Hideki Yoshida*, Nobutoshi Tanaka** and Hitoshi Hozumi*

* Dept. of Civil Engineering and Architecture, Muroran Institute of Technology
** Dept. of Sanitary and Environmental Engineering, Hokkaido University

+ Correspondence should be addressed to Hideki Yoshida:
(27-1, Mizumoto-cho, Muroran, Hokkaido, 050, Japan)

Abstract

Free convection of gas or water in a sanitary landfill layer was discussed theoretically. The free convection theory on a porous medium was applied to a landfill layer. The possibility of free convection in a landfill layer was discussed by calculation of Ra (Rayleigh number) and Da (Darcy number) for some actual situation of a landfill layer.

As a result, the possibility that free convection of gas subject to a vertical or horizontal temperature gradient will arise is little. But when there is a large temperature difference in the landfill layer and the permeability of the layer is high, the possibility that free convection of water will arise is high. In the latter case, the simulation of the temperature distribution is calculated by the heat conservation equation and Brinkman's equation which takes convection into the account. It is assumed that temperature distribution will be affected by convection when the permeability is 10^-11 - 10^-10 m2.

Key words: porous media, landfill layer, free convection, Rayleigh number, Darcy number