作者要感谢本杰明 Sommerkorn, 加布里埃尔杜邦, 杰克 Eggan 和 Chirawat Sanpakit 谁协助在这里提出的实验。珍妮特 Cobian Iñiguez 承认支持由美国宇航局 MUREP 机构研究机会 (米洛) 授予号码 NNX15AP99A。这项工作也由美国农业部/USDI 国家防火计划通过美国农业部森林服务, PSW 研究站和加州大学河滨分校的协议资助。

警告: 由于以下协议中的几个步骤涉及有可能导致损伤的活动, 因此应确保按照已建立的安全协议 (包括防火) 使用适当的个人防护设备 (PPE)耐磨的衣服和防护眼镜. 
 1. 皇冠燃油床负载电池检测安装程序 <ol> <li> 通过将双弹簧门扣 (参见 材料表 ) 通过钳位和 #39 的销孔来修改 4 C 钳 (参见 图 2 )。使用扣来悬挂皇冠燃料床. </li>
	<li> 使用一组不同的 C 形夹具, 将每个负载应变计单元粘贴到风洞框架的顶部 (请参见 图 2 ). </li>
	<li> 将修改后的 C 形夹具附加到应变计单元的自由端, 扣挂起。将链条连接到皇冠燃料床的平台上. </li>
	<li> 将皇冠燃料床平台从风洞框架中挂起, 将每个皇冠燃料床链连接到登山. </li>
	<li> 一旦四负载单元中的每一个都完全安装并连接到燃料床上, 将它们的导线连接到将用于数据采集的惠斯桥上。用防火绝缘材料盖住负载电池, 如用于防火避难所的那种. </li>
</ol> <img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56591/56591fig2.jpg"/> 图 2: 风洞顶部燃料床负载电池检测. ( a ) 风洞前视图 ( b ) 修改了登山和皇冠燃料床链的 C 形钳, 它支持皇冠燃料床。( c ) 使用 c 形夹具连接到风洞框架的负载单元。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig2large.jpg" target="_blank"> 请单击此处查看此图的较大版本. </a> 
 2. 负载单元校准 注意: 由负载单元产生的信号通过: <img alt="Equation 2" src="/files/ftp_upload/56591/56591eq2.jpg"/> 转换为等效质量
其中, V 是信号, 通常是在毫伏中, A 和 B 是通过校准确定的常量, m 表示质量为克。方程 (2) 的所有参数都是通过为该协议中的皇冠质量仪器开发的自定义仪器控制接口获得的。当第一次使用该系统时, 使用精确的权重来校准负载单元信号。校准常数 A 和 B 将根据测量这些精度权重的负载时产生的信号获得。常量 A 是从以下位置计算的: <img alt="Equation 3" src="/files/ftp_upload/56591/56591eq3.jpg"/> 其中 m t 是试验精度重量的质量, w 是生成的信号。加载到负载单元格上的权重, 而 w, o 对应于在负载单元格上不应用权重时产生的信号. 
<ol> <li> 若要获取校准常量 a , 则挂钩精度权重 (一个好的范围将是 200-500 g) 到第一个加载单元。将精度权重的质量用作公式 (3) 中的参数 m t . </li>
	<li> 使用输入 # 字段将负载单元格增益设置为 128, 如下所示 图 3b , i. 1。这对应于设备允许的最大值. </li>
	<li> 从仪表接口读取输出0的信号输出 (请参见 图 3b , i2)。这是等式 (3) 中 a w 的参数. </li>
	<li> 松开重量并读取显示在仪器界面中的新值 ( 图 3b , i2)。这是参数 a w, o . </li>
	<li> 计算 根据步骤2.1 到2.4 中获得的参数 ( m t 、 a w 、 w、o ) , 并提供了公式. </li>
	<li> 在控制器接口中, 使用上一步中获得的 值 填充每个传感器的 Ch 0-m 值. </li>
	<li> 若要查找偏移值, B , 请删除所有权重, 读取和 #39 中的值; 输出已校准 (g) 和 #39; 框 (参见 图 3c , i2 ), 将此值乘以-1。生成的数字是常量 B, 请在和 #34 中键入此数字; 加法和 #34; Ch 0-一个框 (参见 图 3c , i. 3). </li>
	<li> 对每个负载单元 (0、1、2、3) 重复步骤 2.3-2.8, 系统现在已完全校准; 继续用燃料装载燃料床. </li>
</ol> <img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56591/56591fig3.jpg"/> 图 3: 加载单元的仪表控制接口数据输入步骤校准. ( a ) 桥接初始设置窗口, 并在第一阶段加载单元校准 ( c ) 窗口中为第二阶段的负载单元校验 ( d ) 窗口进行最后一次加载单元校准阶段, 文件保存在这里, 并开始数据记录。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig3large.jpg" target="_blank"> 请单击此处查看此图的较大版本. </a> 
 3. 查帕拉尔和精益燃料床的制备 注意: 每个实验使用2公斤的活 chamise 和0.5 公斤的精益 (白杨丝碎). 
<ol> <li> 从为燃烧收集的燃料堆中收集几瓶1品脱的燃料 (3-4 瓶)。
	<ol> <li> 按照同胞和院长对烘乾样品和获得燃料水分含量 30 所划定的程序进行操作。
