Resolving Flow Structures Inside Three Dimensional Packed Beds With Gas Flow By Ray Tracing Particle Image Velocimetry

Abstract

Two different configurations are investigated in this study by ray tracing Particle Image Velocimetry to access the interior of different spherical packing structures. Configuration 1 consists of a regular bidisperse packed bed of 10mm and 40mm spheres based on a body-centered cubic arrangement. Ray tracing Particle Image Velocimetry was performed behind two spheres in the 40mm layer for particle Reynolds numbers from 200 to 700. The averaged velocity flow fields show the jet structures according to the pores between the underlying smaller spheres and the influence of the large spheres. Since ray-tracing Particle Image Velocimetry suffers from experimental and numerical limitations, planar 2D Particle Image Velocimetry measurements are performed to obtain spatially highly resolved validation data in the optically accessible void pores. These measurements were performed at different height positions in the bed showcasing that similar flow fields appear in the different pores. Configuration 2 deals with the jet flow (Re=5900) around an individual sphere, part of a body-centred cubic arrangement of d=40mm spheres. The emphasis lays on the temporally resolved snapshot data of the turbulent jet flow obtained by ray tracing Particle Image velocimetry. Data obtained from both configurations is used for a comprehensive discussion of the chances and challenges of ray tracing Particle Image Velocimetry. Limitations appear on the experimental side, like generation of depth of field, illumination and reflections, sufficient measurement signal, and accuracy of the geometry, but also on the numerical side, like the reproduction of the geometry, material properties, and real-world conditions. Since all these phenomena are interlinked, performing the ray tracing method in more complex systems is questionable.