作者谨此致谢香港研究资助局 (否。GRF526913), 香港创新科技委员会 (不。ITS/334/15FP), 美国海军研究局全球办事处 (不。N00014-16-1-2161) 提供财政支持。

1. 风洞设置
<ol><li>三角洲机翼模型
	<ol>
<li>构造一个三角翼模型从铝, 以扫角φ 75°, 弦长度c 280 毫米, 根跨度b 150 毫米和厚度5毫米。在35°上有两个前导边斜面以修复分离点17 (请参见图 1a)。</li>
	</ol></li>
	<li>风洞设施
	<ol>
<li>在闭环低速风洞中进行实验, 测试部分为2.4 米 (长度) x 0.6 米 (宽) x 0.6 米 (高度), 装有玻璃墙, 允许在实验期间进行光学访问。这种设施的湍流强度应小于0.4%。 注: 在本研究中, 我们采用了香港理工大学的风洞, 具有上述特点。此外, 流速度U∞ 从2.64 米/秒到10.56 米/秒不等, 对应于雷诺数, Re, 从 5 x 104到 2 x 105, 基于三角翼的弦长, 这是典型的飞行范围。无人飞行器 (无人机)。</li>
		<li>根据需要, 使用三种不同的安排 (请参见激光片和照相机的图 1bd), 以观察纵向剖面、跨距截面和横断面的流动结构。安装程序的示意图显示在图 1b中。 注: 本协议详细说明了纵向剖面的设置和测量。</li>
	</ol></li>
	<li>安装三角翼
	<ol>
<li>修正三角翼尾缘上的刺, 这是在一个圆形运动指南用于调整攻击角度 (农产品), α。圆形导轨的中心位于风洞试验区的中心线上。因此, 三角洲机翼的中心始终可以在测试部分的中心。将 "农产品" 调整为α = 34°。</li>
		<li>仔细调整三角洲机翼模型, 以尽量减少任何偏航角和滚动角度, 通过检查读数的角度表和三轴激光水平。在目前的研究中, 这两个角度的不确定性小于0.1°。</li>
	</ol></li>
	<li>设置激光片
	<ol>
<li>分别使用两个激光器来阐明 PIV 测量和烟雾流动可视化的流动结构。<ol>
<li>对于 PIV 测量, 使用双脉冲激光器, 波长为532毫微米和最大能量为600兆焦耳 (可调) 为每个脉冲。用晶体管晶体管逻辑 (TTL) 信号的同步器控制它 (请参见图 1b)。</li>
			<li>对于烟雾流动可视化, 使用波长为 532 nm 的连续激光器, 功率为 1 W。这种连续激光器独立工作。在安装过程中, 使用10% 透射率的中性密度滤波器对激光束进行安全过滤。</li>
		</ol>
</li>
		<li>佩戴合适的激光护目镜。</li>
		<li>调整反射镜, 将激光束引入风洞中。激光光轴与镜面之间的夹角为, 使激光束垂直于三角洲机翼表面. <img alt="Equation 1" src="/files/ftp_upload/57244/57244eq1.jpg"> </img>确保激光束位于x/c ≅0.25 的位置, 稍后将成为视图领域的中心 (FOV)。</li>
		<li>安装激光光学 (与连续激光, 首先) 形成激光片, 如图 1b所示。凸透镜用于控制激光束的尺寸 (也适用于板厚)。圆柱透镜将激光束扩展到激光片上。 注: 在目前的研究中, 圆柱透镜的焦距为700毫米, 圆柱透镜的直径为12毫米。</li>
		<li>通过测量模型上的激光线, 检查激光片的厚度。如果激光片厚度不合适, 调整凸透镜的位置 (在这里, 大约1毫米, 以有效宽度的激光片在测试部分大约100毫米)。注意, 激光片的厚度依赖于 1) 的速度分量在正常方向的激光片和 2) 的时间间隔之间的两个快照的 PIV 测量。</li>
		<li>在三角翼上放置一个校准目标板, 其表面与激光片重合。这一步是必不可少的, 因为 FOV 在目前的研究是不正交的风洞坐标。</li>
	</ol></li>
	<li>摄像头设置
	<ol>
<li>设置相机时关掉激光器。与激光一样, 在这个实验的每个单独的部分使用两个摄像头:<ol>
<li>对于 PIV 测量, 请使用一个分辨率为 2048年 x 2048 像素的高速 CCD 摄像机。此摄像机由同步器和双脉冲激光器控制 (请参阅图 1b)。此相机中的数据将直接传送到计算机。</li>
			<li>对于烟雾流可视化, 在烟雾流可视化过程中, 使用具有 4000 x 6000 像素快照分辨率的商用数码相机和 50 Hz 视频记录分辨率 720 x 1280 像素。它将手动操作。</li>
		</ol>
</li>
		<li>移动相机的位置 (商用数码相机, 首先), 以获得所需的 FOV。调整相机镜头, 聚焦在校准靶板上。请确保整个字段都是集中的。如果没有, 相机的坐标可能不是正交的校准目标板。因此, 请仔细调整相机的位置18。</li>
		<li>相机设置好后, 采取几帧。随后, 标定目标板的这些帧将用于校准实际尺寸和帧像素之间的比例因子, 并识别 xyz 坐标中的参考位置。然后, 卸下校准目标板。</li>
	</ol></li>
