Large-scale coherent structures and three-dimensional velocity estimation in the turbulent wake of a low aspect ratio surface-mounted cone
Abstract
The turbulent wake of a low-aspect-ratio right angle cone mounted on a flat surface, partially submerged in a steady turbulent boundary layer, is investigated using planar Stereoscopic Particle Image Velocimetry (SPIV) in a wind tunnel and Large Eddy Simulation (LES). The description of the dynamics of the large-scale quasi-periodic flow structures and their estimations using remote pressure sensors are considered in this study. The dominant vortex structures are first extracted from SPIV data using the traditional phase average method, which yields an average coherent velocity field that represents a typical shedding cycle. The formation and evolution of these large structures are visualized using volume rendering techniques and analyzed in the framework of vorticity dynamics. To go beyond the typical shedding cycle description, a technique to estimate the three-dimensional flow field from uncorrelated velocity measurements is presented. The method utilizes simultaneous pressure sensors mounted on the solid wall boundary in conjunction with the planar SPIV measurements. Compared to the typical shedding cycle representation, the technique can also characterize the low frequency modulation of the vortex shedding process. The capability of this technique to estimate the three-dimensional flow field is then assessed us- ing LES by applying the estimation techniques to planar LES velocity fields and comparing the results to the actual three-dimensional velocity field available from the simulation. The velocity estimation is found to be consistent with the actual three-dimensional velocity field. Additional coherent motions that are not captured in the experiment are also identified with the LES results, and strategies to capture these motions in SPIV measurements are developed based on the numerical data.
Description
Keywords
Fluid and Plasma, Engineering--Aerospace, Engineering--Environmental, Engineering--Mechanical
Citation
Chen, Z. (2017). Large-scale coherent structures and three-dimensional velocity estimation in the turbulent wake of a low aspect ratio surface-mounted cone (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26725