Experimental Study on the Effect of Skin Flexibility on Aerodynamic Performance of Flapping Wings for Micro Air Vehicles

2014 ◽  
Vol 629 ◽  
pp. 18-23 ◽  
Author(s):  
Hamid Yusoff ◽  
Mohd Zulkifly Abdullah ◽  
Kamarul Arifin Ahmad ◽  
M.K. Abdullah ◽  
Shafiq Suhaimi
Keyword(s):  
High Speed ◽  
Orientation Angle ◽  
Aerodynamic Performance ◽  
Flapping Flight ◽  
Production Performance ◽  
Steady Regime ◽  
Flapping Motion ◽  
Advance Ratio ◽  
Lift And Drag ◽  
Rigid Wing

In the present study, the aerodynamic characteristics such as time-averaged lift and drag generation of two flexible membrane (latex thin and thick) wings with different skin flexibilities are compared with those of a conventional rigid (wood) wing to assess the effects of skin flexibility (rigidity) on the aerodynamic performance for flapping flight applications. The experiments are performed in an open circuit wind tunnel of non-return airflow with a test section of (0.3m x 0.3m) and is capable of speeds from 0.5 to 30 m/s. The time-averaged lift and drag as functions of flapping frequency, forward flight velocity and the orientation angle of the flapping motions with respect to the incoming flows are measured by using a strain gauge balance and KYOWA PCD-300A sensor interface data acquisition system. It has been found that flapping motion would bring significant aerodynamic benefits when the flapping flight is in unsteady state regime, with advance ratio less than 1.0. The aerodynamic benefits are found to decay exponentially with the increasing advance ratio. Flapping motion is found to become detrimental for high speed flight applications. It is also observed that the skin flexibility has considerable effect on the aerodynamic performance. The flexible latex thick wing is found to have better overall aerodynamic performance over the rigid wing, especially for low speed applications. The wood (rigid) wing exhibited better lift production performance in quasi steady regime.

scholarly journals Evolution of the leading-edge vortex over a flapping wing mechanism

2020 ◽  
Vol 14 (2) ◽  
pp. 6888-6894
Author(s):  
Muhamad Ridzuan Arifin ◽  
A.F.M. Yamin ◽  
A.S. Abdullah ◽  
M.F. Zakaryia ◽  
S. Shuib ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Flapping Wing ◽  
Unsteady State ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Advance Ratio ◽  
Lift Enhancement ◽  
Lift And Drag

Leading-edge vortex governs the aerodynamic force production of flapping wing flyers. The primary factor for lift enhancement is the leading-edge vortex (LEV) that allows for stall delay that is associated with unsteady fluid flow and thus generating extra lift during flapping flight. To access the effects of LEV to the aerodynamic performance of flapping wing, the three-dimensional numerical analysis of flow solver (FLUENT) are fully applied to simulate the flow pattern. The time-averaged aerodynamic performance (i.e., lift and drag) based on the effect of the advance ratio to the unsteadiness of the flapping wing will result in the flow regime of the flapping wing to be divided into two-state, unsteady state (J<1) and quasi-steady-state(J>1). To access the benefits of aerodynamic to the flapping wing, both set of parameters of velocities 2m/s to 8m/s at a high flapping frequency of 3 to 9 Hz corresponding to three angles of attacks of α = 0o to α = 30o. The result shows that as the advance ratio increases the generated lift and generated decreases until advance ratio, J =3 then the generated lift and drag does not change with increasing advance ratio. It is also found that the change of lift and drag with changing angle of attack changes with increasing advance ratio. At low advance ratio, the lift increase by 61% and the drag increase by 98% between α =100 and α =200. The lift increase by 28% and drag increase by 68% between α = 200 and α = 300. However, at high advance ratio, the lift increase by 59% and the drag increase by 80% between α =100 and α = 200, while between α =200 and α =300 the lift increase by 20% and drag increase by 64%. This suggest that the lift and drag slope decreases with increasing advance ratio. In this research, the results had shown that in the unsteady state flow, the LEV formation can be indicated during both strokes. The LEV is the main factor to the lift enhancement where it generated the lower suction of negative pressure. For unsteady state, the LEV was formed on the upper surface that increases the lift enhancement during downstroke while LEV was formed on the lower surface of the wing that generated the negative lift enhancement. The LEV seem to breakdown at the as the wing flap toward the ends on both strokes.      

