由于温迪张，Luuk吕贝尔斯，马克Miskin和米歇尔斯科尔为帮助准备实验样品许多有益的讨论和泣涕郭。这项工作是由下批准号:DMR-0820054美国国家科学基金会的MRSEC计划的支持。

1。快速成像设置（参见图1） <ol><li>首先设置一个垂直轨道沿该容器充满了被研究的流体可以自由移动，以调节冲击速度。流体离开该容器的底部通过一喷嘴，然后进入自由落下。对这项工作的下落高度从1-200厘米变化，得到的冲击速度V 0 =（0.4-6.3）±0.15米/秒。 </li><li>构造和安装框架保持水平冲击面，典型地为玻璃板，根据该倾斜的反射镜被定位为从底部可视化的压降的影响。 </li><li>将干净和光滑的玻璃板上的持有人。确保板被水平拉平。 </li><li>装载注射器泵上的垂直轨道。 </li><li>对液态金属的影响，放置一个透明纸扩散器的喷嘴，用于侧视成像的后面。同时，附加一个白色不透明纸注射器泵上，以产生反射的底部观察（ 见图1）。然后，找到喷嘴背后的光源。 </li><li>对于密集的悬挂冲击，没有扩散器是必要的。相反，只需将光源在成像平面的前面。 </li><li>用适当的焦距为所需的放大倍率和光学工作距离选择微距镜头。然后，镜头连接到相机上。 </li><li>将相机固定到三脚架和相机调整根据成像的角度（侧面或底部）的高度。 </li></ol> 2。样品制备<ol><li> 氧化的金属液的制备 <ol><li>店铺镓 - 铟共晶（EGAIN）在密封容器中。由于其熔点温度大约为15℃，EGAIN停留在液体状态在室温下进行。 </li><li>用移液管提取3毫升EGAIN从容器和其拉伸到一个亚克力板。等待30分钟的样品在空气中被完全氧化。作为一名conseque考，薄薄的一层皱纹的氧化皮完全覆盖样品表面。 </li><li>用盐酸（HCl，"注意"）不同浓度的预洗到的EGAIN样品和控制表面氧化。具体地说，剪切样品，而这是在酸浴，在60秒-1的剪切速率与流变仪。后剪切10分钟后，将样品中的表面氧化的电平达到平衡时，通过盐酸浓度15,18设置。 </li><li>这个预洗后，用塑料注射器用塑钢尖吸嘴，从浴中提取EGAIN。 </li><li>安装到注射器注射泵和准备实验。 </li></ol></li><li> 密集悬浮液的制备 <ol><li>切断商用注射器（4.5毫米或2.3毫米的半径）的端部，并用它作为圆柱形管用于分配的稠密的悬浮液。 </li><li>拉回活塞和装满水的注射器一路的开口端，进行SURE没有气泡夹带。 </li><li>把球形的ZrO 2或玻璃珠入注射器。与颗粒的沉淀，将水从喷嘴洒出。用颗粒填充注射器一路的开口端。受堵塞在重力作用下。 </li><li>用剃刀刀片从顶部移除多余的湿颗粒，以保持为此持平。 </li><li>翻转喷嘴把它安装到注射泵。表面张力将防止粒子脱落16。 </li></ol></li></ol> 3。校准之前收集视频，成像设备的参数必须设置和照明对准已被完成。此外，空间分辨率需要校准。 <ol><li>启动注射泵以20毫升/小时的速度从喷嘴压出的流体（液体金属或悬浮液）。 </li><li>等待流体从注射器分离，形成的压降和秋季f以使测试影响到玻璃基板上。 </li><li>调整相机的位置，包括它的垂直位置和图像定位，找到图示中的电脑显示器，连接到相机。修改的工作距离，安排该图像是在焦平面时，透镜的再现比固定为1:1。 </li><li>改变光圈大小，曝光时间和光照角度，以获得最佳的图像质量时，帧速率足够高（&gt; 6,000 fps）的图2（a）显示由相机拍摄对液体EGAIN和密集悬挂的典型形象。 </li><li>将尺子在视场（ 见图2（b））及通过计算有多少个像素跨越1厘米适合计算空间分辨率。确保有分辨率水平和垂直方向之间没有区别。 </li><li>遵循3个步骤来衡量密集悬挂滴堆积分数: <ol><li>测量耳鼻喉科的质量冲击后愤怒图示右侧（ 例如，通过让一滴落入一个量杯，可以准确称量）。 </li><li>然后，蒸发所有溶剂用加热器，并再次称重该图示以获得粒子的质量。 </li><li>计算颗粒和液体的体积来获得堆积分数。通常，该体积分数应为60％左右。 </li></ol></li><li>根据观察方向（底部或侧部），适当地定位相机。特别是，把旁边的基材为侧视图或在反射镜底部成像的同样水平的照相机。 </li></ol> 4。视频录制和数据采集<ol><li>成像校准后，重新启动注射泵。在同一时间，打开相机控制软件监控的影响的过程。 </li><li>设置后触发帧号在大约一半的视频长度。仔细观察当下降开始形成并手动trig的GER将相机对准拍摄瞬间跌落分离从喷嘴。数据记录之前执行一些实践的检验。 </li><li>后的数据被记录时，修剪下来的视频包含冲击的部分，并保存视频作为分析图像序列。 </li></ol> 5。图像后处理及分析<ol><li>使用边界检测方法来定位液体EGAIN的移动前，因为它的传播，其对应于平均像素值的急剧过渡（参见图3（A，B））。 </li><li>无论从底部和侧面图像，确定飞溅发病密集暂停。 </li><li>进行粒子跟踪算法来获取从图示转义（参见图3（c））的单个颗粒的痕迹。然后，计算出从该轨迹的喷射速度（ 图3（d））。 </li></ol>