	</ol> </li> <li> 从最近收获的 chamise 的捆绑中修剪单个分支, 以删除大于和 #188 的死材和分支材料; 英寸直径。将剩余的带电燃料材料放入容器中进行称量. </li>
	<li> 选择2公斤的修剪 chamise 和0.5 公斤的精益求精使用电子秤。将0.5 公斤的精益放在风洞地板上的地面燃料床平台上, 确保体积密度尽可能均匀。通过在已知区域深度上放置已知的精益量来执行此项设置. </li>
	<li> 拉紧 (绒毛) 压实的精益, 以减少其体积密度, 使其容易燃烧. #160; 加载2公斤的修剪 chamise 到平台上悬挂从负载电池创建高架燃料床。均匀地分散在整个平台上的 chamise 分支, 以产生一个统一的燃料床. </li>
</ol> 4。热电偶排列 注意: K 型热电偶用于测量两个燃料层的温度。数据是通过一个由自定义图形用户界面控制的数据采集系统收集的 (见控制器设计软件的材料表)。热电偶推荐为使用是 24 AWG 热电偶与响应时间 0.9 s. 
<ol> <li> 将十六 24 AWG 热电偶 (导体直径: 0.51054 mm) 的数组连接到数据记录器 (响应时间: 0.9 秒). </li>
	<li> 将6热电偶插入顶部燃料层。把这些热电偶 20 cm 分开并且避免热电偶的联络与分支。将10热电偶插入表面燃料层。把这些表面燃料热电偶 10 cm 分开并且避免热电偶的联络与分支 (参见 图 4 ). </li>
	<li> 通过单击 "#34"、"启动/#34"、"热电偶控制软件" 界面中的按钮来激活数据记录. </li>
</ol> <img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56591/56591fig4.jpg"/> 图 4: 热电偶阵列表面和顶部燃料层示意图位置. 这里 6 个热电偶入了入冠燃料层数 20 cm 除彼此之外。10 热电偶入了入表面燃料层数 10 cm 分开。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig4large.jpg" target="_blank"> 请单击此处查看此图的较大版本. </a> 
 5. 图像获取设置 <ol> <li> 将具有红色标记的可视化引用目标挂载在风洞窗口上方10厘米的间隔处。使用此目标作为参考, 以确定从实验视频的火焰高度. 
	注意: 示例火焰高度显示在 图 5 中. </li>
	<li> 设置照片数据收集。集中在风洞试验区, 调整摄像机焦距, 以捕获整个垂直参考目标以及燃料床区域. </li>
	<li> 设置摄像机数据收集。安装在墙上的万能相机壁挂摄像头, 提供了风洞测试部分的全景. </li>
</ol> <img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56591/56591fig5.jpg"/> 图 5: 从一个典型的实验中取样火焰高度的照片。用红色标记的蓝色视觉目标作为从实验视频中确定火焰高度的参考。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig5large.jpg" target="_blank"> 请单击此处查看此图的较大版本. </a> 
 6. 流设置 注意: 风洞中装有变速风扇。风洞中的气流被预先校准到风扇速度。为了达到预期的风速, 选择了风扇转速 (赫兹)。在目前的试验中, 没有风和1米/秒的风流的情况下进行了研究. 
<ol> <li> 将风扇速度设置为速度控制器上的1米/秒。打开风扇以确保它正常工作. </li>
	<li> 关闭风扇。它现在可以使用了. 
	注: 燃烧建筑物设计用于安全地进行防火实验, 同时从工作空间中疏散烟雾。通知当地消防部门, 正在进行试验以消除假警报的发生. </li>
	<li> 关闭大楼所有的门, 以确保屋顶通风口是唯一可能的烟雾疏散出口. </li>
	<li> 打开空气供应风扇, 从楼面外的建筑物中引入新鲜空气。打开排气扇, 通过屋顶通风口排出烟雾. 
	注: 这将建立一个低速度, 高容积的空气流量从建筑物外垂直上升, 由于轻微的压力差和屋顶开口. </li>
	<li> 在每次试验之前, 使用湿球湿度计测量环境空气的相对湿度和温度. </li>
</ol> 7。点火 (与步骤8同时实施) 注意: 点火过程应由点火机组成员按如下方式进行。为了提高安全性, 建议在点火过程中在试验区附近留有第二名船员. 
<ol> <li> 指示 #39; 点燃和 #39; 用变性乙醇浸泡在怡东表面燃料床的前缘。将酒精瓶放在远离点火区的地方, 使用丁烷炬, 将表面燃料床的一端点燃, 与燃料床的前缘平行。小心, 因为酒精浸泡燃料将容易点燃. </li>
	<li> 一旦燃料床被点燃, 踏出测试区并关闭隧道门。如果试验需要风, 打开风洞风扇. </li>
</ol> 8。启动实验运行 注意: 验证实验是否正确设置后, 应启动摄像机. 
<ol> <li> 打开要录制的摄像机. </li>
	<li> 大声朗读实验编号/代码、日期和实验配置, 以便摄像机上的麦克风记录此信息. </li>
	<li> 指示计算机组通过滴答和 #34 开始数据记录; 启用数据记录和 #34; 在仪表控制界面中选择 (请参见 图 3d , i. 1)。指示点火人点燃燃料。一旦点火机组成员退出风洞, 指示风机组成员启动风洞风扇。这将是实验的开始时间为零 (t = 0). </li>
</ol>

