Experimental Investigation on a 3D Wing Section Hosting Multiple SJAs for Stall Control Purpose

Flow control over aerodynamic shapes in order to achieve performance enhancements has been a lively research area for last two decades. Synthetic Jet Actuators (SJAs) are devices able to interact actively with the flow around their hosting structure by providing ejection and suction of fluid from the enclosed cavity containing a piezo-electric oscillating membrane through dedicated orifices. The research presented in this paper concerns the implementation of zero-net-mass-flux SJAs airflow control system on a NACA0015, low aspect ratio wing section prototype. Two arrays with each 10 custom-made SJAs, installed at 10% and 65% of the chord length, make up the actuation system. The sensing system consists of eleven acoustic pressure transducers distributed in the wing upper surface and on the flap, an accelerometer placed in proximity of the wing c.g. and a six-axis force balance for integral load measurement. A dSPACE™ hardware connected to the software environment Matlab/Simulink® and dSPACE Control-Desk® complete the test architecture. Wind tunnel experiments, on the uncontrolled wing (actuators off), are primarily performed for system identification purpose. The open-loop control operation (actuators on but no feedback) of the wing is implemented and tested, obtaining a stall delay of about 2.8 degrees of AOA. Furthermore, a closed-loop strategy, based on the wing upper surface mean pressure chord-wise distributions signature is adopted to characterize the forthcoming boundary layer detachment. This allows for triggering the controller in stall proximity only, for energy saving purpose. Pertinent results and discussion are provided along with concluding remarks and prospects for future research

Particle nucleation in a forested environment

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Aeroelastic Response of Nonlinear Wing Section by Functional Series Technique

This paper addresses the problem of the determination of the subcritical aeroelastic response and flutter instability of nonlinear two-dimensional lifting surfaces in an incompressible flow-field via indicial functions and Volterra series approach. The related aeroelastic governing equations are based upon the inclusion of structural and damping nonlinearities in plunging and pitching, of the linear unsteady aerodynamics and consideration of an arbitrary time-dependent external pressure pulse. Unsteady aeroelastic nonlinear kernels are determined, and based on these, frequency and time histories of the subcritical aeroelastic response are obtained, and in this context the influence of the considered nonlinearities is emphasized. Conclusions and results displaying the implications of the considered effects are supplied

A Reduced Order Model for the Aeroelastic Analysis of Flexible Wings

The aeroelastic design of highly flexible wings, made of extremely light structures yet still capable of carrying a considerable amount of non-structural weights, requires significant effort. The complexity involved in such design demands for simplified mathematical tools based on appropriate reduced order models capable of predicting the accurate aeroelastic behaviour. The model presented in this paper is based on a consistent nonlinear beam model, capable of simulating the unconventional aeroelastic behaviour of flexible composite wings. The partial differential equations describing the wing dynamics are reduced to a dimensionless form in terms of three ordinary differential equations using a discretization technique, along with Galerkin's method. Within this approach the nonlinear structural model an unsteady indicial based aerodynamic model with dynamic stall are coupled. Only three degrees of freedom in edgewise, flapwise, and torsion, are needed to describe efficiently the dynamics of the wing and to evaluate the sensitivity to system parameters, such as stiffness ratio, aspect ratio, and root angle of attack. Interesting design indicators will be highlighted. In addition to analytical results, a wind tunnel test article will be introduced to assess the validity of the proposed model

Post-flutter bifurcation behavior in long-span suspension bridges

A linearized parametric continuum model of a long-span suspension bridge is coupled with a nonlinear quasi-steady aero-dynamic model giving the aeroelastic partial differential equations of motion reduced to the state-space ordinary differential form by adopting the Galerkin method. Numerical time-domain simulations are performed to investigate the limit cycle oscillations occurring in the range of post-flutter wind speeds. Continuation tools are thus employed to path follow the limit cycles past the flutter speed where the Hopf bifurcation occurs. The stable post-flutter behavior, which can significantly affect the bridge by fatigue, terminate at a fold bifurcation. This result represents an important assessment of the conducted aeroelastic investigations. The stability range of the limit cycle oscillations is evaluated by carrying out sensitivity analyses with respect to the main design parameters, such as the structural damping and the initial wind angle of attack. Copyright © 2013 by ASME