	<li>以低速 (例如, 3 米/秒) 打开风洞, 并将油粒子注入风洞。将气溶胶发生器的压力设置在2.5 巴, 并在三十年代对预播种流可视化方法进行操作。在此之后, 整个风洞将被均匀地播种与油颗粒在正常直径约1µm。 注: 在目前的研究中, 在烟气流动可视化中, 风洞中的估计油粒密度浓度约为; <img alt="Equation 2" src="/files/ftp_upload/57244/57244eq2.jpg">因此, 风洞中的总流量密度变化为. <img alt="Equation 3" src="/files/ftp_upload/57244/57244eq3.jpg"> </img></li>
	<li>PIV 软件设置
	<ol>
<li>用 piv 软件控制 piv 系统 (见材料表)。此软件可以命令同步器向激光器和照相机发送 TTL 信号, 如图 1b所示。</li>
		<li>将采样频率设置为5赫兹, 总采样数为500。PIV 帧之间的时间间隔为80µs. 请注意, 时间间隔取决于 FOV 和流速的大小。请确保两帧中的审讯区域有大约 50-75% 重叠。</li>
	</ol></li>
</ol>2. 运行实验
<ol><li>
改进的烟雾流动可视化
	<ol>
<li>以所需的流速度打开风洞 (U = 2.64 米/秒)。运行10分钟, 以稳定流速度。在Re = 5万, 流速度为U = 2.64 米/秒。</li>
		<li>打开连续激光器。使用数码相机捕捉流结构的 5-10 快照。</li>
		<li>检查激光片是否位于列芯的纵向截面上 (请参阅图 3中显示的典型结构)。如果是这样, 在三角洲机翼模型上标记这个位置, 作为以后 PIV 测量的参考;否则, 通过调整光学透镜来改变激光片的位置, 并在 1.4.6 1.5.3 的步骤后复位校准。</li>
		<li>查看这些图像并检查焦点和亮度。如果图像质量不理想, 则调整透镜的光圈或 ISO 设置。</li>
		<li>采取更多的快照 (通常大约 20) 和视频 (大约四十年代) 与正确的设置。关闭激光并将数据传输到计算机。</li>
	</ol>
</li>
	<li>
PIV 测量
	<ol>
<li>根据从步骤2.1.3 已知的引用位置和步骤2.1.5 中快照的结果, 选择一个有趣的区域 (x/c≈ 0.3) 作为 FOV, 在那里可以观察到涡流子结构。用双脉冲激光和 CCD 摄像机代替连续激光和数码相机进行 PIV 测量。</li>
		<li>重复步骤 1.4.6 1.5.3 记录 PIV 测量的校准。</li>
		<li>以所需的流速度打开风洞, U = 2.64 米/秒. 运行10分钟以确保流速度稳定。</li>
		<li>将双脉冲激光器调整到最高功率水平并待命。使用该软件启动100s 的数据获取。数据记录完成后, 关闭激光头。</li>
		<li>回顾软件中获取的图像, 检查激光片的分布、粒子密度 (每个所需的审问区域中通常有6-10 粒子)、焦点以及双帧之间的粒子位移 (25-50% 的审讯区域)。</li>
		<li>如果图像的质量令人满意, 如步骤2.2.5 中所述, 请将数据保存到 PC 的硬盘上, 然后通过重复上述步骤来运行其他情况。否则, 请重复步骤1.7 和 2.2, 并仔细调整安装程序。</li>
	</ol>
</li>
</ol>3. 数据处理
<ol><li>
改进的烟雾可视化 注意: 以下步骤 3.1. 1-3. 1.4, 是通过 MATLAB 代码自动完成的 (请参阅补充编码文件)。<ol>
<li>将视频转换为帧序列。将帧从 RGB 窗体转换为灰度。旋转框架使三角翼表面水平。为以后的处理选择感兴趣的区域 (图 2a)。</li>
		<li>调整亮度和对比度以突出显示流结构。应用自适应阈值将灰度图像转换为二进制图像 (图 2b)。</li>
		<li>将每列中的二进制值相加, 并查找总和突然更改的位置。此位置是涡流击穿位置 (图 2c)。</li>
		<li>记录涡流击穿位置及其相应的时间。因而可以获得击穿振荡的时间历史。</li>
		<li>使用像素-实际大小比例因子 (从图像中测量的步骤1.5.3 中的校准目标板), 将时间历史从像素转换为实际大小, 并识别参考位置。绘制故障振荡的时间历史记录。</li>
	</ol>
</li>
	<li>
PIV 测量
	<ol>
<li>运行 PIV 软件。使用步骤2.2.2 中获取的图像设置坐标的比例因子和参考位置。通过图像处理库预先处理获取的数据, 以突出显示粒子并减少噪音18。</li>
		<li>使用自适应审讯区域方法, 其最小网格大小为 32 x 32 像素, 最小重叠为50%。选择图像区域, 并为自适应交叉关联设置 3 x 3 向量验证。</li>
		<li>结果作为一个速度向量场, 其中蓝色向量是正确的向量, 绿色的是取代向量, 红色的是坏的向量。</li>
		<li>应用 3 x 3 移动平均验证方法, 通过比较邻域中的向量来估计局部速度。用邻居的平均值替换离邻居太远的向量。</li>
		<li>计算速度图中的矢量统计量, 以获取时间历史中的流特性,例如、时间平均速度、标准偏差和速度分量之间的相互关联。计算矢量图中的标量导数, 以证明流场的内部特征,例如、涡度、剪切应力和旋转强度。</li>
	</ol>
</li>
</ol>

