Straight Wing Research Articles

Aerodynamic Investigations of a Morphing Membrane Wing

This paper presents the aerodynamic analysis of a morphing wing configuration using a compliant membrane as lifting surface to enable large variations of the planform geometry (aspect ratio and sweep angle) and airfoil shape. Comprehensive tests of a specifically designed wind-tunnel model including force measurements, deformation measurements, surface flow visualizations, and wake flow measurements are used to assess the aerodynamic behavior and the performances of this morphing wing. The results of the force measurements performed on five different wing configurations ranging from a high-aspect-ratio, straight wing to a highly swept back, low-aspectratio configuration show that the active variation of the wing planform effectively alters the lift and drag characteristics in such a way that relatively high lift-to-drag ratios can be maintained over a broad range of flight conditions.Inaddition,duetoitsmaterialproperties,thewingsurfacepassivelydeflectsunderaerodynamicloading, whichaffectstheairfoilshapeaccordingly.Itresultsin anadditional dependencyoftheaerodynamiccharacteristics on the flow conditions, which can be used for passive flow control.

Nonlinear bending-torsion flutter experiments of a medium-aspect-ratio flexible wing model

In this research a two-motion medium-aspect-ratio straight flexible wing model was tested. Tests with the wing model were conducted in the subsonic wind tunnel of the Faculty of Aerospace Engineering at the Technion, Israel. Experimental results obtained for flutter and Limit Cycle Oscillations (LCO) of the wing model are presented. At least two types of flutter and postflutter LCO have been observed. Both types were characterized by coupling between the torsional and bending modes. The first type flutter was associated with coupling of the first bending and first torsional modes, whereas the second type was observed for coupling of the first torsional and second bending modes.

Influences of upstream floor roughness and aerodynamic parameters on swept-wing junction flow

This study examines several finite length NACA 0012 airfoils to explore how the angle of attack (α), the sweep angle (Λ) and the Reynolds number (Re) affect the junction vortex and horseshoe vortex. Upstream floor roughness and turbulence intensity (T.I.) influence the wing-junction flow was also studied. The junction-flow structures at low Reynolds numbers were visualized using the smoke-wire technique. The smoke-streak flow patterns were classified into two characteristic modes — horseshoe vortex and non-horseshoe vortex. The horseshoe-vortex patterns were further categorized as the junction-vortex mode and non-junction-vortex mode. The velocity vectors were measured using the particle-image velocimetry (PIV), and the data was utilized to calculate the junction vorticity (Ω). Experimental results indicate that the straight wing has the maximum junction vorticity. The Ω decreases with increasing α and Λ and with decreasing Re. The Ω decreases with increasing T.I. The upstream T.I. generated by the mesh fences was more significant than that produced by sandpapers.

The Effect of Structural Geometric Nonlinearities on the Flutter of the Straight and Swept Wing Configurations

High altitude and long endurance (HALE) vehicle always adopt straight or swept configuration, which leads to the problem that the wings of UAV have high aspect ratio and are very flexible. This kind of flexible wing exhibits large deformation when aerodynamic forces are loaded on them and the structural nonlinearity should be considered. So the dynamic and flutter characteristics will be changed. In the engineering applications, the effects of structural geometric nonlinearities on the air vehicle design are the most concerns of aeroelasticity before a systematic flutter analysis for the air vehicle. because the solution for nonlinear flutter speed based on the CFD-CSD method is complex and time consuming. In this paper, we propose a simple and efficient approach that can analyze the effect of structural geometric nonlinearities on the flutter characteristics of high aspect ratio wing quickly. And a straight wing and a straight-swept wing are analyzed to verify the feasibility and efficiency of the proposed method. It is found that the effect of structural geometric nonlinearities has a strong effect on the flutter characteristic of the straight wing, but is weak on the straight-swept wing. And finally the impact of swept angle on the dynamic and flutter characteristics of straight-swept wing is also discussed.

Control of flow separation from a model wing at low Reynolds numbers

The results of an experimental investigation of the structure of the flow separated from the model of a straight wing with point sources of disturbances (bulges) made on its surface are presented. The variations in the three-dimensional flow pattern are analyzed as functions of the bulge shapes and positions. It is found that the flow can be controlled by means of mounting the bulges downstream of the separation line, in the return flow region, since in this case they hinder large-scale vortex formation in the separation zone. The results obtained show that there is an intimate connection between the vortices and the separation zone as a whole. Impeding the vortex structure formation can result in considerable variations in the separation zone structure, up to its complete disappearance.

