Color-VTR image analysis on catastrophic deformations of water waves

水波灾难性变形的彩色 VTR 图像分析

• 批准号: 05452242
• 负责人: NISHIMURA Hitoshi
• 金额: $ 4.29万
• 依托单位: University of Tsukuba
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452242/
• 关键词: hydraulic experiment; flow visualization; velocity field; color-VTR image analysis; wave breaking; wave overtopping; 内部流速場測定

Technology of spatial correlation analysis of high-speed color-VTR imageries was developed for investigating flow mechanisms of catastrophic wave deformations such as breaking and overtopping. Polystirene beads were used as tracers for flow visualization. Trials and errors were repeated to determine the optimum conditions of tracer mixing, lighting, video recording, and frame sizes in image analysis.Statistics of pixelwise data implies that further improvement in visualization techniques are required to obtain imageries with widely ranged colortones. In this study, flow velocity detection with high reliability was realized by taking advantage of quantitative increase in graded brightness data, that is, by incorporating three correlation coeffcients for red, green, and blue component imageries. Accuracy and reliability of velocity vector fields thus obtained were examined through evaluation of residual error in terms of flow continuity.Solitary wave overturning over a fixed slope was reproduced in an experimental basin, and internal flow velocities were extracted. Thorough description of velocity fields allowed the deduction of pressure and vorticity fields. Extremely mild pressure gradient thus found in the wave crest region may play an essential role in the breaking phenomenon. Notable vorticity was observed below the water surface on the rear side of the crest.A vertical breakwater model was installed for investgation of the flow field in an overtopping solitary wave. A predominant shear-flow appeared near the upper-front corner of the breakwater, where strong vorticities were detected. The overtopping flow velocity is high in general under the wave crest, and its maximum appeared slightly below the surface.

开发了高速彩色VTR成像的空间相关性分析技术，用于研究灾难性波浪变形（例如破裂和超上）的流动机制。聚类珠被用作可视化流动的示踪剂。重复试验和误差，以确定图像分析中的示踪剂混合，照明，视频记录和框架大小的最佳条件。像素方向数据的统计数据意味着，需要进一步改进可视化技术以获得具有广泛范围的clort酮的成像。在这项研究中，通过利用分级亮度数据的定量增加，即通过结合红色，绿色和蓝色分量成像的三个相关系数来实现具有高可靠性的流速度检测。通过评估剩余误差在流量连续性方面，检查了速度矢量场的准确性和可靠性。在实验盆地中复制了固定斜率上的固定波，并提取了内部流量速度。详细描述速度场允许扣除压力和涡度场。因此，在波峰区域中发现的极度轻度压力梯度可能在破裂现象中起着至关重要的作用。在冠的后侧的水面下方观察到了显着的涡度。安装了垂直的防波堤模型，以在超大的孤立波动中投资流场。在防波堤的上前角附近出现了主要的剪切流，在那里检测到了强烈的涡度。在波峰下，高顶速度通常很高，其最大值出现在表面以下。