RANS Investigation of the Transitional Flow Over Stepped NLF(1)-0416

2012 ◽  
Author(s):  
Shervin Sammak ◽  
Rambod Mojgani ◽  
Masoud Boroomand
Keyword(s):  
Skin Friction ◽  
Fluid Dynamic ◽  
Leading Edge ◽  
Transitional Flow ◽  
Stream Velocity ◽  
Backward Facing Step ◽  
Suction Surface ◽  
Rans Equations ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The Computational Fluid Dynamic simulation of RANS equations over NLF(1)-0416, utilized by backward facing step, is investigated for enhancement of aerodynamic characteristics. This article concentrates on the effects of step location transition point and reattachment of separated flow by backward facing step on pressure distribution and skin friction coefficient and subsequently on lift and drag. Reynolds number (based on the free stream velocity and airfoil chord) is 2.0 million. The finite volume method has been employed to numerically solve the steady state compressible Reynolds Averaged Navier-Stokes (RANS) equations with second order Roe’s scheme. Steps at different chordwise locations are chosen on both suction and pressure sides of the airfoil in order to determine their effects on skin friction, lift, lift to drag ratio and near stall behavior. In specific cases decreasing in drag is achieved due to step point on the chord followed by transition inception. The results show that all stepped studied airfoil cases experienced higher drag in comparison with base airfoil. Lift to drag ratio enhancement is seen in step on pressure side while the step extended to leading edge, this effect increases. Based on the results, delaying stall in some cases with step on suction surface is concluded.

Numerical Investigation of Turbulent Flow Around a Stepped Airfoil at High Reynolds Number

2009 ◽  
Author(s):  
Masoud Boroomand ◽  
Shirzad Hosseinverdi
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Vortex Formation ◽  
Stream Velocity ◽  
Pressure Side ◽  
Backward Facing Step ◽  
Suction Surface ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Trapped Vortex

This study presents the numerical simulation of flow development around NACA-2412 airfoil which utilized the backward facing step to explore the possibility of enhancing airfoil aerodynamic performance by trapped vortex lift augmentation. This article concentrate on the effect of separated flow and following vortex formation which is created by backward facing step on pressure distribution and subsequently on lift and drag coefficient. Reynolds number that based on the free stream velocity and airfoil chord is 5.7×106. The two-equation shear stress transport (SST) k-ω turbulence model of Menter is employed to determine accurately turbulent flow, as well as the recirculation pattern along the airfoil. The Reynolds-averaged Navier Stokes (RANS) equations are solved numerically using finite volume based solution with second-order upwind Roe’s scheme. Steps are located on both suction side and pressure side of the airfoil, at different locations, different lengths and various depths in order to determine their effects on lift, lift to drag ratio and near stall behavior. The modeling results showed that all stepped airfoil cases studied experienced higher drag compared to the base airfoil. Considerable lift enhancement was found for airfoil with backward facing step on pressure side at all values of angle of attack because of trapped vortex. The results suggest that the steps on the lower surface that extended back to trailing edge can lead to more enhancement of lift to drag ratio for some angles of attack; while the rear locations for the step on upper surface was found to have negative effect on lift to drag ratio. Based on this study, the backward facing step on suction surface offers no discernable advantages over the conventional airfoil but showed some positive effect on delaying stall.

Numerical Investigation of Bionic Rudder With Leading-Edge Protuberances

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Hongtao Gao ◽  
Wencai Zhu
Keyword(s):  
Electron Microscopy ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Hydrodynamic Performance ◽  
Spanwise Direction ◽  
Flow Mechanism ◽  
Suction Surface ◽  
Edge Profile ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The duck's webbed feet are observed by using electron microscopy, and observations indicate that the edges of the webbed feet are the shape of protuberances. Therefore, the rudder with leading-edge protuberances is numerically studied in the present investigation. The rudder has a sinusoidal leading-edge profile along the spanwise direction. The hydrodynamic performance of rudder is analyzed under the influence of leading-edge protuberances. The present investigations are carried out at Re = 3.2 × 105 and 8 × 105. In the case of Re = 3.2 × 105, the curves of lift coefficient illustrate that the protuberant leading-edge scarcely affects the lift coefficient of bionic rudder. However, the drag coefficient of the bionic rudder is markedly lower than that of the unmodified rudder. Therefore, the lift-to-drag ratio of the bionic rudder is obviously higher than the unmodified rudder. In another case of Re = 8 × 105, the advantageous behavior of the bionic rudder with leading-edge protuberances is mainly performed in the post-stall regime. The flow mechanism of the significantly increased efficiency by the protuberant leading-edge is explored. It is obvious that the pairs of counter-rotating vortices are presented over the suction surface of bionic rudder, and therefore, the flow is more likely to adhere to the suction surface of bionic rudder.

Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils

2003 ◽  
Vol 125 (4) ◽  
pp. 468-478 ◽  
Author(s):  
R. P. J. O. M. van Rooij ◽  
W. A. Timmer
Keyword(s):  
Turbine Blades ◽  
Leading Edge ◽  
Lower Surface ◽  
Vortex Generators ◽  
Wind Turbine Blades ◽  
High Lift ◽  
Edge Roughness ◽  
Proper Design ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In modern wind turbine blades, airfoils of more than 25% thickness can be found at mid-span and inboard locations. At mid-span, aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root, structural requirements become more important. In this paper, the performance for the airfoil series DU FFA, S8xx, AH, Risø and NACA are reviewed. For the 25% and 30% thick airfoils, the best performing airfoils can be recognized by a restricted upper-surface thickness and an S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Risø-A1-24 (24%) airfoils are small. For a 30% thickness, the DU 97-W-300 meets the requirements best. Reduction of roughness sensitivity can be achieved both by proper design and by application of vortex generators on the upper surface of the airfoil. Maximum lift and lift-to-drag ratio are, in general, enhanced for the rough configuration when vortex generators are used. At inboard locations, 2-D wind tunnel tests do not represent the performance characteristics well because the influence of rotation is not included. The RFOIL code is believed to be capable of approximating the rotational effect. Results from this code indicate that rotational effects dramatically reduce roughness sensitivity effects at inboard locations. In particular, the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, DU 00-W-350 and DU 00-W-401, respectively, is remarkable. As a result of the strong reduction of roughness sensitivity, the design for inboard airfoils can primarily focus on high lift and structural demands.

Effects of leading-edge bevel angle on the aerodynamic forces of a non-slender 50° delta wing

2005 ◽  
Vol 109 (1098) ◽  
pp. 403-407 ◽  
Author(s):  
J. J. Wang ◽  
S. F. Lu
Keyword(s):  
Delta Wing ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Relative Thickness ◽  
Aerodynamic Performances ◽  
Stall Angle ◽  
Drag Ratio ◽  
Low Speed Wind Tunnel ◽  
Lift To Drag Ratio ◽  
Blunt Leading Edge

Abstract The aerodynamic performances of a non-slender 50° delta wing with various leading-edge bevels were measured in a low speed wind tunnel. It is found that the delta wing with leading-edge bevelled leeward can improve the maximum lift coefficient and maximum lift to drag ratio, and the stall angle of the wing is also delayed. In comparison with the blunt leading-edge wing, the increment of maximum lift to drag ratio is 200%, 98% and 100% for the wings with relative thickness t/c = 2%, t/c = 6.7% and t/c = 10%, respectively.

scholarly journals Lift-to-Drag Ratio Improvement on a Supersonic Transport by Leading-Edge Flap at Transonic Regions

2004 ◽  
Vol 52 (601) ◽  
pp. 65-71
Author(s):  
Dong-Youn Kwak ◽  
Katsuhiro Miyata ◽  
Masayoshi Noguchi ◽  
Kenji Yoshida ◽  
Kenichi Rinoie
Keyword(s):  
Leading Edge ◽  
Supersonic Transport ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Lift Augmentation between Passive and Active Vortex Generator

2016 ◽  
Vol 851 ◽  
pp. 532-537
Author(s):  
Nur Faraihan Zulkefli ◽  
Zulhilmy Sahwee ◽  
Nurhayati Mohd Nur ◽  
Muhamad Nor Ashraf Mohd Fazil ◽  
Muaz Mohd Shukri
Keyword(s):  
Reynolds Number ◽  
Lift Coefficient ◽  
Vortex Generator ◽  
Leading Edge ◽  
Plasma Actuator ◽  
Triangular Shape ◽  
Subsonic Wind Tunnel ◽  
Different Types ◽  
Drag Ratio ◽  
Lift To Drag Ratio

This study was conducted to investigate the performance of passive and active vortex generator on the wing’s flap. The triangular shape of passive vortex generator (VG) was developed and attached on the wing’s flap leading edge while the plasma actuator performed as active vortex generator. The test was carried out experimentally using subsonic wind tunnel with 300 angles extended flap. Three different types of turbulent flow; with Reynolds number 1.5 x105, 2.0 x105, and 2.6x105 were used to study the aerodynamics forces of airfoil with plasma actuator OFF. All Reynolds number used were below 1x106. The result indicated that airfoil with plasma actuator produced higher lift coefficient 12% and lift-to-drag ratio 5% compared to airfoil with passive vortex generator. The overall result showed that airfoil with plasma actuator produced better lift forces compared to passive vortex generator.

scholarly journals Lift Enhancement of NACA 4415 Airfoil using Biomimetic Shark Skin Vortex Generator

