Wing kinematics and aerodynamic forces in miniature insect Encarsia formosa in forward flight

2021 ◽  
Vol 33 (2) ◽  
pp. 021905
Author(s):  
Xin Cheng ◽  
Mao Sun
Keyword(s):  
Encarsia Formosa ◽  
Aerodynamic Forces ◽  
Forward Flight ◽  
Wing Kinematics

Effects of Flapping Wing Kinematics on Hovering and Forward Flight Aerodynamics

AIAA Journal ◽  
2011 ◽  
Vol 49 (8) ◽  
pp. 1750-1762 ◽  
Author(s):  
Hiroto Nagai ◽  
Koji Isogai
Keyword(s):  
Flapping Wing ◽  
Forward Flight ◽  
Wing Kinematics

scholarly journals Aerodynamic forces and vortical structures in flapping butterfly's forward flight

2013 ◽  
Vol 25 (2) ◽  
pp. 021902 ◽  
Author(s):  
Naoto Yokoyama ◽  
Kei Senda ◽  
Makoto Iima ◽  
Norio Hirai
Keyword(s):  
Aerodynamic Forces ◽  
Forward Flight ◽  
Vortical Structures

scholarly journals Parametric study of a corrugated airfoil in a forward flight at ultra-low Reynolds number

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Mahmoud E. Abd El-Latief ◽  
Khairy Elsayed ◽  
Mohamed M. Abdelrahman
Keyword(s):  
Reynolds Number ◽  
Phase Difference ◽  
Lift Force ◽  
Thrust Force ◽  
Angle Of Attack ◽  
Initial Angle ◽  
Aerodynamic Forces ◽  
Forward Flight ◽  
Propulsive Efficiency ◽  
Stroke Amplitude

AbstractIn the current study, the mid cross section of the dragonfly forewing was simulated at ultra-low Reynolds number. The study aims to understand better the contribution of corrugations found along the wing on the aerodynamic performance during a forward flight. Different flapping parameters were employed. FLUENT solver was used to solve unsteady, two-dimensional, laminar, incompressible Navier–Stokes equations. The results revealed that any stroke amplitude less than 1cm generated no thrust force. The stroke amplitude had to be increased to form the reversed Kármán vortices responsible for generating thrust force. The highest propulsive efficiency was found in the Strouhal number range 0.2 < St < 0.4 with a peak efficiency of 57% at St = 0.39. Changing the phase difference between pitching and plunging motions from advanced to synchronized caused lift force to drop 91% and thrust force to increase by 15%. On the other hand, changing the phase difference from synchronized to delayed caused lift and thrust forces to increase by 89% and 36%, respectively, and propulsive efficiency to deteriorate significantly. In all performed simulations, the airfoil was assumed to start motion from rest with no initial angle of attack. The increase in initial angle of attack generates a very high lift force with a fair loss for both thrust force and propulsive efficiency. The decomposition of flapping motion into its elementary motions revealed that the aerodynamic forces generated are a non-linear superposition from both pure pitching and pure plunging aerodynamic forces. This can be attributed to the non-linear interaction between unsteady vortices generated from these decomposed motions.

scholarly journals The control of flight force by a flapping wing: lift and drag production

2001 ◽  
Vol 204 (15) ◽  
pp. 2607-2626 ◽  
Author(s):  
Sanjay P. Sane ◽  
Michael H. Dickinson
Keyword(s):  
High Performance ◽  
Time Course ◽  
Aerodynamic Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Force Sensor ◽  
Aerodynamic Forces ◽  
Wing Kinematics ◽  
The Mean ◽  
Stroke Amplitude

