LinearFVPressureSymmetryBC

Description

LinearFVPressureSymmetryBC enforces a symmetry constraint for the pressure correction equation in segregated linear finite-volume Navier-Stokes solves. It sets the face pressure equal to the adjacent cell value, yielding a zero normal gradient while respecting the Rhie-Chow coupling between pressure and velocity.

For a boundary face with unit normal $var element = document.getElementById("moose-equation-f11db69f-9715-4225-8ccc-80325b8f0fbf");katex.render("\\mathbf{n}", element, {displayMode:false,throwOnError:false});$ , the pressure degrees of freedom satisfy

$var element = document.getElementById("moose-equation-0689be5d-f05d-4f76-b836-5e2df13af818");katex.render("p_f = p_P, \\qquad \\frac{\\partial p}{\\partial n}\\biggr\\rvert_f = 0,", element, {displayMode:true,throwOnError:false});$

note

The current approximation of the face value assumes that the face centroid is close to the point where the line from the cell center in the normal direction intersects the face. This means that on unstructured meshes, this results a spatially first-order discretization.

and the residual contribution stemming from the Rhie-Chow momentum-flux correction is

$var element = document.getElementById("moose-equation-d4af68ca-0aa9-4ead-8145-d475b26ea172");katex.render("R_f = -\\left(A^{-1} H\\right)_f \\cdot \\vec{n}_f,", element, {displayMode:true,throwOnError:false});$

where $var element = document.getElementById("moose-equation-bf572b96-708a-4d59-ba40-9a3cf9d82031");katex.render("A^{-1} H", element, {displayMode:false,throwOnError:false});$ is provided through RhieChowMassFlux to provide the "HbyA_flux" functor. This flux is used to populate the right-hand side contribution so that the pressure gradient remains consistent with the momentum equation discretisation on symmetry planes.

An example of this boundary condition applied alongside the velocity symmetry condition for a channel flow is shown in:

[LinearFVBCs<<<{"href": "../../syntax/LinearFVBCs/index.html"}>>>]
  [symmetry-p]
    type = LinearFVPressureSymmetryBC<<<{"description": "Adds a symmetry boundary condition for pressure in a segregated velocity and pressure solve.", "href": "LinearFVPressureSymmetryBC.html"}>>>
    variable<<<{"description": "The name of the variable that this boundary condition applies to"}>>> = pressure
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = 'bottom'
    HbyA_flux<<<{"description": "The total HbyA face flux value. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = 'HbyA' # Functor created in the RhieChowMassFlux UO
  []
[]

Input Parameters

HbyA_fluxThe total HbyA face flux value. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number.
C++ Type:MooseFunctorName
Unit:(no unit assumed)
Controllable:No
Description:The total HbyA face flux value. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number.
boundaryThe list of boundary IDs from the mesh where this object applies
C++ Type:std::vector<BoundaryName>
Controllable:No
Description:The list of boundary IDs from the mesh where this object applies
variableThe name of the variable that this boundary condition applies to
C++ Type:LinearVariableName
Unit:(no unit assumed)
Controllable:No
Description:The name of the variable that this boundary condition applies to

Required Parameters

matrix_onlyFalseWhether this object is only doing assembly to matrices (no vectors)
Default:False
C++ Type:bool
Controllable:No
Description:Whether this object is only doing assembly to matrices (no vectors)

Optional Parameters

absolute_value_vector_tagsThe tags for the vectors this residual object should fill with the absolute value of the residual contribution
C++ Type:std::vector<TagName>
Controllable:No
Description:The tags for the vectors this residual object should fill with the absolute value of the residual contribution
extra_matrix_tagsThe extra tags for the matrices this Kernel should fill
C++ Type:std::vector<TagName>
Controllable:No
Description:The extra tags for the matrices this Kernel should fill
extra_vector_tagsThe extra tags for the vectors this Kernel should fill
C++ Type:std::vector<TagName>
Controllable:No
Description:The extra tags for the vectors this Kernel should fill
matrix_tagssystemThe tag for the matrices this Kernel should fill
Default:system
C++ Type:MultiMooseEnum
Options:nontime, system
Controllable:No
Description:The tag for the matrices this Kernel should fill
vector_tagsrhsThe tag for the vectors this Kernel should fill
Default:rhs
C++ Type:MultiMooseEnum
Options:rhs, time
Controllable:No
Description:The tag for the vectors this Kernel should fill

