scholarly journals Chordwise wing flexibility may passively stabilize hovering insects

2018 ◽  
Vol 15 (147) ◽  
pp. 20180409 ◽  
Author(s):  
James E. Bluman ◽  
Madhu K. Sridhar ◽  
Chang-kwon Kang
Keyword(s):  
Stokes Equations ◽  
Insect Flight ◽  
Flight Dynamics ◽  
Fruit Fly ◽  
Flapping Wing ◽  
Wing Shape ◽  
Horizontal Velocity ◽  
Integration Scheme ◽  
System Matrix ◽  
Flexible Wings

Insect wings are flexible, and the dynamically deforming wing shape influences the resulting aerodynamics and power consumption. However, the influence of wing flexibility on the flight dynamics of insects is unknown. Most stability studies in the literature consider rigid wings and conclude that the hover equilibrium condition is unstable. The rigid wings possess an unstable oscillatory mode mainly due to their pitch sensitivity to horizontal velocity perturbations. Here, we show that a flapping wing flyer with flexible wings exhibits stable hover equilibria. The free-flight insect flight dynamics are simulated at the fruit fly scale in the longitudinal plane. The chordwise wing flexibility is modelled as a linear beam. The two-dimensional Navier–Stokes equations are solved in a tight fluid–structure integration scheme. For a range of wing flexibilities similar to live insects, all eigenvalues of the system matrix about the hover equilibrium have negative real parts. Flexible wings appear to stabilize the unstable mode by passively deforming their wing shape in the presence of perturbations, generating significantly more horizontal velocity damping and pitch rate damping. These results suggest that insects may passively stabilize their hover flight via wing flexibility, which can inform designs of synthetic flapping wing robots.

scholarly journals Mathematical Modelling of Near-Hover Insect Flight Dynamics

2010 ◽  
Author(s):  
B. Cheng ◽  
X. Deng
Keyword(s):  
Mathematical Model ◽  
Insect Flight ◽  
Control Strategies ◽  
Flight Dynamics ◽  
Analytical Approximation ◽  
Morphological Data ◽  
Oscillatory Mode ◽  
System Matrix ◽  
Lateral Velocity ◽  
Lateral Instability

Using a dynamically scaled robotic wing, we studied the aerodynamic torque generation of flapping wings during roll, pitch, and yaw rotations of the stroke plane. The total torque generated by a wing pair with symmetrical motions was previously known as flapping counter-torques (FCTs). For all three types of rotation, stroke-averaged FCTs act opposite to the directions of rotation and are collinear with the rotational axes. Experimental results indicate that the magnitude of FCTs is linearly dependent on both the flapping frequency and the angular velocity. We also compared the results with predictions by a mathematical model based on quasi-steady analyses, where we show that FCTs can be described through consideration of the asymmetries of wing velocity and the effective angle of attack caused by each type of rotation. For roll and yaw rotations, our model provided close estimations of the measured values. However, for pitch rotation the model tends to underestimate the magnitude of FCT, which might result from the effect of the neglected aerodynamics, especially the wake capture. Similar to the FCT, which is induced by body rotation, we further provide a mathematical model for the counter force induced by body translation, which is termed as flapping counter-force (FCF). Based on the FCT and FCF models, we are able to provide analytical estimations of stability derivatives and to study the flight dynamics at hovering. Using fruit fly (Drosophila) morphological data, we calculated the system matrix of the linearized flight dynamics. Similar to previous studies, the longitudinal dynamics consist of two stable subsidence modes with fast and slow time constants, as well as an unstable oscillatory mode. The longitudinal instability is mainly caused by the FCF induced by an initial forward/backward velocity, which imparts a pitch torque to the same direction of initial pitch velocity. Similarly, the lateral dynamics also consist of two stable subsidence modes and an unstable oscillatory mode. The lateral instability is mainly caused by the FCF induced by an initial lateral velocity, which imparts a roll torque to the same direction of initial roll velocity. In summary, our models provide the first analytical approximation of the six-degree-of-freedom flight dynamics, which is important in both studying the control strategies of the flying insects and designing the controller of the future flapping-wing micro air vehicles (MAVs).

scholarly journals Quasi-Steady versus Navier–Stokes Solutions of Flapping Wing Aerodynamics

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 81 ◽  
Author(s):  
Jeremy Pohly ◽  
James Salmon ◽  
James Bluman ◽  
Kabilan Nedunchezian ◽  
Chang-kwon Kang
Keyword(s):  
Stokes Equations ◽  
Aerodynamic Force ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Fruit Fly ◽  
Flapping Wing ◽  
Navier Stokes ◽  
Pitching Motion ◽  
Navier Stokes Equations ◽  
Wing Motion

Various tools have been developed to model the aerodynamics of flapping wings. In particular, quasi-steady models, which are considerably faster and easier to solve than the Navier–Stokes equations, are often utilized in the study of flight dynamics of flapping wing flyers. However, the accuracy of the quasi-steady models has not been properly documented. The objective of this study is to assess the accuracy of a quasi-steady model by comparing the resulting aerodynamic forces against three-dimensional (3D) Navier–Stokes solutions. The same wing motion is prescribed at a fruit fly scale. The pitching amplitude, axis, and duration are varied. Comparison of the aerodynamic force coefficients suggests that the quasi-steady model shows significant discrepancies under extreme pitching motions, i.e., the pitching motion is large, quick, and occurs about the leading or trailing edge. The differences are as large as 1.7 in the cycle-averaged lift coefficient. The quasi-steady model performs well when the kinematics are mild, i.e., the pitching motion is small, long, and occurs near the mid-chord with a small difference in the lift coefficient of 0.01. Our analysis suggests that the main source for the error is the inaccuracy of the rotational lift term and the inability to model the wing-wake interaction in the quasi-steady model.

