Effect Of Gurney Flap Research Articles

Aerodynamic Performance Characteristics of NACA 0010 Cascade with Gurney Flaps

AbstractComputational investigations on the effect of Gurney flaps in a NACA 0010 cascade with a 90oblade angle were carried out using STARCCM+ code. The flaps were positioned at the trailing edge of the blades and were aligned at 45oand 90oto the blade chord. The variations in the lift, drag, aerodynamic efficiency and static pressure distributions were recorded on the blades and were compared with the baseline case. Significant increase in the lift coefficient was observed due to the Gurney flaps accompanied by a small drag penalty. This is achieved by increasing the effective camber of the blade, thereby increasing the pressure difference between the pressure and suction surfaces. The Gurney flaps increased the aerodynamic efficiency of the blade at lower angles of attack, whereas at higher angles a small drop in the value was observed.

The effects of Gurney flap on the aerodynamic performance of NACA 0012 airfoil in the rarefied gas flow

In this research, the rarefied gas flow around the NACA 0012 airfoil with attached Gurney flap at Mach number 2 and three different Knudsen numbers (0.026, 0.1 and 0.26) are studied, numerically. The effects of angle of attack and Gurney flap height on the aerodynamic characteristic of airfoil are investigated. At Kn = 0.026 the flow is simulated using Navier–Stokes equations with slip boundary conditions and DSMC method. In two other Kn numbers only the DSMC method is applied. For the clean airfoil, the calculated lift and drag coefficients and surface pressure distribution are compared with previous studies including the experimental and numerical results. This validation reveals that in the case of clean airfoil, there are a good agreement between the results of this study and those presented in literature. Furthermore, the effects of Gurney flap height on the lift and drag coefficients at different Knudsen numbers and angles of attack are studied. The results shows that for angles of attack smaller than 30°, the Gurney flap can improve the aerodynamics characteristics of airfoil. But, for angles of attack larger than 30° the Gurney flap does not have destructive effect on the aerodynamic characteristics.

Numerical simulation of gurney flaps lift-enhancement on a low reynolds number airfoil

Two-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations with transition shear stress transport (SST) model were solved to investigate the effects of Gurney flaps on the aerodynamic performance of a low Reynolds number airfoil. This airfoil was designed for flight vehicles operating at 20 km altitude with freestream velocity of 25 m/s. The chord length (C) of this airfoil is 5 m and the corresponding Reynolds number is 7.76×105. Gurney flaps with the heights ranging from 0.25%C to 3%C were investigated. It has been shown that Gurney flaps can enhance not only the prestall lift but also lift-to-drag ratio in a certain range of angles of attack. Specially, at cruise angle of attack (3°), Gurney flap with the height of 0.5%C can increase lift-to-drag ratio and lift coefficient by 1.6% and 12.8%, respectively. Furthermore, the mechanisms of Gurney flaps to improve the aerodynamic performance were illustrated by analyzing the surface pressure distribution, streamlines and trailing-edge flow structure for this low Reynolds number airfoil. Specially, distinguished from some other numerical researches, the flow details such as the laminar separation bubble and transition phenomena for low Reynolds number airfoil with Gurney flaps were investigated and it was found that Gurney flaps can delay the transition onset position at small angles of attack (≤2°). However, with the increase of angles of attack, Gurney flaps will promote the boundary layer transition.

Effect of Gurney Flaps on an Elliptical Airfoil

A low-speed wind tunnel investigation is presented characterizing the impact of Gurney flaps on an elliptical airfoil. The chordwise attachment location and height of the flaps were varied, as was the Reynolds number. The results showed strong nonlinearities in the lift curve which were present for all tested geometries. Flap effectiveness was seen to diminish as the flap was moved closer to the trailing edge stemming from flap submersion in separated flow. For the tested cases, the measured lift coefficients showed a weak Re dependency. The upper airfoil surface was shown to carry approximately 80% of the total lift load. The top surface caused a pitching moment reversal associated with nonlinearity in the lift curve.

