Proper Orthogonal Decomposition of Flexible Clap and Fling Elastic Motions via High-Speed Deformation Measurements

Many complex unsteady mechanisms are thought to facilitate the high efficiency and agility commonly observed in small biological flyers. One of these, the flexible clap and fling maneuver, has not been extensively studied; an experimental characterization is the focus of this work. The clap–fling mechanism is approximated with a single flexible membrane flapping wing, replacing the symmetry plane between two wings with a splitter plate simulating the pair wing. This produces a complex vibro-impact aeroelastic problem, the deformation resulting from which is measured with a high-speed visual image correlation system. A low-dimensional representation of the ensuing large data set is obtained with proper orthogonal decomposition. The POD modes, and the relative importance of each, can help elucidate crucial mechanisms and relationships within the flapping system, and are computed for various membrane wing structures and flapping frequencies, with or without the presence of the splitter plate.     

Direct Conversion of the Energy of Laser and Fusion Plasma Clouds to Electrical Energy During Expansion in a Magnetic Field

The paper deals with the physical and electrotechnical principles of the promising method of direct conversion of the kinetic energy of an expanding plasma cloud to electrical energy by inductive generation of currents in short–circuited load coils that enclose the plasma and are oriented across the external magnetic field. An analysis of plasma deceleration by a magnetic field and transfer of plasma energy to an inductive load gave a solution of the problem in general form and the dimensionless parameters of the problem that determine the deceleration radius, the coil current, and the theoretical conversion efficiency. The role of the basic physical effects, including parasitic ones (plasma instabilities and Joule heating), influencing the real efficiency is assessed. A comparison of the results with data of experiments with laser–produced plasma clouds on a KI–1 facility and with available numerical results shows that in the optimized version of the method for conversion of inertial confinement fusion energy, a 30% efficiency can be achieved.