<ol>
	<li>Chiechi, R. C., Weiss, E. A., Dickey, M. D., Whitsides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eutectic+Gallium-Indium+(EGaIn):+A+moldable+Liquid+Metal+for+Electrical+Characterization+of+Self-Assembled+Monolayers.">Eutectic Gallium-Indium (EGaIn): A moldable Liquid Metal for Electrical Characterization of Self-Assembled Monolayers.</a> Angew. Chem. Int. Ed. 47, 142 (2008).</li><li>Fukumoto, M., Huang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flattening+Mechanism+in+Thermal+Sprayed+Ni+Particles+Impinging+on+Flat+Substrate+Surface.">Flattening Mechanism in Thermal Sprayed Ni Particles Impinging on Flat Substrate Surface.</a> J. Thermal Spray Tech. 8, (1999).</li><li>Seerden, K. A., Reis, N., Evans, J. R., Grant, P. S., Halloran, J. W., Derby, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ink-Jet+Printing+of+Wax-Based+Alumina+Suspensions.">Ink-Jet Printing of Wax-Based Alumina Suspensions.</a> J. Am. Ceram. Soc. 84, 2514 (2004).</li><li>Derby, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inkjet+printing+ceramics:+From+drops+to+solid.">Inkjet printing ceramics: From drops to solid.</a> J. Eur. Ceram. Soc. 31, 2543 (2011).</li><li>Xu, L., Zhang, W. W., Nagel, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drop+Splashing+on+a+Dry+Smooth+Surface.">Drop Splashing on a Dry Smooth Surface.</a> Phys. Rev. Lett. 94, (2005).</li><li>Clanet, C., Beguin, C., Richard, D., Quere, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maximal+deformation+of+an+impacting+drop.">Maximal deformation of an impacting drop.</a> J. Fluid. Mech. 517, 199 (2004).</li><li>Yarin, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drop+Impact+Dynamics:+Splashing+Spreading,+Receding,+Bouncing.">Drop Impact Dynamics: Splashing Spreading, Receding, Bouncing.</a> Annu. Rev. Fluid Mech. 38, 159 (2006).</li><li>Chandra, S., Avedisian, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+collision+of+a+droplet+with+a+solid+surface.">On the collision of a droplet with a solid surface.</a> Proc. R. Soc. Lond. A. 432, 13-41 (1991).</li><li>Versluis, M. <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+imaging+in+fluids.">High-speed imaging in fluids.</a> Exp. Fluids. 54, 1458 (2013).</li><li>Thoraval, M. -. J., Takehara, K., Etoh, T. G., Thoroddsen, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drop+impact+entrapment+of+bubble+rings.">Drop impact entrapment of bubble rings.</a> J. Fluid Mech. 724, 234-258 (2013).</li><li>Thoroddsen, S. T., Takehara, K., Etoh, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micro-splashing+by+drop+impacts.">Micro-splashing by drop impacts.</a> J. Fluid Mech. 706, 560-570 (2012).