scholarly journals Development of a morphing wingtip based on compliant structures

2018 ◽  
Vol 29 (16) ◽  
pp. 3293-3304 ◽  
Author(s):  
Chen Wang ◽  
Hamed Haddad Khodaparast ◽  
Michael I Friswell ◽  
Alexander D Shaw ◽  
Yuying Xia ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Dihedral Angle ◽  
Honeycomb Structure ◽  
Equivalent Model ◽  
Morphing Aircraft ◽  
Aerodynamic Loads ◽  
Compliant Structure ◽  
Trailing Edges ◽  
Morphing Structure ◽  
Structural Solutions

Compliant structures, such as flexible corrugated panels and honeycomb structures, are promising structural solutions for morphing aircraft. The compliant structure can be tailored to carry aerodynamic loads and achieve the geometry change simultaneously, while the reliability of the morphing aircraft can be guaranteed if conventional components and materials are used in the fabrication of the morphing structure. In this article, a compliant structure is proposed to change the dihedral angle of a morphing wingtip. Unsymmetrical stiffness is introduced in the compliant structure to induce the rotation of the structure. Trapezoidal corrugated panels are used, whose geometry parameters can be tailored to provide the stiffness asymmetry. An equivalent model of the corrugated panel is employed to calculate the deformation of the compliant structure. To provide the airfoil shape, a flexible honeycomb structure is used in the leading and trailing edges. An optimisation is performed to determine the geometry variables, while also considering the actuator requirements and the available space to instal the compliant structure. An experimental prototype has been manufactured to demonstrate the deformation of the morphing wingtip and conduct basic wind tunnel tests.

scholarly journals Compliant structures based on stiffness asymmetry

2018 ◽  
Vol 122 (1249) ◽  
pp. 442-461 ◽  
Author(s):  
C. Wang ◽  
H. H. Khodaparast ◽  
M. I. Friswell ◽  
A. D. Shaw
Keyword(s):  
Experimental Tests ◽  
Equivalent Model ◽  
Finite Element Models ◽  
Morphing Aircraft ◽  
Actuation Force ◽  
Compliant Structure ◽  
Morphing Structure ◽  
Wing Tip ◽  
Multiple Units

ABSTRACTOne of the key problems in the development of morphing aircraft is the morphing structure, which should be able to carry loads and change its geometry simultaneously. This paper investigates a compliant structure, which has the potential to change the dihedral angle of morphing wing-tip devices. The compliant structure is able to induce deformation by unsymmetrical stiffness allocation and carry aerodynamic loads if the total stiffness of the structure is sufficient.The concept has been introduced by building a simplified model of the structure and deriving the analytical equations. However, a properly designed stiffness asymmetry, which is optimised, can help to achieve the same deformation with a reduced actuation force.In this paper, round corrugated panels are used in the compliant structure and the stiffness asymmetry is introduced by changing the geometry of the corrugation panel. A new equivalent model of the round corrugated panel is developed, which takes the axial and bending coupling of the corrugated panel into account. The stiffness matrix of the corrugated panel is obtained using the equivalent model, and then the deflections of the compliant structure can be calculated. The results are compared to those from detailed finite element models built in the commercial software Abaqus. Samples with different geometries were manufactured for experimental tests.After verifying the equivalent model, optimisation is performed to find the optimum geometries of the compliant structures. The actuation force of a single compliant structure is first optimised, and then the optimisation is performed for a compliant structure consisting of multiple units. A case study is used to show the performance improvement obtained.

scholarly journals Influence of Embankments With Parapets on the Cross-Wind Turbulence Intensity at the Contact Wire of Railway Overheads

2010 ◽  
Author(s):  
Sergio Avila-Sanchez ◽  
Oscar Lopez-Garcia ◽  
Jose Meseguer
Keyword(s):  
Wind Tunnel ◽  
Environmental Factor ◽  
Turbulence Intensity ◽  
Experimental Analysis ◽  
System Operation ◽  
Contact Wire ◽  
Aerodynamic Loads ◽  
Essential Parameter ◽  
Railway System ◽  
Undamped Oscillations

Winds as an environmental factor can cause significant difficulties for the railway system operation. The railway overhead has been particularly vulnerable to cross-winds related problems, such as development of undamped oscillations due to galloping phenomenon. The installation of windbreaks to decrease the aerodynamic loads on the train can affect the loads on railway overheads triggering cable galloping. One essential parameter to indicate the influence of the parapet wake on the catenary contact wire is the turbulence intensity. In this paper the results of an experimental analysis of the turbulence intensity due to the presence of parapets carried out in a wind tunnel are reported. Embankments equipped with different parapets have been tested and turbulence intensity has been measured at both contact wire locations, windward and leeward. The relative influence of the parapets is measured through a reduced turbulence intensity, defined as the ratio between the turbulence intensity measured with parapet and the turbulence intensity in the case without any parapet on the embankment. In general the reduced turbulence intensity increases as the height of the parapet increases.

