Study On Isotropic Turbulence And Its Applications

The development process of isotropic turbulence is of great significance to recognize the motion law of turbulent flow in general.This paper established a set of advanced large scaleoscillating grid turbulence and carried out a series of physical analysis of the formation and spatial development in water tank.The arangement of measurement is devided into two times: first time, the experiment is carried out with a wide range of measurgment area.There are three different heights of measurement.Each height decorated three measure area. second time, experiment decorated one measure area with a smaller scale. This area is decorated in the area of isotropic turbulence.Through the measurement data and theoretical analysis, studied the movement and development of isotropic turbulence in detail. Obtained the following conclusions:(1) oscillating grid turbulence in this paper is a random process;(2) The large scaleoscillating grid turbulence system indeed can generate nealy isotropic turbulence, but is not exsit in the whole tank. The generate area is in the middle of the water tank;(3) The isotropic turbulence generated in the water tank is strongly dependence on vibration frequency and amplitude;(4) In the area of isotropic turbulence, physical quantities including velocity, shear stress and turbulence intensity keep stable. The decay of power spectrum with the power of-5/3.Integral length scale and time integral scale are linear increase with the incerase of distance from the grid,and the size of the two kinds of integral scale are dependent on the size of the grid and hole size of grid;(5) Fixed the index and coefficient of formula to apply to this paper.