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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of computational fluids engineering
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Journal DOI :
Korea Society of Computational Fluids Engineering
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Volume & Issues
Volume 10, Issue 4 - Dec 2005
Volume 10, Issue 3 - Sep 2005
Volume 10, Issue 2 - Jun 2005
Volume 10, Issue 1 - Mar 2005
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NUMERICAL ANALYSIS OF FLOW AROUND RECTANGULAR CYLINDERS WITH VARIOUS SIDE RATIOS
Rokugou Akira ; Okajima Atsushi ; Gutierrez Isaac ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 1~7
Three-dimensional numerical analysis of the flow around rectangular cylinders with various side ratios, D/H, from 0.2 to 2.0, was carried out for Reynolds number of 10³ by using a multi-directional finite difference method on a regular-arranged multi-grid. The predicted results are in good agreement with the experimental data. It is found that fluid dynamic characteristics of rectangular cylinders alternate between the high-pressure mode and the low-pressure mode of the base pressure for D/H=0.2-0.6. We show that this phenomenon is induced by the change of the flow pattern around rectangular cylinders.
COMPUTATION OF AERODYNAMIC SOUNDS AT LOW MACH NUMBERS USING FINITE DIFFERENCE LATTICE BOLTZMANN METHOD
Kang H. K ; Tsutahara M ; Shikata K ; Kim E. R ; Kim Y. T ; Lee Y. H ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 8~15
Aerodynamic sounds generated by a uniform flow around a two-dimensional circular cylinder at Re=150 are simulated by applying the finite difference lattice Boltzmann method. Thethird-order-accurate up-wind scheme (UTOPIA) is used for the spatial derivatives, and the second-order-accurate Runge-Kutta scheme is applied for the time marching. We have succeed in capturing very small pressure fluctuations with the same frequency of the Karman vortex street compared with the pressure fluctuation around a circular cylinder. The propagation velocity of the acoustic waves shows that the points of peak pressure are biased upstream due to the Doppler effect in the uniform flow. For the downstream, on the other hand, it is faster. It is also apparent that the amplitude of sound pressure is proportional to r /sup -1/2/,r being the distance from the center of the circular cylinder. To investigate the effect of the lattice dependence, furthermore, 2D computations of the tone noises radiated by a square cylinder and NACA0012 with a blunt trailing edge at high incidence and low Reynolds number are also investigate.
ABLATING AND CHARRING OF TWO DIMENSIONAL HEAT SHIELD MATERIALS
Shabani Mohammad Reza ; Rahimian Mohammad Hassan ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 16~23
The objective of this research is to estimate two dimensional ablating and charring of heat shield materials in severe aero-thermal heat transfer. This estimation requires an accurate and rapid technique for its serious heat transfer with a moving boundary. Aerodynamic heating is obtained by an explicit relation which is a function of Mach number and air condition, while a fully implicit method is used for heat transfer calculations. Moving boundary is captured by FLIAR method which is a subgroup of VOF. Thickness of ablating and charring of heat shield, temperature of the moving surface and rate of radiation heat are calculated and compared with references. The results are in good agreement with other calculations.
UNSTRUCTURED MOVING-GRID FINITE-VOLUME METHOD FOR UNSTEADY SHOCKED FLOWS
Yamakawa M ; Matsuno K ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 24~30
Unstructured grid system is suitable for flows of complex geometries. For problems with moving boundary walls, the grid system must be time-dependently changing and deforming according to the movement of the boundaries when we use a body fitted grid system. In this paper, a new moving-grid finite-volume method on unstructured grid system is proposed and developed for unsteady compressible flows with shock waves. To assure geometric conservation laws on moving grid system, a control volume on the space-time unified domain is adopted for estimating numerical flux. The method is described and applied for two-dimensional flows.
