Feasibility study of three-dimensional PIV by correlating images of particles within parallel light sheet planes

Abstract

Large velocity components perpendicular to the light sheet plane leads to a significant reduction of valid data points and errors due to perspective projection of the imaging lens in PIV experiments. Therefore, the observation of flows with a strong out-of-plane flow component requires the measurements of this component in order to reduce the error of both measured in-plane components. It is know that when utilizing statistical evaluation methods in PIV, such as cross- or autocorrelation methods, the height of the peak in the correlation plane decreases with increasing out-of-plane velocity components. Thus, one aproach obtaining information about the out-of-plane velocity component from PIV recordings is to analyze the height of the peak in the correlation plane. This value depends on the portion of paired particle images, which itself depends on the out-of-plane velocity component and on other parameters. To circumvent problems with other influences (e.g. background light, varying image sizes and numbers), images from another light sheet plane parallel to the firstare also captured for peak height normalization. Our experimental results show the feasibility of an out-of-plane velocity estimation by analyzing the correlation of particles imaged in parallel light sheet planes.