Name: an analog macroscopic technique for studying molecular hydrodynamic processes in dense gases and liquids
Uploaded: 2017-12-04T15:00:00
Description: Watch this Scientific Journal Video about An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids at JoVE.com

这项工作得到了海军研究办公室 (进货 N00014-15-1-0020) [Tkacik 和 Keanini] 的支持, 并在北卡罗莱纳大学在夏洛特的赛车研究实验室进行. 抛光介质由 Rosler 捐赠。

1. 振动系统的制备
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设置振动系统, 如图 1所示。这个系统由一个环形聚氨酯碗 (具有外径600毫米), 连接到一个单一的速度 (1740 rpm), 不平衡的马达, 后者产生的过程振动。这是附加到一个加权的基础, 并由一组八弹簧 (碗和加权基地被购买组装成一件)。将碗总成固定在它的支架上, 并用两个供应的橡皮钩连接。将蠕动泵放在靠近碗的桌子上, 并将泵出口软管连接到?...

<ol>
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Japan. 12, 570-586 (1957).</li><li>Kubo, R., Toda, M., Hashitsume, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical physics II: nonequilibrium statistical mechanics. , (1991).</li></ol>

为了将振动颗粒桩作为宏观的类似物用于研究分子流体动力学过程, 实验必须一方面学习和使用四基本测量, 另一方面, 掌握一些基本的平衡元素和非平衡统计力学。首先将重点放在实验测量上, 这些测量包括: i) 通过测量单粒子速度自相关函数的单个晶粒动力学, 二) 测量时间平均/长时间尺度的表面晶粒速度场, iii) 测量颗粒介质的有效粘度, iv) 测量介质碗的振动谱, 既空又充满介质。
<p class="jove...