</li><li>Thoroddsen, S. T., Etoh, T. G., Takehara, K. <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+imaging+of+drops+and+bubble.">High-speed imaging of drops and bubble.</a> Ann. Rev. Fluid Mech. 40, 257-285 (2008).</li><li>Driscoll, M., Stevens, C. S., Nagel, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thin+film+formation+during+splashing+of+viscous+liquids.">Thin film formation during splashing of viscous liquids.</a> Phys. Rev. E. 82, (2010).</li><li>Pregent, S., Adams, S., Butler, M. F., Waigh, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+impact+and+deformation+of+a+viscoelastic+drop+at+the+air-liquid+interface.">The impact and deformation of a viscoelastic drop at the air-liquid interface.</a> J. Non-Newtonian Fluid Mech. 166, 831 (2011).</li><li>Xu, Q., Brown, E., Jaeger, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+dynamics+of+oxidized+liquid+metal+drops.">Impact dynamics of oxidized liquid metal drops.</a> Phys. Rev. E. 87, (2013).</li><li>Peters, I. R., Xu, Q., Jaeger, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Splashing+onset+in+dense+suspension+droplets.">Splashing onset in dense suspension droplets.</a> Phys. Rev. Lett. 111, (2013).</li><li>Luu, L., Forterre, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drop+impact+of+yield-stress+fluids.">Drop impact of yield-stress fluids.</a> J. Fluid Mech. 632, 301 (2009).</li><li>Xu, Q., Oudalov, N., Guo, Q., Jaeger, H., Brown, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+oxidation+on+the+mechanical+properties+of+liquid+gallium+and+eutectic+gallium-indium.">Effect of oxidation on the mechanical properties of liquid gallium and eutectic gallium-indium.</a> Phys. Fluids. 24, (2012).</li><li>Turitsyn, K. S., Lai, L., Zhang, W. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asymmetric+Disconnection+of+an+Underwater+Air+Bubble:+Persistent+Neck+Vibrations+Evolve+into+a+smooth+Contact.">Asymmetric Disconnection of an Underwater Air Bubble: Persistent Neck Vibrations Evolve into a smooth Contact.</a> Phys. Rev. Lett. 103, (2009).</li><li>Miskin, M. Z., Jaeger, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Droplet+Formation+and+Scaling+in+Dense+Suspensions.">Droplet Formation and Scaling in Dense Suspensions.</a> Proc. Natl. Acad. Sci. U.S.A. 109, 4389-4394 (2012).</li><li>Royer, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Birth+and+growth+of+a+granular+jet.">Birth and growth of a granular jet.</a> Phys. Rev. E. 78, (2008).</li><li>Paulsen, J. D., Burton, J. C., Nagel, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viscous+to+Inertial+Crossover+in+Liquid+Drop+Coalescence.">Viscous to Inertial Crossover in Liquid Drop Coalescence.</a> Phys. Rev. Lett. 106, (2011).</li></ol>

