Session: 12-01-02 Wave theories II
Paper Number: 121514
121514 - The Front Runner of Roll Waves in Jiang-Jia Ravine
Mudflows triggered by earth slides in clayey material are hazardous, threatening the safety of people and destructive to infrastructures, posing severe problems for river and land management. The occurrence of landslides is often unforeseeable. However, dangerous waves of exceeding large amplitude have been regularly observed in Jiang-Jia Ravine and have been studied by Li et al. (1983), Engelund & Wan (1984), Scott & Wang (2004), and Wu et al. (1990). Wan (1982) also observed such wave occurrence in the Yellow River, where the flow experienced a sudden increase from a regular flow rate of 1000 m3/s to a peak flow rate of 12000 m3/s. Normal flow returned within a couple of days. How can a massive flow increase occur in such a brief period? Liu & Mei (1994) attributed the phenomenon to roll-wave instability in a Bingham plastic model of muddy fluid. With the presence of clay minerals, mudflow is highly viscous and non-Newtonian. Roll waves in mud often are laminar, occurring at relatively small Froude numbers. Our understanding of mudflow depends on rheological modelling. Theories of the roll waves in mud are also model-specific. Liu & Mei (1994) and Balmforth & Liu (2004) studied the roll waves using a Bingham plastic model. On the other hand, the theory of roll waves by Ng & Mei (1994) was based on the power-law model.
Coussot (1994) conducted laboratory experiments for roll-wave instability in laminar mudflow. His experimental results show the mudflow instability occurring at a Froude number as low as Fr = 0.12, much lower than the critical Froude number of 2 observed in turbulent flow by Brock (1967). The experimental results of Coussot (1994) are specific to the Sinard clay in the French Alps. The rheology and the mudflow instability were interpreted by Coussot (1994) using a Herschel-Bulkley model. On the other hand, O’Brien & Julien (1988) examined the rheology of Aspen muds using a Bingham-plastic model. But by far, the most comprehensive observation of roll waves was conducted for the mudflow in Jiang-Jia Ravine. Wu et al. (1990) used a Bingham-plastic model to describe the mudflow rheology and the roll waves in Jiang-Jia Ravine. Their observation was well documented, but the roll-wave data in Jiang-Jia Ravine have not collaborated with any analytical and numerical models.
In this paper, we examine (i) the rheological data of mudflows from various landslide muds using the Bingham-plastic model, the power-law model and the Herschel-Bulkley model, and (ii) the roll-wave instability focusing specifically on the development of the front runner produced by a local disturbance. We use a highly accurate shock-capturing numerical scheme developed by Yu & Chu (2022, 2023) to capture the front runner of the roll waves in mudflow. Simulations conducted on roll-wave development in the Jiang-Jia Ravine mudflow are closely collaborate with the field observation in the Ravine by Wu et al. (1990).
Presenting Author: Vincent Chu McGill University
Presenting Author Biography: Professor of Civil Engineering
McGill University
Authors:
Boyuan Yu McGill UniversityVincent Chu McGill University
The Front Runner of Roll Waves in Jiang-Jia Ravine
Submission Type
Technical Paper Publication