Passive damping augmentation is one of attractive methods for vibration suppression to various kinds of structures because it is definitely stable and generally simple. Using viscous adhesive indicated a remarkable effect to the vibration suppression in the practical application to a satellite. In this paper, mathematical model of thin viscous adhesive layer using non-linear elements has been proposed. In this model, the characteristics of elements are correlated with non-linear internal phenomena of polymer. The simulation results using this proposal model are good agreement with experimental ones.

View full abstract

In this study, high efficient design tool is developed with several informatics approaches for Multidisciplinary Design Optimization (MDO) and knowledge discovery of supersonic wing design. In this design, Multi-Objective Genetic Algorithm (MOGA) is applied as an optimizer, while Kriging model is also used to reduce computational cost. To obtain the information of the design space, functional ANalysis Of VAriance (ANOVA) and Parallel Coordinate Plot (PCP) is applied. For Kriging model construction, 107 sample points are evaluated. This tool is applied to the multidisciplinary design problem of supersonic wing. The objective functions are to maximize lift to drag ratio and to minimize sonic boom intensity at supersonic cruise, and to minimize wing weight. According to the results, there are trade-off relationships among three objective functions. The ANOVA results indicate that the cambers of the wing section at the root and the kink have an influence on the lift to drag ratio, the inner wing sweep back angle affects the sonic boom intensity, and the camber of wing section at the kink and aspect ratio affect the wing weight. The design space information could be visualized quantitatively from the sampling results with PCP technique. Since the design space exploration using MOGA is carried out based on Kriging surrogate models, the proposed MDO process is effective in terms of computational cost.

View full abstract

The plasma plume of a 1-MW-class quasi-steady magnetoplasmadynamic (MPD) arcjet is studied to reveal the plume plasma fluctuations in a downstream plume region (150–900mm away from the MPD arcjet). By using a double probe and a time-of-flight method, the averaged velocity distribution along the centerline of the plasma plume is found to be almost constant (∼38km/s), and the average ion saturation current is inversely proportional to the square of the distance from the MPD arcjet. The power spectrum density (PSD) of the ion saturation current is proportional to 1/f ^1.6 (f : frequency) in 50–200kHz range and it is proportional to 1/f ^2.6 above 200kHz. However, fluctuations are dominant in the lower frequency region of 50kHz, where PSD vs. f  curve is flat. The spectrum analysis of the fluctuations shows that the MPD arcjet plume in the downstream region is isotropic turbulent flow.

View full abstract

A decentralized control of an air traffic flow on an oceanic route is discussed. This study aims to clarify a fundamental strategy for unidirectional air traffic flow control. It is assumed that the decentralized control is made using airborne surveillance systems. The separation control between aircraft is made by turning, and 3 types of surveillance are compared: foreside surveillance, omnidirectional surveillance, and extended area omnidirectional surveillance. Through the numerical simulation, where an aircraft merges into the traffic flow, it has been clarified that the separation control by turning always stabilizes the traffic flow. The traffic flow formation is also numerically simulated by giving each aircraft random initial position. The numerical results have revealed that the aircraft control by foreside surveillance leads some aircraft into dead lock states. The aircraft control using the omnidirectional surveillance can avoid such unfavorable situations. The aircraft control by the extended area omnidirectional surveillance can achieve the flow formation with considerably improving safety and pilot workload.

View full abstract