Insect-like Wing Research Articles

NGHIÊN CỨU ẢNH HƯỞNG CỦA YẾU TỐ BIẾN DẠNG ĐẾN CÁC ĐẶC TÍNH KHÍ ĐỘNG CỦA CÁNH VẪY KIỂU CÔN TRÙNG Ở CHẾ ĐỘ BAY TREO

Insect-mimicking flapping-wing micro air vehicles (FWMAVs) are currently of great research interest due to their many practical applications. Most of the studies have focused on the rigid wing, which is much simpler. However, the wings of these FWMAVs, as well as those of insects in nature, are light and flexible structures, thus the deformation is unavoidable. In this study, a spring-body system is used to model the insect-like wing structure, combined with an aerodynamic program based on the UVLM model. The co-simulation framework is validated with published experimental data. Results show that using the flexible wing significantly increases the lift force as well as improves energy efficiency.

Aspect ratio studies on insect wings

The wing aspect ratio (AR), that is, the ratio of the wingspan to the mean wing chord, is the most important geometrical parameter describing an insect wing. While studies have shown that a change in AR affects the flow structure as well as the aerodynamic force components on wings, the reasons behind the wide variety of aspect ratios observed in nature remain underexplored. Further to this, motivated by the developments in micro-air vehicles (MAVs), determining an optimum AR is important for their efficient operation. While the effects on flow structure appear to be, at least superficially, broadly consistent across different studies, the effects on aerodynamic forces have been more strongly debated. Indeed, the considerable variation of force coefficients with AR in different studies suggests different optimal ARs. To help explain this, recent studies have pointed out the coupled effects of AR with other parameters. Specifically, the use of Reynolds and Rossby numbers based on alternative scalings helps to at least partially decouple the effects of AR and also to reconcile previous conflicting trends. This brief review presents an overview of previous studies on aspect-ratio effects of insectlike wings summarizing the main findings. The suggested alternative scalings of Reynolds and Rossby numbers, using the wingspan as the characteristic length, may be useful in aiding the selection of the optimal aspect ratios for MAVs in the future.

A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight.

A novel lifting line formulation is presented for the quasi-steady aerodynamic evaluation of insect-like wings in hovering flight. The approach allows accurate estimation of aerodynamic forces from geometry and kinematic information alone and provides for the first time quantitative information on the relative contribution of induced and profile drag associated with lift production for insect-like wings in hover. The main adaptation to the existing lifting line theory is the use of an equivalent angle of attack, which enables capture of the steady non-linear aerodynamics at high angles of attack. A simple methodology to include non-ideal induced effects due to wake periodicity and effective actuator disc area within the lifting line theory is included in the model. Low Reynolds number effects as well as the edge velocity correction required to account for different wing planform shapes are incorporated through appropriate modification of the wing section lift curve slope. The model has been successfully validated against measurements from revolving wing experiments and high order computational fluid dynamics simulations. Model predicted mean lift to weight ratio results have an average error of 4% compared to values from computational fluid dynamics for eight different insect cases. Application of an unmodified linear lifting line approach leads on average to a 60% overestimation in the mean lift force required for weight support, with most of the discrepancy due to use of linear aerodynamics. It is shown that on average for the eight insects considered, the induced drag contributes 22% of the total drag based on the mean cycle values and 29% of the total drag based on the mid half-stroke values.

Nonlinear Dynamic Modeling and Simulation of an Insect-Like Flapping Wing

The main objective of this paper is to present the modeling and simulation of open loop dynamics of a rigid body insect-like flapping wing. The most important aerodynamic mechanisms that explain the nature of the flapping flight, including added mass, rotational lift and delayed stall, are modeled. Wing flapping kinematics is described using appropriate reference frames and three degree of freedom for each wing with respect to the insect body. In order to simulate nonlinear differential equations of motion, 6DOF model of the insect-like flapping wing is developed, followed by an evaluation of the simulation results in hover condition.

