Hiroshi Shigefuji

Experimental Visualization of Sound Pressure Level and Vibration Around a Soundproof Barrier

The noise and vibration control are the one of important issues. A soundproof barrier, which covers a sound source with sound absorbing materials, is very useful for the noise reduction. When large noise and high temperature heat emit from the sound source, we must also consider the heat radiation as well as the noise reduction. The purpose of the present study is to investigate the relationship between sound pressure level and vibration on a soundproof barrier around a sound source. The effect of heat radiation hole on the sound insulation performance of the soundproof barrier is also investigated. The sound pressure level and the vibration displacement were similarly distributed on the surface of the barrier. Therefore, the vibration of the barrier was strongly influenced to the sound pressure level of the transmitted sound.Copyright

Intermittent Noises Due to Bubbles Sucked Into a Siphon Pipe

Intermittent noises arising from a siphon pipe attached to a toilet bowl are investigated experimentally. The see-through model of a drained system is used to study the relation between noises and flow patterns near the entrance of the siphon pipe. We observed the different manner of the formation of large bubbles for different values of sucking velocity in the siphon pipe. The overall value of the noise in the sucking period increases with increasing the draining velocity. When the draining velocity is constant, the largest noise is generated at completion of the large bubble attached on the wall. The intermittent noises in the early stage of the period are found to be caused by small bubbles separated from the tail of the large bubble. The small bubbles are torn off because of shear stress of the main flow acting on the bubble surface. Another intermittent noises arising in the last stage is caused by periodic formation of the large bubble near the entrance. The detailed process of the bubble formation in the siphon pipe and the noises are discussed in this paper.© 2003 ASME

Numerical Analysis of Free Surface Deformation in Water Tank

A siphon phenomenon is one of gas/liquid two-phase flows including free surface deformation. Since the large-scale deformation of the free surface causes a loud noise, it is important to investigate the motion of the free surface. The purpose of the present study is to reproduce a siphon phenomenon in computer, and to analyze an internal flow field of the siphon phenomenon. An oscillating flow in two-dimensional U-tube was simulated to verify our computational codes, and good agreement compared with the theoretical period was obtained. After that, the numerical reproduction of a siphon phenomenon was succeeded and the behavior of the free surface was captured reasonably.Copyright