温度・速度混合層内に発達する波動現象の解明

概要

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The present wind tunnel experiment verified streamwise development of internal gravity waves from their spontaneous generation to collapse into turbulence. Strongly stably-stratified mixing layer was realized in which the maximum local temperature gradient reached about 1 100 K/m and the local Richardson number exceeded 0.25. Simultaneous measurements were made on instantaneous temperature and velocity fluctuations in the mixing layer. Energy density levels of quasiperiodic components of temperature and velocity fluctuations below the Brunt-Vaisala frequency increased rapidly downstream and the internal gravity waves having frequency components of 1.0 Hz, 1.8 Hz, 2.8 Hz were confirmed to develop in the streamwise direction. The phase difference between the vertical component of velocity fluctuation and temperature fluctuation approached -π/2. The constitution of fine structure of the internal gravity waves swung in time as they grew downstream. The energy of their low-frequency components were transported toward the higher frequency components through their nonlinear interaction and the internal gravity waves collapsed into turbulence locally in the mixing layer. Then, the stably stratified flow field was rapidly broken down.
社団法人日本機械学会の論文
1999-11-25