3-D flow imaging using a MHz-rate pulse burst LASER system
3-D flow imaging using a MHz-rate pulse burst LASER system
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发表时间：
2010
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通讯作者：
B. Thurow;K. Lynch;S. Williams;M. Melnick
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作者：
B. Thurow;K. Lynch;S. Williams;M. Melnick
在过去十年中，脉冲爆发激光系统的发展取得了重大进展，这些系统能够产生重复率超过1兆赫的高能激光脉冲。这些独特的激光系统目前正被用于各种领域的实验，从传统的流体动力学到燃烧再到等离子体物理。这里描述了一种用于三维流动可视化的这样的系统的使用，其中使用检流计扫描镜扫描通过流场的高重复频率的激光薄片，并使用高速相机获取流动图像。然后，从得到的2-D图像堆叠重建3-D图像。使用现有的仪器，可以在136微秒内获得220x220x68像素分辨率的图像，主要限制是可用的高速相机的速度和分辨率。通过在湍流射流和湍流边界层中进行的三维流动可视化实验，说明了该技术的优越性。湍流射流近场的三维烟雾可视化图像描述了在射流的轴对称剪切层中形成的环状涡和流向涡之间复杂的三维相互作用。湍流边界层图像显示了边界层外层存在的大尺度结构的三维性质，并为未来更详细的实验奠定了基础。
Over the past decade significant strides have been made in the development of pulse burst laser systems capable of producing high energy laser pulses at repetition rates in excess of 1 MHz. These unique laser systems are currently being used in experiments across a variety of fields ranging from traditional fluid dynamics to combustion to plasma physics. Described here is the use of one such system for 3-D flow visualization whereby a high-repetition rate laser sheet is scanned through the flow field using a galvanometric scanning mirror and flow images are acquired using a high-speed camera. 3-D images are then reconstructed from the resulting stack of 2-D images. Using existing instrumentation, images with 220 x 220 x 68 pixel resolution can be acquired in 136 microseconds with the primary limitation being the speed and resolution of an available high-speed camera. The strength of the technique is illustrated through 3-D flow visualization experiments conducted in a turbulent jet and a turbulent boundary layer. 3-D smoke visualization images of the near-field of a turbulent jet depict the complex 3-D interaction between ring vortices and streamwise vortices that form in axisymmetric shear layer of the jet. Turbulent boundary layer images show the 3-D nature of large-scale structures present in the outer layer of the boundary layer and lay the ground work for more detailed future experiments.