Time resolved visualization and analysis on a single short acoustic wave generation, propagation and interaction

Abstract

The generation and detection of short acoustic waves in liquid and solid media by short pulsed laser based techniques have been demonstrated to be efficient tools in many applied science and medical areas, including nondestructive evaluation and material characterization, laser cleaning of surface contaminants, laser tissue ablation, corneal sculpturing, and gall stone fragmentation. The laser energy interaction with the surface of an absorbing liquid or a transparent liquid in contact with an absorbing solid boundary, induces rapid heating, thermoelastic expansion or explosive phase change and finally emission of a strong ultrasonic wave or a shock wave, depending on the applied laser energy. Most of the laser induced acoustic wave experimental studies have aimed at the zerodimensional point detection of the propagating pressure transient at a fixed location by utilizing capacitance transducers, piezoelectric transducers, or hydrophones. These approaches can only be applied to idealized zero-or one-dimensional geometries and fail to capture the detailed acoustic wave behavior inside the medium, especially for complex two-or three-dimensional configurations. The direct transient observation of two or three-dimensional laser induced acoustic wave interaction with solid structure is very important to understand the physics of short acoustic wave and to validate the numerical simulation studies. In this chapter, the state of the art laser based time resolved (100ns resolution) visualization technique of a single, short acoustic plane wave generation, propagation in various external and internal channels and the subsequent interaction with submerged solid structures are presented. The effect of liquid viscosity on the acoustic wave propagation velocity, pressure attenuation, and wave broadening was investigated. The fluid viscosity was varied by mixing glycerol with DI water to yield liquid of 1, 10, and 100 cp in viscosity at room temperature. © 2012 Nova Science Publishers, Inc.