Experimental and Computational Turbulence in Engineering and Biological Flows

我的研究计划侧重于发现基本原理和流动物理，这些原理和物理控制着自由湍流（例如射流）和有壁流动（例如人体气道内）中湍流结构的时空演变。****本研究的目标是探索圆形湍流射流的近喷嘴区域，以发现其中遇到的湍流的程度和性质，并发现手术干预如何改善阻塞的人体气道中的压降和三维速度分布。每项研究都将采用计算机模拟和物理实验。****没有任何约束的射流是常见的，也是极其重要的基本流。在喷嘴区域，即射流开始的地方，远离射流开始的地方，称为远场，已经被广泛研究。然而，连接近喷嘴区域和远场的一个区域，包含丰富的流动物理，人们对它知之甚少，但它在将初始进口条件传输到远场充分发展的湍流中发挥着作用。我和我的学生将应用直接数值模拟（DNS），并使用我们独特的飞行热线设备来严格评估离其中心线的射流的各向异性和非均匀区域。我们将在喷嘴附近区域引入被动控制环，以改变初始条件，从而增强混合并潜在地降低噪声，这是庞巴迪宇航公司感兴趣的。****正常的肺功能与向每个肺输送相同数量的空气有关。人体气道中的气流阻塞会导致呼吸困难和空气输送到肺部的不对称。阻塞性睡眠呼吸暂停（OSA）通常与扁桃体/腺样体阻塞有关，可能需要手术纠正。正常的人类气道在几何形状上是复杂的，在整个气道中产生复杂的流动模式，特别是在会厌处和会厌外，进入气管产生所谓的喉射流，它包含自由射流的流动特征。阻塞性睡眠呼吸暂停患者的几何形状异常复杂，可在气管内产生高度不对称的血流，从而导致流向肺部的血流分布不均匀。我们将使用DNS和光学测量来探索手术前后几何形状内部的流动。随着孩子们越来越多地经历一系列与呼吸有关的健康问题，以及如今儿科气道手术越来越频繁，家长们面临着越来越多的担忧。临床医生需要更多地了解他们的手术所带来的流体动力学后果，这项研究将使之成为可能。****在此期间，14名HQP将接受流体动力学先进研究技术的培训，并将培养专业和沟通技巧，为他们在学术界和工业界的职业生涯做好准备。**

My research programme focuses on the discovery of the underlying principles and the flow physics that govern the spatial and temporal evolution of the structure of turbulence in both free turbulent flows (e.g. jets) and wall-bounded flows (e.g. inside the human airway).****The objectives of the research, each of which will employ both computer simulation and physical experiments, are to explore the near nozzle region of round turbulent jets to discover the extent and nature of the turbulence encountered therein and to discover how the pressure drop and the three dimensional velocity distributions in obstructed human airways are improved because of surgical intervention. ****Jets that are free of any confinement are common and a critically important fundamental flow. Flow in the nozzle area, where the jet starts, and well away from the start of the jet, called the far field, has been extensively studied. However, a region that bridges the near-nozzle area to the far field, which is rich in flow physics, is poorly understood and yet plays the role to transport initial inlet conditions through to fully developed turbulence in the far field. My students and I will apply direct numerical simulation (DNS) and use our unique flying hot wire facility to critically assess the anisotropic and non-homogeneous regions of a jet off its centreline. We will introduce passive control rings in the near nozzle region to alter the initial conditions thereby enhancing mixing and potentially reducing noise, which is of interest to Bombardier Aerospace.****Normal lung function is associated with delivery of the same amount of air to each lung. Obstructed airflow in the human airway gives rise to breathing difficulties and asymmetry in air delivery to the lungs. Obstructive sleep apnea (OSA), often associated with tonsil/adenoid blockage, may require surgery to rectify. Normal human airways are geometrically complex in shape and produce complicated flow patterns throughout the airway, particularly at and beyond the epiglottis and into the trachea to produce what is called the laryngeal jet, which contain flow features seen in free jets. The geometries in patients with OSA are exceptionally more complex and can produce highly asymmetric flow in the trachea that can lead to uneven distribution of flow to the lungs. We will use DNS and optical measurements to explore the flow inside pre- and post-operative geometries. Parents face growing concern as children are increasingly experiencing a range of breathing-related health issues and pediatric airway surgeries are being performed more often today.  Clinicians need to be more informed about the fluid dynamic consequences enabled by their surgeries, which this research will enable.****During this DG period, 14 HQP will be trained in advanced research techniques in fluid dynamics and will develop professional and communication skills to prepare them for careers in academe and industry.**