Experimental and Numerical Modelling of Air Entrainment in Eco-hydraulics

生态液压中空气夹带的实验和数值模拟

• 批准号: RGPIN-2018-03994
• 负责人: Balachandar, Ramaswami
• 金额: $ 3.79万
• 依托单位: University of Windsor
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=690322
• 关键词: Experimental; Numerical; Modelling; Air; Entrainment

Air entrainment in free-surface flows is ubiquitous in eco-hydraulics. The entrained air influences the dissolved oxygen level and is very useful in water treatment to sustain microorganisms for water purification and in rivers and streams for sustaining a healthy aquatic life. However, excessive air entrainment in fish passages can result in gas-bubble disease and adversely affect fish migration. Aeration also occurs in oceans during the wave breaking process. Wave energy is said to be the largest source of renewable energy and could contribute 10% of the global electricity demand by 2050. Methods to extract the energy from the wave breaking process needs to be explored. These examples highlight the practical relevance of studying air-water flows.*** ***Self-aeration is an uncontrolled process and the dynamics of air-water flows is complex. Researchers have largely studied air-water flows experimentally and to a limited extent using numerical tools. While the studies have brought forth the complexity in the flows, the internal turbulence mechanism is not fully understood. This is due to the limitations in the commonly used single-phase flow instruments, which need to be improved or modified for use in air-water flows. The Achilles heel in the computational study of air-water flows is the air-entrainment model. To achieve success, an improved understanding of the physical processes that govern the flow is required. With the availability of improved instrumentation and enhanced computational facilities, it is now possible to begin a research program to develop practical tools that are required to predict the supersaturation of gases in rivers, to prevent fish-kill and to reduce odour in urban sewer systems.******A novel experimental and numerical research program is proposed to predict/control turbulence and air entrainment in free-surface flows. We will focus on flow fields that represent most of the complexities that one encounters in practical situations. We have chosen 3 flow fields: Hydraulic Jumps, Fish Passages and Breaking Waves. These flows have common features: high turbulence, free-surface breakup, air entrainment followed by bubble generated turbulence. Experimental studies using Bubble Image Velocimetry supported by complementary numerical modeling will be used.******The major goals include: (i) Improve our understanding of aerated flows by conducting experimental studies using state-of-the-art instrumentation and (ii) Develop computational fluid dynamics based models suitable for air-water flows. The physical processes that are responsible for aeration, air bubble interactions and breakup will be analyzed in the flow fields. The study will aid to improve the design of drop shafts, fish passages, spillways and urban hydraulic systems. The new tools will help to reduce future reliance on expensive physical model testing. Over the 5-year cycle, 14 HQP (4 PhD, 5 MSc, 5 BSc) will be trained.

自由表面流的空气夹带在生态融合物中无处不在。夹带的空气会影响溶解的氧气水平，并且在水处理中非常有用，以维持微生物的水净化以及河流和溪流，以维持健康的水生生物。 然而，鱼通道中的空气夹带过多会导致气体泡沫疾病，并对鱼类的迁移产生不利影响。在波浪破裂过程中，海洋也发生了充气。据说波能是可再生能源的最大来源，到2050年可能占全球电力需求的10％。需要探索从波浪破裂过程中提取能量的方法。这些例子突出了研究空气流量的实际相关性。*** ***自我平息是一个不受控制的过程，空气水流动的动力很复杂。研究人员在很大程度上通过实验研究了空气水流，并使用数值工具在有限的程度上研究了。尽管研究提出了流动的复杂性，但内部湍流机制尚未完全理解。这是由于常用的单相流量仪器的局限性，需要改进或修改以用于空气水流。空气水流计算研究中的致命弱点是空气式模型。为了取得成功，需要提高对控制流动的物理过程的理解。 借助改进的仪器和增强的计算设施，现在可以开始一项研究计划，开发实用工具，这些工具可以预测河流中气体的过度饱和，以防止鱼类杀伤和减少城市下水道系统中的气味。我们将专注于代表一个人在实际情况下遇到的大多数复杂性的流场。我们选择了3个流场：液压跳跃，鱼通道和破坏波。这些流具有共同的特征：高湍流，自由表面破裂，空气夹带，然后是气泡产生的湍流。将使用使用互补数值建模支持的气泡图像的实验研究。******的主要目标包括：（i）通过使用最先进的仪器进行实验研究来提高对充气流的理解，并开发基于计算流体的基于计算流体的模型。 将在流场中分析负责曝气，气泡相互作用和破裂的物理过程。该研究将有助于改善滴轴，鱼通道，溢洪道和城市液压系统的设计。新工具将有助于减少未来对昂贵的物理模型测试的依赖。在5年的周期中，将培训14个HQP（4博士学位，5 MSC，5 BSC）。