IntegralDirectedSurfaceForce

Computes the directed force coming from friction and pressure differences on a surface. One can use this object for the computation of the drag and lift coefficient as well.

Explanation

This postprocessor which computes the directed force coming from friction and pressure differences on a surface defined as:

where is the Cauchy stress tensor. One can use this in combination with other postprocessors to compute representative drag and lift coefficients.

Example input syntax

In this case, the lift and drag coefficients are computed on the surface of a cylinder.

[Postprocessors]
  [Re]
    type = ParsedPostprocessor
    function = 'rho * U * D / mu'
    constant_names = 'rho U D mu'
    constant_expressions = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius} ${mu}'
    pp_names = ''
  []
  [point_vel_x]
    type = PointValue
    point = '${fparse (x_max-x_min)/2} ${fparse (y_max-y_min)/2} 0'
    variable = 'vel_x'
  []
  [point_vel_y]
    type = PointValue
    point = '${fparse (x_max-x_min)/2} ${fparse (y_max-y_min)/2} 0'
    variable = 'vel_y'
  []
  [drag_force]
    type = IntegralDirectedSurfaceForce
    vel_x = vel_x
    vel_y = vel_y
    mu = ${mu}
    pressure = pressure
    principal_direction = '1 0 0'
    boundary = 'circle'
    outputs = none
    execute_on = 'INITIAL TIMESTEP_END'
  []
  [drag_coeff]
    type = ParsedPostprocessor
    function = '2*drag_force/rho/(avgvel*avgvel)/D'
    constant_names = 'rho avgvel D'
    constant_expressions = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius}'
    pp_names = 'drag_force'
    execute_on = 'INITIAL TIMESTEP_END'
  []
  [lift_force]
    type = IntegralDirectedSurfaceForce
    vel_x = vel_x
    vel_y = vel_y
    mu = ${mu}
    pressure = pressure
    principal_direction = '0 1 0'
    boundary = 'circle'
    outputs = none
    execute_on = 'INITIAL TIMESTEP_END'
  []
  [lift_coeff]
    type = ParsedPostprocessor
    function = '2*lift_force/rho/(avgvel*avgvel)/D'
    constant_names = 'rho avgvel D'
    constant_expressions = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius}'
    pp_names = 'lift_force'
    execute_on = 'INITIAL TIMESTEP_END'
  []
[]
(moose/modules/navier_stokes/examples/flow-over-circle/executioner_postprocessor.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

  • muThe dynamic viscosity.

    C++ Type:MooseFunctorName

    Controllable:No

    Description:The dynamic viscosity.

  • pressureThe pressure functor.

    C++ Type:MooseFunctorName

    Controllable:No

    Description:The pressure functor.

  • principal_directionThe direction in which the force is computed.

    C++ Type:libMesh::VectorValue<double>

    Controllable:No

    Description:The direction in which the force is computed.

  • vel_xThe velocity in direction x.

    C++ Type:MooseFunctorName

    Controllable:No

    Description:The velocity in direction x.

Required Parameters

  • execute_onTIMESTEP_ENDThe list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, FINAL, CUSTOM, ALWAYS.

    Default:TIMESTEP_END

    C++ Type:ExecFlagEnum

    Options:NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, FINAL, CUSTOM, ALWAYS, TRANSFER

    Controllable:No

    Description:The list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, FINAL, CUSTOM, ALWAYS.

  • prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

    C++ Type:MaterialPropertyName

    Controllable:No

    Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

  • vel_yThe velocity in direction y.

    C++ Type:MooseFunctorName

    Controllable:No

    Description:The velocity in direction y.

  • vel_zThe velocity in direction z.

    C++ Type:MooseFunctorName

    Controllable:No

    Description:The velocity in direction z.

Optional Parameters

  • allow_duplicate_execution_on_initialFalseIn the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).

    Default:False

    C++ Type:bool

    Controllable:No

    Description:In the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).

  • 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.

  • execution_order_group0Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.

    Default:0

    C++ Type:int

    Controllable:No

    Description:Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.

  • force_postauxFalseForces the UserObject to be executed in POSTAUX

    Default:False

    C++ Type:bool

    Controllable:No

    Description:Forces the UserObject to be executed in POSTAUX

  • force_preauxFalseForces the UserObject to be executed in PREAUX

    Default:False

    C++ Type:bool

    Controllable:No

    Description:Forces the UserObject to be executed in PREAUX

  • force_preicFalseForces the UserObject to be executed in PREIC during initial setup

    Default:False

    C++ Type:bool

    Controllable:No

    Description:Forces the UserObject to be executed in PREIC during initial setup

  • outputsVector of output names where you would like to restrict the output of variables(s) associated with this object

    C++ Type:std::vector<OutputName>

    Controllable:No

    Description:Vector of output names where you would like to restrict the output of variables(s) associated with this object

  • use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

    Default:False

    C++ Type:bool

    Controllable:No

    Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Advanced Parameters