Modeling Atmospheric Thermal and Velocity Boundary Layer in a Long Wind Tunnel
2019
SHOJAEE, S. M. Nima
The Atmospheric Boundary Layer (ABL) is a boundary layer of air over the ground surface whose thickness is the height which the surfacefriction no longer affects the general flow of wind. In many industrial aerodynamics and wind engineering applications, modelling conditions withvelocity boundary layer are of special importance and it is usually assumed that the influence of heat convection is negligible. However during airpollution applications, the temperature structure of the boundary layer because of inversion level is in essential effort. In this paper, the governingequations in modelling of ABL in long Environmental Wind Tunnel (EWT) are discussed. The velocity boundary layer in long EWT is defined fromthe beginning of the wind tunnel’s test section. The modelling structure of its ABL is based on surface roughness of the prototype and wind tunnelfloor for three defined exposures. Conversely, the starting position for the thermal boundary layer modelling would differ for various cases. Theheating/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 desiredthermal profile at the model’s mounted section of the wind tunnel. Moreover, it is determined that the development of the velocity boundary layer isbased 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 boundarylayer profile.
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