Journal articles: 'Active aerodynamics'

1

Kurec, Krzysztof, Michał Remer, Jakub Broniszewski, Przemysław Bibik, Sylwester Tudruj, and Janusz Piechna. "Advanced Modeling and Simulation of Vehicle Active Aerodynamic Safety." Journal of Advanced Transportation 2019 (February 3, 2019): 1–17. http://dx.doi.org/10.1155/2019/7308590.

Full text

Abstract:

The aim of this study was to extend the safety limits of fast moving cars by the application, in a controlled way, of aerodynamic forces which increase as the square of a car’s velocity and, if left uncontrolled, dramatically reduce car safety. This paper presents the methods, assumptions, and results of numerical and experimental investigations by modeling and simulation of the aerodynamic characteristics and dynamics of a small sports car equipped with movable aerodynamic elements operated by an electronic subsystem for data acquisition and aerodynamics active automatic control.

APA, Harvard, Vancouver, ISO, and other styles

2

Žilinský, Juraj, and Milan Vanc. "Applied Aerodynamics in Building." Advanced Materials Research 855 (December 2013): 164–67. http://dx.doi.org/10.4028/www.scientific.net/amr.855.164.

Full text

Abstract:

Development of new materials, high strength concrete, steels, composites, new construction techniques and procedures put the Development of new materials, high strength concrete, steels, composites, new construction techniques and procedures put the foundations of a new generation of buildings. With the advent of advanced computer technology, using the finite element method engineers and architects plan and construct buildings that are, high, flexible, thin and lightweight. These buildings, however, are burdened by aerodynamic forces, whose source is wind. Just the action of aerodynamic forces adversely affects their ability to traffic, reducing safety and durability. It is therefore necessary to provide high flexibility structures and maintain their safety. This can only be achieved by means of applied aerodynamics using various types of passive and active components to optimize aerodynamics of buildings.

APA, Harvard, Vancouver, ISO, and other styles

3

Jung, Frank. ""All vehicles can benefit from active aerodynamics"." ATZ worldwide 123, no. 4 (March 26, 2021): 22–25. http://dx.doi.org/10.1007/s38311-021-0647-0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Althoff, Matthias, Mayuresh J. Patil, and Johannes P. Traugott. "Nonlinear Modeling and Control Design of Active Helicopter Blades." Journal of the American Helicopter Society 57, no. 1 (January 1, 2012): 1–11. http://dx.doi.org/10.4050/jahs.57.012002.

Full text

Abstract:

This paper presents the theoretical basis for the simulation and control of active helicopter blades. The analysis is based on a model that considers the structural dynamics, the aerodynamics, as well as the integrated blade actuation and sensing. The effect of the integral actuation enters the beam model via an active beam cross-sectional analysis. A two-dimensional incompressible, inviscid, quasi-steady aerodynamic model is coupled to the active structural model. For simulation, analysis, and control design, the blade model is discretized in space using a Galerkin approach. The resulting nonlinear model of high order is reduced using the aeroelastic modes of the blade. Finally, the usefulness of a reduced-order model is demonstrated by designing an energy optimal linear-quadratic-Gaussian (LQG) control.

APA, Harvard, Vancouver, ISO, and other styles

5

NIE, RUI, JINHAO QIU, HONGLI JI, and DAWEI LI. "AERODYNAMIC CHARACTERISTIC OF THE ACTIVE COMPLIANT TRAILING EDGE CONCEPT." International Journal of Modern Physics: Conference Series 42 (January 2016): 1660173. http://dx.doi.org/10.1142/s2010194516601733.

Full text

Abstract:

This paper introduces a novel Morphing Wing structure known as the Active Compliant Trailing Edge (ACTE). ACTE structures are designed using the concept of “distributed compliance” and wing skins of ACTE are fabricated from high-strength fiberglass composites laminates. Through the relative sliding between upper and lower wing skins which are connected by a linear guide pairs, the wing is able to achieve a large continuous deformation. In order to present an investigation about aerodynamics and noise characteristics of ACTE, a series of 2D airfoil analyses are established. The aerodynamic characteristics between ACTE and conventional deflection airfoil are analyzed and compared, and the impacts of different ACTE structure design parameters on aerodynamic characteristics are discussed. The airfoils mentioned above include two types (NACA0012 and NACA64A005.92). The computing results demonstrate that: compared with the conventional plane flap airfoil, the morphing wing using ACTE structures has the capability to improve aerodynamic characteristic and flow separation characteristic. In order to study the noise level of ACTE, flow field analysis using LES model is done to provide noise source data, and then the FW-H method is used to get the far field noise levels. The simulation results show that: compared with the conventional flap/aileron airfoil, the ACTE configuration is better to suppress the flow separation and lower the overall sound pressure level.

APA, Harvard, Vancouver, ISO, and other styles

6

Czyż, Zbigniew, and Mirosław Wendeker. "Measurements of Aerodynamic Interference of a Hybrid Aircraft with Multirotor Propulsion." Sensors 20, no. 12 (June 13, 2020): 3360. http://dx.doi.org/10.3390/s20123360.

Full text

Abstract:

This article deals with the phenomenon of aerodynamic interference occurring in the innovative hybrid system of multirotor aircraft propulsion. The approach to aerodynamics requires a determination of the impact of active sources of lift and thrust upon the aircraft aerodynamic characteristics. The hybrid propulsion unit, composed of a conventional multirotor source of thrust as well as lift in the form of the main rotor and a pusher, was equipped with an additional propeller drive unit. The tests were conducted in a continuous-flow low speed wind tunnel with an open measuring space, 1.5 m in diameter and 2.0 m long. Force testing made it possible to develop aerodynamic characteristics as well as defining aerodynamic characteristics and defining the field of speed for the considered design configurations. Our investigations enabled us to analyze the results in terms of a mutual impact of particular components of the research object and the area of impact of active elements present in a common flow.

APA, Harvard, Vancouver, ISO, and other styles

7

Qin, N., Y. Zhu, and S. T. Shaw. "Numerical study of active shock control for transonic aerodynamics." International Journal of Numerical Methods for Heat & Fluid Flow 14, no. 4 (June 2004): 444–66. http://dx.doi.org/10.1108/09615530410532240.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Dowell, Earl H., Kenneth C. Hall, and Michael C. Romanowski. "Eigenmode Analysis in Unsteady Aerodynamics: Reduced Order Models." Applied Mechanics Reviews 50, no. 6 (June 1, 1997): 371–86. http://dx.doi.org/10.1115/1.3101718.