LIFT PERFORMANCE OF A CAMBERED WING FOR AERODYNAMIC PERFORMANCE ENHANCEMENT OF THE FLAPPING WING

2015 ◽  
Vol 75 (8) ◽  
Author(s):  
H. Yusoff ◽  
N. Iswadi ◽  
A.H. Zulkifly ◽  
Sh. Mohd Firdaus ◽  
M.Z. Abdullah ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Performance Enhancement ◽  
Wind Tunnel Test ◽  
Micro Air Vehicles ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Open Circuit ◽  
Flapping Wing ◽  
Flapping Flight ◽  
Advance Ratio

Flapping-Wing Micro Air Vehicles (FW-MAVs) are small hand-held flying vehicles that can maneuver in constrained space owing to its lightweight, low aspect ratio and the ability to fly in low Reynolds number environment. In this study, the aerodynamic characteristics such as time-averaged lift of camber wings with different five wind tunnel test models with 6, 9, 12, and 15 percent camber were developed and the results were compared with time-averaged lift of a flat wing in order to assess the effects of camber wing on the aerodynamic performance for flapping flight applications. The experiments were performed in an open circuit wind tunnel with of non-return airflow with a test section of (0.3 x 0.3) m and capable of speeds from 0.5 to 30 m/s. The time-averaged lift as functions of advance ratio of the flapping motions with respect to the incoming flows are measured by using a strain gauge balance and KYOWA PCD-300A sensor interface data acquisition system. It is found that camber would bring significant aerodynamic benefits when the flapping flight is in unsteady state regime, with advance ratio less than 1.0. The aerodynamic benefits of camber are found to decay exponentially with the increasing advance ratio. Cambered wing shows significantly higher lift in comparison to the flat wing.

Unsteady Flow Analysis Strategies for Flapping Flight

2014 ◽  
Author(s):  
Paul Asbury ◽  
Rachel Nichols ◽  
Greg Gadell ◽  
Mohamed Elsheikh ◽  
Brandon Galbraith ◽  
...  
Keyword(s):  
Steady State ◽  
Cell Volume ◽  
Finite Volume ◽  
Degrees Of Freedom ◽  
Flapping Flight ◽  
Grid Resolution ◽  
Cfd Analysis ◽  
Bird Flight ◽  
Flapping Motion ◽  
Lift And Drag

A current project is underway to create a prototype of an anatomically correct seagull with biologically accurate flight kinematics. The presented work is focused on the computational fluid dynamics (CFD) analysis of bird flight kinematics. A finite volume approach, using Fluent, was used to attempt to model the kinematics of bird flight with varying degrees of freedom to analyze the lift, drag, pressure, and vortices magnitude associated with a range of flight kinematics. Dimensional analysis has been performed to analyze the effects of angle of incidence on the different sections of a seagull wing. Validated CFD analysis has been performed to identify optimal degree of freedom for generating maximum amount of lift while minimizing drag. The analysis benefitted from dynamic meshing and a user defined function to model the seagull wing, profiles of which were approximated by the S1223 airfoil. The user defined function allowed for variation of degrees of freedom to model the flight in the current bird prototype and to assess the effects of changing angles of incidence and inlet velocity on lift and drag. Difficulties were encountered when trying to accurately analyze unsteady aerodynamics over a flapping motion. The appropriate grid resolution, the user defined function, as well as the appropriate grid and dynamic mesh parameters within Fluent were all possible areas of concern. The grid resolution was determined by analyzing a steady state case and determining the variation in lift and drag values calculated by increasing the grid density. A user defined function was created that accurately represents the kinematics associated with the bird wing. A triangular grid was utilized for the dynamic mesh with re-meshing procedure activated at every iteration during the analysis. The final geometry provided an accurate method for dynamic re-meshing and overcame the problem of negative cell volume associated with re-meshing using a rectangular mesh configuration. It was determined that maximum cell volume, number of time steps, and time step interval were all important criteria when determining parameters for the unsteady flight analysis. Results indicate that the unsteady dynamics of bird flapping motion can be effectively represented with modified CFD analysis with updated finite volume scheme. Data indicates that values associated with varying angles of attack at a steady state cannot be used to model flapping flight. The paper will report on further validation to analyze the pressure, lift and drag associated with flapping flight in a three-dimensional study.

Aerodynamic performance of a small-scale tilt rotor: Numerical simulation and experiment in steady state

2020 ◽  
pp. 095440622095035
Author(s):  
Haitao Yang ◽  
Wei Xia ◽  
Kun Wang ◽  
Shuling Hu
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Tilt Angle ◽  
High Speed ◽  
Aerodynamic Performance ◽  
Small Scale ◽  
Thrust Coefficient ◽  
Wind Tunnel Tests ◽  
Advance Ratio

The present work studies the aerodynamic performance of a small-scale rotor in tilting transition states through wind tunnel tests and numerical simulations. Firstly, the test platform for the rotor aerodynamics is built up, and the Computational Fluid Dynamics (CFD) model of flow field around the rotors is established based on the multiple reference frame method. Secondly, the effects of flow velocity, tilt angle and advance ratio on the aerodynamic performance of the rotor are investigated using both the numerical simulation and the wind tunnel test. It is found that for the Model 8038 rotor with maximum effeciency of 0.567 at advance ratio of 0.43, the rotor thrust coefficient increases with the increase of the Reynolds number. At Reynolds number of 410 thousand to 820 thousand, the thrust coefficient increases slightly with the increase of the rotating speed. The results also show that the thrust coefficient decreases with the increase of the advance ratio. With high-speed airflow and relatively low-speed rotation, “windmill” phenomenon is found in the experiment. The tilting of the rotor from level flight to hovering increases the thrust coefficient. Highly dependency of the tilt angle on the thrust coefficients at given advance ratios is found in the wind tunnel tests.

