​ ​Seminar on PIV-based pressure reconstruction and its application

Associate Professor Gao Qi

 School of Aeronautics and Astronautics, Zhejiang University

Pressure reconstruction technique based on particle image velocimetry (PIV) is a non-invasive optical measurement technology developed in the past ten years. It requires first obtaining a time-resolved experimental data of the velocity field and then solving the pressure field based on the governing equation of fluid mechanics. The whole process is divided into three parts: the velocity field is obtained by the time-resolved PIV measurement, the pressure gradient field is calculated by the velocity field, and the pressure field is obtained by integrating the pressure gradient field. The accuracy and uncertainty of the integral result depends on the integral path. In this work, an irrotation correction (IC) and orthogonal path integration method are proposed. By performing the irrotation correction on the calculated pressure gradient field, the dependence of the integral result on the integral path is significantly reduced, so that the pressure field can be solved by applying only a very small number of orthogonal path integrals, and the accuracy of the reconstructed pressure field is well improved. A hemispherical model was used to artificially generate the horseshoe vortex in the laminar boundary layer, and the time-resolved PIV measurement was achieved. The time-resolved three-dimensional velocity of the whole flow field was obtained, so that the flow characteristics, especially the generation, evolution and interaction of the horseshoe vortex, were studied in detail. Furthermore, through the PIV-based pressure reconstruction technique, the three-dimensional pressure field of the flow is calculated, and the mechanism of the evolution of the flow structures is further analyzed from the pressure.

Dr Qi Gao received his bachelor's degree from Zhejiang University in 2001, his master's degree from Tsinghua University in 2005, and his Ph.D. from the University of Minnesota in 2011. He joined the Beijing University of Aeronautics and Astronautics as an assistant professor in 2011, and was promoted to associate professor in 2013. He is currently an associate professor at the School of Aeronautics and Astronautics, Zhejiang University, China, since 2018, and serves as the Director of Laboratory of Fluid Mechanics at the Institute of Fluid Engineering. Dr. Gao's research is broadly in the area of experimental fluid mechanics. Current projects focus on developing techniques of volumetric velocimetry and their applications. Studies on turbulent boundary layers, cardiovascular flows, compressible flows and flow control are highly interested. He has published over 20 papers and applied for 28 Chinese patents (8 certificated). Dr. Gao recently received the Chinese National Award of Technology Invention (second class, 2018) as the second inventor.