The onset of penetrative convection in a three-layered porous–air–porous system with internal heat source

The study is devoted to a linear stability problem for system of two horizontal porous sublayers separated by an air interlayer under the influence gravity field. are capable generating heat with constant volumetric strength source proportional solid volume fraction. Equal temperatures maintained at external boundaries three-layered system. onset value internal convection numerically determined in limiting case thin sublayer. critical wave number also found, upon reaching which equilibrium lost system, and convective patterns begin arise. on ratio permeabilities layers, relative thickness lower sublayer, parameter analyzed. This sublayer raised third power Darcy number. New results obtained that take into account localization flow. It shown permeability can both destabilize stabilize motionless state. An increase unambiguously reduces value. A map local large-scale regimes has been constructed coordinates versus parameter. demarcation line transition from one regime another corresponds parameters Rayleigh–Darcy numbers minima bimodal neutral curve have equal values. One belongs region small (a long-wave minimum) defines convection, other large short-wave indicates convection. parameter, required decreases.