NUMERICAL STUDY ON MODE-TRANSITION OF NATURAL-CONVECTION IN DIFFERENTIALLY HEATED INCLINED ENCLOSURES

The present paper reports a numerical investigation of natural convect ion and the associated mode-transition and hysteresis phenomena in a t wo-dimensional differentially heated inclined enclosure. Unsteady Navi er-Stokes/Boussinesq equations governing the fluid flow and heat trans fer are solved numerically. Rayleigh numbers in steady flow regime, 1 x 10(3) less than or equal to Ra less than or equal to 2 x 10(4), and the angles of inclination of 0 degrees less than or equal to gamma les s than or equal to 90 degrees are considered in the computations. Majo r concerns are the effects of inclination on flow-mode transition. Enc losures of length-to-height aspect ratio As = 4, 3 and 1 are studied. Air of PI = 0.71 in an enclosure of As = 4 is chosen as the flow model to examine the influences of the inclination at various Rayleigh numb ers. Hysteresis phenomena for Ra greater than or equal to 2000 are dem onstrated. Parameter maps of Ra vs gamma for As = 4 with gamma increas ing and decreasing are proposed, in which flow regimes characterized b y various modes are designated. Effects of initial condition on the fl ow pattern formation are examined for As = 3. In a model of square enc losure (As = 1), effect of the imperfect thermal boundary conditions i s examined to investigate the possible causes for inconsistency of the predictions with the experiments. The present study provides more phy sical insight into the natural convection in enclosures. Copyright (C) 1996 Elsevier Science Ltd.