Effect of the strip spacing on the aerodynamic performance of a high-speed double-strip pantograph

2021 ◽  
pp. 1-17
Author(s):  
Zhiyuan Dai ◽  
Tian Li ◽  
Jian Deng ◽  
Ning Zhou ◽  
Weihua Zhang
Keyword(s):  
High Speed ◽  
Aerodynamic Performance

Exploring research on high-speed vehicle attitude control with plasma virtual flap manipulation

2018 ◽  
Vol 233 (10) ◽  
pp. 3627-3634
Author(s):  
Wang Xin ◽  
Yan Jie ◽  
Zhang Yerong
Keyword(s):  
Attitude Control ◽  
High Speed ◽  
Long Duration ◽  
Aerodynamic Control ◽  
Control Authority ◽  
Attitude Controller ◽  
Lift And Drag ◽  
Cruise Flight ◽  
Aerodynamic Lift ◽  
High Speed Vehicle

This work provides an attitude solution for a high-speed vehicle using plasma aerodynamic control called “plasma virtual flap” manipulation. This paper describes the concept of using plasma active control as plasma virtual flap for off-design attitude manipulation problem. Design of an attitude controller considering plasma aerodynamic effects for the high-speed vehicle is presented. The aerodynamic lift and drag force features in the high speed, long duration cruise flight with plasma actuator effect are introduced, where the estimated models and attitude controller are established. This paper documents the development and capabilities of plasma virtual flap attitude control authority. Simulation results are presented to exhibit the effectiveness of the proposed method.

scholarly journals Intermittent Gliding in the Hunting Flight of the Kestrel, Falco Tinnunculus L

1983 ◽  
Vol 102 (1) ◽  
pp. 1-12 ◽  
Author(s):  
J. J. VIDELER ◽  
D. WEIHS ◽  
S. DAAN
Keyword(s):  
Theoretical Model ◽  
Wind Speed ◽  
High Speed ◽  
Flapping Flight ◽  
Falco Tinnunculus ◽  
Fixed Position ◽  
Centre Of Gravity ◽  
High Speed Film

The hunting flight of the kestrel (Falco tinnunculus) consists of short bouts of flight at wind speed against the wind with the eyes in a fixed position relative to the ground, and of short flights from one such position to the next. High speed films taken with a camera in a fixed position of a hunting kestrel of known weight and dimensions, allow estimates to be made of the amount of energy required for this behaviour. A theoretical model shows how a bird could economise by alternating flapping flight with short gliding bouts, without changing the position of the eyes above the ground, by mere displacement of the centre of gravity relative to the head. High speed film data confirm predictions from this model.

scholarly journals Aerodynamic Performance of the NREL S826 Airfoil in Icing Conditions

2017 ◽  
Author(s):  
Julie Krøgenes ◽  
Lovisa Brandrud ◽  
Richard Hann ◽  
Jan Bartl ◽  
Tania Bracchi ◽  
...  
Keyword(s):  
Wind Farm ◽  
Aerodynamic Performance ◽  
Cold Climate ◽  
Navier Stokes ◽  
Computational Results ◽  
Energy Potential ◽  
Pressure Distributions ◽  
Wind Energy Potential ◽  
Experimental Values ◽  
Lift And Drag

Abstract. The demand for wind power is rapidly increasing, creating opportunities for wind farm installations in more challenging climates. Cold climate areas, where ice accretion can be an issue, are often sparsely populated and have high wind energy potential. Icing may lead to severely reduced aerodynamic performance and thereby reduced power output. To reach a greater understanding of how icing affects the aerodynamics of a wind turbine blade, three representative icing cases; rime ice, glaze ice and a mixed ice, were defined and investigated experimentally and computationally. Experiments at Re = 1.0 × 105–4.0 × 105 were conducted in the low-speed wind tunnel at NTNU on a two dimensional wing with applied 3D-printed ice shapes, determining lift, drag and surface pressure distributions. Computational results, obtained from the Reynolds Averaged Navier–Stokes fluid dynamics code FENSAP, complement the experiments. Measured and predicted data show a reduction in lift for all icing cases. Most severe is the mixed ice case, with a lift reduction of up to 30 % in the linear lift area, compared to a clean reference airfoil. Computational results show an under-prediction in maximum lift of 7–18 % compared to experimental values. Curvature and tendencies for both lift and drag show good agreement between simulations and experiment.

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