Name: measurements of waves in a wind-wave tank under steady and time-varying wind forcing
Uploaded: 2018-02-13T13:00:00
Description: Watch this Scientific Journal Video about Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing at JoVE.com

这项工作得到了以色列科学基金会306/15 号赠款的支持。

1. 系统准备
<ol><li>用自来水将水箱装满20厘米深, 以满足深水条件;清洗任何可能影响表面张力的污染物的水面。</li>
	<li>在所需的提取处放置仪表托架。<ol>
<li>装入托管管并将其放置在测试部分气流部分的中心。</li>
		<li>在计算机控制的垂直舞台上安装波形测量仪, 以实现其静态校准。</li>
	</ol>
</li>
	<li>将汉莎组件放置在所需的提取位置, 并在7厘米的横向距离上从波形表中定位, 以消除波规组件与...

<ol>
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Fluid Mech. 6 (4), 568-582 (1959).</li><li>Plant, W. 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+relationship+between+wind+stress+and+wave+slope.">A relationship between wind stress and wave slope.</a> J. Geophys. Res. 87, 1961-1967 (1982).</li><li>Zavadsky, A., Shemer, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+turbulent+air+flow+over+evolving+water-waves+in+a+wind-wave+tank.">Characterization of turbulent air flow over evolving water-waves in a wind-wave tank.</a> J. Geophys. Res. 117, C00J19 (2012).</li><li>Zavadsky, A., Liberzon, D., Shemer, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+analysis+of+the+spatial+evolution+of+the+stationary+wind+wave+field.">Statistical analysis of the spatial evolution of the stationary wind wave field.</a> J. Phys. Oceanogr. 43, 65-79 (2013).</li><li>Zavadsky, A., Benetazzo, A., Shemer, L. <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+two-dimensional+structure+of+short+gravity+waves+in+a+wind+wave+tank.">On the two-dimensional structure of short gravity waves in a wind wave tank.</a> Phys. Fluids. 29 (1), 016601 (2017).</li><li>Zavadsky, A., Shemer, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+statistical+parameters+of+the+evolving+wind+wave+field+using+Laser+Slope+Gauge.">Investigation of statistical parameters of the evolving wind wave field using Laser Slope Gauge.</a> Phys. Fluids. 29 (5), (2017).</li><li>Zavadsky, A., Shemer, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water+waves+excited+by+near-impulsive+wind+forcing.">Water waves excited by near-impulsive wind forcing.</a> J. Fluid Mech. , (2017).</li></ol>

本实验协议的目的是在不稳定的风强迫下, 在时间和空间上演化的波场进行定量表征。由于风浪本质上是随机的和三维的, 因此在时间和空间上变化很快, 在时间依赖的风力强迫下, 一个不断增长的风浪场个体认识的记录只能提供对治理的定性估计。波形参数。为了实现该协议的目标, 获得统计上可靠的时间和提取相关波特性, 需要应用具有相同风变化模式的大量实验运行的时间分辨集合平均。由于?...

