• 한국항해항만학회지
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• 제37권3호
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• pp.257-262
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• 2013

거친 바다를 운항하는 선박의 경우 횡 동요로 인해 선박 내의 장비운영 문제 및 탑승객들에게 큰 불편함을 초래한다. 따라서 횡동요 감쇠를 위한 목적으로 빌지 킬, 핀 안정기, 자이로스코프, ART(Anti-Rolling Tank), 타, 플랩 등 다양한 횡 동요 감쇠장치들이 사용되고 있다. 콴다효과는 콴다제트가 곡면의 표면을 따라 흐르며 주위 유동의 순환을 증가시켜 양력을 효과적으로 발생시키는 방법으로 핀의 양력성능을 향상시킬 수 있다. 본 연구에서는 모형시험 및 수치계산을 통해 콴다효과를 적용한 고정식 핀 안정기의 사용가능성을 검토하였다. 그 결과 받음각이 $0^{\circ}$에서, 제트모멘텀을 $C_j$ = 0.25 만큼 공급할 때, 기준 핀의 최대 작동각($26^{\circ}$)에서 발생되는 양력과 동일하게 발생되는 것으로 나타났다. 즉 받음각을 변화시키는 기존의 핀 안정기와 달리 받음각을 고정하고, 콴다효과를 통한 제트유동제어만으로 선박의 횡 동요를 능동적으로 제어 할 수 있을 것으로 보인다.

• 대한조선학회논문집
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• 제40권5호
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• pp.10-16
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• 2003

To investigate the jet effect on circulation control, a segment of model was prepared and inserted horizontally across the test section of the cavitation tunnel. The hydrodynamic forces acting on the model were measured under the 2 dimensional flow behavior. Circulation flow control requires higher flow rate of water jet than boundary layer control does. Jet injection is effective in increasing lift coefficient and the increments reach to 160% in a certain combination of parameters such as an angle of attack, jet flow rate and flap angle. The blown water jet not only reduces form drag but also thrust effect, which is sometimes greater than the form drag in specific conditions.

• 대한조선학회논문집
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• 제50권1호
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• pp.25-32
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• 2013

The shape of a conventional full spade rudder has been modified to implement the Coanda effect and consequential changes in the flow characteristics are carefully examined to show the significant enhancement in the lift performance. A preliminary numerical study has been done to identify the optimum configuration of the modified rudder sections. For the purpose, chord wise locations of the jet slit and the radii of the trailing edge were varied in several ways and the changes in the lift characteristics have been observed at the various angles of attack, particularly focusing on the usefulness of the Coanda effect upon delaying the stall or increase in the circulation. Making the most use of the results so attained, full spade rudder of a VLCC has been reformed to realize the Coanda effect. A series of model experiments and numerical simulations are performed to confirm the effectiveness of the Coanda effect in improving the performance of the modified rudder. It is found that considerable enhancement in the lift performance of the rudder is plausible at any rudder angle if an optimum jet momentum is provided.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2006년도 추계학술발표회
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• pp.65-69
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• 2006

물제트분사장치가 부착된 NACA-0021 익 주변의 흐름을 업자영상유속계를 이용하여 고찰하였다. $R_e=6.0261\times10^4$에서 영각 (a) 을 $0^{\circ}\sim35^{\circ}$로 변화시켜가며, 물제트분사 속도를 0[m/s], 9.2[m/s] 의 2 가지로 조절한 결과 익 후류영역에서는 박리 후 비정상적인 (unsteady) 재순환 재부착 영역이 형성되었으며, 박리영역의 폭이 콴다 효과 (Coanda effect)를 갖는 물제트분사로 인하여 최대 1/3만큼 감소하는 경향을 확인하였다. 물분사가 없는 조건에서의 박리는 영각(a) $17^{\circ}\sim18^{\circ}$부근에서 시작되는 것이 관측되었으나, 물제트분사를 시켰을 경우 $20^{\circ}\sim21^{\circ}$에서 박리가 시작되는 것을 유통관측을 통해 알 수 있었다. 유통계측을 통해 익의 후연부 (trailing edge) 에서 생성되었던 와 (vortex, eddy) 가 물제트분사로 인해 소멸되는 것을 알 수 있었고, 영각이 작고 물분사 유속이 빠를 수록 박리영역의 감소가 더욱 가속화됨을 알 수 있었다.

• 대한조선학회논문집
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• 제47권4호
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• pp.543-552
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• 2010

The Coanda effect is noticeable when a jet stream is applied tangential to a curved surface since then the jet stream remains attached to the surface beyond the point where flow separates otherwise and results in augmentation of circulation and lift. Numerous experimental and numerical studies have been performed in various fields of aerodynamics to exploit the Coanda effect and many of them found to be useful. It can be speculated that the Coanda effect may have practical application to the field of marine hydrodynamics as well since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, the Coanda effect has been applied to a horn type rudder and a series of numerical computations and model experiments are performed to find the practical applicability. The results indicate that the Coanda jet increases the lift coefficient of the rudder as much as 52% at the momentum coefficient $C_j$ = 0.1 and the rudder angle ${\alpha}=10^{\circ}$.

