LinearFVVelocitySymmetryBC

Description

LinearFVVelocitySymmetryBC mirrors the segregated momentum solution at a symmetry plane for linear finite-volume velocity variables. The boundary value is obtained by reflecting the cell-centered velocity across the symmetry normal, removing the normal component while preserving the tangential components. This provides the classical symmetry condition of zero normal velocity together with a zero-gradient tangential velocity, making the operator consistent with the linearised momentum fluxes used by SIMPLE-like algorithms. The implementation is based on the methodology in Greenshields and Weller (2022).

Let denote the cell-center velocity adjacent to the face with unit normal . The boundary condition projects out the normal contribution,

which enforces $ \mathbf{u}_f \cdot \mathbf{n} = 0$ while keeping the tangential velocity from the cell.

The object couples to the momentum component being solved. The parameter "momentum_component" selects which velocity equation the boundary condition contributes to, and the velocity components must be supplied through "u", "v", and "w". Only the velocity components present in the problem dimension are required.

This boundary condition is typically paired with the momentum flux kernel LinearWCNSFVMomentumFlux and LinearFVPressureSymmetryBC on symmetry planes of channel flows, as demonstrated in:

commentnote

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.

[LinearFVBCs<<<{"href": "../../syntax/LinearFVBCs/index.html"}>>>]
  [symmetry-u]
    type = LinearFVVelocitySymmetryBC<<<{"description": "Adds a symmetry boundary condition for the velocity.", "href": "LinearFVVelocitySymmetryBC.html"}>>>
    variable<<<{"description": "The name of the variable that this boundary condition applies to"}>>> = vel_x
    momentum_component<<<{"description": "The component of the momentum equation that this kernel applies to."}>>> = x
    u<<<{"description": "The velocity in the x direction."}>>> = vel_x
    v<<<{"description": "The velocity in the y direction."}>>> = vel_y
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = 'bottom'
  []
[]
(modules/navier_stokes/test/tests/finite_volume/ins/channel-flow/linear-segregated/2d-symmetric/channel.i)

Input Parameters

  • 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

  • momentum_componentThe component of the momentum equation that this kernel applies to.

    C++ Type:MooseEnum

    Options:x, y, z

    Controllable:No

    Description:The component of the momentum equation that this kernel applies to.

  • uThe velocity in the x direction.

    C++ Type:SolverVariableName

    Unit:(no unit assumed)

    Controllable:No

    Description:The velocity in the x direction.

  • 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

  • vThe velocity in the y direction.

    C++ Type:SolverVariableName

    Unit:(no unit assumed)

    Controllable:No

    Description:The velocity in the y direction.

  • wThe velocity in the z direction.

    C++ Type:SolverVariableName

    Unit:(no unit assumed)

    Controllable:No

    Description:The velocity in the z direction.

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_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)

  • 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

Input Files

References

  1. Christopher Greenshields and Henry Weller. Notes on Computational Fluid Dynamics: General Principles. CFD Direct Ltd, Reading, UK, 2022.[BibTeX]