NUMERICAL STUDY OF THE FORMATION OF LINEAR DUNES
Zhang Ruyan ; Kan Makiko ; Kawamura Tetuya ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 31~38
Three-dimensional flow over the sand dunes have been studied numerically by using Large-Eddy Simulation (LES) method. In the direction of initial flow and span direction cyclic boundary conditions are imposed for velocity and pressure. The movement of the sand dune which is formed by converging wind direction has been investigated. The numerical method employed in this study can be divided into three parts: (i) calculation of the air flow over the sand dune using standard MAC method with a generalized coordinate system; (ii) estimation of the sand transfer caused by the flow through the friction; (iii) determination of the shape of the sand surface. Since the computational area has been changed due to step (iii), (i)-(iii) are repeated. The simulated dune, which has initially elliptic cross section, extends at the converging direction, which is known as linear dunes.
NUMERICAL ANALYSIS OF INTERACTION BETWEEN SUPERSONIC JET AND PERPENDICULAR PLATE
Yasunobu T ; Matsuoka T ; Kashimura H ; Setoguchi T ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 39~44
The numerical investigation of the interaction between the underexpanded supersonic jet and the perpendicular plate is carried out using the TVD numerical method. The wave structure in the flowfield and the pressure and temperature distributions on the plate surface are obtained by the numerical analysis. Especially, the influence of self-induced flow oscillation caused by the impinging jet and the characteristic of impinging jet are shown. From the result of the numerical analysis, it is concluded that the pressure and the temperature fluctuations on the plate surface strongly depends on the pressure ratio in the flowfield and the position of plate.
NUMERICAL SIMULATION AND VISUALIZATION OF THE FLOW AROUND THE DARIUS WIND TURBINE
Lee Mi Young ; Kawamura Tetuya ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 45~50
A fundamental understanding of the flow around the wind turbine is important to investigate the performance of new type of wind turbine. This study presents the simulation of three dimensional flow fields around the Darius wind turbine as an example. Incompressible Navier-Stokes equations are used for this simulation. The rotating coordinate system that rotates in the same speed of the turbine is used in order to simplify the boundary condition on the blades. Additionally, the boundary fitted coordinate system is employed in order to express the shape of the blades precisely. Fractional step method is used to solve the basic equations. Third order upwind scheme is chosen for the approximation of the non-linear terms since it can compute the flow field stably even at high Reynolds number without any turbulence models. The flow fields obtained in this study are highly complex due to the three dimensionality and are visualized effectively by using the technique of the computer graphics.
A SENSITIVITY STUDY OF THE DISTORTED INLET FLOW IN AXIAL TURBOMACHINERY WITH NOVEL INTEGRAL SCHEME
Ng Eddie Yin-Kwee ; Liu Ningyu ; Lim Hong Ngiap ; Tan Daniel ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 51~55
For proper installation, operation and performance of axial flow jet engines in aircrafts, the impacts and effects of inlet flow distortion in axial compressors have to be understood. Inlet distortion conditions may cause component-mismatch and instability problems known as rotating stall, and severe oscillations of mass flow rate called surge or a combination of both. Typical effects of this phenomenon include stresses and wear on the compressor blading, destruction of entire jet engines due to the failure of airfoil and mechanical failure or interruption of the combustion process. Therefore, it is important to study inlet flow distortion and its propagation effects to minimize and hence to prevent the occurrence of such calamity. The current novel integral method with parametric analysis signifies its validity to this field of research and offers much potential for further improvements. The present effort further indicates that this simple method may be flourishing in the problems of strongly distorted flow and propagating stall in axial compressor. It is therefore believe that using a more realistic and flexible velocity and pressure profiles could develop this approach further.