• 대한조선학회논문집
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• 제48권2호
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• pp.113-120
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• 2011

Fins are widely used for roll stabilization of passenger ferries and high performance naval ships, among others. The Coanda effect is noticeable when a jet stream is applied tangentially to a curved wing surface since the jet can augment the lift by increasing the circulation. The Coanda effect has been found useful in various fields of aerodynamics and speculated to have practical applicability in marine hydrodynamics where various control surfaces are used to control motions of ships and the other offshore structures. In the present study, numerical computations have been performed to find proper jet momentum coefficients $C_j$ and trailing edge shapes suitable for the application of the Coanda effect to a stabilizer fin. The results show that the lift coefficient of the modified Coanda fin at the zero angle of attack ${\alpha}$ identically coincides with that of the original fin at ${\alpha}\;=\;25^{\circ}$ when Coanda jet is supplied at the rate of $C_j$ = 0.1. It is also shown that a fixed type fin stabilizer utilizing the Coanda effect can be implemented without changing the fin angle to actively control the motions of ships and the other offshore structures.

• 대한조선학회논문집
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• 제48권4호
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• pp.346-356
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• 2011

Rudder is to be located in extremely complicated flows generated and disturbed behind a hull and a propeller in operation. In order to estimate the rudder efficiency, it is quite important to investigate the disturbed flows due to the interaction under the hull-propeller and rudder condition. The purpose of the present research is to investigate the interaction between the hull-propeller and a high-lifting horn-type rudder through both numerical computations and experiments. A horn-type rudder implementing the Coanda effect of USB (Upper Surface Blowing) type is selected for its high efficiency of lifting force, and a 1/85 scaled model of 47K PC(Product Carrier) is manufactured for the purpose of the model test. The forces acting on the rudder during the experiment are measured using a three-component force gauge. Both cases are investigated in the hull-propeller-rudder condition and rudder open-water condition, which confirms that the flows generated under the former condition is considerably different from that of the latter condition.

• 대한조선학회논문집
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• 제45권6호
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• pp.569-578
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• 2008

The Coanda effects demonstrate that a jet stream applied tangential to a curved surface can generate lift force by increasing the circulation. Many experimental and numerical studies have been performed on the Coanda effect and it is found to be useful in various fields of aerodynamics. The Coanda effect may have practical application to marine hydrodynamics since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, numerical computations are performed to find the applicability of the Coanda effect to the marine control surfaces. For the purpose, changes in flow characteristics around a flapped foil due to the Coanda effect have been simulated by RANS equations discretized with a cell-centered finite volume method (FVM). In the process, special attention has been given to the influence of jet nozzle arrangement on the lift characteristics of the Coanda foil. It is found that the shape as well as the location of the jet intake and jet exit affects the lift performance of the foil significantly.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 추계학술대회 논문집(제1권)
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• pp.45-49
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• 2006

물분사장치가 부착된 NACA-0021 익 주변의 흐름을 입자영상유속계를 이용하여 고찰하였다. $R_w=6.0261{\times}10^4$에서 영각(a)을 $0^{\circ}{\sim}35^{\circ}$로 변화시켜가며, 물분사 속도를 0[m/s], 9.2[m/s]의 2가지로 조절한 결과 익 후류영역에서는 박리 후 비정상적인(unsteady) 재순환 ${\cdot}$ 재부착 영역이 형성되었으며, 박리영역의 폭이 콴다 효과(Coanda effect)를 갖는 물분사로 인하여 최대 1/3만큼 감소하는 경향을 확인하였다. ?Nㄴ사가 없는 조건에서의 박리는 영각(a) $17^{\circ}{\sim}18^{\circ}$ 부근에서 시작되는 것이 관측되었으나, 물분사를 시켰을 경우 $20^{\circ}{\sim}21^{\circ}$에서 박리가 시작되는 것을 유동관측을 통해 알 수 있었다. 유동계측을 통해 익의 후연부(trailing edge)에서 생성되었던 와(vortex, eddy)가 물제트분사로 인해 소멸되는 것을 알 수 있었고, 영각이 작고 물분사 유속이 빠를수록 박리영역의 감소가 더욱 가속화됨을 알 수 있었다.

• 해양환경안전학회지
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• 제18권6호
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• pp.591-596
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• 2012

안전하며 친환경적인 근해운송시스템을 확보하기 위해서는 운송 수단인 선박의 안전한 운항 확보가 필수적이다. 특히 좌초, 충돌 등의 해난사고를 방지하기 위해서는 선박이 우수한 조종성능을 갖는 것이 요구되며 특히 조종성능 중에서 선회성능은 충돌 회피 등에 필수적인 성능이다. 본 연구에서는 선박에 부착된 조타기의 타력 증가가 선박의 선회성능에 미치는 영향을 모형선 실험을 통하여 고찰하였다. 먼저 Coanda 효과를 이용한 고 양력 타 장치 모형과 47 K PC의 모형선을 제작하였다. 또한 모형선의 선회 성능 실험을 위한 자유항주시스템을 구축하고 사각 수조에서의 타력 증가 값을 변화시켜가면서 모형선의 선회 성능을 계측하여 타력 증가에 따른 선회 성능의 변화를 평가하였다. 모형선의 선회성능 실험결과를 통해 타력 증가가 근해운송 선박의 선회 성능 향상에 효과적인 것을 확인하였다.