Full text

Abstract:

In this article, we review the status of reduced order modeling of unsteady aerodynamic systems. Reduced order modeling is a conceptually novel and computationally efficient technique for computing unsteady flow about isolated airfoils, wings, and turbomachinery cascades. Starting with either a time domain or frequency domain computational fluid dynamics (CFD) analysis of unsteady aerodynamic or aeroacoustic flows, a large, sparse eigenvalue problem is solved using the Lanczos algorithm. Then, using just a few of the resulting eigenmodes, a Reduced Order Model of the unsteady flow is constructed. With this model, one can rapidly and accurately predict the unsteady aerodynamic response of the system over a wide range of reduced frequencies. Moreover, the eigenmode information provides important insights into the physics of unsteady flows. Finally, the method is particularly well suited for use in the active control of aeroelastic and aeroacoustic phenomena as well as in standard aeroelastic analysis for flutter or gust response. Numerical results presented include: 1) comparison of the reduced order model to classical unsteady incompressible aerodynamic theory, 2) reduced order calculations of compressible unsteady aerodynamics based on the full potential equation, 3) reduced order calculations of unsteady flow about an isolated airfoil based on the Euler equations, and 4) reduced order calculations of unsteady viscous flows associated with cascade stall flutter, 5) flutter analysis using the Reduced Order Model. This review article includes 25 references.

APA, Harvard, Vancouver, ISO, and other styles

9

Bieler, Heribert. "Active flow control concepts and application opportunities." Aircraft Engineering and Aerospace Technology 89, no. 5 (September 4, 2017): 725–29. http://dx.doi.org/10.1108/aeat-01-2017-0015.

Full text

Abstract:

Purpose Aerodynamics drives the aircraft performance and, thus, influences fuel consumption and environmental compatibility. Further, optimization of aerodynamic shapes is an ongoing design activity in industrial offices; this will lead to incremental improvements. More significant step changes in performance are not expected from pure passive shape design. However, active flow control is a key technology, which has the potential to realize a drastic step change in performance. Flow control targets two major goals: low speed performance enhancements mainly for start and landing phase via control of separation and drag reduction at high speed conditions via skin friction and shock wave control. Design/methodology/approach This paper highlights flow control concepts and Airbus involvements for both items. To mature flow control systematically, local applications of separation control technology are of major importance for Airbus. In parallel, but at lower maturity level, investigations are ongoing to reduce the turbulent skin friction at cruise. A popular concept to delay separation at low speed conditions is the implementation of jet actuation control systems flush mounted to the wall of aerodynamic components. Findings In 2006, DLR (in collaboration with universities Berlin, Braunschweig and industrial partner Airbus) started to study active flow control for separation delay towards application. Based on basic proof of concepts (achieved in national projects), further flow control hardware developments and wind tunnel and lab testing took place in European funded projects. Originality/value Significant lift enhancements were realized via flow control applied to the wing leading edge and the flap.

APA, Harvard, Vancouver, ISO, and other styles

10

Psiaki, Mark L. "Nanosatellite Attitude Stabilization Using Passive Aerodynamics and Active Magnetic Torquing." Journal of Guidance, Control, and Dynamics 27, no. 3 (May 2004): 347–55. http://dx.doi.org/10.2514/1.1993.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Stoica, Adrian Mihail, Marius Stoia-Djeska, and Gabriela Stroe. "Stability Analysis of an Aeroelastic System with Actuator Saturation." Advanced Materials Research 463-464 (February 2012): 1527–32. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.1527.

Full text

Abstract:

Aeroelastic problems of light weight structures of modern aerospace vehicles are the result of interactions between aerodynamics, structural and inertial forces. The mathematical model of the aeroelastic problem is based on the Lagrange equations of motion for the structural dynamics and on a quasi-steady approach of the generalized unsteady incompressible aerodynamic forces. The oscillations of such aeroelastic system can be suppressed using linear active control techniques. In the case when the control is saturated the stability domain shrinks. The describing function method is used in this paper to determine the periodic solutions of an experimental aeroelastic system for two control laws.

APA, Harvard, Vancouver, ISO, and other styles

12

Party, Petra, Csilla Bartos, Árpád Farkas, Piroska Szabó-Révész, and Rita Ambrus. "Formulation and In Vitro and In Silico Characterization of “Nano-in-Micro” Dry Powder Inhalers Containing Meloxicam." Pharmaceutics 13, no. 2 (February 3, 2021): 211. http://dx.doi.org/10.3390/pharmaceutics13020211.

Full text

Abstract:

Pulmonary delivery has high bioavailability, a large surface area for absorption, and limited drug degradation. Particle engineering is important to develop inhalable formulations to improve the therapeutic effect. In our work, the poorly water-soluble meloxicam (MX) was used as an active ingredient, which could be useful for the treatment of non-small cell lung cancer, cystic fibrosis, and chronic obstructive pulmonary disease. We aimed to produce inhalable “nano-in-micro” dry powder inhalers (DPIs) containing MX and additives (poly-vinyl-alcohol, leucine). We targeted the respiratory zone with the microcomposites and reached a higher drug concentration with the nanonized active ingredient. We did the following investigations: particle size analysis, morphology, density, interparticular interactions, crystallinity, in vitro dissolution, in vitro permeability, in vitro aerodynamics (Andersen cascade impactor), and in silico aerodynamics (stochastic lung model). We worked out a preparation method by combining wet milling and spray-drying. We produced spherical, 3–4 µm sized particles built up by MX nanoparticles. The increased surface area and amorphization improved the dissolution and diffusion of the MX. The formulations showed appropriate aerodynamical properties: 1.5–2.4 µm MMAD and 72–76% fine particle fraction (FPF) values. The in silico measurements proved the deposition in the deeper airways. The samples were suitable for the treatment of local lung diseases.

APA, Harvard, Vancouver, ISO, and other styles

13

Barlas, Thanasis, Eva Jost, Georg Pirrung, Theofanis Tsiantas, Vasilis Riziotis, Sachin T. Navalkar, Thorsten Lutz, and Jan-Willem van Wingerden. "Benchmarking aerodynamic prediction of unsteady rotor aerodynamics of active flaps on wind turbine blades using ranging fidelity tools." Journal of Physics: Conference Series 753 (September 2016): 022027. http://dx.doi.org/10.1088/1742-6596/753/2/022027.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Pastrikakis, V. A., R. Steijl, and G. N. Barakos. "Effect of active Gurney flaps on overall helicopter flight envelope." Aeronautical Journal 120, no. 1230 (June 7, 2016): 1230–61. http://dx.doi.org/10.1017/aer.2016.57.

