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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 18, Issue 4 - Dec 2013
Volume 18, Issue 3 - Sep 2013
Volume 18, Issue 2 - Jun 2013
Volume 18, Issue 1 - Mar 2013
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A NUMERICAL STUDY ON THE HEAT AND FLUID FLOW IN A REGENERATIVE OXY-FUEL COMBUSTION SYSTEM
Kang, K. ; Hong, S.K. ; Noh, D.S. ; Ryou, H.S. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 1~7
DOI : 10.6112/kscfe.2013.18.3.001
A pure oxygen combustion technology is crucial in Carbon Capture and Storage (CCS) technology especially in capturing of
, where CCS will reduce 9
by 2050, which is 19% of the total
reduction amount. To make pure oxygen combustion feasible, a regenerative system is required to enhance the efficiency of pure oxygen combustion system. However, an existing air combustion technology is not directly applicable due to the absence of nitrogen that occupies the 78% of air. This study, therefore, investigates the heat and fluid flow in a regenerative system for pure oxygen combustion by using commercial CFD software, FLUENT. Our regenerative system is composed of aluminium packed spheres. The effect of the amount of packed spheres in regenerator and the effect of presence or absence of a bypass of exhaust gas are investigated. The more thermal mass in regenerator makes the steady-state time longer and temperature variation between heating and regenerating cycle smaller. In the case of absence of bypass, the regenerator saturates because of enthalpy imbalance between exhaust gas and oxygen. We find that 40% of exhaust gas is to be bypassed to prevent the saturation of regenerator.
A NUMERICAL STUDY ON THE EFFECT OF DOWN-WASH OF A WING-BODY ON ITS AERODYNAMIC CHARACTERISTICS
Yoon, K.H. ; Kim, C.H. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 8~13
DOI : 10.6112/kscfe.2013.18.3.008
Drag reduction of a running vehicle is very important issue for the energy savings and emission reduction of its power train. Especially for a solar powered electric vehicle, the drag reduction and weight lightening are two serious problems to be solved to extend its driving distance under the given energy condition. In this study, the ground effect of an airfoil shaped road vehicle was studied for an optimum body design of an ultra-light solar powered electric vehicle. Clark-Y airfoil type was adopted to the body shape of the model vehicle to reduce aerodynamic drag. From the study, it was found that the drag of the model vehicle was reduced as the height(h) between ground and the lower surface of the model vehicle was decreased. It is due to the reduction of the down-wash decreasing the induced drag of the vehicle. The lift was also decreased as the height decreased. It is due to the turbulent boundary layer developed beneath the vehicle body. The drag is classified into two types; the form and friction drag. The fraction of form drag to friction one is 76 to 24 on the model vehicle. As the height(h) of the model vehicle from the ground surface increases the form drag also increases but the friction drag is in reverse.
NUMERICAL ANALYSIS ON THE BLOOD FLOW CHARACTERISTIC IN THE ARTERIOVENOUS GRAFT FOR DIFFERENT INJECTION METHOD OF BLOOD
Kim, J.T. ; Sung, K.H. ; Ryou, H.S. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 14~19
DOI : 10.6112/kscfe.2013.18.3.014
Renal failure patients have to operate arteriovenous graft for hemodialysis. Blood flow characteristics influence the patency rate of arteriovenous graft. Numerical investigation is performed with the arteriovenous graft according to injection of blood. As a result, when the injection is not applied to venous graft, the low wall shear stress region appears at venous anastomosis. It may cause intimal hyperplasia at venous anastomosis.
COUPLED ANALYSIS OF INJECTION MOLDING AND FILM FORMING FOR IDENTIFYING FILM DEFORMATION IN IMD PROCESS
Yoon, J.H. ; Hur, N. ; Bae, A.H. ; Lee, T.H. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 20~25
DOI : 10.6112/kscfe.2013.18.3.020
In various manufacturing industries, an in-mold decoration (IMD) process for plastic objects is widely utilized because a film forming and an injection molding processes run simultaneously. In the present study, the deformation of polymer film and filling of resin in the IMD process were numerically investigated to evaluate the quality of the plastic object formed by the IMD process, which consists of thermoforming and injection molding processes. To obtain the initial shape of the polymer film during the injection molding process, the deformation of the polymer film in the thermoforming process was pre-formed using the vacuum conditions to attach the film to a cavity. Since the properties and deformation of polymer film are greatly affected by the behavior of polymer resin being injected into a mold cavity, numerical simulations for the injection molding and film forming were performed with one-way coupling method. The results showed that the injected resin could lead to the tearing of the polymer film in local regions near the corners. In order to verify the proposed numerical methodology, the numerical results of the deformation patterns printed on the initial polymer film were compared with the experimental data. The proposed methodology to couple film forming analysis with injection molding analysis can be used to predict the deformation of film in IMD process.
