An experimental technique for coupled high-resolution full-scale PIV and load measurements in water tunnel

Wind and water tunnels are key platforms for the study of the dynamics of boundary layers and flows past objects, utilizing load-cell measurements, particle image velocimetry, dye visualizations, etc. In such measurements, size of the setup and the sample as well as proximity to the ideal theoretical boundary layer model can be limiting factors on the type and resolution of the data collected. In this talk, I introduce a variation in the experimental technique, to perform high-resolution 2D-2C PIV measurements of relatively large samples, with simultaneous load measurements via a 2-axis load-cell. In this setup, the sample is attached to the load-cell and kept fixed in the water tunnel, while the optical elements are arranged to allow for all sides of the samples to be illuminated and thus avoid any shadows, and the high-speed camera is controlled via a 3-axis CNC, motorized stage. To perform measurements of the entire sample and achieve a high-resolution view of the boundary layer profiles close to the wall, the experimental procedure is then repeated in overlapping steps by systematically moving the camera via the CNC stage. Ultimately, to analyze the results, the images are stitched back together to get the full view of the sample and the velocity distribution in the fluid. As a case study, I present the experiments performed with a flat plate sample which its leading edge has an elliptical streamlined form. I will explore the velocity and load measurements, and how access to the entire velocity field data can be used to decompose the forces into viscous and pressure based components and compare the results with previous experimental and theoretical models. Lastly, I will discuss how this setup can be utilized to study more complex flow scenarios around single or many objects.