Experimental study on wavefront flow characteristics of dam-break wave at initial stage on wet bed

Abstract

The flow characteristics of dam-break wave in the initial stage of downstream wet bed are studied experimentally by digital image measurement technologies. First, the fine wavefront structure and its velocity were captured by the optical flow method, and an image measurement technology of water level based on edge detection was proposed. Then, the comparison and verification were carried out using the numerical simulation. The mean error is −7.369%, −1.243%, and 1.317% under depth ratio (σ) is 0.2, 0.25, and 0.33, and the error of most cases is within ±15% except σ = 0.2. The results show that large eddy simulation combined with volume of fluid method could accurately predict the distribution of dam-break water level, but it tends to overestimate the propagation velocity of the wavefront by about 10.3%. In addition, Stoker's quasi-steady paradigm has been proven to accurately predict the mean and steady-state flow characteristics of dam-break wave. Furthermore, the wavefront structure of the initial stage was subdivided into three sub-stages, namely, the jump stage, the transition stage, and the stable stage. Following that, the flow characteristics of each stage under the condition of the σ = 0.25 were studied in detail. The results show that the morphology of the wavefront structure is driven by the transformation of its internal energy in the initial stage. In summary, the work reveals the flow characteristics and quantitative flow results of the initial stage of dam-break wave under the wet river bed, thus improving the accuracy of dam-break accident prediction.