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作者没有什么可透露的。

在整个实验中, 测量高燃料质量的能力是这项技术的主要优点之一。以前的研究查帕拉尔火灾的重点是只在树冠火启动或只在表面传播, 但不是两者兼而有之。这些研究已经量化了在树冠层点火的可能性, 并离开了对未来工作的研究23。我们的方法允许测量的质量损失, 温度分布和火焰几何的两个层涉及灌木树冠火点火和蔓延。它提供了一种从质量损失率间接推断能量通量的方法。其他研究表明, 直接测量热通量在火灾蔓延实验中的优势。芬尼et al.介绍了野火扩散实验中的几个热通量测量示例34。通过这些工作, 他们能够对野火扩散中的对流和辐射传热的作用进行重要观察。这里提出的方法允许在野火蔓延的查帕拉尔的能量动力学基线观测。一个有益的下一步将涉及对辐射和对流换热的特殊贡献的更 in-depth 的分析。为了将来的研究, 我们建议探索直接测量热通量。
为了确保测量的准确性, 有几个关键步骤。测量冠质量损失的载荷单元的标定也许是最关键的步骤, 也是最耗时的步骤。这是因为在每个实验日结束时, 皇冠燃料床必须卸载, 并在配置中的轻微移动可能会导致质量读数的变化。因此, 必须在每个实验日开始时进行校准。对于未来的实验, 一个更永久性的配置将是理想的。在未来的配置中, 单个的负载单元将被贴在实验装置上。
除了校准步骤, 该协议的另一个关键步骤是燃料的制备。整个实验计划的目的是为了提高我们预测规定的火灾行为的能力, 从而更好地了解生活燃料中的燃烧。当活分支由½英寸 (1.27 cm) 可以消耗在高强度被规定的烧伤的火焰前面在查帕拉尔 (参见绿色35), 更大的直径燃料在火焰前面典型地没有被烧。实验室燃烧使用查帕拉尔燃料的重点是使用燃料, 通常会消耗的规定烧伤的蔓延火焰阵线 (见科恩和布拉德肖36, 魏泽et al.37). 主要查帕拉尔种类包括 chamise (Adenostoma 三), 而其他查帕拉尔燃料包括 manzanita (Arctostaphylos glandulosa) 和 hoaryleaf ceanothus (ceanothus crassifolius)。在这里 chamise 是燃料选择, 因为它是最易燃的这些物种。只要分支大小保持在¼英寸以下, 就可以修改该协议以包括其他物种。
一般而言, 无论选择哪种燃料, 都应修剪树枝, 使所有的树枝直径都 #60; ¼英寸 (0.63 厘米) 以保持均匀。不执行此步骤或不正确执行将会对结果的重现性产生负面影响。在修剪的分支也可能是不利的, 因为具有非常小的分支尺寸的燃料床往往有更大的包装密度, 因此也有不同的燃烧。在这里描述的过程中, 在 Omodan38之后, 包装密度保持在平均9.2 公斤/米3。
值得注意的是, 由于这个实验的规模, 需要4人或以上的人员, 以确保在实验中的效率。在任何时候, 让一个人都能看到该协议的负责人是很重要的, 确保所有步骤都能正确地遵循。此人负责船员的安全以及实验的协调。重要的是, 这个人和其他船员注意他们的安全和环境, 这意味着有可见的灭火器, 确保排气口是和门关闭在实验过程中。
此外, 将所有的仪器与单一的触发按钮同步是有利的。这将使数据分析和处理更加有效。最后, 在这里的技术被掌握后, 自然的进展将是集成一些剩余的风洞能力, 如温度控制, 已显示在其他研究是另一个重要因素考虑。这将有助于更广泛地控制环境条件。这里提出的结果是在夏季的试验期间, 当燃料通常干燥;这一时期也对应于当年荒地火灾发生时的一部分。然而, 如果在一个试验期内对大量的季节进行分析, 则可以采用风洞温度控制。同样, 燃料含水率的变化也将提供这一参数对查帕拉尔冠火过渡和扩散的影响的洞察力。在设计一个扩展的研究, 包括燃料水分含量和体积密度作为控制参数, 错误分析, 如马维尼et al.提供的, 将协助设计的方法与实验一致性39。
这里所描述的技术, 可以检查的皇冠火的行为, 集成测量质量, 温度和火焰几何的两层燃料涉及。这一方法所产生的分析, 可能会导致更多的理解查帕拉尔火, 特别是在独立, 被动或主动冠火行为的范围内, 由范 Wagner5提出, 从而提供知识协助火灾预测和控制。

在 2016年, 加利福尼亚州总共经历了6986场荒地大火, 消耗了564835英亩的1, 造成数百万美元的损失, 并冒着数百人的健康风险。由于区域地中海气候, 主要燃料来源为这些火是查帕拉尔植被社区2。火灾蔓延在查帕拉尔可以被认为是一个皇冠火, 因为主要的燃料, 烧伤是提升3。共同存在与主要地居住的冠层数, 是死的表面燃料层数, 包括铸造的叶子、分支和草本植物生长在和在各自的灌木之间。火将更容易启动在死表面燃料层。一旦表面火点燃, 火可能转移到冠层, 在火释放的能量急剧增加。虽然查帕拉尔火灾通常被模拟为火灾蔓延在深表面燃料4, 有有限的研究查帕拉尔火灾的树冠火灾。

