Strong shock waves around 10km/s are generated in low-density (13.3Pa) air by using a free-piston, double-diaphragm shock tube with test section of 40mm×40mm. Two-dimensional pictures of radiation intensity behind the shock waves are taken at the test section, and analyzed by combined usage of an image converter camera and an image processor. Contour plots and time histories are derived from the radiation images by image processing for several shock speeds around 10km/s. The contour plots gives us informations about two-dimensional features for radiation intensity, and the time histories reveal transition characteristics on double peaks in radiation profile around 10km/s.
Laminar separation bubbles formed on airfoils were expressed numerically using a simple eddy-viscosity turbulence model. The eddy viscosity constant, εt, was set to a uniform value inside the turbulent part of the bubble. Overall characteristics of numerical results agreed closely with experimental results. The relation between εt and velocity distributions was analyzed by the momentum balance inside the bubble. It was shown that the pressure recovery inside the bubble is proportional to εt. Finally, the semi-empirical parameter which determines εt was proposed.
An experimental study was carried out in which a vertically hanged cylindrical tank partially filled with water was longitudinally excited at the center of the bottom for several water levels. The shell was made of polyester film. The theoretical value was calculated by the method of analysis derived in Part I for comparison. The critical exciting force amplitude to produce one-half subharmonic wall vibration was measured at each constant exciting frequency by gradually increasing it. For the parametric excitation boundary, reasonably good agreement is observed between experimental and theoretical results. The resonance curves of longitudinal vibration at the bottom and the transverse wall vibration were measured under the condition of constant amplitude of longitudinal exciting force. The property of the resonance curves can be explained by the present analysis.
A rigid multibody system of tree configuration whose base is free is treated in this paper. Equations of motion are derived based on Kane's ones using resolved vector components on the moving frame fixed on mainbody. This eliminates three variables, which denote the attitude of the mainbody when applied force and torque act parallel to the basis of the moving frame. As an example, equations of motion for the three-rigid-body system, a model of a springboard diver, are derived explicitly by symbolic manipulation, and a numerical result is shown to explain the motion of springboard diving.
In this paper, a study is described that compares the performance of a predictive fuzzy control law with that of an optimal feedback control law. The predictive fuzzy control scheme is a method which predicts the result and selects the most likely control rule based on a human's control strategy. Two mathods are applied to automatic rendezvous maneuvers to bring a spacecraft toward a target vehicle (typically a space station). It is shown that the predictive fuzzy controller can provide better performance compared with the optimal regulator, in the sense that it can assure collision avoidance in case of RCS jet failure.
A new method was developed for determining a slant hot-wire inclination to the axial flow direction in order to accurately measure the transverse velocity component. The method requires dual parallel laser beams near the focal point such as Laser-Two-Focus velocimeter beams, one of which can rotate around the other. Since the squared hot-wire bridge output is proportional to the mean value of the beam intensity exposed on the hot-wire element, the bridge output indicates the maximum variation, when the slant wire is exposed by just dual beams. This rotating angle is referred to as the slant angle of the wire, if necessary, relative to the freestream angle, which is exactly given by the Laser-Two-Focus velocimeter. Furthermore, it is pointed out in the measurement that the beams rotate in precession due to optical misalignment. This method may be applicable to optical alignment.