Assigning Fluid Block Properties

A fluid block is a block with a fluid material assigned. Fluid blocks are regions of the model where fluid properties can be specified independently of those specified for the default fluid.

The Block Thermal Model dialog box contains the following general and thermal information for the selected boundary condition.

Name	The Name of the boundary condition appears in the Project Manager window and 3D Modeler window.
Power	The Power specifies type of power assigned to the block. Total Power specifies the total power dissipated by the solid block. For steady-state simulations, if needed, select the check box and select Temp Dep or Joule Heating. For Temp Dep, click Edit to specify the temperature dependence of power. For transient simulations, select Temp Dep, Transient, or DTM. Alternatively, specify the power as Power Density. Transient allows you to specify power as a function of time. DTM (dynamic thermal modeling) allows you to specify a temperature-dependent power after each time step of a transient simulation. Alternatively, specify the power as Power Density (Solve Inside enabled) or Heat Flux (Solve inside disabled).
Note: For more information on specifying transient power, see Specifying Parameters as a Function of Time. For more information on dynamic thermal modeling, see DTM - Thermostat for Source Control.
MRF	Moving Reference Frame MRF is available when a fluid material (gaseous fluids only) is assigned to the block's geometry. MRF specifies an angular velocity to model rotating parts in a steady state simulation. See Moving Reference Frame for more information.
Laminar flow	Laminar flow specifies that interior of the block is to be modeled as a laminar zone.
External Thermal Conditions	External Thermal Conditions specifies a Heat Transfer Coefficient and a reference Temperature for the volume of space on the immediate exterior of the currently selected side of the solid block.
Fixed Velocity	Fixed Velocity allows you to fix values of velocities to essentially set a boundary condition for the velocities within the cells of the fluid block. When a velocity is fixed in a given cell, the transport equation for that velocity is not solved in the cell. The fixed value is used for the calculation of face fluxes between the cell and its neighbors. The result is a smooth transition between the fixed value of a velocity and the values at the neighboring cells.

Assigning a Fluid Block and Defining Thermal Properties

To assign a fluid block boundary condition and define its properties:

1. Press O to enable object-selection mode.
2. Select and right-click a three-dimensional geometry component in the 3D Modeler window or the history tree.
   Note:

   To assign a fluid block type, ensure that the material assigned is fluid.

3. From the right-click menu, select Assign Thermal>Block.
4. In the Block Thermal Model dialog box, enter a Name for the block.
5. Under Power, do one of the following:

   • For steady-state simulations, if needed, select the check box and select Temp Dep or Joule Heating. For transient simulations, select Temp Dep, Transient, or DTM. For Temp Dep, click Edit to open the Temperature Dependent Variation dialog box and specify the Variation function and values.

     Note:

     Joule Heating uses the block geometry's Thermal Conductivity to calculate the block's power. See Joule Heating in Icepak for more information.

   • If Solve Inside is enabled, select Power Density and enter a power density value for the block.
   • If Solve Inside is disabled, select Heat Flux and enter a heat flux value for the block.
6. If needed, select the Laminar flow check box.
7. If needed, select the External conditions check box and enter the following values:
   • Heat Transfer Coeff
   • Temperature
8. If needed, select the Fixed Velocity check box and enter velocity values for each coordinate direction.
9. Click OK.