SUMMARYWe used a dynamically scaled mechanical model of the fruit fly Drosophila melanogaster to study how changes in wing kinematics influence the production of unsteady aerodynamic forces in insect flight. We examined 191 separate sets of kinematic patterns that differed with respect to stroke amplitude, angle of attack, flip timing, flip duration and the shape and magnitude of stroke deviation. Instantaneous aerodynamic forces were measured using a two-dimensional force sensor mounted at the base of the wing. The influence of unsteady rotational effects was assessed by comparing the time course of measured forces with that of corresponding translational quasi-steady estimates. For each pattern, we also calculated mean stroke-averaged values of the force coefficients and an estimate of profile power. The results of this analysis may be divided into four main points.(i) For a short, symmetrical wing flip, mean lift was optimized by a stroke amplitude of 180° and an angle of attack of 50°. At all stroke amplitudes, mean drag increased monotonically with increasing angle of attack. Translational quasi-steady predictions better matched the measured values at high stroke amplitude than at low stroke amplitude. This discrepancy was due to the increasing importance of rotational mechanisms in kinematic patterns with low stroke amplitude.(ii) For a 180° stroke amplitude and a 45° angle of attack, lift was maximized by short-duration flips occurring just slightly in advance of stroke reversal. Symmetrical rotations produced similarly high performance. Wing rotation that occurred after stroke reversal, however, produced very low mean lift.(iii) The production of aerodynamic forces was sensitive to changes in the magnitude of the wing’s deviation from the mean stroke plane (stroke deviation) as well as to the actual shape of the wing tip trajectory. However, in all examples, stroke deviation lowered aerodynamic performance relative to the no deviation case. This attenuation was due, in part, to a trade-off between lift and a radially directed component of total aerodynamic force. Thus, while we found no evidence that stroke deviation can augment lift, it nevertheless may be used to modulate forces on the two wings. Thus, insects might use such changes in wing kinematics during steering maneuvers to generate appropriate force moments.(iv) While quasi-steady estimates failed to capture the time course of measured lift for nearly all kinematic patterns, they did predict with reasonable accuracy stroke-averaged values for the mean lift coefficient. However, quasi-steady estimates grossly underestimated the magnitude of the mean drag coefficient under all conditions. This discrepancy was due to the contribution of rotational effects that steady-state estimates do not capture. This result suggests that many prior estimates of mechanical power based on wing kinematics may have been grossly underestimated.

Kinematic Variation and Modeling for Design in Ornithoptic Flight

Materials ◽  
2005 ◽  
Author(s):  
John M. Dietl ◽  
Ephrahim Garcia
Keyword(s):  
Genetic Algorithm ◽  
Mathematical Model ◽  
Flow Field ◽  
Power Consumption ◽  
Degrees Of Freedom ◽  
Flapping Flight ◽  
Kinematic Parameters ◽  
Aerodynamic Forces ◽  
Forward Flight ◽  
Strip Theory

During soaring forward flight, larger birds such as raptors generate most of their lift in a manner consistent with the lift generated by fixed-wing aircraft. However, in flapping flight there is an additional flow field that must be superimposed to account for thrust generated. The aerodynamic forces can be analyzed using conventional strip theory techniques and integrated across the wingspan and over the entire flapping cycle. Oscillating wing pitch causes the lift vector to contribute to forward thrust and effects useful angles of attack. This paper seeks to predict which kinematic parameters of flapping flight will allow for sustained forward flight. Using a mathematical model for flapping flight and a genetic algorithm, kinematic parameters are selected that provide sufficient lift and thrust while attenuating aerodynamic power consumption. The results show that separate degrees of freedom are necessary for twisting and heaving motions to yield acceptable flight conditions.

scholarly journals Very small insects use novel wing flapping and drag principle to generate the weight-supporting vertical force

2018 ◽  
Vol 855 ◽  
pp. 646-670 ◽  
Author(s):  
Xin Cheng ◽  
Mao Sun
Keyword(s):  
Steady Motion ◽  
The Other ◽  
Vertical Force ◽  
Encarsia Formosa ◽  
Viscous Effects ◽  
Insect Wing ◽  
Wing Kinematics ◽  
Generation Mechanisms ◽  
Starting Flow ◽  
First Time

The effect of air viscosity on the flow around an insect wing increases as insect size decreases. For the smallest insects (wing length$R$below 1 mm), the viscous effect is so large that lift-generation mechanisms used by their larger counterparts become ineffective. How the weight-supporting vertical force is generated is unknown. To elucidate the aerodynamic mechanisms responsible, we measure the wing kinematics of the tiny waspEncarsia formosa(0.6 mm $R$) in hovering or very slow ascending flight and compute and analyse the aerodynamic forces. We find that the insects perform two unusual wing motions. One is ‘rowing’: the wings move fast downward and backward, like stroking oars. The other is the previously discovered Weis-Fogh ‘fling’. The rowing produces 70 % of the required vertical force and the Weis-Fogh ‘fling’ the other 30 %. The oaring wing mainly produces an approximately up-pointing drag, resulting in the vertical force. Because each oaring produces a starting flow, the drag is unsteady in nature and much greater than that in steady motion at the same velocities and angles of attack. Furthermore, our computation shows that if the tiny wasps employed the usual wing kinematics of the larger insects (flapping back and forth in a horizontal plane), the vertical force produced would be only$1/3$of that by the real wing kinematics; i.e. they must use the special wing movements to overcome the problem of large viscous effects encountered by the commonly used flapping kinematics. We have observed for the first time very small insects using drag to support their weight and we explain how a net vertical force is generated when the drag principle is applied.

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