Artigos - Engenharia Aeronáutica - São João da Boa Vista

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https://hdl.handle.net/11449/204197

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Agora exibindo 1 - 10 de 10

Efeitos da aplicação de piezocerâmicas no comportamento aeroelástico de rotores submetidos ao whirl-flutter
(2022-04-22) Bastos, Sérvio Túlio Suenai Haramura [UNESP]; De Vasconcellos, Rui Marcos Grombone [UNESP]; Universidade Estadual Paulista (Unesp)
Com o advento da mobilidade aérea do futuro torna-se fundamental a análise de táticas de controle vibracional para o desenvolvimentos de aeronaves mais eficientes. Sendo que a aplicação de piezoelétricos para o controle do whirl-flutter devem ser analisadas para que se aumente das margens de estabilidade e se controle vibrações
Vibrações induzidas por vórtice em um cilindro com um grau de liberdade e rigidez não linear
(2019-11-15) Bastos, Sérvio Túlio Suenai Haramura [UNESP]; Vasconcellos, Rui Marcos Grombone de [UNESP]; Marques, Flávio Donizeti; Universidade Estadual Paulista (Unesp)
In this research project, it is proposed an investigation of the effects of hardening structural nonlinearity in a single degree of freedom cylinder exposed to a transverse flow, presenting the vortex induced vibration effect. To check the validity of the implemented phenomenological model, numerical simulations has been performed and the results has been compared with experiments. Simulations showed that the presence of this type of nonlinearity extends the lock-in region by changing the structural natural frequency with the freestream speed and the vortex shedding frequency. A wind tunnel test validated the obtained simulated results. The contributions of this research can be helpful in order to prevent vortex induced vibrations in realistic nonlinear structures.
Amplitude reduction through energy harvesting in vortex-induced vibrations
(2021-03-20) Bastos, Sérvio Túlio Suenai Haramura [UNESP]; De Vasconcellos, Rui Marcos Grombone [UNESP]; Universidade Estadual Paulista (Unesp)
In this work, an identified electrical-mechanical model is implemented to describe complex behavior, such as upper and lower branches, and the piezoelectric coupling to harvest electric power in a 1DOF cylinder exposed to a transverse flow, presenting vortex induced vibration (VIV). A classical Van der Pol model was modified to represent the variations of Strouhal number and aerodynamic damping coefficient in order to represent the experimentally observed upper and lower branches. By comparing the numerical simulation with experiments presented in the literature the proposed model was validated. Then, the effects due to the electrical coupling were analyzed in terms of electrical power generation and the suppression of high amplitude oscillations. Results demonstrate the electrical coupling contributed to reduce the amplitude of oscillation. The results of this research can be helpful in order to design efficient energy harvesters based on VIV and can assist the development of strategies to suppress vibrations.
Effect of Coriolis acceleration on the span-wise vorticity field over a wind-turbine airfoil
(AIAA, 2022-06-30) Rodrigues, Pedro Trombini [UNESP]; Gennaro, Elmer Mateus [UNESP]; Souza, Daniel Sampaio [UNESP]; Universidade Estadual Paulista (Unesp)
The rotation is known to reduce the volume of the region of separated flow on inboard sections of horizontal-axis wind turbine blades. This reduction is frequently attributed to centrifugal pumping. However, recent investigations on the rotational stabilization of leading-edge vortex suggest that the radial transport of vorticity may not be the dominant mechanism limiting the vortex circulation on inboard sections of insect wings. For such low-Reynolds number, the effect of the tangential component of the Coriolis force destroys radial vorticity, limiting the growth of the leading-edge vortex and stabilizing it. However, to the best knowledge of the authors, the contribution of such a phenomenon to the rotational augmentation observed in wind turbines has not been assessed. We employed quasi-3D simulations to investigate the role of the Coriolis acceleration to the balance of span-wise vorticity within the region of separated flow on the upper surface of wind-turbine-blade sections at high angles of attack. The destruction rate of radial vorticity due to Coriolis acceleration was most significant in the free shear layer on the upper boundary of the separated-flow region. Moreover, it is shown that its integrated effect may be comparable to the rate of vorticity flowing in the recirculation region from the boundary layer. Therefore, the mechanism may be relevant to rotational augmentation observed in inboard sections of wind-turbines blades.