Numerical investigation into energy extraction of flapping airfoil with Gurney flaps

A new type of Gurney flap is applied for energy extraction enhancement of a flapping airfoil. Two-dimensional Navier-Stokes simulations at Re = 104 are conducted to study the effect of Gurney flaps with various heights. The investigations are undertaken over a wide range of kinematic parameters (reduced frequency k, pitching amplitude θ0). Numerical results show that the application of a Gurney flap notably increases the maximum output power and efficiency compared with a clean NACA0012 airfoil. By affecting the flow structure and the pressure distribution around the trailing edge of the airfoil, the Gurney flap is beneficial to the lift force generation, thus leading to a higher power coefficient. The maximum power coefficient increases with Gurney flap height hg at first between hg = 0c–0.3c (c is the airfoil chord length), while a further increase in hg provides no further energy extraction enhancement. Besides, the increasing hg results in stronger trailing edge vortices and higher drag force.

Computational Investigations on the Effects of Gurney Flap on Airfoil Aerodynamics.

The present study comprises steady state, two-dimensional computational investigations performed on NACA 0012 airfoil to analyze the effect of Gurney flap (GF) on airfoil aerodynamics using k-ε RNG turbulence model of FLUENT. Airfoil with GF is analyzed for six different heights from 0.5% to 4% of the chord length, seven positions from 0% to 20% of the chord length from the trailing edge, and seven mounting angles from 30° to 120° with the chord. Computed values of lift and drag coefficients with angle of attack are compared with experimental values and good agreement is found at low angles of attack. In addition static pressure distribution on the airfoil surface and pathlines and turbulence intensities near the trailing edge are present. From the computational investigation, it is recommended that Gurney flaps with a height of 1.5% chord be installed perpendicular to chord and as close to the trailing edge as possible to obtain maximum lift enhancement with minimum drag penalty.

Experimental Investigation into the Effect of Gurney Flaps on Various Airfoils

The aerodynamic effects of the application of Gurney flaps of different heights and chordwise locations to five airfoils have been investigated in the Pennsylvania State University low-speed, low-turbulence wind tunnel. The effectiveness of each Gurney flap/airfoil combination is measured by the change in the maximum lift coefficient of the airfoil. When grouped by flap height and plotted against chordwise location, there is considerable scatter in the data, indicating that the effectiveness of the Gurney flap is strongly influenced by airfoil shape. Two anomalous cases are considered in detail. In the first case, the increase in is considerably different for two airfoils with the addition of a Gurney flap having the same height and mounted at the same chordwise location. The second case is one in which a Gurney flap of a specific height and mounting location is found to increase on one airfoil and decrease it on another. For these cases, pressure distributions, lift curves, and drag polars are provided. An explanation for the mechanism for the change in lift due to a Gurney flap is presented.