NUMERICAL STUDY OF VARIABLE GEOMETRY NOZZLE FLOW USING A MESH DEFORMATION TECHNIQUE ON HYBRID UNSTRUCTURED MESHES
Kim, J.W. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 26~33
DOI : 10.6112/kscfe.2013.18.3.026
In the present study, unsteady flow simulations of a variable geometry nozzle were conducted using a two-dimensional flow solver based on hybrid unstructured meshes. The variable geometry nozzle is used to achieve efficient performances of aircraft engines at various operating conditions. To describe the motion of the variable geometry nozzle, an algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements. A ball-vertex spring analogy was used for inviscid elements. The aerodynamic data were obtained for a range of nozzle pressure ratios, and the validations were made by comparing the present results with available experimental data. The unsteady nozzle flows were simulated with an oscillating diverging section and a converging-diverging section. It was found that the nozzle performances are influenced by the nozzle exit flow characteristics, mass flow rate, as well as unsteady effects. These unsteady effects are shown to behave differently depending on the frequency of the nozzle motion.
AN IMMERSED BOUNDARY METHOD FOR LOW REYNOLDS NUMBER FLOWS
Park, Hyun Wook ; Lee, Changhoon ; Choi, Jung-Il ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 34~41
DOI : 10.6112/kscfe.2013.18.3.034
We develop a novel immersed boundary (IB) method based on implicit direct forcing scheme for incompressible flows. The proposed IB method is based on an iterative procedure for calculating the direct forcing coupled with the momentum equations in order to satisfy no-slip boundary conditions on IB surfaces. We perform simulations of two-dimensional flows over a circular cylinder for low and moderate Reynolds numbers. The present method shows that the errors for estimated velocities on IB surfaces are significantly reduced even for low Reynolds number with a fairly large time step while the previous methods based on direct forcing failed to provide no-slip boundary conditions on IB surfaces.
THE ANALYSIS OF AERODYNAMIC CHARACTERISTICS FOR BUSEMANN BIPLANE WITH FLAP
Tai, Myungsik ; Son, Chankyu ; Oh, Sejong ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 42~50
DOI : 10.6112/kscfe.2013.18.3.042
The supersonic airplane with flapped biplane, Busemann biplane equipped flap, is superior to drag and noise reduction due to wave cancelation effect between upper and lower airfoils. In this study, it is numerically calculated and analyzed the lift, drag and lift to drag ratio of flapped biplane with respect to various the length and angle of the flap. Euler solver of EDISON CFD, web based computational fluid dynamic solver for the purpose of education, is employed. Depending on the length of the flap, lift and drag increase linearly, and there exists the optimum flap angle which maximize the lift-to-drag ratio at the freestream mach 2.0 on-design condition. The predictable relational expression is driven as liner equation. As a results of comparison with drag of flapped biplane, Busemann biplane, and diamond airfoil with the same lift, the drag of flapped biplane is 88.76% lower than that of the Busemann biplane and 70.67% lower than that of the diamond airfoil. In addition, the change of pressure is compared to confirm the noise reduction effect of flapped biplane at h/c=5 of lower airfoil. The shock strength of flapped biplane is smaller than that of other airfoils.
COMPUTATIONAL PREDICTION OF ICING EFFECTS ON AERODYNAMIC CHARACTERISTICS OF A WIND TURBINE BLADE
Park, J.H. ; Jung, K.Y. ; Myong, R.S. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 51~59
DOI : 10.6112/kscfe.2013.18.3.051
A significant change in aerodynamic characteristics of wind turbine blade can occur by ice formed on the surface of the blade operated in cold climate. The ice accretion can result in performance loss, overloading due to delayed stall, and excessive vibration associated with mass imbalance. In this study, the impact of ice accretion on the aerodynamic characteristics of NREL 5MW wind turbine blade sections is examined by a CFD-based method. It is shown that the thickness of ice accretion increases from the root to the tip and the effects of icing conditions such as relative wind velocity play a significant role in the shape of ice accretion. In addition, the computational results are used to assess the degradation in the lift and drag coefficients of the blade sections.
