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

Vortex force of an impulsively started plate at high angle of attack

2017 ◽  
Vol 27 (11) ◽  
pp. 2402-2414
Author(s):  
Xiang Fu ◽  
Gaohua Li ◽  
Fuxin Wang
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Forces ◽  
Total Drag ◽  
Content Type ◽  
Vortical Structures ◽  
Edge Vortex ◽  
The Individual ◽  
Practical Implications

Purpose A quantitative study that can identify the primary aerodynamic forces and relate them to individual vortical structures is lacking. The paper aims to clarify the quantitative relationships between the aerodynamic forces and vortical structures. Design/methodology/approach The various contributions to the aerodynamic forces on the two-dimensional impulsively started plate are investigated from the perspective of the vorticity moment theorem. The angles of attacks are set to 45°, 58.5° and 72°, while the Reynolds number is 10,000 based on the chord length. Compared with the traditional pressure force analysis, this theorem not only tells us the total aerodynamic force during the motion, but also enables us to quantify the forces contributed from the fluid elements with non-zero vorticity. Findings It is found that the time-dependent force behaviors are dominated by the formations and evolutions of these vortical structures. The analysis of the time-averaged forces demonstrates that the lift contributed from the leading edge vortex (LEV) is nearly four times larger than the total lift and the drag contributed from the starting vortex (SV) is almost equal to the total drag when the angle of attack (AoA) increases to 72°, which means the LEV is “lift structure” whereas the SV is “drag structure”. Practical implications The present method provides a better perspective for flow control and drag reduction by relating the forces directly to the individual vorticity structures. Originality/value In this paper, the Vorticity Moment Theory is first used to study the quantitative relationships between the aerodynamic forces and the vortices.

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.

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.

Experimental Study on the Forward Flight of the Hawkmoth Using the Dynamically Scaled-Up Robotic Model

2015 ◽  
Author(s):  
Jong-seob Han ◽  
Jae-Hung Han ◽  
Jo Won Chang
Keyword(s):  
Experimental Study ◽  
Flow Regime ◽  
Aerodynamic Forces ◽  
Forward Flight ◽  
Hovering Flight

DARPA’s MAV project has accelerated a lot of studies on insect flights to gain insights for flapping MAV development [1]. In particular, the insects adept at hovering have become major subjects of these investigations [2–3]. Due to the great contributions by pioneers, we are now able to well explain how the insects produce the enhanced aerodynamic forces in the hovering flight at intricate flow regime [4].

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