Full text

Abstract:

ABSTRACTThis paper presents a study of the W3-Sokol main rotor equipped with Gurney flaps. The effect of the active Gurney is tested at low and high forward flight speeds to draw conclusions about the potential enhancement of the rotorcraft performance for the whole flight envelope. The effect of the flap on the trimming and handling of a full helicopter is also investigated. Fluid and structure dynamics were coupled in all cases, and the rotor was trimmed at different thrust coefficients. The Gurney proved to be efficient at medium to high advance ratios, where the power requirements of the rotor were decreased by up to 3.3%. However, the 1/rev actuation of the flap might be an issue for the trimming and handling of the helicopter. The current study builds on the idea that any active mechanism operating on a rotor could alter the dynamics and the handling of the helicopter. A closed loop actuation of the Gurney flap was put forward based on a pressure divergence criterion, and it led to further enhancement of the aerodynamic performance. Next, a generic light utility helicopter was built using 2D aerodynamics of the main aerofoil section of the W3 Sokol blade along with a robust controller, and the response of the rotorcraft to control inputs was tested. This analysis proved that the 1/Rev actuation of the Gurney did not alter the handling qualities of the helicopter, and as a result, it can be implemented as a flow control mechanism for aerodynamic enhancement and retreating blade stall alleviation.

APA, Harvard, Vancouver, ISO, and other styles

15

Nakashima, Takuji, Chao Yan, Takashi Moriuchi, Itsuhei Kohri, Hidemi Mutsuda, and Yasuaki Doi. "Active aerodynamics control of simplified vehicle body in a crosswind condition." Journal of Engineering 2020, no. 14 (November 1, 2020): 1005–11. http://dx.doi.org/10.1049/joe.2020.0062.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Dai, Hu, Haoxiang Luo, and James F. Doyle. "Dynamic pitching of an elastic rectangular wing in hovering motion." Journal of Fluid Mechanics 693 (January 17, 2012): 473–99. http://dx.doi.org/10.1017/jfm.2011.543.

Full text

Abstract:

AbstractIn order to study the role of the passive deformation in the aerodynamics of insect wings, we computationally model the three-dimensional fluid–structure interaction of an elastic rectangular wing at a low aspect ratio during hovering flight. The code couples a viscous incompressible flow solver based on the immersed-boundary method and a nonlinear finite-element solver for thin-walled structures. During a flapping stroke, the wing surface is dominated by non-uniform chordwise deformations. The effects of the wing stiffness, mass ratio, phase angle of active pitching, and Reynolds number are investigated. The results show that both the phase and the rate of passive pitching due to the wing flexibility can significantly modify the aerodynamics of the wing. The dynamic pitching depends not only on the specified kinematics at the wing root and the stiffness of the wing, but also greatly on the mass ratio, which represents the relative importance of the wing inertia and aerodynamic forces in the wing deformation. We use the ratio between the flapping frequency, $\omega $, and natural frequency of the wing, ${\omega }_{n} $, as the non-dimensional stiffness. In general, when $\omega / {\omega }_{n} \leq 0. 3$, the deformation significantly enhances the lift and also improves the lift efficiency despite a disadvantageous camber. In particular, when the inertial pitching torque is assisted by an aerodynamic torque of comparable magnitude, the lift efficiency can be markedly improved.

APA, Harvard, Vancouver, ISO, and other styles

17

V, Somashekar. "A Computational Investigation of Unsteady Aerodynamics of Insect-Inspired Fixed Wing Micro Aerial Vehicle’s 2D Airfoil." Advances in Aerospace Engineering 2014 (June 17, 2014): 1–7. http://dx.doi.org/10.1155/2014/504049.

Full text

Abstract:

A Micro air vehicle (MAV) is defined as class of unmanned air vehicle (UAV) having a linear dimension of less than 15 centimeters and a mass of less than 100 grams with flight speeds of 6 to 12 meters per second. MAVs fall within a Reynolds number (Re) range of 50,000 and 120,000, in which many causes of unsteady aerodynamic effects are not fully understood. The research field of low Reynolds number aerodynamics is currently an active one, with many defence organizations, universities, and corporations working towards a better understanding of the physical processes of this aerodynamic regime. In the present work, it is proposed to study the unsteady aerodynamic analysis of 2D airfoil using CFD software and Xfoil panel code method. The various steps involved in this work are geometric modelling using CATIA V5R17, meshing using ICEM CFD, and solution and postprocessing through FLUENT. The finite control volume analysis and Xfoil panel code method has been carried out to predict aerodynamic characteristics such as lift coefficients, drag coefficients, moment coefficients, pressure coefficients, and flow visualization. The lift and drag coefficients were compared for all the simulations with experimental results. It was observed that for the 2D airfoil, lift and drag both compared well for the midrange angle of attack from −10 to 15 degree AOA.

APA, Harvard, Vancouver, ISO, and other styles

18

Liu, Hao, Sridhar Ravi, Dmitry Kolomenskiy, and Hiroto Tanaka. "Biomechanics and biomimetics in insect-inspired flight systems." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1704 (September 26, 2016): 20150390. http://dx.doi.org/10.1098/rstb.2015.0390.

Full text

Abstract:

Insect- and bird-size drones—micro air vehicles (MAV) that can perform autonomous flight in natural and man-made environments are now an active and well-integrated research area. MAVs normally operate at a low speed in a Reynolds number regime of 10 4 –10 5 or lower, in which most flying animals of insects, birds and bats fly, and encounter unconventional challenges in generating sufficient aerodynamic forces to stay airborne and in controlling flight autonomy to achieve complex manoeuvres. Flying insects that power and control flight by flapping wings are capable of sophisticated aerodynamic force production and precise, agile manoeuvring, through an integrated system consisting of wings to generate aerodynamic force, muscles to move the wings and a control system to modulate power output from the muscles. In this article, we give a selective review on the state of the art of biomechanics in bioinspired flight systems in terms of flapping and flexible wing aerodynamics, flight dynamics and stability, passive and active mechanisms in stabilization and control, as well as flapping flight in unsteady environments. We further highlight recent advances in biomimetics of flapping-wing MAVs with a specific focus on insect-inspired wing design and fabrication, as well as sensing systems. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight’.

APA, Harvard, Vancouver, ISO, and other styles

19

Ahangarnejad, Arash Hosseinian, Stefano Melzi, and Mehdi Ahmadian. "Integrated Vehicle Dynamics System through Coordinating Active Aerodynamics Control, Active Rear Steering, Torque Vectoring and Hydraulically Interconnected Suspension." International Journal of Automotive Technology 20, no. 5 (August 10, 2019): 903–15. http://dx.doi.org/10.1007/s12239-019-0084-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Dimino, Ignazio, Giovanni Andreutti, Frédéric Moens, Federico Fonte, Rosario Pecora, and Antonio Concilio. "Integrated Design of a Morphing Winglet for Active Load Control and Alleviation of Turboprop Regional Aircraft." Applied Sciences 11, no. 5 (March 9, 2021): 2439. http://dx.doi.org/10.3390/app11052439.

