Aeroelastic Analysis of Membrane Micro Air Vehicles

2009 ◽  
Author(s):  
Peter J. Attar ◽  
Raymond E. Gordnier ◽  
Jordan W. Johnston ◽  
William A. Romberg ◽  
Ramkumar N. Parthasarathy
Keyword(s):  
Strouhal Number ◽  
Limit Cycle ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Micro Air Vehicles ◽  
Element Model ◽  
Wing Membrane ◽  
Reduced Frequency ◽  
Membrane Wing ◽  
Air Vehicles

The fluid and structural response of two different membrane wing Micro Air Vehicles is studied through computation and experiment. A (three) batten-reinforced fixed wing membrane micro air vehicle is used to determine the effect of membrane prestrain and fixed angle of attack on flutter and limit cycle behavior of fixed wing membrane Micro Air Vehicles. For each configuration tested, flutter and subsequent limit cycle oscillations are measured in wind tunnel tests and predicted using an aeroelastic computational model consisting of a nonlinear finite element model coupled to a vortex lattice solution of the Laplace equation and boundary conditions. Correlation between the predicted and measured onset of limit cycle oscillation is good as is the prediction of the amplitude of the limit cycle at the trailing edge of the lower membrane. A direct correlation between levels of strain and the phase of the membranes during the limit cycle is found in the computation and thought to also occur in the experiment. The second membrane wing micro air vehicle configuration is that of a plunging membrane airfoil model. This model is studied computationally using a sixth-order finite difference solution of the Navier-Stokes equations coupled to a nonlinear string finite element model. The effect, on the structural and fluid response, of plunging Strouhal number, reduced frequency and static angle of attack is examined. At two degree angle of attack, and Strouhal number of 0.2, the effect of increasing the plunging reduced frequency is to decrease the sectional lift coefficient and increase the sectional drag coefficient. At this angle of attack, minimal change in the sectional lift coefficient is found when increasing from a Strouhal number of 0.2 to 0.5 at reduced frequencies of 0.5 and 5.903, the lowest and highest values of this parameter which are studied in this work. For this angle of attack the maximum change which occurs when increasing the Strouhal number from 0.2 to 0.5 is at a reduced frequency of 1.5. When the effect of angle of attack is studied, it is found that at a Strouhal number of 0.5 and reduced frequency of 1.5 the plunging flexible model demonstrates improved lift characteristics over the fixed flexible airfoil case. The greatest improvement occurs at an angle of attack of 2 degrees followed by 10 degrees and then 6 degrees. Finally the effect on the flow characteristics of airfoil flexibility is investigated by increasing the membrane pre-strain from a nominal value of 5 percent to that of 20 percent. This increase in pre-strain results in a reduced value of sectional lift coefficient as compared the 5 percent pre-strain case at the same fixed angle of attack, Strouhal number and reduced frequency.

A Characterization of Limit Cycle Oscillations in Membrane Wing Micro Air Vehicles at Low Angle of Attack

2010 ◽  
Author(s):  
Peter J. Attar ◽  
Jordan W. Johnston ◽  
William A. Romberg ◽  
Ramkumar N. Parthasarathy ◽  
Brian J. Morris
Keyword(s):  
Limit Cycle ◽  
Micro Air Vehicles ◽  
Element Model ◽  
Limit Cycle Oscillation ◽  
Limit Cycle Oscillations ◽  
Wing Membrane ◽  
Membrane Wing ◽  
Cycle Oscillation ◽  
Nonlinear Finite Element Model ◽  
Air Vehicles

In this paper, a (three) batten-reinforced fixed wing membrane micro air vehicle is used to determine the effect of membrane pre-strain on flutter and limit cycle behavior of fixed wing membrane Micro Air Vehicles. For each configuration tested, flutter and subsequent limit cycle oscillations are measured in wind tunnel tests and predicted using an aeroelastic computational model consisting of a nonlinear finite element model coupled to a vortex lattice solution of the Laplace equation and boundary conditions. Agreement between the predicted and measured onset of limit cycle oscillation is good as is the prediction of the amplitude of the limit cycle at the trailing edge of the lower membrane. A direct correlation between levels of strain and the phase of the membranes during the limit cycle is found in the computation and thought to also occur in the experiment.

