33.6.1 Fluid Dialog Box

The Fluid dialog box sets the conditions for a fluid cell zone. It is opened from the Cell Zone Conditions task page. See Sections  7.2.1 and 7.2.3 for details about the items below.

Controls

Zone Name   sets the name of the zone.

Material Name   sets the fluid material. The drop-down list contains the names of all materials that have been loaded into the solver. Materials are defined with the Materials task page.

If you are modeling species transport or multiphase flow, the Material Name list will not appear in the Fluid dialog box. For species calculations, the mixture material for all fluid zones will be the material you specified in the Species Model dialog box. For multiphase flows, the materials are specified when you define the phases, as described in Section  24.3.4.

Porous Zone   indicates that the zone is a porous medium. Additional items will appear in the dialog box when this option is enabled. See Section  7.2.3 for details.

Laminar Zone   disables the calculation of turbulence production

in the fluid zone (appears only for turbulent flow calculations using the Spalart-Allmaras model or one of the $k$- $\epsilon$ or $k$- $\omega$ models). See Section  7.2.1 for details.

Source Terms   enables the specification of volumetric sources of mass, momentum, energy, etc. When you turn on this option, the Source Terms tab will be enabled to allow you to input the values for the desired sources. See Section  7.2.5 for details.

Fixed Values   enables the fixing of the value of one or more variables in the fluid zone, rather than computing them during the calculation. See Section  7.2.4 for details.

You can fix values for velocity components, temperature, and species mass fractions only if you are using the pressure-based solver.

Participates In Radiation   specifies whether or not the fluid zone participates in radiation. This option appears when you are using the DO model for radiation.

Reaction   enables/disables reactions in the porous zone.

Motion   lists the parameters associated with the fluid motion.

Rotation-Axis Origin   specifies the origin for the fluid zone's axis of rotation. See Section  7.2.1 for details. This item will appear only for 3D and 2D non-axisymmetric models.

Rotation-Axis Direction   specifies the direction vector for the fluid zone's axis of rotation. See Section  7.2.1 for details. This item will appear only for 3D.

Motion Type   specifies zone motion for a rotating or translating reference frame or for a sliding zone in a sliding mesh problem. The default selection of Stationary indicates that the zone is not moving. To define the motion of a moving reference frame for the zone, select Moving Reference Frame and specify the items below in the expanded portion of the dialog box. See Section  10.7, 10.10.1, or 10.10.2 for details. To define zone motion for a moving (sliding) mesh, select Moving Mesh and set the appropriate parameters below. See Section  11.2.2 for details.

Rotational Velocity   contains an input field for the rotational Speed of the zone. This item will appear if you select Moving Reference Frame or Moving Mesh in the Motion Type list.

Translational Velocity   contains inputs for the X, Y, and Z velocities of the zone. This item will appear if you select Moving Reference Frame or Moving Mesh in the Motion Type list.

Porous Zone   lists the parameters associated with the porous zone.

Conical   enables the specification of a conical (or cylindrical) porous medium. This item will appear only when the Porous Zone option is enabled for a 3D case.

Cone Half Angle   specifies the angle between the cone's axis and its surface (see Figure  7.2.4). Set this to 0 to define the porous region using a cylindrical coordinate system. This item will appear only when the Porous Zone and Conical options are enabled.

Snap to Zone   aligns the plane (or line, in 2D) tool with the zone selected in the drop-down list. The tool is centered at the centroid of the zone, with the tool's axis normal to the zone. If this axis is not the desired cone axis, reposition the tool (as described in Section  28.6.1). When you are satisfied with the axis, click on the Update From Plane Tool (or Update From Line Tool) button to update the Cone Axis Vector fields.

This item will appear only when the Porous Zone and Conical options are enabled.

Update From Plane Tool   ( Update From Line Tool in 2D) updates the Direction-1 Vector and (in 3D) the Direction-2 Vector from the plane tool orientation. If the Conical option is enabled, this button will update the Cone Axis Vector and the Point on Cone Axis. See Section  7.2.3 for details. This item will appear only when the Porous Zone option is enabled.

Direction-1 Vector, Direction-2 Vector   indicate the directions for which the resistance coefficients are defined. See Section  7.2.3 for details. These items will appear only when the Porous Zone option is enabled, but the Conical option is not. (In 2D, only Direction-1 Vector will appear.)

Cone Axis Vector   specifies the X,Y,Z vector for the cone's axis.

This item will appear only when the Porous Zone and Conical options are enabled.

Point on Cone Axis   specifies a point on the cone's axis. This point will be used by ANSYS FLUENT to transform the resistances to the Cartesian coordinate system.

This item will appear only when the Porous Zone and Conical options are enabled.

Relative Velocity Resistance Formulation   allows ANSYS FLUENT to either apply the relative reference frame or the absolute reference frame. This allows for the correct prediction of the source terms.

Viscous Resistance, Inertial Resistance   contain inputs for the viscous resistance coefficient $1/\alpha$ and the inertial resistance coefficient $C2$ in each direction. See Section  7.2.3 for details. These items will appear only when the Porous Zone option is enabled.

Alternative Formulation   provides better stability to the calculation when your porous medium is anisotropic.

If you have enabled the Conical option, Direction-1 is the cone axis direction, Direction-2 is the normal to the cone surface (radial ( $r$) direction for a cylinder), and Direction-3 is the circumferential ( $\theta$) direction.

Power Law Model   contains inputs for the C0 and C1 coefficients in the power law model for porous media. See Section  7.2.3 for details.

Fluid Porosity   contains additional inputs for the porous medium. See Section  7.2.3 for details.

Porosity   sets the volume fraction of fluid within the porous region.

Solid Material Name   specifies the solid material in the porous region.

Reaction   lists the parameters for reactions in the porous zone.

Reaction Mechanism   allows you to specify a defined group, or mechanism, of available reactions. See Section  15.1.3 for details about defining reaction mechanisms.

Surface-to-Volume Ratio   specifies the surface area of the pore walls per unit volume ( $\frac{A}{V}$), and can be thought of as a measure of catalyst loading. With this value, ANSYS FLUENT can calculate the total surface area on which the reaction takes place in each cell by multiplying $\frac{A}{V}$ by the volume of the cell.

Source Terms   defines a source of heat, mass, momentum, turbulence, species, or other scalar quantity within the fluid zone.

Fixed Values   lists the fixed parameters of the fluid zone.

Local Coordinate System For Fixed Velocities   enables the specification of fixed cylindrical velocity components instead of Cartesian components. The local coordinate system is defined by the Rotation-Axis Origin and Rotation-Axis Direction.

This item is available only in 3D, and only when the Fixed Values option is on.