Blade Element Momentum simulations using polars extracted from wind-turbine-model experiments
(ABCM, 2021-11-22) Rodrigues, Pedro Trombini [UNESP]; Lemos, Diego Magela; Pagani Júnior, Carlos do Carmo [UNESP]; Sampaio, Daniel Souza [UNESP]; Universidade Estadual Paulista (Unesp)
Due to rotational effects, the observed load of inboard sections of rotary wings is consistently higher than the load predicted based on the two-dimensional aerodynamic behavior of the corresponding airfoil in linear motion. Therefore, engineering methods used to analyze and optimize the aerodynamics of horizontal-axis wind turbines (HAWT) rely on corrections to 2D airfoil data. Since the physics associated with the phenomenon is not fully understood, the correction models have to resort to empirically determined parameters. It is important to stress that a great scattering of the turbine power predictions based on different correction models is observed for conditions of high blade load. We propose a methodology to predict the load on HAWT blades based on the widely applied blade element momentum (BEM) method that does not rely on the correction of 2D polar curves. In the proposed methodology, the force coefficients are stored in the lookup table and consulted by the BEM algorithm, not only as function of the angle of attack but also as function of the chord-to-radius ratio and the local Rossby number. The data of the lookup table is provided by the measurements of the unsteady aerodynamic experiment Phase-VI, coordinated by the United States' National Renewable Energy Laboratory and conducted in a 24.4m × 36.6m wind tunnel in NASA Ames Research Center. Compared to a well accepted correction model, the proposed methodology predict the load radial distribution with greater accuracy for relatively high wind speeds.
Orbital maneuvers for asteroids using genetic algorithm
(IOP Publishing, 2019-10-01) Neves, Guilherme Marcos [UNESP]; Santos, Denilson P. S. [UNESP]; Domingos, Rita de C. [UNESP]; Formiga, Jorge K. S. [UNESP]; Universidade Estadual Paulista (Unesp)
Near Earth objects (NEOs) are comets and asteroids that orbit the vicinity of the Earth. The scientific interest in comets and asteroids is due in large part to their status as remnants remaining relatively unchanged from the process of forming the solar system some 4.6 billion years ago, and some asteroids are made of precious metals such as platinum. Genetic algorithms are a particular class of evolutionary algorithms that use techniques inspired by evolutionary biology such as heredity, mutation, natural selection, and recombination. They can also be defined as global optimization algorithms and model a solution to a specific problem. This method provides a way to find solutions to problems that would be unlikely to be analytically feasible. The present work aims to use this method to optimize the consumption of fuel in Rendezvous maneuvers in interplanetary missions in a context where one wishes to send a probe to an asteroid to study it.
Tension force in nanosatellite tethers systems
(IOP Publishing, 2019-11) Moia, Guilherme Parreira [UNESP]; Santos, Denilson P. S. [UNESP]; Formiga, Jorge K. S. [UNESP]; Universidade Estadual Paulista (Unesp)
The use of innovative technologies in space missions has evolved considerably in the last decade. The use of large cables in space structures to connect spacecrafts and satellites with the goal to minimize cost of missions created a new field to be explored. A brief explanation will be considered about papers related to the equilibrium and stability of the movement of space systems connected by cables, known as Tether Systems. It will be presented the mathematical formulation for the system formed by two point masses connected by a tether in the central force field, in a Keplerian movement. The Lagrangian formulation was used to describe the rotational movement of the dumbbell-like system. Results of system behavior, tension and kinetic energy will be presented for two different situations, considering equal masses and different masses.
