Study On The Turbulent Characteristics Of Flow In An Airfoil Channel

Turbulent channel flow is a fundamental research problem in the field of turbulent.Researchers have been using various models to describe the phenomena of turbulent and expected to develop new turbulent model theory to guide the practical production and application.A variety of mathematical tools and methods were used to analyze the experimental data and numerical simulation results to seek the structural characteristics of the turbulent.In fact,the research results of the asymmetric channel turbulent have been widely used in the industrial production.Therefore,in this paper,we mainly study the non-symmetric channel flow of the airfoil,and study the influence of the airfoil on the internal flow structure of the turbulent flow and turbulent transport characteristics through two basic research methods,experimental research and numerical simulation.The main content of this paper are as follows:In the experimental study,the nonlinear analysis is carried out on the flow velocity time series of each point in the inverse gradient region of the airfoil.By using the EMD analysis method,the flow velocity time series of the relevant points in the counter gradient area are analyzed and the internal model function,the interval of each model and the probability density distribution are studied.According to the characteristic of the model,the probability density of the airfoil is analyzed,and the relevant conclusions are obtained.In addition,the average frequency and the average energy of each modes after the decomposition of the streamwise velocity are analyzed about turbulent coherent scale.There is a significant linear relationship between the modal frequencies and modal orders in the single log coordinate system.By comparing the Hilbert spectra and Fourier spectra,it is clear that the relationship between the time,frequency and energy of the velocity time series are showed and the advantages and disadvantages of the two energy spectra are presented.Moreover,this paper studies the airfoil channel flow streamwise vortex structure scale coherent pulse.In the numerical simulation,the large eddy simulation is used to simulate the channel of the airfoil.The turbulent flow characteristics such as the turbulent flow structure,the mean velocity,the turbulent kinetic energy,streamline evolution and velocity evolution before and after the airfoil height are studied under four different conditions.In addition,the change of Reynolds stress in the wing shape position area is studied.In the four cases,the counter-gradient transport region of the airfoil is in agreement with the experimental results.