Linear-Stability Analysis of Thermocapillary-Buoyancy Convection in an Annular Two-Layer System with Upper Rigid Wall Subjected to a Radial Temperature Gradient

Abstract

This paper presented a linear-stability analysis on thermocapillary-buoyancy convection in radially heated annular pool filled in 5cSt silicone oil / HT-70 two-layer fluids. The influences of the aspect ratio, radius ratio and thickness ratio on the flow stability were discussed. Results indicate that the system is most unstable when the thickness ratio is close to 0.375. Flow bifurcation appears when the thickness ratio varies from 0.625 to 0.875. Three corresponding destabilization mechanisms were revealed. Effect of buoyancy convection and the upper boundary condition on the flow stability were also analyzed. The upper rigid wall can enhance the flow stability in the annular two-layer system, especially when the thickness ratio is near 0.75. Furthermore, the buoyancy can greatly reduce the flow stability comparing with that under the microgravity condition.