Effects of Gurney Flaps for Aerodynamic Characteristics of an Airfoil

Gurney flaps are the high-lift devices with L shape beam used for high speed road vehicles since 1970s. The aim of this research is to investigate effects of the Gurney flaps for aerodynamic characteristics of NACA4412 airfoil by wind-tunnel experiments. The flaps with height of 0 to 6% of the chord length are attached at the trailing edge. Under flow condition of Reynolds number 6.5×105, experimental setup is three-dimensional (3D) or quasi two-dimensional (2D), according to flow-fields without or with side plates. Consequently, the Gurney flaps made CL and stall angles higher: in 3D cases, the stall angles remarkably increased as the mounted flap was higher, while in 2D cases CL increased far more than in 3D cases at the same attack angle. The reason was explained by introduction of the idea of the imaginary aspect ratio. The reason was also confirmed by flow visualizations. Each family of polar curves for 2D or 3D measurements constitutes a curve like an envelope. By use of each “envelope”, when the necessary value of CL is given, combination of an attack angle and a flap height with the lowest value of CD can be obtained. As concluding remarks, usage of Gurney flaps is most effective to obtain high value of CL, with small and light wings, or when CD increases within tolerance level. 1.はじめに 自動車においては,形状最適化や翼などの空力装置を装 着することで下方向の揚力であるダウンフォースを増加さ せ,タイヤと路面の摩擦の目安となる摩擦円を大きくする ことが出来る.この効果により,カーブを横滑りなく高速 で走行することが可能(走行安定性向上)となるため,競 技用車両において最低旋回速度の向上を図ることができる. ダウンフォースは航空機の揚力と同様に,翼に高揚力装置 を装着することで更に増加させることが可能である. 本研究で扱う Gurney Flap は,翼下面後端に垂直に取り 付けられた板(Fig.1 参照)であり,コンパクトかつ軽量な Flap であるので,F1 などの競技用車両の翼の高揚力装置と して 1970 年代から使用されてきた.Liebeck による初期基 礎研究や,Kats による車両実用研究により Gurney Flap が 揚力係数を増加させることが確かめられた. Jang, Storms 等により基礎的な空気力学特性が示されて以来, タービン翼,ヘリコプター回転翼,振動翼,デルタ翼など 様々な翼への適用研究が行われてきた.他方,競技用車両 では規約の変更に伴い Gurney Flap の使用状況も変遷して いるが,空気力学の重要性が認識されてきたので空力特性 データは公表されていない.先に言及した Jang や Storms らの研究は,二次元流れにおいて,翼弦長に対す る Flap 高が 2%,もしくは 3%以下に限定された場合の成果 である.実際に自動車に翼を装着して走行するときには, 翼単体の場合である三次元流れ,もしくは翼端板を装着し た場合である準二次元流れとなり,また自動車では揚抗比 よりも揚力-重量比のほうが重要となる場合があるため, Flap 高が翼弦長の 3% 以上となることも強く想定される. そこで本研究では,より実際の流れに近い三次元流れと 準二次元流れにおいて,Flap 高を従来よりも大きな範囲で ある 6% まで変化させ,風洞実験により空力特性を調べる. 基準翼として NACA4412 を用い, 六分力測定により Gurney Flap の翼の空力特性への効果を明確にし,流れの可 視化により考察を検証する. 2.実験装置および測定条件 2.1 実験装置 本研究で用いる風洞(東海大学工学部航空宇宙工学科所 有の本田工業製回流式大型低速風洞)は吹出し口 1.0m× 1.5m,測定部長さ 2.0m,最大風速 40m/s である.翼に加わ る各分力は日章電器製のストラット型六分力天秤にて測定 を行う.天秤からのアナログ電圧信号は,A/D コンバータ (KEYENCE 製 NR-2000)を用いデジタル信号へと変換し, A/D コンバータ付属の波形保存ソフト WAVE SHOT!2000 により PC に記録する.可視化実験の際にはツクバリカセ イキ製の煙発生装置を使用する. 2.2 実験模型 実験では基準翼として,翼弦長 500mm,翼幅 900mm,ア スペクト比が 1.8 の NACA4412 翼型を用いた.この翼形状 を選択した理由は,Jang, Storms により Flap 高が翼弦長 の 2% 以下の場合の空力特性が示されており,本研究にお いて 6%高以下の空力特性のデータとして発展させること が可能だからである.Flap には翼幅と同じ幅 900mm の L 字 アングルを用い,翼装着面に対し直角に装着する.装着位 置は翼下面の翼後端と L 字アングルの後端が一致する位置 となる.Flap 高は翼弦長に対し 0%(Flap 無し),1% (5mm),2%(10mm),3%(15mm),4%(20mm), 5%(25mm),6%(30mm)である.Flap 付近の流れに対 するストラットの影響を軽減するために,Fig.1 のように翼 下面を上方にして翼模型をストラットにより支持する.支 持位置は翼中心線上において前縁より 50mm のメインスト ラット位置,後縁より 100mm のサブストラット位置である. 2.3 測定条件 本研究における実験風速は空力特性計測実験,可視化実 験共に Re=6.5×105となるよう 19.5 m/s とする.流れ場とし て,翼単体を設置する三次元流れ場,翼の両側にアクリル 板製の側壁板(1100mm× 1380mm)を設置する準二次元流 れ場(Fig.2)の二通りを扱う.迎角を変化させるために, 19 第 44 回流体力学講演会 /航空宇宙数値シミュレーション技術シンポジウム 2012 論文集 This document is provided by JAXA Fig.1 Wing Model Supported by Main and Sub Struts Front View Side View Fig.2 Quasi Two-Dimensional Flow Field 翼端と側壁板の間に両端それぞれ 5mm の隙間をあける. 2.3.1 空力特性測定実験 空力特性計測実験において,迎角は天秤操作部にて変更, サンプリングは 10ms 間隔で 1024 点の値の取得を 3 回行う. この3回の平均の値を計測値として空力特性を求める.実 験では二次元形状翼を使用するため,揚力,抗力,ピッチ ングモーメントの計測を行う.空力特性は,揚力係数 CL, 抗力係数 CD,計測したモーメントの係数 CM(メインスト ラット位置 xMC = 50mm まわりのモーメント),空力中心 xc/4 まわりのモーメント係数 CMAC,揚抗比 L/D,翼前縁か ら圧力中心までの距離 xCP などにより議論される.これら 諸量は,流体の密度 ρ,速度 U,翼面積(翼幅×翼弦長)A, 翼弦長 c,迎角 αを用いて次のように表される.

