DNSによる鉛直平板間の自然対流における乱流構造の解析(流体工学,流体機械)

概要

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The objective is to make clear the mechanisms of heat transfer under the bouyancy effect. A Direct Numerical Simulation (DNS) of natural convection in differentially heated vertical slot is conducted with Boussinesq approximation. The discretization of computation is carried out with a spectral method for three directions. Rayleigh number (Ra) which is defined with the slot width and the temperature difference between two walls, is 5.4×10^5. Turbulence structures are investigated in more detail compared to previous researchs. As a results, it reveals that quasi streamwise vortices are not formed in the near-wall region, the large-scale streamwise vortical structure is dominant in the core region of the slot. Then we extracted the large-scale structure by means of proper orthogonal decomposition (POD). Most energetic mode is characterized by the rotational motion, whose axis is in the streamwise direction and its scale is approximately the width of flow passage, and the reconstructed flow structures with low dimensional modes of velocity highly correlates to those of thermal field. Therefore these findings recommend the control of the streamwise directed vortex to enhance effectively the heat exchange.
2006-07-25