Development of the Wave Packets-Forerunners at the Straight Wing Boundary Layer

This work is devoted to the study of wave packets (forerunners) formed in straight wing boundary layers in the regions preceding a drastic change in the flow velocity inside the boundary layer, near the fronts of streaks. The investigations were carried out in the subsonic low turbulence wind tunnel. Measurements of the flow fields were carried out using a single-wire probe of a constant-temperature hot-wire anemometer. It was shown that the localized structures, which modeled artificially from incoming flow, generate streaks in a boundary layer. The wave packets (forerunners) are appears in the regions preceding a drastic change of flow velocity inside the boundary layer at the streaks fronts. The characteristics of the forerunners, affected by the external-flow pressure gradient, intensity of streak, and local velocity gradients near the front of the streak were investigated

Design of the Grand Touring sports car wing: geometric and aerodynamic twist

Wing twist gives the Grand Touring sports car an eye-catching ‘aerodynamic shape’. From the functional viewpoint, wing twist may improve downforce, provide stall control and enhance aerodynamic efficiency if the twist is optimised. This study aims, first, to explore the influence of linear geometric and aerodynamic twist upon spanwise upwash velocity, downforce and induced drag distributions and, second, to evaluate the use of optimum twist in achieving minimum induced drag while preserving high downforce, in wings with linear taper for the Grand Touring car. Baseline wing prototypes were designed and fitted, subsequently, with a Gurney flap and endplates to obtain complete wings. Aerodynamics for straight wings and wings with geometric, aerodynamic and optimised twist were computed using modified versions of the Prandtl’s Lifting-line Theory. Straight and geometrically-twisted wings with constituent NACA 651-412 airfoils present superior aerodynamic efficiency at angles of attack ≤ 1° and may be used as stabilisers on high-speed circuits. Geometric twisting elicits a partial, rather than complete, wing stall that contributes to safety in motor racing. A geometrically-twisted wing constructed with a NASA LS(1)-0413 airfoil yields high downforce at the expense of large induced drag via a double-peaked induced drag distribution, and it is suitable for high-downforce racing circuits. Nonetheless, the analysis suggests that a twist-optimised wing for the Grand Touring car very nearly duplicates the ideal aerodynamic performance of an elliptic wing and yields high downforce and minimum possible induced drag. The findings support the implementation of optimum wing twist at the conceptual stages of Grand Touring sports car design.

Wing crack model subjected to high hydraulic pressure and far field stresses and its numerical simulation

By considering the effect of hydraulic pressure filled in wing crack and the connected part of main crack on the stress intensity factor at wing crack tip, a new wing crack model exerted by hydraulic pressure and far field stresses was proposed. By introducing the equivalent crack length l eq of wing crack, two terms make up the stress intensity factor K I at wing crack tip: one is the component K I (1) for a single isolated straight wing crack of length 2l subjected to hydraulic pressure in wing crack and far field stresses, and the other is the component K I (2) due to the effective shear stress induced by the presence of the equivalent main crack. The FEM model of wing crack propagation subjected to hydraulic pressure and far field stresses was also established according to different side pressure coefficients and hydraulic pressures in crack. The result shows that a good agreement is found between theoretical model of wing crack proposed and finite element method (FEM). In theory, an unstable crack propagation is shown if there is high hydraulic pressure and lateral tension. The wing crack model proposed can provide references for studying on hydraulic fracturing in rock masses.

A Study of Two Dimensional Airfoil for Straight Wing Non-Articulated Vertical Axis Wind Turbine

A Study of Two Dimensional Airfoil for Straight Wing Non-Articulated Vertical Axis Wind Turbine

A114 制御回路レス風力発電装置のフィールド試験結果(OS2 再生可能エネルギー)

In the current expansion of wind turbine generation, we propose the new wind turbine generator system (hereafter refer to as CC-less) optimized to the wind turbine. The CC-less consists of: the permanent magnet synchronous generator (PMG) which has several windings, reactor, and rectifier. In this paper, a new CC-less with the over speed brake function is proposed. The new CC-less consists of: PMG which has one winding, reactor, condenser, and rectifier. Currently, it was directly coupled with the straight wing non-articulated vertical axis wind turbine (SW-VAWT) and is examined in the roof of our company building. From the field test result and view, it has been confirmed that the new CC-less restrains the over speed of wind turbine.

A104 垂直軸型風車の性能予測と流れの可視化に関する研究(5)(OS2 再生可能エネルギー)

A104 垂直軸型風車の性能予測と流れの可視化に関する研究(5)(OS2 再生可能エネルギー)

A103 直線翼垂直軸型風力発電システムの翼型の実験的研究(OS2 再生可能エネルギー)

In this paper we will present some novel results of our research and development in the field of wind energy utilization. Our effort in this filed is mainly concentrated to the conceptual design of optimum airfoil sections for the blade of straight wing non-articulated vertical axis wind turbine which undergo cross wind motion. This concept was embodied in the design of a family of airfoil sections designated as TWT sections and a series of wind tunnel testing was conducted to confirm its desired aerodynamic characteristics. Then, we designed an experimental straight wing non-articulated vertical axis wind turbine system with straight blades to evaluate system performance and structural analysis results, and furthermore to collect operating experiences under real, fluctuating wind conditions.

