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:

var element = document.getElementById("moose-equation-036e847f-e7f5-49b4-8c60-86c191e3284b");katex.render("F_d = \\int\\limits_S (\\sigma \\vec{n}) \\cdot \\vec{d} ~dS", element, {displayMode:true,throwOnError:false});

where $var element = document.getElementById("moose-equation-2bad58ed-b75f-4876-88ae-47aa5a9d2e97");katex.render("\\sigma", element, {displayMode:false,throwOnError:false});$ 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<<<{"href": "../../syntax/Postprocessors/index.html"}>>>]
  [Re]
    type = ParsedPostprocessor<<<{"description": "Computes a parsed expression with post-processors", "href": "ParsedPostprocessor.html"}>>>
    expression<<<{"description": "function expression"}>>> = 'rho * U * D / mu'
    constant_names<<<{"description": "Vector of constants used in the parsed function (use this for kB etc.)"}>>> = 'rho U D mu'
    constant_expressions<<<{"description": "Vector of values for the constants in constant_names (can be an FParser expression)"}>>> = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius} ${mu}'
  []
  [point_vel_x]
    type = PointValue<<<{"description": "Compute the value of a variable at a specified location", "href": "PointValue.html"}>>>
    point<<<{"description": "The physical point where the solution will be evaluated."}>>> = '${fparse (x_max-x_min)/2} ${fparse (y_max-y_min)/2} 0'
    variable<<<{"description": "The name of the variable that this postprocessor operates on."}>>> = 'vel_x'
  []
  [point_vel_y]
    type = PointValue<<<{"description": "Compute the value of a variable at a specified location", "href": "PointValue.html"}>>>
    point<<<{"description": "The physical point where the solution will be evaluated."}>>> = '${fparse (x_max-x_min)/2} ${fparse (y_max-y_min)/2} 0'
    variable<<<{"description": "The name of the variable that this postprocessor operates on."}>>> = 'vel_y'
  []
  [drag_force]
    type = IntegralDirectedSurfaceForce<<<{"description": "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.", "href": "IntegralDirectedSurfaceForce.html"}>>>
    vel_x<<<{"description": "The velocity in direction x. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = vel_x
    vel_y<<<{"description": "The velocity in direction y. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = vel_y
    mu<<<{"description": "The dynamic viscosity. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = ${mu}
    pressure<<<{"description": "The pressure functor. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = pressure
    principal_direction<<<{"description": "The direction in which the force is computed."}>>> = '1 0 0'
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = 'circle'
    outputs<<<{"description": "Vector of output names where you would like to restrict the output of variables(s) associated with this object"}>>> = none
    execute_on<<<{"description": "The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html."}>>> = 'INITIAL TIMESTEP_END'
  []
  [drag_coeff]
    type = ParsedPostprocessor<<<{"description": "Computes a parsed expression with post-processors", "href": "ParsedPostprocessor.html"}>>>
    expression<<<{"description": "function expression"}>>> = '2*drag_force/rho/(avgvel*avgvel)/D'
    constant_names<<<{"description": "Vector of constants used in the parsed function (use this for kB etc.)"}>>> = 'rho avgvel D'
    constant_expressions<<<{"description": "Vector of values for the constants in constant_names (can be an FParser expression)"}>>> = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius}'
    pp_names<<<{"description": "Post-processors arguments"}>>> = 'drag_force'
    execute_on<<<{"description": "The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html."}>>> = 'INITIAL TIMESTEP_END'
  []
  [lift_force]
    type = IntegralDirectedSurfaceForce<<<{"description": "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.", "href": "IntegralDirectedSurfaceForce.html"}>>>
    vel_x<<<{"description": "The velocity in direction x. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = vel_x
    vel_y<<<{"description": "The velocity in direction y. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = vel_y
    mu<<<{"description": "The dynamic viscosity. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = ${mu}
    pressure<<<{"description": "The pressure functor. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number."}>>> = pressure
    principal_direction<<<{"description": "The direction in which the force is computed."}>>> = '0 1 0'
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = 'circle'
    outputs<<<{"description": "Vector of output names where you would like to restrict the output of variables(s) associated with this object"}>>> = none
    execute_on<<<{"description": "The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html."}>>> = 'INITIAL TIMESTEP_END'
  []
  [lift_coeff]
    type = ParsedPostprocessor<<<{"description": "Computes a parsed expression with post-processors", "href": "ParsedPostprocessor.html"}>>>
    expression<<<{"description": "function expression"}>>> = '2*lift_force/rho/(avgvel*avgvel)/D'
    constant_names<<<{"description": "Vector of constants used in the parsed function (use this for kB etc.)"}>>> = 'rho avgvel D'
    constant_expressions<<<{"description": "Vector of values for the constants in constant_names (can be an FParser expression)"}>>> = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius}'
    pp_names<<<{"description": "Post-processors arguments"}>>> = 'lift_force'
    execute_on<<<{"description": "The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html."}>>> = 'INITIAL TIMESTEP_END'
  []
[]

