Computational Aeroelasticity of Flying Robots with Flexible Wings

A computational co‐simulation framework for flying robots with flexible wings is presented. The authors combine a nonlinear aerodynamic model based on an extended version of the unsteady vortex‐lattice method with a nonlinear structural model based on a segregated formulation of Lagrange’s equations obtained with the Floating Frame of Reference formalism. The structural model construction allows for hybrid combinations of different models typically used with multibody systems such as models based on rigid‐body dynamics, assumed‐modes techniques, and finite‐element methods. The aerodynamic model includes a simulation of leading‐edge separation for large angles of attack. The governing differential‐algebraic equations are solved simultaneously and interactively to obtain the structural response and the flow in the time domain. The integration is based on the fourth‐order predictor‐corrector method of Hamming with a procedure to stabilize the iteration. The findings are found to capture known nonlinear behavior of flapping-wing systems. The developed framework should be relevant for conducting aeroelastic studies on a wide variety of air vehicle systems

Aerodinámica y dinámica del vuelo de alas batientes

En este trabajo se presenta una herramienta de simulación numérica que permite estudiar la aerodinámica no-estacionaria y la dinámica no-lineal asociada al vuelo natural de insectos y aves pequeñas. El modelo aerodinámico utilizado es una versión modificada de la versión 3D del “unsteady vortex lattice method” (UVLM), una generalización del conocido “vortex lattice method”, ampliamente utilizado en flujos incompresibles y estacionarios. La dinámica asociada al insecto se modela mediante un modelo estructural multicuerpo hibrido del insecto completo (cabeza, tórax, abdomen y alas). El desarrollo del modelo está basado en la formulación de Lagrange con coordenadas generalizadas redundantes. Para lograr generalidad y versatilidad en la herramienta desarrollada, se modificó un modelo cinemático desarrollado previamente por los autores de este trabajo para incluir diferentes patrones de deformación sobre el ala (torsión, flexión y ambos efectos combinados). Las alas tienen movimientos prescriptos respecto del cuerpo central, se dice que las alas son cinemáticamente conducidas. La integración numérica de todas las ecuaciones gobernantes, que son diferenciales algebraicas, es realizada simultáneamente e interactivamente en el dominio del tiempo. El esquema de integración usado acopla un método predictor corrector de cuarto orden, el método modificado de Hamming, con un procedimiento de estabilización para las ecuaciones de movimiento resultantes.Fil: Roccia, Bruno A. Universidad Nacional de Río Cuarto. Facultad de Ingeniería; Argentina.Fil: Roccia, Bruno A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Estructuras; Argentina.Fil: Preidikman, Sergio. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Estructuras; Argentina.Fil: Preidikman, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Massa, Julio C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Estructuras; Argentina.Fil: Mook, Dean T. Virginia Polytechnic Institute and State University Blacksburg VA. Department of Engineering Sciences and Mechanics; Estados Unidos.Ingeniería Mecánic

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

An Improved Vortex Method for Closed Surfaces

An improved vortex method by carefully considering redundancy in application to closed surfaces has been worked out to compute aerodynamic characteristics of known configurations. It has been shown that application of Newmann Boundary condition for closed surfaces gives rise to a singularity in aerodynamic matrix which is removed by eliminating the redundancy in the set of equations

Note on the redundancy in the discrete-vortex method for closed bodies 13; 13;

The redundancy that occurs when vortex-lattice methods are applied to closed bodies is discussed. Two procedures to solve the no-penetration condition are explained and illustrated by means of a simple example in which the flow over a sphere is modeled with a very crude mesh. The mesh is refined, and it is shown that the procedure produces an accurate approximation to the exact solution

Redundancy in the discrete-vortex method for closed bodies

The redundancy that occurs when vortex-lattice methods are applied to closed bodies is discussed. The solution to the no-penetration condition in terms of the circulations around the closed loops encircling the elements of the lattice is not unique, but the circulations around the individual vortex segments of the lattice are. Two procedures to solve the no-penetration condition are explained and illustrated by means of a simple example in which the flow over a sphere is modeled with a very crude mesh. Then the mesh is refined, and it is shown that the procedure produces an accurate approximation to the exact solution. (AIAA

Nonlinear oscillations

Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses si