Specifying Boundary Conditions

To simplify the scenario being modeled, for the fluid region you define constant temperature and constant velocity at the inlet.

In reality the exhaust gas flow entering the manifold is pulsated. This case assumes that the temperature and velocity are averaged externally before setting up the simulation, and hence the Time Averaging Option on the mapped contact boundary is set to Instantaneous. Had the temperature and velocity been received in their pulsed state, the option would be set to Sliding Window Average or Running Average.

To specify the boundary conditions:

For the fluid region Regions > Gas:

Select the Boundaries > inlets node, set the Type to Velocity Inlet, and set the following properties:


Node	Property	Setting
Physics Values
Static Temperature	Value	500 K
Velocity Magnitude	Value	10 m/s

Select the Boundaries > outlet node, set Type to Pressure Outlet, and set the following properties:


Node	Property	Setting
Physics Values
Static Temperature	Value	360 K
Pressure	Value	0 Pa

The Type of the boundary [Gas/Manifold (Thermal)] [0] is set automatically to Mapped Contact Boundary. Additionally, set the following properties:


Node	Property	Setting
Physics Conditions
Time Averaging Option	Option	Instantaneous
Physics Values
Static Temperature	Method	Mapped Temperature

For the solid region Regions > Manifold (Thermal):

Select the Boundaries > exhaust connection node and set the following conditions:


Node	Property	Setting
Physics Conditions
Thermal Specification	Condition	Convection
Physics Values
Ambient Temperature	Value	360 K
Heat Transfer Coefficient	Value	6.667 W/m^2-K

Select the [Gas/Manifold (Thermal)] [1] node and set the following properties:


Node	Property	Setting
Physics Values
Ambient Temperature	Method	Mapped Reference Temperature
Heat Transfer Coefficient	Method	Mapped Specified Y+ Heat Transfer Coefficient

This interface boundary is of the type Mapped Contact Boundary, which is set automatically when you specify the corresponding interface as a mapped contact interface.

The Mapped Reference Temperature and Mapped Specified Y+ Heat Transfer Coefficient are the values calculated when explicitly mapping Boundary Heat Flux and Specified Y+ Heat Transfer Coefficient on the Mapped Contact Interface. The Y+ value can be set in the User Specified y+ property of the Specified Y+ Heat Transfer Coefficient field function. The default value is 100.

Set the other surfaces as Wall, applying the following conditions:


Node	Property	Setting
Physics Conditions
Thermal Specification	Condition	Convection
Physics Values
Ambient Temperature	Value	360 K
Heat Transfer Coefficient	Value	50 W/m^2-K

Save the simulation.