↓ General research interests ↓
Energy-efficient vehicles. Currently: aerial vehicles with cycloidal rotors. Formerly: trucks and cars. Tools: computational fluid dynamics, multibody dynamics, C++ and Linux. I prefer open-source software.
↓ Short project intro ↓
For my Humboldt project I aim to design a highly efficient helicopter-like aircraft. To find its best configuration, I will conduct coupled aerodynamic-structural simulations within an optimization process.
↓ media coverage ↓
Article about my research stay from the university's website: Alternative zu Helikopter: ein Cyclocopter für Spezialfälle , English translation (pdf): Alternative to helicopter: a cyclocopter for special cases, traduction en Français(pdf): Alternative à l'hélicoptère : un cyclocoptère pour les cas particuliers.
↓ A longer intro ↓
Taken from the abstract I prepared for a Humboldt Network Meeting.
SUMMARY (project, briefly)
My goal is to optimize the energy efficiency of a novel aircraft propulsion system. It comes from an idea which originated in the early 1900s and which was never brought to commercialization. It is usually referred to by the name of “cycloidal rotor” and can be powered by electric motors. I will describe it in more details in the next paragraph. To attain my goal, I will develop and rely on methodologies for the analysis of the mechanics and aerodynamics of these rotors. With the help of these methodologies, I will assess the power requirements of the rotor when carrying cargo and passengers and evaluate the ratios of required power to carried weight. I will enrich my analyses by considering a flying vehicle configuration which makes use of the optimized rotors. I will then build a small prototype to demonstrate the ability to fly and confirm the results obtained from the numerical simulations. Eventual applications of the technology range from lightweight single-person sport aircraft to larger heavy-duty aerial cranes.
CYCLOIDAL ROTORS (what are they?)
The propulsion system commonly referred to as the cycloidal rotor is not known by many people. Similarly to helicopter rotors and propellers, cycloidal rotors have a set of aerodynamic wings (blades) which rotate around a common central point. However, they have the particularity of having their long (span) axis parallel to the rotation axis. Such an alignment is usually seen in squirrel cage fans, water turbines, paddle wheels, and vertical axis wind turbines. In most known cycloidal rotor implementations, the blades are clamped at their tips by a mechanism which transfers a constant rotation velocity and a variable pitch angle to each blade. The combination of the rotation and pitching motions produces a resulting force which can be directed anywhere normal to the rotation axis. The latter is a considerable advantage for flight stability. The geometry of cycloidal rotors also brings its blades in contact with the same air elements twice. This presents a challenge for the design of proper pitch control mechanisms during the second contact with the flow. There, the influence of the vortices created by the first contact is considerable and hard to understand.
SOFTWARE (favoring open source)
The principal tools I use are numerical simulations of the flow field on and around the propulsion system. I set up these simulations using both the Multibody Dynamics (MBD) and the Computational Fluid Dynamics (CFD) methodologies. They are implemented into open source software which constitute the principal tools that I rely on for my research. For the former I specifically rely on MBDyn, which is developed by my previous research team at Politecnico di Milano. It allows to model the aerodynamics of the blades of the cycloidal rotor using data tables and is consequently able to yield results in a very short period of time. I can further model the mechanics of a complete aircraft along with control systems which allow to perform virtual flight testing. Furthermore, it allows to implement the rotor blades and other parts of an aircraft as flexible structural objects. For the later I rely on OpenFOAM, which is an established open source code for CFD analyses. It provides tools to solve an extensive number of flow types. It is equipped to model complex rotating machinery and turbulence. It also permits a good analysis of the power requirements and lifting forces of a rotor. Although I rely on various software to conduct my research, MBDyn and OpenFOAM are the most important ones. They can also be coupled to work together in order to provide high precision aerodynamic rotorcraft modeling with structural deformations.
OPTIMIZATION (achieving energy efficiency)
The objective is to find operating conditions where the power required to provide lifting forces is as small as possible in proportion to the weight that can be carried. In order to better simulate the advantages of diverse configurations having various rotor sizes and rotating velocities, I run a CFD simulation which numerically solves the flow field up to as close as possible to the walls of the blades. This allows to better model the changes in the behavior of the flow that are caused by small changes in velocity and turbulence content when working at various regimes. Such changes can have drastic effects on the resulting flight dynamics. Once I obtain a satisfactory model, I will test different rotor configurations within a parametric study aimed at increasing the energy efficiency. The parameters which I intend to explore are: the dimensions of the planar surfaces of the blades, the shape of their cross sections, and their distance from the rotation axis; the position of the pivoting axis of the blades and their pitching function; the number of blades; the material construction of the blades; and, the main rotation velocity. If time permits, I will study the impact of the deformation of the flexible structures on the energy efficiency of the rotor.
MY HOST (IAG, Universität Stuttgart)
The Institut für Aerodynamik und Gasdynamik has a considerably large team of researchers who specialize in the study of fluid dynamics. As such, many of them conduct aerodynamic analyses on ground vehicles, fixed-wing aircraft, helicopters, and wind turbines. They develop diverse CFD tools and have extensive experience with the proper arrangement of such simulations. My interaction with the team and access to their platforms allow me to quickly solve problems related to the numerical study of the flow on cycloidal rotors.