Characteristic Analysis Of Turbulence Field Generated By A Pair Of Vibrating Grids

Isotropic turbulence greatly simplifies the complexity of turbulence.The nature of the flow can be investigated by studying various flow parameters of isotropic turbulence,which is beneficial to understand the flow law of ordinary turbulence.In this paper,the large eddy simulation(LES)and dynamic grid of computational fluid dynamics software FLUENT is used to simulate approximately isotropic turbulence excited by a pair of vibrating grids.The relationship between the motion parameters of the vibrating grids and the turbulence characteristics is studied when the vibrating frequency under 2Hz,3Hz,4Hz,5Hz and vibrating amplitude under 10 mm,15 mm,20 mm.The main research contents and conclusions are as follows:1)Using the test platform of vibrating grids to verify the correctness of numerical simulation by comparing the result of PIV experiment and numerical simulation.2)It can be concluded that the range of turbulent isotropy is [0.7,1.3],the probability density distribution of the pulsation velocity satisfies the Gaussian distribution,the shear stress is approximately 0,and the power spectrum of the turbulence satisfies the Kolmogorov-5/3 law,which proves that the turbulence generated by the vibrating grids is nearly isotropic turbulence.3)The trend of the flow parameters can be observed by changing the motion parameters and measuring plane position.Under the same vibrating amplitude,as the vibrating frequency increases,the energy input,root mean square velocity,effective turbulence intensity increases,and the energy spectrum moves to the right,the turbulence length scale decrease.If keep the grid vibrating frequency steady,and increase the vibrating amplitude will obtain similar conclusions as above.Finally the specific energy dissipation rate and effective turbulence intensity also can be represented by motion parameter of vibrating grids and measuring plane position.