Flow Analysis of Naca0018 Airfoil with Blended Winglet for Low Speed Aircraft

Flow Analysis of Naca0018 Airfoil with Blended Winglet for Low Speed Aircraft

T. N. R. Venkat Ramanan

Dept of AERO- PITS

N. Nagarajan Assistant Professor Dept of AERO- PITS

S. Naveen

Dept of AERO- PITS

Abstract :- Design a new concept of induced drag reduction of blended winglet.The optimum reduction of the drag created by the trailing vortices at the tip of aircraft wing. The dimension of winglet yield huge amount of reduction in fuel consumption. The aim of the analysis was to compare the aerodynamic characteristics of single, two and three winglet configuration and to find the performance of the winglets.

Index Terms-Blended winglet, Induced drag reduction, outboard wing, staggered winglet.

INTRODUCTION

DRAG is generated by the interaction and contact of a solid body with a fluid [1]. The aim of the project is primarily to reduce drag in an airplane or a car that will lead to more velocity and fuel efficiency. This is done primarily to reduce the Induced drag created due to high pressure underneath the wing that causes the airflow at the tips of the wings to curl around from bottom to top in a circular motion, resulting in a trailing vortex which in turn increases the angle of attack that results in an increase in induced drag [2]. An Ideal way to decrease the lift-induced drag is to increase the aspect ratio of the wing, but it is not a great possibility to do the same [3]. An alternative being to develop wing tip devices acting on the vortex, which is the origin of the lift, induced drag. An effective Drag reduction technique involves modification of the wing structure and the angle of attack[4]. Passive techniques include wingtip turbine, wing tip sails, wing grid, winglets etc. Analysis has shown that the passive control technique reduces the viscous flow. Research has indicated that winglets could reduce induced drag [5]. The airfoil was placed in a subsonic wind tunnel with pressure taps along its surface and a pitot probe downstream to measure the flow characteristics. The wind tunnel was operated at a nominal 17 m/s during the coefficient measurements, a Reynold's number of about232,940 and was analyzed at 0, 5, 10 and 15 degree angles of attack and drag was reduced by twenty percent .In short increasing the span is achievable using the technique of blended winglet at low.

METHODOLOGY

In an existing model for the reduction of induced drag with single winglet results in minimal drag to lift ratio. The blended winglet reduces the induced drag without

increasing the span of aircraft [6]. The blended winglet is expected to be more efficient than the conventional one to reduce the flow acceleration that occurs in the cross-flow curvature and to decrease the vortex intensity as important chord variation is avoided. The usage of blended winglet for the reduction of induced drag without increasing the span of aircraft wings was tested in a subsonic wind tunnel using a rectangular, untwisted wing built from NACA 0018 airfoil with a 15% thickness to chord ratio constituted of three winglets, at flow speed 20m/s and placing the wing at angle of attack ranging from -5 to +15 deg. Reynolds numbers from 161,000 to 300,000 range were tested. Wind tunnel balances provided lift and drag measurements, and laser flow visualization obtained wingtip vortex information. And also the wing with no winglet (bare wing) and with single winglet was also tested in the same condition as in the case of blended winglets. The results show that blended winglet system reduced induced drag by 27.9% and improved CL by 26.5% compared to bare wing. Dihedral spread of the winglets improves lift by taking some of the winglets away from the wing plane, and redistributing the tip vortex into multiple vortices that do not merge in the near wake, thereby reducing the effective downwash at the wing plane. Combining the force measurement results with the flow visualization we observe that negative incidence and geometrically twisted winglets improves L/D by reorienting the winglet lift vector forward and thus canceling part of the drag.

LIFT, DRAG AND MOMENT OF NACA0018 AIRFOIL

To measure the flow characteristics the wind tunnel was operated at a nominal 17 m/s during the coefficient measurements, a reynold number of about 232,940 and was analysed at 0,5,10and 15-degree angles of attack. and the phenomenon known as hysteresis with regards to stall conditions was also observed by varying the angle of attack and wind tunnel velocity. The observation indicates that that as a result of the control, higher moment was drawn towards the wall, which was responsible for delaying separation.