分子流体力学研究的动力学和统计力学的个别分子和收集的分子在流体中。在研究分子水动力系统的许多实验技术中,1,2, 光散射1,2,3, 分子动态模拟4, 5、6、7以及在较小程度上, 非弹性中子散射8已被最常用。不幸的是, 后两种技术有很大的局限性。分子动力学 (MD) 模拟, 例如: i) 被限制到包含相对地少量分子的小空间和世俗域, ii) 需要使用近似的粒子间电位, iii) 通常引入周期性<img alt="Equation 1" src="/files/ftp_upload/56632/56632eq1.jpg"> <img alt="Equation 2" src="/files/ftp_upload/56632/56632eq2.jpg"> </img>边界条件, 在非平衡散流条件下无效, 和 iv) 目前不能回答的根本问题是如何分子尺度动力学, 涉及单一分子或分子集合, 受影响, 和夫妇回到, 散装, 非平衡流体流动。与中子散射有关的主要限制与获得有限数量的中子束源的困难有关。
为了为本文所提出的模拟实验技术提供背景, 我们着重介绍了光散射技术在简单稠密气体和液体状态流体中的应用。在典型的光散射实验中, 偏振激光光束被定向到含有固定流体样本的小审讯量。从样品中的分子中散射的光, 然后在相对于入射光束的固定角度检测。根据感兴趣的分子动力学机制, 散射光信号的检测和分析采用光滤波或光混合检测方法。正如伯尔尼和皮科拉1所概述的, 过滤技术, 它在时间尺度上探测流体状态分子动力学的短于, 引入了后向散射干涉仪或衍射光栅, 并允许扫描的频谱密度<img alt="Equation 3" src="/files/ftp_upload/56632/56632eq3.jpg">的散射光。光学混合技术, 用于慢时间尺度的动态, s, 相比之下, 合并后散射 autocorrelator 或频谱分析仪, 其中的散射信号的光谱内容从测量散射光提取<img alt="Equation 4" src="/files/ftp_upload/56632/56632eq4.jpg">强度.
一般而言, 激光探针, 至少在光谱的可见光范围内的探测器, 波长比液态态分子间的特征间距长得多。在这种情况下, 探头光束激发五集体, 慢时间尺度, 长波长度的水动力模式2,9,10 (相对于特征碰撞频率的慢速): 两个粘性阻尼, 反传播声波, 两个不耦合, 纯粹的扩散涡度模式, 和一个单一的扩散热 (熵) 模式。在入射光束的 (纵向) 方向上, 声模是兴奋的, 而涡模式在横向方向上是兴奋的。
考虑纯实验散射技术, 两个基本问题, 位于平衡的核心和非平衡统计力学的分子, 液体状态系统, 仍然超越光和中子散射测量: 1) 严格的参数9,11显示单个液态状态分子的随机、碰撞和次碰撞-时间尺度动力学, 无论是经典牛顿动力学还是量子动力学, 都可以在广义万方程 (GLE) 的形式。GLE 的, 反过来, 构成了一个中心的理论工具研究的非平衡的分子在稠密气体和液体的统计力学。不幸的是, 由于个体 (非大分子) 分子的动力学不能通过任何一种散射技术来解决, 目前还没有直接的方法, 除了 MD 模拟, 以测试 GLE 的有效性。 2) 一项基本假设位于宏观连续体流体动力学的核心, 以及微尺度分子流体力学, 假定在长度和时间尺度上相对于分子直径和碰撞时间大, 但相对于连续体小长度和时间尺度, 局部热力学平衡 (LTE) 盛行。在连续流和传热模型, 如 n-s-斯托克斯 (NS) 方程, LTE 假设是必需的9 , 以耦合本质上的非平衡, 连续尺度流和能量传输特征-像粘性剪应力和热传导-严格平衡热力学性质, 如温度和内部能量。同样, 虽然微尺度动量和能量传输本质上是非平衡过程, 反映了耦合的、微尺度的质量、动量和能量流的出现, 但这些微尺度过程的模型假设电流表示来自 LTE9的小扰动。再次, 据我们所知, 没有对 LTE 假设的直接实验测试。特别是, 似乎没有分子水动力学散射实验试图在稠密, 移动, 非平衡流体流动。
本文概述了用标准粒子成像测速仪 (PIV) 测量振动颗粒桩的宏观、单粒子和集体粒子动力学的模拟实验技术, 可用于间接预测,解释, 并暴露在稠密气体和液体的单和多分子流体力学。在我们的组12发布的最近一篇文章中, 介绍了启用该方法的物理和理论元素。实验上, 宏观系统必须表现: (一) 持续的趋势, 以局部, 宏观统计机械平衡, 和 (ii) 小, 线性偏离平衡, 模仿 (弱) 非平衡波动观察分子流体力学系统。从理论上讲: (一) 描述稠密、相互作用的 N 粒子系统的平衡和弱非平衡统计力学的经典微型模型必须以宏观形式进行重铸, (ii) 所产生的宏观模型必须可靠地预测单和多粒子动力学, 从短, 粒子碰撞-时间尺度到长, 连续流-时间尺度。
在这里, 我们提出了一个详细的实验协议, 以及代表性的结果得到了新的技术。与 MD 模拟和光和中子散射方法不同, 这项新技术首次允许对流动的、强烈的非平衡、稠密气体和液体中的分子流体力学过程进行详细研究。

