This section is referenced in the following other sections

- Simulation Setup: Heat Flux

# 7.12.2. Heat Flux Boundary Condition On Surface

Scope

  Fuego Region

Summary

  Defines a heat flux boundary condition for heat transfer on a named surface of the mesh.

Description

  From Section Wall Functions; Enthalpy Transport, In practice, the heat flux boundary condition block is to be defined on an already defined wall boundary condition block (without temperature specification). In this manner, multiple boundary conditions are painted on a particular sideset.

  > If one desires to post-process heat flux on a surface, one should remember that post-processed heat flux (both in the log file and Exodus output) is the reconstruction from solution variables and any turbulent wall model that may be specified. As such, the post-processed heat flux is dependent on mesh quality and has been shown to converge to the correct value at a zeroth order rate. Thus, caution should be exercised when evaluating post-processed heat flux values.

    begin Heat Flux Boundary Condition On Surface Surfacename

       External Field For VariableName [{of} Species] {=} ExtFieldName [ Of Size Value With Multiplier {=} Multiplier  ]

       Function For Heat_Flux {=} functionName In The {t | x | y | z} Direction

       Heat_Flux {=} value

       Integer Data For Subroutine SubName {=} Values...

       Postprocess FluxType Flux Of {conserved_enthalpy | continuity | edc_product | enthalpy | mixture_fraction | nuclei | progress_variable | scalar_variance | second_mixture_fraction | solid_volume_fraction | soot | species | temperature | turbulent_dissipation | turbulent_frequency | turbulent_helmholtz_function | turbulent_kinetic_energy | turbulent_v2 | volume_of_fluid | x_momentum | x_solid_momentum | y_momentum | y_solid_momentum | z_momentum | z_solid_momentum} [ As aliases...  ]

       Real Data For Subroutine SubName {=} Values...

       Subroutine For Heat_Flux {=} subroutineName

       Law_Of_Wall_Roughness_Parameter {=} Law of the Wall Roughness parameter

    end Heat Flux Boundary Condition On Surface Surfacename

## 7.12.2.1. Line Commands

###### External Field For

Syntax

  External Field For VariableName [{of} Species] {=} ExtFieldName [ Of Size Value With Multiplier {=} Multiplier ]

Summary

  Name of the field that is to be transferred in. For species equation, specify variable as “mass fraction of” followed by the species name for transfers associated with separated individual species field names.

Parameter | Value | Default
--- | --- | ---
VariableName | string | –
Species | string | –
{=} | {= | are | is} | –
ExtFieldName | string | –

###### Function For Heat_Flux

Syntax

  Function For Heat_Flux {=} functionName In The {t | x | y | z} Direction

Summary

  Name of the function to use for the heat flux in the given direction.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
functionName | string | –
Direction | {t | x | y | z} | –

###### Heat_Flux

Syntax

  Heat_Flux {=} value

Summary

  Constant value for the heat flux through the surface.

Description

  This value is positive for heat into the surface.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
value | “string” | –

###### Integer Data For Subroutine

Syntax

  Integer Data For Subroutine SubName {=} Values…

Summary

  List of integer data values to be passed down in to the user subroutine. These values may be changed by the user subroutine.

Parameter | Value | Default
--- | --- | ---
SubName | string | –
{=} | {= | are | is} | –
Values | integer… | –

###### Postprocess

Syntax

  Postprocess FluxType Flux Of {conserved_enthalpy | continuity | edc_product | enthalpy | mixture_fraction | nuclei | progress_variable | scalar_variance | second_mixture_fraction | solid_volume_fraction | soot | species | temperature | turbulent_dissipation | turbulent_frequency | turbulent_helmholtz_function | turbulent_kinetic_energy | turbulent_v2 | volume_of_fluid | x_momentum | x_solid_momentum | y_momentum | y_solid_momentum | z_momentum | z_solid_momentum} [ As aliases… ]

Summary

  Enable nodal flux post-processing for a given equation. Flux types can be “total”, “advective”, or “diffusive”. Integrated fluxes will also be output to global variables for post-processing or use in other string functions.

  By default the variables will be named based on the equation and sideset they are applied to as bc_FluxType_EquationName_flux_SurfaceName. However, if you want to assign a more compact or descriptive name you can provide it with

      POSTPROCESS TOTAL FLUX OF Continuity AS mdot1

  When post-processing enthalpy, the average temperature is also output as a global variable. If you provide only one alias the enthalpy flux uses your alias and the average temperature is automatically named. If you provide two aliases the first is used for enthalpy and the second is used for temperature.

      POSTPROCESS TOTAL FLUX OF ENTHALPY AS hFlux
      POSTPROCESS TOTAL FLUX OF ENTHALPY AS hFlux Tavg

  When post-processing species, the post-processor is run for each species that is solved for. This means that there is no post-processor run on the last species (which is determined by a fractional balance). If you provide aliases for the species post-processor you should provide one for each post-processed species. For example, in a problem with O2, CO2, and N2 (in that order) you could use:

      POSTPROCESS TOTAL FLUX OF SPECIES AS mdotO2 mdotCO2

Parameter | Value | Default
--- | --- | ---
FluxType | string | –
equation | {conserved_enthalpy | continuity | edc_product | enthalpy | mixture_fraction | nuclei | progress_variable | scalar_variance | second_mixture_fraction | solid_volume_fraction | soot | species | temperature | turbulent_dissipation | turbulent_frequency | turbulent_helmholtz_function | turbulent_kinetic_energy | turbulent_v2 | volume_of_fluid | x_momentum | x_solid_momentum | y_momentum | y_solid_momentum | z_momentum | z_solid_momentum} | –

###### Real Data For Subroutine

Syntax

  Real Data For Subroutine SubName {=} Values…

Summary

  List of real data values to be passed down in to the user subroutine. These values may be changed by the user subroutine.

Parameter | Value | Default
--- | --- | ---
SubName | string | –
{=} | {= | are | is} | –
Values | real… | –

###### Subroutine For Heat_Flux

Syntax

  Subroutine For Heat_Flux {=} subroutineName

Summary

  Name of the subroutine to use for the heat flux.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
subroutineName | string | –

###### Law_Of_Wall_Roughness_Parameter

Syntax

  Law_Of_Wall_Roughness_Parameter {=} Law of the Wall Roughness parameter

Summary

  Specify dimensionless roughness factor to be used in the law-of-the-wall formulation.

Parameter | Value | Default
--- | --- | ---
{=} | {= | are | is} | –
Law of the Wall Roughness parameter | real | 9.8