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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of computational fluids engineering
Journal Basic Information
Journal DOI :
Korea Society of Computational Fluids Engineering
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Volume & Issues
Volume 16, Issue 4 - Dec 2011
Volume 16, Issue 3 - Sep 2011
Volume 16, Issue 2 - Jun 2011
Volume 16, Issue 1 - Mar 2011
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COMPUTATIONAL DESIGN OF A FLUTED NOZZLE FOR ACHIEVING TARGET AERODYNAMIC PERFORMANCE
Kang, Y.J. ; Yang, Y.R. ; Hwang, U.C. ; Myong, R.S. ; Cho, T.H. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 1~7
DOI : 10.6112/kscfe.2011.16.3.001
As a preliminary design study to achieve target aerodynamic performance, this work was conducted on an original nozzle with 9 flutes in order to design a fluted nozzle with 12 flutes. The thrust and rolling moment of the nozzle with 12 flutes were analyzed using a CFD code according to the depth and rotation angle of the flutes. Based on this, a fluted nozzle with 12 flutes was optimized to yield the same thrust as that of the original nozzle with 9 flutes. The response surface method was applied for shape optimization of the fluted nozzle and design variables were selected to determine the depth angle and rotation angle of the flutes. An optimized shape that led to a thrust as strong as that of the original nozzle was obtained.
NUMERICAL ANALYSIS OF THE FLOW AROUND A ROTARY OSCILLATING CIRCULAR CYLINDER USING UNSTEADY TWO DIMENSIONAL NAVIER-STOKES EQUATION
Lee, M.K. ; Kim, J.S. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 8~14
DOI : 10.6112/kscfe.2011.16.3.008
Although the geometry of circular cylinder is simple, the flow is complicate because of the flow separation and vortex shedding. In spite of many numerical and experimental researches, the flow around a circular cylinder has not been clarified even now. It has been known that the unsteady vortex shedding from a circular cylinder can vibrate and damage a structure. Lock-on phenomenon is very important in the flow around an oscillating circular cylinder. The lock-on phenomenon is that when the oscillation frequency of the circular cylinder is at or near the frequency of vortex shedding from a stationary cylinder, the vortex shedding synchronizes with the cylinder motion. This phenomenon can be recognized by the spectral analysis of the lift coefficient history. At the lock-on region the vortex is shedding by the modulated frequency to the body frequency. However, the vortex is shedding by the mixed frequencies of natural shedding and forced body frequency in the region of non-lock-on. In this paper, it was analyzed the relation between the frequency of rotary oscillating circular cylinder and the vortex shedding frequency.
COMPUTATIONAL INVESTIGATION OF NOZZLE FLOWFIELDS AT VARIOUS FLIGHT CONDITIONS FOR AIRCRAFT INFRARED SIGNATURE ANALYSIS
Chun, S.H. ; Yang, Y.R. ; Moon, H. ; Myong, R.S. ; Cho, T.H. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 15~21
DOI : 10.6112/kscfe.2011.16.3.015
Aerothermodynamic flowfields of aircraft engine nozzles are computationally investigated at various flight conditions for infrared signature analysis. A mission profile of subsonic unmanned combat aerial vehicle is considered for the case study and associated engine and nozzles are selected through a performance analysis. Computational results of nozzle and plume flowfields using a density-based CFD code are analyzed in terms of thrust, maximum temperature, length and optical thickness of plume. It is shown that maximum temperature, length, and optical thickness of nozzle plume increase for lower altitude and higher Mach number.
EFFECTS OF INFLOW ANGLE ON LAMINAR FLOW PAST A TRIANGULAR CYLINDER
Park, Tse-Seon ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 22~28
DOI : 10.6112/kscfe.2011.16.3.022
Laminar Flow over an equilateral triangular cylinder is studied for several inflow angles. Under an uniform flow of
NUMERICAL STUDY FOR PRANDTL NUMBER DEPENDENCY ON NATURAL CONVECTION IN AN ENCLOSURE WITH SQUARE ADIABATIC BODY
Lee, Jae-Ryong ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 29~36
DOI : 10.6112/kscfe.2011.16.3.029
The natural convection in a horizontal enclosure heated from the bottom wall, cooled at the top wall, and having a square adiabatic body at its centered area was studied. Three different Prandtl numbers (0.01, 0.7 and 7) were considered for an effect of the Prandtl number on natural convection. A two-dimensional solution for unsteady natural convection was obtained, using Chebyshev spectral methodology for different Rayleigh numbers varying over the range of
. It had been experimentally and numerically reported [1,2] that the heat transfer mode becomes oscillatory when Pr is out of a specific Pr band beyond the critical Ra. In this study, we reproduced this phenomenon numerically. The variation of time- and surface-averaged Nusselt numbers on the hot and cold walls for different Rayleigh numbers and Prandtl numbers was presented to show the overall heat transfer characteristics in the system. And also, the isotherms and streamline distributions were presented in detail to compare the physics related to their thermal behavior.
