This model describes boundary conditions for pressure, enthalpy, and species concentration that can be obtained from weather data. The model is identical to Buildings.Fluid.Sources.Outside, except that it adds the wind pressure to the pressure at the fluid port ports. The correlation that is used to compute the wind pressure is based on Swami and Chandra (1987) and valid for low-rise buildings with rectangular shape. The same correlation is also implemented in CONTAM (Persily and Ivy, 2001). For other buildings, the model Buildings.Fluid.Sources.Outside_CpData or Buildings.Fluid.Sources.Outside_Cp should be used that takes the wind pressure coefficient as a parameter or an input.

The wind pressure coefficient is computed based on the side ratio of the walls, which is defined as

s = x ⁄ y

where x is the length of the wall that will be connected to this model, and y is the length of the adjacent wall. The wind direction is computed relative to the azimuth of this surface, which is equal to the parameter azi. The surface azimuth is defined in Buildings.Types.Azimuth. For example, if an exterior wall is South oriented, i.e., its outside-facing surface is towards South, use Buildings.Types.Azimuth.S.

Based on the surface azimuth, the wind direction and the side ratio of the walls, the model computes how much the wind pressure is attenuated compared to the reference wind pressure Cp0. The reference wind pressure Cp0 is a user-defined parameter, and must be equal to the wind pressure at zero wind incidence angle. Swami and Chandra (1987) recommend Cp0 = 0.6 for all low-rise buildings as this represents the average of various values reported in the literature. The computation of the actual wind pressure coefficient Cp is explained in the function Buildings.Airflow.Multizone.BaseClasses.windPressureLowRise that is called by this model.

The pressure p at the port ports is computed as

p = pw + Cp 1 ⁄ 2 v2 ρ,

where pw is the atmospheric pressure from the weather bus, v is the wind speed from the weather bus, and ρ is the fluid density.

This model differs from Buildings.Fluid.Sources.Outside_CpData by the calculation of the wind pressure coefficient Cp,act. The wind pressure coefficient is defined by an equation in stead of a user-defined table. This model is only suited for low-rise rectangular buildings.



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