Evaluation Methodology of Laminar-Turbulent Flow State for Fluidized Material with Special Reference to Submarine Landslide

Abstract

Submarine landslides have destroyed many ocean engineering facilities and induced catastrophic tsunamis, causing considerable loss of lives and properties. However, the evolution process of submarine landslides is highly complicated and difficult to describe with a unified mechanical framework. For fluidized landslides with wider influence ranges, faster migration velocities, and stronger impact forces, it is necessary not only to describe the constitutive model but also to determine the flow state. First, based on the essential rheological test for determining constitutive models, the relevant method and principle are thoroughly analyzed, and the formula for calculating the Reynolds number of fluidized submarine landslides in the entire shear process is derived. Taking the critical Reynolds number as the evaluation standard, a methodology to distinguish the flow state (laminar or turbulent) of fluidized landslides is quantitatively proposed. Second, through the low-temperature rheological test, the proposed formula and methodology are briefly applied to the natural submarine sediment samples in the South China Sea. In addition, the point of contraflexure of the rheological curve is consistent with the critical Reynolds number calculated by the formula, and the validity of this methodology is further verified. Finally, the mechanism of the flow-state transition is systematically analyzed by the internal evolution of the structure of the fluidized sediment samples in the shear process. This study provides important support for understanding the migration of fluidized submarine landslides.