Pii: S0020-7225(00)00032-x
نویسنده
چکیده
The problem treated is that of convection in a ̄uid saturated porous layer, heated internally and where the gravitational ®eld varies with distance through the layer. The boundaries are assumed to be solid. It is proved that the principle of exchange of stabilities holds as long as the gravity ®eld and the integral of the heat sources both have the same sign. The proof is based on the idea of a positive operator, and uses the positivity property of the Green's function. Ó 2000 Elsevier Science Ltd. All rights reserved.
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تاریخ انتشار 2000