<table>
	<tbody>
		<tr>
			<td>Vibratory Polishing Bowl</td>
			<td>Raytech</td>
			<td>AV-75</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Meter</td>
			<td>Peristaltic Pumps</td>
			<td>913 Mity Flex</td>
			<td></td>
		</tr>
		<tr>
			<td>Scale</td>
			<td>Pelouze</td>
			<td>4040</td>
			<td></td>
		</tr>
		<tr>
			<td>Triaxial Accelerometer</td>
			<td>PCB Piezotronics</td>
			<td>PCB 356B11</td>
			<td>Accelerometer with Sensor Signal Conditioner</td>
		</tr>
		<tr>
			<td>Data Acquisition Computer</td>
			<td>IBM</td>
			<td>Thinkpad</td>
			<td>Used with high speed camera</td>
		</tr>
		<tr>
			<td>High Speed Camera</td>
			<td>Redlake</td>
			<td>Motionxtra HG-XR</td>
			<td></td>
		</tr>
		<tr>
			<td>Zoom Lens</td>
			<td>Tamron</td>
			<td>Model A18</td>
			<td>18-250mm F/3.5-6.3&#160;</td>
		</tr>
		<tr>
			<td>High intensity Light</td>
			<td>ARRI</td>
			<td>EB 400/575 D</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Processing Computer</td>
			<td>Dell</td>
			<td>Dell Precision Tower 7910</td>
			<td></td>
		</tr>
		<tr>
			<td>PIV Software&#160;</td>
			<td>Dantec Dynamics</td>
			<td>Dynamic Studio 2013</td>
			<td>version 3.41.38</td>
		</tr>
		<tr>
			<td>Data Acquisition Hardware</td>
			<td>National Instruments</td>
			<td>SCXI</td>
			<td>SCXI-1000 Chasis with SCXI 1100 Card and SCXI 1303 Adapter</td>
		</tr>
		<tr>
			<td>Data Acquisition Software</td>
			<td>National Instruments</td>
			<td>LabVIEW 2012</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Processing Software</td>
			<td>MATHWORKS</td>
			<td>MATLAB</td>
			<td></td>
		</tr>
		<tr>
			<td>Polishing Media</td>
			<td>Rosler</td>
			<td>RSG 10/10S</td>
			<td>Multiple media types used (mixed, spherical, triangular)</td>
		</tr>
		<tr>
			<td>Polishing Solution</td>
			<td>Rosler</td>
			<td>FC KFL (3%)</td>
			<td>3% soap solution with water</td>
		</tr>
		<tr>
			<td>Ruled Scale</td>
			<td>Swiss Precision Instruments</td>
			<td>13-911-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Graduated Cylinder</td>
			<td>Global Scientific</td>
			<td>601082</td>
			<td></td>
		</tr>
	</tbody>
</table>

an analog macroscopic technique for studying molecular hydrodynamic processes in dense gases and liquids

本文介绍了一种研究稠密气体和液体中分子尺度流体力学过程的模拟、宏观方法。该技术适用于标准流体动态诊断, 粒子图像测速 (PIV), 以测量: i) 单个粒子 (晶粒) 的速度, 现存于短, 颗粒碰撞时间尺度, ii) 的速度系统的粒子, 在短碰撞时间-长, 连续流-时间尺度, iii) 在稠密分子流体中已知存在的集体水动力模式, 和 iv) 短期和长时间尺度的速度自相关函数, 中央了解粒子尺度动力学强相互作用, 稠密流体系统。基本系统由成像系统、光源、振动传感器、具有已知介质的振动系统以及 PIV 和分析软件组成。所需的实验测量和理论工具的概述, 当使用模拟技术来研究分子尺度的流体力学过程是突出的。该技术为传统用于分子流体力学研究的光子和中子束散射方法提供了一个相对简单的替代方案。

在介绍具有代表性的结果时, 我们指的是连续时间尺度过程, 它们是随着时间的推移而观察和预测的, 相对于特征粒碰撞时间刻度的来说, 是长期的, 和<img alt="Equation 25" src="/files/ftp_upload/56632/56632eq25.jpg"> <img alt="Equation 26" src="/files/ftp_upload/56632/56632eq26.jpg"> <img alt="Equation 27" src="/files/ftp_upload/56632/56632eq27.jpg"> 粒子时间尺度的进程, 如观察和预测的时间尺度,, 按顺序,...

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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

本文介绍了一种研究稠密流体分子流体力学过程的实验性模拟方法。该技术采用振动、高恢复力颗粒桩的粒子图像测速, 并允许对强相互作用、高密度气体和液体中已知和预测的动态过程进行直接、宏观的观察。

一种研究稠密气体和液体分子流体力学过程的模拟宏观技术

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a ...

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The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed under uniform ...

Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

浓稠钇铁石榴石薄膜的形成使用气溶胶沉积

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% ...

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

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 ...

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

使用扫描透射电子显微镜研究纳米大小的物体的动态过程中的液体

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

Wicking Tests for Unidirectional Fabrics: Measurements of Capillary Parameters to Evaluate Capillary Pressure in Liquid Composite Molding Processes

吸湿排汗试验单向织物：毛细管参数的标准评价在液体复合成型工艺毛细管压力

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

光诱导的宏观振荡运动液晶网络的制备

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...