Relationship between aerodynamic forces, flow structures and wing camber for rotating insect wing planforms

AbstractWing deformation is observed during the flight of some insect species; however, the effect of these distorted wing shapes on the leading edge vortex (LEV) is not well understood. In this study, we investigate the effect of one of these deformation parameters, (rigid) wing camber, on the flow structures and aerodynamic forces for insect-like wings, using a numerical model of an altered fruit fly wing revolving at a constant angular velocity. Both positive and negative camber was investigated at Reynolds numbers of 120 and 1500, along with the chordwise location of maximum camber. It was found that negatively cambered wings produce very similar LEV structures to non-cambered wings at both Reynolds numbers, but high positive camber resulted in the formation of multiple streamwise vortices at the higher Reynolds number, which disrupt the development of the main LEV. Despite this, positively cambered wings were found to produce higher lift to drag ratios than flat or negatively cambered wings. It was determined that a region of low pressure near the wing’s leading edge, combined with the curvature of the wing’s upper surface in this region, resulted in a vertical tilting of the net force vector for positively cambered wings, which explains how insects can benefit from wing camber.

Multi-Objective Genetic Algorithm for Hover Stabilization of an Insect-Like Flapping Wing

This paper describes latest results obtained on modeling, simulation and controller design of an insect-like Flapping Wing Micro Air Vehicle (FWMAV). Because of the highly nonlinear and time varying nature of insect flight and the inability to find an equilibrium point, linearization of the model without compromising the accuracy is not possible. Therefore, to address the problem of designing a controller capable of stabilizing and controlling the FWMAV around a hovering point, a metaheuristic optimization approach is proposed, based on the time averaging theorem. The results show that a controller, designed using the proposed method, is capable of stabilizing the FWMAV effectively around its hovering point.

Reynolds number and aspect ratio effects on the leading-edge vortex for rotating insect wing planforms

AbstractPrevious studies investigating the effect of aspect ratio ($\mathit{AR}$) for insect-like regimes have reported seemingly different trends in aerodynamic forces, however no detailed flow observations have been made. In this study, the effect of$\mathit{AR}$and Reynolds number on the flow structures over insect-like wings is explored using a numerical model of an altered fruit fly wing revolving at a constant angular velocity. Increasing the Reynolds number for an$\mathit{AR}$of 2.91 resulted in the development of a dual leading-edge vortex (LEV) structure, however increasing$\mathit{AR}$at a fixed Reynolds number generated the same flow structures. This result shows that the effects of Reynolds number and$\mathit{AR}$are linked. We present an alternative scaling using wing span as the characteristic length to decouple the effects of Reynolds number from those of$\mathit{AR}$. This results in a span-based Reynolds number, which can be used to independently describe the development of the LEV. Indeed, universal behaviour was found for various parameters using this scaling. The effect of$\mathit{AR}$on the vortex structures and aerodynamic forces was then assessed at different span-based Reynolds numbers. Scaling the flow using the wing span was found to apply when a strong spanwise velocity is present on the leeward side of the wing and therefore may prove to be useful for similar studies involving flapping or rotating wings at high angles of attack.

Approximate Aeroelastic Modeling of Flapping Wings in Hover

A nonlinear aeroelastic model suitable for flexible insectlike flapping wings in hover is presented. The aeroelastic model is obtained by coupling a nonlinear structural dynamic model based on MARC, with a potential-flow-based approximate aerodynamic model that consists of leading-edge vortices and a wake model. The aeroelastic response is obtained using an updated Lagrangian method. The paper describes validation studies conducted on the structural dynamic model, aerodynamic comparisons, and aeroelastic studies conducted on isotropic and anisotropic Zimmerman wings. The results demonstrate the suitability of MARC for modeling anisotropic wings undergoing insectlike wing kinematics. For the aeroelastic cases considered, the approximate model shows acceptable agreement with computational-fluid-dynamics-based and experimental results. The approximate model captured several important trends correctly.

Effect of flapping kinematics on the mean lift of an insect-like flapping wing

An experimental investigation of the effects of varying flapping kinematics on the mean lift produced by an insect-like flapping wing in hover is presented. This was performed with application to flapping-wing micro-air vehicles (FMAVs) in mind. Experiments were accomplished with a first-of-its-kind mechanical flapping-wing apparatus capable of reproducing a wide range of insect-like wing motions in air on the FMAV scale (~150 mm wingspan). This apparatus gives an insect-like wing the three controllable degrees of freedom required to produce the three separate motions necessary for mimicking an insect-like flapping-wing trajectory: sweeping (side to side), plunging (up and down), and pitching (angle of attack variation). Lift was measured via a force balance while the following kinematic parameters were varied: flapping frequency ( f ), angle of attack at mid-stroke (αmid), timing of pitch reversal with stroke reversal (rotation phase), stroke amplitude (Φ), and plunge amplitude (Θ). Results revealed that mean lift scaled with f 1.5 and varied proportionally with Φ. A pitch reversal advanced by up to 5 per cent of the flapping period relative to stroke reversal was found to maximize mean lift, and delayed pitch reversals were detrimental to mean lift. Of the parameters tested, mean lift was also maximized for αmid = 45° and Θ = 8.6°.