2019 ◽  
Vol 8 (4) ◽  
pp. 9231-9234
Keyword(s):  
Performance Enhancement ◽  
Incident Angle ◽  
Vortex Generator ◽  
Leading Edge ◽  
Vortex Generators ◽  
Shark Skin ◽  
Baseline Case ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

An experimental study was conducted to investigate the aerodynamic performance of the NACA 4415 airfoil with and without passive vortex generators. The measurement has been carried out for three considered cases: smooth airfoil for baseline case, airfoil with triangular vortex generator and also airfoil with shark skin shape vortex generator. Both the triangular and shark skin vortex generators were located at 50% of chord from leading edge of the airfoil with a 20° counter-rotating incident angle. The experiments were conducted with Reynold’s number of 100,000. Overall, the results indicate that the lift and drag coefficients, and lift-to-drag ratio, for the airfoil with sharkskin vortex generator are comparatively higher than the other airfoils at some angles of attack. The findings can be applied in optimizing shark skin shape vortex generator for the airfoil performance enhancement.

Modification impact on aerodynamic performance of hypersonic waverider

2011 ◽  
Vol 115 (1168) ◽  
pp. 325-334 ◽  
Author(s):  
C. Xiao-Qing ◽  
H. Zhong-Xi ◽  
L. Jian-Xia ◽  
G. Xian-Zhong
Keyword(s):  
Leading Edge ◽  
Aerodynamic Performance ◽  
Hypersonic Vehicles ◽  
Flow Conditions ◽  
Aerodynamic Coefficient ◽  
High Lift ◽  
Computational Fluid Dynamics Cfd ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Sharp Leading Edge

Abstract Waverider serves as a good candidate for hypersonic vehicles. The typical waverider has sharp leading edge and no control face, which is inappropriate for practical use. This paper puts forward a method modifying the waverider, and the modification impact on the performance of waverider at hypersonic flow conditions is studied. The modification is based on blunted waverider, includes cutting the tip and introducing two control wings. The modification’s effect on aerodynamic performance is obtained and analysed through Computational Fluid Dynamics (CFD) techniques. When blunted with 2cm radius, the waverider retains its good aerodynamic performance and the heat flux at the stagnation point can be managed. Three factors of the introduced wing are argued, the fixed angle, aspect ratio and wing area. Results show that influence on the aerodynamic coefficient is slight and the vehicle retains its high lift-to-drag ratio. The main influences of the modification are the control ability and trim efficiency, which is the motivation of this work and can be adapted when designing a practical waverider.

scholarly journals New Airfoils for Small Horizontal Axis Wind Turbines

1998 ◽  
Vol 120 (2) ◽  
pp. 108-114 ◽  
Author(s):  
P. Gigue`re ◽  
M. S. Selig
Keyword(s):  
Wind Turbines ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Horizontal Axis ◽  
Variable Speed ◽  
Edge Roughness ◽  
Horizontal Axis Wind Turbines ◽  
Wind Energy Systems ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In a continuing effort to enhance the performance of small wind energy systems, one root airfoil and three primary airfoils were specifically designed for small horizontal axis wind turbines. These airfoils are intended primarily for 1–5 kW variable-speed wind turbines for both conventional (tapered/twisted) or pultruded blades. The four airfoils were wind-tunnel tested at Reynolds numbers between 100,000 and 500,000. Tests with simulated leading-edge roughness were also conducted. The results indicate that small variable-speed wind turbines should benefit from the use of the new airfoils which provide enhanced lift-to-drag ratio performance as compared with previously existing airfoils.

Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils

2003 ◽  
Author(s):  
R. P. J. O. M. van Rooij ◽  
W. A. Timmer
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Leading Edge ◽  
Lower Surface ◽  
Wind Turbine Blades ◽  
Strong Reduction ◽  
High Lift ◽  
Edge Roughness ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In modern wind turbine blades airfoils of more than 25% thickness can be found at mid-span and inboard locations. In particular at mid-span aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root srtuctural requirements become more important. In this paper the performance for the airfoil series DU, FFA, S8xx, AH, Riso̸ and NACA are reviewed. For the 25% and 30% thick airfoils the best performing airfoils can be recognized by a restricted upper surface thickness and a S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Riso̸-A1-24 (24%) airfoil are small. For a 30% thickness the DU 97-W-300 meets the requirements best. At inboard locations the influence of rotation can be significant and 2d wind tunnel tests do not represent the characteristics well. The RFOIL code is believed to be capable of approximating the rotational effect. In particular the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, respectively DU 00-W-350 and DU 00-W–401, is remarkable. Due to the strong reduction of roughness sensitivity the design for inboard airfoils could primarily focus on high lift and structural demands.

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