Linear Stability of a Combined Convective Flow in an Annulus

Abstract

Linear stability analysis of a combined convective flow in an annulus is performed in the paper. The base flow is generated by two factors: (a) different constant wall temperatures and (b) heat release as a result of a chemical reaction that takes place in the fluid. The nonlinear boundary value problem for the distribution of the base flow temperature is analyzed using bifurcation analysis. The linear stability problem is solved numerically using a collocation method. Two separate cases are considered: Case 1 (non-zero different constant wall temperatures) and Case 2 (zero wall temperatures). Numerical calculations show that the development of instability is different for Cases 1 and 2. Multiple minima on the marginal stability curves are found for Case 1 as the Prandtl number increases. Concurrence between local minima leads to the selection of the global minimum in such a way that a finite jump in the value of the wave number is observed for some values of the Prandtl number. All marginal stability curves for Case 2 have one minimum in the range of the Prandtl numbers considered. The corresponding critical values of the Grashof number decrease monotonically as the Prandtl number grows.

On the Stability of a Convective Flow with Nonlinear Heat Sources

“…It is shown in [22] that, for wide gaps, asymmetric (spiral) perturbations are the most unstable ones. The combined effect of nonlinear heat sources and different wall temperatures on the linear stability characteristics is analyzed in [23]. Calculations show that two modes of instability can be present, shear or buoyant instability, depending on the value of the Prandtl number.…”