NUMERICAL INVESTIGATION OF UNSTEADY CAVITATING FLOW ON A THREE-DIMENSIONAL TWISTED HYDROFOIL
Park, Sun-Ho ; Rhee, Shin-Hyung ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 37~46
DOI : 10.6112/kscfe.2011.16.3.037
Unsteady sheet cavitation on a three-dimensional twisted hydrofoil was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. As a verification test of the computational method, non-cavitating and cavitating flows over a modified NACA66 foil section were simulated and validated against existing experimental data. The numerical uncertainties of forces and pressure were evaluated for three levels of mesh resolution. The computed pressure on the foil and the cavity shedding behavior were validated by comparing with existing experimental data. The cavity shedding dynamics by re-entrant jets from the end and sides of the cavity were investigated.
NUMERICAL ANALYSIS FOR CONDUCTION HEAT TRANSFER AND APPRAISAL OF PERFORMANCE INDICES IN LED MONITOR FOR LAPTOP COMPUTER
Park, I.S. ; Sohn, C.H. ; Son, D.H. ; Baik, S.M. ; Park, C. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 47~51
DOI : 10.6112/kscfe.2011.16.3.047
Dark Mura phenomena which can happen at the region with high temperature gradient in a Notebook LCD Monitor using LED light source has numerically been studied. The calculation was conducted under the nearly realistic conditions by considering the anisotropic thermal properties of materials and the real dimensions of each component. The two performance indices of LED monitor, i.e., the maximum temperature and the spacial gradient of temperature were examined for the various shapes, lengths and thickness of heat sink plate. Calculated results give more reasonable temperature distribution comparing with experimental results.
QUASI-PERIODICITY AND CHAOTIC CONVECTION IN A HORIZONTAL ANNULUS WITH A CONSTANT HEAT FLUX WALL
Yoo, Joo-Sik ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 52~58
DOI : 10.6112/kscfe.2011.16.3.052
This study investigates the bifurcation sequence to chaos in a horizontal annulus with a constant heat flux wall. After the first Hopf bifurcation from a steady to a simple time-periodic flow with a fundamental frequency, quasi-periodic flows with two or three incommensurable frequencies appear. A reverse transition from a quasi-periodic flow to a simple periodic flow is observed with increase of Rayleigh number. And finally, chaotic convection is established after appearance of three incommensurable frequencies at a high Rayleigh number. Simple periodic flows exist between quasi periodic flows. The transition route to chaos of the present simulations follows the Ruelle-Takens route.
THERMAL MODEL CORRELATION OF A GEOSTATIONARY SATELLITE
Jun, H.Y. ; Kim, J.H. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 59~65
DOI : 10.6112/kscfe.2011.16.3.059
COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and was developed by KARI for communication, ocean and meteorological observations. COMS was tested under vacuum and very low temperature conditions in order to correlate thermal model and to verify thermal design. The test was performed by using KARI large thermal vacuum chamber. The COMS S/C thermal model was successfully correlated versus the 2 thermal balance test phases. After model correlation, temperatures deviation of all individual units were less than
and global deviation and standard deviation also satisfied the requirements, less than
. The final flight prediction was performed by using the correlated thermal model.
HIGH Ra NUMBER NATURAL CONVECTION IN A TRIANGULAR POOL WITH A HEAT GENERATION
Kim, Jong-Tae ; Park, Rae-Joon ; Kim, Hwan-Yeol ; Hong, Seong-Wan ; Song, Jin-Ho ; Kim, Sang-Baik ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 66~74
DOI : 10.6112/kscfe.2011.16.3.066
A fluid in an enclosure can be heated by electric heating, chemical reaction, or fission heat. In order to remove the volumetric heat of the fluid, the walls surrounding the enclosure must be cooled. In this case, a natural convection occurs in the pool of the fluid, and it has a dominant role in heat transfer to the surrounding walls. It can augment the heat transfer rates tens to hundreds times larger than conductive heat transfer. The heat transfer by a natural convection in a regular shape such as a square cavity or semi-circular pool has been studied experimentally and numerically for many years. A pool of an inverted triangular shape with 10 degree inclined bottom walls has a good cooling performance because of enhanced boiling critical heat flux (CHF) compared to horizontal downward surface. The coolability of the pool is determined by comparing the thermal load from the pool and the maximum heat flux removable by cooling mechanism such as radiative or boiling heat transfer on the pool boundaries. In order to evaluate the pool coolability, it is important to correctly expect the thermal load by a natural convection heat transfer of the pool. In this study, turbulence models with modifications for buoyancy effect were validated for unsteady natural convections by volumetric heating. And natural convection in the triangular pool was evaluated by using the models.