查帕拉尔的树冠特征, 包括叶片颗粒形状, 与北方针叶林不同, 其中大部分研究都是在那里发生的。众多的实验室和野外规模研究已经调查了野火动力学的各个方面6,5,7,3,8,9,10 ,11,12。在实验室实验领域, 有几项研究分析了风和燃料性质等参数对查帕拉尔冠火行为的影响。Lozano7检测了在两个独立的树冠燃料层存在下的顶火起爆特性。在 Tachajapong et al.3, 在风洞内燃烧了离散表面和树冠层, 并进行了表面火灾的表征。只有冠火起爆被充分描述留下充分的分析传播为未来工作。Li et al.11报告了火焰的传播, 虽然单查帕拉尔灌木。在相关工作中, 克鲁兹et al.10,9开发了一个模型来预测在展开的表面火之上的针叶树叶的点火。对查帕拉尔燃料的燃烧特性进行了研究, 并对散装燃料和个体叶片的试验进行了探讨13,14,15,16。Dupuy et al.13通过在圆柱筐中燃烧燃料, 研究了松松树针和精益的燃烧特性。他们观察到, 在这些燃料中, 火焰高度通过2/5 幂定律与热释放率有关, 正如先前在文献1718中所报告的那样。Sun et al.14在类似的圆柱筐中燃烧查帕拉尔燃料, 以分析三查帕拉尔燃料的燃烧特性: chamise (Adenostoma 三)、ceanothus (ceanothus crassifolius) 和 manzanita (Arctostaphylos glandulosa)。
在上述实验室研究的结果的激励下, 我们的目的是提出一种方法来描述在表面和灌木树冠层的传播。此外, 我们的目的是澄清一些关键的特征, 决定了表面-冠层相互作用的程度。为此, 我们开发了实验实验室方法, 研究在荒地表面燃料燃烧的垂直转变为在高架灌木燃料中蔓延的火灾。在这些类型的火灾中, 将火翻译成树冠, 被称为加冠, 在适当的条件下可持续传播。一般而言, 查帕拉尔的火灾行为是由地形、天气和燃料19决定的。结果表明, 风影响能量释放率在燃料5,3,8,20。
多孔燃料中的火蔓延可以看作是一系列的过渡或阈值, 必须跨越才能成功21。精力充沛地, 燃料微粒点燃, 如果它接受的热量的数量结果在气体的混合物成功地反应与氧气。当燃烧粒子的热量点燃相邻的燃料粒子时, 产生的火焰就会扩散。如果火势能够跨越可燃燃料元件之间的空隙, 就会蔓延到地面。如果火焰的表面火能够垂直传播到树冠的灌木和树木, 火灾行为的重大变化, 包括增加的热释放率, 往往被观察到, 由于更大的可用性燃料。荒地火灾中的热能动力学包括几个尺度, 从非常大的规模, 如在大型火灾, 往往需要气候建模, 小规模需要化学尺度动力学建模。在这里, 我们处理实验风洞尺度行为建模;对于化学尺度的纤维素燃烧研究, 读者被称为工作, 如沙利文et al.22
自2001年以来, 我们进行了各种实验, 检查了一些实验室规模的能量阈值23,8,24,25,26, 27, 重点是与查帕拉尔相关的带电燃料。虽然室外测量的火可以提供更逼真的结果, 受控环境的风洞允许划定各种参数的影响。例如, 控制风对于查帕拉尔的树冠火灾尤其重要, 例如在南加州, foehn 类型的风, 称为圣安娜风, 是典型的火灾事件的驱动因素。由于本文所述方法的主要动力是研究风和其他受控参数对查帕拉尔火灾蔓延的影响, 本研究在实验室规模风洞中进行。读取器由 Silvani et al.定向到工作28用于现场测量查帕拉尔火灾中的温度, 类似于此处所示。有关风对火势蔓延影响的实地测量, 请参阅莫兰迪et al.29
通过量化概率, 对影响查帕拉尔燃料扩散的几个参数进行了实验分析火传播成功在高架燃料床8。目前的实验研究涉及的方法是开发的研究查帕拉尔树冠火灾蔓延的模拟表面燃料和皇冠燃料在测试段的低速风洞。表面燃料是建模与精益求精 (干碎木材)。表面燃料床被安置在风洞的地面水平在标准尺度 (参见图 1)。代表顶部燃料床, 一个燃料床与 chamise 被放置在表面燃料床通过悬挂燃料从一个平台上安装在风洞框架 (见图 1)。两个燃料床都被检测温度和质量损失测量;火焰几何学是从实验录像中获得的。测量的参数包括质量损失率、燃料含水量和空气相对湿度。控制的参数是风存在, 表面燃料床和树冠燃料床之间的距离, 以及表面燃料的存在。测量的质量损失率可以用来计算热释放率, 这是定义为: 
<img alt="Equation 1" src="/files/ftp_upload/56591/56591eq1.jpg"> 其中h是燃料燃烧的热量, m是燃料质量, t是时间。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56591/56591fig1.jpg"> 
图 1: 风洞实验装置.皇冠燃料床的位置, 地面燃料床, 和隧道风扇已被标记为方便。地面燃料床被安置在风洞的地面水平在标准标度。代表顶部燃料床, chamise 的燃料床被放置在地面燃料床上, 悬挂燃料从一个平台上安装在风洞框架。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
实验的重点是了解查帕拉尔冠火的行为, 特别是点火, 火焰传播和传播的机制, 火焰锋速度, 和燃料消耗率。为了研究表面火和冠火之间的相互作用, 六配置的表面和顶部燃料床与没有应用风流, 已被烧毁的风洞: 冠燃料只有和没有风 (2), 树冠和表面燃料床分离两个距离与和没有风 (4)。表 1总结了6实验类的实验配置。在表中, 表面燃料层参数表示在试验过程中是否存在表面燃料, 风参数指的是风的存在, 树冠的高度是指顶部燃料床底部与表面底部之间的距离燃料床每项试验都测量了燃料湿度, 但不受控制, 平均燃料含水量为 48%, 而最小和最大值分别为18% 至68%。
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>类</td>
			<td>表面燃料床</td>
			<td>风</td>
			<td>皇冠高度</td>
		</tr>
		<tr>
			<td>一个</td>
			<td>缺席</td>
			<td>无风</td>
			<td>60或70厘米</td>
		</tr>
		<tr>
			<td>b</td>
			<td>缺席</td>
			<td>1毫秒-1</td>
			<td>60或70厘米</td>
		</tr>
		<tr>
			<td>c</td>
			<td>目前</td>
			<td>无风</td>
			<td>60厘米</td>
		</tr>
		<tr>
			<td>d</td>
			<td>目前</td>
			<td>无风</td>
			<td>70厘米</td>
		</tr>
		<tr>
			<td>e</td>
			<td>目前</td>
			<td>1毫秒-1</td>
			<td>60厘米</td>
		</tr>
		<tr>
			<td>f</td>
			<td>目前</td>
			<td>1毫秒-1</td>
			<td>70厘米</td>
		</tr>
	</tbody>
</table>
表 1: 实验配置在这里, 表面燃料床参数表示在试验过程中是否存在表面燃料, 风参数指的是风的存在, 树冠的高度是指顶部燃料床底部与表层燃料床底部之间的距离。
电子秤测量表面燃料质量, 我们开发了一个自定义质量损失系统的冠层。该系统由单独的负载单元连接到悬挂的燃料床的每个角落。消费级摄像机记录了视觉火焰;图像处理的视觉数据使用自定义脚本生成的火焰特性, 包括高度和角度。开发了一个程序, 将视频帧从 RGB (红/绿/蓝) 编码转换为黑白, 通过一个光强阈值的过程。火焰的边缘是从黑白视频帧中获得的。最大火焰高度被定义为火焰边缘的最高点, 同时也获得了火焰的瞬时高度。在图像中, 火焰的高度是从燃料床的底部测量到火焰的最大垂直点。所有的处理代码以及为该协议设计的仪表控制接口都是作者通过他们的软件访问站点提供的。在当地收割现场燃料, 并在24小时内进行实验性烧伤, 减少水分流失。热电偶阵列记录了在风流向方向的燃料床温度, 从而能够计算传播速率。图 1显示了燃料床设置的示意图以及热电偶的布置。实验协议的细节如下。