<ol>
	<li>Smits, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Flow visualization: Techniques and examples. , (2012).</li><li>Barlow, J. B., Rae, W. H., Pope, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Low-speed wind tunnel testing. , (1999).</li><li>Merzkirch, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Flow visualization. , (1987).</li><li>Raffel, M., Willert, C. E., Wereley, S., Kompenhans, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Particle image velocimetry: A practical guide. , (2007).</li><li>Westerweel, J., Elsinga, G. E., Adrian, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+Image+Velocimetry+for+Complex+and+Turbulent+Flows.">Particle Image Velocimetry for Complex and Turbulent Flows.</a> Annu Rev Fluid Mech. 45 (1), 409-436 (2013).</li><li>Meinhart, C. D., Wereley, S. T., Santiago, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PIV+measurements+of+a+microchannel+flow.">PIV measurements of a microchannel flow.</a> Exp Fluids. 27 (5), 414-419 (1999).</li><li>Gursul, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Review+of+unsteady+vortex+flows+over+slender+delta+wings.">Review of unsteady vortex flows over slender delta wings.</a> J Aircraft. 42 (2), 299-319 (2005).</li><li>Gursul, I., Gordnier, R., Visbal, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unsteady+aerodynamics+of+nonslender+delta+wings.">Unsteady aerodynamics of nonslender delta wings.</a> Prog Aerosp Sci. 41 (7), 515-557 (2005).</li><li>Lowson, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Some+experiments+with+vortex+breakdown.">Some experiments with vortex breakdown.</a> JRoy Aeronaut Soc. 68, 343-346 (1964).</li><li>Payne, F. M., Ng, T., Nelson, R. C., Schiff, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+and+wake+surveys+of+vortical+flow+over+a+delta+wing.">Visualization and wake surveys of vortical flow over a delta wing.</a> AIAA J. 26 (2), 137-143 (1988).</li><li>Lowson, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+three+dimensional+vortex+sheet+structure+on+delta+wings.">The three dimensional vortex sheet structure on delta wings.</a> Fluid Dynamics of Three-Dimensional Turbulent Shear Flows and Transition. , 11.11-11.16 (1989).</li><li>Riley, A. J., Lowson, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+three-dimensional+free+shear+layer.">Development of a three-dimensional free shear layer.</a> J Fluid Mech. 369, 49-89 (1998).</li><li>Menke, M., Gursul, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unsteady+nature+of+leading+edge+vortices.">Unsteady nature of leading edge vortices.</a> Phys Fluids. 9 (10), 2960 (1997).</li><li>Yayla, S., Canpolat, C., Sahin, B., Akilli, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Yaw+angle+effect+on+flow+structure+over+the+nonslender+diamond+wing.">Yaw angle effect on flow structure over the nonslender diamond wing.</a> AIAA J. 48 (10), 2457-2461 (2010).</li><li>Menke, M., Gursul, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nonlinear+response+of+vortex+breakdown+over+a+pitching+delta+Wing.">Nonlinear response of vortex breakdown over a pitching delta Wing.</a> J Aircraft. 36 (3), 496-500 (1999).</li><li>Sahin, B., Yayla, S., Canpolat, C., Akilli, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+structure+over+the+yawed+nonslender+diamond+wing.">Flow structure over the yawed nonslender diamond wing.</a> Aerosp Sci Technol. 23 (1), 108-119 (2012).</li><li>Kohlman, D. L., Wentz, J. W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vortex+breakdown+on+slender+sharp-edged+wings.">Vortex breakdown on slender sharp-edged wings.</a> J Aircraft. 8 (3), 156-161 (1971).</li><li>Lu, L., Sick, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-speed+Particle+Image+Velocimetry+Near+Surfaces.">High-speed Particle Image Velocimetry Near Surfaces.</a> J Vis Exp. (76), e50559 (2013).</li><li>Mitchell, A. M., Barberis, D., Molton, P., D&#233;lery, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oscillation+of+Vortex+Breakdown+Location+and+Blowing+Control+of+Time-Averaged+Location.">Oscillation of Vortex Breakdown Location and Blowing Control of Time-Averaged Location.</a> AIAA J. 38 (5), 793-803 (2000).</li><li>Shen, L., Wen, C. -. y., Chen, H. -. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asymmetric+Flow+Control+on+a+Delta+Wing+with+Dielectric+Barrier+Discharge+Actuators.">Asymmetric Flow Control on a Delta Wing with Dielectric Barrier Discharge Actuators.</a> AIAA J. 54 (2), 652-658 (2016).</li><li>Leibovich, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Structure+of+Vortex+Breakdown.">The Structure of Vortex Breakdown.</a> Annu Rev Fluid Mech. 10 (1), 221-246 (1978).</li><li>Mitchell, A. M., Molton, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vortical+Substructures+in+the+Shear+Layers+Forming+Leading-Edge+Vortices.">Vortical Substructures in the Shear Layers Forming Leading-Edge Vortices.</a> AIAA J. 40 (8), 1689-1692 (2002).</li><li>Gad-El-Hak, M., Blackwelder, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+discrete+vortices+from+a+delta+wing.">The discrete vortices from a delta wing.</a> AIAA J. 23 (6), 961-962 (1985).</li><li>Zhou, J., Adrian, R. J., Balachandar, S., Kendall, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+for+generating+coherent+packets+of+hairpin+vortices+in+channel+flow.">Mechanisms for generating coherent packets of hairpin vortices in channel flow.</a> J. Fluid Mech. 387, 353-396 (1999).</li><li>Adrian, R. J., Christensen, K. T., Liu, Z. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+and+interpretation+of+instantaneous+turbulent+velocity+fields.">Analysis and interpretation of instantaneous turbulent velocity fields.</a> Exp Fluids. 29 (3), 275-290 (2000).</li><li>Yoda, M., Hesselink, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+three-dimensional+visualization+technique+applied+to+flow+around+a+delta+wing.">A three-dimensional visualization technique applied to flow around a delta wing.</a> Exp. Fluids. 10 (2-3), (1990).</li><li>Greenwell, D. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> RTO AVT Symposium. , (2001).</li><li>Furman, A., Breitsamter, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Turbulent+and+unsteady+flow+characteristics+of+delta+wing+vortex+systems.">Turbulent and unsteady flow characteristics of delta wing vortex systems.</a> Aerosp Sci Technol. 24 (1), 32-44 (2013).</li><li>Wang, C., Gao, Q., Wei, R., Li, T., Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+flow+visualization+and+tomographic+particle+image+velocimetry+for+vortex+breakdown+over+a+non-slender+delta+wing.">3D flow visualization and tomographic particle image velocimetry for vortex breakdown over a non-slender delta wing.</a> Exp Fluids. 57 (6), (2016).</li></ol>

