Ray tracing particle image velocimetry – Challenges in the application to a packed bed--颗粒学报PARTICUOLOGY

Velten, C., Ebert, M., Lessig, C., & Zähringer, K. (2024). Ray tracing particle image velocimetry – Challenges in the application to a packed bed. Particuology, 84, 194-208. https://doi.org/10.1016/j.partic.2023.06.003

Ray tracing particle image velocimetry – Challenges in the application to a packed bed

Christin Velten^a *, Mirko Ebert^b, Christian Lessig^b, Katharina Zähringer^a

a Lehrstuhl für Strömungsmechanik und Strömungstechnik, Otto-von-Guericke-Universität Magdeburg, 39106, Magdeburg, Germany
b Institut für Simulation und Graphik, Otto-von-Guericke-Universität Magdeburg, 39106, Magdeburg, Germany

10.1016/j.partic.2023.06.003

Volume 84, January 2024, Pages 194-208

Received 10 February 2023, Revised 31 May 2023, Accepted 2 June 2023, Available online 17 June 2023, Version of Record 30 June 2023.

E-mail: christin.velten@ovgu.de

Highlights

• Gas flow field measurement in transparent particle assemblies with ray tracing particle image velocimetry (RT-PIV).

• Distortion correction by a ray tracing based method.

• Detailed description of experimental setup and challenges appearing during application for RT-PIV.

• Step-wise validation of the ray tracing correction.

Abstract

Ray tracing Particle Image Velocimetry (RT-PIV) is an optical technique for high resolution velocity measurements in challenging optical systems, such as transparent packed beds, that uses ray tracing to correct for distortions introduced by transparent geometries in the light paths. The ray tracing based correction is a post processing step applied to the raw PIV particle images before classical PIV evaluation. In this study, RT-PIV is performed in the top layer of a body centred cubic (bcc) sphere packing with gaseous flow, where optical access is obtained by the use of transparent N-BK7 glass balls with a diameter of d=40 mm. RT-PIV introduces new experimental and numerical challenges, for example a limited field of view, illumination difficulties, a very large required depth of field and high sensitivity to geometric parameters used in the ray tracing correction. These challenges and their implications are the main scope and discussed in the present work. Further, the validation of the ray tracing reconstruction step is presented and examples for the obtained corrected vector fields in a packed bed are given. The results show the strength of the method in reconstructing velocity fields behind transparent spheres that would not have been accessible by optical measurement techniques without the ray tracing correction.

Graphical abstract

Keywords

Ray tracing particle image velocimetry (RT-PIV); Transparent spherical particles; Packed bed; Distortion correction; Gas flow

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