Multi-exposed recordings for 3D Lagrangian particle tracking with Multi-Pulse Shake-The-Box
Multi-exposed recordings for 3D Lagrangian particle tracking with Multi-Pulse Shake-The-Box
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DOI：
10.1007/s00348-019-2692-7
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发表时间：
2019-02
影响因子：
2.4
通讯作者：
M. Novara;D. Schanz;R. Geisler;S. Gesemann;C. Voss;A. Schröder
中科院分区：
文献类型：
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作者：
M. Novara;D. Schanz;R. Geisler;S. Gesemann;C. Voss;A. Schröder
AbstractThe最近推出的多脉冲摇箱（MP-STB）方法打开了可能性，扩展三维拉格朗日粒子跟踪（LPT）的调查高速流，其中长时间分辨序列的记录是目前无法获得由于有限的采集频率的高速系统。MP-STB技术利用迭代方法来克服由多脉冲记录序列提供的短观察时间所带来的限制。多脉冲序列通常通过同步多个照明系统以产生激光脉冲的突发来获得，其中时间间隔可以自由地向下调整到小于一微秒。可以采用几种策略来记录多脉冲序列;可以采用双相机系统将单个脉冲分离到相机帧上（通过偏振或定时），而使用多曝光帧允许采用单个成像系统，大大降低了实验设置的复杂性和成本。本文介绍了产生多脉冲记录序列的主要策略，并通过对三种湍流边界层流动的实验数据分析，讨论了MP-STB方法的应用和性能。结果表明，MP-STB技术在重建准确的跟踪领域，可以利用它来描述瞬时流结构，并产生高度空间分辨的统计数据，通过合奏平均在小箱子的能力。MP-STB的迭代重建和跟踪策略可以成功地适应多曝光帧的情况。结果表明，尽管双曝光粒子图像导致粒子图像密度增加，但采用多曝光记录有可能成为记录适用于高速流中拉格朗日粒子跟踪的多脉冲序列的首选技术。图形摘要
AbstractThe recent introduction of the Multi-Pulse Shake-The-Box (MP-STB) method opened the possibility of extending 3D Lagrangian particle tracking (LPT) to the investigation of high-speed flows, where long time-resolved sequences of recordings are currently not available due to the limited acquisition frequency of high-speed systems. The MP-STB technique makes use of an iterative approach to overcome the limitations posed by the short observation time offered by a multi-pulse recording sequence. Multi-pulse sequences are typically obtained by synchronizing multiple illumination systems to generate bursts of laser pulses where the time separation can be freely adjusted down to less than a microsecond. Several strategies can be adopted for the recording of multi-pulse sequences; a dual camera system can be adopted to separate the single pulses onto the camera frames (either by means of polarization or timing), while the use of multi-exposed frames allows for the employment of a single imaging system, largely reducing the complexity and cost of the experimental setup. The main strategies to generate multi-pulse recording sequences are presented here; the application and performances of the MP-STB method are discussed based on the analysis of experimental data from the investigation of three turbulent boundary layer flows at velocities ranging from 10 to approximately 30 m/s. Results show the capability of the MP-STB technique in reconstructing accurate track fields which can be exploited both to describe instantaneous flow structures and to produce highly spatially resolved statistics by means of ensemble average in small bins. The iterative reconstruction and tracking strategy for MP-STB can be successfully adapted to the case of multi-exposed frames. Results suggest that, despite the increase in particle image density resulting from the double-exposed particle images, the adoption of multi-exposed recordings has the potential to become the technique of choice for the recording of multi-pulse sequences suitable for Lagrangian particle tracking in high-speed flows.Graphical abstract