Implicit LES Simulations for an Aspect Ratio Two Flexible Membrane Wing

Air Vehicle ◽

Membrane Wing ◽

Reynolds Number Flows

Development of an aeroelastic solver with application to flexible membrane wings for micro air vehicle applications 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. Intitial computations for a baseline rigid membrane wing are presented to understand the complex vortex dynamics associated with these flows before proceeding with the more challenging flexible cases.

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

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2012-72296 ◽

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 ◽

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.

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

Effect of Small-Amplitude Heaving Oscillations on the Flow Structure Above a Low-Aspect Ratio Wing

10.1115/ajk2011-02011 ◽

2011 ◽

Cited By ~ 2

Author(s):

Miguel R. Visbal

Keyword(s):

Micro Air Vehicles ◽

Dynamic Stall ◽

Flapping Wings ◽

Flight Performance ◽

Effective Angle ◽

And Performance ◽

Aerodynamic Surfaces ◽

Reynolds Number Flows ◽

Unsteady low-Reynolds-number flows are of importance in understanding the flight performance of natural flyers, as well as in the design of small unmanned air vehicles and micro air vehicles [1,2]. The imposed motion of flapping wings or the large excursions in effective angle of attack during gust encounters may induce the formation of dynamic-stall-like vortices [3–10] whose evolution and interaction with the aerodynamic surfaces impact both flight stability and performance.

Computational and experimental investigations of low-Reynolds-number flows past an aerofoil

The Aeronautical Journal ◽

10.1017/s000192400000172x ◽

2007 ◽

Vol 111 (1115) ◽

pp. 17-29 ◽

Cited By ~ 26

Author(s):

W. Yuan ◽

M. Khalid ◽

J. Windte ◽

U. Scholz ◽

R. Radespiel

Keyword(s):

Reynolds Number ◽

Separation Bubble ◽

Low Reynolds Number ◽

Turbulence Models ◽

Navier Stokes ◽

Experimental Investigations ◽

Eddy Simulation ◽

Low Reynolds ◽

Reynolds Number Flows

AbstractThis paper presents investigations of low-Reynolds-number flows past an SD7003 aerofoil at Re = 60k, where transition takes place across a laminar separation bubble (LSB). Results of experimental measurements and numerical calculations are analysed and discussed. In particular, reasonably good results were obtained using two different numerical approaches: Large-eddy simulation (LES) that demonstrated vortical structures at different transition stages, and where the transition occurred naturally; unsteady Reynolds-averaged Navier-Stokes (URANS) simulations for several turbulence models based on the ω-length-scale equation, coupled to a linear stability solver to predict the transition position.

Volume 1A, Symposia: Advances in Fluids Engineering Education; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Applications in CFD; Bio-Inspired Fluid Mechanics; CFD Verification and Validation; Development and Applications of Immersed Boundary Methods; DNS, LES, and Hybrid RANS/LES Methods ◽

Implicit LES Simulations of a Flapping Wing in Forward Flight

10.1115/fedsm2013-16540 ◽

2013 ◽

Cited By ~ 5

Author(s):

Raymond E. Gordnier ◽

Luciano Demasi

Keyword(s):

Reynolds Number ◽

Angle Of Attack ◽

Micro Air Vehicles ◽

Navier Stokes ◽

Forward Flight ◽

Freestream Velocity ◽

Flapping Motion ◽

Wing Motion ◽

Aerodynamic Angle

Computations of an aspect ratio 3.5 flat plate wing in flapping forward flight are performed. A high-order 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. The ILES approach is implemented by exploiting the properties of a well validated, robust, sixth-order Navier-Stokes solver. The analyzed kinematics are a flapping motion described by an anti-clockwise 8 cycle. A Reynolds number based on the freestream velocity of 1250 is prescribed. A detailed description of the dynamic vortex system engendered by the unsteady flapping motion is given and related to the development of lift and thrust during the flapping cycle. Effective angle of attack, which results from the wing motion, and its interplay with the aerodynamic angle of attack play a key role in determining the flow structure and forces produced.

Modal Analysis of a Flexible Membrane Wing of Micro Air Vehicles

Journal of Aircraft ◽

10.2514/1.c031393 ◽

2011 ◽

Vol 48 (6) ◽

pp. 1960-1967 ◽

Cited By ~ 11

Author(s):

Uttam Kumar Chakravarty ◽

Roberto Albertani

Keyword(s):

Modal Analysis ◽

Micro Air Vehicles ◽

Flexible Membrane ◽

Membrane Wing ◽

Vortex flows on UAVs: Issues and challenges

The Aeronautical Journal ◽

10.1017/s0001924000000439 ◽

2004 ◽

Vol 108 (1090) ◽

pp. 597-610 ◽

Cited By ~ 38

Author(s):

I. Gursul

Keyword(s):

Vortex Breakdown ◽

Unsteady Aerodynamics ◽

Micro Air Vehicles ◽

Vortical Flow ◽

Vortical Flows ◽

Vortex Interactions ◽

Wing Stall ◽

Reynolds Number Flows ◽

Abstract Separated and vortical flows are dominant over various unmanned air vehicles (UAVs). In this article, issues and challenges of vortical flows for future UAVs are reviewed. These include shear layer instabilities, vortex breakdown and wing stall, vortex interactions, nonslender vortices, multiple vortices, and manoeuvring wing vortices. There are also issues relating to vortical flows in certain flow/structure interactions, as well as in aerodynamics/propulsion interactions. Separated and vortical flows are even more dominant at low Reynolds number flows. The main features of vortical flows, unsteady aerodynamics, and propulsion related vortical flow isssues relevant to mini- and micro air vehicles, are discussed.