Contribution To Tagged Field Data Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Controllable:Yes
Description:Set the enabled status of the MooseObject.
implicitTrueDetermines whether this object is calculated using an implicit or explicit form
Default:True
C++ Type:bool
Controllable:No
Description:Determines whether this object is calculated using an implicit or explicit form
search_methodnearest_node_connected_sidesChoice of search algorithm. All options begin by finding the nearest node in the primary boundary to a query point in the secondary boundary. In the default nearest_node_connected_sides algorithm, primary boundary elements are searched iff that nearest node is one of their nodes. This is fast to determine via a pregenerated node-to-elem map and is robust on conforming meshes. In the optional all_proximate_sides algorithm, primary boundary elements are searched iff they touch that nearest node, even if they are not topologically connected to it. This is more CPU-intensive but is necessary for robustness on any boundary surfaces which has disconnections (such as Flex IGA meshes) or non-conformity (such as hanging nodes in adaptively h-refined meshes).
Default:nearest_node_connected_sides
C++ Type:MooseEnum
Options:nearest_node_connected_sides, all_proximate_sides
Controllable:No
Description:Choice of search algorithm. All options begin by finding the nearest node in the primary boundary to a query point in the secondary boundary. In the default nearest_node_connected_sides algorithm, primary boundary elements are searched iff that nearest node is one of their nodes. This is fast to determine via a pregenerated node-to-elem map and is robust on conforming meshes. In the optional all_proximate_sides algorithm, primary boundary elements are searched iff they touch that nearest node, even if they are not topologically connected to it. This is more CPU-intensive but is necessary for robustness on any boundary surfaces which has disconnections (such as Flex IGA meshes) or non-conformity (such as hanging nodes in adaptively h-refined meshes).

Advanced Parameters

(moose/modules/navier_stokes/test/tests/finite_volume/ins/channel-flow/linear-segregated/2d-symmetric/channel.i)

mu = 2.6
rho = 1.2
advected_interp_method = 'upwind'
u_inlet = 1.1
half_width = 0.2

[Mesh]
  [mesh]
    type = CartesianMeshGenerator
    dim = 2
    dx = '1.0'
    dy = '${half_width}'
    ix = '30'
    iy = '15'
    subdomain_id = '0'
  []
  allow_renumbering = false
[]

[Problem]
  linear_sys_names = 'u_system v_system pressure_system'
  previous_nl_solution_required = true
[]

[UserObjects]
  [rc]
    type = RhieChowMassFlux
    u = vel_x
    v = vel_y
    pressure = pressure
    rho = ${rho}
    p_diffusion_kernel = p_diffusion
  []
[]

[Variables]
  [vel_x]
    type = MooseLinearVariableFVReal
    initial_condition = 0.5
    solver_sys = u_system
  []
  [vel_y]
    type = MooseLinearVariableFVReal
    solver_sys = v_system
    initial_condition = 0.0
  []
  [pressure]
    type = MooseLinearVariableFVReal
    solver_sys = pressure_system
    initial_condition = 0.2
  []
[]

[LinearFVKernels]
  [u_advection_stress]
    type = LinearWCNSFVMomentumFlux
    variable = vel_x
    advected_interp_method = ${advected_interp_method}
    mu = ${mu}
    u = vel_x
    v = vel_y
    momentum_component = 'x'
    rhie_chow_user_object = 'rc'
    use_nonorthogonal_correction = false
  []
  [v_advection_stress]
    type = LinearWCNSFVMomentumFlux
    variable = vel_y
    advected_interp_method = ${advected_interp_method}
    mu = ${mu}
    u = vel_x
    v = vel_y
    momentum_component = 'y'
    rhie_chow_user_object = 'rc'
    use_nonorthogonal_correction = false
  []
  [u_pressure]
    type = LinearFVMomentumPressure
    variable = vel_x
    pressure = pressure
    momentum_component = 'x'
  []
  [v_pressure]
    type = LinearFVMomentumPressure
    variable = vel_y
    pressure = pressure
    momentum_component = 'y'
  []

