Research Into The Scaling Law Of The Streamwise Turbulence Intensity In The Atmospheric Surface Layer

This paper carries out wind tunnel and field experiments to measure the boundary layer flow, which is in order to investigate on how the scaling law of the streamwise turbulence intensity in the atmospheric surface layer varies with the Reynolds number. Through the experimental data acquisition, processing and analysis, we get some new results and try to analyze the mechanism which produces. The main work and results of this paper are:1. This paper carry out laboratory boundary layer experiments of moderate Reynolds number using the multi-purpose environmental wind tunnel in Lanzhou University and the Reynolds number, Re(?) are10394,12982and15325.I find that the distribution of the streamwise turbulence intensity is highly satisfied with logarithmic relationship in the logarithmic region after the statistics and analysis of the experimental data and the slope, i.e. Townsend-Perry constant is almost equal to a constant around1.2which is consistent with the existing results at moderate Reynolds number.2. We simultaneously measured the dataset of wind speed from0.9m to30m,11heights totally, with three-dimensional sonic anemometer by taking advantage of a atmospheric surface layer observing systems which have been built in a dry lake bed, a very flat region in the Nature Reserve of Lake Qingtu located in City Minqin, Gansu Province. Dataset of wind speed on this paper are selected strictly. The wind direction must be suitable and wind speed must be steady, and at the same time, it must be in near-neutral stratified conditions. After analysing the datasets which are selected following these conditions, I find that the distribution of the streamwise turbulence intensity in the atmospheric surface layer is also highly satisfied with logarithmic relationship. However, the Townsend-Perry constant A1is not a constant and it decreace with the Reynolds number increasing. This result indicates that the Reynolds number has a significant impact on the distribution of the streamwise turbulence intensity in the atmospheric surface layer.3. Comparing with the result of wind tunnel and field experiments in this paper and the existing results, this paper points out that, in the scaling law of the streamwise turbulence intensity, the Townsend-Perry constant A1shows a significant segment features:when the Reynolds number is below1.4x106, A1is almost a constant, and when the Reynolds number is higher than1.4x106, A1decreases with the Reynolds number increasing. The reason for this rule, this paper considering, is that with the Reynolds number increasing to a relatively high level, there having significant turbulence intensity in the outer region. In addition, there may also be present in the energy input on the top of the atmospheric surface layer.