• 대한조선학회논문집
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• 제43권4호
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• pp.399-413
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• 2006

Mathematical model for coupled motions of Manta-type Unmanned Undersea Vehicle(UUV) moving with six degrees of freedom, is formulated. Furthermore, a calculation method for estimating the linear hydrodynamic derivatives acting on UUV, is proposed, and some of the estimated linear hydrodynamic derivatives are compared with results of captive model experiment. Based on linear dynamic model of UUV, a study was made to examine dynamic stability and turning ability in horizontal plane. And directional stability and required elevation rudder angles for neutrally operating in vertical plane, are also discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제16권5호
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• pp.67-76
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• 1992

This paper describes the vibration characteristic of second-order nonlinear systems subjected to parametric excitation. Emphasis is put on the examination of the hydrodynamic nonlinear damping effect on limiting the response amplitudes of parametric vibration. Since the parametric vibration is described by the Mathieu equation, the Mathieu stability chart is examined in this paper. In addition, the steady-state solutions of the nonlinear Mathieu equation in the first instability region are obtained by using a perturbation technique and are compared with those by a numerical integration method. It is shown that the response amplitudes of parametric vibration are limited even in unstable conditions by hydrodynamic nonlinear damping force. The largest reponse amplitude of parametric vibration occurs in the first instability region of Mathieu stability chart. The parametric excitation induces the response of a dynamic system to be subharmonic, superharmonic or chaotic according to their dynamic conditions.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.479-490
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• 2020

The hydrodynamic characteristic of transonic motion projectiles with different head diameters are investigated by numerical simulation. Compressibility effect in liquid-phase water are modeled using the Tait state equation. The result shows that with increasing of velocity the compression waves transfer to shock waves, which cause the significant increasing of pressure and decreasing the dimensions of supercavities. While the increasing of head diameter, the thickness, the vapor volume fraction and the drag coefficient of supercavities are all enhanced, which is conducive to the stability of transonic-speed projectiles. The cavity dynamics of the different head projectiles are compared, and the results shows when Mach number is in high region, the truncated cone head projectile is enveloped by a cavity which results in less drag and better stability.

• 한국항해항만학회지
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• 제41권6호
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• pp.389-394
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• 2017

본 논문에서는 수중운동체 중 하나인 잠수함의 코닝타워(Conning tower) 위치 및 제어판 형태에 따라 4가지 타입별로 나누어 회전팔 시험(Rotating arm test)을 실시하였다. 또한 본 RA 시험을 통하여 유체력 미계수를 추정하였으며 수평면 운동에 대한 동적 안정성(Dynamic stability)을 평가하였다. 특히, 자유수면의 영향으로부터 자유로운 심도비(Depth ratio) 6.0에서 힘과 모멘트를 측정한 후, 다중회귀분석을 이용하여 유체력 미계수를 추정하였다. 최종적으로 선형유체력 미계수를 이용한 수평면 동적 안정성 지수를 산정함으로써 잠수함 타입별 특성이 동적 안정성에 미치는 영향을 분석하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.62-67
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• 2002

While upwelling regions account for only 0.1% of the ocean surface, they yield over 40% of world's fish catch. Thus it is vary important making upwelling region by various methods. This study was performed to find out basic hydrodynamic characteristics (function, stability..,) of artificial upwelling structures. The hydrodynamic characteristics of artificial upwelling structures can be summarized as follows: 1) The falling velocity of blocks was effected size($l_B$) of blocks than incident current velocity( $V_0$). 2) The falling horizontal distance was reduced as induce of stratification parameters and block' size. 3) Generation of artificial upwelling current was effected by size of structures and incident current. When stratification parameters was about 3.0 and relative height(hs/h) of structures was about $0.125{\sim}0.15$, stable artificial upwelling current was generated in the back-side of structures.

• 한국해양공학회지
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• 제30권1호
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• pp.25-31
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• 2016

In this study, hydrodynamic coefficients were obtained from a Rotating Arm (RA) test, which is one of the captive model tests used to provide accurate coefficients in the control motion equation of an underwater vehicle. The RA test was carried out at the RA facility of ADD (Agency for Defense Development), and the forces and moments acting on the underwater vehicle were measured using a six-axis waterproof gage. A multiple regression analysis was used in the analysis of the measured data. The experimental results were also verified by comparison with the theoretical values of the previous linear coefficients. In addition, the stability indices in the horizontal plane were calculated using the linear and nonlinear coefficients, and the dynamic stability of the underwater vehicle was estimated to have a good dynamic performance with a depth ratio of 6.0.