<table>
	<tbody>
		<tr>
			<td>Wind Tunnel Instrumentation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>cDAQ-9178 CompactDAQ Chassis</td>
			<td>National Instruments</td>
			<td>781156-01</td>
			<td></td>
		</tr>
		<tr>
			<td>NI-9213 C Series Temperature Input Module</td>
			<td>National Instruments</td>
			<td>785185-01</td>
			<td></td>
		</tr>
		<tr>
			<td>NI SignalExpress for Windows</td>
			<td>National Instruments</td>
			<td>779037-35&#160;</td>
			<td>Newest version, older version used for experiment</td>
		</tr>
		<tr>
			<td>High Temperature Nextel Insulated Thermocouple Elements</td>
			<td>Omega</td>
			<td>XC-24-K-18</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermocouple Extension Wire with Polyvinyl Coated Wire and Tinned Copper Overbraid</td>
			<td>Omega</td>
			<td>EXPP-K-24S-TCB-P</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultra High Temperature Miniature Connectors</td>
			<td>Omega</td>
			<td>SHX-K-M</td>
			<td></td>
		</tr>
		<tr>
			<td>CompuTrac MAX 2000XL&#160;</td>
			<td>Arizona Instruments</td>
			<td>MAX-2000XL</td>
			<td>Discontinued, Newer Model Out</td>
		</tr>
		<tr>
			<td>Kestrel 3000 Pocket Weather Meter</td>
			<td>Nielsen-Kellerman</td>
			<td>0830</td>
			<td></td>
		</tr>
		<tr>
			<td>Satorius CPA 34001S&#160;</td>
			<td>Sartorius</td>
			<td>25850314</td>
			<td>Discontinued Model</td>
		</tr>
		<tr>
			<td>5 Kg Micro Load Cell (X4)</td>
			<td>Robotshop.com</td>
			<td>RB-Phi-118</td>
			<td>Strain Gauge Load Cell</td>
		</tr>
		<tr>
			<td>Phidget PhidgetBridge Wheatstone Bridge Sensor Interface</td>
			<td>Robotshop.com</td>
			<td>RB-Phi-107</td>
			<td>Interfaces with 4 load cells, performs signal amplification</td>
		</tr>
		<tr>
			<td>#2 Stainless S-Biner (X4)</td>
			<td>Home Depot</td>
			<td>SB2-03-11</td>
			<td>Dual spring gate carabiners used to mount load cells</td>
		</tr>
		<tr>
			<td>2 in. Malleable Iron C-Clamp</td>
			<td>Home Depot</td>
			<td># 4011</td>
			<td>Used to mount load cells</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Personal Protective Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Wildland Firefighter Nomex Shirt</td>
			<td>GSA Advantage</td>
			<td>SH35-5648</td>
			<td></td>
		</tr>
		<tr>
			<td>Fireline 6 oz Wildland Fire Pants</td>
			<td>GSA Advantage</td>
			<td>139702MR SEV16</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Fuels</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chamise</td>
			<td>Collected in situ</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Natural Shredded Wood Excelsior &#8211; Natural Coarse 50 lbs bail</td>
			<td>Paper Mart</td>
			<td>21-711-88</td>
			<td></td>
		</tr>
		<tr>
			<td>Bernzomatic UL100 Basic Propane Torch Kit</td>
			<td>Home Depot</td>
			<td>UL100KC</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol</td>
			<td>Convenience store</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Video and Photography</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon D3000 10.2-MP DSLR camera with DX-format sensor and 3x 18x55mm Zoon-NIKKOR VR Image Stabilization Lens</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sony Handycam Camcorder DCR-SX85</td>
			<td>Amazon.com</td>
			<td>DCR-SX85</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NI LabView</td>
			<td>National Instruments</td>
			<td>Student Version</td>
			<td>Used for instrument control and interfacing</td>
		</tr>
		<tr>
			<td>MATLAB Student Version (MATLAB_R2014a)</td>
			<td>Mathworks</td>
			<td>Student Version&#160;</td>
			<td>Used for data post-processing including image processing</td>
		</tr>
	</tbody>
</table>

