This paper describes on the frequency characteristics of discrete tone which is emitted when a thin circular cylinder is placed in a high subsonic jet in the vicinity of a circular nozzle exit. This discrete tone has similar characteristics to ordinary edge-tone which is emitted in a low speed jet stream. But, the frequency of this discrete tone decreases as the wind velocity increases, and this tendency is opposite to that of ordinary edge-tone characteristics. The frequency of this discrete tone is calculated by using a model of aerial vibrations in an open pipe, and is compared with the experimental values.
The expansion of a two-dimensional flow due to the resistance of an oblique wire gauze at setting angles of 30 to 75 degrees has been studied analitically by applying revised TAYLOR'S method.1) Measurements were also made on the expansion of flow in a two-dimensional smoke wind-tunnel, and a agreement between the calculated and measured profiles of flow was found. Additionally, flow observation and velocity-distribution measurement were carried out for a model diffuser equipped with the oblique wire gauze having low pressure drop coefficient.
A simple system of CARS (Coherent AntiSTOKES RAMAN Spectroscopy) was constructed and applied to measurements of the distribution of the concentration of hydrogen in a hydrogenair diffusion flame. The apparatus is similar to that used by TARAN et al.: The incident beam from a giant pulse ruby laser into a cell filled with high pressure hydrogen generates stimulated RAMAN emissions. The first order STOKES light selected from the emissions together with the original ruby laser light is focused in the system containing hydrogen and the intensity of CARS light thus generated is measured. Using the method similar to that for estimating the density distribution of a axially symmetric system from a shadowgraph, the distribution of hydrogen concentration in the flame could be determined quantitatively. The results were compared with that of the calculation using the BURKE-SCHUMANN's model and the problems which should be considered in experiments with this technique were discussed.
Nonlinear equations of vibration of shallow cylindrical panels with clamped edges are derived in the framework of the linear viscoelasticity and the large deflection theory. The static external pressure-displacement curve of the panel is calculated and the snap-through and the branchpoint buckling are studied before revealing the response property to random excitation. At first the influence of the number of the normal modes used in the analysis on the curve is revealed. For square panels the load-displacement curves become complicated depending on the ratio of shell rise to thickness and two types of snapthrough phenomena are disclosed. In the case where the ratio is 10, snap-through loads are obtained two times in the process of increasing pressure. In the case where the panel aspect ratio is two, the load-displacement curve becomes rather simple and has one snap-through load.
Probabilistic properties of nonlinear response of cylindrical panels to random excitation are studied by simulation method to disclose the effects of curvature of the panel on the sonic fatigue life. Simultaneous nonlinear differential equations derived in the part I are solved numerically by NEWMARK's β method and the fatigue life is calculated with a cumulative damage rule. The results show that the curvature is effective to prevent sonic fatigue when the exciting force is not large and the response is small, but harmful when the response is very large. The following response properties are revealed. The PDF of stress decreases much more slowly at the high positive stress region than that of gaussian process does when the response of the panel seldom exceeding the point of the snap-through buckling or the minimum rigidity. In the case where the panel response is very large, the dominant mode of vibration becomes one-half-wave pattern and different from the normal mode of vibration.
After Robert P. CILEMAN, a great many researches on the ground resonance of helicopter have been developed by a lot of scholars. Yet we have not enough to the experimental data until now, and some excellent and simplified analytical methods for this problem are needed. In this paper, the comparison are set up between the experimental results and the numerical calculations in the new method. That was suggested by Dr. Isamu IMAXHI. An agreement between them is very well. It is concluded that the present work has some contribution for the analysis of ground resonance of helicopter.