  [p_diffusion]
    type = LinearFVAnisotropicDiffusion
    variable = pressure
    diffusion_tensor = Ainv
    use_nonorthogonal_correction = false
  []
  [HbyA_divergence]
    type = LinearFVDivergence
    variable = pressure
    face_flux = HbyA
    force_boundary_execution = true
  []
[]

[LinearFVBCs]
  [inlet-u]
    type = LinearFVAdvectionDiffusionFunctorDirichletBC
    boundary = 'left'
    variable = vel_x
    functor = ${u_inlet}
  []
  [inlet-v]
    type = LinearFVAdvectionDiffusionFunctorDirichletBC
    boundary = 'left'
    variable = vel_y
    functor = '0.0'
  []
  [walls-u]
    type = LinearFVAdvectionDiffusionFunctorDirichletBC
    boundary = 'top'
    variable = vel_x
    functor = 0.0
  []
  [walls-v]
    type = LinearFVAdvectionDiffusionFunctorDirichletBC
    boundary = 'top'
    variable = vel_y
    functor = 0.0
  []
  [symmetry-u]
    type = LinearFVVelocitySymmetryBC
    variable = vel_x
    momentum_component = x
    u = vel_x
    v = vel_y
    boundary = 'bottom'
  []
  [symmetry-v]
    type = LinearFVVelocitySymmetryBC
    variable = vel_y
    momentum_component = y
    u = vel_x
    v = vel_y
    boundary = 'bottom'
  []
  [outlet_u]
    type = LinearFVAdvectionDiffusionOutflowBC
    variable = vel_x
    use_two_term_expansion = false
    boundary = 'right'
  []
  [outlet_v]
    type = LinearFVAdvectionDiffusionOutflowBC
    variable = vel_y
    use_two_term_expansion = false
    boundary = 'right'
  []
  [outlet_p]
    type = LinearFVAdvectionDiffusionFunctorDirichletBC
    boundary = 'right'
    variable = pressure
    functor = 1.4
  []
  [pressure-extrapolation]
    type = LinearFVExtrapolatedPressureBC
    boundary = 'top left'
    variable = pressure
    use_two_term_expansion = true
  []
  [symmetry-p]
    type = LinearFVPressureSymmetryBC
    variable = pressure
    boundary = 'bottom'
    HbyA_flux = 'HbyA' # Functor created in the RhieChowMassFlux UO
  []
[]

[Functions]
  [u_parabolic_profile]
    type = ParsedFunction
    value = '3/2*${u_inlet}*(1 - pow(y/${half_width}, 2))' # Poiseuille profile
  []
  [u_parabolic_profile_rz]
    type = ParsedFunction
    value = '2*${u_inlet}*(1 - pow(y/${half_width}, 2))' # Cylindrical profile
  []
[]

[AuxVariables]
  [vel_exact]
    type = MooseLinearVariableFVReal
  []
[]

[AuxKernels]
  [assign_vel_exact]
    type = FunctionAux
    variable = vel_exact
    function = u_parabolic_profile
    execute_on = TIMESTEP_END
  []
[]

[VectorPostprocessors]
  [outlet_velocity_profile]
    type = SideValueSampler
    variable = 'vel_x vel_exact'
    boundary = 'right'
    sort_by = 'y'
    execute_on = TIMESTEP_END
  []
[]

[Executioner]
  type = SIMPLE
  momentum_l_abs_tol = 1e-12
  pressure_l_abs_tol = 1e-12
  momentum_l_tol = 0
  pressure_l_tol = 0
  rhie_chow_user_object = 'rc'
  momentum_systems = 'u_system v_system'
  pressure_system = 'pressure_system'
  momentum_equation_relaxation = 0.5
  pressure_variable_relaxation = 0.3
  num_iterations = 1000
  pressure_absolute_tolerance = 1e-10
  momentum_absolute_tolerance = 1e-10
  momentum_petsc_options_iname = '-pc_type -pc_hypre_type'
  momentum_petsc_options_value = 'hypre boomeramg'
  pressure_petsc_options_iname = '-pc_type -pc_hypre_type'
  pressure_petsc_options_value = 'hypre boomeramg'
  print_fields = false
  continue_on_max_its = true
[]

[Outputs]
  csv = true
  execute_on = timestep_end
[]

Description
Input Parameters