Stability of Convective Ventilation after Fan Switching-Off in Mines

Abstract

The stability of convective air motion in mine shafts after disactivating the draft source is investigated. Based on numerical simulation, it is found that the mine ventilation with natural draft is violated by the formation of air vortices extended along the shaft depth. The transverse profiles of motion velocity and air temperature are determined in approximation of a plane-parallel laminar flow of an incompressible medium with a vertical temperature gradient in the gravity field. Analytical calculations of the stability of the found flow to plane long-wave perturbations are carried out, as a result of which the value of critical Rayleigh parameter is obtained. A correction to the coefficient of air volume expansion allowing taking the hydrostatic compressibility of air into account is simulated. The dependence of the critical value of air temperature vertical gradient in the shaft, the excess of which leads to the formation of convective vortices and violation of through ventilation, is calculated.