Full text

Abstract:

Aircraft winglets are well-established devices that improve aircraft fuel efficiency by enabling a higher lift over drag ratios and lower induced drag. Retrofitting winglets to existing aircraft also increases aircraft payload/range by the same order of the fuel burn savings, although the additional loads and moments imparted to the wing may impact structural interfaces, adding more weight to the wing. Winglet installation on aircraft wing influences numerous design parameters and requires a proper balance between aerodynamics and weight efficiency. Advanced dynamic aeroelastic analyses of the wing/winglet structure are also crucial for this assessment. Within the scope of the Clean Sky 2 REG IADP Airgreen 2 project, targeting novel technologies for next-generation regional aircraft, this paper deals with the integrated design of a full-scale morphing winglet for the purpose of improving aircraft aerodynamic efficiency in off-design flight conditions, lowering wing-bending moments due to maneuvers and increasing aircraft flight stability through morphing technology. A fault-tolerant morphing winglet architecture, based on two independent and asynchronous control surfaces with variable camber and differential settings, is presented. The system is designed to face different flight situations by a proper action on the movable control tabs. The potential for reducing wing and winglet loads by means of the winglet control surfaces is numerically assessed, along with the expected aerodynamic performance and the actuation systems’ integration in the winglet surface geometry. Such a device was designed by CIRA for regional aircraft installation, whereas the aerodynamic benefits and performance were estimated by ONERA on the natural laminar flow wing. An active load controller was developed by PoliMI and UniNA performed aeroelastic trade-offs and flutter calculations due to the coupling of winglet movable harmonics and aircraft wing bending and torsion.

APA, Harvard, Vancouver, ISO, and other styles

21

Stuermer, A., J. Yin, and R. Akkermans. "Progress in aerodynamic and aeroacoustic integration of CROR propulsion systems." Aeronautical Journal 118, no. 1208 (October 2014): 1137–58. http://dx.doi.org/10.1017/s0001924000009829.

Full text

Abstract:

Abstract Contra-Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as an economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In the past five years, DLR’s Institute of Aerodynamics and Flow Technology has performed a number of numerical studies investigating important aspects relating to engine-airframe integration of CROR engines. In this article an overview of coupled aerodynamic and aeroacoustic simulations investigating representative pusher-configuration CROR engines will be given, focusing on the impact on aerodynamic performance and aeroacoustics caused by the presence of a pylon, the potential for noise reduction by employing trailing-edge blowing at the pylon trailing edge as well as the performance and noise variations caused by different senses of rotation of the rotors. It is shown that the interaction with the pylon strongly impacts blade performance and front rotor noise emissions but that the use of active flow control in the form of pylon trailing-edge blowing can alleviate these adverse installation effects to a notable extent.

APA, Harvard, Vancouver, ISO, and other styles

22

Zulkefli, Nur Faraihan, Zulhilmy Sahwee, Nurhayati Mohd Nur, Muhamad Nor Ashraf Mohd Fazil, and Muaz Mohd Shukri. "Lift Augmentation between Passive and Active Vortex Generator." Applied Mechanics and Materials 851 (August 2016): 532–37. http://dx.doi.org/10.4028/www.scientific.net/amm.851.532.

Full text

Abstract:

This study was conducted to investigate the performance of passive and active vortex generator on the wing’s flap. The triangular shape of passive vortex generator (VG) was developed and attached on the wing’s flap leading edge while the plasma actuator performed as active vortex generator. The test was carried out experimentally using subsonic wind tunnel with 300 angles extended flap. Three different types of turbulent flow; with Reynolds number 1.5 x105, 2.0 x105, and 2.6x105 were used to study the aerodynamics forces of airfoil with plasma actuator OFF. All Reynolds number used were below 1x106. The result indicated that airfoil with plasma actuator produced higher lift coefficient 12% and lift-to-drag ratio 5% compared to airfoil with passive vortex generator. The overall result showed that airfoil with plasma actuator produced better lift forces compared to passive vortex generator.

APA, Harvard, Vancouver, ISO, and other styles

23

Dominy, J., and D. N. Bulman. "An Active Suspension for a Formula One Grand Prix Racing Car." Journal of Dynamic Systems, Measurement, and Control 107, no. 1 (March 1, 1985): 73–79. http://dx.doi.org/10.1115/1.3140710.

Full text

Abstract:

During 1982, Formula 1 racing cars generated very high downforces by the use of “ground effect” aerodynamics. Such cars required very stiff suspensions to maintain a reasonably constant ride height with the result that the slightest bump unsettled the chassis and reduced cornering speeds. A semi-active suspension would have been capable of withstanding the variations in downforce while remaining “soft” to rapid road inputs. This paper proposes such a system and decribes an analysis of its dynamic responses. It demonstates that it is able to maintain a sensibly constant ride height and attitude during cornering, braking, and acceleration, while minimizing the chassis response to individual bumps.

APA, Harvard, Vancouver, ISO, and other styles

24

Schreck, Scott J., Michael C. Robinson, M. Maureen Hand, and David A. Simms. "Blade Dynamic Stall Vortex Kinematics for a Horizontal Axis Wind Turbine in Yawed Conditions*." Journal of Solar Energy Engineering 123, no. 4 (June 1, 2001): 272–81. http://dx.doi.org/10.1115/1.1408307.

Full text

Abstract:

Horizontal axis wind turbines routinely suffer significant time varying aerodynamic loads that adversely impact structures, mechanical components, and power production. As lighter and more flexible wind turbines are designed to reduce overall cost of energy, greater accuracy and reliability will become even more crucial in future aerodynamics models. However, to render calculations tractable, current modeling approaches admit various approximations that can degrade model predictive accuracy. To help understand the impact of these modeling approximations and improve future models, the current effort seeks to document and comprehend the vortex kinematics for three-dimensional, unsteady, vortex dominated flows occurring on horizontal axis wind turbine blades during non-zero yaw conditions. To experimentally characterize these flows, the National Renewable Energy Laboratory Unsteady Aerodynamics Experiment turbine was erected in the NASA Ames 80 ft×120 ft wind tunnel. Then, under strictly-controlled inflow conditions, turbine blade surface pressures and local inflow velocities were acquired at multiple radial locations. Surface pressure histories and normal force records were used to characterize dynamic stall vortex kinematics and normal forces. Stall vortices occupied approximately two-thirds of the aerodynamically active blade span and persisted for nearly one-fourth of the blade rotation cycle. Stall vortex convection varied dramatically along the blade radius, yielding pronounced dynamic stall vortex deformation. Analysis of these data revealed systematic alterations to vortex kinematics due to changes in test section speed, yaw error, and blade span location.

APA, Harvard, Vancouver, ISO, and other styles

25

Pak, Chan-Gi, Peretz P. Friedmann, and Eli Livne. "Digital Adaptive Flutter Suppression and Simulation Using Approximate Transonic Aerodynamics." Journal of Vibration and Control 1, no. 4 (October 1995): 363–88. http://dx.doi.org/10.1177/107754639500100401.

