The stability of a slender fixed-free elastic strip in a uniform air stream is studied analytically. The analysis is performed using slender body aerodynamic theory and beam theory. It is seen that the aerodynamic instability occurs as a result of coupling between first and second bending modes.
The effects of water vapor condensation on the transonic turbine cascade flow in a suction type shock tunnel are investigated by the optical methods and by the wake traverse method using the Pitot comb with silicon oil containing tubes. It is shown that the flow pattern and the downstream total pressures are influenced considerably by the condensation for the supersonic exit flow. The traverse test results using the shock tunnel with dried air (Dew point Td=-10°C) show fairly good agreement with the experimental results in an ordinary blow-down type wind tunnel, which are considered to have almost no effects of water vapor condensation.
This paper describes an experimental investigation on the blockage effect of an upper wall of wind-tunnel on the wake of a two-dimensional flat plate normal to a plane boundary in a uniform stream. The experiment was carried out in the 40cm×40cm N.P.L. type wind-tunnel having the working section of 2m long. The distributions of the velocity and static pressure of the flow field, the vortex generating region behind the flat plate, the surface pressure and the drag coefficient of the flat plate, and the shear flow near the wall in the wake region were measured and the results were discussed in comparison with those of the existing investigations and the theory.
An investigation concerning the noise source distribution of a coaxial double jet in subsonic speed was conducted by means of a reflector-type directional microphone system which operated on the image principle of an elliptical concave reflector of diameter of 40cm. The effect of the velocity ratio of the bypass jet to the main jet on the apparent source strength distribution for flow direction on the jet axis was clarified in one-third octave band and overall frequency. The distribution of pressure fluctuations in the jet flow was also compared with that of the noise source intensities. The sound power generated by unit axial length of the jet flow was calculated by an iterative technique with the measured noise source distribution and the directional characteristics of the microphone. And, the amount of the noise reduction was estimated. The calculated results agreed with the measurement by the non-directional microphone.
In order to improve the accuracy of measurement of DOPPLER type miss distance indicator (MDI) used to measure the miss distance between a flying body and a target by utilizing the DOPPLER effect of radio wave, the possibility of MDI of 2 way DOVAP type was investigated and a measuring method capable of obtaining the miss distance by the use of integration data of DOPPLER frequency obtained from the oscillograph of DOPPLER beat and from direction cosine data was found out. In the present paper, the measuring principle of measuring method, the simulation test conducted to ascertain the establishment of the measuring principle, the results of the test, and the results of our investigation on the measurement error were described. It was also described in the present paper that the miss distances up to about 20m can be measured with an accuracy of within±1m of measurement error by this method and that the methods can make a measuring method which is practicable in the evaluation of the performance of precision guided flying bodies passing by at so near a distance as within 10m of miss distance.
An experimental study of the special type resonance tube inclining by an angle of 30° to 50° with respect to the nozzle axis has been conducted here. The gas within the tube is excited to intense periodic oscillations and the gas temperature at the closed tube end reaches some 150°C. The mechanism of the oscillation excitation has been found to be the periodic deflection of the supersonic jet caused by the collision of the jet with its swirl flow at the open tube end. Furthermore, not only several relationships between gas temperature, geometrical parameters of the tube, nozzle inlet pressure and inflow angle, but also distributions of gas temperature, wall pressure and high-intensity sound radiation are presented in detail.