作者没有什么可透露的。

本文介绍了两种流动可视化方法, 改进了烟气流动可视化和 PIV 测量, 对三角洲机翼的流动结构进行了定性和定量的研究。对实验的一般程序进行了逐步的描述。这两种方法的设置几乎相同, 而所涉及的设备则不同。这两种流动可视化方法的基本原理是通过激光片来照亮流动中的粒子。改进后的烟气流动可视化可以同时获得全局流结构和小局部结构, 有助于获得未知流结构的概述。定量 PIV 分析提供了一个有趣的流场的详细的矢量图。因此, 结合这些流动可视化方法可以显著提高研究效率。
与普通排烟线的可视化相比, 该方法具有较好的效果。由于粒子是均匀分布的, 所以很容易识别出小流量结构。在复杂的三维流中, 该方法允许在任意空间位置设置激光片, 观察不同剖面上的流场, 而在传统的烟丝法中, 激光片必须始终与烟雾对齐。方向和观察窗口相应地被限制26。此外, 这种改进的方法不应该错过任何流动细节造成的烟雾在一些地区的烟雾线实验。然而, 由于如何进行播种, 这种方法不适用于开环风洞设施。应仔细分析流可视化数据, 以避免虚光照3、27的陷阱。
由于三角洲机翼上的流场高度为三维, 对任何扰动都很敏感, 因此建议使用非侵入性调查21。对于平面测量, 必须考虑在 PIV 测量过程中观测平面上的正交速度分量28,29。在这种情况下, 两个帧和激光片厚度之间的时间间隔应与正交速度折衷, 以确保大多数粒子不移出激光片。对于类似的测量, 建议先运行几个不同的设置参数, 以确定最适合的情况。
本文介绍的流量可视化方法方便、高效、成本低廉。今后, 这些技术将应用于具有主动流控制的复杂流场, 如钝体减阻和涡结构相互作用, 快速评价控制效果, 了解控制机制, 加快优化控制参数。