Full text

Abstract:

A digital adaptive controller, using a trailing edge control surface, is introduced for the active flutter suppression of wings undergoing time varying flight conditions. The aeroservoelastic system is modeled in the time domain by a deterministic Auto Regressive Moving Average (ARMA) model together with a parameter estimator. Linear quadratic controller gains at each time step are obtained using an iterative Riccati solver. Aeroservoelastic transient response is obtained using Roger's approximation, state transition matrices, and an iterative time marching algorithm. Simulations of system performance for flights into the transonic speed regime are used to demonstrate suppression of flutter and divergence instabilities.

APA, Harvard, Vancouver, ISO, and other styles

26

Dickinson, Michael H., and Florian T. Muijres. "The aerodynamics and control of free flight manoeuvres in Drosophila." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1704 (September 26, 2016): 20150388. http://dx.doi.org/10.1098/rstb.2015.0388.

Full text

Abstract:

A firm understanding of how fruit flies hover has emerged over the past two decades, and recent work has focused on the aerodynamic, biomechanical and neurobiological mechanisms that enable them to manoeuvre and resist perturbations. In this review, we describe how flies manipulate wing movement to control their body motion during active manoeuvres, and how these actions are regulated by sensory feedback. We also discuss how the application of control theory is providing new insight into the logic and structure of the circuitry that underlies flight stability. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight’.

APA, Harvard, Vancouver, ISO, and other styles

27

Tesař, Václav. "Aerodynamics of Monolithic Matrices for Supporting Solid Reactant or Catalyst." Energies 12, no. 17 (September 3, 2019): 3398. http://dx.doi.org/10.3390/en12173398.

Full text

Abstract:

Heterogeneous solid/fluid chemical reactions—as well as reactions dependent on solid catalysts—require spreading the active solid substance on the largest accessible area. The solution is a thin layer covering as much as possible convoluted surface of an inert support. This is nowadays the internal surface of narrow parallel passages. The supporting body is usually ceramic, its passages now mostly of square cross section. Reliable detailed knowledge of pressure drop across the set of passages has to be available, especially for flow control based on fluid property changes (e.g., with temperature or fluid composition). This paper presents results of laboratory measurements as well as numerical flowfield computations of the passage flows, with discovered universal law.

APA, Harvard, Vancouver, ISO, and other styles

28

Tang, Peng, Fei Wang, and Yuehong Dai. "Controller Design for Different Electric Tail Rotor Operating Modes in Helicopters." International Journal of Pattern Recognition and Artificial Intelligence 33, no. 08 (June 25, 2019): 1959022. http://dx.doi.org/10.1142/s0218001419590225.

Full text

Abstract:

The nonlinear aerodynamics and new kinds of operation associated with helicopter electric tail rotors (ETRs) make accurate speed tracking control under complex flight conditions a key challenge confronting designers. In this paper, we present an electric propulsion system for tail rotors that uses a high-power-density permanent magnet motor. The management of aerodynamic disturbance rejection and accurate speed control are aspects of ETR design that require particularly close attention. To this end, we have developed a speed controller that is based on an active disturbance rejection control (ADRC) technique that can handle fixed speed and adjustable pitch-angle modes. We have also applied a linear extended state observer (LESO) with a self-tuning bandwidth to estimate fluctuations in the drive system. For variable speeds, a simple controller combined with an adaptive radial basis function (RBF) observer and nonlinear state error feedback using ADRC was designed to replace LESO while avoiding any dependence on the system parameters. The stability of the controllers was analyzed and their effectiveness was verified using a simulation platform. Test results showed that the propulsion system is able to achieve fast dynamic response and aerodynamic disturbance rejection.

APA, Harvard, Vancouver, ISO, and other styles

29

Cesnik, C. E. S., D. G. Opoku, F. Nitzsche, and T. Cheng. "Active twist rotor blade modelling using particle-wake aerodynamics and geometrically exact beam structural dynamics." Journal of Fluids and Structures 19, no. 5 (June 2004): 651–68. http://dx.doi.org/10.1016/j.jfluidstructs.2004.01.007.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Bushnell, D. M. "Aircraft drag reduction—a review." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 217, no. 1 (January 1, 2003): 1–18. http://dx.doi.org/10.1243/095441003763031789.

Full text

Abstract:

The paper summarizes the state of the art in aeronautical drag reduction across the speed range for the “conventional” drag components of viscous drag, drag due to lift and wave drag. It also describes several emerging drag-reduction approaches that are either active or reactive/interactive and the drag reduction potentially available from synergistic combinations of advanced configuration aerodynamics, viscous drag-reduction approaches, revolutionary structural concepts and propulsion integration.

APA, Harvard, Vancouver, ISO, and other styles

31

Ristroph, Leif, Gunnar Ristroph, Svetlana Morozova, Attila J. Bergou, Song Chang, John Guckenheimer, Z. Jane Wang, and Itai Cohen. "Active and passive stabilization of body pitch in insect flight." Journal of The Royal Society Interface 10, no. 85 (August 6, 2013): 20130237. http://dx.doi.org/10.1098/rsif.2013.0237.

Full text

Abstract:

Flying insects have evolved sophisticated sensory–motor systems, and here we argue that such systems are used to keep upright against intrinsic flight instabilities. We describe a theory that predicts the instability growth rate in body pitch from flapping-wing aerodynamics and reveals two ways of achieving balanced flight: active control with sufficiently rapid reactions and passive stabilization with high body drag. By glueing magnets to fruit flies and perturbing their flight using magnetic impulses, we show that these insects employ active control that is indeed fast relative to the instability. Moreover, we find that fruit flies with their control sensors disabled can keep upright if high-drag fibres are also attached to their bodies, an observation consistent with our prediction for the passive stability condition. Finally, we extend this framework to unify the control strategies used by hovering animals and also furnish criteria for achieving pitch stability in flapping-wing robots.

APA, Harvard, Vancouver, ISO, and other styles

32

Lehmkuhl, Oriol, Adrián Lozano-Durán, and Ivette Rodriguez. "Active flow control for external aerodynamics: from micro air vehicles to a full aircraft in stall." Journal of Physics: Conference Series 1522 (April 2020): 012017. http://dx.doi.org/10.1088/1742-6596/1522/1/012017.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Yang, Yang, Chun Li, Wanfu Zhang, Xueyan Guo, and Quanyong Yuan. "Investigation on aerodynamics and active flow control of a vertical axis wind turbine with flapped airfoil." Journal of Mechanical Science and Technology 31, no. 4 (April 2017): 1645–55. http://dx.doi.org/10.1007/s12206-017-0312-0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Mattaboni, M., P. Masarati, and P. Mantegazza. "Multibody simulation of a generalized predictive controller for tiltrotor active aeroelastic control." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 226, no. 2 (December 7, 2011): 197–216. http://dx.doi.org/10.1177/0954410011406203.

