Characterisation of Vortex Flow Control Hydrodynamics for Sustainable Drainage Applications

《2010年洪水和水管理法案》为英国目前使用的方法提供了基本的立法基础，是对当今水务行业面临的全球挑战的直接回应。我们的国家基础设施系统必须是可持续的、有弹性的，并具有风险，设法将持续发展对自然和建筑环境的影响降至最低，这些都是EPSRC的优先研究领域。可持续排水系统是应对这些挑战的关键，该法附表3要求使用这种系统，在水量和水质方面实行强有力的排放标准。洪水衰减是SODS系统中采用的主要控制系统，而涡流制动是实现这一点的最有效的方法。涡流制动器的工作原理是，通过延长流动路径和增加能量损失，排放流动的能力降低，同时不会对水和碎屑的通过造成物理障碍。在这些系统中形成的涡旋在垂直平面内运行，因此重力的影响虽然以前被认为是可以忽略的，但从最初的测试中证明是显著的。该项目的核心目标将从实验和计算两方面调查这种垂直涡旋如何启动和取消启动的不同之处，以便能够评估和评价固有的水动力响应。充分了解这些差异对于涡流制动器的优化设计至关重要。如果要了解风暴的时间性质和涡旋控制系统的动态响应之间的相互关系，就必须解决刹车的运行顺序，以及对任何变化的后果和反应的了解，以及对总流量影响的评估。从本质上讲，涡旋的形成是一个两相流动问题，在启动和解除启动顺序以及运行周期的重要部分中，水和空气都混合在一起。使用标准开源CFD包的试验模拟已被证明在周期的这些部分是有问题的。到目前为止，标准CFD模拟表面相互作用的能力是有限的。该项目将得到使用格子玻尔兹曼方法(LBM)对流体动力学过程进行计算分析的发展的支持。LBM是一种计算流体力学中尺度系统，它不是求解Navier-Stokes方程，而是使用离散的Boltzmann方程来模拟牛顿流体的流动，模拟流动中颗粒的流动和碰撞。这种方法相对较新，在土木工程流量问题中很少使用。该系统对风暴时间变化的动态响应将使我们能够确定涡流制动器整个运行周期的典型响应特性，并通过这一特性更全面地了解最佳设计。

The Flood and Water Management Act 2010 provides the fundamental legislative underpinning for current approaches used in the UK and is a direct response to the global challenge that faces the water industry today. Our national infrastructure system must be sustainable, resilient and with risks that are managed to minimize the impact of continued development on the natural and built environment, all priority research areas of EPSRC. Sustainable drainage systems (SuDS) are key to addressing those challenges and Schedule 3 of the Act requires the use such systems, imposing robust discharge standards in terms of both the quantity and quality of water. Flood attenuation is the prime control system employed in a SuDS system and the vortex brake represents the most efficient method by which this can be achieved. A vortex brake works on the principle that by extending the flow path and increasing energy loss, the capacity to discharge flow reduces while not presenting a physical obstacle to the passage of the water and debris. The vortex that forms in these systems operates within the vertical plane and as such the influence of gravity, while previously assumed negligible, has proven from initial tests to be significant. The core objective of this project will investigate, both experimentally and computationally, the differences in how such vertical vortices prime and de-prime so that the inherent hydrodynamic responses can be appraised and appreciated. A full understanding of these differences is essential for an optimum design of a vortex brake to take place. The operational sequence of the brakes, along with an understanding of the consequence and response of any change, and an assessment of the impact on the total flow must be resolved if the interrelationships between the temporal nature of a storm and the dynamic response of the vortex control system are to be understood.By nature, the formation of the vortex is a two phase flow problem with both water and air mixing during the priming and de-priming sequence and during a significant part of the operational cycle. Trial simulations using standard open source CFD packages has proven to be problematical during these part of the cycle. The ability for standard CFD to model in particular the surface interactions is so far limited. The project will be supported by the development of a computational analysis of the hydrodynamics process using a Lattice Boltzmann Method (LBM). LBM is a computational fluid dynamics mesoscale system that instead of solving the Navier-Stokes equations, the discrete Boltzmann equation is used to simulate the flow of a Newtonian fluid by modelling streaming and collision of particles within the flow. This methodology is relatively new and has been rarely employed in Civil Engineering flow problems. The dynamic response of that system to the temporal changes in storms will allow profiling of typical response characteristics throughout the operational cycle of a vortex brake to be determined and through that, a fuller understanding of optimal design achieved.