自古以来, 众所周知, 水面上的波浪被风所激发。目前对控制这一进程的物理机制的理解远非令人满意。许多试图描述风力发电的理论在过去几年中提出了1,2,3,4, 但他们的可靠的实验验证还没有可用。在海洋中随机风浪的测量是极具挑战性的, 因为不可预知的风可能会在方向上和震级上变化得很快。实验室实验的优点是可控制的条件, 使长期和可重复的测量。
在实验室环境的恒定风强迫下, 风浪在空间中演化。几十年前在稳态强迫下进行的波浪的早期实验室实验仅限于瞬时表面高程测量5,6,7,8。最近的研究还使用各种光学技术来测量瞬时水表面倾角, 如汉莎9,10。这些测量允许得到一些有限的质量信息的三维结构的风波场。当风强迫是不稳定的, 因为它是在野外试验中, 引入额外的复杂性, 以风的激励问题, 因为产生的波场的统计参数不仅在空间, 但时间也不一样。到目前为止的尝试, 以定性和定量地描述波浪演变模式在时间依赖强迫下仅部份地成功了11,12,13,14,15,16. 不同似然的物理机制的相对贡献可能导致激发和波浪的增长由于风作用仍然是未知数。
我们的实验设施的目的是为了能够积累准确和多样的统计信息的变化的风波场特征在稳定或不稳定的风强迫。两个主要因素有助于进行这些详细的研究。首先, 该设施的适度规模导致了相对较短的特征演化尺度的时间和空间。第二, 整个实验由计算机完全控制, 从而使实验运行在不同实验条件下的性能能够自动、实际地实现, 无需人工干预。这些特性的实验设置是非常重要的, 在进行实验的波浪兴奋从休息的冲动风。
本文研究了风波在稳定强迫下的空间生长, 为风速17。根据植物19所提出的里程18理论, 将结果与增长率估计进行了比较。对比表明, 实验结果与理论预测有显著差异。在17中还获得了其他重要参数, 例如测试部分中的平均压降, 以及特征静压波动的绝对值和相位。在空气-水界面上的剪切应力对于描述风与波浪之间的动量和能量传递是必不可少的17,19。因此, 在大量的提取和风速下, 进行了对数边界层的详细测量, 并对水波上的湍流波动进行了分析, 结果为20。本文所确定的空气-水界面的摩擦速度u*的值用于获取在我们的设施21中测量到的风浪的无量纲统计参数。将这些值与大型实验装置和野外试验中获得的相应无量纲参数进行了比较。以前的21表明, 在适当的尺度下, 小规模设施所获得的风波场的重要特征与较大实验室积累的相应数据没有显著差异。安装和露天测量。这些参数包括具有代表性的波浪高度和波长的空间增长, 表面高程的频谱的形状, 以及较高统计矩的值。
随后在我们的设施中进行的研究22,23表明, 风波本质上是随机的和三维的。为了更好地了解风波的3D 结构, 我们尝试使用立体视频成像22对扩展区域的水面高程进行定量的时间依赖性测量。由于现有的计算机电源不足, 而且处理算法还不够有效, 这些尝试被证明只是部分成功。结果表明, 采用传统的电容式波规和汉莎, 可为风浪的空间结构提供有价值的信息。同时应用这两种仪器, 可以独立测量瞬时表面高程和瞬时表面斜率的两个分量的高时间分辨率23。这些测量允许估计波浪的主导频率和主要波浪长度, 并且提供对波浪结构的洞察在正常风向的方向。一种可由计算机控制的马达垂直移动的托管管, 它补充了传感器的集合, 用于测量风速。
所有这些研究表明, 随机和三维的风波导致测量参数的显著变化, 即使在稳定的风强迫和单一测量位置。因此, 需要长时间的测量与实测波场的特征时间尺度相称, 以积累足够的信息来提取可靠的统计量。为了获得有价值的物理洞察力的机制, 控制波场的空间变化, 必须在许多地点进行测量, 并尽可能多的价值的风速尽可能在测试部分。为了实现这一目标, 最好采用自动化的实验程序。
非恒定风强迫下的波浪实验引入了一个额外的复杂程度。在这类研究中, 必须将瞬时测量参数与风速的瞬时水平联系起来。考虑以近脉冲风强迫作为一个重要例子, 从静止的波浪中激发的实验。在这种情况下, 需要许多独立的测量, 在风的作用下演变的风波场, 在不同的时间根据相同的规定模式24。有意义的统计参数, 表示为自空气流动开始以来所经过的时间函数, 然后通过平均从独立认识积累的集合中提取的数据来计算。这项工作可能涉及连续抽样的十个和上百个小时。完成这样一项雄心勃勃的任务所需的实验课程总持续时间, 除非实验完全自动化, 否则整个方法是行不通的。直到最近, 在风浪设施中没有这样的完全计算机化的实验程序。这是在非恒定强迫下缺乏可靠的风浪统计数据的主要原因之一。
由于该实验所用的设施不是从商用的现成硬件构造的, 所以这里提供了其主要部件的简要描述。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56480/56480fig1.jpg"> 图1。示意图 (不缩放) 实验设施的视图.1-鼓风机;2流入沉降室;3-流出沉降室;4-消音器盒;5试验段;6滩;7-换热器;8蜂窝;9喷嘴;10-板式;11瓣;12-仪器运输;13波计由步进电机驱动;14-由步进电机驱动的托管管。<a href="http://cloudflare.jove.com/files/ftp_upload/56480/56480fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
实验设施包括一个封闭环风洞安装在一个波坦克 (示意图视图显示在图 1)。测试部分为5米长, 0.4 米宽, 0.5 米深。壁和地板由6毫米厚的玻璃板组成, 并被封闭在一个由铝型材制成的框架内。一个40厘米长的襟翼提供平滑的扩展气流剖面从喷嘴到水面。波浪能吸收的海滩由多孔的包装材料制成位于坦克的末端。计算机控制的鼓风机允许在测试区段达到平均气流速度在15米/秒。
该定制电容式100毫米长波测量仪由阳极氧化钽制成。0.3 毫米线安装在一个垂直的阶段, 由 PC 控制的步进电机驱动, 为波规校准设计。一个直径为3毫米的托管管, 用于测量测试部分中央气流部分的动态压力。
测量瞬时2D 水表面斜率的汉莎安装在与测试部分分离的框架上, 可以定位在罐体上的任意位置 (图 2)。汉莎由四主要部分组成: 激光二极管、菲涅尔透镜、扩散屏和位置传感探测器 (PSD) 组件。激光二极管产生 650 nm (红色), 200 兆瓦可获得焦点激光束直径约0.5 毫米。26.4 厘米直径的菲涅尔透镜, 焦距为22.86 厘米, 将传入的激光光束定向到位于透镜后焦平面上的 25 x 25 厘米2扩散屏幕。
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56480/56480fig2.jpg"> 图2。激光斜率计 (汉莎) 的示意图.1-激光二极管;2-菲涅尔透镜;3-扩散屏幕;4位传感器检测器 (PSD)。<a href="http://cloudflare.jove.com/files/ftp_upload/56480/56480fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
该协议描述了允许执行实验的过程, 在这种情况下, 在时间依赖的风力强迫下, 测量非恒定波的许多参数。考虑到实验设施的技术局限性, 可以根据所需风速的时间来调整程序。本议定书具体描述了在每一个实现中, 风开始几乎在最初平静的水的冲动的实验。稳定的风强迫, 然后持续足够长的风波场在测试段各处达到准稳态状态。风最后被关闭, 再几乎冲动。在各个阶段, 记录了多个波形参数。该程序允许计算出许多统计代表性的集合-平均数量表征瞬时局部风波场是新颖的, 并在最近在我们的设施进行的实验过程中发展22,23,24。

