Research On The Characteristics Of The Atmospheric Boundary Layer With Wind Tunnel Simulation

This paper investigates the mean velocity and turbulence profiles in wind tunnel simulations. The dependences of aerodynamic parameters on wind speed and packing density are discussed, which provides some guidance for their practical applications.Firstly, the probability analysis gives rise to a new promising method in which the atmospheric boundary layer is divided into outer layer and inner layer, and the latter can be further divided into four sublayers: stress-descent sublayer, inertial sublayer, transition sublayer and trap sublayer.Secondly, a combined technique considering both constant stress region and error analysis has been proposed for the determination of the most appropriate range in fitting procedures, which greatly reduces the uncertainty of the surface roughness length estimates and leads to the changing trend of aerodynamic parameters. For example, there exists a descent in roughness length as the wind speed increases whilst the zero-plane displacement height is rising with the increase of wind speed; and the friction velocity obtained from curve-fit represents an overall friction velocity while that obtained from the direct measurement of Reynolds stress a shear friction velocity.In addition, an empirical expression for the zero-plane displacement height is proposed for the square arrays of roughness elements, highlighting the influence of free-stream velocity. An alternative model is also developed for the prediction of surface roughness length in which a new factor was introduced to compensate for the effects of wake diffusion and interactions between the roughness obstacles.Finally, a numerical study has been performed using the commercial CFD code Fluent 6.2.16. The comparison of the calculation results with wind tunnel data shows that the boundary layer thickness determined from the mean velocity profile of vertical component is larger than that from the streamwise component.