• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.179-183
• /
• 2006

Surface roughness is present in most of the microfluidic devices due to the microfabrication techniques. This paper presents lattice Boltzmann method (LBM) results for laminar flow in a microchannel with surface roughness. The surface roughness is modeled by an array of rectangular modules placed on top and bottom side of a parallel-plate channel. In this study, LBGK D2Q9 code in lattice Boltzmann Method is used to simulate flow field for low Reynolds number in a micro-channel. The effects of relative surface roughness, roughness distribution, roughness size and the results are presented in the form of the product of friction factor and Reynolds number. Finally, a significant increase in Poiseuille number is detected as the surface roughness is considered, while the effect of roughness on the microflow field depends on the surface roughness.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.24 no.1
• /
• pp.103-119
• /
• 2020

In this work, the hydromagnetic and thermal characteristics of natural convection flow in a vertical parallel plate micro-porous-channel with suction/injection is analytically studied in the presence of Hall current by taking the temperature jump and the velocity slip at the wall into account. The governing equations, exhibiting the physics of the flow formation are displayed and the exact analytical solutions have been obtained for momentum and energy equations under relevant boundary conditions. The impact of distinct admissible parameters such as Hartmann number, Hall current parameter, permeability parameter, suction/injection parameter, fluid wall interaction parameter, Knudsen number and wall-ambient temperature ratio on the flow formation is discussed with the aid of line graphs. In particular, as rarefaction parameter on the micro-porous-channel surfaces increases, the fluid velocity increases and the volume flow rate decreases for injection/suction.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.622-625
• /
• 2008

While the research for flow over a circular cylinder has been actively carried out up to the present, it has been known that the flow has not been clarified even now. Various complex flow and aero-acoustic characteristics exist around a circular cylinder such as flow separation, wake and pressure wave propagation. In this paper, research was carried out for wake flow and aeroacoustics over a circular cylinders by using high order, high resolution techniques that are used in two dimensional aero- acoustic analysis. OpenMP parallel processing method was used. For the numerical result, the periodic characteristic of Strouhal Number due to vortex shedding was comparatively analyzed with other experiment values and two dimensional numerical results.

• Journal of applied mathematics & informatics
• /
• v.18 no.1_2
• /
• pp.393-403
• /
• 2005

We study the isothermal flow of a dusty viscous incompressible conducting fluid between two types of boundary motions- oscillatory and non-oscillatory, under the influence of gravitational force. Within the frame work of some physically realistic approximations and suitable boundary conditions, closed form solutions were obtained for the velocity profiles and the skin friction of the particulate flow. These results show that for a constant pressure gradient, only the velocity profile of the fluid and the skin friction are unaffected by gravity, while magnetic field is seen to affect both the fluid, particle velocities and the skin friction. Thus, our results are extension of previous results in literature, and graphical demonstration of some these solutions have been presented.

• Journal of Mechanical Science and Technology
• /
• v.18 no.3
• /
• pp.491-498
• /
• 2004

An analysis of the plane Couette flow between two parallel plates of a viscous, incompressible, micropolar fluid is presented. Especially, the effects of non-zero values of the micro-gyration boundary condition coefficient and pressure gradient on the flow fields are studied. Numerical results show that the micro polar parameter was found to have much more of an impact on the flow behaviors. It is also observed that the micro-gyration boundary condition coefficient influenced on the coefficients of skin friction and couple stress due to its different effect on the surface stress.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.250-257
• /
• 2005

Large eddy simulation{LES) methodology used to model a bluff-body stabilized non-reacting flow. The LES solver was implemented on parallel computer consisting 16 processors. To verify the capability of LES code, the results was compared with that of Reynolds Averaged Navier-Stokes(RANS) using $k-{\epsilon}$ model as well as experimental data. The results showed that the LES and RANS qualitatively well predicted the experimental results, such as mean axial, radial velocities and turbulent kinetic energy. However, in the quantitative analysis, the LES showed a better prediction performance than RANS. Specially, the LES well described characteristics of the recirculation zones, such as air stagnation point and jet stagnation point. Finally, the unsteady phenomena on the Bluff-body, such as the transition of recirculation region and vorticity, was examined with LES methodology.

• Journal of Korean Society of Water and Wastewater
• /
• v.14 no.4
• /
• pp.337-342
• /
• 2000

In water treatment plants, open channel is used to distribute incoming flow to parallel treatment unit, such as flocculation basin and sedimentation basin. These control devices must be designed so that the incoming flow evenly distributed to the process unit. this is important in the view of optimizing process unit. In the recent past. significant insights into the sedimentation process have been developed. In this study, the 2-D computer program is developed to investigate fluid flow field and velocity vectors in flocculation sedimentation inlet distribution weir and calculate flow rates in each inlet weir. The specific purpose of this study is to analyze physical design factors, such as now rates, shape of channel, tapered angle in tapered type channel and main channel width.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.3
• /
• pp.321-331
• /
• 1999

A numerical study is carried out for increasing heat removal using indirect cooling system. Computation is performed for nine cases as variation of flow condition in the lower channel. As the result of this study, water is more effective than air at the same pressure loss in spite of the lower inlet velocity. In channel configuration, the vertical channel is more effective than horizontal channel because of the buoyancy effect. Under the condition that heat generation is the same, counter flow effectively decreases the temperature difference among blocks. Parallel flow is more effective than counter flow when average temperature of all blocks is considered. In the case of installing obstacles in the lower channel, it is desirable to install obstacles in the bottom of lower channel. Heat transfer rate increases as the height of obstacles increases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.3
• /
• pp.351-360
• /
• 1996

This study focuses on the development and evaluation of the high efficiency absorption chiller-heater, which can be applied to a direct gas fired, double effect system with 40RT (508,000kJ) cooling capacity. The performance of the absorption chiller-heater is investigated through cycle simulation and experiment to obtain the system characteristics with the inlet tenperature of cooling, chilled water, and gas input flow rate. The efficiency of the different cycles has been studied and the simulation and experiment results show that higher coefficient of performance could be obtained for mixed flow cycle. The five percent difference was obtained from the comparison between experimental and cycle simulation results. As a result of this study, the optimum designs were determined based on the operating conditions and the coefficient of performance.

• Proceedings of the KIEE Conference
• /
• 1998.11b
• /
• pp.666-668
• /
• 1998

In this paper we illustrate the design of a node label data flow machine based on self-timed paradigm. Data flow machines differ from most other parallel architectures, they are based on the concept of the data-driven computation model instead of the program store computation model. Since the data-driven computation model provides the excution of instructions asynchronously, it is natural to implement a data flow machine using self timed circuits.