INDUCED DRAG REDUCTION USING BLENDED WINGLET

The drag reduction provided by blended winglets improves fuel efficiency and thereby reduces emissions. The paper

shows, how taking into account grid effect of blended winglets on the deflected mass flow of a wing system within linear models exhibit much smaller induced drag. The blended winglet is expected to be more efficient than a narrow one to reduce the flow acceleration that occurs in the cross-flow curvature and to decrease the vortex intensity as important chord variation is avoided [7]. The results for the Split-Wing configuration tested in parallel experimentally were obtained by calculating the true force free vortex sheets leaving the wing, including partial rollup, in the near field a few chord lengths downstream using iterative wake relaxation. Induced drag was obtained using the classic Trefftz plane. Interpreting the fanned winglets as a true grid, the additional deflected mass flow delta using the Betz grid deflection coefficient with the grids t/c is calculated. The blended winglet provides a transition region between the outboard wing, which is typically designed for a plain tip, and the winglet. Without this transition region, the outer wing would require aerodynamic redesign to allow for the interference between the wing and winglet surfaces [8].

AERODYNAMIC ANALYSIS

A CFD 3-dimensional winglet analysis that was performed on a rectangular wing of NACA653218 cross sectional airfoil is shown. The wing is of 660 mm span and 121 mm chord and was analyzed for two shape configurations, semicircle and elliptical. The objectives were to compare the aerodynamic characteristics of the two winglet configurations and to investigate the performance of the two winglets shape simulated at selected angles of 0, 45 and 60 degrees. The computational simulation was carried out by FLUENT solver using finite volume approach. The simulation was done at low subsonic flow and at various angles of attack using Spalart- Allmaras couple implicit solver. A comparison of aerodynamics characteristics of lift coefficient CL, drag coefficient CD and lift to drag ratio L/D was made and it was found that the addition of the elliptical and semi circular winglet gave a larger lift curve slope and higher lift-to-drag ratio in comparison to the baseline wing alone. Elliptical winglet with an angle of

45 degree was the best overall design giving about 8 percent increase in lift curve slope and the best lift-to-drag ratio.

DESIGN

Research based on the materials of winglet manufacturing led us to the use of Medium density fiber board (MDF) for its cost efficiency on comparison with other materials and the ease of fabrication.

FIG1: NACA0018 WING TABLE I: PARAMETERS OF BARE WING

FIG 2: NACA0018 WING WITH BLENDED WINGLET

TABLE III: PARAMETERS OF MULTI WINGLET

FIG 5: CONTOURS OF WING WITH BLENDED WINGLET

V. RESULTS AND DISCUSSION

1. XPERIMENTAL AND THEORETICAL VALUE OF WNG WITHWINGLET

   5

   5

   TABLE V: COMPARISON OF EXPERIMENTAL AND THEORETICAL VALUE AT °

   TABLE VI: COMPARISON OF EXPERIMENTAL

   TABLE IV: COMPARISON OF EXPERIMENTAL AND THEORETICAL

   TABLE VIII: COMPARISON OF EXPERIMENTAL AND THEORETICAL

   1 0

   1 0

   AND THEORETICAL VALUE AT °

   EXPERIMENTAL AND THEORETICAL VALUE OF WING WITH BLENDED WINGLET

   TABLE VII: COMPARISON OF EXPERIMENTAL AND THEORETICAL VALUE AT °0

   TABLE IX : COMPARISON OF EXPERIMENTAL AND THEORETICAL VALUE AT 5

   TABLE XII: COMPARISON OF THEORETICAL AND EXPERIMENTAL VALUES

   CONCLUSION

   In this work, theoretical and experimental calculations were done and t°he performance parameters were investigated to obtain the following results. Blended winglet configuration reduced the wing-induced drag and improved L/D by 15-30% compared with the baseline 0012 wing. Stall angle for blended winglet system is much higher than conventional system. At high angles of attack blended winglet system produces better CL. Blended winglet can reduce the induced drag in more percentage compared to conventional winglet system at low angles of attack.

   REFERENCES

   1. J.Johansen and N.N.Sorensen. Aerodynamic investigation of winglets on wind turbine blades

   2. Viswanath, P. (2002). Aircraft Viscous Drag Reduction Using Winglets. Progress In Aerospace Sciences 38

   3. U. La Roche And H.L. La Rocheü La Roche Consulting,

   4. . (n.d.). Induced Drag Reduction Using Multiple Winglets.

   5. Srikanth G, S. B. (n.d.). Experimental Analysis Of Multi- Winglets

   6. Miller, S. D. (28 May 2008). Lift, Drag And Moment Of A Naca 0018 Airfoil.

   7. M. J. Smith, N. K. (n.d.). Performance Analysis Of A Wing With Multiple Winglets. Aiaa-2001- 2407