Inlet

This condition should be used on boundaries for which there is a net flow into the domain. To obtain a numerically well-posed problem, it is advisable to also consider the Outlet conditions when specifying an Inlet condition. For example, if the pressure is specified at the outlet, the velocity may be specified at the inlet, and vice versa. Specifying the velocity vector at both the inlet and the outlet may cause convergence difficulties.

Boundary Condition

The available options for an inlet are and . After selecting a from the list, a section with the same or a similar name displays underneath. For example, if is selected, a section, where further settings are defined, is displayed.

Velocity

The is specified as u = −nU0, where n is the boundary normal pointing out of the domain and U0 is the normal inflow speed.

The option sets the velocity vector to u = u0. The components of the inlet velocity vector u0 should be defined for this choice.

Pressure Conditions

This option specifies the normal stress, which in most cases is approximately equal to the pressure. If the reference pressure pref, defined at the physics interface level, is equal to 0, the value of the p0, at the boundary, is the absolute pressure. Otherwise, p0 is the relative pressure at the boundary.

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The option adjusts the inlet pressure locally in order to prevent fluid from exiting the domain through the boundary. If you clear the suppress backflow option, the inlet boundary can become an outlet depending on the pressure field in the rest of the domain.

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controls in which direction the fluid enters the domain.

For , it prescribes zero tangential velocity component.

For , an du (dimensionless) should be specified. The magnitude of du does not matter, only the direction. du must point into the domain.

Constraint Settings

This section is displayed by clicking the button (

) and selecting .

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Prescribing Inlet and Outlet Conditions

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Normal Stress Boundary Condition