• Title/Summary/Keyword: Coanda effect

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An Application of Coanda Effect to a Flapped Rudder

  • Ahn, Hae-Seong;Kim, Hyo-Chul;Park, Je-Jun;Lee, Seung-Hee
    • Journal of Ship and Ocean Technology
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    • v.3 no.4
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    • pp.23-34
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    • 1999
  • A Coanda effect which is known to provide a high lift in a high drag condition has been applied to a flapped rudder of a ship. Model experiments and numerical simulations on the Coanda effect of the flapped rudder have been carried out at various situations and the results are compared to each other. It I found that a remarkable increase in the rudder force occur due to the Coanda effect and that the results ould be utilized for the design of a high-lift rudder system.

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Performance analysis of a horn-type rudder implementing the Coanda effect

  • Seo, Dae-Won;Oh, Jungkeun;Jang, Jinho
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.9 no.2
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    • pp.177-184
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    • 2017
  • The Coanda effect is the phenomenon of a fluid jet to stay attached to a curved surface; when a jet stream is applied tangentially to a convex surface, lift force is generated by increase in the circulation. The Coanda effect has great potential to be applied practically applied to marine hydrodynamics where various lifting surfaces are being widely used to control the behavior of ships and offshore structures. In the present study, Numerical simulations and corresponding experiments were performed to ascertain the applicability of the Coanda effect to a horn-type rudder. It was found that the Coanda jet increases the lift coefficient of the rudder by as much as 52% at a jet momentum coefficient of 0.1 and rudder angle of $10^{\circ}$.

A Numerical Study for Design of a Fixed Type Fin Stabilizer Utilizing the Coanda Effect (콴다 효과를 적용한 고정식 핀 안정기 설계를 위한 수치적 연구)

  • Seo, Dae-Won;Lee, Seung-Hee
    • Journal of the Society of Naval Architects of Korea
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    • v.48 no.2
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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.

A Study to Improve the Lift Performance of a Full Spade Rudder with the Coanda Effect (콴다효과를 이용한 전 가동 타의 양력성능 개선에 관한 연구)

  • Seo, Dae-Won;Lee, Seung-Hee
    • Journal of the Society of Naval Architects of Korea
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    • v.50 no.1
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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.

A Study for Improvement of Lift Performance of a Horn-type Rudder with the Coanda Effect (콴다 효과를 이용한 혼-타의 양력성능 개선에 관한 연구)

  • Seo, Dae-Won;Oh, Jung-Keun;Lee, Seung-Hee
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.4
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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 ${\alpha}=10^{\circ}$.

Improvement of Film Cooling Performance of a Slot on a Flat Plate Using Coanda Effect (코안다 효과를 이용한 평판 슬롯의 막냉각 성능 향상)

  • Kim, Gi Mun;Kim, Ye Jee;Kwak, Jae Su
    • The KSFM Journal of Fluid Machinery
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    • v.20 no.2
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    • pp.5-10
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    • 2017
  • In this study, the Coanda effect inducing bump was applied to improve the film cooling effectiveness on the flat plate with $30^{\circ}$ and $45^{\circ}$ angled rectangular slots. The slot length to width ratio was 6. A cylindrical cap shaped structure, called Coanda bump, was installed at the exit of the slot to generate Coanda effect. The width and height of the bump was 10.5 mm and 1 mm, respectively. The film cooling effectiveness was measured at the fixed blowing ratio, M=2.0, using pressure sensitive paint (PSP) technique. The mainstream velocity was 10 m/s and the turbulence intensity was about 0.5%. Results showed that the film cooling effectiveness for case of $30^{\circ}$ angled slot was higher than that of $45^{\circ}$ angled slot. It was found that there was no positive effect of Coanda effect on the overall averaged film cooling effectiveness for the $30^{\circ}$ angled slot. On the other hand, for the $45^{\circ}$ angled slot, the film cooling effectiveness was improved with the installation of the Coanda bump.

Influence of Jet Nozzle Arrangement on the Performance of a Coanda Foil (제트 노즐의 배치가 콴다 날개의 성능에 미치는 영향)

  • Seo, Dae-Won;Kim, Joung-Hyun;Kim, Hyo-Chul;Lee, Seung-Hee
    • Journal of the Society of Naval Architects of Korea
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    • v.45 no.6
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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.

Performance Analysis of Stabilizer Fin Applied Coanda System (코안다 시스템이 장착된 안정기용 핀의 성능해석)

  • Seo, Dae-Won;Lee, Se-Jin;Oh, Jungkeun
    • Journal of Ocean Engineering and Technology
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    • v.30 no.1
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    • pp.18-24
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    • 2016
  • Stabilizer fins are installed on each side of a ship to control its roll motion. The most common stabilizer fin is a rolling control system that uses the lift force on the fin surface. If the angle of attack of a stabilizer fin is zero or the speed is zero, it cannot control the roll motion. The Coanda effect is well known to generate lift force in marine field. The performance of stabilizer fin that applies the Coanda effect has been verified by model tests and numerical simulations. It was found that a stabilizer fin that applied the Coanda effect at Cj = 0.085 and a zero angle of attack exactly coincided with that of the original fin at α = 26°. In addition, the power needed to generate the Coanda effect was not high compared to the motor power of the original stabilizer fin.

On the development of the Anuloid, a disk-shaped VTOL aircraft for urban areas

  • Petrolo, Marco;Carrera, Erasmo;D'Ottavio, Michele;de Visser, Coen;Patek, Zdenek;Janda, Zdenek
    • Advances in aircraft and spacecraft science
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    • v.1 no.3
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    • pp.353-378
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    • 2014
  • This paper deals with the early development of the Anuloid, an innovative disk-shaped VTOL aircraft. The Anuloid concept is based on the following three main features: the use of a ducted fan powered by a turboshaft for the lift production to take-off and fly; the Coanda effect that is developed through the circular internal duct and the bottom portion of the aircraft to provide further lift and control capabilities; the adoption of a system of ducted fixed and swiveling radial and circumferential vanes for the anti-torque mechanism and the flight control. The early studies have been focused on the CFD analysis of the Coanda effect and of the control vanes; the flyability analysis of the aircraft in terms of static performances and static and dynamic stability; the preliminary structural design of the aircraft. The results show that the Coanda effect is stable in most of the flight phases, vertical flight has satisfactory flyability qualities, whereas horizontal flight shows dynamic instability, requiring the development of an automatic control system.