A Study on Buoyancy Effects in Double-Diffusive Convecting System(II) - Theoretical Study -

J. Ocean Eng. Technol. 1999;13(2):129-137.

Hong, Nam-Ho;Kim, Min-Chan;Hyun, Myung-Taek;

이중확산 대류계에서의 부력효과에 관한 연구(II) - 이론적 연구 -

홍남호;김민찬;현명택;

제주대학교 대학원 기계공학과;제주대학교 화학공학과;제주대학교 기계공학과;

Keywords: Double-Diffusive Convecting System, Natural Convection, Stability Analysis, Soret Effect

핵심용어: 이중확산 대류계, 자연대류, 안정성 해석, Soret 효과

Abstract

The time of the onset of double-diffusive convection in time-dependent, nonlinear concentration fields is investigated theoretically. The initially quiescent horizontal fluid layer with a uniform temperature gradient experiences a sudden concentration change from below, but its stable thermal stratification affects concentration effects in such way to invoke convective motion. The related stability analysis, including Soret effect, is conducted on the basis of the propagation theory. Under the linear stability theory the concentration penetration depth is used as a length scaling factor, and the similarity transform for the linearized perturbation equations. The newlly obtained stability equations are solved numerically. The resulting critical time to mark the onset of regular cells are obtained as a function of the thermal Rayleigh number, the solute Rayleigh number, and the Soret effect coefficient. For a certain value of the Soret effect coefficient, the stable thermal gradient promote double-diffusive convective motion.