Characterization of grazing bifurcation in airfoils with control surface freeplay nonlinearity
(European Assoc Structural Dynamics, 2014-01-01) Vasconcellos, Rui M. G. [UNESP]; Abdelkefi, Abdessattar; Marques, Flavio D.; Hajj, Muhammad R.; Universidade Estadual Paulista (Unesp); Virginia Tech; Universidade de São Paulo (USP)
A variety of nonlinear features is obtained from aeroelastic systems with discontinuous nonlinearity motivates investigations that may support future applications in controls design, flutter prediction problems, and energy harvesting exploration. The freeplay nonlinearity leads to bifurcations and abrupt response changes which can result in undesirable or catastrophic responses. Grazing bifurcations of limit cycles are one of the most commonly found discontinuity-induced bifurcations (DIBs) and are caused by a limit cycle that becomes tangent to the discontinuity boundary of the available piecewise-smooth function. The abrupt transition from periodic to aperiodic is directly related with the discontinuous nature of freeplay nonlinearity. In fact, recent studies in different areas discussed the presence of grazing bifurcations and the associated behavior changes. These abrupt transitions caused by grazing bifurcations are different from the well-known routes to chaos. In this work, a nonlinear analysis based on modern methods of nonlinear dynamics, such as power spectra and phase portraits is performed to characterize the sudden transitions in a three-degree of freedom aeroelastic system with freeplay nonlinearity in the flap degree of freedom. The results show that the main transition is due to a grazing bifurcation.
Influence of structural nonlinearities in stall-induced aeroelastic response of pitching airfoils
(European Assoc Structural Dynamics, 2014-01-01) Pereira, Daniel A.; Vasconcellos, Rui M. G. [UNESP]; Marques, Flávio D.; Universidade de São Paulo (USP); Universidade Estadual Paulista (Unesp)
Stall-induced vibrations are a relevant aeroelastic problem for very flexible aero-structures. Helicopter blades, wind turbines, or other rotating components are severely inflicted to vibrate in stall condition during each revolution of its rotor. Despite a significant effort to model the aerodynamics associated to the stall phenomena, non-linear aeroelastic behavior prediction and analysis in such flow regime remain formidable challenges. Another source of nonlinearity with influence to aeroelastic response may be associated to structural dynamics. The combination of both separated flow aerodynamic and structural nonlinearities lead to complex dynamics, for instance, bifurcations and chaos. The purpose of this work is to present the analysis of stall-induced vibrations of an airfoil in pitching when concentrated nonlinearities are associated to its structural dynamics. Limit cycles oscillations at higher angles of attach and complex non-linear features are analyzed for different nonlinear models for concentrated restoring pitching moment. The pitching-only typical section dynamics is coupled with an unsteady aerodynamic model based on Beddoes-Leishmann semi-empirical approach to produce the proper framework for gathering time series of aeroelastic responses. The analyses are performed by checking the content of the aeroelastic responses prior and after limit cycle oscillations occur. Evolutions on limit cycles amplitudes are used to reveal bifurcation points, thereby providing important information to assess, characterize, and qualify the nonlinear behavior associated with combinations of different forms to represent concentrated pitching spring of the typical section.
Compressible modes in a square lid-driven cavity
(Elsevier B.V., 2015-07-01) Bergamo, Leandro Fernandes; Gennaro, Elmer Mateus [UNESP]; Theofilis, Vassilis; Medeiros, Marcello Augusto Faraco; Universidade de São Paulo (USP); Universidade Estadual Paulista (Unesp); Universidad Politécnica de Madrid
This paper studies the effect of compressibility on the linear stability of a two-dimensional lid-driven cavity flow in the subsonic regime. The base flow is generated by high fidelity direct numerical simulation and a biglobal mode instability analysis is carried out by a matrix forming approach. The eigenvalue problem is discretized by high-order finite differences and Arnoldi algorithm is used to reduce the size of the problem. The solution procedure uses sparse matrix techniques. Influence of Mach number on the modes known from incompressible calculations is presented, showing that compressibility has a stabilizing effect. New modes that appear only for compressible flows are presented and their relationship with duct acoustics is investigated.

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