LARGE EDDY SIMULATION OF VORTEXING FLOW IN THE MOLD WITH DC MAGNETIC FIELD
Zhongdong Qian ; Yulin Wu ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 56~62
Large eddy simulation of vortexing flow of molten steel in the continuous casting mold with and without DC magnetic field was conducted. The influence of the position of magnetic field to the residence time and depth of the vortex was analyzed. The mechanism of the influence of magnetic field to the vortexing flow was found. The computational results show that the vortexing flow is the result of shearing of the two un-symmetric surface flows from the mold narrow faces when they meet adjacent to the SEN; the un-symmetric flow for turbulent vortex is caused by turbulent energy of the fluid and that for biased vortex is caused by biased flow and the turbulent energy of fluid; with the moving of the magnetic field from the centerline of the outlet of the SEN to the free surface, the surface velocity is decreased gradually and the depth of the turbulent vortex and the biased vortex is decreased, the residence time is increased with the magnetic field moves from DL=120mm to DL=60mm and then decreased; the turbulent vortex and the biased vortex can be eliminated when the magnetic field is located at the free surface.
PERFORMANCE ANALYSIS OF THE TURBULENCE MODELS FOR A TURBULENT FLOW IN A TRIANGULAR ROD BUNDLE
In W.K ; Chun T.H ; Myong H.K ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 63~66
A computational fluid dynamics(CFD) analysis has been made for fully developed turbulent flow in a triangular bare rod bundle with a pitch to diameter ratio (P/D) of 1.123. The nonlinear turbulence models predicted the turbulence-driven secondary flow in the triangular subchannel. The nonlinear quadratic κ-ε models by Speziale and Myong-Kasagi predicted turbulence structure in the rod bundle fairly well. The nonlinear quadratic and cubic k-ε models by Shih et al. and Craft et al. showed somewhat weaker anisotropic turbulence. The differential Reynolds stress model by Launder et al.[5} appeared to over predict the turbulence anisotropy in the rod bundle.
PARALLEL ALGORITHMS FOR INTEGRATION OF NAVIER-STOKES EQUATIONS BASED ON THE ITERATIVE SPACE-MARCHING METHOD
Skurin Leonid I. ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 67~72
This research is based on the iterative space-marching method for incompressible and compressible Navier-Stokes equations[1-4]. A principle of parallel computational schemes construction for steady and unsteady problems is suggested. It is analytically proven that convergence of these schemes is unconditional for incompressible case. When the parallel scheme is used the total volume of computations is the sum of a large number of independent and equal parts. Estimation of the speed-up K shows that K > 1000 in ideal case. First results of using the parallel schemes are presented.
NUMERICAL INVESTIGATION ON BOTTOM GAP OF MICRO FLOW SENSOR
Abdullahl Mohd Zulkiefly ; Kouta T ; Kamijo Takuma ; Yamamoto Makoto ; Honami Shinji ; Kamiunten Shoji ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 73~79
Micro sensor is very useful for flow measurements in a number of engineering applications. Especially, it is necessary for the development of MEMS. This paper presents the 3D numerical simulation of flows around a micro flow sensor, which is mounted on a flat plate. The effects of the sensor configuration (i.e. bottom gap) and the Reynolds number on the flow field are numerically investigated. The numerical results indicate that the bottom gap clearly affects the flow fields over the top surface of the sensor. The Reynolds numbers also show a significant influence on the flow nature, especially on the recirculation zone at downstream of the sensor. The present results illustrate a certain improvement on the flow field for the sensor installed at O.5mm above the wall with four pillars, comparing with that directly mounted on the wall
PASSlVE SHOCK CONTROL IN TRANSONIC FLOW FIELD
Matsuo S ; Tanaka M ; Setoguchi T ; Kashimura H ; Yasunobu T ; Kim H.D ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 80~86
In order to control the transonic flow field with a shock wave, a condensing flow was produced by an expansion of moist air on a circular bump model and shock waves were occurred in the supersonic parts of the fields. Furthermore, the additional passive technique of shock-boundary layer interaction using the porous wall with a cavity underneath was adopted in this flow field. The effects of these methods on the shock wave characteristics were investigated numerically. The result showed that the flow fields might be effectively controlled by the suitable combination between non-equilibrium condensation and the position of porous wall.
