Convection Currents in Porous Media. IV. Remarks on the Theory

Abstract

Differential equations for critical stability of a fluid in a porous medium and heated from below are solved by an approximate method not hitherto used. A single formula is obtained for the thermal environment at critical stability, apparently valid over a wide range of conditions, which allows for temperature dependence of viscosity and nonlinear temperature distributions. New experiments are reported in which initial convection has been detected by visual, thermal, and radioactive‐trace means. Experimental mean thermal gradients for critical stability deviated from values predicted by the new solution of theory by the following average amounts: visual, 150 percent; thermal, 32 percent; radioisotopic, 11 percent.