Yoshitaka Ochiai

Analysis of human glottal velocity using hot-wire anemometry and high-speed imaging.

Objectives: The aim of this study was to analyze glottal velocity and glottal opening and closure. For this purpose, we developed a miniature, flexible, hot-wire probe that can make truly instantaneous measurements of the human larynx in vivo. Methods: A miniature hot-wire tip was inserted into a flexible transnasal endoscope. Fiberscopic examination was performed transnasally so that we could observe glottal vibration using high-speed imaging. The tip of the hot-wire probe was placed just above the glottis. The position of the probe was carefully monitored and checked with another flexible endoscope. Results: Changes in velocity were recorded periodically. The velocity was higher in close proximity to the vocal folds. High-speed motion pictures were taken at a rate of 2,000 frames per second with an auxiliary light source. Conclusions: Quantitative analysis of glottal velocity is required to improve our understanding of the relationship between laryngeal physiology and acoustics in humans. To solve the problem of synchronization inaccuracy, glottal velocity was captured instantaneously in the high-speed imaging systems processor memory.

Experimental studies on vortex shedding frequency of a bluff body in a pulsating flow. Equilateral triangular cylinder.

Vortex shedding frequency was measured downstream of the equilateral triangular cylinder in a pulsating flow. A hot-wire anemometer was used for the velocity measurement. The Strouhal number based on the shedding frequency was substantially higher than that for the steady flow. Spectral components other than basic shedding frequency were observed to show significant levels as the pulsation amplitude of the flow increased.

Experimental studies on piston slap in diesel engines. Effect of gudgeon pin offset.

A series of experiments was performed on a small high-speed automobile engine which was an in-line four-cylinder IDI engine. Acceleration was measured on both sides of cylinder liner under various running conditions of the engine, that is, the rotational speed, the load and cooling water temperature. In order to evaluate the characteristics of the slap-induced vibration, acceleration recorded in the neighborhood of firing TDC was analysed to obtain such statistical quantities as the autopower spectra, the crosspower spectra and coherence functions. It was experimentally confirmed that the gudgeon pin offset to thrust side had the effect of decreasing the vibration level, but the effect varied depending the running condition.

Experimental Studies on Piston Slap in Diesel Engines

The secondary movement of the piston within the piston-cylinder clearance was measured on a small automotive IDI diesel engine. A total of six inductive transducers were installed on the piston skirt to measure the clearance. Slap-induced vibration measurement was made on the liner, the cylinder block and the head bolt. The effects of the gudgeon pin off-set, the engine speed and the load on the piston slap phenomena are discussed. Some of the experimental results of the piston secondary movement are compared with the numerically simulated movement of the piston. It is suggested that the profiles of the piston skirt and the cylinder have also important effects on the impulse of the piston slap.

Experimental studies on piston slap in diesel engines.

小形乗用車用渦流室式ディーゼル機関のピストンの二次元運動を,ピストンスカート部に合計6個取りつけた電磁誘導形ピックアップで計測した。ピンオフセット,回転数,負荷の影響を論じた。着火上,死点後のスラップによる振動に関して,シリンダライナに直接装着した加速度ピックアップおよびシリンダブロック上のピックアップによる振動測定も行った。両者の高いコヒーレンスが認められた。いくつかの数値シミュレーション結果も示す。