Laser doppler anemometer for turbulent and multiphase flows

用于湍流和多相流的激光多普勒风速计

• 批准号: 344750-2007
• 负责人: Bergstrom, Donald
• 金额: $ 4.12万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments - Category 1 (<$150,000)
• 财政年份: 2006
• 资助国家: 加拿大
• 起止时间: 2006-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=326282
• 关键词: Laser; doppler; anemometer; turbulent; multiphase

Most flows encountered in industrial and/or environmental applications are turbulent, which is to say that they are characterised by enhanced levels of mixing associated with apparently random small-scale fluctuations in the velocity field.  Turbulence has many important practical applications including increased skin friction drag and increased wall heat transfer rates.  In addition to turbulence, flows can exhibit additional sources of complexity, such as flow separation  from an exterior surface, which then creates a wake region of reduced velocity and possible recirculating flow.  Other flows can involve multiple phases, such as gas or vapour bubbles and solid particles in a liquid.  As the flow complexity increases, the prediction of flow feaures using computer models becomes increasingly more difficult. Experimental studies are used to improve our understanding of  complex flows, often with the long term goal of being able to predict them for engineering applications.  Measurement of the velocity field in complex turbulent flows presents a special challenge.  In order to capture the small-scale fluctuations of the velocity field, the instrument used to measure the velocity field must be capable of multi-component resolution of the instantaneous velocity field.  One research tool that accomplishes this task is a laser doppler anemometer (or LDA) system.  This equipment uses multiple laser beams to effectively measure the local velocity in a flow.  The present research grant will upgrade the processor of an exisitng LDA system at the University of Saskatchewan, which will then be used to study a wide range of fundamental and applied flows including: a turbulent boundary layer on a rough surface; a wall jet; the complex wake behind a short stack in a cross-flow; Taylor bubbles rising in a liquid; falling annular films.

在工业和/或环境应用中遇到的大多数流动都是湍流，也就是说，它们的特征是与速度场中明显随机的小尺度波动相关的混合水平增强。湍流具有许多重要的实际应用，包括增加表面摩擦阻力和增加壁面传热率。除了湍流之外，流动还可以表现出其他复杂性来源，例如，流体从外表面分离，然后产生速度降低的尾流区和可能的再循环流。其他流动可能涉及多相，例如液体中的气体或蒸汽气泡和固体颗粒。随着流动复杂性的增加，使用计算机模型预测流动特征变得越来越困难。实验研究是用来提高我们对复杂流动的理解，通常具有能够预测它们用于工程应用的长期目标。测量复杂湍流中的速度场是一个特殊的挑战。为了捕获速度场的小尺度波动，用于测量速度场的仪器必须能够对瞬时速度场进行多分量分辨。完成这一任务的一种研究工具是激光多普勒风速计（该仪器利用多束激光有效地测量气流中的局部速度。本研究拨款将提升萨斯喀彻温大学的激光多普勒分析系统的处理器，然后利用该系统研究各种基本和应用的气流，包括：粗糙表面上的湍流边界层;壁面射流;横流中短叠层后面的复杂尾流;液体中上升的泰勒气泡;下降的环形膜。