Control of ambient fluid on turbidity current evolution: Mechanisms, feedbacks and influencing factors

Turbidity currents are important ocean dynamic processes that influence sediment transport, ocean engineering, and marine environments. As a turbidity current evolves, its macroscopic and mesoscopic properties are controlled by ambient fluid mechanisms, including entrainment and mixing. These ambient fluid mechanisms are, in turn, influenced by changes in the multiscale properties of the turbidity current. These two aspects are often studied separately, and the feedback relationship between them is not fully understood. To reveal the feedback relationship and understand the control of ambient fluid on turbidity current evolution, this review summarizes and discusses the multiscale properties, ambient fluid mechanisms, feedback relationship, and the influencing factors from the relevant researches in the past 20 years. It is believed that ambient fluid entrainment and mixing change the multiscale properties of a turbidity current by affecting the overall dilution of the current and behavior of sediment particles. Changes in velocity, density, and stratification of the turbidity current enhance or suppress ambient fluid entrainment and mixing. Factors influencing the pattern and extent of the feedback interaction include the initial conditions of turbidity currents and their runout environments. The concept of ambient fluid – turbidity current – marine geological system is proposed. Under this system, the natural marine geological environment is considered in detail when studying turbidity current. Establishing this system necessitates improvements in research methods; particularly, improving the two-dimensional resolution of in-situ observations, developing new physics and numerical turbidity current generation methods, and using the Euler-Lagrange model to analyze interactions between particles and fluids, and between particles. Furthermore, complex external hydrodynamic fields as well as seabed geological fields could be considered in this system; this includes internal waves, bottom currents, typhoon-induced waves and currents, and canyon topography.