Inlets

Identify one or more inlet surfaces and define the conditions.

1. On the Fluids ribbon, select the Inlet tool.

Tip: To find and open a tool, press Ctrl+F. For more information, see Find and Search for Tools.
2. Select one or more surfaces as the inlets.
3. In the microdialog, choose a method to define the inlet conditions.
• Velocity: Define the velocity magnitude and the direction of the incoming fluid at an inlet surface.

A constant velocity value is applied on the selected surface along the prescribed direction. Use this condition when you know the exact orientation of the incoming fluid.

• Normal Velocity: Define the velocity magnitude of the incoming fluid entering perpendicular to the inlet surface.

A constant velocity value is applied along a locally perpendicular direction at each point on the inlet surface. Use this condition when the incoming fluid enters the domain perpendicular to the inlet surface.

• Average Velocity: Define the average velocity of the incoming fluid entering perpendicular to the inlet surface.

A spatially varying velocity profile is applied on the inlet surface along a locally perpendicular direction at each point on the inlet surface. This velocity profile is calculated based on a fully developed pipe flow assumption (laminar or turbulent) that models the existence of a boundary layer with an average value equal to the user-specified velocity magnitude. A fully developed boundary layer velocity profile has zero velocity on wall boundaries and maximum velocity farthest away from the walls. The exact variation is based on the flow Reynolds number.

This condition is typically applicable when simulating flow through ducts where the fluid has already traveled for a sufficiently long distance to reach the inlet surface location. During this upstream fluid flow, it is assumed that the fluid velocity profile has gradually evolved from a constant velocity state to a fully developed state.
• Volumetric Flow Rate: Define the volume of the incoming fluid per unit time entering perpendicular to the inlet surface.

The application of this condition follows a similar approach to the Average Velocity condition, where a fully developed velocity profile is computed such that the specified flow rate is enforced on the inlet surface. This velocity profile is calculated based on a fully developed pipe flow assumption (laminar or turbulent) that models the existence of a boundary layer. A fully developed velocity profile has zero velocity on wall boundaries and maximum velocity farthest from the walls. The exact variation is based on the flow Reynolds number.

This condition is typically applicable when simulating flow through ducts where the fluid has already traveled for a sufficiently long distance to reach the inlet surface location. During this upstream fluid flow, it is assumed that the fluid velocity profile has gradually evolved from a constant velocity state to a fully developed state.
• Stagnation Pressure: Define the gauge value of the stagnation pressure of the incoming fluid flow entering perpendicular to the inlet surface. Stagnation Pressure is also commonly known as Total Pressure, since it is calculated as the sum of the fluid's static and dynamic pressure values. The gauge value of pressure is defined as the pressure relative to the atmospheric pressure. For example, if the atmospheric pressure is 14.7 psi (pounds-per-square-inch) and the total (stagnation) pressure at the inlet is known to be 15.2 psi, then a relative value of 0.5 psi must be specified as the gauge stagnation pressure condition at the inlet surface. The inlet velocity profile is automatically computed during the simulation to satisfy the specified total pressure condition at this inlet surface. Use this condition when the inlet velocity or flow rate is unknown.
4. Define the fluid temperature at the inlet.