wind tunnel experiments to study chaparral crown fires

本协议提出了一种实验室技术, 旨在研究查帕拉尔冠火点火和蔓延。在一个低速风洞中进行了实验, 其中两个不同的燃料层被建造来代表查帕拉尔中的表面和树冠燃料。Chamise, 一种常见的查帕拉尔灌木, 包括活冠层。用精益 (碎木) 建造的死燃料表面层。我们开发了一种方法来测量两个燃料层的质量损失、温度和火焰高度。热电偶放置在每层估计温度。摄像机捕捉到了可见的火焰。数字图像后处理产生火焰特性, 包括高度和火焰倾斜。自定义冠质量损失仪器开发了 in-house 测量了冠层质量的演变在烧伤期间。利用技术匹配理论和其他实证研究得出的质量损失和温度趋势。在本研究中, 我们提供了详细的实验程序和有关仪器使用的信息。并对燃料层中燃料质量损失率和温度的代表性结果进行了讨论。

从视频数据中获得了树冠和表面火焰高度数据。实验的典型火焰高度趋势在图 6中介绍。火焰高度行为跟随在太阳中发现et al.14
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56591/56591fig6.jpg"> 
图 6: 估计的顶部火焰高度.这里U = 1 米/秒, 表面-冠分离d = 70 厘米。这对应于一个代表性 E 类实验。通过对实验视频图像的处理, 得到了火焰的高度。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig6large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
选择了图 6中火焰高度的变化, 因为它显示了典型的火焰高度行为。在这些类型的实验中, 火焰开始小, 靠近燃料床的中间, 然后随着火焰接近燃料床的末端而衰减。该图中的实验是 F (风速在1米/秒, 树冠与表面燃料的距离为70厘米)。在这种情况下, 风帮助火焰倾斜。由于火焰倾斜, 火焰对燃料床的辐射热传递增强了31。当火焰穿过燃料床时, 它会预热燃料的前方。中间燃料床似乎是一个最佳的位置, 充分预热已经发生在大量的燃料, 以创建一个大的火焰。燃料床的末端也是预热的, 然而, 燃料的数量变得有限, 以便较少热解气体被发布, 导致减少的火焰高度。
燃料消耗率在两个燃料层的整个范围内得到。在图 7中, 对所选实验的质量损失的演化过程进行了介绍。纲参数m是瞬时质量m和初始质量m0的比率。无量纲时间Τ是实验时间的比率t和总刻录时间tf, 其中总刻录时间定义为燃烧点火停止的时间。在实验过程中, 质量损失的演化遵循了预期的行为。三一般区域从质量损失曲线的特征被辨认了: 点火, 燃烧和闷燃, 参见图 7。这是一个案例 F 实验 (风在1米/秒, 表面和树冠之间的距离70厘米)。燃料含水率为 45%, 相对湿度为 66%, 总燃烧时间为2.5 分钟, 总体质量损失和质量损失趋势与 Rothermel32和查普曼·福瑞博et al的结果相匹配。33
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/56591/56591fig7.jpg"> 
图 7: 油耗趋势.描述的是一个代表性的 F 级实验, 其中 U = 1 m/s 和表面冠分离 d = 70 cm. 燃烧区域被标记在情节 (点火, 燃烧和闷燃)。在大多数实验中观察到这三区域的普遍趋势。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig7large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
为了说明通过这种方法所描述的实验所获得的表面和树冠层的质量损失趋势, 四实验的结果在图 8和图 9中进行了介绍。图 8所表示的实验类别的平均刻录时间如下: C 和 D 类平均值4.5 分钟, E 和 F 平均2.5 分钟。可以看到, 风提高了质量损失率和总烧伤时间。
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/56591/56591fig8.jpg"> 
图 8: 代表试验的表面燃料床质量损失数据显示从实验以风在 1 m/s 和没有风, 并且两个表面冠距离测试了: d = 60, 70 cm. 这里的质量损失数据是从用于表面燃料床的数字秤上获得的。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig8large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/56591/56591fig9.jpg"> 
图 9: 代表试验的皇冠燃料床质量损失数据显示试验与风和没有风并且两个表面冠距离测试了。这里的质量损失数据是从用于皇冠燃料床的负载细胞仪器中获得的。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig9large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
在燃料床内使用十六热电偶测量了两个燃料层的气相温度。热电偶被标记为 T0-T15,图 4描述了热电偶的排列方式。热电偶 T0-T09 被安置了在表面燃料床里面, 而 T10 T15 被安置了在冠燃料床里面。在图 10中, 所选实验的树冠燃料床温度。
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/56591/56591fig10.jpg"> 
图 10: 燃料床气体温度皇冠燃料床热电偶排列在图 4中表示。显示的是 B 类试验, 没有表面燃料床和风速为1米/秒.<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig10large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/56591/56591fig11.jpg"> 
图 11: 由于不正确放置热电偶而导致的温度读数.热电偶排列在图 4中表示。描述的是用于顶部燃料床温度的数据, 在这种情况下, 热电偶不适当地放置在不正常的低温下。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56591/56591fig11large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
重要的是要注意, 如果热电偶没有正确地插入到燃料床, 温度读数将是不准确的。例如, 在检查以图 11表示的实验中的温度读数时, 人们注意到, 其中一个皇冠燃料床热电偶 (T15) 的温度低于正常燃烧条件。这些 temperatures 比燃烧 chamise 的气相温度更接近环境条件。因此, 据推测, 在这种情况下, 热电偶 T15 保持在燃料床外通过实验。

