Experimental study on impulse waves generated by a viscoplastic material at laboratory scale

Abstract

This experimental study provides insight into impulse waves generated by a viscoplastic material. The viscoplastic material chosen is a stable polymeric gel called Carbopol Ultrez 10, which is approximately modeled as Herschel–Bulkley model. As observed from high-speed cameras, the viscoplastic material such as Carbopol moves as a long and thin train of material along the slope, and only a fraction of the sliding mass is engaged in generating the leading wave. Therefore, our primary objective is to study how much of the initial slide mass is able to contribute to the leading wave formation. For the sake of distinguishing the actual slide mass acting on the leading wave formation with the initial mass, we define the submarine slide mass when the leading wave reaches its maximum wave height as “effective mass”. In this work, we held the still water depth and slope angle constant, and varied the initial slide mass and slope length. Then, we measured the slide velocity, slide thickness, and slide mass at impact, as well as the wave amplitude and wave height. The results indicate that the effective mass is dependent on both the initial slide mass and the slope length. The ratio of the effective mass to the initial slide mass is less than 20% in our experimental range, and the ratio increases with larger initial mass. In addition, we also examined our experimental data with previous empirical equations developed from granular slides. By considering the effective mass instead of the initial slide mass, the prediction of impulse waves generated by viscoplastic material is significantly improved.