scholarly journals FLAPPING WING DEVICES FOR MARS EXPLORATION

2011 ◽  
Author(s):  
Asier Ania ◽  
Dominique Poirel ◽  
Marie-Josée Potvin ◽  
Steeve Montminy
Keyword(s):  
Reynolds Number ◽  
Insect Flight ◽  
Low Reynolds Number ◽  
Flapping Wing ◽  
Low Density ◽  
Mars Exploration ◽  
Unsteady Aerodynamic ◽  
Aerial Vehicle ◽  
Low Reynolds

The use of an aerial vehicle would greatly enhance the domain of exploration on Mars. The main constraint in such a design would be the extreme Martian environment. The low-density atmosphere suggests the use of a low Reynolds number flight regime modeled after flapping wing insect flight. This flapping wing flight employs several unsteady aerodynamic mechanisms; delayed stall, wake capture, and rotational mechanisms. Two prototypes, a flapping wing and a rotary-flapping wing hybrid, have been built and will be tested in order to quantify the 'overall lift' generated and allow us to evaluate the efficacy of flapping wing flight on Mars.

Longitudinal Flight Dynamics of Flapping-Wing Micro Air Vehicles

2012 ◽  
Vol 35 (4) ◽  
pp. 1115-1131 ◽  
Author(s):  
Christopher T. Orlowski ◽  
Anouck R. Girard
Keyword(s):  
Flight Dynamics ◽  
Micro Air Vehicles ◽  
Flapping Wing ◽  
Air Vehicles

Lift and power requirements of hovering flight inDrosophila virilis

2002 ◽  
Vol 205 (16) ◽  
pp. 2413-2427 ◽  
Author(s):  
Mao Sun ◽  
Jian Tang
Keyword(s):  
Flight Control ◽  
Stokes Equations ◽  
Fruit Fly ◽  
The Body ◽  
Drosophila Virilis ◽  
Specific Power ◽  
Aerodynamic Forces ◽  
Hovering Flight ◽  
Power Expenditure ◽  
The Mean

SUMMARYThe lift and power requirements for hovering flight in Drosophila virilis were studied using the method of computational fluid dynamics. The Navier-Stokes equations were solved numerically. The solution provided the flow velocity and pressure fields, from which the unsteady aerodynamic forces and moments were obtained. The inertial torques due to the acceleration of the wing mass were computed analytically. On the basis of the aerodynamic forces and moments and the inertial torques, the lift and power requirements for hovering flight were obtained.For the fruit fly Drosophila virilis in hovering flight (with symmetrical rotation), a midstroke angle of attack of approximately 37°was needed for the mean lift to balance the insect weight, which agreed with observations. The mean drag on the wings over an up- or downstroke was approximately 1.27 times the mean lift or insect weight (i.e. the wings of this tiny insect must overcome a drag that is approximately 27 % larger than its weight to produce a lift equal to its weight). The body-mass-specific power was 28.7 W kg-1, the muscle-mass-specific power was 95.7 W kg-1 and the muscle efficiency was 17 %.With advanced rotation, larger lift was produced than with symmetrical rotation, but it was more energy-demanding, i.e. the power required per unit lift was much larger. With delayed rotation, much less lift was produced than with symmetrical rotation at almost the same power expenditure; again, the power required per unit lift was much larger. On the basis of the calculated results for power expenditure, symmetrical rotation should be used for balanced, long-duration flight and advanced rotation and delayed rotation should be used for flight control and manoeuvring. This agrees with observations.

Flight Dynamics of Flapping-Wing Air Vehicle

2008 ◽  
Author(s):  
Roman Krashanitsa ◽  
Dmitry Silin ◽  
Sergey Shkarayev ◽  
Gregg Abate
Keyword(s):  
Flight Dynamics ◽  
Flapping Wing ◽  
Air Vehicle

A Conceptual Model of Flapping-Wing Mechanism Inspired from the Results of Numerical Study

2013 ◽  
Vol 397-400 ◽  
pp. 783-788
Author(s):  
Xing Wei Zhang ◽  
Chao Wang ◽  
Hang Liu
Keyword(s):  
Conceptual Model ◽  
Power Efficiency ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flapping Wing ◽  
Numerical Results ◽  
Navier Stokes ◽  
Active Deformation ◽  
Navier Stokes Equations ◽  
Wing Model

This paper investigates the aerodynamic forces of several plunging wing models by means of computational fluid dynamics. A finite volume method was used to solve the two-dimensional unsteady incompressible Navier-Stokes equations. The forces and power efficiency have been calculated and compared between sets of different models. Current work found that the nonsymmetrical moving can enhance the lift and thrust forces. The numerical results also prove that the flexible wing model can be use to improve the efficiency and reduce the input. Additionally, a new conceptual model for flapping wing mechanism with active deformation and adaptive nonsymmetrical driving motion is proposed base on the numerical results.

Influence of wing kinematics on aerodynamic performance in hovering insect flight

2007 ◽  
Vol 594 ◽  
pp. 341-368 ◽  
Author(s):  
FRANK M. BOS ◽  
D. LENTINK ◽  
B. W. VAN OUDHEUSDEN ◽  
H. BIJL
Keyword(s):  
Insect Flight ◽  
Fruit Fly ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Insect Wing ◽  
Wing Kinematics ◽  
Drag Forces ◽  
Kinematic Models ◽  
Characteristic Features ◽  
Lift And Drag

The influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled at Re = 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied.The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.

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