AERODYNAMIC EFFECTS OF THE TAB ON A HOVERING ROTOR BLADE
Kang, H.J. ; Kim, D.H. ; Kim, S.H. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 60~66
DOI : 10.6112/kscfe.2013.18.3.060
Numerical simulation was performed for the rotor blade with fixed tab in hover using an unstructured mesh Navier-Stokes flow solver. The inflow and outflow boundary conditions using 1D momentum and 3D sink theory were applied to reduce computational time. Calculations were performed at several operating conditions of varying collective pitch angle and fixed tab length. The aerodynamic effect of fixed tab length was investigated for hovering efficiency, pitching moment and flapping moment of the rotor blade. The results show that it affects linearly increasing on the pitching moment of the rotor blade but does not affect on the flapping moment. The required power is less than 45kw for ground rotating test in hover. Numerical simulations also show that the vortex generate not only from the tip of the rotor blade but also from the fixed tab on the rotor blade.
APPLICATION OF CFD SIMULATION IN SIC-CVD PROCESS
Kim, J.W. ; Han, Y.S. ; Choi, K. ; Lee, J.H. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 67~71
DOI : 10.6112/kscfe.2013.18.3.067
Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.
LARGE EDDY SIMULATION OF ORDINARY & EMERGENCY VENTILATION FLOW IN UNDERGROUND SUBWAY STATION
Jang, Yong-Jun ; Ryu, Ji-Min ; Park, Duck-Shin ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 72~78
DOI : 10.6112/kscfe.2013.18.3.072
The turbulent flow behavior of air supply and exhaustion in the Shin-gum-ho subway station is analyzed for ordinary and emergency state. The depth of Shin-gum-ho station is 43.6m which consists of the island-type platform(8th floor in underground) and a two-story lobby (first & second floor in underground). An emergency stairway connects between the platform and the lobby. Ventilation operation mode for ordinary state is set up as a combination of air supply and exhaustion in the lobby and platform, while for emergency state it is set up as a full air supply in the lobby and a full exhaustion in the platform. The entire station is covered for simulation. The ventilation diffusers are modeled as 95 square shapes of
in the lobby and as 222 square shapes of
and 4 rectangular shapes of
in the platform. The total of 7.5million grids are generated and whole domain is divided to 22 blocks for MPI efficiency of calculation. Large eddy simulation(LES) is applied to solve the momentum equation and Smagorinsky model(
=0.2) is used as SGS(subgrid scale) model. The time-averaged velocity fields are compared to experimental data and show a good agreement with it.
PRECONDITIONED NAVIER-STOKES COMPUTATION FOR WEAKLY COMPRESSIBLE FLOW ANALYSIS ON UNSTRUCTURED MESH
Son, S.J. ; Ahn, H.T. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 79~86
DOI : 10.6112/kscfe.2013.18.3.079
Preconditioned compressible Navier-Stokes equations are solved for almost incompressible flows. Unstructured meshes are utilized for spatial discretization of complex flow domain. Effectiveness of the current preconditioning algorithm, with respect to various Reynolds numbers and Mach numbers, is demonstrated by the solution of canonical problems for incompressible flows, e.g. driven cavity flows.
NUMERICAL SIMULATION OF THERMOCHEMICAL NON-EQUILIBRIUM FLOW AROUND BLUNT BODIES CONSIDERING CATALYTIC WALL EFFECTS
Kim, J.W. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 87~93
DOI : 10.6112/kscfe.2013.18.3.087
A computational study has been performed to examine the effects of catalytic walls on the stagnation region heat transfer. The boundary conditions for none, finite, and fully catalytic walls have been incorporated into a multi-block compressible Navier-Stokes solver. In the present study, both chemical and thermal non-equilibrium effects were included. The flows over a blunt body model were simulated by varying surface catalytic recombination rates. A full range of catalycities was explored in the context of a constant wall temperature assumption. Detailed information on species concentrations, temperature, and surface heat flux are presented. Comparison with available flight data of surface heat flux is also made.
DEVELOPMENT OF CAVITATION EROSION PREDICTION METHOD AND ITS APPLICATION FOR MARINE PROPELLER
Park, S. ; Rhee, S.H. ;
Journal of computational fluids engineering, volume 18, issue 3, 2013, Pages 94~101
DOI : 10.6112/kscfe.2013.18.3.094
In the present study, a practical method to predict cavitation erosion, which caused a critical damage on hydraulic machineries, was developed. Impact and critical velocities were defined to develop a practical method for the prediction of cavitation erosion. To develope the practical method, the computational fluid dynamics (CFD) was introduced. Cavitating flows with erosion in a converging-diverging nozzle and around a hydrofoil were simulated by developed and validated code. Based on the CFD results, the cavitation erosion coefficient was derived by a curve fitting method. The cavitation erosion coefficient was formulated as the function of the cavitation and Reynolds numbers. A cavitating flow in an axisymmetric nozzle followed by radial divergence was simulated to validate the developed practical method. For the application to a propeller, a cavitating flow around a propeller was simulated. Predicted damage extent showed similar with damaged full-scale propeller blade.