The aerodynamics of flying birds and insects plays a crucial role in the domain of aeronautical engineering. The energy-efficient construction of winglets for airplanes, the formation flight of tactical aircraft or the drone engineering or military applications are inspired by birds. This holds also for flow and structure simulation of flapping wing motion, taking the unsteady aerodynamics and corresponding wing deformations into account at high flow velocities and flapping frequencies.

This book provides readers from academia and industry with an up-to-date overview of important advances in the field, dealing with such fundamental fluid mechanics problems as nonlinear transport phenomena and optimal control of mixing at the micro- and nanoscale. The editors provide both in-depth knowledge of the topic as well as vast experience in guiding an expert team of authors. The review style articles offer a coherent view of the micromixing methods, resulting in a much-needed synopsis of the theoretical models needed to direct experimental research and establish engineering principles for future applications. Since these processes are governed by nonlinear phenomena, this book will appeal to readers from both communities: fluid mechanics and nonlinear dynamics.

This book includes the proceedings of the Sustaining Tomorrow 2020 symposium and summit which bring together research from experts in academia, industry, and policy arenas to uncover the challenges and to forge solutions to sustain tomorrow. To sustain tomorrow, we need to continuously make headway in Agriculture, Engineering, Energy, Environment, Economics, Water, among other necessities. This book disseminates the most recent advances in these fields and promotes collaborations to maximize opportunities for innovative solutions. Though primarily intended to offer an update for experts and researchers in the field, this book is equally useful as a valuable educational tool for relevant undergraduate and graduate courses. Key aspects covered include the better and more responsible engineering and management of energy conversion and conservation processes, the furthering of renewable energy technologies, improvements in water-agriculture nexus and energy-environment-economics relationship, and endorsing education, implementation, and evaluation of all-embracing sustainability.

The study investigated the role of formation time, Reynolds Number, and non-dimensional frequency number, the three most significant parameters in the dynamics of vortex rings, in the interaction between co-axial and co-rotating vortex rings and in the ring behaviors of merging and leapfrogging. To generate and investigate vortex rings with the required characteristics, two laminar vortex rings were generated consecutively from a piston-cylinder apparatus such that the rings propagated in the same direction and that the spatial separation between them decreased until they began merging. Using digital particle image velocimetry to measure the flow fields as well as the trajectory and circulation of the individual rings, a series of experiments were conducted at three formation times, with the experiments at each formation time repeated at different Reynolds Numbers, and the experiments at each Reynolds Number in turn repeated at different non-dimensional frequency numbers. The results indicate that at low Reynolds Numbers, the total circulation in the flow is relatively constant before and after the rings merge. However, at high Reynolds Numbers, the total circulation begins rapidly decreasing upon the contact of two vortex ring cores, indicating a transition to a turbulent vortex ring during merging, before stabilizing at a lower level, indicating that the merged ring has transitioned back to a laminar vortex ring after shedding some circulation.