Watch this Scientific Journal Video about Wind Tunnel Experiments to Study Chaparral Crown Fires at JoVE.com

Wind Tunnel Experiments to Study Chaparral Crown Fires

本议定书描述风洞实验, 旨在研究从地面到查帕拉尔灌木树冠的火灾过渡。

查帕拉尔树冠火灾风洞实验研究

The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low ...

wind-tunnel-experiments-to-study-chaparral-crown-fires

Nanyang Technological University

Research

JoVE Journal

Engineering

9.6K 次观看.  University of California, Riverside. 本议定书描述风洞实验, 旨在研究从地面到查帕拉尔灌木树冠的火灾过渡。

视频: Wind Tunnel Experiments to Study Chaparral Crown Fires

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

白光干涉表面改性中的应用离子溅射，激光烧蚀，与摩擦学实验表征

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

科研

工程学

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

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 detailed observation, scenarios that make it challenging to observe with conventional imaging systems. One of these is the drop impact of liquids, which usually happens within one tenth of millisecond. To tackle this challenge, a fast imaging technique is introduced that combines a high-speed camera (capable of up to one million frames per second) with a macro lens with long working distance to bring the spatial resolution of the image down to 10 &#181;m/pixel. The imaging technique enables precise measurement of relevant fluid dynamic quantities, such as the flow field, the spreading distance and the splashing speed, from analysis of the recorded video. To demonstrate the capabilities of this visualization system, the impact dynamics when droplets of non-Newtonian fluids impinge on a flat hard surface are characterized. Two situations are considered: for oxidized liquid metal droplets we focus on the spreading behavior, and for densely packed suspensions we determine the onset of splashing. More generally, the combination of high temporal and spatial imaging resolution introduced here offers advantages for studying fast dynamics across a wide range of microscale phenomena.

Drop impact of non-Newtonian fluids is a complex process since different physical parameters influence the dynamics over a very short time (less than one tenth of a millisecond). A fast imaging technique is introduced in order to characterize the impact behaviors of different non-Newtonian fluids.

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 ...

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species&#8217; profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Gas sampling from laboratory-scale flames with online analysis of all species by mass spectrometry is a powerful method to investigate the complex mixture of chemical compounds occurring during combustion processes. Coupled with tunable soft ionization via synchrotron-generated vacuum-ultraviolet radiation, this technique provides isomer-resolved information and potentially fragment-free mass spectra.

火焰在实验的先进光源:全新洞察烟灰形成过程

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics ...

Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction.

Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape.

Disordered structures offer new mechanisms for forming photonic bandgaps and unprecedented freedom in functional-defect designs. To circumvent the computational challenges of disordered systems, we construct modular macroscopic samples of the new class of PBG materials and use microwaves to characterize their scale-invariant photonic properties, in an easy and inexpensive manner.

利用微波和电介质固体的宏观样本，研究无序光子带隙材料的光子特性

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). ...