Experimental Characterization of Limit Cycle Oscillations in Membrane Wing Micro Air Vehicles

2010 ◽  
Vol 47 (4) ◽  
pp. 1300-1308 ◽  
Author(s):  
Jordan W. Johnston ◽  
Will Romberg ◽  
Peter J. Attar ◽  
Ramkumar Parthasarathy
Keyword(s):  
Limit Cycle ◽  
Micro Air Vehicles ◽  
Limit Cycle Oscillations ◽  
Experimental Characterization ◽  
Membrane Wing ◽  
Air Vehicles

An Investigation of the Aerodynamic Performance of a Biomimetic Insect-Sized Wing for Micro Air Vehicles

2016 ◽  
Author(s):  
Jose E. Rubio ◽  
Uttam K. Chakravarty
Keyword(s):  
Reynolds Number ◽  
Structural Integrity ◽  
Angle Of Attack ◽  
Micro Air Vehicles ◽  
Element Model ◽  
Aerodynamic Performance ◽  
Mode Shapes ◽  
Wing Structures ◽  
Artificial Wing ◽  
Air Vehicles

Biologically-inspired micro air vehicles (MAVs) are miniature-scaled autonomous aircrafts which attempt to biomimic the exceptional maneuver control during low-speed flight mastered by insects. Flexible wing structures are critical elements of a nature-inspired MAV as evidence supports that the wings of aerial insects experience highly-elastic deformations that enable insects to proficiently hover and maneuver in different airflow conditions. For this study, a crane fly (family Tipulidae) forewing is selected as the target specimen to replicate both its structural integrity and aerodynamic performance. The artificial insect-sized wing is manufactured using photolithography with negative photoresist SU-8 to fabricate the vein geometry. A Kapton film is attached to the vein pattern for the assembling of the wing. The natural frequencies and mode shapes of the artificial wing are determined to characterize its vibrations. A numerical simulation of the fluid-structure interaction is conducted by coupling a finite element model of the artificial wing with a computational fluid dynamics model of the surrounding airflow. From these simulations, the deformation response and the coefficients of drag and lift of the artificial wing are predicted for different freestream velocities and angles of attack. The deformation along the span of the wing increases nonlinearly with Reynolds number from the root to the tip of the wing. The coefficient of lift increases with angle of attack and Reynolds number. The coefficient of drag decreases with Reynolds number and angle of attack. The aerodynamic efficiency, defined as the ratio of the coefficient of lift to the coefficient of drag, of the artificial wing increases with angle of attack and Reynolds number.

Aeroelastic Analysis of Membrane Microair Vehicles—Part I: Flutter and Limit Cycle Analysis for Fixed-Wing Configurations

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Peter J. Attar ◽  
Raymond E. Gordnier ◽  
Jordan W. Johnston ◽  
William A. Romberg ◽  
Ramkumar N. Parthasarathy
Keyword(s):  
Limit Cycle ◽  
Element Model ◽  
Limit Cycle Oscillation ◽  
Wing Membrane ◽  
Structural Dynamic ◽  
Aeroelastic Analysis ◽  
Structural Dynamic Characteristics ◽  
Membrane Wing ◽  
Cycle Oscillation ◽  
Nonlinear Finite Element Model

This is the first of two papers concerning the fluid and structural dynamic characteristics of membrane wing microair vehicles. In this paper, a (three) batten-reinforced fixed-wing membrane microair vehicle is used to determine the effect of membrane prestrain on flutter and limit cycle behavior of fixed-wing membrane microair vehicles. For each configuration tested, flutter and subsequent limit cycle oscillations are measured in wind tunnel tests and predicted using an aeroelastic computational model consisting of a nonlinear finite element model coupled to a vortex lattice solution of the Laplace equation and boundary conditions. Agreement between the predicted and measured onset of limit cycle oscillation is good as is the prediction of the amplitude of the limit cycle at the trailing edge of the lower membrane. A direct correlation between levels of strain and the phase of the membranes during the limit cycle is found in the computation and thought to also occur in the experiment.

