Variable gravity effects on thermal instability in a porous medium with internal heat source and inclined temperature gradient

The onset of convection in a horizontal fluid saturated isotropic porous la yer, induced by inclined temperature gradient and internal heat source, sub ject to a gravity field varying linearly with location along the gravitatio nal acceleration direction, is investigated using Galerkin technique. The b oundaries are assumed to be impermeable and perfectly conducting. It is see n that the value of the variable gravity parameter plays a decisive role on the onset of convection. When the variable gravity parameter is zero and p ositive, an increase in the heat generation due to internal heat source adv ances the onset of convection in both the presence and absence of inclined temperature gradient. On the other hand, when the variable gravity paramete r is negative, the opposite effect is seen. Further, it is observed that at the onset of convection the favourable mode is always the stationary longi tudinal mode. (C) 2001 Published by The Japan Society of Fluid Mechanics an d Elsevier Science B.V. All rights reserved.