• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.399-406
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• 2014

Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a turbine blade equipped with both a pressure-side winglet and a suction-side squealer have been measured for the tip gap-to-span ratio of h/s = 1.36%. The suction-side squealer has a fixed height-to-span ratio of $h_s/s$ = 3.75% and the pressure-side winglet has width-to-pitch ratios of w/p = 2.64%, 5.28%, 7.92% and 10.55%. The results are compared with those for a plane tip and for a cavity squealer tip of $h_{ps}/s$ = 3.75%. The present tip delivers lower loss in the passage vortex region but higher loss in the tip-leakage vortex region, compared to the plane tip. With increasing w/p, its mass-averaged loss tends to be reduced. Regardless of w/p, the present tip provides lower loss than the plane tip but higher loss than the cavity squealer tip.

• Advances in aircraft and spacecraft science
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• v.8 no.4
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• pp.303-330
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• 2021

The paper discusses the effect of the winglets on the aerodynamic and aeroacoustic performance of Boeing 737-800 aircraft by numerical approach. For this purpose, computational fluid dynamics and fluent commercial software are used to solve the compressible flow governing equations. The RANS method and the K-ω SST turbulence model are selected to simulate the subsonic flow around the wing with acceptable accuracy and low computational cost. The main variables of steady flow around the simple and blended wing in constant atmospheric conditions are computed by numerical solution of governing equations. The solution of the acoustic field has also been accomplished by the broad-band acoustic source model. The results reveal that adding a blended winglet increases the pressure difference near the wingtip,which increases the lift force. Also, the blended winglet reduces the power and magnitude of vorticities around the wingtip, which reduces the wing's drag force. The effects of winglets on aerodynamic forces lead to a 3.8% increase in flight range and a 3.6% increase in the maximum payload of the aircraft. Also, the acoustic power level variables on the surfaces and fields around the wing have been investigated integrally and locally.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.103-111
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• 2024

Axial-flow fans are used to transport fluids in relatively low-pressure flow regimes, and a variety of design variables are employed. The tip geometry of an axial fan plays a dominant role in its flow and noise performance, and two of the most prominent flow phenomena are the tip vortex and the tip leakage vortex that occur at the tip of the blade. Various studies have been conducted to control these three-dimensional flow structures, and winglet geometries have been developed in the aircraft field to suppress wingtip vortices and increase efficiency. In this study, a numerical and experimental study was conducted to analyze the effect of winglet geometry applied to an axial fan blade for an air conditioner outdoor unit. The unsteady Reynolds-Averaged Navier-Stokes (RANS) equation and the FfocwsWilliams and Hawkings (FW-H) equation were numerically solved based on computational fluid dynamics techniques to analyze the three-dimensional flow structure and flow noise numerically, and the validity of the numerical method was verified by comparison with experimental results. The differences in the formation of tip vortex and tip leakage vortex depending on the winglet geometry were compared through a three-dimensional flow field, and the resulting aerodynamic performance was quantitatively compared. In addition, the effect of winglet geometry on flow noise was evaluated by numerically simulating noise based on the predicted flow field. A prototype of the target fan model was built, and flow and noise experiments were conducted to evaluate the actual performance quantitatively.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.55.3-55.3
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• 2008

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.637-644
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• 2005

This paper describes the numerical simulation of the interaction between longitudinal vortices ("common flow up") and a 3-D turbulent boundary layer over a flat plate To analyze the common flow up Produced from vortex generators. the flow field behind the vortex generators Is modeled by the information that is available from studies on a half-delta winglet. Also. the Reynolds-averaged Navier-Stokes equation for three-dimensional turbulent flows. together with a two-layer turbulence model to resolve the near-wall flow, is solved by the method of AF-ADI. The computational results predict that the boundary layer is thinned in the regions where the secondary flow is directed toward the wall and thickened where it is directed away from the wall Also. the numerical results. such as Reynolds stresses. turbulent kinetic energy and skin friction characteristics generated from the vortex generators . are reasonably close to the experimental data.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.149-156
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• 1999

In this study, aerodynmaic characteristics of the notch-back and fast-backpassenger vehicle models(1/10~1/12 acale) attached with winglets were experimentally investigated in a low speed wind tunnel. For various positions(X/L). tilted angles($\beta$) of a winglet, the aerodynamic forces on the vehicle model and rear-surface pressures were measured at various flow speeds. Also a flow of model surface was visualized by tuft method. The experimental results showed that winglets effect aerodynamic characteristics of vehicle models. A maximum of 3% reduction in lift coefficient was achieved with winglets at $\alpha$=-30$^{\circ}$. A maximum of 10% reduction in drag coefficient was achieved for a model with winglets and a rear-spoiler.

• Journal of the Semiconductor & Display Technology
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• v.17 no.1
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• pp.84-87
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• 2018

As the propeller end speed increases, the propeller surface is damaged in the process of bubble formation and dropout. It is intended to prevent the corrosion of the propeller by modifying the shape of the end through the winglet structure to mitigate the cavitation phenomenon. In the case of conventional SUS materials, the cost of production is so high that plastic materials are used to prevent corrosion. This paper aims to mitigate the cavitation by deforming the shape of the end through the winglet structure by using the SMC composite material of the propeller using the existing SUS.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.24-29
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• 2008

Aircraft fuel efficiency is one of main concerns to aircraft manufacturers and to aviation companies because jet fuel price has tripled in last ten years. One of simple and effective methods to increase fuel efficiency is to reduce aircraft induced drag by using of wingtip devices. Induced drag is closely related to the circulation distribution, which produces strong wingtip vortex behind the tip of a finite wing. Wingtip devices including winglets can be successfully applied to reduce induced drag by wingtip vortex mitigation. Winglet design, however, is very complicated process and has to consider many parameters including installation position, height, taper ratio, sweepback, airfoil, toe-out angle and cant angle of winglets. In current research, different shapes of winglets are compared in the view of vortex mitigation. Appropriately designed winglets are proved to mitigate wingtip vortex and to increase lift to drag ratio. Also, the results show that winglets are more efficient than wingtip extension. That is the reason B-747-400 and B-737-800 chose winglets instead of a span increase to increase payload and range. Drag polar comparison chart is presented to show that minimum drag is increased by viscous drag of winglet, but at high lift, total drag is reduced by induced drag decrease. So, winglets are more efficient for aircraft that cruises at a high lift condition, which generates very strong wingtip vortex.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.447-447
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• 2021

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.9
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• pp.843-852
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• 2000

The flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices were studied experimentally. The test facility consisted of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta winglet protruding from the surface. In order to control the strength of the longitudinal vortices, the angles of attack of the vortex generators were varied from $\pm20\;degree\;to\;\pm45$ degree, but spacings between the vortex generators were fixed to 4 cm. The 3-dimensional mean velocity measurements were made using a five-hole pressure probe. Heat transfer measurements were made using the thermochromatic liquid to provide the local distribution of the heat transfer coefficient. By using the method mentioned above, the following conclusions were obtained from the present experiment. The boundary layer was thinned in the regions where the secondary flow was directed toward the wall and thickened where it was directed away from the wall. The peak augmentation of the local heat transfer coefficient occurred in the downwash region near the point of minimum boundary-layer thickness.