NUMERICAL PREDICTION OF THE OPTIMAL STAGGER ANGLES FOR A HIGH-POWER TURBO BLOWER
Park, T.G. ; Chung, H.T. ; Park, J.Y. ; Sung, B.I. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 75~81
DOI : 10.6112/kscfe.2011.16.3.075
The turbo blowers having large power capacity are generally composed of the variable inlet guide vane, the impeller and the variable diffuser. In the present study, the effect of the stagger angles on the aerodynamic performances has been investigated by CFD methods. The design specifications of the reference model having 400kW power were given as 7.43kg/s of mass flow rate, 1.66 of pressure ratio with 12000rpm of impeller rotating speed. As the first simulation parameter, the diffuser vane angle was varied in the range of
20 degree from the initial-design point. The inlet guide vane angles, as the second one, was changed in the range of
40 degree from the initial-design point. The commercial Navier-Stokes solver, ANSYS-CFX, was applied to solve the three-dimensional unsteady flow fields inside the turbo blower. Through the numerical results, the desirable setting angles were proposed to fit the best performance to the variation of the operating conditions.
FLOW ANALYSES AROUND THE BATTERY PACK FOR A NEV
Kim, H.S. ; Han, B.Y. ; Park, H.K. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 82~87
DOI : 10.6112/kscfe.2011.16.3.082
The battery pack, a main component of NEV(Neighborhood Electric Vehicle), needs cooling system when it is charging or discharging to prevent the degradation of the battery charging efficiency. The purpose of this study is to analyse the effects of cooling methods, changing positions of inlet and outlet and changing area ratios of inlet and outlet. It has been observed that in the point of uniform cooling, suction from the exit side is more efficient than blowing from the inlet. And there is a suitable inlet/outlet area ratio in maximizing the mass flow rate. A commercial code, STAR-CCM+(ver. 4.02), was used for the numerical study.
CFD STUDY ON THE COMBUSTION CHAMBER OF A 1 kW CLASS STIRLING ENGINE
Ahn, J. ; Lee, Y.S. ; Kim, H.J. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 88~94
DOI : 10.6112/kscfe.2011.16.3.088
The availability of the thermal energy has been deeply recognized recently to encourage the cascade usage of thermal energy from combustion. Within the framework, a 1 kW class Stirling engine based cogeneration system has been proposed for a unit of a distributed energy system. The capacity has been designed to be adequate for the domestic usage, which requires high compactness as well as low emission and noise. To develop a highly efficient system with satisfying these requirements, a premixed slot type short flame burner has been proposed and a series of numerical simulation has been performed to establish a design tool for the combustion chamber. The thermal radiation model has been found to highly affect the computational results and a proper resolution to analyze the heat transfer characteristics of the high temperature heat exchanger. Finally, the combustion characteristics of the premixed flame with the metal fiber type burner has been studied.
ASSESSMENT of CORE BYPASS FLOW IN A PRISMATIC VERY HIGH TEMPERATURE REACTOR BY USING MULTI-BLOCK EXPERIMENT and CFD ANALYSIS
Yoon, S.J. ; Lee, J.H. ; Kim, M.H. ; Park, G.C. ;
Journal of computational fluids engineering, volume 16, issue 3, 2011, Pages 95~103
DOI : 10.6112/kscfe.2011.16.3.095
In the block type VHTR core, there are inevitable gaps among core blocks for the installation and refueling of the fuel blocks. These gaps are called bypass gap and the bypass flow is defined as a coolant flows through the bypass gap. Distribution of core bypass flow varies according to the reactor operation since the graphite core blocks are deformed by the fast neutron irradiation and thermal expansion. Furthermore, the cross-flow through an interfacial gap between the stacked blocks causes flow mixing between the coolant holes and bypass gap, so that complicated flow distribution occurs in the core. Since the bypass flow affects core thermal margin and reactor efficiency, accurate prediction and evaluation of the core bypass flow are very important. In this regard, experimental and computational studies were carried out to evaluate the core bypass flow distribution. A multi-block experimental apparatus was constructed to measure flow and pressure distribution. Multi-block effect such as cross flow phenomenon was investigated in the experiment. The experimental data were used to validate a CFD model foranalysis of bypass flow characteristics in detail.