[M-IS12] 地球流体力学：地球惑星現象への分野横断的アプローチ

[MIS12-02] Quasi-2D flow structures of Rayleigh-Bénard convection confined in a thin rectangular container

高野 奏汰¹、柳澤 孝寿^2,1、*田坂 裕司^1,2、能登 大輔³、宮腰 剛広² (1.北海道大学大学院工学研究院、2.海洋研究開発機構、3.ペンシルバニア大学)

キーワード：熱対流、流れ構造、准二次元流れ

Rayleigh-Bénard convection (RBC) induced by unstable temperature gradient has been dealt with as a typical research platform for flow instability, transition, pattern formation, and turbulence. The convection is dominated by Rayleigh number (Ra), Prandtl number (Pr), and aspect ratios of the fluid layer. Influence of the aspect ratio, however, has not been investigated deeply unlike other two parameters, although the fluid layers have finite horizontal extent in all laboratory experiments. The present study focuses on quasi-two-dimensional (quasi-2D) flow structures observed in RBCs confined by a thin rectangular container, which has much shorter depth scale relative to the height of layer, about 1/8. Laboratory experiment using a thickener solution indicates a flow transition from vertically slender cell structures to cell structures with unsteady corner rolls while the structures keep quasi-2D characteristics. Experiments using different test fluid elucidated that the critical Ra number for onset of the unsteady corner roll does not depend on Pr number. This is recognized as one of the typical features of Hele-Shaw regime although the test condition does not satisfy the Hele-Shaw limit which is determined by Ra and thickness of the fluid layer.