Gurney Flaps on Slender and Nonslender Delta Wings

*† ‡ A parametric low-speed wind tunnel study has been undertaken of the effect of Gurney flaps on the aerodynamic characteristics of slender and non-slender delta wings with sweep angles of 40°, 60° and 70°. In contrast to published data, no fundamental difference in behaviour with sweep angle was found. Gurney flaps were found to give similar lift and pitching moment changes to conventional hinged control surfaces, but with a much greater drag penalty. Gurney flap effectiveness was found to increase as sweep angle is reduced; a characteristic explained by a simple analysis of lift and drag on a sharp-edged delta wing. For a 40° sweep angle (typical of a UCAV configuration), Gurney flap deployment can significantly improve lift/drag ratio at higher incidences. Further improvements can be obtained by tapering or serrating the flap.

Effects of Gurney Flaps on an Annular Wing

F OR a constrained wing span, nonplanar wings exhibit significant aerodynamic benefits. These are generally indicated through increased lift curve slopes and reduced drag due to lift. These benefits are accrued through thewing capturing a larger volume of air to generate the lift impulse, and consequently the downwash at a point is reduced [1]. A simple biplane is a clear embodiment of nonplanarity. As the spacing between the upper and lower wings tends to infinity, the lift curve slope of the biplanewing tends to twice that of the equivalent monoplane, and the lift dependent drag tends to half that of the monoplane. Naturally, an infinitely spaced biplane or even that with a significant gap is not a practical design solution. As the gap between the biplanewings reduces, mutual wing interference effects reduce the nonplanar benefits. An annular (or ring) wing achieves the same aerodynamic benefits as an infinitely spaced biplane but with a maximum vertical wing spacing of the diameter of the ring. However, annular wings are hindered by their significant minimum drag coefficient that is largely due to their wetted area, which is 1.57 times greater than an equivalent projected span biplane of equal aspect ratio. Annular wings also suffer from pitch-up at stall due to dissimilar stall characteristics between the upper and lower wing halves [2]. Consequently, an active design space for annular wings is where flight operations at low speed (high loading) for extended duration are a design driver, as may be required for a small reconnaissance unmanned air vehicle [3]. Gurneyflaps have received considerable attention of late as simple devices capable of augmenting the lift of a wing or airfoil [4–7]. The flap itself is usually composed of a small metal tab, typically nomore then 1–2% of the chord attached perpendicular to the trailing edge on the pressure side (generally within the pressure side’s boundary layer). The flaps essentially work by violating the Kutta condition at the trailing edge; thus greater loading is carried over the aft section as final pressure recovery occurs in thewake. This also has the benefit of reduced pressure recovery demands on the upper surface boundary layer [5]. The flaps have also been observed to increase base suction; beneficial in delaying stall but also causing a drag increase. Flap inclination has been indicated to be favorable in reducing drag, and placement at the trailing edge is generally indicated as being themost advantageous [5]. Segmented flaps have been studied as a means to attenuate the drag penalty of the flaps by introducing instabilities into the wake, which culminate in the breakdown of the two-dimensional vortex street that has been observed aft of theflap [6]. Liftmodulation of an annular wing can be complicated due to the wing’s geometric shape; flaps or ailerons may require large end gaps for clearance. Consequently, a Gurney flap may prove an effective device for force andmomentmodulation on an annular wing. Lift augmentation of an annular wing usingGurney flaps is apparently not documented in the literature. Consequently, a study has been undertaken to elucidate the effects of various Gurney flap configurations and layouts on the aerodynamic characteristics of an annular wing.

Navier-Stokes Analysis of Airfoils with Gurney Flap

Two dimensional steady state Navier-Stokes computations were performed to determine the effect of Gurney flap on NACA 4412 and NACA 0011 airfoils. Gurney flap sizes selected for the study range from 0.5% to 4% of the airfoil chord. A compressible Navier-Stokes solver with Baldwin-Lomax turbulence model, JUMBO2D, is used to predict the flow field around the airfoils. Computed results have been compared with available experimental and computational data. There is good correlation observed between computed and experimental data. Addition of Gurney flap increases the lift coefficient significantly with very little drag penalty if proper Gurney flap height is selected. Nose down pitching moment also increases with Gurney flap height. Flow field structure near the trailing edge shows very good resemblance with Liebeckx2019;s hypothesis that provides the possible explanation for the increased aerodynamic performance

