• 한국전산유체공학회:학술대회논문집
• /
• 2002.05a
• /
• pp.8-15
• /
• 2002

For the large scale computation of turbulent flows around an arbitrarily shaped body, a parallel LES (large eddy simulation) code has been recently developed in which domain decomposition method is adopted. METIS and MPI (message Passing interface) libraries are used for domain partitioning and data communication between processors, respectively. For unsteady computation of the incompressible Wavier-Stokes equation, 4-step splitting finite element algorithm [1] is adopted and Smagorinsky or dynamic LES model can be chosen fur the modeling of small eddies in turbulent flows. For the validation and performance-estimation of the parallel code, a three-dimensional laminar flow generated by natural convection inside a cube has been solved. Then, we have solved the turbulent flow around MIRA (Motor Industry Research Association) model at $Re = 2.6\times10^6$, which is based on the model height and inlet free stream velocity, using 32 processors on IBM SMP cluster and compared with the existing experiment.

• Journal of Mechanical Science and Technology
• /
• v.20 no.4
• /
• pp.569-579
• /
• 2006

In the present study, the unsteady Couette flow with heat transfer of a dusty viscous incompressible electrically conducting fluid under the influence of an exponential decaying pressure gradient is studied without neglecting the Hall effect. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below while the fluid is acted upon by an external uniform magnetic field is applied perpendicular to the plates. The governing equations are solved numerically using finite differences to yield the velocity and temperature distributions for both the fluid and dust particles.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.4
• /
• pp.11-18
• /
• 2006

Compound flow by confluence of two parallel flows through a convergent channel and its choking phenomenon are calculated by one-dimensional isentropic model and completely mixing model. Optical observations and pressure measurements for subsonic/subsonic compound flows are carried out and compared with the results of one-dimensional calculations. As a result, it is found that inlet conditions of one flow influence the behavior of the other flow as well as the choking condition and present experimental data agree well with the results of one-dimensional calculations.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1332-1336
• /
• 2009

If water-chillers are arranged in series-series counterflow, compressor lift of each chiller will be decreased in comparison with water-chillers in parallel. That means that compressor power of the chillers in series will be lower than that of chillers in parallel. However, the pressure drop of the water flow through the chillers in series will increase, and thus increase the power of water pumps. This disadvantage will be made good by increasing the temperature difference of water flow through evaporator and condenser, but the water flow rates will decrease. This paper explores the optimal parameters in system of series-series counterflow for central chilled water plants such as the leaving chilled water temperature, the leaving condenser water temperature, condenser water flow rate and number of chillers in series.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1404-1408
• /
• 2008

The migration and proliferation of vascular endothelial cells (VEC), which play an important role in vascular remodeling, are known to be regulated by hemodynamic forces in the blood vessels. When shear stresses of 2, 6, 15 dynes/$cm^2$ are applied on mouse micro-VEC in vitro, cells surprisingly migrate against the flow direction at all conditions. While higher flow rate imposes more resistance against the cells, reducing their migration speed, the horizontal component of the velocity parallel to the flow increases with the flow rate, indicating the higher alignment of cells in the direction parallel to the flow at a higher shear stress. In addition, cells exhibit substrate stiffness and calcium dependent migration behavior, which can be explained by polarized remodeling in the mechanosensitive pathway under shear stress.

• Electronics and Telecommunications Trends
• /
• v.9 no.4
• /
• pp.9-21
• /
• 1994

Wide variety of the architectural complexity of parallel computer often makes it difficult to develop efficient programs for them. One of approaches to improve this difficulty is to program in familiar sequential languages such as Fortran or C and to parallelize sequential programs into equivalent parallel programs automatically. This paper presents an organization of parallelizing compiler which transforms sequential programs into equivalent parallel programs. The parallelizer consists mainly of syntax analysis, control and data flow analysis, program transformation, and parallel code generation. In particular, the program restructuring in this parallelizer maximizes loop parallelism.

• Tribology and Lubricants
• /
• v.15 no.1
• /
• pp.24-28
• /
• 1999

This paper describes a new pivoting technique to improve bearing performance in pivoted pad thrust bearings. This new technique adjusts the pivot line in a line pivoted pad thrust bearing to be parallel to the trailing edge of a sector shaped pad. Bearing performance factors such as load carrying capacity, frictional torque and flow rate are numerically investigated for conventional point-pivoted and line-pivoted pads and for the new parallel-line pivoting technique. It is shown that the load carving capacity can be maximized with the new technique.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.20 no.4
• /
• pp.333-354
• /
• 2016

The present investigation deals, heat and mass transfer characteristics with the effect of slip on the hydromagnetic pulsatile flow through a parallel plate channel filled with saturated porous medium. Based on the pulsatile flow nature, exact solution of the governing equations for the fluid velocity, temperature and concentration are obtained by using two term perturbation technique subject to physically appropriate boundary conditions. The expressions of skin friction, Nusselt number and Sherwood number are also derived. The numerical values of the fluid velocity, temperature and concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. By increasing the slip parameter at the cold wall the velocity increases whereas the effect is totally reversed in the case of shear stress at the cold wall.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.4
• /
• pp.333-348
• /
• 2023

In this study, a 3D model of the proton exchange membrane fuel cell is established, and a new 3D baffle structure is designed, which is combined with the parallel flow field and then optimized by numerical simulation methods. The number of baffles and the cross-sectional trapezoidal base angle are taken as the main variables, and their impacts on the performance indexes of the cathode side are analyzed. The results show that the 3D baffle can facilitate the convection and diffusion mass transfer of reactants, improve the uniformity of oxygen distribution, enhance the drainage capacity, and make the cell performance superior; however, too small angle will lead to excessive local convective mass flux, resulting in the decrease of the overall uniformity of oxygen distribution and lowering the cell performance. Among them, the optimal number of baffles and angle are 9 and 58°, respectively, which improves the net output power density by 10.8% than conventional flow field.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.12
• /
• pp.3546-3552
• /
• 2009

In this study, an analysis code was created for a 190*650*25-mm (W*H*D) parallel-flow evaporator, and research was done on how to increase the heat transfer rate of aluminum PF heat exchanger for application in IDU. After varying the R410A refrigerant up-down flow to two and three passes and the distribution ratio to 1:1:1 and 1:2:2, it was determined that the two-pass flow has a 30% higher partial heat transfer rate and a 25% lower heat transfer coefficient compared to the three-pass flow. As for the distribution ratios of the three-pass flow, 1:1:1 was found to have a lower refrigerant pressure loss than 1:2:2 distribution. It was assumed, though, that the refrigerant distribution had a uniform flow and that its value was thus overestimated in the actual case of maldistribution in each pass.