双平面立体PIV

The unsteady organization and temporal dynamics of the interaction between a planar shock wave impinging on a turbulent boundary layer at a free stream Mach number of M∞=1.69 is investigated experimentally by means of dual-plane Particle Image Velocimetry (dual-PIV). Two independent PIV systems were combined in two component mode to obtain instantaneous velocity fields separated by a prescribed small time delay. This enables to obtain, in addition to mean and statistical flow properties, also instantaneously time resolved data to characterize the temporal dynamics of the flow phenomenon in terms of time scales, temporal correlations and convective velocities. The characteristic time scales for the incoming boundary layer, the separation region and the reflected shock are evaluated by means of measuring the temporal auto-correlation coefficient in the complete flow field for a range of time delays from 5 ms to 2000 ms. These auto-correlation fields are used to quantify the time scales in selected regions of the flow. This permits resolving the dominant time scales within the boundary layer and the interaction region. I. Introduction

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.

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.