<table>
	<tbody>
		<tr>
			<td>PSD</td>
			<td>THORLABS</td>
			<td>PDP90A</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Diode</td>
			<td></td>
			<td></td>
			<td>any laser pointer &#8804; 200 mW</td>
		</tr>
		<tr>
			<td>Aspheric Fresnel Lens</td>
			<td>EDMUND OPTICS</td>
			<td>#46-390</td>
			<td>Diameter 10.4&#39;&#39;, Focal length 9&#39;&#39;</td>
		</tr>
		<tr>
			<td>Wave-gauge</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>Pressure Transducer</td>
			<td>MAMAC SYSTEMS</td>
			<td>PR-274-R2-VDC</td>
			<td></td>
		</tr>
		<tr>
			<td>Signal Conditioner</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>Diffusive screen</td>
			<td>EDMUND OPTICS</td>
			<td>#02-147</td>
			<td></td>
		</tr>
		<tr>
			<td>Water tank</td>
			<td></td>
			<td></td>
			<td>custome made</td>
		</tr>
		<tr>
			<td>A/D card PCI-6221</td>
			<td>National Instruments</td>
			<td>779066-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Pitot tube</td>
			<td>KIMO Instruments</td>
			<td>12971</td>
			<td></td>
		</tr>
		<tr>
			<td>15&#176; Nom. VIS-NIR Coated, Wedge Prism</td>
			<td>EDMUND OPTICS</td>
			<td>#47-624</td>
			<td></td>
		</tr>
		<tr>
			<td>10&#176; Nom. VIS 0&#176; Coated, Wedge Prism</td>
			<td>EDMUND OPTICS</td>
			<td>#49-444</td>
			<td></td>
		</tr>
		<tr>
			<td>2.5&#176; Nom. Fused Silica Wedge Prism Uncoated</td>
			<td>EDMUND OPTICS</td>
			<td>#84-863</td>
			<td></td>
		</tr>
		<tr>
			<td>4&#176; Nom. Uncoated, Wedge Prism</td>
			<td>EDMUND OPTICS</td>
			<td>#43-650</td>
			<td></td>
		</tr>
		<tr>
			<td>5.0&#176; Nom. Fused Silica Wedge Prism Uncoated</td>
			<td>EDMUND OPTICS</td>
			<td>#84-865</td>
			<td></td>
		</tr>
		<tr>
			<td>LabView Full Development System</td>
			<td>National Instruments</td>
			<td>776670-35</td>
			<td></td>
		</tr>
	</tbody>
</table>

