The hydrodynamics of microbial landscapes

微生物景观的流体动力学

• 批准号: NE/K01210X/1
• 负责人: Richard Hardy
• 金额: $ 22.38万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK01210X%2F1
• 关键词: hydrodynamics; microbial; landscapes

The way in which water flows across a surface is one of the most complex phenomena to model and predict accurately in the environment. Understanding complex flows moving into and from pebbles and gravels on river beds is especially challenging An additional level of complexity that has been largely overlooked in this environment is the effect that microorganisms such as algae, (collectively known as biofilms), attached to surfaces have on the flow processes. Given that biofilms occur in all natural environments and many engineered contexts such as wastewater systems this represents a significant knowledge gap. But why do we need to understand flow-biofilm interactions? Firstly, stream ecologists recognise that the bed of the river is an important habitat for a diverse range of species. The way flow from above the bed makes its way into the subsurface largely dictates how much oxygen and nutrients are supplied to this habitat. Secondly, fisheries managers have long understood that the probability of salmon eggs hatching in river beds will be dependent on a continuous supply of oxygenated water to the gravelly sediments in which they are laid. Thirdly, knowledge of how biofilms can affect the conveyance of flow within wastewater systems or lead to discolouration of potable waters is an important consideration for water managers. There are thus a broad range of highly important environmental and engineered contexts that require detailed predictions of how water moves, yet there is no way of measuring or modelling this accurately which takes into account the effect that biofilms may have to influence these processes. The overall aim of this proposal is to develop a quantitative numerical representation of micro-scale hydraulic response to biofilm forcing. This will be achieved by using pioneering new experimental and numerical approaches to meet this challenge. The first task is to accurately measure flow both right at the bed and within the biofilms and pore spaces of the bed themselves. This significant problem will be overcome by using laboratory PIV (particle imaging velocimetry) techniques in a range of small channels containing intact biofilm cultures. The technique works by seeding the flow with tiny reflective particles, and providing high intensity illumination from a laser, a camera then records how they move within the flow around the biofilms and within the pore spaces of the experimental channel. Using a special processor, these digital images can be turned into numerical data that accurately records how flow moves across and then into the river bed. Such measurements have never been possible before. The second phase of the project is to use the new understanding made possible by this unique dataset to develop and test a 3-D numerical model that can be used to further understand and explore the influence of biofilms on the flow processes at and within the bed over a much broader range of environmental and engineered contexts. This will be achieved using a specially modified computational fluid dynamics (CFD) model which will be developed so that it can account for the dynamic nature of the biofilms (i.e. the fact that they move with the flow) that live on the more stable channel surface.The advances in measurement and modelling approach that will be used in this project represent real breakthroughs that will unlock the inherent problem of gaining useful data from one of the most challenging of environments. Meanwhile, the development of a numerical model that can be widely used will ensure that this new understanding can be applied and adapted to meet a variety of real world environmental challenges as well as being of relevance to areas such as the wastewater industry.

水流过表面的方式是环境中最复杂的现象之一，需要准确建模和预测。了解复杂的流动和从河床上的卵石和砾石移动是特别具有挑战性的。在这种环境中，在很大程度上被忽视的另一个复杂性水平是附着在表面上的微生物（如藻类）（统称为生物膜）对流动过程的影响。鉴于生物膜发生在所有自然环境和许多工程背景下，如废水系统，这代表了一个显着的知识差距。但是，为什么我们需要了解流动生物膜的相互作用？首先，河流生态学家认识到，河床是各种物种的重要栖息地。从河床上方流入地下的方式在很大程度上决定了为这个栖息地提供了多少氧气和营养物质。第二，渔业管理人员早就知道，鲑鱼卵在河床中孵化的可能性取决于向产卵的砾石沉积物持续供应含氧水。第三，了解生物膜如何影响废水系统内的水流输送或导致饮用沃茨变色，是水管理人员的一个重要考虑因素。因此，有广泛的高度重要的环境和工程背景，需要详细预测水如何移动，但没有办法准确地测量或建模，考虑到生物膜可能会影响这些过程。该提案的总体目标是开发一个定量的数值表示的微尺度水力响应生物膜强迫。这将通过使用开创性的新实验和数值方法来应对这一挑战来实现。第一项任务是准确测量床层处以及生物膜和床层本身孔隙内的流量。这一重大问题将克服使用实验室PIV（粒子成像测速）技术在一系列的小通道包含完整的生物膜培养。该技术的工作原理是用微小的反射颗粒接种流动，并提供来自激光的高强度照明，然后相机记录它们如何在生物膜周围的流动和实验通道的孔隙空间内移动。使用一种特殊的处理器，这些数字图像可以转化为数字数据，精确记录水流如何穿过河床，然后进入河床。这样的测量以前是不可能的。该项目的第二阶段是利用这个独特的数据集所带来的新认识来开发和测试一个三维数值模型，该模型可用于进一步了解和探索生物膜对床内和床内流动过程的影响，范围更广。这将使用一个特别修改的计算流体动力学（CFD）模型来实现，该模型将被开发，以便它可以解释生物膜的动态性质（即它们随流动而移动的事实）在测量和建模方法方面的进步将用于该项目，代表了真实的突破，将解开获得有用数据的固有问题从最具挑战性的环境之一。同时，开发一个可以广泛使用的数值模型将确保这种新的理解可以应用和调整，以满足各种真实的世界环境挑战，以及与废水工业等领域的相关性。

项目成果

A numerical investigation into the importance of bed permeability on determining flow structures over river dunes

• DOI: 10.1002/2016wr019662
• 发表时间: 2017-04
• 期刊: Water Resources Research
• 影响因子: 5.4
• 作者: S. Sinha;R. Hardy;G. Blois;J. Best;G. S. Sambrook Smith

The Effect of Biofilms on Turbulent Flow Over Permeable Beds

• DOI: 10.1029/2019wr026032
• 发表时间: 2020-12
• 期刊: Water Resources Research
• 影响因子: 5.4
• 作者: F. Kazemifar;G. Blois;M. Aybar;Patricia Perez Calleja;R. Nerenberg;S. Sinha;R. Hardy;J. Best;G. S. Sambrook Smith;K. Christensen