Sediment-Bed-Turbulence Coupling in Oscillatory Flows: Fully Resolved Numerical Experiments and Modeling

振荡流中的沉积物-床-湍流耦合：完全解析的数值实验和建模

• 批准号: 1133363
• 负责人: Sourabh Apte
• 金额: $ 28.03万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1133363&HistoricalAwards=false
• 关键词: Sediment; Bed; Turbulence; Coupling; Oscillatory

1133363ApteSediment transport, in rivers and coastal regions, affects large-scale geomorphic processes of dune formation, beach erosion and landform evolution that can displace human settlements, as well as destroy vegetation and agricultural infrastructure with strong socio-economic impact. Large-scale predictive computations of large-scale sediment-laden flows typically employ simplistic models for (i) incipient motion and resultant the bedload transport, and (ii) suspended sediment transport. These models are based on quasi-steady models based on averaged bed-shear stress for erosion onset and advective-diffusive transport based continuum models, neglecting particle inertia and are limited in their ability to accurately predict sediment erosion, entrainment and transport. Lack of accurate criteria for onset of incipient motion and sediment pickup function remain two of the biggest hurdles in developing better predictive models for sediment transport.A numerical investigation of sediment-bed-turbulence interactions is proposed in oscillatory turbulent boundary layers representative of coastal environments. The primary research objective is to quantify the effect of these interactions on the onset of erosion, entrainment, suspension, and deposition of sediments. The broad range of spatio-temporal scales associated with particle-particle and particle-fluid interactions makes modeling of sediment transport at practical scales extremely challenging. The proposed research builds upon the following main hypotheses: (i) the dynamics of near-wall turbulence structure and resultant variations in the magnitudes and time-scales of the destabilizing drag and lift forces on sediment grains are critical in formulating predictive criteria for onset of erosion, and (ii) particle inertia and variations in suspended sediment concentration due to fluidization and settling of sediments substantially affects the spatio-temporal evolution of the wall-events in the outer as well as inner regions of a turbulent boundary layer. Use of high-fidelity numerical simulations and modeling are proposed to test these hypotheses.Intellectual Merit: The novelty of this research is in the development and use of a fully resolved simulation (FRS) approach based on first principles, without requiring models for drag and lift forces, for the study of sediment incipient motion. This work will, for the first time, provide data on the temporal variations in the magnitude of drag and lift forces on sediment grains, the time-scales associated with these variations, and their correlation to the sweep-burst events in turbulent boundary layers. Effect of temporal variations in drag and lift forces, due to the sweep-burst turbulence events, on incipient motion will be revealed, identifying the roles of bed shear stress (Shield's criterion) and local accelerations (Sleath's parameter), and impulse (Diplas' concept) on onset of erosion. The FRS studies varying the grain size, flow Reynolds number, and volume loading, will also yield flow parameterizations for development of better analytical and engineering predictions of erosion, scour, transport, and deposits based on continuum approaches. These flow parameterizations obtained from fully resolved numerical experiments have the potential to transform current practices in modeling sediment transport on practical scales.Broader Impact: The research methodologies and models are applicable to several other fluid-particle systems, such as fluid-structure interactions in biological applications and flapping wings in micro-air vehicles, inertial flow through porous media, oxy-coal combustion, among others. This research will yield a Numerical Water/Wind Tunnel (NWT), a virtual educational tool for fluid-particle systems. Several aspects of the NWT will be integrated into graduate courses and University Honors College (UHC) curriculum. Training workshops for local school teachers and demonstrations to students will be held on the role of simulation-based engineering and science in predictions of river and coastal sediments during the ongoing K-12 outreach activities.

1133363河流和沿海地区的沉积物迁移影响到沙丘形成、海滩侵蚀和地貌演变等大规模地貌过程，这些过程可能使人类住区迁移，并破坏植被和农业基础设施，造成严重的社会经济影响。大尺度含沙水流的大尺度预测计算通常采用简化模型，用于（i）起动和由此产生的推移质输运，以及（ii）悬浮泥沙输运。这些模型是基于准稳态模型的基础上平均床剪切应力侵蚀开始和对流扩散运输为基础的连续模型，忽略颗粒的惯性，并在其准确预测泥沙侵蚀，夹带和运输的能力有限。针对泥沙起动和泥沙起动函数缺乏准确判据的问题，提出了一种基于振荡湍流边界层的泥沙-床面-湍流相互作用数值模拟方法。主要的研究目标是量化这些相互作用的侵蚀，夹带，悬浮和沉积物的发生的影响。与颗粒-颗粒和颗粒-流体相互作用相关的广泛的时空尺度使得在实际尺度上模拟沉积物输运极具挑战性。拟议的研究基于以下主要假设：（i）近壁湍流结构的动力学以及由此产生的作用在沉积物颗粒上的不稳定阻力和升力的大小和时间尺度的变化，对于制定侵蚀开始的预测标准至关重要，及（ii）颗粒惯性及因沉积物流化及沉降而引起的悬浮沉积物浓度的变化，会显著影响沉积物的空间分布。在湍流边界层的外部和内部区域中的壁事件的时间演化。使用高保真数值模拟和建模提出来测试这些hypothes.Intellectual优点：这项研究的新奇是在开发和使用的一个完全解决的模拟（FRS）的方法的基础上的第一原则，而不需要模型的阻力和升力，泥沙起动的研究。这项工作将首次提供关于沉积物颗粒上的拖曳力和升力大小的时间变化、与这些变化有关的时间尺度及其与湍流边界层中的扫掠突发事件的相关性的数据。将揭示由于掠爆湍流事件引起的阻力和升力随时间变化对起动的影响，确定床面剪应力（Shield准则）和局部加速度（Sleath参数）以及冲激（Diplas概念）对侵蚀发生的作用。FRS研究改变粒径，流动雷诺数，和体积负荷，也将产生流参数化的发展更好的分析和工程预测的侵蚀，冲刷，运输，和存款的基础上连续的方法。 这些流动参数化得到充分解决的数值实验有可能改变目前的做法，在实际scales.Broader影响泥沙输运建模：研究方法和模型适用于其他几个流体颗粒系统，如流体结构相互作用在生物应用和扑翼微型飞行器，惯性流通过多孔介质，氧煤燃烧，除其他外。这项研究将产生一个数值水/风洞（NWT），流体粒子系统的虚拟教育工具。西北地区的几个方面将被纳入研究生课程和大学荣誉学院（UHC）课程。在进行中的K-12推广活动期间，将为当地学校教师举办培训讲习班，并向学生演示模拟工程和科学在预测河流和沿海沉积物方面的作用。