Bruno A. Roccia

Modified Unsteady Vortex-Lattice Method to Study Flapping Wings in Hover Flight

A numerical-simulation tool is developed that is well suited for modeling the unsteady nonlinear aerodynamics of flying insects and small birds as well as biologically inspired flapping-wing micro air vehicles. The present numerical model is an extension of the widely used three-dimensional general unsteady vortex-lattice model and provides an attractive compromise between computational cost and fidelity. Moreover, it is ideally suited to be combined with computational structural dynamics to provide aeroelastic analyses. The present numerical results for a twisting, flapping wing with neither leading-edge nor wing-tip separations are in close agreement with the results obtained in previous studies with the Euler equations and a vortex-lattice method. The present results for unsteady lift, mean lift, and frequency content of the force are in good agreement with experimental data for the robofly apparatus. The actual wing motion of a hovering Drosophila is used to compute the flowfield and predict the lift ...

Development of a Kinematical Model to Study the Aerodynamics of Flapping-Wings

The kinematics that characterizes the “natural flight” of insects is quite complex. It involves simultaneous rotations, oscillations and significant changes in the angle of attack. All this permits the wings to follow an extremely complex trajectory producing different flight mechanisms that are efficient at low to moderate Reynolds numbers. Some of these mechanisms, such as the delayed stall, the additional circulation generated by the rotation of the wing, and the wake capture amongst others, offer unique advantages with respect to the well-known fixed-wing aerial vehicles. Such advantages are better lift and thrust generation without the need to increase weight. This paper presents a general kinematical model that permits studying the movements of the wings of a scale robot of a house fly, the ‘RoboFly’, built at UC Berkeley, USA. Additionally, this general kinematical model allows studying the kinematics of the wings of a flying insect considering both the body orientation and the stroke plane orientation of the creature in the 3D space. This work provides a nexus between the descriptive language used by biologists and the predictive language used by engineers. This connection between scientific disciplines allows one to study and characterize the principal kinematic parameters that intervene in a stroke cycle, as well as to determine how these variables modify the trajectories of the material points on the wings.

Computational Dynamics of Flapping Wings in Hover Flight: A Co-Simulation Strategy

A co-simulation strategy for modeling the unsteady dynamics of flying insects and small birds as well as biologically inspired flapping-wing micro-air-vehicles is developed in this work. In particu...

A Numerical Model to Study the Nonlinear and Unsteady Aerodynamics of Bioinspired Morphing-Wing Concepts

In the present paper, a numerical model to study the nonlinear and unsteady aerodynamics of morphing-wing concepts inspired by bird flight is developed. The model includes: i) a wing topology inspired by gull wings; ii) a kinematical model to describe the process of wing adaptation based on one mechanism observed in the flight of gulls (folding-wing approach); and iii) a version of the unsteady vortex-lattice methods (UVLM) that allows taking nonlinear and unsteady aerodynamic phenomena into account. The model was specially developed to study the aerodynamic behavior during wing adaptation. A simulation for a twisting-flapping wing was performed in order to validate the numerical model. The present results are in close agreement with those obtained in previous studies based on the Euler equations, but required much less execution time. The numerical simulations of a bioinspired morphing wing showed the strong dependence between the prescribed kinematics and the aerodynamic characteristics, which evidences the importance of studying the process of wing adaptation. UVLM is shown to be ideal for preliminary analysis of bioinspired morphing wings.

A Computational Aeroelastic Framework for Studying Non-conventional Aeronautical Systems

A computational co-simulation framework to study the aeroelastic behavior of a variety of aeronautical systems characterized by highly flexible structures undergoing complex motions in space and immersed in a low-subsonic flow is presented. The authors combine a non-linear aerodynamic model based on an extended version of the unsteady vortex-lattice method with a non-linear 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 multi-body systems, such as models based on rigid-body dynamics, assumed-modes techniques, and finite-element methods. The governing equations are numerically integrated in the time domain to obtain the structural response and the consistent flowfield around it. The integration is based on the fourth-order predictor-corrector method of Hamming. The findings are found to capture known non-linear behavior of these non-conventional flight systems. The developed framework should be relevant for conducting aeroelastic studies on a wide variety of aeronautical systems such as: micro-air-vehicles (MAVs) inspired by biology, morphing wings, and joined-wing aircrafts, among others.