33.7.19 Wall Dialog Box

The Wall dialog box sets the boundary conditions for a wall zone. It is opened from the Boundary Conditions task page. See Section  7.3.14 for details about defining the items below.

Controls

Zone Name   sets the name of the zone.

Phase   displays the name of the phase. This item appears if the VOF, mixture, or Eulerian multiphase model is being used.

Adjacent Cell Zone   shows the name of the cell zone adjacent to the wall. (This is for informational use only; you cannot edit this field.)

Momentum   displays the momentum boundary conditions.

Wall Motion   contains options for specifying whether or not the wall is moving.

Stationary Wall   specifies that the wall is not moving relative to the adjacent cell zone.

Moving Wall   enables specification of the tangential wall motion. Tangential wall motion is applicable only to viscous flows. Since the inviscid slip condition decouples the tangential wall velocity from the governing equations, tangential wall motion has no effect on inviscid flow.

Motion   contains inputs related to wall motion. See Section  7.3.14 for details.

Relative to Adjacent Cell Zone   enables the specification of a wall velocity relative to the velocity of the adjacent cell zone. (If the adjacent cell zone is not moving, this is equivalent to Absolute.)

Absolute   enables the specification of an absolute wall velocity,

Translational   enables the specification of a translational wall velocity.

Rotational   enables the specification of a rotational wall velocity.

Components   enables the specification of wall velocity components.

Speed   sets the translational or rotational speed of the wall (depending on whether you selected Translational or Rotational).

Direction   sets the direction vector of the translational velocity. (This item will appear if you have chosen the Translational option.)

Rotation-Axis Origin   sets the coordinates of the origin of the axis of rotation, thereby determining the location of the axis. (This item will appear if you have chosen the Rotational option for a non-axisymmetric case.)

Rotation-Axis Direction   sets the direction vector for the axis of rotation. (This item will appear if you have chosen the Rotational option for a non-axisymmetric case.)

Velocity Components   sets the X, Y, and Z-Velocity components of the wall motion. (This item will appear if you have chosen the Components option.)

Shear Condition   contains options for specifying the shear conditions at the wall.

No Slip   specifies a no-slip condition at the wall. No further inputs are required.

Specified Shear   enables specification of zero or non-zero shear. See Section  7.3.14 for details. This option is not available for moving walls.

Marangoni Stress   enables the specification of shear stress caused by the variation of surface tension due to temperature. This option is not available for moving walls.

Shear Stress   contains inputs related to wall shear. These items will appear when Specified Shear is selected as the Shear Condition. See Section  7.3.14 for details.

X-Component, Y-Component, Z-Component, Swirl Component   specify the $x$, $y$, and $z$ or swirl components of shear for a slip wall. Swirl Component is available only for axisymmetric swirl cases.

Specularity Coefficient   is used in multiphase granular flow. You can specify the specularity coefficient such that when the value is zero, this condition is equivalent to zero shear at the wall, but when the value is near unity, there is a significant amount of lateral momentum transfer.

Specularity Coefficient   allows you to enter a value between zero and one, which controls the amount of lateral momentum transfer.

Marangoni Stress   contains inputs related to Marangoni stress. This item will appear when Marangoni Stress is selected as the Shear Condition. See Section  7.3.14 for details.

Surface Tension Gradient   specifies the surface tension gradient with respect to temperature ( $d \sigma/dT$ in Equation  7.3-40).

Wall Roughness   contains inputs for defining wall roughness in turbulent calculations. See Section  7.3.14 for details.

Roughness Height   sets the roughness height $K_s$ (see Section  7.3.14 for details).

Roughness Constant   sets the roughness constant $C_{K_s}$ (see Section  7.3.14 for details).

Wall Adhesion   contains inputs related to wall adhesion. This section of the dialog box will appear if you are using the VOF model and have enabled wall adhesion in the Phase Interaction dialog box.

Contact Angles   specifies the contact angle at the wall for each pair of phases ( $\theta_w$ in this figure in the separate Theory Guide). See Section  24.2.9 for details.

Thermal   contains the thermal parameters. This tab is available only when the energy equation is turned on.

Thermal Conditions   contains radio buttons for selecting the thermal boundary condition type. See Section  7.3.14 for details about these inputs:

Heat Flux   selects a specified heat flux condition.

Temperature   selects a specified wall temperature condition.

Convection   selects a convective heat transfer boundary condition model.

Radiation   selects an external radiation boundary condition.

Mixed   selects a combined convection/external radiation boundary condition.

Coupled   selects a coupled heat transfer condition. It is applicable only to walls that form the interface between two regions (such as the fluid/solid interface for a conjugate heat transfer problem).

Once a condition type has been selected, the appropriate conditions can be specified.

Heat Flux   sets the wall heat flux to be used for the Heat Flux condition. A specification of zero Heat Flux is simply the adiabatic condition (no heat transfer). A positive value of heat flux implies that heat is input into the domain.

Temperature   sets the wall temperature to be used for the Temperature condition.

Heat Transfer Coefficient   sets the convective heat transfer coefficient to be used for the Convection condition ( $h_{\rm eff}$ in Equation  7.3-51).

Free Stream Temperature   sets the reference or free stream temperature to be used for the Convection condition ( $T_{\rm ext}$ in Equation  7.3-51).

External Emissivity   sets the emissivity of the external wall to be used for the Radiation condition ( $\epsilon_{\rm ext}$ in Equation  7.3-52).

External Radiation Temperature   sets the temperature of the external radiation source/sink to be used for the Radiation condition ( $T_\infty$ in Equation  7.3-52).

Internal Emissivity   sets the internal emissivity of the wall. This item will appear only if you are using the P-1 model, the DTRM, the discrete ordinates model, or the S2S model for radiation heat transfer. (Note that it will not appear if you are using the non-gray discrete ordinates model. In this case, you will enter the Internal Emissivity for each band under Radiation.)

Wall Thickness   sets the thickness of the wall for calculation of thin-wall thermal resistance. (See Section  7.3.14 for details.)

Heat Generation Rate   sets the rate of heat generation in the wall.

Contact Resistance   sets the contact resistance ( $R_c$ in this equation in the separate Theory Guide) at the wall. See Section  25 for details. This item appears only when the solidification/melting model is used.

Material Name   sets the material type of the wall. The conductivity of the material is used for the calculation of thin-wall thermal resistance. (See Section  7.3.14 for details.) Material is used only when Wall Thickness is non-zero. Materials are defined with the Materials task page.

Shell Conduction   enables shell conduction for the wall. See Section  7.3.14 for details.

Radiation   displays the boundary conditions for the DO radiation model at the wall. This tab is available only if you are using the discrete ordinates radiation model. See Section  13.3.6 for details.

BC Type   contains a drop-down list of available radiation boundary condition types. The available options are opaque and semi-transparent.

Internal Emissivity   specifies the internal emissivity of the wall in each wavelength band. This item will appear only if you are using the non-gray discrete ordinates radiation model and you have selected opaque as the BC Type.

Diffuse Fraction   specifies the fraction of the irradiation that is to be treated as diffuse. By default, the Diffuse Fraction is set to 1, indicating that all of the irradiation is diffuse. If the non-gray DO model is being used, the Diffuse Fraction can be specified for each band.

Beam Width   specifies the beam width for an external semi-transparent wall in terms of the Theta and Phi extents. This item will appear only if you are using the discrete ordinates radiation model and you have selected semi-transparent as the BC Type.

Beam Direction   specifies the beam direction as an X,Y,Z vector. You can specify the Beam Direction as a constant, a profile, or a UDF. This item will appear only if you are using the discrete ordinates radiation model and you have selected semi-transparent as the BC Type.

Direct Irradiation   specifies the value of the irradiation flux. If the non-gray DO model is being used, a constant Direct Irradiation can be specified for each band.

