Sedimentation from forced wall jets versus free gravity flows: integrating tank experiments and field data into a physics-based depositional model

近年来，人们越来越认识到弗劳德超临界密度流对深水碎屑沉积体系的影响。这些沉积物主要保存在扩展流的区域，那里的沉积程度最高。这种膨胀的流动区域可以用超临界射流来模拟。水下平面壁射流从孔板进入静水体并减速，可以被认为是与膨胀、点源流（如海底扇和水下冰接触扇）相关的沉积过程的基本模型。膨胀的超临界流的形态动力学对沉积物的扩散以及由此形成的水下冰接触扇（射流沉积）和海底扇（重力流沉积）的沉积结构有很大的影响。射流及其沉积表现出明显的近端到远端分带。密度弗劳德数对流动动力学和由惯性驱动的射流向密度驱动的重力流的演变起着主要的控制作用。平面壁射流与重力流之间的过渡对膨胀流沉积有较大的影响。现有的关于射流和重力流、流体动力学和形态动力学演化及其沉积的知识不足以解释其特征的层状和相序列。该项目旨在研究这两种流体类型，并通过整合油罐实验和现场数据的观察结果，制定识别其沉积物的标准。在本项目的实验部分，将在水池实验中对射流和重力流的形态动力学进行表征，实现控制流和泥沙参数的系统变化。在项目的现场部分，将研究与粗粒超临界海底扇流动膨胀带有关的沉积物。这些现场实例必须能够详细描述沉积结构和相序列，并提供足够的细节来反演流动强迫。通过将实验观测结果与露头岩层相结合，将开发出一种通用的、基于物理的扩展超临界密度流沉积模型。

Recently, the impact of Froude supercritical density flows on deepwater clastic depositional systems has been increasingly recognized. These deposits are mainly preserved in the regions of expanding flows, where the aggradation is highest. Such regions of expanding flow can be modeled as supercritical jet flows. Submerged plane-wall jet flows, which emerge from an orifice into a standing water body and decelerate, can be considered as basic model for depositional processes related to expanding, point-sourced flows, like submarine fans and subaqueous ice-contact fans. The morphodynamics of expanding supercritical flows have a large impact on the dispersal of sediment and the resulting depositional architecture of subaqueous ice-contact fans, deposited by jet flows, and submarine fans, deposited by gravity flows, respectively. Jet flows and their deposits display a distinctive proximal to distal zonation. The densimetric Froude number exerts a primary control on the flow dynamics and the evolution from inertia-driven jets into density-driven gravity flows. The transition between plane-wall jets and gravity flows has a large impact on the deposition by expanding flows. The existing knowledge of jet flows and gravity flows, their hydrodynamic and morphodynamic evolution, and their deposits is insufficient to explain the characteristic bedform and facies successions. This project is designed to investigate these two flow types and develop recognition criteria for their deposits by integrating observations from tank experiments and field data. In the experimental part of the project, the morphodynamics of jet flows and gravity flows will be characterized in tank experiments, enabling the systematic variation of the controlling flow and sediment parameters. In the field part of the project, deposits related to zones of flow expansion from coarse-grained supercritical submarine fans will be studied. These field examples must enable a detailed characterization of the depositional architecture and facies successions and provide sufficient detail to invert for flow forcing. By the integration of the observations from the experiments and the outcrops a generic, physics-based model for deposition by expanding supercritical density flows will be developed.