measurements of waves in a wind-wave tank under steady and time-varying wind forcing

这篇手稿描述了一个实验程序, 它允许获得不同的定量信息的时间和空间演化的水波兴奋的时候依赖和稳定的风强迫。利用电容式波浪测量仪和激光斜率计 (汉莎) 测量了风波装置试验段沿线多个位置的瞬时水面高程和瞬时面斜率的两个分量。计算机控制的鼓风机在水箱的水中提供气流, 其速率可能会随时间而变化。在目前的实验中, 测试部分的风速最初从静止到设定值快速增加。它然后保持恒定为规定的期间;最后, 气流被关闭。在每次实验运行的开始, 水面是平静的, 没有风。鼓风机的操作是同时启动的, 并获得由计算机提供的所有传感器的数据;数据采集一直持续到坦克中的波浪完全衰减。在相同的强迫条件下进行的多个独立运行允许确定统计可靠的集合平均特征参数, 以定量地描述在初始开发阶段的风浪变化时间, 作为提取功能。该程序还允许描述在稳定的风力强迫下的波浪场的空间演化, 以及当风被关闭后, 随着海浪的衰减, 作为提取的函数。

在图 6、图 7和图 8中绘制了代表性的集合平均结果。瞬时曲面高程的 RMS 值的变化 <η2>1/2的特征是随机风波振幅的特点, 如图 6所示, 作为时间流逝的函数, 因为鼓风机的启动。显示的结果与板式、 x和三目标风速 ( U. ) 的距离为3。</...

Watch this Scientific Journal Video about Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing at JoVE.com

Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing

这篇手稿描述了一个完全计算机控制的程序, 允许获得可靠的统计参数, 从实验的水波的稳定和不稳定的风强迫在一个小规模的设施。

稳定时变风强迫下风浪罐中波浪的测量

This manuscript describes an experimental procedure that allows obtaining diverse quantitative information on temporal and spatial evolution of water ...

Research

Education

JoVE Journal

JoVE Core

Engineering

Physics

Electrical Engineering

Unit 1

First and Second-Order Circuits

Waves

SCIENTISTS IN ACTION

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

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 ...

科研

工程学

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

互溶的测量准备和摩擦力显微镜，反对聚合物刷

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

Preparation and Evaluation of Hybrid Composites of Chemical Fuel and Multi-walled Carbon Nanotubes in the Study of Thermopower Waves

化学燃料和多壁碳纳米管的混杂复合材料的热电波的研究准备和评估

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs ...

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films

环境钚的薄膜弥散形态和生物利用度测量

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can ...

Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

实验协议来调查产品的粒子雾化在耐磨和环境下风化

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

锁模自动化的非线性偏振旋转光纤激光器通过输出偏振测量

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

制造和Acoustofluidic设备的运营支撑体声波驻波的聚焦鞘颗粒

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must ...

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

在稳定层流边界层扩散火焰本地热通量和燃烧率的估计实验方法

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex ...

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

在油样品的相行为在炼油工艺条件的原位可视化

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to ...

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

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 ...