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Modelling flow over bedform fields in tidal environments

模拟潮汐环境中床型场的流动

基本信息

批准号：
345915838
负责人：
Dr. Alice Lefebvre, Ph.D.
金额：
--
依托单位：
Arbeitsgruppe Sedimentologie, Küsten- und Schelfgeologie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/345915838?language=en
关键词：
Modelling flow over bedform fields

项目摘要

This project aims at characterising the patterns of flow over bedform fields in tidal environments through high-resolution numerical modelling. Bedforms (ripples and dunes) are ubiquitous features in rivers, coastal and deep sea environments, where they reflect the strength and pathways of sediment transport, strongly influence the overlying flow and have a major socio-economic relevance, for example through the control of navigational depth and the safety of offshore constructions. In shallow tidal seas, large bedform fields develop due to the strong hydrodynamics and high availability of sandy sediment. Flow above these bedform fields differs fundamentally from flow above well-known angle-of-repose two-dimensional (2D) triangular bedforms which have been until now the focus of laboratory and numerical modelling studies. Bedform fields are intrinsically three-dimensional (3D), with sinuous crestlines, scour pits and crestlines bifurcations and terminations, they have complex profiles with slope discontinuities and low-angle lee sides. In the coastal zone, flow reversal during a tidal cycle further complicates the interaction between bedforms fields and hydrodynamics. The patterns of flow above such bedforms fields are still largely unknown, especially the influence of bedform three-dimensionality in relation to tidal flows, due to the difficulty in measuring accurately current velocities and turbulence at an appropriate spatial and temporal resolution. The proposed study will set up, calibrate and validate a 3D numerical model in order to characterise flow above natural bedform fields and morphological elements characteristic of bedform fields. This new model will allow for the first time to determine the patterns of current velocities and turbulence above natural bedforms fields in reversing tidal currents and to recognise the influence of each morphological elements and how they interact with each other. These results will enable a better parameterisation of small-scale processes into large scale hydro- and morphodynamic models.

该项目旨在通过高分辨率数值模拟来描述潮汐环境中底形场上的水流模式。底形（波纹和沙丘）是河流、沿海和深海环境中普遍存在的特征，它们反映了沉积物迁移的强度和路径，对上覆水流有很大影响，并具有重大的社会经济意义，例如通过控制航行深度和近海建筑物的安全。潮浅海由于水动力作用强，桑迪沉积物可利用性高，形成大的底形场。这些床型场上方的流从根本上不同于著名的休止角二维（2D）三角形床型上方的流，直到现在，三角形床型一直是实验室和数值模拟研究的焦点。底形场本质上是三维（3D）的，具有弯曲的波峰线、冲刷坑和波峰线分叉和终止，它们具有复杂的剖面，具有斜坡不连续性和低角度背风面。在海岸带，潮汐周期中的水流逆转使底形场和水动力学之间的相互作用更加复杂。由于难以以适当的空间和时间分辨率准确测量流速和湍流，因此，这种底形场上方的流动模式在很大程度上仍然是未知的，特别是底形三维性对潮汐流动的影响。本研究将建立、校正及验证一个三维数值模式，以模拟天然底形场上方的水流及底形场的形态要素特征。这个新的模型将允许第一次确定的模式，在扭转潮流的天然床型领域的流速和湍流，并认识到每个形态元素的影响，以及它们如何相互作用。这些结果将使一个更好的参数化的小规模的过程到大规模的水文和形态动力学模型。