作者什么都没有透露。

几个步骤是为快速成像的正确执行是至关重要的。首先，照相机和透镜必须进行适当的设置和校准。特别是，为了得到高的空间分辨率，该透镜的复制比例必须保持接近1:1。这是致密混悬剂的可视化特别重要。另外，孔径大小需要慎重选择用于成像。例如，观测从总体上侧需要一个较长的景深，因此较小的光圈尺寸。以保持视频的亮度，需要增加曝光时间，从而降低帧速率（〜6000帧）。相比之下...

落锤冲击到固体表面是在涉及电子制造1，喷涂2，和添加剂制造使用喷墨打印3,4，其中下降的精确控制扩散和飞溅需要许多应用中的关键过程。然而，直接观察的下落冲击，原因有二技术上具有挑战性。首先，这是发生的时间尺度内过短（约100微秒），也可以通过常规的成像系统，如光学显微镜和数码单反相机容易想像，一个复杂的动态过程。闪光照相罐的过程图像快得多，但不允许进行连续记录，根据需要为随时间的演变的详细的分析。第二，引起不稳定性的影响的长度规模可以小到10微米5。因此，定量研究的影响过程，结合超快成像以及合理的高空间分辨率的系统往往是所需。如果没有这样的制度，对液滴撞击早期的工作主要集中在6-8冲击后，全球的几何变形，但无法收集有关早期信息，以影响相关的非平衡过程，如飞溅的发作。在流体中9,12中的CMOS高速摄像的最新进展，推动了帧速率最高可达百万fps和曝光时间下低于1微秒。此外，新开发的CCD成像技术可以推动帧速率远高于百万FPS 9-12。另一方面空间分辨率，可提高到使用放大镜12 1微米/像素的顺序。因此，它已成为可能的空前细致的探讨范围广泛的物理参数对压降的影响不同阶段的影响，并系统地比较实验和理论5,13-16。例如，在牛顿流体飞溅转变是缶次由大气压力5进行设置，而本征的流变决定的屈服应力流体17的扩展动态。 这里提供一个简单但功能强大的快速成像技术被引入并应用于研究两种类型的非牛顿流体的冲击动力学:液态金属和密密麻麻的悬浮液。与暴露于空气中，基本上所有的液体金属（汞除外）会自发形成在其表面上的氧化皮。机械地，皮肤被发现以改变有效的表面张力和金属18的润湿能力。在过去的研究15，几个作者的研究传播过程定量，并能解释趋肤效应影响冲击动力学，与碰撞参数的最大扩散半径，特别是缩放。因为液态金属具有高的表面反射率，仔细调整照明的需要在成像。停学一再在液体组成的小颗粒。即使是简单的牛顿 ​​流体，增加了粒子效果在非牛顿流体特性，成为在密集的悬浮液， 即在悬浮颗粒的高体积分数尤为突出。特别是，在发病飞溅时悬挂液滴撞击光滑，坚硬的表面，研究了以前的工作16。这两种液体粒子与粒子间的相互作用可以从什么可能从简单的液体预期显著改变飞溅的行为。来跟踪颗粒小至80微米的在这些实验中，需要很高的空间分辨率。 各种技术要求，如高时空分辨率，以及对观察无论是从侧面和下方的影响的能力的组合，都可以满意这里所描述的成像设置。通过以下的标准协议，如下所述，冲击动力学可以是不变拟tigated以受控的方式，以明确示出用于扩展和飞溅的行为。

<table border="0" cellpadding="0" cellspacing="0" style="width:604px;" width="605">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:103px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gallium-Indium Eutectic</td>
			<td>Sigma Aldrich</td>
			<td>495425-25G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hydrochloric Acid&#160;</td>
			<td>Sigma Aldrich</td>
			<td>320331-2.5L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Zirconium oxide</td>
			<td>Glen Mills Inc.</td>
			<td>7200</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phantom V12 &#38; V7 Fast Ccamera</td>
			<td>Vision Research</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">105mm Micro-Nikon</td>
			<td>Nikon</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">12V/200W light Source</td>
			<td>Dedolight</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Syringe Pump</td>
			<td>RAZEL</td>
			<td>MODEL R9-9E</td>
			<td></td>
		</tr>
	</tbody>
</table>

fast imaging technique to study drop impact dynamics of non-newtonian fluids

在流体力学领域，许多动力学过程，不仅发生在一个很短的时间间隔，但也需要高空间分辨率的详细观测，场景，使其具有挑战性，观察其与传统的成像系统。其中之一是液体的落下冲击，这通常在毫秒的十分之一发生。为了应对这一挑战，快速成像技术被引入，结合了高速摄像机（可高达每秒一百万帧）的微距镜头具有长工作距离，使图像的空间分辨率降低到10微米/像素。成像技术使得相关的流体动力学数量时，如流场，扩散距离和飞溅速度的精确测量，从所记录的视频的分析。为了证明这种可视化系统的功能，当非牛顿流体液滴撞击到坚硬的平面上的冲击动力学是characterized。两种情况考虑:对于氧化液态金属液滴我们专注于传播行为，并密密麻麻悬浮我们判断飞溅的发生。更一般地，在这里介绍了高时空分辨率的成像相结合的优势，提供跨多种微尺度现象研究快速动态。

在快速成像技术可以被用于量化扩频和飞溅的各种影响的情况。 图4（a）中 ，例如，示出了具有不同氧化皮强度为液体EGAIN典型影响图像序列。通过从相同的喷嘴，并在同一高度落下喷射EGAIN，液滴具有可重复的冲击速度V 0 = 1.02±0.12米/秒和半径R 0 = 6.25±0.10毫米的生成。左栏显示的空气氧化EGAIN下降，酸不预洗的影响。形成一条长尾巴在下落的顶端，当流体从喷嘴分离...

