• Title/Summary/Keyword: Coanda jet

Search Result 48, Processing Time 0.023 seconds

EXPERIMENTAL AND COMPUTATIONAL STUDIES ON HYSTERISYS PHENOMENON OF SUPERSONIC COANDA WALL JETS

  • Kim, Heuy-Dong;Kweon, Oh-Sik;Setoguchi, Toshiaki
    • Proceedings of the KSME Conference
    • /
    • 2000.04b
    • /
    • pp.514-519
    • /
    • 2000
  • Recently a considerable interest is being concentrated on industrial applications of supersonic Coanda wall jets, but the flow physics are not still understood well. It is of practical importance to evaluate the effectiveness of supersonic Coanda wall jet devices fer such industrial purposes. In the present work, experiments and computations were performed to Set a better understanding of the supersonic Coanda jet physics. The experiments were made using a small blow-down wind tunnel. The operating pressure ratio and the Coanda surface configuration were changed to investigate their influences on the wall jet flows. Two-dimensional Navier-Stokes computations were performed using a TVD finite volume scheme to effectively capture the important wave structures of supersonic Coanda jet flows. Both experimental and computational results showed several important hysterical features of the supersonic Coanda wall jets; the attachment and detachment of supersonic Coanda jet were strongly dependent on the change processes of the operating pressure ratio and the detailed flow configuration.

  • PDF

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
    • /
    • v.9 no.2
    • /
    • pp.177-184
    • /
    • 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 $10^{\circ}$.

Experimental Study Of Supersonic Coanda Jet

  • Kim, Heuydong;Chaemin Im;Sunhoon, Woo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 1999.10a
    • /
    • pp.33-33
    • /
    • 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.

  • PDF

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
    • /
    • v.45 no.6
    • /
    • pp.569-578
    • /
    • 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.

Experimental Study of the Characteristics of 2-Dimensional Coanda Nozzle Jet (2차원 Coanda 노즐 제트 의 특성 에 관한 실험적 연구)

  • 이동호;정명균;김응태
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.6 no.3
    • /
    • pp.222-231
    • /
    • 1982
  • A single free jet formed by the interaction of two curved wall jets on a Cylinder surface is defined as "the Coanda nozzle jet" in this study. In order to investigate the characteristics of Coanda nozzle jet, an experimental analysis was carried out; measurements of the static pressure distribution on the cylinder surface, the mean velocity profile, the turbulence intensity, and the Reynolds shear stress by using x-type hot-wire probe.ire probe.

Experimental Study of Thrust Vectoring of Supersonic Jet Utilizing Co-flowing Coanda Effects (동축류의 코안다 효과를 이용한 초음속 제트의 추력편향제어에 관한 실험적 연구)

  • Yoon, Sang-Hun;Jun, Dong-Hyun;Heo, Jun-Young;Sung, Hong-Gye;Lee, Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.40 no.11
    • /
    • pp.927-933
    • /
    • 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.

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
    • /
    • v.48 no.2
    • /
    • pp.113-120
    • /
    • 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 Numerical Study on the Geometry of Jet Injection Nozzle of a Coanda Control Surface

  • Seo, Dae-Won;Kim, Jong-Hyun;Kim, Hyo-Chul;Lee, Seung-Hee
    • Journal of Ship and Ocean Technology
    • /
    • v.12 no.3
    • /
    • pp.36-54
    • /
    • 2008
  • A jet stream applied tangential to a curved surface in fluid increases lift force by strengthening circulation around the surface and this phenomenon is known as the Coanda effect. Many experimental and numerical studies have been performed on the Coanda effect and the results found to be useful in various fields of aerodynamics. Recently, preliminary studies on Coanda control surface are in progress to look for practical application in marine hydrodynamics since various control surfaces are used to control behaviors of ships and offshore structures. In the present study, the performance of a Coanda control surface with different geometries of the jet injection nozzle was surveyed to assess applicability to ship rudders. A numerical simulation was carried out to study flow characteristics around a section of a horn type rudder subjected to a tangential jet stream. The RANS equations, discretized by a cell-centered finite volume method were used for this computation after verification by comparing to the experimental data available. Special attentions have been given to the sensitivity of the lift performance of a Coanda rudder to the location of the slit (outlet) and intake of the gap between the horn and rudder surface at the various angles of attack. It is found that the location of the water intake is important in enhancing the lift because the gap functions as a conduit of nozzle generating a jet sheet on the rudder surface.

A Study on the Flow Characteristics around a Coanda Control Surface

  • Hong, Seok-Jin;Lee, Seung-Hee
    • Journal of Ship and Ocean Technology
    • /
    • v.8 no.2
    • /
    • pp.13-19
    • /
    • 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.

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
    • /
    • v.47 no.4
    • /
    • pp.543-552
    • /
    • 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 ${\alpha}=10^{\circ}$.