212 EFFECTS OF ULTRASONIC VIBRATIONS ON A TURBULENT SQUARE-DUCT FLOW(O.S.5 Advanced Technology for Usage of Sound and Vibration I)

概要

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Effects of ultrasonic vibrations on a turbulent (Re=7000±50) square-duct flow were investigated experimentally by means of LDV (Laser Doppler Velocimetry). Ultrasound was introduced into the flow by PZT-type transducers attached to the trapezoidal horn. The height range of the horn tip was in between the buffer layer and the fully turbulent region. Driven frequency and power supplied to transducers were nominally 45.5kHz and 20W respectively. The result shows that ultrasound makes low speed region near the center of the duct bottom wall, and that it entrains the flow in the center region to the horn. In the present horn arrangement shown in Fig. 2, the counter-clockwise (viewing from the upstream) vortex may lie in the lower left quarter square of the duct cross section. This is mainly caused by acoustic streaming. The test varying ultrasound frequency and power shows that it is clarified that main feature in the present study is caused by acoustic streaming, not the vibration transmitted from the horn itself.
一般社団法人日本機械学会の論文
2005-05-31