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

使用超声波润滑实验一压电辅助摩擦试验机和光学轮廓

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

可视化潜流流通过底形用染料试验及仿真

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

A Robotic Platform to Study the Foreflipper of the California Sea Lion

The California sea lion (Zalophus californianus), is an agile and powerful swimmer. Unlike many successful swimmers (dolphins, tuna), they generate most of their thrust with their large foreflippers. This protocol describes a robotic platform designed to study the hydrodynamic performance of the swimming California sea lion (Zalophus californianus). The robot is a model of the animal&#39;s foreflipper that is actuated by motors to replicate the motion of its propulsive stroke (the &#39;clap&#39;). The kinematics of the sea lion&#39;s propulsive stroke are extracted from video data of unmarked, non-research sea lions at the Smithsonian Zoological Park (SNZ). Those data form the basis of the actuation motion of the robotic flipper presented here. The geometry of the robotic flipper is based a on high-resolution laser scan of a foreflipper of an adult female sea lion, scaled to about 60% of the full-scale flipper. The articulated model has three joints, mimicking the elbow, wrist and knuckle joint of the sea lion foreflipper. The robotic platform matches dynamics properties&#8212;Reynolds number and tip speed&#8212;of the animal when accelerating from rest. The robotic flipper can be used to determine the performance (forces and torques) and resulting flowfields.

A robotic platform is described that will be used to study the hydrodynamic performance&#8212;forces and flowfields&#8212;of the swimming California sea lion. The robot is a model of the animal&#39;s foreflipper that is actuated by motors to replicate the motion of its propulsive stroke (the &#39;clap&#39;).

机器人平台研究加州海狮的Foreflipper

The California sea lion (Zalophus californianus), is an agile and powerful swimmer. Unlike many successful swimmers (dolphins, tuna), they generate most ...

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

This manuscript describes an experimental procedure that allows obtaining diverse quantitative information on temporal and spatial evolution of water waves excited by time-dependent and steady wind forcing. Capacitance-type wave gauge and Laser Slope Gauge (LSG) are used to measure instantaneous water surface elevation and two components of the instantaneous surface slope at a number of locations along the test section of a wind-wave facility. The computer-controlled blower provides airflow over the water in the tank whose rate can vary in time. In the present experiments, the wind speed in the test section initially increases quickly from rest to the set value. It is then kept constant for the prescribed duration; finally, the airflow is shut down. At the beginning of each experimental run, the water surface is calm and there is no wind. Operation of the blower is initiated simultaneously with the acquisition of data provided by all sensors by a computer; data acquisition continues until the waves in the tank fully decay. Multiple independent runs performed under identical forcing conditions allow determining statistically reliable ensemble-averaged characteristic parameters that quantitatively describe wind-waves&#39; variation in time for the initial development stage as a function of fetch. The procedure also allows characterizing the spatial evolution of the wave field under steady wind forcing, as well as decay of waves in time, once the wind is shut down, as a function of fetch.

This manuscript describes a fully computer-controlled procedure that allows obtaining reliable statistical parameters from experiments of water waves excited by steady and unsteady wind forcing in a small-scale facility.

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 ...

Conducting Elevated Temperature Normal and Combined Pressure-Shear Plate Impact Experiments Via a Breech-end Sabot Heater System

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The method enables elevated temperature plate-impact experiments aimed towards probing dynamic behavior of materials under thermomechanical extremes, while mitigating several special experimental challenges faced while performing similar experiments using the conventional plate impact approach. Custom adaptations are made to the breech-end of a single-stage gas-gun at Case Western Reserve University; these adaptations include a precision-machined extension piece made from SAE 4340 steel, which is strategically designed to mate the existing gun-barrel while providing a high tolerance match to the bore and keyway. The extension piece contains a vertical cylindrical heater-well, which houses a heater assembly. A resistive coil heater-head, capable of reaching temperatures of up 1200 &#176;C, is attached to a vertical stem with axial/rotational degrees of freedoms; this enables thin metal specimens held at the front-end of a heat-resistant sabot to be heated uniformly across the diameter to the desired test temperatures. By heating the flyer plate (in this case, the sample) at the breech-end of the gun-barrel instead of at the target-end, several critical experimental challenges can be averted. These include: 1) severe changes in the alignment of the target plate during heating due to the thermal expansion of the several constituents of the target holder assembly; 2) challenges that arise due to the diagnostics elements, (i.e., polymer holographic gratings, and optical probes) being too close to the heated target assembly; 3) challenges that arise for target plates with an optical window, where crucial tolerances between the sample, bond layer, and window become increasingly difficult to maintain at high temperatures; 4) in the case of combined compression-shear plate impact experiments, the need for high-temperature resistant diffraction gratings for the measurement of transverse particle velocity at the free surface of the target; and 5) limitations imposed on the impact velocity necessary for unambiguous interpretation of the measured free surface velocity versus time profile due to thermal softening and possibly yielding of the bounding target plates.By utilizing the adaptations mentioned above, we present results from a series of reverse geometry normal plate impact experiments on commercial purity aluminum at a range of sample temperatures. These experiments show decreasing particle velocities in the impacted state, which are indicative of material softening (decrease in post-yield flow stress) with increasing sample temperatures.

Here, we present a detailed protocol of a new approach for conducting elevated temperature reverse normal plate impact, and combined pressure-and-shear plate impact. The approach involves the use of a breech-end resistive coil heater to heat a sample held at the front-end of a heat-resistant sabot to the desired temperature.

采用臀端穿甲弹加热系统进行高温常压联合压力-剪切板冲击试验

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The ...

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 ...