Examination on the existence of slow wave in fluid saturated porous medium (FSPM) with the optical method

With the shadowgraph method,three ultrasonic pulses in water,which corresponds to the conversion modesof the fast compressional wave the transverse wave and the slow compressional wave in the sample of fluid-saturatedporous medium (FSPM) respectively,were observed and recorded by CCD camera.The position of each pulse is consistentwith the computed position and the results measured by transducer.