Establishment of the Direct Numerical Simulation Data Bases of Turbulent Transport Phenomena

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All the investigators involved in this project worked in close cooperation during the past two years in order to establish the direct numerical simulation data bases of turbulent transport phenomena. The outcome of each research group is summarized as follows :Kasagi established the data bases of isotropic turbulence, turbulent channel flows and turbulent Couette-Poiseuille flows with scalar transport, and obtained important information on the turbulence statistics as well as the role of quasi-coherent structures in turbulent transport mechanism.Nagano intensively investigated accuracy of various spectral methods (Galerkin, tau and collocation) and associated aliasing errors in direct numerical simulations of turbulent flows. He established statistical data bases of homogeneous turbulent shear flows.Horiuti applied the Kleiser-Schumann (KS) method to two-dimensional channel and square-duct flows. In channel its consistency with conventional methods was validated with databases being ge … More nerated including heat transfer analysis. In duct, Chebyshev polynomial expansion solvers of Helmholtz equations were compared with the matrix-diagonalization technique. A method to prevent round-off error accumulation and algorithm to implement the KS method to supercomputing were further investigated.Miyauchi and Nagasaki conducted direct numerical simulations of reactive/nonreactive homogeneous isotropic turbulence and a reacting turbulent mixing layer with temperature and concentration assumed to be passive scalars. They made data bases of turbulent energy, scalar fluctuating intensity, energy spectra, budget of scalar fluctuation transport equation, mean reactant and product concentration profiles.Miyake developed DNS codes for turbulent flows in a wavy channel and a straight rectangular duct and for a turbulent round jet, though not finally completed. All the codes are based on finite-difference method. In addition, large eddy simulations of these flows were carried out to supplement the above DNSs. Less