Full text

Abstract:

A generalized predictive control has been developed for the control of the aeroelasticity and structural dynamics of a tiltrotor. Adaptivity is the key feature of the proposed technique. It gives the controller the capability to autonomously follow the variations of the system. A comprehensive simulation system has been adopted to design and test the adaptive regulator under realistic conditions. The aeroservoelastic tiltrotor has been modelled using a multibody approach, considering the structural dynamics, the aerodynamics, the blade pitch control system kinematics, and actuator and sensor dynamics. Numerical simulations illustrate the capability of the adaptive controller to reduce wing vibrations and loads while significantly extending the flutter-free flight envelope. This controller shows satisfactory performances within the whole flight envelope as it is able to properly work in different rotor trim conditions and varying structural properties in the presence of external disturbances and measurement noise.

APA, Harvard, Vancouver, ISO, and other styles

35

Grosche, F. R., and G. E. A. Meier. "Research at DLR Göttingen on bluff body aerodynamics, drag reduction by wake ventilation and active flow control." Journal of Wind Engineering and Industrial Aerodynamics 89, no. 14-15 (December 2001): 1201–18. http://dx.doi.org/10.1016/s0167-6105(01)00161-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Jorge, Ahmed, Christina Dastolfo-Hromack, Witold J. Lipski, Ian H. Kratter, Libby J. Smith, Jackie L. Gartner-Schmidt, and R. Mark Richardson. "Anterior Sensorimotor Subthalamic Nucleus Stimulation Is Associated With Improved Voice Function." Neurosurgery 87, no. 4 (March 21, 2020): 788–95. http://dx.doi.org/10.1093/neuros/nyaa024.

Full text

Abstract:

Abstract Background Despite the impact of Parkinson disease (PD) on speech communication, there is no consensus regarding the effect of lead location on voice-related outcomes in subthalamic nucleus (STN) deep brain stimulation (DBS). Objective To determine the relationship of stimulation location to changes in cepstral analyses of voice following STN DBS. Methods Speech pathology evaluations were obtained from 14 PD subjects, before and after STN DBS, including audio-perceptual voice ratings (overall severity, loudness, hoarseness changes), measured indices of dysphonia (cepstral peak prominence and cepstral spectral index of dysphonia), and phonatory aerodynamics. The contact locations used for active stimulation at the time of postoperative voice evaluations were determined and assessed in relation to voice outcomes. Results Voice outcomes remained relatively unchanged on average. Stimulation locations in the anterior portion of the sensorimotor region of the left STN, however, were associated with improvements in voice severity scores, cepstral spectral index of dysphonia, shortness of breath, and phonatory airflow during connected speech. Posterior locations were associated with worsening of these outcomes. Variation in the medial-lateral or dorsal-ventral position on the left, and in any direction on the right, did not correlate with any voice outcome. Conclusion Active contact placement within the anterior sensorimotor STN was associated with improved perceptual and acoustic-aerodynamic voice-related outcomes. These findings suggest an STN topography for improving airflow for speech, in turn improving how PD patients’ voices sound.

APA, Harvard, Vancouver, ISO, and other styles

37

Rozov, Vladyslav, Andreas Volmering, Andreas Hermanutz, Mirko Hornung, and Christian Breitsamter. "CFD-Based Aeroelastic Sensitivity Study of a Low-Speed Flutter Demonstrator." Aerospace 6, no. 3 (March 6, 2019): 30. http://dx.doi.org/10.3390/aerospace6030030.

Full text

Abstract:

The goal of developing aircraft that are greener, safer and cheaper can only be maintained through significant innovations in aircraft design. An integrated multidisciplinary design approach can lead to an increase in the performance of future derivative aircraft. Advanced aerodynamics and structural design technologies can be achieved by both passive and active suppression of aeroelastic instabilities. To demonstrate the potential of this approach, the EU-funded project Flutter Free Flight Envelope Expansion for Economical Performance Improvement is developing an unmanned aerial vehicle with a high-aspect-ratio-wing and clearly defined flutter characteristics. The aircraft is used as an experimental test platform. The scope of this work is the investigation of the aeroelastic behaviour of the aircraft and the determination of its flutter limits. The modeling of unsteady aerodynamics is performed by means of the small disturbance CFD approach that provides higher fidelity compared to conventional linear-potential-theory-based methods. The CFD-based and the linear-potential-theory-based results are compared and discussed. Furthermore, the sensitivity of the flutter behaviour to the geometric level of detail of the CFD model is evaluated.

APA, Harvard, Vancouver, ISO, and other styles

38

Haan, Fred L. Jr, Partha P. Sarkar, and Nicholas J. Spencer-Berger. "Development of an active gust generation mechanism on a wind tunnel for wind engineering and industrial aerodynamics applications." Wind and Structures 9, no. 5 (October 25, 2006): 369–86. http://dx.doi.org/10.12989/was.2006.9.5.369.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Karpuk, Stanislav, Snorri Gudmundsson, and Vladimir Golubev. "Feasibility Study of a Multi-Purpose Aircraft Concept with a Leading-Edge Embedded Cross-Flow Fan." Unmanned Systems 08, no. 01 (January 2020): 21–32. http://dx.doi.org/10.1142/s2301385020500028.

Full text

Abstract:

The research presented focuses on investigating the use of Cross-Flow Fan (CFF) as a high-lift device for a Short Take-off and Landing (STOL) aircraft. The wing-embedded fan performance analysis is mostly addressed from an aerodynamic perspective and focuses on using such Active Flow Control (AFC) technology in the conceptual aircraft design process. In particular, the design trade study of an aircraft featuring the fan as a high-lift device applied to a conceptual design of a medium-range multi-purpose aircraft is performed. A sensitivity analysis is employed to investigate the impact of the technology on the aircraft weight, aerodynamics, stability and control, and fight performance. The aircraft design modifications are introduced to maximize the aircraft mission performance given the fan specifications and constraints. Results indicate a reduction of the take-of field length by 18% with the payload penalty of 14%. The aircraft ferry range is also decreased by 7% compared to the baseline aircraft design. The scaling analysis of the aircraft concept is performed to determine the potential market for such technology. The results show that a light General Aviation (GA) airplane or a medium-large size Unmanned Aerial Vehicle (UAV) could benefit more from the wing-embedded CFF compared to more heavy airplanes.

APA, Harvard, Vancouver, ISO, and other styles

40

Kalarikovilagam Srinivasan and Bertram. "Preliminary Design and System Considerations for an Active Hybrid Laminar Flow Control System." Aerospace 6, no. 10 (October 1, 2019): 109. http://dx.doi.org/10.3390/aerospace6100109.

Full text

Abstract:

Hybrid laminar flow control or HLFC design is a complex and multi-disciplinary process, which demands a thorough understanding of all aspects from a global systems viewpoint. The objective of the paper is to present a preliminary design of important components of an HLFC system that helps in quick assessment of conceptual system architectures. This is important to evaluate feasibility, system performance, and overall aircraft benefits at early stages of system development. This paper also discusses the various important system requirements and issues concerning the design of active HLFC systems, and the interfaces between various disciplines are presented. It can be emphasized from the study that the future compressor design for the HLFC system should consider the thermal management aspects and additional mass flow requirements from the aerodynamics-structure design optimization and also from water drain system solutions. A method to calculate the accumulated water content inside the plenum chambers is presented, and the effect of a drain hole on the power consumption is studied. A low order thermal management study of the HLFC compressor motor shows a high temperature rise in the windings for very high speed motors for long duration operation and calls for effective cooling solutions.

