### 2.6.2. Loss Coefficient

You can optionally specify a Loss Coefficient which can be used to model the pressure drop across a screen or other planar resistance at the opening. The pressure drop is calculated using:

| (2–5)

where f is a specified Loss Coefficient and U n is the normal component of velocity at the opening boundary location. When the opening behaves as an inlet, the pressure drop is applied before flow enters the domain. When the opening behaves as an outlet, the pressure drop is deemed to occur after the flow has left the domain. This results in the following behavior:

#### 2.6.2.1. For a Pressure-Specified Opening

For outflow, the boundary static pressure is the specified Relative Pressure, plus a pressure loss, if specified.

For inflow, the boundary static pressure is the specified Relative Pressure converted from Total to Static Pressure using the normal component of the velocity, minus a pressure loss, if specified.

#### 2.6.2.2. For a Static-Pressure-Specified Opening

For outflow, the boundary static pressure is the specified Relative Pressure, plus a pressure loss, if specified.

For inflow, the boundary static pressure is the specified Relative Pressure, minus a pressure loss, if specified.

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