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 C_{p0} = 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 C_{p}
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 = p_{w} + C_{p} 1 ⁄ 2 v^{2} ρ,
where p_{w} 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 C_{p,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.
unit
and quantity
attributes.