Particle image velocimetry system upgrade

粒子图像测速技术（PIV）是一种实验流体动力学研究工具，能够同时测量数千个点的速度。 这是通过用光反射颗粒接种流并用激光产生的脉冲光照射流中的平面来实现的。 数码相机在很短的时间内获得了这架飞机的两幅图像。 对这些图像进行适当的处理，通过测量颗粒在两张图像之间移动的距离来揭示流体的速度。 有关速度场的详细资料，例如PIV所提供的资料，是解释流动特性和指导工程设备的智能设计决策的最有力工具。这项拨款的重点是扩展现有的PIV系统，以进行世界级的测量。 为了更全面地研究流动，重要的是测量流动中不同位置的速度变化。 这笔赠款将为我们现有的PIV设施增加必要的设备，以便同时在两架飞机上进行测量。 两个不同平面上的PIV测量之间的关系将允许提取信息，这在许多应用中将是首创。 目前正在进行或计划中的调查的例子是：气泡和颗粒的瞬态运动的壁附近，两相流管，粗糙壁湍流边界层测量，约束射流和壁射流。 这些流动在空气动力学、发电、环境扩散建模和许多其他工业过程中有应用。

Particle image velocimetry (PIV) is an experimental fluid dynamics research tool capable of measuring the velocity in a flow at several thousand points simultaneously.  This is achieved by seeding the flow with light-reflecting particles and illuminating a plane in the flow with pulsed light produced by a laser.  A digital camera acquires two images of this plane a very short time apart.  Proper processing of these images reveals the velocity of the fluid by measuring the distance travelled by the particles between the two pictures.  Detailed information about the velocity field, such as that provided by PIV, is the most powerful tool for interpreting flow behaviour and guiding intelligent design decisions for engineering equipment.The particular focus of this grant is to expand an existing PIV system to allow world-class measurements to be made.  To more completely characterise a flow, it is important to measure how the velocity changes from place to place in the flow.  This grant will add the necessary equipment to our existing PIV facilities to allow measurements to be made on two planes simultaneously.  Relationships between PIV measurements on two different planes will allow information to be extracted that will be the first of its kind in many applications.  Examples of investigations currently underway or being planned are: the transient motion of bubbles and particles near walls, two-phase flow in tubes, rough-wall turbulent boundary layer measurements, confined jets, and wall jets.  These flows have application in aerodynamics, power generation, environmental dispersion modelling, and many other industrial processes.