Aeroelastic Analysis of Membrane Microair Vehicles—Part II: Computational Study of a Plunging Membrane Airfoil

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Peter J. Attar ◽  
Raymond E. Gordnier ◽  
Jordan W. Johnston ◽  
William A. Romberg ◽  
Ramkumar N. Parthasarathy
Keyword(s):  
Strouhal Number ◽  
Stokes Equations ◽  
Computational Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Reduced Frequency ◽  
Lift And Drag ◽  
Intermediate Value

In the second paper of the two part study of membrane microair vehicles, computations are performed for a plunging membrane airfoil. The computational model uses a sixth-order finite difference solution of the Navier–Stokes equations coupled to a finite element solution of a set of nonlinear string equations. The effect, on the structural and fluid response, of plunging Strouhal number, reduced frequency, and static angle of attack is examined. Qualitatively, the flow field is found to be very complex with interactions of vortices shed from various locations along the chord of the airfoil. At a low angle of attack and a low Strouhal number, increasing reduced frequency results in a decrease and an increase in the mean sectional lift and drag coefficients, respectively. Also, at a low angle of attack, increasing the Strouhal number has minimal effect at high and low values of reduced frequencies, but a significant effect is found at an intermediate value of reduced frequency. When the effect of angle of attack is studied for fixed values of Strouhal number and reduced frequency, it is found that the act of plunging gives improved mean sectional lift when compared with the case of a fixed flexible airfoil. The improvement does not increase monotonically with the angle of attack but instead is maximum at an intermediate value. Finally, increasing the value of the membrane prestrain, which stiffens the airfoil, results in a reduced value of the sectional lift coefficient for a given Strouhal number, reduced frequency, and angle of attack.

Evolutionary shape optimisation enhances the lift coefficient of rotating wing geometries

2019 ◽  
Vol 868 ◽  
pp. 369-384 ◽  
Author(s):  
Shantanu S. Bhat ◽  
Jisheng Zhao ◽  
John Sheridan ◽  
Kerry Hourigan ◽  
Mark C. Thompson
Keyword(s):  
Reynolds Number ◽  
Lift Coefficient ◽  
Micro Air Vehicles ◽  
Aerodynamic Performance ◽  
Wing Shape ◽  
Shape Optimisation ◽  
Large Area ◽  
Aerodynamic Pressure ◽  
Performance Requirements ◽  
Air Vehicles

Wing shape is an important factor affecting the aerodynamic performance of wings of monocopters and flapping-wing micro air vehicles. Here, an evolutionary structural optimisation method is adapted to optimise wing shape to enhance the lift force due to aerodynamic pressure on the wing surfaces. The pressure distribution is observed to vary with the span-based Reynolds number over a range covering most insects and samaras. Accordingly, the optimised wing shapes derived using this evolutionary approach are shown to adjust with Reynolds number. Moreover, these optimised shapes exhibit significantly higher lift coefficients (${\sim}50\,\%$) than the initial rectangular wing forebear. Interestingly, the optimised shapes are found to have a large area outboard, broadly in line with the features of high-lift forewings of multi-winged insects. According to specific aerodynamic performance requirements, this novel method could be employed in the optimisation of improved wing shapes for micro air vehicles.

