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

近年来，弗劳德超临界密度流对深水碎屑沉积体系的影响日益受到重视。这些矿床主要保存在沉积程度最高的扩张流区域。这样的扩张区可以被模拟为超临界射流。水下平面-壁面射流从孔口进入静止水体并减速，可以被认为是与扩展的点源流有关的沉积过程的基本模型，如海底扇和水下接触冰扇。膨胀超临界流的地貌动力学对沉积物的扩散和由此产生的由喷流沉积的水下接触冰扇和由重力流沉积的海底扇的沉积结构有很大的影响。喷流及其沉积在远端环带显示出独特的近端分带。密度弗劳德数对流动动力学和从惯性驱动射流到密度驱动重力流的演化起着主要的控制作用。平壁射流和重力流之间的过渡对扩张流动的沉积有很大影响。现有的关于喷流和重力流、其水动力和地貌动力学演化以及沉积的知识不足以解释具有特征的台地和相序列。该项目旨在研究这两种流动类型，并通过结合水槽实验和现场数据的观测来制定其沉积物的识别标准。在本工程的试验部分，将在水槽试验中表征喷流和重力流的形态动力学，从而实现控制水流和泥沙参数的系统变化。在该项目的现场部分，将研究与粗粒超临界海底风扇的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体系结构和相序，并提供足够的细节来反转流动强迫。通过综合来自实验的观测和露头，将开发一个通用的、基于物理的、通过扩展超临界密度流进行沉积的模型。

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.