通过可视化技术进行流场测量是流体工程的基本方法。在不同的可视化技术中, 风洞实验中的烟线流动可视化和水隧道实验中的染料可视化, 是对渗流结构进行定性描述的最广泛的应用。PIV 和激光多普勒测速技术 (LDA) 是两种典型的定量技术 1.
在烟雾线流动可视化中, 烟雾 streaklines 是由加热导线上的油滴产生的, 或在实验过程中从外层烟雾发生器/容器中注入。大功率灯或激光片用于照亮烟雾 streaklines。然后记录图像以进行进一步分析。这是一个简单但非常有用的流可视化方法2。然而, 这种方法的有效性可能受到各种因素的限制, 如烟线的短时间, 复杂的三维流场, 相对较高的流速和烟雾产生的效率3。
在 PIV 测量中, 带有气流粒子的流场的剖面由激光片照亮, 在这个剖面中粒子的瞬时位置被高速相机捕获。在极小的时间间隔内, 记录一对图像。通过将图像分割成一个审讯区网格, 通过交叉相关函数计算审讯区域内粒子的平均运动, 可以得到观测到的剖面上的瞬时速度矢量图。然而, 也知道, 必须达成妥协的因素, 包括观察窗口的大小, 速度图的分辨率, 平面的速度大小, 对图像的时间间隔, 正交速度大小和粒子密度4。因此, 可能需要进行许多探索性实验以优化实验设置。用 PIV 测量单独的5、6来调查未知和复杂的流场将是昂贵且耗时的。针对上述问题, 提出了一种结合烟气流动可视化和 PIV 测量的策略, 并在此基础上对细长三角洲机翼上的复杂流动进行了研究。
在三角洲机翼上进行的比对列的大量研究已经进行了7、8, 并使用流可视化技术作为主要工具。许多有趣的流现象被观察到: 螺旋型和气泡式涡击穿9,10, 不稳定剪切层子结构11,12, 列弗击穿位置的振荡13, 以及俯仰和偏航角度14、15、16在流结构上的影响。然而, 三角洲翼流中某些不稳定现象的基本机制仍然不清楚7。在这项工作中, 烟雾流动可视化的改进使用相同的播种粒子用于 PIV 测量, 而不是烟雾线。这种改进大大简化了可视化的操作, 提高了图像的质量。基于改进的烟气流动可视化结果, PIV 测量主要集中在感兴趣的流场上获取定量信息。
本文详细介绍了如何在风洞中进行流动可视化实验, 并研究了三角洲机翼上的非恒定流现象。本实验将两种可视化方法、改进的烟气流动可视化和 PIV 测量相结合使用。该过程包括设备设置和参数调整的分步指导。典型的结果表明, 结合这两种方法来测量复杂的流场的空间和世俗的优势。

<table>
	<tbody>
		<tr>
			<td>532 nm Nd:YAG laser</td>
			<td>Quantel Laser</td>
			<td>Evergreen 600mJ</td>
			<td></td>
		</tr>
		<tr>
			<td>High speed camera</td>
			<td>Dantec Dynamic</td>
			<td>HiSense 4M</td>
			<td></td>
		</tr>
		<tr>
			<td>camera lens</td>
			<td>Tamron</td>
			<td>SP AF180mm F/3.5 Di</td>
			<td></td>
		</tr>
		<tr>
			<td>PIV recording and processing software</td>
			<td>Dantec Dynamic</td>
			<td>DynamicStudio</td>
			<td></td>
		</tr>
		<tr>
			<td>cylindrical lens</td>
			<td>Newport</td>
			<td></td>
			<td>&#934;=12 mm</td>
		</tr>
		<tr>
			<td>convex lens</td>
			<td>Newport</td>
			<td></td>
			<td>f=700 mm</td>
		</tr>
		<tr>
			<td>neutral density filter</td>
			<td>Newport</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Calibration target</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>aerosol generator</td>
			<td>TSI</td>
			<td>TSI 9307-6</td>
			<td></td>
		</tr>
		<tr>
			<td>PULSE GENERATOR</td>
			<td>Berkeley Nucleonics Corp</td>
			<td>BNC 575</td>
			<td></td>
		</tr>
		<tr>
			<td>continuous laser</td>
			<td></td>
			<td>APGL-FN-532-1W</td>
			<td></td>
		</tr>
		<tr>
			<td>Digital camera</td>
			<td>Nikon</td>
			<td>Nikon D5200</td>
			<td></td>
		</tr>
		<tr>
			<td>Image processing</td>
			<td>Matlab</td>
			<td></td>
			<td>custom code</td>
		</tr>
		<tr>
			<td>wind tunnel support</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>laser level</td>
			<td>BOSCH</td>
			<td>GLL3-15X</td>
			<td></td>
		</tr>
		<tr>
			<td>angle meter</td>
			<td>BOSCH</td>
			<td>GAM220</td>
			<td></td>
		</tr>
	</tbody>
</table>

experimental investigation of the flow structure over a delta wing via flow visualization methods

