Two kinds of methods of explaining the physical mechanism of the Magnus effect are compared with each other and fully discussed. The first method uses Bernoulli's theorem and the fluid velocity difference between both sides of the body. The second one is based on the momentum theorem which relates the lift force with the fluid acceleration perpendicular to the uniform flow direction, which is caused by the asymmetry of separation points. It is shown that the latter method is preferable because it can be strictly applied to the real flow field containing both the rotational and the irrotational flow regions.
A numerical simulation method taking into account both aerodynamics and flight dynamics has been developed to simulate the flight of a low speed flying object, where it undergoes unsteady deformation. This method can also be applied to simulate the unsteady motion of small vehicles such as micro air vehicles (MAV). In the present study, we take up a bird and demonstrate its flight in the air. In particular the effect of fluid forces on the bird's flying motion is examined in detail, based on CFD×CFD: Computational Fluid Dynamics (CFD) and Computational Flight Dynamics. It is found from simulated results that this bird can generate lift and thrust enough to fly by flapping its wing. In addition, it can make a level flight by adjusting its oscillation frequency. Thus, the present method is promising to study the aerodynamics and flight dynamics of a moving object with its shape morphing.
The purpose of this study is to suppress edge tone generated by jet-wedge interaction. A passive control was achieved by means of a pair of tabs attached to the center of the nozzle exit, and revealed that the edge tone is reduced by 5dB. Velocity measurement was also conducted to clarify the suppression mechanism by use of sound wave excitation. The excitation was synchronized with the self-oscillating flow for selective sampling, so that hot-wire measurement directly provide the phase averaged flow fields. It was revealed that the velocity is weakened at the position corresponding to tabs, and the spanwise uniformity of the jet is broken. In addition periodic fluctuation of vorticity is reduced by tabs. These phenomena weaken feedback loop, as a result the edge tone was suppressed.
In this paper the variation of cushion pressure is investigated theoretically to achieve comfortable riding of SES. A simpler and practical control method is proposed to control cushion pressure changes arising from pumping phenomenon that appears in SES cruising over the waves. Cushion pressure is controlled by varying the discharge height of the vertical nozzle. In this method the nozzle height (hover height) is kept constant according with the motion of the craft. As the result of investigations, cushion pressures are successfully controlled by the proposed method. In addition, it is shown that the pressure variation depends not only hover height but also on rate of change of cushion volume. Therefore it is also necessary to consider phase difference between the motion of models and the vertical displacement of nozzles.
This paper presents coupled thermal-electrical analysis of transient temperature distribution in carbon fibre composites (CFRP) exposed to simulated lightning current to understand the damage behaviour due to lightening strike. Thermal and electrical properties of CFRP were evaluated for each direction of the unidirectional composites. The thermal decomposition behaviour was also estimated from thermo-gravimetric analysis results. Based on the experimental results and preliminary analysis results, the electrical and thermal boundary conditions were discussed in detail. The numerical results are directly compared with the experimental results, and the damage mechanisms of CFRP exposed to impulse current were considered. As a result, it was inferred that the delamination of CFRP was mainly caused by the decomposition of matrix resin, and the fibres were broken by the sublimation due to high Joule heat generation.