A 3D User and Maintenance Manual for UAVs and Commercial Aircrafts Based on Augmented Reality

raditional User/Maintenance Manuals provide useful information when dealing with simple machines. However, when dealing with complex systems of systems and highly miniaturized technologies, like UAVs, or with machines with millions of parts, a commercial aircraft is a case in point, new technologies taking advantage of Augmented Reality can rapidly and effectively support the maintenance operations. This paper presents a User/Maintenance Manual based on Augmented Reality to help the operator in the detection of parts and in the sequence to be followed to assemble/disassemble systems and subsystems. The proposed system includes a handheld device and/or an head mounted display or special goggles, to be used by on-site operators, with software management providing data fusion and overlaying traditional 2D user/maintenance manual information with an augmented reality software and appropriate interface. This device is connected by internet to a maintenance centre located in the aircraft manufacturer facilities. The on-site operator can directly access to multimedia content and historical information and can be helped or guided remotely by expert engineers residing at the manufacturer company offices. This resource may exploit Computer Aided Design and Product Data Management PDM remote facilities to prepare additional and specific 3D graphic content, supported also by a video and audio streaming from the camera and microphone of the on-site operator's handheld device. The proposed solution has revealed a number of significant advantages compared to the currently used operations: there is no need for preparing animations and graphic content for all the required maintenance sequences. The expert engineers and designers can both be involved directly in the maintenance tasks, a useful mean of feedback to evaluate the design for further projects or for project improvement. Additionally, the sensitive data is not shared outside the company since data is transmitted for visual display but it is stored on a secured location

UNSTEADY AERODYNAMIC MODELING AND FLUTTER ANALYSIS OF LONG-SPAN SUSPENSION BRIDGES

A parametric one-dimensional model of suspension bridges is employed to investigate their static and dynamic aeroelastic behavior in response to a gust load and at the onset of flutter. The equilibrium equations are obtained via a direct total Lagrangian formulation where the kinematics for the deck, assumed to be linear, feature the vertical and the chord-wise displacements of the deck mean axis and the torsional rotations of the deck cross sections, while preserving their shape during rotation. The cables elasto-geometric stiffness contribution is obtained by condensing the equilibrium in the longitudinal direction assuming small horizontal displacements and neglecting the cable kinematics along the bridge chord-wise direction. The equations of motion are linearized about the prestressed static aeroelastic configuration and are obtained via an updated Lagrangian formulation. The equations of motion governing the structural dynamics of the bridge are coupled with the incompressible unsteady aerodynamic model obtained by a set of reduced-order indicial functions developed for the cross section of a suspension bridge, here represented by a rectangular cross-section. The space dependence of the governing equations is treated using the Galerkin approach borrowing as set of trial functions, the eigenbasis of the modal space. The time integration is subsequently performed by using a numerical scheme that includes the modal reduced dynamic aeroelastic Ordinary Differential Equations (ODEs) and the added aerodynamic states also represented in ODE form, the latter being associated with the lag-state formulation pertinent to the unsteady wind-induced loads. The model is suitable to analyze the effect of a time and space non uniform gust load distributed on the bridge span. The obtained aeroelastic system is also suitable to study the onset of flutter and to investigate the sensitivity of the flutter condition on geometrical and aerodynamic parameters. The flutter instability is evaluated using appropriate frequency and time domain characteristics. The parametric continuum model is exploited to perform dynamic aeroelastic flutter analysis and gust response of the Runyang Suspension Bridge over the Yangtze river in China

Post-flutter analysis of flexible high-aspect-ratio wings

The nonlinear aeroelastic modeling and post-flutter behavior of HALE wings are discussed. By employing a geometrically exact 3-dimensional structural beam model coupled with the modified Beddoes-Leishman incompressible unsteady aerodynamic model, the study of a reduced-order model obtained by the Galerkin method is carried out. Continuation tools are employed to path follow both the nonlinear static equilibria as well as the limit cycles past the flutter velocity where the Hopf bifurcation occurs. Aeroelastic simulations are concurrently performed by reducing the governing equations to a form amenable to numerical integration in a finite element solution platform. Initial investigations are carried out on the nonlinear HALE wing model coupled with a quasi-steady aerodynamic model. It is highlighted that the number of mode shapes in the reduced-order models for the equilibrium response in the pre-flutter range becomes important for increasing air speeds. The stable post-flutter branches terminate at fold bifurcations, a somewhat expected result which, however, represents an important assessment of the conducted investigations. Further investigations present the effects of the unsteady aerodynamics for moderately large angles of attack described by the modified Beddoes-Leishman incompressible unsteady aerodynamic model that accounts for flow separation and dynamic stall. The ongoing investigations aim to study the aeroelastic behavior of these highly nonlinear wings, for an improved understanding of the nonlinear behavior in the neighborhood of the flutter boundary and in the post-critical regime, and in high angle-of-attack regimes where the unsteady aerodynamic effects due to flow separation and stall are more significant. ©2012 AIAA