This paper presents new formulation of equations of motion for chained rigid bodies. In this method, components of matrix or vector of equations of motion are calculated recursively. This reduces much effort for calculation of motion of chained rigid bodies. Calculation can be done effectively and quickly. Moreover, this new formulation does not require much memory even if chained rigid bodies system has many bodies. Computer simulations are given to demonstrate the effectiveness of this formulation.
This paper investigates the aerodynamic response of a thin airfoil flying over and in proximity to a wavy wall surface which moves in the same direction as free stream but with a different velocity. Integral equation method relating the pressure on boundaries to downwash velocity is adopted for formulation, based on inviscid and small perturbation flow. Supposing the wall to be sinusoidal and the airfoil to be a flat plate at zero incidence, numerical calculations are made with a set of important parameters as airfoil height from the wall, wave length of wall surface, and the wall velocity. The influence of such parameters on the aerodynamic coefficients is divided into two parts, “First-order Ground Effect” and “Second-order Ground Effect” The latter is discussed in detail through the solution of Kemp-type gust. Numerical results show that the wave length and the traveling velocity of wall within a certain range have a great influence on the “Second-order Ground Effect”, with proximity to the ground.
Recently, upwind differencing schemes have become very popular, especially when discontinuities exist in the solutions. In the present paper, an application of upwind differencing scheme to the magnetogasdynamic equations with a flux vector splitting method is described. We have approximately splitted fluxes by using magneto-Mach number in place of Mach number. The new upwind scheme has been extended to a generalized coordinate system by finite volume method. In the formulation, the problem of ∇·B=0 has been overcome by the integration of induction equation on the control cell surfaces. Several examples show good characteristics of the present method.
The present paper deals with the failure analyses of symmetric angle-ply laminated composites with different number of stacking layers. The problem is investigated under a uniform axial extension through the application of nonlinear constitutive equations, which are based on the three-dimensional Ramberg-Osgood formulas. A quasi-three-dimensional finite element method with a four-node rectangular element is utilized in analyses. The post-failure state is analyzed by taking into account the change of material properties due to initial failure evaluated by the maximum stress criterion. Numerical calculation is made for [45°4/-45°4]s (four layers) and [45°/-45°/45°/-45°]s (eight layers) CFRP symmetric angle-ply laminates. The ultimate strengths predicted by the present method are in good agreement with the experimental results for 45° four- and eight-layered CFRP laminates. Basing upon the propagation of the failure, we propose the failure modes of the four- and eight-layered laminates. The proposed failure modes agree with the experimental failure modes. We also investigate the strength of laminates versus angleply orientations.
The optimization of a wing structure with a gust load alleviation (GLA) system is presented as a method to evaluate the weight reduction of the wing structure. A wing spar is descretized into a set of beam elements using the Finite Element Method. The GLA system controls an aileron deflection using the feedback of an wing accelerometer signal. Goal programming formulation is used to find optimum solutions. A reference model is the optimized structure without the GLA system. The quantity of the weight reduction is estimated with the structural optimization of the reference model with the GLA system. In addition, an wing stress level resulting from the GLA system failure and the aileron deflection angle for active control are calculated.
This paper describes a ground verification method for a high-accuracy on-board antenna-drive control system which compensates the antenna's pointing error. A ground test system for this control system was investigated to predict the control performance in orbit. A laser beam was used instead of the RF beacon signal, and an RF converter which simulates the RF characteristics of the antenna system has been composed in order to realize the closed loop test system. The ground test system was constructed using a vacuum chamber to simulate the thermal vacuum environment. Gravity compensation was applied to the antenna pointing mechanism and 1.6×10-4G (G: acceleration of gravity) environment was obtained by adjusting the suspension point location. Control performance of the antenna-drive control system which is planned for the launch on ETS-VI spacecraft was evaluated by this ground test system.
The current view is that airships to be used for transportation would be promising only if they have considerably big scale. But the present author has some doubts. The reason is that numbers of ground crew and airport size expands considerably with airship-scale and that advertisement-income is not taken into account. Only the last factor is considered in this paper. It is found that the advertisement-income would exceed the transportation expenditure for airship of medium to small size. This result will encourage development of airship for commuter transport.