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. 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 dynamic viscosity. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number.
pressureThe pressure functor. 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 pressure functor. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number.
principal_directionThe direction in which the force is computed.
C++ Type:libMesh::VectorValue<double>
Unit:(no unit assumed)
Controllable:No
Description:The direction in which the force is computed.
vel_xThe velocity in direction x. 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 velocity in direction x. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number.

Required Parameters

vel_yThe velocity in direction y. 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 velocity in direction y. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number.
vel_zThe velocity in direction z. 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 velocity in direction z. A functor is any of the following: a variable, a functor material property, a function, a postprocessor or a number.

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).
execute_onTIMESTEP_ENDThe list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
Default:TIMESTEP_END
C++ Type:ExecFlagEnum
Options:XFEM_MARK, NONE, INITIAL, LINEAR, LINEAR_CONVERGENCE, NONLINEAR, NONLINEAR_CONVERGENCE, POSTCHECK, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, MULTIAPP_FIXED_POINT_CONVERGENCE, FINAL, CUSTOM, TRANSFER
Controllable:No
Description:The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
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

Execution Scheduling 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.
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

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
Unit:(no unit assumed)
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.
use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
Default:False
C++ Type:bool
Controllable:No
Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Material Property Retrieval Parameters

(moose/modules/navier_stokes/examples/flow-over-circle/executioner_postprocessor.i)

[Functions]
  [inlet_function]
    type = ParsedFunction
    expression = '4*U*(y-ymin)*(ymax-y)/(ymax-ymin)/(ymax-ymin)'
    symbol_names = 'U ymax ymin'
    symbol_values = '${inlet_velocity} ${y_max} ${y_min}'
  []
[]

[Executioner]
  type = Transient
  solve_type = 'NEWTON'
  petsc_options = '-snes_converged_reason -ksp_converged_reason'
  petsc_options_iname = '-pc_type'
  petsc_options_value = 'lu'
  line_search = 'none'
  nl_rel_tol = 1e-8
  nl_abs_tol = 1e-10
  nl_max_its = 10
  end_time = 15
  dtmax = 2e-2
  dtmin = 1e-5
  scheme = 'bdf2'
  [TimeStepper]
    type = IterationAdaptiveDT
    dt = 1e-3
    optimal_iterations = 6
    growth_factor = 1.5
  []
[]

[Outputs]
  exodus = true
  csv = true
  checkpoint = true
[]

[Postprocessors]
  [Re]
    type = ParsedPostprocessor
    expression = 'rho * U * D / mu'
    constant_names = 'rho U D mu'
    constant_expressions = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius} ${mu}'
  []
  [point_vel_x]
    type = PointValue
    point = '${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 = ${mu}
    pressure = pressure
    principal_direction = '1 0 0'
    boundary = 'circle'
    outputs = none
    execute_on = 'INITIAL TIMESTEP_END'
  []
  [drag_coeff]
    type = ParsedPostprocessor
    expression = '2*drag_force/rho/(avgvel*avgvel)/D'
    constant_names = 'rho avgvel D'
    constant_expressions = '${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 = ${mu}
    pressure = pressure
    principal_direction = '0 1 0'
    boundary = 'circle'
    outputs = none
    execute_on = 'INITIAL TIMESTEP_END'
  []
  [lift_coeff]
    type = ParsedPostprocessor
    expression = '2*lift_force/rho/(avgvel*avgvel)/D'
    constant_names = 'rho avgvel D'
    constant_expressions = '${rho} ${fparse 2/3*inlet_velocity} ${fparse 2*circle_radius}'
    pp_names = 'lift_force'
    execute_on = 'INITIAL TIMESTEP_END'
  []
[]

Explanation
Example input syntax
Input Parameters

Usage

Development

Demonstration