This item will appear only if you are using the discrete ordinates radiation model and you have selected semi-transparent as the BC Type.

Apply Direct Irradiation Parallel to the Beam   is the default means of specifying the scale of irradiation flux. When enabled, ANSYS FLUENT assumes that the value of Direct Irradiation that you specify is the irradiation flux parallel to the Beam Direction. When deselected, ANSYS FLUENT instead assumes that the value specified is the flux parallel to the face normals and will calculate the resulting beam parallel flux for every face.

Diffuse Irradiation   specifies the value of the irradiation flux. If the non-gray DO model is being used, a constant Diffuse Irradiation can be specified for each band.

This item will appear only if you are using the discrete ordinates radiation model and you have selected semi-transparent as the BC Type.

Species   contains the species parameters. This tab is available only if you have enabled the Species Transport model in the Species Model dialog box.

Reaction   activates reactions at the wall. This item will appear only if you have enabled any of the reactions in the Species Model dialog box.

Reaction Mechanisms   allows you to specify a defined group, or mechanism, of available reactions. This item will appear only if the Reaction option has been turned on. See Section  15.1.3 for details about defining reaction mechanisms.

Species Boundary Condition   contains options for the specification of species boundary conditions. See Section  7.3.14 for details.

Zero Diffusive Flux   indicates a zero-flux condition for a species. This is the default condition.

Specified Mass Fraction   indicates that the species mass fraction will be specified.

Species Mass Fractions   contains inputs for the species mass fractions of any species for which you have selected Species Mass Fraction as the Species Boundary Condition.

DPM   contains the discrete phase parameters. This tab is available only if you have defined at least one injection.

Discrete Phase Model Conditions   contains inputs for setting the fate of particle trajectories at the wall. These options will appear when one or more injections have been defined. See Section  23.4 for details.

Boundary Cond. Type   sets the way that the discrete phase behaves with respect to the boundary.

reflect   rebounds the particle off the boundary with a change in its momentum as defined by the coefficients of restitution. (See Figure  23.4.1.)

trap   terminates the trajectory calculations and records the fate of the particle as "trapped''. In the case of evaporating droplets, their entire mass instantaneously passes into the vapor phase and enters the cell adjacent to the boundary. See Figure  23.4.2.

escape   reports the particle as having "escaped'' when it encounters the boundary. Trajectory calculations are terminated. See Figure  23.4.3.

user-defined   specifies a user-defined function to define the discrete phase boundary condition type.

Boundary Cond. Function   sets the user-defined function from the drop-down list.

Discrete Phase Reflection Coefficients   determine the behavior of reflecting particles. This item appears when reflect is chosen as the Boundary Cond. Type. See Section  23.4.1 for details on setting the following items.

Normal   sets the type of function for the normal coefficient of restitution. This function can be constant, piecewise-linear, piecewise-polynomial, or polynomial.

Tangent   sets the type of function for the tangential coefficient of restitution. This function can be constant, piecewise-linear, piecewise-polynomial, or polynomial.

Erosion Model   contains inputs for erosion calculations. See Section  23.4.1 for details about these items.

Impact Angle Function   specifies the value of $f(\alpha)$ in this equation in the separate Theory Guide.

Diameter Function   specifies the value of $C(d_p)$ in this equation in the separate Theory Guide.

Velocity Exponent Function   specifies the value of $b(v)$ in this equation in the separate Theory Guide.

UDS   displays the boundary conditions for user-defined scalars (UDSs) at the wall. This tab is available only if you have specified a non-zero number of user-defined scalars in the User-Defined Scalars dialog box.

User Defined Scalar Boundary Condition   contains options for the specification of UDS boundary conditions. See the separate UDF Manual for details.

Specified Flux   indicates that the flux of the UDS at the wall will be specified.

Specified Value   indicates that the value for the UDS at the wall will be specified.

User Defined Scalar Boundary Value   contains inputs for the value of the flux of the UDS, or the value of the UDS itself, depending on your selection for that UDS under User Defined Scalar Boundary Condition.