Aircraft wings are a compromise that allows the aircraft to fly at a range of flight conditions, but the performance at each condition is sub-optimal. The ability of a wing surface to change its geometry during flight has interested researchers and designers over the years as this reduces the design compromises required. Morphing is the short form for metamorphose; however, there is neither an exact definition nor an agreement between the researchers about the type or the extent of the geometrical changes necessary to qualify an aircraft for the title ‘shape morphing.’ Geometrical parameters that can be affected by morphing solutions can be categorized into: planform alteration (span, sweep, and chord), out-of-plane transformation (twist, dihedral/gull, and span-wise bending), and airfoil adjustment (camber and thickness). Changing the wing shape or geometry is not new. Historically, morphing solutions always led to penalties in terms of cost, complexity, or weight, although in certain circumstances, thes...

A Review of Morphing Aircraft

This paper documents the development and evaluation of an original flexible-wing-based Micro Air Vehicle (MAV) technology that reduces adverse effects of gusty wind conditions and unsteady aerodynamics, exhibits desirable flight stability, and enhances structural durability. The flexible wing concept has been demonstrated on aircraft with wingspans ranging from 18 inches to 5 inches. Salient features of the flexible-wing-based MAV, including the vehicle concept, flexible wing design, novel fabrication methods, aerodynamic assessment, and flight data analysis are presented.

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Flexible-wing-based Micro Air Vehicles

4-10 5 . In order to gain better understanding of the fluid physics and associated aerodynamics characteristics, we have coupled (i) a NavierStokes solver, (ii) the e N method transition model, and (iii) a Reynolds-averaged two-equation closure to study the low Reynolds number flow characterized with laminar separation and transition. A new intermittency distribution function suitable for low Reynolds number transitional flow is proposed and tested. To support the MAV applications, we investigate both rigid and flexible airfoils, which has a portion of the upper surface mounted with a flexible membrane, using SD7003 as the configuration. Good agreement is obtained between the prediction and experimental measurements regarding the transition location as well as overall flow structures. In the current transitional flow regime, though the Reynolds number affects the size of the laminar separation bubble, it does not place consistent impact on lift or drag. The gust exerts a major influence on the transition position, resulting in the lift and drag coefficients hysterisis. It is also observed that thrust instead of drag can be generated under certain gust condition. At α=4 o , for a flexible wing, self-excited vibration affects the separation and transition positions; however, the time-averaged lift and drag coefficients are close to those of the rigid airfoil.

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Laminar-Turbulent Transition of a Low Reynolds Number Rigid or Flexible Airfoil

Membrane wing aerodynamics for micro air vehicles

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Flexible-Wing-Based Micro Air Vehicles

Micro aerial vehicles have been the subject of considerable interest and development over the last several years. The majority of current vehicle concepts rely on rigid fixed wings or rotors. An alternate design based on an aeroelastic membrane wing concept has also been developed that has exhibited desired characteristics in flight test demonstrations and competition. This paper presents results from a wind tunnel investigation that sought to quantify stability and control properties for a family of vehicles using the aeroelastic design. The results indicate that the membrane wing does exhibit potential benefits that could be exploited to enhance the design of future flight vehicles.

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Stability and Control Properties of an Aeroelastic Fixed Wing Micro Aerial Vehicle

A series of wind tunnel tests were conducted to investigate the benefits of flexible wings on micro air vehicle aerodynamic performance. Projection Moir Interferometry (PMI) was used to quantify the aero-loaded wing shape for three different wing constructions of varying flexibility. The measurements fully describe the aero-loaded wing shape for a range of tunnel free stream velocity and vehicle angle-of-attack. The deformation measurement accuracy has been shown to be nominally plus or minus 0.25 mm. Generalized comparisons between wings were provided by examining the wing total integrated deformation as a function of simulated flight condition. Using this metric, it was found that a 6-batten, monofilm covered wing deformed approximately 65 percent less than a 2-batten, latex covered wing. A rigid, composite wing tested showed no change in shape throughout the test matrix, proving the aerodynamic performance data collected with this wing can be used as a baseline for comparison with other flexible wing designs. The complete database of wing shape measurements is currently being prepared for input into computational fluid dynamics (CFD) models, enabling accurate modeling of the wing shape at each simulated flight condition tested.

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Projection Moire Interferometry Measurements of Micro Air Vehicle Wings

An experimental investigation of the flow over the rear end of a 0.16 scale notchback automobile configuration has been conducted in the NASA Langley Basic Aerodynamics Research Tunnel (BART). The objective of this work was to investigate the flow separation that occurs behind the backlight and obtain experimental data that can be used to understand the physics and time-averaged structure of the flow field. A three-component laser velocimeter was used to make non-intrusive, velocity measurements in the center plane and in a single cross-flow plane over the decklid. In addition to off-body measurements, flow conditions on the car surface were documented via surface flow visualization, boundary layer measurements, and surface pressures. The experimental data show several features previously identified by other researchers, but also reveal differences between the flow field associated with this particular configuration and the generally accepted models for the flow over a notchback rear end.

N Jenkins Luther

Papers

Stability and Control Properties of an Aeroelastic Fixed Wing Micro Aerial Vehicle

Projection Moire Interferometry Measurements of Micro Air Vehicle Wings

An Experimental Investigation of the Flow Over the Rear End of a Notchback Automobile Configuration