Watch this Scientific Journal Video about Fast Imaging Technique to Study Drop Impact Dynamics of Non-Newtonian Fluids at JoVE.com

Fast Imaging Technique to Study Drop Impact Dynamics of Non-Newtonian Fluids

的非牛顿流体压降的影响是一个复杂的过程，因为不同的物理参数在很短的时间（毫秒的不到十分之一）影响的动态。一种快速成像技术以表征不同的非牛顿流体的冲击行为引入。

快速成像技术来研究非牛顿流体的跌落冲击动力学

In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for ...

fast-imaging-technique-to-study-drop-impact-dynamics-non-newtonian

Research

Education

JoVE Journal

JoVE Core

Engineering

Physics

Civil Engineering

Unit 1

Flow over Immersed Bodies

Fluid Mechanics

SCIENTISTS IN ACTION

12.2K 次观看.  The University of Chicago. 的非牛顿流体压降的影响是一个复杂的过程，因为不同的物理参数在很短的时间（毫秒的不到十分之一）影响的动态。一种快速成像技术以表征不同的非牛顿流体的冲击行为引入。 

视频: Fast Imaging Technique to Study Drop Impact Dynamics of Non-Newtonian Fluids

Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic (VES) fluids. The measurements are made for particles settling in unbounded fluids&#160;and fluids between parallel walls. VES fluids over a wide range of rheological properties are prepared and rheologically characterized. The rheological characterization involves steady shear-viscosity and dynamic oscillatory-shear measurements to quantify the viscous and elastic properties respectively. The settling velocities under unbounded conditions are measured in beakers having diameters at least 25x the diameter of particles. For measuring settling velocities between parallel walls, two experimental cells with different wall spacing are constructed. Spherical particles of varying sizes are gently dropped in the fluids and allowed to settle. The process is recorded with a high resolution video camera and the trajectory of the particle is recorded using image analysis software. Terminal settling velocities are calculated from the data.
The impact of elasticity on settling velocity in unbounded fluids is quantified by comparing the experimental settling velocity to the settling velocity calculated by the inelastic drag predictions of Renaud et al.1&#160;Results show that elasticity of fluids can increase or decrease the settling velocity. The magnitude of reduction/increase is a function of the rheological properties of the fluids and properties of particles. Confining walls are observed to cause a retardation effect on settling and the retardation is measured in terms of wall factors.

This paper demonstrates the experimental procedure to measure terminal settling velocities of spherical particles in surfactant-based shear thinning viscoelastic fluids. Fluids over a wide range of rheological properties are prepared and settling velocities are measured for a range of particle sizes in unbounded fluids and fluids between parallel walls.

无约束和封闭表面活性剂中球形粒子沉降速度的实验测量 剪切变薄粘性流体

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic ...

科研

工程学

Time Multiplexing Super Resolving Technique for Imaging from a Moving Platform

We propose a method for increasing the resolution of an object and overcoming the diffraction limit of an optical system installed on top of a moving imaging system, such as an airborne platform or satellite. The resolution improvement is obtained in a two-step process. First, three low resolution differently defocused images are being captured and the optical phase is retrieved using an improved iterative Gerchberg-Saxton based algorithm. The phase retrieval allows to numerically back propagate the field to the aperture plane. Second, the imaging system is shifted and the first step is repeated. The obtained optical fields at the aperture plane are combined and a synthetically increased lens aperture is generated along the direction of movement, yielding higher imaging resolution. The method resembles a well-known approach from the microwave regime called the Synthetic Aperture Radar (SAR) in which the antenna size is synthetically increased along the platform propagation direction. The proposed method is demonstrated through laboratory experiment.

A method for overcoming the optical diffraction limit is presented. The method includes a two-step process: optical phase retrieval using iterative Gerchberg-Saxton algorithm, and imaging system shifting followed by repetition of the first step. A synthetically increased lens aperture is generated along the direction of movement, yielding higher imaging resolution.

时间复用超解析技术成像的运动平台

We propose a method for increasing the resolution of an object and overcoming the diffraction limit of an optical system installed on top of a moving ...

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

通过硅直接晶圆粘接制造均匀纳米级腔

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.

We present a technique to achieve low-velocity to intermediate-velocity collisions between fragile dust aggregates in the laboratory. For this purpose, two vacuum drop-tower setups have been developed that allow collision velocities between &#60;0.01 and ~10 m/sec. The collision events are recorded by high-speed imaging.

