Modeling Atmospheric Thermal and Velocity Boundary Layer in a Long Wind Tunnel

Abstract

The Atmospheric Boundary Layer (ABL) is a boundary layer of air over the ground surface whose thickness is the height which the surface
friction no longer affects the general flow of wind. In many industrial aerodynamics and wind engineering applications, modelling conditions with
velocity boundary layer are of special importance and it is usually assumed that the influence of heat convection is negligible. However during air
pollution applications, the temperature structure of the boundary layer because of inversion level is in essential effort. In this paper, the governing
equations in modelling of ABL in long Environmental Wind Tunnel (EWT) are discussed. The velocity boundary layer in long EWT is defined from
the beginning of the wind tunnel’s test section. The modelling structure of its ABL is based on surface roughness of the prototype and wind tunnel
floor for three defined exposures. Conversely, the starting position for the thermal boundary layer modelling would differ for various cases. The
heating/cooling of floor and roof of the test section is based on thermal profile of the ABL and discussed in this paper in order to obtain the desired
thermal profile at the model’s mounted section of the wind tunnel. Moreover, it is determined that the development of the velocity boundary layer is
based on the exposures B, C and D on the wind tunnel floor with the presence of roughness devices, also other cases are most achievable. Finally,
a sample problem is presented by modelling a real case by considering Monin-Obukhove length scale for modeling real atmospheric boundary
layer profile.