• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.115-121
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• 2010

Cavitating flow is widely shown in many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work focuses on the numerical analysis of the multiphase flow around the underwater vehicle which was launched from a submarine. The governing equation is the Navier-Stokes equation with a homogeneous mixture mode. The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinate. For the code validation, the results from the present work are compared with the existing experimental and numerical results, and a reasonably good agrements are obtained. The multiphase flow around an underwater vehicle is simulated which includes submarine wake effects.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.294-299
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• 2001

An experimental study was made of turbulent separated and reattaching flow over a blunt body, where unsteady wake was generated by a spoke wheel-type wake generator with cylindrical rods. The influence of unsteady wake was scrutinized by altering the rotating direction (CW and CCW) and the normalized passing frequency $(0{\leq}St_H{\leq}0.20)$. The Reynolds number based on the cylindrical rod was $Re_d=375$. A phase-averaging technique was employed to characterize the unsteady wake. The effect of different rotating directions was examined in detail, which gave a significant reduction of $X_R$. The wall pressure fluctuations on the blunt body were analyzed in terms of the spectrum and the coherence.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.353-361
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• 2002

An experimental study was made of turbulent separated and reattaching flow over a blunt body, where unsteady wake was generated by a spoke wheel-type wake generator with cylindrical rods. The influence of unsteady wake was scrutinized by altering the rotating direction (CW and CCW) and the normalized passing frequency (0 St$\_$H/ 0.20). The Reynolds number based on the cylindrical rod was Re$\_$d/=375. A phase-averaging technique was employed to characterize the unsteady wake. The effect of different rotating directions was examined in detail, which gave a significant reduction of x$\_$R/. The wall pressure fluctuations on the blunt body were analysed in terms of the spectrum and the coherence.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.1
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• pp.12-19
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• 2022

The exhaust wake of an aircraft engine is discharged in a high temperature and high speed, which can damage objects such as an aircraft in the rear. The exhaust wake can lift small foreign substances lying on the ground or falling off, and the floating foreign substances can enter the intake duct of the aircraft moving from the rear and cause engine FOD (Foreign Object Damage). This study experimentally analyzed how the engine exhaust wake generated from military jet fighters affects the movement of foreign substances and evaluated the effects of foreign substances on the damaged area by measuring wake velocity. The simulation and field experimental results confirmed that the effect of exhaust wake increases as the rear position closer, and that foreign substances lifted by the wake can act as FOD to the adjacent rear aircraft.

• Journal of Wind Energy
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• v.4 no.1
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• pp.68-74
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• 2013

Offshore wind farm is being increased since there are much trouble to develop onshore wind farm. But in the offshore, wind turbine wake does not dissipate less than onshore wind turbine because of low turbulence level. Thus this remained wake interacted to other wind turbine. This interaction reduces energy production in wind farm and have a bad influence on fatigue load of wind turbine. In this research, CFD model was constructed to analyze wake effect in offshore wind farm. A method that wind turbine rotor region was modelled in porous media was devised to reduce computation load and validated by comparison with Horns Rev measurement. Then wake interaction between two wind turbine was analyzed by devised porous model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.4
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• pp.315-320
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• 2008

This paper describes aerodynamic characteristics for the NREL(National Renewable Energy Laboratory) Phase VI rotor using the Fluent which is a commercial flow analysis tool. Aerodynamic analysis results are compared with experimental results by the NREL/NASA Ames wind tunnel tests. For three velocity cases, computed results are compared with experiment results at five spanwise positions. Computed results represented good agreement with the experimental results at low velocity. Otherwise computed results in suction side represents disagreement with the experimental results at high velocity. When interval between wind turbines is 10 times of rotor diameter, CFD research is performed to calculate the wake effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.695-702
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• 2008

Flow instability in the rocket turbo pump systems can be caused by various elements such as valve, orifice and venturi and etc. The formation of cavitation specially in the propellant feeding system can trigger the mass flow and pressure oscillation due to cyclic formation and depletion of cavitations. If the cryogenic propellant are used, which is very sensitive to temperature variation, the change of propellant properties due to thermodynamic effect should be accounted for in the flow analysis. This study focuses on the formation of cryogenic cavitation adopting MUSHY IDM model suggested by Shyy and coworkers. Also, the flow instability is investigated with developed numerical code in the downstream of orifice flow. To this end, three different orifices are selected and investigated by the numerical calculation.

• 한국항공운항학회:학술대회논문집
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• 2005.11a
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• pp.155-159
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• 2005

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.1-11
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• 2020

Behaviors of wake vortices generated by an aircraft affect the performance and flight stability of flying aircraft in formation flight. In the present study, the trajectories of the wake vortices behind airplanes in close formation flight were computed using a Fourier spectral method. The behavior of wake vortices showed complex patterns depending on the initial circulation and the relative positions between the vortices. In the initial stage, the wake vortex movement was affected by the nascent vortex. When the vortex becomes closer to the other vortex, then a new trajectory is formed. When the viscous effect becomes dominant, the core radius increases. Thus, a new vortex moving near the existing vortex can have strong interaction with each other, resulting in the complicated behavior of wake vortices. In the future, the ground effect on the behavior of the wake vortices during take-off and landing will be studied.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.209-215
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• 2017

A large floating offshore wind-wave hybrid power generation system with an area of 150 m2 and four 3 MW class wind turbine generators was installed at each column top. In accordance with the wind turbine arrangement, the wake generated from upstream turbines can adversely affect the power performance and load characteristics of downstream turbines. Therefore, an optimal arrangement design, obtained through a detailed flow analysis focusing on wake interference, is necessary. In this study, to determine the power characteristics and annual energy production (AEP) of individual wind turbines, transient computational fluid dynamics, considering wind velocity variation (8 m/s, 11.7 m/s, 19 m/s, and 25 m/s), was conducted under different platform conditions ($0^{\circ}$, $22.5^{\circ}$, and $45^{\circ}$). The AEP was calculated using a Rayleigh distribution, depending on the wind turbine arrangement. In addition, we suggested an optimal arrangement design to minimize wake losses, based on the AEP.