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TURBULENT STATISTICS OF RAREFIED FLOWS IN A MICROCHANNEL

Dong-Xing Du
Department of Mechanical Engineering, Kyoto University Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan

Kenjiro Suzuki
Department of Mechanical Engineering, Kyoto University, Kyoto; Department of Machinery and Control Systems, Shibaura Institute of Technology, 307 Fukasaku, Saitama, 337-8570, Japan

Resumo

Direct Numerical Simulation (DNS) has been carried out to investigate the effect of weak rarefaction on turbulent flow characteristics in microchannels. Knudsen numbers of the simulated flow are selected to be O.O(un-rarefied), 0.001, 0.005, 0.01 and 0.02 respectively. Validity of the calculation is demonstrated by the combination of presenting the data of two-point correlation functions and one-dimensional power spectra and comparing the results with available reported results. Turbulent statistics including mean streamwise velocity, turbulent intensities and Reynolds shear stress are investigated under the rarefied conditions. It can be concluded that the weakly rarefied turbulent flow has higher streamwise velocity over the whole channel width. Rarefaction can also lead to higher turbulent intensities and higher Reynolds shear stress in the vicinity ofthe wall.