Optimal Hovering Kinematics of Flapping Wings for Micro Air Vehicles

This paper presents theoretical and experimental analyses of insect flapping mechanics and aerodynamics, with the aim of developing flapping-wing micro air vehicles. A model of an insect thorax flapping mechanism is developed that includes a quasi-steady aerodynamic model. Computer simulations of the thorax model show insectlike wing kinematics, including passive wing rotation at the end of the stroke. These kinematics are perturbed in a sequence of experiments using a robotic flapping-wing device to determine optimal hovering kinematics. Experiments are supported with numerical optimization based on the aerodynamic model. Apart from optimal kinematics, this study shows negative aerodynamic power required during wing rotation, which explains passive wing rotation at the end of the stroke.

Numerical and Experimental Simulations of Flapping Wings

This paper presents recent progress in a continuing investigation of the aeromechanical aspects of unsteady flapping wings for micro air vehicles (MAV). Numerical simulations were performed for two-dimensional (2D) pitching-plunging airfoils and three-dimensional (3D) flapping wings, mainly at hover conditions, using an in-house code called INSflow. The results were compared with available experimental data obtained in the water tunnel at the NRC-IAR. The investigation revealed that, at hover conditions, the vortices formed during the airfoil plunging motion may remain near the airfoil and affect new vortex formations, and thus the integral aerodynamic performance. In addition, the flow around the 3D insect-like wing is fully three-dimensional. The tip flow affects the flow separation, reducing the separation intensity. Two-dimensional calculations may over-predict the separation and the shedding vortices, thus affecting the generation of aerodynamic forces.

For insects, press print

With a 3D printer it's easy to fashion insect-like wings, the prelude to building the robotic spy that's high on the Pentagon's wish list

Artificial insect wings of diverse morphology for flapping-wing micro air vehicles

The development of flapping-wing micro air vehicles (MAVs) demands a systematic exploration of the available design space to identify ways in which the unsteady mechanisms governing flapping-wing flight can best be utilized for producing optimal thrust or maneuverability. Mimicking the wing kinematics of biological flight requires examining the potential effects of wing morphology on flight performance, as wings may be specially adapted for flapping flight. For example, insect wings passively deform during flight, leading to instantaneous and potentially unpredictable changes in aerodynamic behavior. Previous studies have postulated various explanations for insect wing complexity, but there lacks a systematic approach for experimentally examining the functional significance of components of wing morphology, and for determining whether or not natural design principles can or should be used for MAVs. In this work, a novel fabrication process to create centimeter-scale wings of great complexity is introduced; via this process, a wing can be fabricated with a large range of desired mechanical and geometric characteristics. We demonstrate the versatility of the process through the creation of planar, insect-like wings with biomimetic venation patterns that approximate the mechanical properties of their natural counterparts under static loads. This process will provide a platform for studies investigating the effects of wing morphology on flight dynamics, which may lead to the design of highly maneuverable and efficient MAVs and insight into the functional morphology of natural wings.

Shape-memory alloy actuation of insect-like flapping wings

This paper presents the results from an exploratory investigation into the real-time shape adaptation of an artificial insect-like wing. insect-like flapping flight offers many aerodynamic advantages at small scales, <150mm, compared to more conventional approaches to flight. However, it requires the implementation of low band-width high strain adaptation of aerofoil shape. The incorporation of Shape-Memory (SM) alloy actuators within composite wingforms offers one solution to such shape-changes. The results of this preliminary programme show that it is possible to introduce 'twist' and saddle-shapes into insect-like wings using integrated SM actuators. This offers the potential for real-time adaptation of angle of attack during upstroke and structural stiffening during downstroke of a flapping wing. The paper also shows that these effects can be simply modelled by FE, analysis providing accurate data for SM actuator performance is available.