实验室落塔的粉尘聚集在碰撞早期太阳系的实验模拟

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust ...

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

高压直流电桥从极地介电液的制备

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

烧蚀材料在试验过程中等离子体发生器发射光谱边界层研究

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Dynamic Pore-scale Reservoir-condition Imaging of Reaction in Carbonates Using Synchrotron Fast Tomography

Underground storage permanence is a major concern for carbon capture and storage. Pumping CO2 into carbonate reservoirs has the potential to dissolve geologic seals and allow CO2 to escape. However, the dissolution processes at reservoir conditions are poorly understood. Thus, time-resolved experiments are needed to observe and predict the nature and rate of dissolution at the pore scale. Synchrotron fast tomography is a method of taking high-resolution time-resolved images of complex pore structures much more quickly than traditional &#181;-CT. The Diamond Lightsource Pink Beam was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 &#181;m resolution over a period of 2 hours. The images were segmented and the porosity and permeability were measured using image analysis and network extraction. Porosity increased uniformly along the length of the sample; however, the rate of increase of both porosity and permeability slowed at later times.

Synchrotron fast tomography was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 &#181;m resolution over a period of 2 h.

用同步快速反应层析成像动态孔隙规模油藏条件下成像碳酸盐

Underground storage permanence is a major concern for carbon capture and storage. Pumping CO2 into carbonate reservoirs has the potential to dissolve ...

Dielectric RheoSANS &#8212; Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and microstructural properties of complex fluids is presented. The instrument consists of a Couette geometry contained within a modified forced convection oven mounted on a commercial rheometer. This instrument is available for use on the small angle neutron scattering (SANS) beamlines at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). The Couette geometry is machined to be transparent to neutrons and provides for measurement of the electrical properties and microstructural properties of a sample confined between titanium cylinders while the sample undergoes arbitrary deformation. Synchronization of these measurements is enabled through the use of a customizable program that monitors and controls the execution of predetermined experimental protocols. Described here is a protocol to perform a flow sweep experiment where the shear rate is logarithmically stepped from a maximum value to a minimum value holding at each step for a specified period of time while frequency dependent dielectric measurements are made. Representative results are shown from a sample consisting of a gel composed of carbon black aggregates dispersed in propylene carbonate. As the gel undergoes steady shear, the carbon black network is mechanically deformed, which causes an initial decrease in conductivity associated with the breaking of bonds comprising the carbon black network. However, at higher shear rates, the conductivity recovers associated with the onset of shear thickening. Overall, these results demonstrate the utility of the simultaneous measurement of the rheo-electro-microstructural properties of these suspensions using the dielectric RheoSANS geometry.

Dielectric RheoSANS &amp;#8212; Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids

Here, we present a procedure for the measurement of simultaneous impedance, rheology and neutron scattering from soft matter materials under shear flow.

介电RheoSANS  - 阻抗，流变性和复杂流体的小角中子散射的同时拷问

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

静态和扫描模式下中子伽马分析法测量土壤碳

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...

Film Control to Study Contributions of Waves to Droplet Impact Dynamics on Thin Flowing Liquid Films

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous studies on flowing liquid films have neglected the contributions of spatial structures of waves to the impact outcome, while this has recently been shown to have a significant influence on the drop impact dynamics. In this report, we outline a step-by-step procedure to investigate the effect of periodic inlet forcing of a flowing liquid film leading to the production of spatiotemporally regular wave structures on drop impact dynamics. A function generator in connection with a solenoid valve is used to excite these spatiotemporally regular wave structures on the film surface while the impact dynamics of uniform-sized droplets are captured using a high-speed camera. Three distinct regions are then studied; viz. the capillary wave region preceding the large wave peak, the flat film region, and the wave hump region. The effects of important dimensionless quantities such as film Reynolds, drop Weber and Ohnesorge numbers parameterized by the film flow rate, drop speed, and drop size are also examined. Our results show interesting, hitherto undiscovered dynamics brought about by this application of film inlet forcing of the flowing film for both low and high inertia drops.

A protocol to study the contributions of waves to droplet impact dynamics on flowing liquid films is presented.

薄膜控制研究波浪对液滴冲击动力学的影响薄流动液体薄膜

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous ...

Speed

Subtitles

快速成像技术来研究非牛顿流体的跌落冲击动力学