APA, Harvard, Vancouver, ISO, and other styles

41

Richard, Robert E., John A. Rule, and Robert L. Clark. "Genetic Spatial Optimization of Active Elements on an Aeroelastic Delta Wing." Journal of Vibration and Acoustics 123, no. 4 (May 1, 2001): 466–71. http://dx.doi.org/10.1115/1.1389458.

Full text

Abstract:

This work outlines a cohesive approach for the design and implementation of a genetically optimized, active aeroelastic delta wing. Emphasis was placed on computational efficiency of model development and efficient means for optimizing sensor and actuator geometries. Reduced-order models of potential-flow aerodynamics were developed for facilitation of analysis and design of the aeroelastic system in the early design phase. Using these methods, models capturing “95% of the physics with 8% of the modeling effort” can be realized to evaluate various active and passive design considerations. The aeroelastic delta wing model was employed in determining the most effective locations and sizes for transducers required to provide flutter control. The basic design presented is based upon an analytical model of the structure. A comparison of optimization strategies led to the use of a genetic algorithm to determine the optimal transducer locations, sizes, and orientations required to provide effective flutter control based upon an open-loop performance metric. The genetic algorithm and performance metric essentially provided loop shaping through the adaptive structure design. An experimental model was then developed based upon the optimal transducer designs. Wind tunnel tests were performed to demonstrate closed-loop performance for flutter control. Results from this study indicate that a single sensor/actuator pair can be designed to extend the flutter boundary and selectively couple to only those modes required to control the response.

APA, Harvard, Vancouver, ISO, and other styles

42

Aho, Jacob P., Andrew D. Buckspan, Fiona M. Dunne, and Lucy Y. Pao. "Controlling Wind Energy for Utility Grid Reliability." Mechanical Engineering 135, no. 09 (September 1, 2013): S4—S12. http://dx.doi.org/10.1115/1.2013-sep-4.

Full text

Abstract:

This article provides an overview of utility grid operation by introducing the fundamental behavior of the electrical system, explaining the importance of maintaining grid reliability through balancing generation and load, and describing the methods of providing ancillary services using conventional utilities. This article also introduces the basic structural components of wind turbines, explains the traditional control systems for capturing maximum power, and highlights control methods developed in industry and academia to provide active power ancillary services with wind energy. As the penetration of wind energy continues to grow, the participation of wind turbines and wind farms in grid frequency stability is becoming more important. The future of wind energy development and deployment depends on many factors, such as policy decisions, economic markets, and technology improvements. Improvements through research and development in areas such as forecasting, turbine manufacturing processes, blade aerodynamics, power electronics, and active power control systems will continue to be a key driver for wind energy technology.

APA, Harvard, Vancouver, ISO, and other styles

43

H. Suffer, Kadhim, Yassr Y. Kahtan, and Zuradzman M. Razlan. "Aerodynamics and Modal Analysis for the Combined Vane type Vertical Axis Wind Turbine." International Journal of Engineering & Technology 7, no. 4.38 (December 3, 2018): 1395. http://dx.doi.org/10.14419/ijet.v7i4.38.27883.

Full text

Abstract:

The present global energy economy suggests the use of renewable sources such as solar, wind, and biomass to produce the required power. The vertical axis wind turbine is one of wind power applications. Usually, when the vertical axis wind turbine blades are designed from the airfoil, the starting torque problem begins. The main objective of this research is to numerically simulate the combination of movable vanes of a flat plate with the airfoil in a single blade configuration to solve the starting torque problem. CFD analysis in ANSYS-FLUENT and structural analysis in ANSYS of combined blade vertical axis wind turbine rotor has been undertaken. The first simulation is carried out to investigations the aerodynamic characteristic of the turbine by using the finite volume method. While the second simulation is carried out with finite element method for the modal analysis to find the natural frequencies and the mode shape in order to avoid extreme vibration and turbine failure, the natural frequencies, and their corresponding mode shapes are studied and the results were presented with damping and without damping for four selected cases. The predicted results show that the static pressure drop across the blade increase in the active blade side because of the vanes are fully closed and decrease in the negative side because of the all the vanes are fully open. The combined blade helps to increase turbine rotation and so, thus, the power of the turbine increases. While the modal results show that until the 5th natural frequency the effect of damping can be neglected. The predicted results show agreement with those reported in the literature for VAWT with different blade designs.

APA, Harvard, Vancouver, ISO, and other styles

44

Lin, Min. "Study of Badminton Net Shot Technology Based on Dynamics." Advanced Materials Research 791-793 (September 2013): 1431–35. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.1431.

Full text

Abstract:

In the sport of badminton, net shot is one of the extremely important technologies. With the continuous development and innovation of badminton sport, net technology has been paid more and more attention to. In addition, in many badminton games, it has become an important technical means to change active to passive by taking effective use of net shot changes. Firstly, this paper elaborates the division of badminton net technology area and technology selection. And then, based on this, combined with the principle of aerodynamics, this paper makes an analysis on the dynamics of badminton net techniques. At the same time, this paper also makes an analysis on the dynamics of net ball chop technique. Thus, to some extent, it provides theoretical basis and technical guidance for the teaching and practice of badminton net shot.

APA, Harvard, Vancouver, ISO, and other styles

45

Piao, Minnan, Youan Zhang, Mingwei Sun, Zhihong Yang, Zenghui Wang, and Zengqiang Chen. "Adaptive aeroservoelastic mode stabilization of flexible airbreathing hypersonic vehicle." Journal of Vibration and Control 25, no. 15 (May 20, 2019): 2124–42. http://dx.doi.org/10.1177/1077546319849775.

Full text

Abstract:

The statically unstable airbreathing hypersonic vehicle requires a high-bandwidth controller to control the instability, which results in intricate interactions among the aerodynamics, the low-frequency structural modes, and the flight control system. Especially, the structural frequencies are uncertain and time-varying, which further raises the difficulty of controller design. In this paper, two adaptive aeroservoelastic mode stabilization methods are proposed. First, the condition of phase stabilization is given under the linear active disturbance rejection control framework to realize the self-stabilization of the flexible modes. Then, an adaptive notch filter, which employs the lattice type structure and the fast-recursive square root algorithm, is presented. Both methods can achieve the adaptive vibration suppression and extend the control bandwidth. Simulation results demonstrate the effectiveness of the proposed approach.

