Defining the Default Wall Behavior

You can customize a default wall boundary to control the wall type, thermal condition, radiation behavior, and roughness parameters for surfaces on which no other boundary conditions are specified.

The app creates the default wall boundary automatically when you define the physics for the simulation.

See Also
About Walls
Defining the Fluid Physics of a Flow Simulation
  1. From the tree, expand the Flow container and select the default wall boundary you want to edit.
  2. From the Wall type options, select No-Slip or Slip behavior.

    Important: You cannot select rotating or moving walls as the default wall type.

  3. From the Thermal condition options, specify the default thermal condition for wall boundaries.
    OptionDescription
    Adiabatic No heat exchanged between the wall and the fluid.
    Temperature No heat exchanged, but the wall surface is held at a constant temperature.
    Heat flux Heat exchanged at a specified flux rate.
    Film condition Heat exchange from convection between the wall and the fluid. Two parameters determine the level of heat flux:
    • film coefficient, a constant that relates heat flux to the difference in temperature between the wall and the fluid
    • far field temperature, which is the temperature of the surrounding fluid
    The default values are appropriate for typical objects at room temperature.
    Radiation to ambient Heat radiation from the wall to the environment. The emissivity of the wall (that is, its ability to transmit thermal energy) and the ambient temperature determine the level of radiation.
  4. Select Enable wall roughness to include the effects of wall roughness and the resulting turbulent flow in the simulation by default. You can then set either or both of the following aspects of wall roughness as the default parameters:
    1. Adjust the average Roughness height of the components on the wall that contribute to its roughness. For example, this parameter might specify the average height of the individual grains of sand on a piece of sandpaper.
    2. Adjust the Roughness constant, a measure of the uniformity of roughness. Values range from 0 to 1, with higher values indicating less uniformity. A value of 0.5 represents a tightly packed, uniformly distributed roughness.
  5. Enable surface-to-surface radiation by default by setting the Surface-to-surface radiation option to On. You can also specify the default Emissivity for the radiation.
  6. Enable solar radiation by selecting Enable solar radiation, then expand the Solar wall conditions section to specify default values for any solar radiation parameters.
  7. Click OK.