The Research on Aeroelasticity of the Vehicle Wing Surface

By taking high aspect ratio straight wing as the research object, static aerodynamic force and dynamic aerodynamic force are detailed analysed and researched. The flutter speed of panel derived from Unsteady Theory and Theory.

Wing crack propagation model under high hydraulic pressure in compressive-shear stress state

A new wing crack model subjected to hydraulic pressure and far-field stresses was proposed considering the effect of hydraulic pressure in wing crack and the connected part of the main crack on the stress intensity factor at the wing crack tip. With the equivalent crack length leq of the wing crack introduced, the stress intensity factor KI at the wing crack tip was assumed to the sum of two terms: on one hand a component KI(1) for a single isolated straight wing crack of length 2l, and subjected to hydraulic pressure in the wing crack and far-field stresses; on the other hand a component KI(2) due to the effective shear stress induced by the presence of the equivalent main crack. The lateral tensile stress and hydraulic high pressure are the key factors that induce crack propagation unsteadily. The new wing crack theoretical model proposed can supply references for the study on hydraulic fracture in fractured masses, hydraulic fracturing in rock masses.

Influence of Turbulent Wake Upon Flow Separation on a Wing Model

The experimental investigations results of the flow over a straight wing model, placed at the subsonic wind tunnel are presented. The model was installed at high angle of attack so that the flow separation have place near the leading edge. An influence of external disturbances on such flow is studied. Free stream disturbances were generated by thin wire stretched in front of wing model. It is found that the separation can be completely removed when the wire wake achieve a wing upper surface

CAROLS: A New Airborne L-Band Radiometer for Ocean Surface and Land Observations

The “Cooperative Airborne Radiometer for Ocean and Land Studies” (CAROLS) L-Band radiometer was designed and built as a copy of the EMIRAD II radiometer constructed by the Technical University of Denmark team. It is a fully polarimetric and direct sampling correlation radiometer. It is installed on board a dedicated French ATR42 research aircraft, in conjunction with other airborne instruments (C-Band scatterometer—STORM, the GOLD-RTR GPS system, the infrared CIMEL radiometer and a visible wavelength camera). Following initial laboratory qualifications, three airborne campaigns involving 21 flights were carried out over South West France, the Valencia site and the Bay of Biscay (Atlantic Ocean) in 2007, 2008 and 2009, in coordination with in situ field campaigns. In order to validate the CAROLS data, various aircraft flight patterns and maneuvers were implemented, including straight horizontal flights, circular flights, wing and nose wags over the ocean. Analysis of the first two campaigns in 2007 and 2008 leads us to improve the CAROLS radiometer regarding isolation between channels and filter bandwidth. After implementation of these improvements, results show that the instrument is conforming to specification and is a useful tool for Soil Moisture and Ocean Salinity (SMOS) satellite validation as well as for specific studies on surface soil moisture or ocean salinity.

Influence of Wing Section and Wing Setting Angle on the Starting Performance of a Darrieus Wind Turbine with Straight Wings

Influence of Wing Section and Wing Setting Angle on the Starting Performance of a Darrieus Wind Turbine with Straight Wings

D204 垂直軸型風車の性能予測と流れの可視化に関する研究(3)(OS2 再生可能エネルギー(垂直軸風車の技術))

D204 垂直軸型風車の性能予測と流れの可視化に関する研究(3)(OS2 再生可能エネルギー(垂直軸風車の技術))

D202 直線翼垂直軸風車へのウイングレット導入による有効性の一検討(OS2 再生可能エネルギー(垂直軸風車の技術))

This paper describes the effectiveness of straight wing vertical-axis wind turbine with winglets. First of all, the effectiveness of winglets is analyzed the fluid analysis by the computer simulation. Next, the demonstration experiment is carried out. The contents of examination are the power generation characteristics and the performance of wind turbine. From these results, it was possible to show the introduction effect of the winglet.

Hotwire Measurement and Numerical Analysis of Flows around a Straight Wing Vertical Axis Wind Turbine

This paper describes the analysis of flows around a straight wing vertical axis wind turbine. Hotwire measurements in two-dimensional wind tunnel and numerical simulations are conducted. The rotor has two blades, whose airfoil is NACA0012 and the chord length is 0.1 of the rotor diameter. Reynolds number based on the uniform velocity and rotor diameter is 8.0 × 104. The tip speed ratio is 2.0. Incompressible Navier-Stokes equation is used for numerical simulation. A rotating coordinate system, which rotates at the same speed of the rotor, is employed. Both the experimental and numerical results are compared. As a result, the velocity fields show good agreements at each rotation angle, and the aerodynamic torque varies according to the flow condition, especially the flow separation.