scholarly journals Bidirectional Spiral Pulley Negative Stiffness Mechanism for Passive Energy Balancing

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Jiaying Zhang ◽  
Alexander D. Shaw ◽  
Mohammadreza Amoozgar ◽  
Michael I. Friswell ◽  
Benjamin K. S. Woods
Keyword(s):  
Energy Conversion ◽  
Conversion Efficiency ◽  
Energy Conversion Efficiency ◽  
Negative Stiffness ◽  
Energy Balancing ◽  
Morphing Aircraft ◽  
Spring Force ◽  
Morphing Structure ◽  
Negative Stiffness Mechanism ◽  
Analytical Result

The energy balancing concept seeks to reduce actuation requirements for a morphing structure by strategically locating negative stiffness devices to tailor the required deployment forces and moments. One such device is the spiral pulley negative stiffness mechanism. This uses a cable connected with a pre-tension spring to convert the decreasing spring force into the increasing balanced torque. The kinematics of the spiral pulley is first developed for bidirectional actuation, and its geometry is then optimized by employing an energy conversion efficiency function. The performance of the optimized bidirectional spiral pulley is then evaluated through the net torque, the total required energy, and energy conversion efficiency. Then, an additional test rig tests the bidirectional negative stiffness property and compares the characteristics with the corresponding analytical result. Exploiting the negative stiffness mechanism is of significant interest not only in the field of morphing aircraft but also in many other energy and power reduction applications.

Passive Morphing Airfoil With Honeycombs

2011 ◽  
Author(s):  
Hyeonu Heo ◽  
Jaehyung Ju ◽  
Doo-Man Kim ◽  
Chang-Soo Jeon
Keyword(s):  
Shape Change ◽  
Fuel Efficiency ◽  
Aerodynamic Characteristics ◽  
Structural Performance ◽  
Element Analysis ◽  
Structural Shape ◽  
Aerodynamic Loads ◽  
Structure Interaction ◽  
Morphing Structure ◽  
Passive Morphing

A passive morphing may improve the aerodynamic characteristics through structural shape change by aerodynamic loads during the flight, resulting in improving fuel efficiency. The passive morphing structure should have a capability to be highly deformed while maintaining a sufficient stiffness in bending. Honeycombs may be good for controlling both stiffness and flexibility. This paper investigates a honeycomb airfoil’s static deformations through the fluid-structure interaction using computational fluid dynamics and structural finite element analysis. The structural performance will be investigated with varying honeycomb geometries including regular, auxetic and chiral meso-structures.

Some Aerodynamic Aspects of Safety in Road Vehicles: First Paper: Aerodynamic Lift Characteristics of Cars

1973 ◽  
Vol 187 (1) ◽  
pp. 333-347
Author(s):  
G. W. Carr
Keyword(s):  
Wind Tunnel ◽  
Variable Geometry ◽  
Road Vehicles ◽  
Wind Tunnel Tests ◽  
Ground Clearance ◽  
Car Model ◽  
Trailing Edges ◽  
Principal Factors ◽  
Basic Parameters ◽  
Aerodynamic Lift

The principal factors determining the aerodynamic lift of cars are identified from the results of an extensive series of wind-tunnel tests involving simple models of bluff and streamlined form and a variable-geometry saloon-car model. The influence is examined of basic parameters such as camber, incidence, thickness, ground clearance, and underbody roughness. An indication is also given of the extent to which the lift is modified by the squaring of individual edges, particularly the horizontal leading and trailing edges; and the effectiveness of devices fitted under the nose of a car to reduce lift is discussed.

scholarly journals Wind Tunnel Analysis of the Aerodynamic Loads on Rolling Stock over Railway Embankments: The Effect of Shelter Windbreaks

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Sergio Avila-Sanchez ◽  
Santiago Pindado ◽  
Oscar Lopez-Garcia ◽  
Angel Sanz-Andres
Keyword(s):  
Wind Tunnel ◽  
High Speed ◽  
Flow Characteristic ◽  
Rolling Stock ◽  
High Speed Train ◽  
Aerodynamic Loads ◽  
Common Solution ◽  
Small Height ◽  
Tunnel Analysis ◽  
Sheltering Effect

Wind-flow pattern over embankments involves an overexposure of the rolling stock travelling on them to wind loads. Windbreaks are a common solution for changing the flow characteristic in order to decrease unwanted effects induced by the presence of cross-wind. The shelter effectiveness of a set of windbreaks placed over a railway twin-track embankment is experimentally analysed. A set of two-dimensional wind tunnel tests are undertaken and results corresponding to pressure tap measurements over a section of a typical high-speed train are herein presented. The results indicate that even small-height windbreaks provide sheltering effects to the vehicles. Also, eaves located at the windbreak tips seem to improve their sheltering effect.

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