Membrane wing aerodynamics for micro air vehicles

2003 ◽  
Vol 39 (6-7) ◽  
pp. 425-465 ◽  
Author(s):  
Yongsheng Lian ◽  
Wei Shyy ◽  
Dragos Viieru ◽  
Baoning Zhang
Keyword(s):  
Micro Air Vehicles ◽  
Membrane Wing ◽  
Wing Aerodynamics ◽  
Air Vehicles

scholarly journals Improving the aerodynamic performance of a cycloidal rotor through active compliant morphing

2017 ◽  
Vol 121 (1241) ◽  
pp. 901-915
Author(s):  
L. Ferrier ◽  
M. Vezza ◽  
H. Zare-Behtash
Keyword(s):  
Negative Impact ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Aerodynamic Performance ◽  
Dynamic Stall ◽  
Marine Vehicles ◽  
Aerospace Applications ◽  
Naca 0015 ◽  
Air Vehicles

ABSTRACTCycloidal rotors are a novel form of propulsion system that can be adapted to various forms of transport such as air and marine vehicles, with a geometrical design differing significantly from the conventional screw propeller. Research on cycloidal rotor design began in the early 1930s and has developed throughout the years to the point where such devices now operate as propulsion systems for various aerospace applications such as micro air vehicles, unmanned air vehicles and compound helicopters. The majority of research conducted on the cycloidal rotor’s aerodynamic performance have not assessed mitigating the dynamic stall effect, which can have a negative impact on the rotor performance when the blades operate in the rotor retreating side. A solution has been proposed to mitigate the dynamic stall effect through employment of active, compliant leading-edge morphing. A review of the current state of the art in this area is presented. A two-dimensional, implicit unsteady numerical analysis was conducted using the commercial computational fluid dynamics software package STAR CCM+, on a two-bladed cycloidal rotor. An overset mesh technique, otherwise known as a chimera mesh, was used to apply complex transient motions to the simulations. Active, compliant leading-edge morphing is applied to an oscillating NACA 0015 aerofoil to attempt to mitigate the dynamic stall whilst maintaining the positive dynamic lift coefficient (Cl) contributions. It was verified that by applying a pulsed input leading-edge rotational morphing schedule, the leading-edge vortex does not fully form and the large flow separation is prevented. Further work in this investigation will focus on coupling the active, leading-edge motion to the cycloidal rotor model with the aim to maximise aerodynamic performance.

Impact of Flexibility on the Aerodynamics of an Aspect Ratio Two Membrane Wing

2012 ◽  
Author(s):  
Raymond E. Gordnier ◽  
Peter J. Attar
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Micro Air Vehicles ◽  
Navier Stokes ◽  
Elastic Membrane ◽  
Pitching Moment ◽  
Flexible Membrane ◽  
Membrane Wing ◽  
The Impact ◽  
Air Vehicles

Development of an aeroelastic solver with application to flexible membrane wings for micro air vehicles is presented. A high-order (up to 6th order) Navier-Stokes solver is coupled with a geometrically nonlinear p-version Reissner-Mindlin finite element plate model to simulate the highly flexible elastic membrane. An implicit LES approach is employed to compute the mixed laminar/transitional/turbulent flowfields present for the low Reynolds number flows associated with micro air vehicles. Computations are performed for an aspect ratio two membrane wing at angles of attack α = 10°, 16° and 23° for a Reynolds number, Re = 24,300. Comparisons of the computational results with experimental PIV and surface deflection measurements demonstrated reasonable agreement. Reduced separation and enhanced lift are obtained due to favorable interactions between the flexible membrane wing and the unsteady flow over the wing. The impact of flexibility on the aerodynamic performance comes primarily from the development of mean camber with some further effects arising from the interaction between the dynamic motion of the membrane and the unsteady flowfield above. At lower angles of attack this lift enhancement comes at the cost of reduced L/D. The nose-down pitching moment increases with flexibility at the lowest angle of attack but is reduced for the higher two angles of attack. These results suggest that membrane flexibility might provide a means to reduce the impact of strong gust encounter by maintaining lift and reducing the effect of the gust on pitching moment.

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