Static longitudinal stability of tailless airplane is evaluated theoretically with two methods. One is quasi (or modified)-strip method and the other is a lifting surface theory—DLM. Computation is made on the basis of available data of Northrop XB-35. The both methods agree each other only qualitatively; of course results of DLM should be much more reliable. Allowable limit of longitudinal CG position may be almost comparable with that of conventional airplanes. The airplane efficiency factor, e concerning with induced drag, is computed which is also satisfactory at least for cruising configuration.
The aerodynamic characteristics of a straight wing lying on a diameter in a circular open wind tunnel are studied, where minimum induced drag is assumed. In my previous paper, exact expressions of spanwise optimum lift distribution and minimum induced drag have been obtained from Trefftz plane flow field analysis, where an independent variable transformation and Söhngen's inversion integral formula were used. In this study, an alternative analysis is done, where a comformal mapping and Söhngen's formula are used. The results obtained here are coincident with those of Ref. 8.
The wave-absorbing control is a control concept to absorb or shunt waves travelling in a flexible structure at the actuators before the travelling waves form the standing waves, i. e., steady vibrations, which cause deterioration of the stringent performance of flexible structures. This paper presents an approach to designing a broadband compensator by applying the H∞ control theory to the wave-absorbing control method. The present approach aims to minimize the effect of the incoming waves on the outgoing waves at the actuators in the sense of the H∞ norm of a scattering matrix. An application example of the present approach is shown by designing a compensator for a cantilever beam which is controlled at the free end. The performance and features of the designed compensator are examined both in the frequency and time domains. Its robustness characteristics are also examined.
An analysis of impact resistance of composite fan blades for turbo-fan engines has been conducted. Analytical models of composite blade of different sizes and materials were composed and impact resistance was evaluated by the analysis. The validity of the analytical model was confirmed by comparison of the analytical result with the experimental result of natural vibration of the titanium blade model of the same configuration as the composite blade models. The transient response produced by simulated bird strike on the blade model was analysed with the finite element method which includes bird impact load model and geometrical nonlinierity. The validity of the analytical method was confirmed by comparing the analytical results with the experimental results of some impact tests of the titanium blade models. The results show that polymer matrix composite blades have much lower impact resistance than titanium blade and it is clear that the composite blade of same size as the titanium blade is entirely broken by the bird strike, and 1.65 and 2.06 times larger size composite blades are partially broken by the bird strike.
The aerodynamic characteristics around a wing tip are investigated with a first order panel method. The geometry chosen for the study is a rectangular wing of aspect ratio 8.43, with RAF6 airfoil of 10% thickness ratio. The panel method gives similar aerodynamic characteristics to experimental ones even near the tip, such as very low pressure distribution existing near trailing edge around the tip, and increase in local lift and drag at the very narrow region of the tip. These properties are caused by the strong spanwise velocity component around the wing tip, the inviscid effects of which are described in detail, with respect to pressure coefficient, local lift and drag coefficients, downwash, and vorticity on the wing.
A calculation method of the maximum heat load for an axially grooved heat pipe which is embedded in a honeycomb sandwich panel with multi-point heating is developed by considering the estimation of heat flux rate along the heat pipe. A thermal mathematical model for the panel is also used to estimate the net heat input to the heat pipe. The maximum heat loads predicted for the heat pipe embedded in the panel show good agreement with the data obtained from tests which has been performed in a vacuum chamber. A minimum weight design method for rectangular grooved heat pipes which satisfied heat transport capabilities required are also proposed as a result of this study.