• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.131-136
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• 1996

The numerical method for the flow field of a gas atomization process is presented. For the analysis of the compressible supersonic jet flow of a gas. an axisymmetric Navier-Stokes equations are solved using a LU-factored upwind method. The MUSCL type TVD scheme is used for the discretization of inviscid flux, whereas Steger-Warming splitting and LU factorization is applied to the implicit operator. For the validation of the present method, we computed the flow field around the simple gas atomizer proposed by Issac. The numerical results has shown excellent agreement with the experimental data.

• Journal of KSNVE
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• v.11 no.2
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• pp.241-248
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• 2001

The present paper describes experimental and computational work to augment the magnitude of the impulsive wave. An experiment was performed using a simple shock tube with an open end and numerical calculations were carried out to solve the unsteady, axisymmetric, inviscid, compressible governing equations. The control strategy applied was to alter the exit geometry of a straight tube to a sudden enlargement tube and a flare tube. The effects of the configurations of the tube exit on the magnitude of the impulsive wave were investigated over the range of the weak shock Mach number from 1.01 to 1.10. The results obtained were compared to those of the straight tube tests. The numerical result predicted the magnitude of the experimented impulsive waves with a good accuracy. The present passive control technique enabled the magnitude of the impulsive wave to augment by about 23 percent, compared to that of the straight tube of no control.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3272-3281
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• 1996

The flow analysis method which had been developed for the numerical calculation of 3-dimensional, incompressible and turbulent flow within an axial compressor was extended to the flow field within centrifugal impeller. In this method based on the SIMPLE(Semi Implicit Method Pressure Linked Equations) algorithm, the coordinate transformation was adopted and the standard k-.epsilon. model using wall function was used for turbulent flow analysis. The calculated flow fields have agreed very well with measurement results. Especially, 3-dimensional and viscous flow characteristics including secondary flows, jet-wake flow and decreased pressure rise along impeller passage, which can't be predicted by inviscid Q3D calculation were predicted very reasonably.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.1994-2004
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• 1996

Numerical calculation was applied to supersonic under-expanded jets, and compared with the results of a linear theory and other experiments. TVD difference scheme was employed to solve 2-dimensional and axisymmetric inviscid Euler equation. This paper aims to explore the effects of angle of divergence and design Mach number of nozzle on the structure of under-expanded jets. The angle of divergence was varied from 0 to 20 deg. The results show that the length of the first cell of the under-expanded jets decreases and Mach disk generates at lower nozzle pressure ratio, if the angle of divergence or design Mach number of nozzle increases. The distance from the nozzle exit to Mach disk in 2-dimensional jets becomes much larger than that of axisymmetric jets, and the widths of the jet boundary and the barrel shock wave are also larger than that of axisymmetric jets. Calculation results indicate that the configuration of the under-expanded jets is strongly dependent on the nozzle pressure ratio.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.279-283
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• 2002

The effects of finite gap at the tip of turbomachinery blades have long been topics of both theoretical and experimental research because tip clearance degrades turbomachinery performance. This paper presents an analytical study of radial flow redistribution in a high speed compressor stage with axisymmetric tip clearance. The flow is assumed to be inviscid and compressible. The stage is modeled as an actuator disc and the analysis is carried out in the meridional plane. Upon going through the stage, the radially uniform upstream flow splits into the tip clearance and passage flows. The tip clearance flow is modeled as a jet driven by blade loading, or pressure difference between the pressure and suction sides. The model takes into consideration the detached shocks which occur in the rotor passage at the design point. This shock model is used to calculate the density ratio across the stage. Thus, the model is capable of predicting the kinematic effects of tip clearance in the high speed compressor flow field.

• Journal of computational fluids engineering
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• v.6 no.2
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• pp.1-8
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• 2001

Despite the massive effort which has been given to the analysis of the base flows, one commonly occurring case seems to be overlooked. This is for base (rearward facing surface) which is between a subsonic flow and supersonic flow. Potential flows of the air and gas streams are computed for the flow past a separated wake. Then a viscous jet mixing is superimposed on this inviscid solution. Conservation of mass, momentum and energy is achieved by multiple iterations. Despite the iterations, the wake flow field is computed with modest computer requirements.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.36-41
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• 2011

Numerical simulation of air-launched rockets from a helicopter was conducted to investigate the aerodynamic interference between air-launched rocket and helicopter. For this purpose, a three-dimensional inviscid flow solver has been developed based on unstructured meshes. An overset mesh technique was used to describe the relative motion between rocket and rocket launcher. The flow solver was coupled with six degree-of-freedom equation to predict the trajectory of free-flight rockets. For the validation, calculations were made for the impinging jet with inclined plate. The rotor downwash of helicopter was calculated and applied to simulation of air-launched rocket. It is shown that the rotor downwash has non-negligible effect on the air-launched rocket and its plume development.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.277-280
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• 2006

This paper describes the aerodynamic interference characteristics between the ing and the engines in a commercial airplane which is realized by reverse engineering based on the photo measurement. Steady three-dimensional compressible inviscid Euler equation is solved in the unstructured grid system under the cruise condition. The lift and drag forces in the wing with engines increase by 1.49% and 3.9%, respectively compared with the wing without engines.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.1-1
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• 2010

With the power of supercomputers increasing exponentially, there is an insatiable need for more advanced multi-disciplinary aerospace CFD simulations. A particular current interest is the 3D viscous turbulent simulation of the highly nonlinear aspects of aero-icing. The applications of CFD in that field are literally light-years behind aerodynamics, with a significant number of users still mired in correlations, or 2D, inviscid, incompressible, and, yes, Panel Methods simulations! Thus, the disparity of tools between aerodynamics and icing departments within an organization leads to a disconnect that makes ice protection a downstream isolated process that is not an integral part of the aerodynamic behavior of an aerospace system (aircraft, rotorcraft, jet engine, UAV, etc.). While 3D RANS has been recently introduced, it is still considered computationally too demanding for industry when wide parametric studies for certification are required. In addition, not unlike the situation in aerodynamics say 20 years ago, naysayers are at every corner claiming that CFD is not reliable and is of limited use.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.145-150
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• 2004

In this study the numerical analysis on staging flow with forward ejector is conducted. The forward ejector plays a vital role in staging, which jets out from aftbody. This staging environment needs careful flow analysis for securing staging safety Present study investigates the steady inviscid staging flow phenomena with variation of separation distance. The performance index is forebody base pressure coefficients. The three dominant flow phenomena are observed according to separation distance which could be told as impinging stage, cavity vortex dominancy stage, and pure base flow characteristics stage. Impinging stage shows high thrust for forebody as one might think. However, important point is that cavity vortex dominancy stage can be more favorable for separation than impinging stage as one simply think in certain separation distance.