To verify the effects caused by small objects attached to the airframe, novel wind tunnel test was conducted. Measurement accuracy of aerodynamic parameters depend on measurement period, equipment used etc., but by turning the portion of the airframe where small objects are attached by 180 degree, error cause such as drift etc. are completely eliminated. Flight path calculation using the parameters obtained by this wind tunnel test and the one by the real firing coincides remarkably. The method appeared in this paper is very suitable to obtain the parameters caused by small objects on airframe.
The flow induced around a sphere with a uniform temperature in a gas with a uniform temperature gradient is investigated for small KNUDSEN number on the basis of the linearized BOLTZMANN-KROOK-WELANDER equation. The velocity field is obtained up to the order of the KNUDSEN number cubed. The thermal force acting on the sphere is also obtained up to the third order, and the relation between its direction and the KNUDSEN number is discussed.
A nonlinear analysis is carried out for oscillations of an inviscid, incompressible fluid in a two-dimensional, rigid, open container which is subjected to horizontal, vertical or pitching oscillation. First, brief review is made on the sloshing in horizontal oscillation and also that in vertical oscillation. Secondly, the sloshing inpitching oscillation is treated with in more detail: Governing equations are formulated as a nonlinear initial-boundary value problem with reference to the coordinate system fixed to the container assuming the liquid motion to be irrotational. Then, pseudo-variational principle is introduced for the problem. A finite element approximation is made by the use of the variational principle. Due to the nonlinearity of the problem, incremental method is employed. The FEM equations thus derived are integrated with respect to time step by step by the trapezoidal rule. The numerical results obtained by the present method were compared with the solutions of the linear theory and the experimental data. The nonlinear characteristics of the fluid motion have been obtained.
The fan noise characteristics of a turbofan engine and fan noise abatement technology have been studied by the authors. The study was concentrated on the theoretical analysis of the spinning mode propagating from the rotating fan of a high bypass-ratio turbofan engine and the practical technology to abate the fan noise and the practical technology to abate the fan noise acoustic linings on the engine inlet duct and the fan cowl. Through the above study, the procedures to determine the optimum impedance and necessary dimensions on the acoustic treatment for the reduction of the fan rotating noise under given conditions were obtained. Following those procedures, acoustically lined ducts were designed, manufactured and installed on a high bypass-ratio turbofan engine for a series of noise measuring tests. As a result, it was revealed that the acoustically lined duct attached to the engine inlet is effective for the reduction of the noise level so long as it is designed to the optimum impedance value for maximizing the attenuation rate of the spinning mode, and that some portions of the spinning mode can be cut off even by the solid wall duct, though this was not realized in the simulation test using a plane wave source.
To analyse the plastic large deformation problems of cylindrical shell by the incremental method, we develope the pseudo-equilibrium type element based on the principle of modified complementary virtual work. Then, we examine the developing process of plastic deformation and stress distributions when a cylinder is subjected to an axial compression force (one of the complicated structural problems involving plastic large deformation, variable boundaries and dynamic effects). Here we treat this problem as the static one and calculate the two cases of boundaries (1) simple supports (2) clamped supports. In the sample, the finite element solutions are performed for L/R=4, R/T=20, T=1mm and 2024-T 4 Al-Alloy material. But it is easy to employ any type of strain hardening rules and to extend the above method to the dynamic problems. As a result, we find that, unlike the elastic solution, one half-wave in the case of simple supports is formed at the end and outwards from the original generating line of the shell. It coincides with the experimental facts.
In designing an advanced flight control system, parameter uncertainties and state inaccessibilities in aircraft include serious problems. Two different adaptive observer schemes to improve the convergence characteristics were proposed by the authors to estimate the state variables and parameters of an unknown linear time-invariant plant from its input-output data. In this paper, the authors proposed the computational algorithm which appears to combine the advantage of the two types of observers described above, and an adaptive controller is designed to generate a control input by a differentiator-free controller such that the output of the plant evolves asymptotically towards that of a given model. Simulation studies for designing the flight controller of VTOL aircraft are presented to demonstrate the effectiveness of the proposed scheme.