• 한국식품과학회지
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• 제25권3호
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• pp.277-281
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• 1993

콜로이드 식품에서의 단백질의 구조적 안정성을 연구하기 위하여 7개의 BSA structural intermediates, succinylated ${\beta}-lactoglobulin$을 만든 후 CD, 이황화물 결합함량, hydrodynamic radius 등을 측정하여 그 구조적 특성을 규명했다. Refolding time이 길수록 BSA intermediates들은 native BSA 구조에 근접하는 것을 나타냈고 succinylation은 ${\beta}-lactoglobulin$의 순 음전하를 변화시켜 보다 aperiodic structure를 갖게하였다. Perchlorate 존재하 ${\beta}-casein$의 구조는 소수성 상호작용에 크게 영향 받는 것으로 나타났다.

• 대한조선학회논문집
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• 제55권1호
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• pp.75-82
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• 2018

Wedge-shaped fins are generally used to provide sufficient forces and moments to control and maneuver a supercavitating vehicle. There are four fins placed along the girth of the vehicle, near he tail: two of the fins are horizontal and the other two fins are vertical. In a fully developed supercavitating flow condition, a part of the fin is in a cavity pocket and the other is exposed to water. In this paper, experimental investigations of hydrodynamic characteristics of the wedge-shaped fin models are presented. Experiments were conducted at a cavitation tunnel of the Chungnam National University. We first closely observed the typical formation of wake cavitation and measured lift and drag forces acting on two different test models. Next, using a special device for generating natural and artificial supercavities, we investigated hydrodynamic forces at different cavitation number conditions. This work provides a basis for interpreting the cavity stability and hydrodynamic characteristics of the wedge-shaped control fin for a supercavitating vehicle.

• 태양에너지
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• 제5권2호
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• pp.11-19
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• 1985

In this paper, the interface stability not to occur mixing and entrainment between the adjacent layers has been studied in the case of the selective withdrawal of a stratum and the injection in stratified fluid formed by the density difference in a small solar pond. There are stability parameter, Richardson number, Rayleigh number and Froude number as the parameters governing stability in order to measure the interface stability on the stratified fluid. The model which could measure the interface stability on the stratified fluid was the small solar pond composed by 1 meters wide, 2 meters high, and 5 meters long. In order to measure the interface stability on the stratified fluid at the inlet port, the middle section and the outlet port, Richardson number, Rayleigh number, and Froude number involved in the parameters governing the stability were calculated by means of the data resulted from the test of the study on hydrodynamic stability between the convective and nonconvective layers in that solar pond. Richardson number written by the ratio of inertia force to buoyancy force can be used in order to measure the stability on the stratified fluid related to the buoyancy force generated from the injection of fluid. Rayleigh number written by the product of Grashof number by Prandtl number can be used in order to measure the stability of the fluid related to the heat flux and diffusivity of viscosity. Froude number written by the ratio of gravity force to inertia force can be used in order to measure the stability of the nonhomogeneous fluid related to the density difference. As the result of calculating the parameters governing stability, the interface stability on the stratified fluid couldn't be identified below the 70cm height from the bottom of the solar pond, but it could be identified above the 70cm height from it at the inlet port, the middle section and the outlet port. When compared with such the three parameters as Richardson number, Rayleigh number, Froude number, the calculated result was in accord with them at inlet port, the middle section and the outlet port. Henceforth, it is learned that even though any of the three parameters is used for the purpose of measuring the interface stability on the stratified fluid, the result will be the same with them. It is concluded that all the use of Richardson number, Rayleigh number, and Froude number, is desirable and infallible to measure the interface stability on the stratified fluid in the case of considering the exist of the fluid flow and the heat flux like the model of the solar pond.

• 수산해양기술연구
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• 제52권2호
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• pp.79-87
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• 2016

Mobile fish-cage was developed assuming a cage net with an enclosed area, which and estimated the hydrodynamic characteristics of the cage through the model experiment. Flux-shielding plates, installed in the bow were compared with the resistance test carried out by making a hole, bilge keel and stud, and basic block flow rate consisting of the results to a flat surface plate. The experimental results confirmed the improved resistance performance effect of 3~6% in the bilge keel and the stud form. To assess the stability of the fish-cage, evaluation of the stability in accordance with the stability criteria for determining the floating docks had confirmed that it satisfied the static stability performance under operating conditions at sea.