General comments:
Scientific Initiation or TCC activities: Undergraduate students interested should contact Dr. Marques at any time by Email (fmarques@sc.usp.br) or telephone (16) 3373 9370. Students from other Institutions/Schools are also welcome.
Master’s and Doctorate degrees: Dr. Marques is certified in the EESC/USP Mechanical Engineering Graduate Program – PPG-AEM (CAPES level 6), thereby enabling them to supervised both Master’s and Doctorate degrees candidates. Those interested can check on the PPG-AEM website for deadlines and registration requirements. Dr. Marques is willing to work with Engineers, Physicists, Mathematicians, or even other speciality from Sciences and Technology fields.
Post-doctoral research: Scholarships or grants are available from PPG-AEM (check criteria from website) and from Projects with other Agencies and Companies/Industry.
Specific topics with immediate (2015/2016) interest on:
TCC (Trabalho de Conclusão de Curso):
1) Shimmy instability in aircraft landing gear (or ground vehicles) … more (in portuguese)
2) Modal analysis (numerical and experimental) of aircraft structures … more (in portuguese)
Scientific initiation:
1) Numerical and experimental assessment of aircraft structural modes and flutter … more
2) Non-linear dynamics in fluid-structure problems … more
Master’s/Doctorate:
1) Stall-Induced vibrations … more
2) Panel flutter prediction and active control … more
Shimmy instability in aircraft landing gear (or ground vehicles)
“Instabilidade shimmy em trens de pouso de aeronaves
(or em veículos terrestres, em geral)“
from: http://grabcad.com/library/nose-landing-gear
O shimmy é um fenômeno que afeta suspensões de veículos terrestres, onde vibrações anormais são observadas nas rodas. Em aeronaves durante a fase de corrida no solo na decolagem ou pouso estão sujeitas ao shimmy, o que pode levar a problemas de instabilidade mais severos. O propósito desse trabalho é modelar um trem de pouso dianteiro genérico para estudar e prever instabilidade shimmy. O estudo também pode ser aplicado para outros tipos de veículos terrestres.
Dentre as habilidades envolvidas neste trabalho tem-se: sistemas dinâmicos e esforços durante a decolagem e pouso. É desejável familiaridade com programas Matlab® ou similares.
Modal analysis (numerical and experimental) of aircraft structures
“Análise modal (numérica e experimental) de estruturas aeronáuticas“
Modal test in a scaled aircraft structure.
Neste projeto, um modelo em escala de uma aeronave completa é usado para identificação e validação dos modos de vibrar na condição de teste no solo. O objetivo é desenvolver uma plataforma de testes e validação de modelos para análise modal de estruturas, aqui tratada no caso de aeronaves. Ensaios modais servirão para ajustar um modelo dinâmico-estrutural da aeronave, podendo este ser pelo método dos elementos finitos.
Dentre as habilidades e afinidades envolvidas neste trabalho tem-se: modelarem via método dos elementos finitos (fica aberto o uso do programa computacional), vibrações mecânicas e análise modal experimental.
Numerical and experimental assessment of aircraft
structural modes and flutter
Aircraft experience important dynamic loading during flight and take-off and landing procedures. Aeroelastic phenomena arise from those conditions with the danger of occurrence of instabilities, for instance, the flutter. To predict such phenomenon it is usual to yield representations based on coupling structural dynamics to unsteady aerodynamics models. Structural dynamics models of complex aircraft structures represent considerable challenge, which are typically dealt by adjusting them with experimental data. As far as the unsteady aerodynamics to predict flutter, frequency domain models are normally considered, thereby allowing to coupled modal-based equations of motion.
Aeroelastic model.
Modal test in a wing structure.
The objective of the research is to develop a complete scheme of flutter prediction framework that consists in the production of numerical and experimental models of a aircraft structure, followed by the adjustment of the numerical representation to account for particular effects only observed from experiments, and the prediction of flutter using traditional aerodynamic strip theory and the doublet-lattice method. By comparing different methodologies for representing the structure and aerodynamics, this research aims to contribute in understanding advantages and drawbacks of each studied case.
Non-linear dynamics in fluid-structure problems
Fluid-structure problems can be understood as those where there are mutual interaction between a flexible body and the flow field surrounding it. Nonlinearities originated from structural or aerodynamic sources can also interfere with fluid-structure dynamics leading to complex behavior.
Wind tunnel experiment with nonlinear airfoil.
This research topic aims to explore basic nonlinear fluid-structure problems using numerical models and experimental investigation. Among possible problems we may have: (i) concentrated structural nonlinearities influence in airfoils responses; (ii) nonlinear wing structure and limit cycle oscillations; (iii) lock-in oscillations of prismatic sections structures (in air and water); (iv) multi-connected nonlinear airfoils dynamics.
Desired skills for this work: dynamic systems, Matlab® or similar programming.
Stall-Induced vibrations
Airfoil SIV at low airspeeds – wind tunnel tests.
Stall-Induced Vibrations (SIV) can be encountered in dynamical systems subjected to fluid-structure interaction loading. Bluff bodies also present aeroelastic SIV due to vortex shedding effects (von Karman vortex sheet). This phenomenon is responsible to bridge aeroelastic oscillations, galloping of transmission cables, vibrations of high towers.
Unsteady airfoils reaching stall angles of incidence may experience aeroelastic oscillations. This condition may occur in highly maneuverable aircraft and commonly affecting rotorcraft and wind turbine blades.
The focus of this research topic is to investigate nonlinear aeroelastic phenomena associated to SIV of airfoils. The following studies are proposed for Master’s and Doctorate degrees research:
- Development of dynamic stall models;
- Experimental assessment of unsteady loads in pitching and heaving airfoils under dynamic stall;
- Nonlinear analysis of aeroelastic time series (numerical and experimental) under SIV.
Panel flutter prediction and active control
Modeling concept for active panel flutter control.
Panel flutter is an aeroelastic instability of plates and/or shell subjected to high speed tangential flows. Typically, at supersonic flow regime this phenomenon can occur at aircraft skin, locally depending of the exposure to the flow.
This proposal research aims to investigate tools for flutter prediction and to the analysis of aeroelastic response of plates and shells towards its active control. As basic hypothesis, the panel instability is nonlinear by nature, where the structure vibrates nonlinearly, but the aerodynamics behaves as a linear system.
Specific research work connected to this issue can be:
- Complete analysis of nonlinear panel responses at flutter or near it, inspecting and detecting bifurcations and chaotic motions.
- Improve aerodynamics to account for nonlinearities that possibly appear from generic panel geometry;
- Use of active composites that can suppress panel flutter.