Experimental Study Of Two-Dimensional Turbulence In Square Domain

Our world is largely made of fluids.Air and water are two of the most common materials on Earth,and their flow in the atmosphere and oceans determines weather and climate.The atmosphere and oceans are approximately seen as realistic physical model of two-dimensional turbulent flow.Equally multi-scale features manifested in 2D turbulence flow,however, the energy transfers process is different from that in 3D turbulence.In this paper,the first part of work focused on the experiment research of 2D turbulence.First,we explained how the electromagnetically driven 2D turbulence system worked and provided the details and parameters of the system.Then we conducted the experiments and used PIV to record the formation of velocity field.We designed two sets of experimental system,the first lateral size is 300×300mm,and found in the region of velocity changing intense has larger magnitude in the vorticity field too;the PDF of fluctuation velocity close to Gussian distribution;and the energy spectrum manifested a dual-power-law with a turning point that approximately corresponded to the injected scale of our experiment;we tried to depict the space-time correlations of the velocity field in 2D turbulent,and the tail has a large fluctuations.Another lateral size is 1000×1000mm.We get the energy spectrum of vorticity by dimensional analysis.And the S-T correlations of the velocity field too.the result shows that with increasing of distance,the correlation weaks.To quantify the multifractality in a 2D bacterial turbulent,a Hilbert based methodology is applied to the velocity field without the ?-limitation,the slope of the Fourier spectrum.A dual-power-law is observed not only for the joint probability density function p(kx,A) of the wavenumber k and the amplitude A,but also for the q th-order Hilbert spectrum Lq(kx). The measured scaling exponents ?(q) of the small-scale motion support Goldstein et al[42]'s theory prediction with the intermittent correction.