Two Aspects of Use of Full- and Partial-Span Gurney Flaps

Two Aspects of Use of Full- and Partial-Span Gurney Flaps

Effect of Gurney Flap on Unsteady Wake Vortex

Effect of Gurney Flap on Unsteady Wake Vortex

Experimental investigations on the effects of divergent trailing edge and Gurney flaps on a supercritical airfoil

Wind tunnel experiments were conducted to investigate the effects of divergent trailing edges and Gurney flaps on a supercritical airfoil at a Mach number M = 0.7 and a Reynolds number Re = 3.15 × 10 5 based on the airfoil chord length. The effects of Gurney flaps on a divergent trailing edge airfoil were also studied. Four Gurney flaps with heights h = 0.5 % , 1.0%, 1.5% and 2.0% chord length, respectively, were employed in this investigation. The results revealed that, in comparison with the divergent trailing edge, the Gurney flaps had significant effects on improving the aerodynamic characteristics of the tested supercritical airfoil, and even on the airfoil with divergent trailing edge. When the Gurney flaps were utilized, the lift coefficient, maximum lift coefficient and the maximum lift-to-drag ratio of both supercritical and divergent trailing edge airfoils were greatly increased. The lift-enhancing effects of Gurney flaps under high-speed circumstances mainly came from its ability of shifting backward the shock on the upper surface. Moreover, the installation of Gurney flaps will increase wave drag and base-pressure drag, but at the same time, the pressure on the lower surface of the airfoil was increased which led to an increased rear-body loading, and the position of the shock on the upper surface was greatly shifted backward, the supersonic region is thus enlarged, which led to an increased suction. Both the increments of pressure on the lower surface and suction on the upper surface resulted in a total lift increase. As the lift did not increase with the drag linearly, the lift-to-drag ratio increase and aerodynamic characteristics improvement were obtained under some circumstances.

Preliminary Parametric Study of Gurney Flap Dependencies

Introduction T HE Gurney flap1,2 is typically a small plate, which is attached at or near the trailing edge of an airfoil on the pressure side. The flap has been shown to be a highly effective small-scale (typically 0.5–1.5% of the chord) modification that can achieve significant lift and pitching-moment generation.1,2 The Gurney functions by essentially increasing the downward deflection of the trailingedge flow, facilitated through the formation of a series of counterrotating vortices similar to that of a von Karman vortex street. A subsequent effect is an apparent violation of the trailing-edge Kutta condition; experimental data show that finite loading is carried to the trailing edge. The Gurney flap increases the effective chord and camber of the airfoil, so by augmenting circulation. Liebeck3 suggested a flow pattern where a “virtual” cusped trailing edge is formed downstream of the Gurney from the shear layers merging downstream of the flap. The final pressure recovery would then occur off-surface, which is analogous to violation of the Kutta condition. Experimental and computational studies exploring the effect of Gurney flaps have been undertaken covering effects of flap height,4 angle,5 effects on multi-element airfoils,2 etc. In this Note, the database is increased through evaluation of the effects of flap porosity, inclination, and spacing from the surface. It would also be useful for experimental design and conceptual understanding to have correlations that relate Gurney-flap geometric parameters to performance. Consequently, such correlations are developed.

