New Development in Computational Physics of Turbulence

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The achievements of this project include the following.1.Universality in the Statistics of Turbulence :(1) We studied the small scale statistics of turbulence by using the data of DNS with the world's highest resolution. The analysis showed that the DNS does not support assumptions commonly used in phenomenological theories of intermittency of turbulence.(2) An evidence supporting the Loitsyansky hypothesis on universality of large scale statistics in freely decaying turbulence was presented by DNS in a computation domain which is the largest in the DNSs so far made.2.Reduction of Information to be treated :(1) The analysis of the statistics of the energy transfer from large to small scales by using the data of 1-(1)clarified the dependence of the statistics on the method and scale of the coarse graining.-(2) The wavelet-analysis of the statistics of the coherent and incoherent modes of turbulence by using the data of 1-(1)showed that the ratio of the numbers of the coherent modes to that of the total modes decreases with the Reynolds number.3.Wall bounded turbulence :New numerical schemes for DNS of wall bounded turbulence were proposed, and compared with conventional ones. A scheme was shown to be promising in view of the accuracy and cost performance for DNS of boundary layer turbulence. The feasibility of -DNS of the inertial subrange in a turbulent channel flow was examined on the basis of our understanding of the physics.The achievements of 1 and 2 were possible only by DNS at the level of our study, and provide us with sound basis for developing turbulence theory and modeling. The finding in 3 should be useful for very large scale DNS of wall bounded turbulence. They contribute to the understanding of turbulence by computational approaches.