众所周知, 三角洲机翼上的流场由一对反旋转前缘涡 (列列) 控制。然而, 他们的机制还没有得到很好的理解。流场可视化技术是一种很有前途的非侵入性方法, 可以在空间和世俗上说明复杂的流动。一个基本的流可视化设置由高功率的激光和光学透镜组成, 用于生成激光片、照相机、示踪粒子发生器和数据处理器。风洞的设置, 所涉及的设备的规格, 以及相应的参数设置取决于要获得的流量特征。
正常的烟线流动可视化使用烟线来证明流动 streaklines。然而, 在复杂流场中, 由于空间分辨率差, 该方法的性能受到限制。为此, 研制了一种改进的烟气流动可视化技术。该技术同时说明了大规模的全球列流场和小尺度剪切层流结构, 为以后详细的粒子图像测速 (PIV) 测量提供了宝贵的参考。
本文介绍了改进的烟气流动可视化和 PIV 测量在三角洲机翼非恒定流现象研究中的应用。列举了风洞安装、数据采集、数据处理等实验过程和注意事项。结果表明, 这两种流动可视化方法是对三维流场进行定性和定量研究的有效方法。

图 2d显示了列在分解位置的时间历史记录。黑色曲线表示左舷, 红色曲线指示右舷列列。时间尺度由自由流速度和弦长 nondimensionalized。这两次历史的相关系数为r = −0.53, 表明了列的击穿位置振荡的强反对称相互作用。此结果与其他13、19、20的工作很好地吻合。
图 3显示了在α = 34°和Re = 7.5万的纵向剖面上的列列流结构。原始图像由数码相机以 RGB 形式捕获, 曝光时间为1/500 秒。在这个图中, 坐标是由三角形翼弦长度正常化的。在右上角绘制10毫米刻度以供参考。结果清楚地证明了主列芯, 它从三角洲机翼尖端发展成一条直线的下游。在x = 0.19 c的位置附近, 漩涡核心突然膨胀。这被称为前缘涡击穿9,21。在击穿位置之后, 唤醒变得混乱。在主列的核心是小涡流结构。这些子结构起源于前缘和漩涡围绕主要漩涡核心内滚动剪切层12,22,23。当子结构进入列列的内层时, 它们的形状由于靠近涡核的纵向方向相对较高的速度分量而拉伸。实验中指出, 除了在列的击穿位置, 列列的流动结构是相当固定的。结果表明, 这种烟气流动可视化方法能在局部小流量结构与全球流动结构演化之间取得较好的平衡。
图 4显示了从 PIV 测量中捕获的 64 x 64 像素区域中的典型粒子图像。在 A 帧的 32 x 32 像素审讯区域中, 有10个被识别的粒子, 由黄色圆圈标记。在两帧之间的时间间隔后, 这些粒子会偏移到新的位置, 如框架 B 所示。流离失所问题大约是审讯区的一季度, 造成这些审讯区之间几乎70% 的重叠。此外, 几乎所有的粒子都留在激光片平面中, 这表明安装参数是适当的选择了这种情况下。
图 5显示了流向和展剖面中的时间平均 PIV 结果。在进行这些测量之前, 进行了改进的烟气流动可视化, 以确定主要涡核位置, 步骤 2.1.1 2.1.3。图 5中的坐标由增量翼和弦长度c和本地 semispan 长度L进行规范化。涡度被规范化为ω * = ωU∞/ <img alt="Equation 4" src="/files/ftp_upload/57244/57244eq4.jpg"> c。根据这一结果, 由正、负 vorticities 的拐点可以很容易地识别出主涡核, 并由黑色虚线标记。在上部和底部区域, 滚动剪切层显示大 vorticities。λci 标准24,25用于从 PIV 测量中识别涡。在图 5中, 实线说明了局部旋转强度低于零的区域, 表明存在涡旋。在核心附近, 子结构被舒展并且不出现在旋转的力量外形。然而, 集中的涡度轮廓仍然建议在这里的子结构, 由白色虚线标记。在图 5b中, 速度矢量图清楚地表明, 在每一侧, 流在前缘处分离, 形成一个强剪切层, 随后滚入列芯。流向剖面的流动结构互补, 展流结构清楚地显示出外涡流子构造的演化。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57244/57244fig1.jpg"> 图 1: 设置的示意图。(a)三角洲机翼模型;(b d)设置用于在纵向剖面、展剖面和横向横断面上进行 PIV 测量。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57244/57244fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57244/57244fig2.jpg"> 图 2: 测量列的分解位置。(a)烟雾流动可视化结果, 显示横向横断面的前缘涡结构: α = 34°和Re = 5万;标记区域旋转并进一步处理。(b) (a) 中标记区域的二进制图像, 明确显示列芯和击穿。(c)对二进制图像 (b) 中的每一列求和, 以及在流向方向 (x 方向) 上确定的, 按弦长c正常化的已识别的弗里分解位置。(d)列列细分位置的时间历史记录。是时间平均位置, 是时间平均位置的即时距离. <img alt="Equation 5" src="/files/ftp_upload/57244/57244eq5.jpg"> <img alt="Equation 6" src="/files/ftp_upload/57244/57244eq6.jpg"><a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57244/57244fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57244/57244fig3.jpg"> 图 3: 纵向横断面上的前缘涡结构α = 34°和Re = 7.5万, 从烟雾流可视化中获得.<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57244/57244fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57244/57244fig4.jpg"> 图 4:64 x 64 像素区域中的粒子图像.相应的审讯区域为 32 x 32 像素。帧 A 和 B 之间的时间间隔为80微秒。原始审讯区中的识别粒子被黄色圆圈标记。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57244/57244fig4large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57244/57244fig5.jpg"> 图 5: 时间平均值的 PIV 结果.(a) 无量纲涡度ω *轮廓, 用实心线标记在纵向剖面上的局部旋转强度小于零的区域。(b) 在x = 0.4c的展剖面上, 具有速度矢量的无量纲涡度ω *轮廓;坐标由本地 semispan 长度SL (α = 34°和Re = 5万) 规范化。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57244/57244fig5large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods at JoVE.com

Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods

在这里, 我们提出了一种通过改进的烟雾流可视化技术来观察三角洲机翼上非恒定涡流流的协议, 并研究了导致前缘涡击穿位置振荡的机制。

基于流动可视化方法的三角洲机翼流动结构实验研究

It is well known that the flow field over a delta wing is dominated by a pair of counter rotating leading edge vortices (LEV). However, their mechanism is ...

experimental-investigation-flow-structure-over-delta-wing-via-flow

Nanyang Technological University

Research

Education

JoVE Journal

JoVE Core

Civil Engineering

Mechanical Engineering

Engineering

Unit 1

Flow over Immersed Bodies

Force Vectors

SCIENTISTS IN ACTION

10.5K 次观看.  Hong Kong Polytechnic University. 在这里, 我们提出了一种通过改进的烟雾流可视化技术来观察三角洲机翼上非恒定涡流流的协议, 并研究了导致前缘涡击穿位置振荡的机制。

视频: Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods

Determining 3D Flow Fields via Multi-camera Light Field Imaging

In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and observed phenomena in fluid flows. Thus, a need exists for an accessible method capable of resolving three-dimensional (3D) data sets for a range of problems. We present a novel technique for performing quantitative 3D imaging of many types of flow fields. The 3D technique enables investigation of complicated velocity fields and bubbly flows. Measurements of these types present a variety of challenges to the instrument. For instance, optically dense bubbly multiphase flows cannot be readily imaged by traditional, non-invasive flow measurement techniques due to the bubbles occluding optical access to the interior regions of the volume of interest. By using Light Field Imaging we are able to reparameterize images captured by an array of cameras to reconstruct a 3D volumetric map for every time instance, despite partial occlusions in the volume. The technique makes use of an algorithm known as synthetic aperture (SA) refocusing, whereby a 3D focal stack is generated by combining images from several cameras post-capture 1. Light Field Imaging allows for the capture of angular as well as spatial information about the light rays, and hence enables 3D scene reconstruction. Quantitative information can then be extracted from the 3D reconstructions using a variety of processing algorithms. In particular, we have developed measurement methods based on Light Field Imaging for performing 3D particle image velocimetry (PIV), extracting bubbles in a 3D field and tracking the boundary of a flickering flame. We present the fundamentals of the Light Field Imaging methodology in the context of our setup for performing 3DPIV of the airflow passing over a set of synthetic vocal folds, and show representative results from application of the technique to a bubble-entraining plunging jet.

A technique for performing quantitative three-dimensional (3D) imaging for a range of fluid flows is presented. Using concepts from the area of Light Field Imaging, we reconstruct 3D volumes from arrays of images. Our 3D results span a broad range including velocity fields and multi-phase bubble size distributions.

通过多摄像头的光场成像的三维流场测定

In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and ...

科研

工程学

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains.

