Showing papers by "Jae Min Hyun published in 1991"

Three‐dimensional simulations of natural convection in a sidewall‐heated cube

Abstract: A high-resolution, finite difference numerical study is reported on three-dimensional natural convection of air in a differentially heated cubical enclosure over an extensive range of Rayleigh number from 103 to 1010. The maximum number of grid points is 122 × 62 × 62. Solutions to the primitive variable formulation of the incompressible Navier-Stokes and energy equations are acquired by a control-volume-based procedure together with a higher-order upwind-differencing technique. The field characteristics at large-time limits are examined in detail by state-of-the-art numerical visualizations of the three-dimensional results. The emergence of the well-defined boundary layers and the interior core at high Rayleigh numbers is captured by elaborate numerical visualizations. Both the similarities and discrepancies between the three- and two-dimensional computations are pointed out. These emphasize the need for three-dimensional calculations to accurately determine the flow characteristics and heat transfer properties in realistic, high-Rayleigh-number situations.

Experimental investigation of the flow with a free surface in an impulsively rotating cylinder

Abstract: An experimental investigation was made of the impulsive spin-up from rest of a liquid in a partially filled cylindrical container. The main impetus was placed on delineating the effects of the presence of a free surface on the transient development of flow. Of particular interest were the situations in which the free surface intersected either or both of the endwall disks during the course of spin-up. Extensive flow visualizations were carried out by using suspended metal particles. An image processing technique was utilized to determine accurately the propagating velocity shear front as well as the time-dependent free surface contour. Precise measurements of the fluids velocities were obtained by using a laser Doppler velocimeter. The transient velocity profiles were mapped out, and they were found to be in satisfactory agreement with the predictions based on the simplified analysis. The radial location, Rs(t), of the propagating shear front was measured by applying the image processing technique to the visualized azimuthal flow field. The experimental data were found to be consistent with the numerical predictions.