Trailing Vortex Rollup from a Wing Equipped with a Gurney Flap

Introduction T RAILING vortices and the hazard they pose to following aircraft have been studied by many researchers since the 1970s.1 Although many attempts to minimize the wake vortex problem have been examined, the strong adverse effect on the performance of the wake generating airplane has precluded their use. The present work explores the use of a Gurney flap as a wake vortex alleviation device. A Gurney flap is a narrow rectangular plate that is installed at the trailing edge of a wing on its pressure side as shown in Fig. 1. The typical height of the Gurney flap is 1–5% of the wing chord. The flap was first introduced by Gurney in the 1970s to improve the cornering speeds of racecars. Liebeck2 studied the effect of the Gurney flap on the performance of a Newman airfoil and found that a flap with a height of 0.01c increased the lift and decreased the drag. Storms and Jang examined the effect of a Gurney flap and/or vortex generator on the performance of a rectangular wing.3 They reported an augmentation of lift with Gurney flaps; this augmentation increased with increasing flap height. Ashby examined the effects of the height and location of Gurney flaps on the lift, drag, and pitching moment characteristics of a two-element rectangular wing.4 The effects of Gurney flaps on airfoils, wings, and a reflection plane model were investigated by Myose et al.5 The Gurney flap improved CL ,max of the flap-equipped configurations compared to the baseline configurations.5 Jeffrey et al. studied a single-element wing fitted with a Gurney flap.6 The Gurney flap increased the lift at a given prestall angle of attack but increased drag at most values of CL . Despite a reduction in the stall angle of attack, the Gurney flaps increased CL ,max. Buchholtz and Tso studied the effects of leadingedge fences and Gurney flaps, both separately and in combination, on the performance of a 60-deg delta wing.7 The Gurney flap was observed to increase the lift. Li and Wang tested delta wings with and without riblets and Gurney flaps.8 They found that all Gurney flaps increased CL and the larger flaps were more effective. Gai and Palfrey conducted experiments on a wing equipped with 0.05c Gurney flaps; both solid and serrated Gurney flaps were examined.9 Both flaps increased the lift, but reduced the stall angle of attack. The (L/D)max for both configurations was about 7% less than for the baseline configuration. Lin et al.10 tested a rectangular wing with a Gurney flap. The effects of the angle between the wing’s pressure surface and the flap and the distance between the flap and the wing trailing edge were studied. They found that all Gurney flap configu-

Gurney 플랩이 장착된 2차원 익형의 플러터 해석

Flutter analysis of NACA 0012 with Gurney flap was conducted in time domain. Flutter analysis was performed with a conjunction of two governing equations; one is 2D Navier-Stokes equation and, the other is Lagrange equation of two dimensional plunge & pitch model. Both governing equations were coupled by loose-coupling method. From the computed results, the effect of Gurney flap was concluded to move the flutter boundary of NACA 0012 downward, which means flutter occurs at lower speed than that of NACA 0012. Although flutter boundary of gurney flap was above the safety margin when mach number was lower than 0.85, there might be a possibility of crossing the safety margin when mach number was between 0.85 and 0.9. For safety, the effect of gurney flap needs to be investigated carefully before using it.

Experimental Study on Gurney Flap and Apex Flap on Delta Wing

The effects of Gurney flaps and apex flaps on the longitudinal aerodynamic performance of a delta wing with 70-deg sweepback angle were investigated in low-speed wind tunnel at a Reynolds number of 3.16 × × 10 5 based on the root chord of the delta wing. The experimental results indicate that the increment of lift coefficient can be obtained efficiently for different ranges of angle of attack with Gurney flaps and apex flaps, respectively. The study first tested the application of Gurney flaps together with an apex flap on the highly swept-back delta wing. The results show that they, used together, can greatly improve the longitudinal aerodynamic performance of the delta wing, and in this case the apex flap contributes much to the gains. The maximum lift-to-drag ratio can be achieved when the drooping angle of the apex flap is nearly equal to the angle of attack.

Summary of the Delft University Wind Turbine Dedicated Airfoils

This paper gives an overview of the design and wind tunnel test results of the wind turbine dedicated airfoils developed by Delft University of Technology (DUT). The DU-airfoils range in maximum relative thickness from 15% to 40% chord. The first designs were made with the XFOIL code. The computer program RFOIL, which is a modified version of XFOIL featuring an improved prediction around the maximum lift coefficient and the capability of predicting the effect of rotation on airfoil characteristics, has been used to design the airfoils since 1995. The measured effect of Gurney flaps, trailing edge wedges, vortex generators (vg) and trip wires on the airfoil characteristics of various DU-airfoils is presented. Furthermore, a relation between the thickness of the airfoil leading edge and the angle-of-attack for leading edge separation is given.

Influences of Mounting Angles and Locations on the Effects of Gurney Flaps

Experimental investigations were conducted on a NACA0012 airfoil to determine the influences of mounting angles and mounting locations on the lift-enhancing effects of Gurney flaps at a Reynolds number of 2.1 x 10 6 . The results revealed that all flaps of different mounting angles increased the lift coefficient, and an increment of maximum lift coefficient of 12.3, 15.1, and 17.4% was obtained by 45-, 60-, and 90-deg Gurney flap, respectively. There was a drag penalty associated with the lift enhancement. The best performance was obtained by the 45-deg Gurney flap for all flap deflections tested. When shifted forward from the trailing edge of the airfoil, the Gurney flap led to a decrease in lift, and an increment in drag, and thus a reduction in lift-to-drag ratio