A NUMERICAL INVESTIGATION OF INDOOR AIR QUALITY WITH CFD
Sin Vai Kuong ; Sun Ho I ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 87~93
Macao, a city with three sides bounded by water, is hot and humid in weather in more than six months of a year. This uncomfortable weather induces the frequency of operating air-conditioners. Choice of location for installation of air-conditioner in a building will affect the performance of cooling effect and thermal comfort on the occupants, which in turn will affect the indoor air quality (IAQ) of the building. In the paper, investigation of distribution on carbon dioxide, room air temperature and velocity, as well as air diffusion performance index (ADPI) of a single bedroom in Macao is studied by using the computational fluid dynamics (CFD) software FLOVENT 3.2. Simulations of locating the air-conditioner at 4 different walls will be done and comparisons and analyses of the results will be performed to decide a proper location for the air-conditioner for obtaining good thermal comfort.
CHARACTERISTICS OF SMOKE CONCENTRATION PROFILES WITH UNDERGROUND UTILITY TUNNEL FIRE
Kim Hong Sik ; Hwang In Ju ; Kim Youn-Jea ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 94~98
Accurate prediction of the fire-induced air velocity, temperature and smoke flow in underground utility tunnel becomes more important for the optimization of design and placement of heat and smoke detectors. In order to improve the safety of underground utility tunnel systems, the behaviors of fire-induced smoke flow and temperature distributions are investigated. Especially, two different cross-sectional shapes of tunnel, such as rectangular and circular types are modeled. Also, fire source is modeled as a volumetric heat source. Three-dimensional thermal-flow characteristics in an underground tunnel are solved by means of FVM using SIMPLE algorithm. The effects of shape geometry on the fire-induced flow characteristics are graphically depicted. It is desirable that heat and smoke detectors are installed on the cables and the top of the wall.
PERFORMANCE OF TWO DIFFERENT HIGH-ACCURACY UPWIND SCHEMES IN INVISCID COMPRESSIBLE FLOW FIELDS
Hosseini R ; Rahimian M.H ; Mirzaee M ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 99~106
Performance of first, second and third order accurate methods for calculation of in viscid fluxes in fluid flow governing equations are investigated here. For the purpose, an upwind method based on Roe's scheme is used to solve 2-dimensional Euler equations. To increase the accuracy of the method two different schemes are applied. The first one is a second and third order upwind-based algorithm with the MUSCL extrapolation Van Leer (1979), based on primitive variables. The other one is an upwind-based algorithm with the Chakravarthy extrapolation to the fluxes of mass, momentum and energy. The results show that the thickness of shock layer in the third order accuracy is less than its value in second order. Moreover, applying limiter eliminates the oscillations near the shock while increases the thickness of shock layer especially in MUSCL method using Van Albada limiter.
ANALYSES ON FLOW FIELDS AND PERFORMANCE OF A CROSS-FLOW FAN WITH VARIOUS SETTING ANGLES OF A STABILIZER
Kim D. W. ; Kim H. S. ; Park S. K. ; Kim Youn J ;
Journal of computational fluids engineering, volume 10, issue 1, 2005, Pages 107~112
A cross-flow fan is generally used on the region within the low static pressure difference and the high flow rate. It relatively makes high dynamic pressure at low rotating speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. At off-design points, there are a rapid pressure head reduction, a noise increase and an unsteady flow. Those phenomena are remarkably influenced by the setting angle of a stabilizer. Therefore, it should be considered how the setting angle of a stabilizer affects on the performance and the flow fields of a cross-flow fan. It is also required to investigate the effect of the volumetric flow rate before occurring stall. Two-dimensional, unsteady governing equations are solved using a commercial code, STAR-CD, which uses FVM. PISO algorithm, sliding grid system and standard k - ε turbulence model are also adopted. Pressure and velocity profiles with various setting angles are graphically depicted. Furthermore, the meridional velocity profiles around the impeller are plotted with different flow rates for a given rotating speed.