Showing papers by "Young I. Cho published in 1988"
TL;DR: In this paper, the effect of rain droplet impingement on the nose of an unarmored plastic projectile has been investigated in the simulation of rainfall in an airstream.
Abstract: Unarmed plastic projectiles can be equipped with small axisymmetric cavities for the generation of intense tones that are useful in training maneuvers. Attention is presently given to the simulation of rainfall in an airstream and the effect of rain droplet impingement on the nose of projectiles, and especially to any penetration or accumulation of water at the base of the cavity that might increase the fundamental cavity frequency and/or reduce the intensity of sound production during rain conditions.
4 citations
TL;DR: In this article, a ground-based microphone was used to obtain the angular distribution of sound intensity produced from the flying projectile, which can be used to plot an intensity contour map on the ground.
Abstract: Training projectiles with axisymmetric ring cavities that produce intense tones in an airstream were shot in a straight‐line trajectory. A ground‐based microphone was used to obtain the angular distribution of sound intensity produced from the flying projectile. Data reduction required calculation of Doppler and attenuation factors. Also, the directional sensitivity of the ground‐mounted microphone was measured and used in the data reduction. A rapid angular variation of sound intensity produced from the projectile was found that can be used to plot an intensity contour map on the ground. A full‐scale field test confirmed the validity of the aeroacoustic concept of producing a relatively intense whistle from the projectile, and the usefulness of short‐range flight tests that yield acoustic data free of uncertainties associated with diffraction, reflection, and refraction at jet boundaries in free‐jet tests.
1 citations