APA, Harvard, Vancouver, ISO, and other styles

46

UEDA, Tetsuhiko, and Kenichi SAITOH. "NUMERICAL SIMULATION FOR RANDOM AEROELASTIC RESPONSES USING INVERSE FOURIER TRANSFORM." Aviation 20, no. 3 (September 29, 2016): 103–9. http://dx.doi.org/10.3846/16487788.2016.1227535.

Full text

Abstract:

This paper reports a new simulation technique for an aeroelastic system which responds to random external forces. Since the aeroelastic system including the effects of unsteady aerodynamics is ordinarily described in the frequency domain, the Inverse Discrete Fourier Transform (IDFT) can be utilized to simulate its random response. The response caused by the external random noise is calculated through a transfer function first in the frequency domain and then converted to the time domain. The objective of the present study is to provide mathematical time history data for evaluating the various estimation methods of the flutter boundary from subcritical responses in flight and/or wind tunnel testing. An example application to the method of flutter prediction is shown. The technique can also be used to evaluate the effects of the active control device coping with atmospheric turbulence.

APA, Harvard, Vancouver, ISO, and other styles

47

Mokina, N. A., V. Yu Zeilert, N. I. Saraeva, G. M. Sakharova, and N. S. Antonov. "Prevalence and particular features of tobacco smoking among adolescents in Chapaevsk, Samara region." PULMONOLOGIYA, no. 6 (December 28, 2007): 58–62. http://dx.doi.org/10.18093/0869-0189-2007-0-6-58-62.

Full text

Abstract:

Under the epidemic rising of tobacco consumption among working-aged people worldwide, there is little Russian detailed data on prevalence and particularities of active and passive tobacco smoking among adolescents. The present 4-stage study involved schoolchildren and students of trade schools (13 to 18 years of age) at Chapaevsk, which is a large industry center of Samara region. The prevalence of tobacco smoking among these adolescents was as high as 28 %. The average age of starting smoking was 14.7 ± 0.4 yrs. A significant effect of tobacco smoking on airway aerodynamics and low motivation for quitting the smoking were found. The most of adolescents had low nicotine dependence but were poorly motivated for smoking cessation and highly influenced by the social surroundings to re-start smoking. The majority of adolescents renewed smoking after return to habitual social conditions.

APA, Harvard, Vancouver, ISO, and other styles

48

Löffler, Stephan, Carola Ebert, and Julien Weiss. "Fluidic-Oscillator-Based Pulsed Jet Actuators for Flow Separation Control." Fluids 6, no. 4 (April 20, 2021): 166. http://dx.doi.org/10.3390/fluids6040166.

Full text

Abstract:

The control of flow separation on aerodynamic surfaces remains a fundamental goal for future air transportation. On airplane wings and control surfaces, the effects of flow separation include decreased lift, increased drag, and enhanced flow unsteadiness and noise, all of which are detrimental to flight performance, fuel consumption, and environmental emissions. Many types of actuators have been designed in the past to counter the negative effects of flow separation, from passive vortex generators to active methods like synthetic jets, plasma actuators, or sweeping jets. At the Chair of Aerodynamics at TU Berlin, significant success has been achieved through the use of pulsed jet actuators (PJA) which operate by ejecting a given amount of fluid at a specified frequency through a slit-shape slot on the test surface, thereby increasing entrainment and momentum in a separating boundary layer and thus delaying flow separation. Earlier PJAs were implemented using fast-switching solenoid valves to regulate the jet amplitude and frequency. In recent years, the mechanical valves have been replaced by fluidic oscillators (FO) in an attempt to generate the desired control authority without any moving parts, thus paving the way for future industrial applications. In the present article, we present in-depth flow and design analysis which affect the operation of such FO-based PJAs. We start by reviewing current knowledge on the mechanism of flow separation control with PJAs before embarking on a detailed analysis of single-stage FO-based PJAs. In particular, we show that there is a fundamental regime where the oscillation frequency is mainly driven by the feedback loop length. Additionally, there are higher-order regimes where the oscillation frequency is significantly increased. The parameters that influence the oscillation in the different regimes are discussed and a strategy to incorporate this new knowledge into the design of future actuators is proposed.

APA, Harvard, Vancouver, ISO, and other styles

49

ALDRIDGE, H. D. J. N. "Body Accelerations During the Wingbeat in Six Bat Species: The Function of the Upstroke in Thrust Generation." Journal of Experimental Biology 130, no. 1 (July 1, 1987): 275–93. http://dx.doi.org/10.1242/jeb.130.1.275.

Full text

Abstract:

The kinematics and aerodynamics of Rhinolophus ferrumequinum, R. hipposideros, Myotis nattereri, M. mystacinus, Plecotus auritus and Eptesicus serotinus in horizontal flight at various flight speeds are described. Three kinematic patterns can be recognized. At low speeds M. nattereri, M. mystacinus and P. auritus use a ‘tip-reversal’ upstroke in which thrust is generated during the backward ‘flick’ of the chiropatagium. R. hipposideros also uses this kinematic pattern, but does not appear to generate thrust during the upstroke. Both R. ferrumequinum flying at 3.12 m s−1 and E. serotinus flying at 3.44 m s−1 accelerate during the ‘vertical’ upstroke (in which the wings move perpendicularly to the flight path), indicating that their wings are active. When flying at 4.16 m s−1, E. serotinus also uses a ‘vertical’ upstroke, but in this case it decelerates, which suggests that thrust is not being generated. At minimum power speed (4.8 m s−1), R. ferrumequinum uses a ‘reduced-span’ upstroke, thrust is not generated during the upstroke and the animal decelerates.

APA, Harvard, Vancouver, ISO, and other styles

50

Jayaraman, Balaji, Siddharth Thakur, and Wei Shyy. "Modeling of Fluid Dynamics and Heat Transfer Induced by Dielectric Barrier Plasma Actuator." Journal of Heat Transfer 129, no. 4 (January 2, 2007): 517–25. http://dx.doi.org/10.1115/1.2709659.

Full text

Abstract:

Glow discharge at atmospheric pressure using a dielectric barrier discharge can induce fluid flow, and can be used for active control of aerodynamics and heat transfer. In the present work, a modeling framework is presented to study the evolution and interaction of such athermal nonequilibrium plasma discharges in conjunction with low Mach number fluid dynamics and heat transfer. The model is self-consistent, coupling the first-principles-based discharge dynamics with the fluid dynamics and heat transfer equations. Under atmospheric pressure, the discharge can be simulated using a plasma–fluid instead of a kinetic model. The plasma and fluid species are treated as a two-fluid system coupled through force and pressure interactions, over decades of length and time scales. The multiple-scale processes such as convection, diffusion, and reaction/ionization mechanisms make the transport equations of the plasma dynamics stiff. To handle the stiffness, a finite-volume operator-split algorithm capable of conserving space charge is employed. A body force treatment is devised to link the plasma dynamics and thermo-fluid dynamics. The potential of the actuator for flow control and thermal management is illustrated using case studies.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Active aerodynamics'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles