TY - JOUR

T1 - Cavity flow induced by a fluctuating acceleration field

AU - Thomson, J. Ross

AU - Casademunt, Jaume

AU - Viñals, Jorge

PY - 1995

Y1 - 1995

N2 - Buoyancy driven convection induced by a fluctuating acceleration field is studied in a two dimensional square cavity. This is a simplified model of, for example, fluid flow in a directional solidification cell subject to external accelerations, such as those encountered in a typical microgravity environment (g-jitter). The effect of both deterministic and stochastic acceleration modulations normal to the initial density gradient are considered. In the latter case, the acceleration field is modeled by narrow band noise defined by a characteristic frequency Ω, a correlation time τ, and an intensity G2. If the fluid is quiescent at t=0 when the acceleration field is initiated, the ensemble average of the voracity at the center of the cavity remains zero for all times. The mean squared vorticity 〈ξ 2〉, however, is seen to exhibit two distinct regimes: For t≪τ, 〈ξ2〉 oscillates in time with frequency Ω. For t≫τ, 〈ξ2〉 grows linearly in time with an amplitude equal to R2Pr/(1 + (Ωτ))2, where R is a new dimensionless number which reduces to the Rayleigh number in the case of a constant gravity, and Pr is Prandtl number. At yet later times, viscous dissipation at the walls of the cavity leads to saturation, with 〈ξ2〉sat={(Pr τ+1)R2/[(Pr π+1)2+Ω2τ2]}.

AB - Buoyancy driven convection induced by a fluctuating acceleration field is studied in a two dimensional square cavity. This is a simplified model of, for example, fluid flow in a directional solidification cell subject to external accelerations, such as those encountered in a typical microgravity environment (g-jitter). The effect of both deterministic and stochastic acceleration modulations normal to the initial density gradient are considered. In the latter case, the acceleration field is modeled by narrow band noise defined by a characteristic frequency Ω, a correlation time τ, and an intensity G2. If the fluid is quiescent at t=0 when the acceleration field is initiated, the ensemble average of the voracity at the center of the cavity remains zero for all times. The mean squared vorticity 〈ξ 2〉, however, is seen to exhibit two distinct regimes: For t≪τ, 〈ξ2〉 oscillates in time with frequency Ω. For t≫τ, 〈ξ2〉 grows linearly in time with an amplitude equal to R2Pr/(1 + (Ωτ))2, where R is a new dimensionless number which reduces to the Rayleigh number in the case of a constant gravity, and Pr is Prandtl number. At yet later times, viscous dissipation at the walls of the cavity leads to saturation, with 〈ξ2〉sat={(Pr τ+1)R2/[(Pr π+1)2+Ω2τ2]}.

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U2 - 10.1063/1.868627

DO - 10.1063/1.868627

M3 - Article

AN - SCOPUS:0029105480

SN - 1070-6631

VL - 7

SP - 292

EP - 301

JO - Physics of Fluids

JF - Physics of Fluids

IS - 2

ER -