• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.12
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• pp.913-919
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• 2015

A supercavitating vehicle has a speed of more than 300 km/h in water. A numerical analysis of the flow around a supercavitating vehicle must deal with a multiphase flow consisting of the water, vapor and exhaust gas because the vehicle is powered by roket propulsion. The effect of the exhaust gas on the vehicle is an important part in the study of the performance of the supercavitating vehicle. In the present study, the effect of the exhaust gas on the drag of vehicle was investigated by conducting numerical analysis. When there is no exhaust gas, drag of vehicle is affected by re-entrant. In the case with rocket propulsion, the exhaust gas reduces the influence of re-entrant. The exhaust gas also creates Mach disk and it changes drag profile.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.383-387
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• 2011

The supercavitating rocket torpedo SHKVAL was analyzed in view of its system operation procedure and the structure and performance. 3 different propulsion systems installed in SHKVAL were 1st solid rocket booster for launch and acceleration, 2nd solid rocket booster for further acceleration, and Mg-rich Hydroreactive fuel rocket propulsion system for cruising. The gas generator used to help generate the supercavitation bubble was composed of a solid propellant gas generator and a hydroreactive fuel one. The structures and their performance were described based on as much knowledge as we have obtained from cumulative information and up-to-date analysis.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.214-224
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• 2021

Recently, as the technology of the supercavitating underwater vehicle is improved, the necessity of research for maneuvering characteristics of the supercavitating underwater vehicle has emerged. In this study, as a preliminary step to analyzing the maneuverability of a supercavitating underwater vehicle, the characteristics of cavity shapes and hydrodynamic forces generated in a supercavitating underwater vehicle with an angle of attack were evaluated numerically. First, the geometry was designed by modifying the shape of the existing supercavitating underwater vehicle. The continuity and the Navier-stokes equations are numerically solved, and turbulent eddy viscosity is solved by the k-ω SST model. The results present the characteristics of cavity shape and the hydrodynamic forces of the designed geometry with an angle of attack.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.82-85
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• 2008

When a projectile travels at high speed underwater, supercavitating flowarises, in which a huge cavity is generated behind the projectile so that only the nose, i.e., the cavitator, of the projectile is wetted, while the rest of it should be surrounded by the cavity. In that case, the projectile can achieve very high speed due to the reduced drag. Furthermore if the nose of the body is shaped properly, the attendant pressure drag can be maintained at a very low value, so that the overall drag is also reduced dramatically. In this study, shape optimization technique is employed to determine the optimum cavitator shape for minimum drag, given certain operating conditions. Simultaneous optimization technique is proposed for efficient cavitator shape optimization, in which the cavity and cavitator shape are determined in a single optimization routine.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.188-192
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• 2009

A massive cavity is generated behind the underwater vehicles, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. when a underwater vehicle moves at very high speed in the underwater. At this point it makes supercavitating flow and the nose, ie., the cavitator is very important fator at the vehicle since it should be surrounded by the cavity. The present work has focused on the simulation of cavitation flow using the new cavitator. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. For the code validation, the results from the present solver have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained.

• Journal of Ocean Engineering and Technology
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• v.31 no.1
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• pp.8-13
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• 2017

Cavitation is used in various fields. This study examined the drag reduction of an underwater vehicle using cavitation. In this study, the natural partial cavitation analysis results were verified using CFD code with the Navier-Stokes equation based on a mixture model. The momentum and continuity equations in the mixture phase were separately solved in the liquid and vapor phases. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The results of a computational analysis showed good agreement with the experiment. A computational analysis was also performed on the supercavity. The study investigated the cavity characteristics and drag of an underwater vehicle and studied the speed required to achieve a supercavity. Finally, a 1DOF analysis was carried out to investigate the thrust system for a supercavity. As a result, one of the methods for determining a suitable thrust system for a supercavitating underwater vehicle was presented.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.300-308
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• 2015

Recently supercavitating underwater torpedo moving at high speed (over 200 knots) has been interested for their practical advantage of the dramatic drag reduction. Cavitator located in front of the torpedo plays an important role to generate a natural supercavity and control the motion of the object. Supercavity can be created artificially by injection of compressed gas from the rear of the cavitator at a relatively low speed. In this paper, we investigated physical characteristics of artificial supercavities through cavitation tunnel experiments. One of the main focuses of the study was to measure pressure inside the cavity, and examined variation of the gravity effects appearing according to different amount of injected air. It was also found that a stable supercavity could be sustained at injection rates less than that required to form the stable supercavity because of hysteresis effect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.797-805
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• 2014

The purpose of this study was to investigate the drag and lift characteristics of the cavitator of a supercavitating underwater vehicle and the pressure loss due to water intake. These investigations were performed by changing the diameter, velocity, radius of curvature of the intake, and angle of attack of the cavitator. With increasing ratio of the intake diameter to the cavitator diameter ratio($d/D_1$), the drag coefficient and the pressure loss coefficient of the water intake decreased. The greater the increase in the ratio of the intake velocity-to-free stream velocity ratio(S), the smaller was the decrease in the drag coefficient and the lift coefficient. When the intake had a radius of curvature(c), the pressure loss coefficient decreased. On the contrary, the effect of the radius of curvature on the drag coefficient was imperceptible. For angles of attack (${\alpha}$) of the caviatator in the range of $0^{\circ}$ to $10^{\circ}$, the drag coefficient and the pressure loss coefficient changed slightly, whereas the lift coefficient increased linearly with increasing angle of attack.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.867-880
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• 2013

The development for a high speed underwater vehicle has been demanded for a long time, and it is possible to realize using supercavitation. This paper introduces the main technologies that are necessary to develop a supercavitating rocket system, such as "Supercavitation" and "Hydroreactive technology", and describes the operating concepts and principles for its components specifically. Russia has obtained the key technologies of supercavitation and hydroreactive fuel technology for the first time. Russia has developed a supercavitating rocket torpedo, Shkval, and it was in service since 90's. Iran collaborated with Russia to develop a supercavitating rocket torpedo 'Hoot' and finished a test recently. This paper describes the analysis results related with the cavitator based on the technical reports for Shkval of Russia and Hoot of Iran.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.88-98
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• 2014

A supercavitation is modern technology that can be used to reduce the frictional resistance of the underwater vehicle. In the process of reaching the supercavity condition which cavity envelops whole vehicle body, a vehicle passes through transition phase from fully-wetted to supercaviting operation. During this phase of flight, unsteady hydrodynamic forces and moments are created by partial cavity. In this paper, analytical and numerical investigations into the dynamics of supercavitating vehicle in transition phase are presented. The ventilated cavity model is used to lead rapid supercavity condition, when the cavitation number is relatively high. Immersion depth of fins and body, which is decided by the cavity profile, is calculated to determine hydrodynamical effects on the body. Additionally, the frictional drag reduction associated by the downstream flow is considered. Numerical simulation for depth tracking control is performed to verify modeling quality using PID controller. Depth command is transformed to attitude control using double loop control structure.