• Journal of Ship and Ocean Technology
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• v.8 no.2
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• pp.1-12
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• 2004

To keep the ocean environment from pollutions, strict international requirements on the controllability are arisen to the VLCC. Especially in low speed operations near the harbor, the VLCC is often supported by tug to replenish the insufficient rudder force. When water jet is blown to the flapped rudder, the Coanda effect induces a high-lift force by delaying stall and re-enforcing circulation in a large angle of attack (Lachmann 1961, Ahn 2003). Based on numerous research efforts, the rudder system supported by the Coanda effect was devised and its performances were evaluated in the towing tank for a large VLCC model. Hydrodynamic forces acting on the rudder system were measured with a water jet blowing on the rudder surface and compared with those acting on a conventional rudder. The effectiveness of the new rudder system was proven through an experimental evaluation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.33-33
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• 1999

The Coanda effect is the tendency for a fluid jet to atach itself to an adjacent surface and follow its contour without causing an appreciable flow separation. The jet is pulled onto the surface by the low pressure region which develops as entrainment pumps fluid from the region between the jet and the surface. Then the jet is held to the wall surface by the resulting radial pressure gradient which balance the inertial resistance of the jet to turning. The jet may attach to the surface and may be deflected through more than 180 dog, when the radius of the Coanda surface is sufficiently large compared to the height of the exhaust nozzle. However, if the radius of curvature is small, the jet turns through a smaller angle, or may not attach to the surface at all. In general, the limitations in size and weight of a device will limit the radius of the deflection surface. Thus much effort has been paid to improve the jet deflection in a variety of engineering fields. The Coanda effect has long been applied to improve aerodynamic characteristics, such as the drag/lift ratio of flight body, the engine exhaust plume thrust vectoring, and the aerofoil/wing circulation control. During the energy crisis of the seventies, the Coanda jet was applied to reduce vehicle drag and led to drag reductions of as much as about 30% for a trailer configuration. Recently a variety of industrial applications are exploiting another characteristics of the Coanda jets, mainly the enhanced turbulence levels and entrainment compared with conventional jet flows. Various industrial burners and combustors are based upon this principle. If the curvature of the Coanda surface is too great or the operating pressure too high, the jet flow will break away completely from the surface. This could have catastrophic consequences for a burner or combustor. Detailed understanding of the Coanda jet flow is essential to refine the design to maximize the enhanced entrainment in these applications.

• Journal of Ship and Ocean Technology
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• v.8 no.2
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• pp.13-19
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• 2004

Jet flows applied tangential to a foil surface near the leading and/or trailing edges increase the lift of the foil by delaying the separation also known as the Coanda effects. Many experimental and numerical studies have proven the effectiveness of Coanda effects on circulation control and the effects have been found to be useful in practical application in many aerodynamics fields. Most of the previous works have studied the effects of the jet blowing near the trailing edges and investigated the influence of jet momentum on lift. A few experimental studies, however, focused on the separation bubble that develops near the leading edge and applied jet flow the edge to remove the bubble but only to find decrease in lift. In the present paper, a Coanda foil of 20% thickness ellipse with modified rounded leading and trailing edges was investigated, and the flow around the foil was numerically studied. The blowing around the leading edge only decreased the lift, as the experiments showed, but the suction considerably increased the lift.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.927-933
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• 2012

The characteristics of two-dimensional supersonic coanda flow was experimentally investigated. For various ratios of slot height to coanda wall's radius of curvature, surface roughnesses, and jet stagnation pressures, the characteristics of the supersonic coanda flow such as shock structures and hysteresis were observed by flow visualization. It was found that the characteristics of hysteresis of the coanda jet was related to the surface roughness of the coanda wall. The study was further extended for application of the tangentially injected coanda jet to control co-flowing highly compressible main jet direction. It was noticed that the stagnation pressure of the main jet as well as the ratio of the slot height to coanda wall's radius of curvature wall was an influencing factor in the performance of the fluidic thrust vectoring method.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.967-972
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• 2013

A MILD (Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used the MILD combustor, which has coaxial cylindrical tube. The outside tube of the MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. A numerical analysis was accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of coanda nozzle geometrical parameters, nozzle passage gap length, nozzle passage length, nozzle angle and expansion length. The optimal configuration of coanda nozzle for the best entrainment flow rate was gap length, 0.5 mm, expansion angle, 4o and expansion length, 146 mm. The nozzle passage length was irrelevant to the exhaust gas entrainement.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.65.2-65.2
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• 2005

• 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.

• Advances in aircraft and spacecraft science
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• v.4 no.4
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• pp.401-419
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• 2017

This paper presents the main outcomes of the preliminary development of the Anuloid, an innovative disk-shaped VTOL aircraft. The Anuloid has three main features: lift is provided by a ducted fan powered by a turboshaft; control capabilities and anti-torque are due to a system of fixed and movable surfaces that are placed in the circular internal duct and the bottom portion of the aircraft; the Coanda effect is exploited to enable the control capabilities of such surfaces. In this paper, results from CFD analyses and wind tunnel tests are presented. Horizontal and vertical flights were considered, including accelerated flight. Particular attention was paid to the experimental analysis of the Coanda effect via a reduced scale 3D printed model. The results suggest that the Coanda effect is continuously present at the lower surface of the Anuloid and may be exploited for the control of the aircraft. Also, very complex 3D flows may develop around the aircraft.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.610-613
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• 2014

본 연구에서는 Dyson사의 Air multiplier의 Coanda surface각도에 따른 Air foil 주변의 2차원 유동을 분석하고 Surface각도가 유동에 미치는 영향에 대해 해석하였다. Air multiplier 단면의 작은 Slit을 통해 분류된 공기는 Venturi effect에 의해 가속되며 Coanda effect에 의해 단면을 따라 흐르며 압력차를 발생시켜 주변의 공기를 추가적으로 유입시킨다. EDISON CFD를 이용하여 Surface 각도에 따른 Air foil 주변의 유동을 구현하고 각도가 유동에 미치는 영향을 해석하였다. 또한 다른 논문에서 발췌한 실험값과 CFD 분석을 통해 얻은 값을 비교하여 CFD분석이 유효한지 확인하였다.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.257-262
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• 2013

A ship operating in rough sea may suffer from an undesirable motion which may severely degrade the performance of equipment onboard and give a person an uncomfortable feeling. Hence, roll stabilization received a considerable attention and various devices including bilge keels, stabilizing fins, gyroscopic, anti-rolling tanks, rudders and flaps have been conceived and utilized for the purpose. The Coanda effect is evident when a jet stream is applied tangential to a curved surface of a hydrofoil since then the jet increases the circulation around the foil and consequently the lift. Model tests and numerical simulation have been conducted to examine the practicality of a fixed type fin stabilizer augmented by the Coanda jet. The results show that the lift coefficient of the modified Coanda fin at the zero angle of attack identically coincides with that of the original fin at ${\alpha}=\26^{\circ}$ when Coanda jet is supplied at the rate of $C_j$ = 0.25. It is also shown that fixed type fin stabilizers for active control of the motions of ships and the other mobile units without rotation can be put to practical use if the Coanda effect is applied.