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7.6.1 Inputs at Inlet Vent Boundaries

You will enter the following information for an inlet vent boundary:

All values are entered in the Inlet Vent panel (Figure  7.6.1), which is opened from the Boundary Conditions panel (as described in Section  7.1.4).

The first 11 items listed above are specified in the same way that they are specified at pressure inlet boundaries. See Section  7.3.1 for details. Specification of the loss coefficient is described here. Open channel boundary condition inputs are described in Section  23.10.2.

Figure 7.6.1: The Inlet Vent Panel

Specifying the Loss Coefficient

An inlet vent is considered to be infinitely thin, and the pressure drop through the vent is assumed to be proportional to the dynamic head of the fluid, with an empirically determined loss coefficient that you supply. That is, the pressure drop, $\Delta p$, varies with the normal component of velocity through the vent, $v$, as follows:

 \Delta p = k_L \frac{1}{2} \rho v^2 (7.6-1)

where $\rho$ is the fluid density, and $k_L$ is the non-dimensional loss coefficient.


$\Delta p$ is the pressure drop in the direction of the flow; therefore the vent will appear as a resistance even in the case of backflow.

You can define the Loss-Coefficient across the vent as a constant, polynomial, piecewise-linear, or piecewise-polynomial function of the normal velocity. The panels for defining these functions are the same as those used for defining temperature-dependent properties. See Section  8.2 for details.

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