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Quantification and modelling of bedform dynamics in unsteady flows

非定常流中床形动力学的量化和建模

基本信息

批准号：
NE/I013393/1
负责人：
Philip Ashworth
金额：
$ 6.61万
依托单位：
University of Brighton
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FI013393%2F1
关键词：
Quantification modelling bedform dynamics unsteady

项目摘要

The beds of most alluvial river channels are not flat, but comprise a series of undulating sedimentary accumulations termed 'bedforms' that include ripples and dunes. These bedforms exist over a range of scales, and are constantly moving and changing their shape, size and form in response to changes in flow discharge. These bedforms are the primary roughness elements that provide resistance to the water flow. The response of bedforms to a changing discharge is therefore critical for predicting flood inundation levels. Changes in flow discharge are more rapid than changes in the bedforms, such that bedforms are commonly out of equilibrium with the flow. This is very important as the vast majority of our bed-phase diagrams (stability field predictors that relate flow velocity and sediment size to the bedform types likely to be present), morphodynamic simulations, and numerical model predictions assume simplified bed morphologies that are based on equilibrium bed states and constant discharges. Consequently, many feedbacks within our models and predictions are either ignored or highly simplified. This is a significant shortcoming as it is these models that are used, especially in more populated and urban areas, to meet demands on safety against flooding, navigation, hydropower, aggregate mining and water supply. The astute management of these rivers is paramount, putting high demands on accuracy in design, implementation and monitoring. If such models are to be improved, then new fundamental understanding is required of the processes that underlie the dynamics of bedform adjustment to unsteady flow and ways of integrating such knowledge into modelling practice. As a step towards this goal, there is a need to link hydraulic controls, the response of sediment transport processes and morphological adjustment, and the changes in form drag and bed resistance to a range of unsteady flows. Once established, these relations can be used to help improve our understanding of these dynamic processes and predict better the river stage for a set of given discharge changes. This project will delineate these processes using a combination of (i) novel laboratory investigations in a state-of-the-art flume that will quantify the flow structure and sediment transport over fixed and mobile beds as stage varies, (ii) intense fieldwork during flood events in the Mississippi River that will map and quantify changes in bed morphology, flow structure and sediment transport, and (iii) development and application of an innovative numerical model of unsteady flow over a deformable 3D boundary. This modelling work will ensure that the results are generic and have a wider appeal, notably in the improvement of models that provide flood predictions and inform environmental management decisions. All data and output will be made freely available via scientific outlets but also through public dissemination events, the internet and via a GoogleEarth based XML interface.

大多数冲积河道的河床并不平坦，而是由一系列起伏的沉积堆积物组成，这些堆积物被称为“底形”，包括波纹和沙丘。这些底形存在于不同的尺度上，并不断移动，改变其形状，大小和形式，以响应流量的变化。这些底形是提供水流阻力的主要粗糙要素。因此，底形对流量变化的响应对于预测洪水淹没水平至关重要。流量的变化比床形的变化更快，因此床形通常与流量不平衡。这是非常重要的，因为绝大多数我们的床相图（稳定性场预测，涉及流速和沉积物的大小，可能存在的床型类型），形态动力学模拟和数值模型预测假设简化的床形态，是基于平衡床状态和恒定的流量。因此，我们的模型和预测中的许多反馈要么被忽略，要么被高度简化。这是一个重大的缺点，因为这些模型被用于，特别是在人口较多的城市地区，以满足对防洪、航行、水电、集料开采和供水的安全要求。这些河流的精明管理至关重要，对设计，实施和监测的准确性提出了很高的要求。如果要改进这种模型，则需要对床形调整到不稳定流的动力学过程以及将这种知识融入建模实践的方法有新的基本认识。作为实现这一目标的一个步骤，有必要将水力控制、沉积物输运过程和形态调整的反应以及形状阻力和河床阻力的变化与一系列非恒定流联系起来。一旦建立，这些关系可以用来帮助我们提高对这些动态过程的理解，并更好地预测一组给定流量变化的河流水位。本项目将使用以下方法来描述这些过程：（i）在最先进的水槽中进行新颖的实验室调查，将随着水位的变化量化固定和移动的河床上的水流结构和沉积物输运，（ii）在密西西比河洪水事件期间进行密集的实地调查，将绘制并量化河床形态、水流结构和沉积物输运的变化，以及（iii）开发和应用一种新的三维可变形边界上非定常流的数值模型。这一建模工作将确保结果具有通用性，并具有更广泛的吸引力，特别是在改进提供洪水预测和为环境管理决策提供信息的模型方面。所有数据和产出都将通过科学渠道免费提供，但也可通过公共传播活动、互联网和基于GoogleEarth的XML界面免费提供。

项目成果

期刊论文数量（3）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

The adaptation of dunes to changes in river flow

DOI：
10.1016/j.earscirev.2018.09.002
发表时间：
2018-10
期刊：
Earth-Science Reviews
影响因子：
12.1
作者：
A. Reesink;D. Parsons;P. Ashworth;J. Best;R. Hardy;B. Murphy;S. McLelland;C. Unsworth
通讯作者：
A. Reesink;D. Parsons;P. Ashworth;J. Best;R. Hardy;B. Murphy;S. McLelland;C. Unsworth

The Impact of Nonequilibrium Flow on the Structure of Turbulence Over River Dunes