The paper provides a brief introduction to the near-wall problem of LES and how it can be solved through modeling of the near-wall turbulence. The distinctions and key differences between different approaches are emphasized, both in terms of fidelity (LES, wall-modeled LES, and DES) and in terms of different wall-modeled LES approaches (hybrid LES/RANS and wall-stress-models). The focus is on approaches that model the wall-stress directly, i.e., methods for which the LES equations are formally solved all the way down to the wall. Progress over the last decade is reviewed, and the most important and promising directions for future research are discussed.

This paper describes the present state of research and development for civil use autonomous unmanned aircraft. In particular, the history of civil use UAVs, the research and development in the world and in Japan, and the subjects and prospects for control and operation systems of civil use autonomous UAVs are described.

To fabricate a semiactive type of damper that is comparatively compact and has low mechanical loss, the author developed an electromagnetic damper using a brushless direct drive DC motor. The damper comprises a ball screw mechanism and a brushless direct drive DC motor that acts as a generator. The motor consists of a rotor and a three-phase stator, and it is installed at the tip of the screw shaft. The lack of contact between the rotor and stator is an advantage. When a linear motion is converted into a rotational motion by the ball screw mechanism, the rotor is rotated, and electrical driving power is generated by electromagnetic induction. The damping effect of each phase is caused by kinetic energy dissipation by the electrical resistances connected to each terminal of coils. In this study, a test damper is fabricated, and theories of resisting force and rise time are introduced. Performance tests are carried out to confirm the theories and the dynamic properties of the damper for two winding configurations, and the experimental results are compared with the theoretical results. The damping effect is greatly generated and smoothly, but saturated in high frequency range, and switched quickly by SSR. It is possible to make the damper more efficient, compact, and sensitive. Finally, theories and the dynamic properties of the damper are confirmed.