In this video we first describe fabrication and operation procedures of a surface acoustic wave (SAW) acoustic counterflow device. We then demonstrate an experimental setup that allows for both qualitative flow visualization and quantitative analysis of complex flows within the SAW pumping device.

制造，操作和表面声波驱动声逆流微流体流动可视化

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we ...

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.

A shear cell is developed for small-angle neutron scattering measurements in the velocity-velocity gradient plane of shear and is used to characterize complex fluids. Spatially resolved measurements in the velocity gradient direction are possible for studying shear-banding materials. Applications include investigations of colloidal dispersions, polymer solutions, and self-assembled structures.

测量材料在微流使用1-2面流小角中子散射

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

对于新材料的低温磁输运测量先进的实验方法

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

基于形状记忆调查Elastocaloric冷却过程和模型验证实验方法

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

湍流应用三维粒子跟踪测速:一喷流病例

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

Design and Use of a Full Flow Sampling System (FFS) for the Quantification of Methane Emissions

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas industry faces continued scrutiny for methane emissions from across the supply chain, due to methane&#39;s relatively high global warming potential (25-84x that of carbon dioxide, according to the Energy Information Administration). Currently, a variety of techniques of varied uncertainties exists to measure or estimate methane emissions from components or facilities. Currently, only one commercial system is available for quantification of component level emissions and recent reports have highlighted its weaknesses.
In order to improve accuracy and increase measurement flexibility, we have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases based on transportation emissions measurement principles. The FFS is a modular system that consists of an explosive-proof blower(s), mass airflow sensor(s) (MAF), thermocouple, sample probe, constant volume sampling pump, laser based greenhouse gas sensor, data acquisition device, and analysis software. Dependent upon the blower and hose configuration employed, the current FFS is able to achieve a flow rate ranging from 40 to 1,500 standard cubic feet per minute (SCFM). Utilization of laser-based sensors mitigates interference from higher hydrocarbons (C2+). Co-measurement of water vapor allows for humidity correction. The system is portable, with multiple configurations for a variety of applications ranging from being carried by a person to being mounted in a hand drawn cart, on-road vehicle bed, or from the bed of utility terrain vehicles (UTVs). The FFS is able to quantify methane emission rates with a relative uncertainty of &#177; 4.4%. The FFS has proven, real world operation for the quantification of methane emissions occurring in conventional and remote facilities.

Design and Use of a Full Flow Sampling System FFS for the Quantification of Methane Emissions

We have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases from across the natural gas supply chain.

设计和全流采样系统（FFS）的使用甲烷排放的量化

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas ...

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy (ATOM)

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the main trend in the advanced development of flow cytometry. Notably, adding high-resolution imaging capabilities allows for the complex morphological analysis of cellular/sub-cellular structures. This is not possible with standard flow cytometers. However, it is valuable for advancing our knowledge of cellular functions and can benefit life science research, clinical diagnostics, and environmental monitoring. Incorporating imaging capabilities into flow cytometry compromises the assay throughput, primarily due to the limitations on speed and sensitivity in the camera technologies. To overcome this speed or throughput challenge facing imaging flow cytometry while preserving the image quality, asymmetric-detection time-stretch optical microscopy (ATOM) has been demonstrated to enable high-contrast, single-cell imaging with sub-cellular resolution, at an imaging throughput as high as 100,000 cells/s. Based on the imaging concept of conventional time-stretch imaging, which relies on all-optical image encoding and retrieval through the use of ultrafast broadband laser pulses, ATOM further advances imaging performance by enhancing the image contrast of unlabeled/unstained cells. This is achieved by accessing the phase-gradient information of the cells, which is spectrally encoded into single-shot broadband pulses. Hence, ATOM is particularly advantageous in high-throughput measurements of single-cell morphology and texture &#8211; information indicative of cell types, states, and even functions. Ultimately, this could become a powerful imaging flow cytometry platform for the biophysical phenotyping of cells, complementing the current state-of-the-art biochemical-marker-based cellular assay. This work describes a protocol to establish the key modules of an ATOM system (from optical frontend to data processing and visualization backend), as well as the workflow of imaging flow cytometry based on ATOM, using human cells and micro-algae as the examples.

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy ATOM

This protocol describes the implementation of an asymmetric-detection time-stretch optical microscopy system for single-cell imaging in ultrafast microfluidic flow and its applications in imaging flow cytometry.

微流控成像流式细胞仪通过不对称检测时间延伸光学显微镜（ATOM）

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the ...

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 &#181;m-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

This paper presents a microfabrication methodology for surface ion traps, as well as a detailed experimental procedure for trapping ytterbium ions in a room-temperature environment.

利用 Microfabricated 表面离子阱捕获离子的实验方法

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due ...

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

流动辅助介: 一种低成本的制备高性能溶液可纳米线器件的方法

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...