様々な周波数と振幅で振動する立方体容器内の熱対流構造

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In this study, the authors numerically investigate the frequency response on the three-dimensional thermal convection in a cubic cavity heated from below in the gravitational field, concerning flow characteristics such as flow structure and a global quantity the spatially-averaged kinetic energy K. The authors assume incompressible fluid with a Prandtl number Pr = 7.1 (water) and with a Rayleigh number Ra = 1.0×104 or 4.0×104. The direction of a forced sinusoidal oscillation is parallel to the terrestrial gravity. The authors especially focus upon the influences of both the forced-oscillation amplitude η and frequency ω in non-dimensional forms, whose test ranges are 1.5 ≤ η ≤ 15 and 10 ≤ ω ≤ 103. The obtained results are as follows. For Ra = 4.0×104, as well as Ra = 1.0×104 (Tanigawa et al., 2009), we can observe the optimum frequency ω|K|max where the amplitude of K attains the maximum for each η. And, for both Ra's, ω|K|max becomes the minimum at η = 1.5 - 2.0. Especially for Ra = 4.0×104, ω|K|max is affected by the initial conditions. For both Ra's, the maximum of the K amplitude uniquely exists at ω = ω|K|max each η, when η < 1.5. On the other hand, we can observe not single but plural peak frequencies with locally-maximum |K|'s for each η, when η ≥ 1.5. It is confirmed that such plural frequencies are related with the appearances of various flow structures. Especially for Ra = 4.0×104, this relation is also affected by the initial conditions. In addition, the details of a new flow structure are reported.
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様々な周波数と振幅で振動する立方体容器内の熱対流構造

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