated.i'
+    exodiff = 'diff_heated_cavity_linear_segregated_out.e'
+    requirement = 'The system shall be able to use the density Boussinesq approximation to solve for a differentially heated 2D cavity.'
+  []
+[]

modules/navier_stokes/test/tests/finite_volume/ins/natural_convection/tests

@@ -17,7 +17,7 @@
   []
   [diff_heated_cavity_linear_segregated]
     type = 'Exodiff'
-    input = 'diff_heated_cavity_linear_segregated.i'
+    input = 'linear_segregated/diff_heated_cavity_linear_segregated.i'
     exodiff = 'diff_heated_cavity_linear_segregated_out.e'
     requirement = 'The system shall be able to use the density Boussinesq approximation to solve for a differentially heated 2D cavity.'
   []