Effect Of Pressure Gradient On Receptivity In Natural Transition Of Plate Boundary Layer

Turbulence characteristics in the atmosphere and ocean are ubiquitous,so the physical properties and dynamic processes of the atmosphere and ocean are very complex.Therefore,turbulent motion has always been a hot topic in the theoretical study of the boundary layer between the atmosphere and the ocean,and the receptivity of the boundary layer is the stratification of the stratus.The initial stage plays a very important role in the cause of turbulence,so the study of this problem not only contributes to the improvement of turbulence theory,but also has broad application prospects in ocean and atmospheric theory research.Based on the incompressible Navier-Stokes equation,the high-resolution compact finite difference scheme and Fourier expansion method are used to numerically study the receptivity of the pressure gradient boundary layer under free-flow turbulence.The research contents can be divided into three aspects:(1)The problem of the pressure gradient boundary layer receptivity under free-stream turbulent and wall local roughness is studied,and it is proved that the local receptivity exists in the pressure gradient boundary layer under the free-stream turbulent and wall local roughness.The group velocity of the small disturbance wave packet excited by pressure gradient boundary layers is calculated numerically;The effects of the pressure gradient on the amplitude,growth rate,wave number,phase velocity and characteristic shape function of the excited T-S wave in the boundary layer are studied numerically.Finally,the relationship between the initial amplitude and the local roughness of the wall in the pressure gradient boundary layer is numerically studied.(2)The problem of the pressure gradient boundary layer receptivity under free-stream turbulent and wall local blowing/suction is studied,and it is proved that the local receptivity exists in the pressure gradient boundary layer under the free-stream turbulent and wall local blowing/suction.The group velocity of the small disturbance wave packet excited by pressure gradient boundary layers is calculated numerically;The effects of the pressure gradient on the amplitude,growth rate,wave number,phase velocity and characteristic shape function of the excited T-S wave in the boundary layer are studied numerically.Finally,the relationship between the initial amplitude and the local blowing/suction intensity of the wall in the pressure gradient boundary layer is numerically studied.(3)The relationship between the initial amplitude and the pressure gradient coefficient in the boundary layer under the interaction of free-stream turbulent and wall local roughness(blowing)is studied.The numerical results is presented,when the pressure gradient coefficient changes from the favorable pressure gradient to the unfavorable pressure gradient,the initial amplitude of the TS wave packet excited in the pressure gradient boundary layer will gradually increase.