德国LaVision 表面PIV

本文介绍了浅水流动表面的大尺度PIV测量方法，详细介绍了实验设备和不用激光照明进行PIV测量的技术途径。特别研究了在表面流动分析时示踪粒子的选择和播撒方法。

In this report we present the methodology we are using in the AMI group to compare optic flow estimation methods in the context of the FLUID Specific Targeted Research Project - Contract No 513633 founded by the CEE. The main goal of this report is to try to unify comparison criteria between the different parnerts in order to share information and conclusions. We think that it is one of the topics we have to address in Las Palmas Meeting December next. In order to describe the methodology we use, we divide it in five steps: 1. We choose a number of optic flow estimation methods 2. We choose an image sequence dataset to apply the methods. 3. We apply the methods and we store the results in a ASCII file using an standard format 4. We define a number of statistics to compare the methods (we use the ASCII files as basic information to compare). 5. We compute the statistics for each pair of methods and we generate tables with the information. To help result interpretation we use arrow images and in the case we know the optic flow groundtruth we generate image to provide the information about what method perform better in the different areas of the image. To illustrate this approach and to fit ideas we present the results of this approach in a particular image sequence provided by LaVision in sections from 1.1 to 1.4. Then, in section 2 we remark some of the difficulties we have found in our work, which should be discussed in order to be able to compare results provided by all the partners of the FLUID project.

Many materials, such as paints, clay suspensions, concrete or inks, are complex fluids which present non-Newtonian properties. To define their rheological properties and particularly for coarse suspensions (debris mud, sediments…), we need to develop specific devices because of the size of the particles within the fluid to reach the continuum assumption. The study of the inclined plane flows can be a solution as soon as we are able to measure the evolution of the free surface and the surface velocity during the flow. We have developed specific 3D measurements based on stereovision to extract rheological properties of two materials flowing down an inclined flow. First a shear thinning fluid (a polyoxyde ethylene solution) is used to validate the method which is then applied to a viscoplastic material (a bentonite suspension). The comparison of the results with conventional measurements using a rheometer is in good agreement.

PIV systems rely on a combination of seed particles, laser light intensity, and camera positioning to collected velocity data. Careful attention is needed when selecting the ap- propriate setup conguration for PIV systems. This paper focuses on several areas for improvement in PIV data collection for a compressible turbulent boundary layer study on a at plate using MVG's. The topics include determining the seed particle surface preparation for a at plate, and PIV system conguration.