Cavity Orientation Research Articles

Free-forced laminar flow convective heat transfer from a square cavity in a channel with variable inclination

Free-forced laminar flow convective heat transfer from a square cavity in a channel with variable inclination has been investigated numerically using Boussinesq approximated equations. All walls of the geometrical configuration are adiabatic except for the back wall in the cavity which was kept at a constant temperature higher than that of the entering flow. The influence on heat transfer of cavity orientation, channel inclination, flow direction and entrance profile have been studied for flow conditions corresponding to Pr = 0.709, Re = 300 and Gr = 4500; based on the cavity width, mean flow rate and a cavity orientation angle γ = 0 corresponding to vertical channel flow. The calculations show that significant buoyant forces arise in the cavity where Gr/ Re 2 ∼- 30 but that these are small in the channel where Gr/ Re 2 ∼- 0.05. In general, the calculations show enhanced rates of heat transfer when buoyant forces are opposed to the main flow direction and diminished rates of heat transfer when they are aligned in the same direction. Stable stratification of the flow in a downward-facing cavity geometry is responsible for reducing the rate of heat transfer relative to an upward-facing geometry under equivalent flew conditions. Although limited to a narrow range of geometric and dynamic characteristics wherein the Boussinesq approximation applies, the present results show clearly the relative roles and magnitudes of these effects and should therefore be of value to researchers concerned with the influence of buoyancy driven motions in ducted flows.

Model studies of subsidence and ground movement using laser holographic interferometry

Laser holographic interferometry is a method of remotely monitoring surface movement even on the surface of granular material in three dimensions, without the surface disturbances associated with instrument emplacement. In this study models of longwall and room and pillar layouts were used to demonstrate the validity of the technique and, subsequently, to generate data as the parameters controlling displacement were varied. The effects of cavity size, depth and orientation and material elasticity, time and geologic structure on surface displacement were analyzed. Gelatin and sand were successfully used as model materials in the study which has demonstrated that laser holographic interferometry is a practical system with potential to examine complex structures such as multiple panel extraction in longwall, multiple seam extraction or extraction of seams associated with irregular geologic conditions which might otherwise be difficult to monitor.