• 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.

• 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 ${\alpha}=10^{\circ}$.

• 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.

• 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.

• 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.

• 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.

• 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

• 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.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.81.1-81.1
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• 2005