Experimental Investigation of 3D Velocity by Tomographic Particle Image Velocimetry (Tomo-PIV) in a Short Riser Section

Abstract

The measurement of instantaneous velocity field with high spatial resolution makes the Tomo-PIV (tomographic particle image velocimetry) technique attractive for the study of complex flows in circulating beds. The Tomo-PIV technique is employed for obtaining the velocity field of the fluid phase in three dimensions using tracer particles which follow the fluid. They are immersed in the fluid and illuminated by a source of pulsed light (laser) within a three-dimensional region. Images of the particles are recorded in the focus of several viewing directions using CCD (Charge-Coupled Device) sensors. The distribution of light intensity is discretized into a 3D array of voxels and then analyzed by interrogation of cross-correlation in three dimensions. The information field is returned in the form of instantaneous velocities of the measurement volume. This paper aims to present an experimental setup for an initial investigation of the velocity field of the particulate phase of a riser section of a circulating bed. The calibration errors were between 0.209 and 0.066 pixels and after the self-calibration errors were below 0.097 pixels. The volume investigated was 82 x 100 x 10 mm 3 with a resolution of 1571 x 897 x 113 voxels. The reconstructed volumes were processed using 3D cross-correlation with a volume interrogation size of 110 voxels decreasing to a final size of 16 voxels with a 75% overlap between adjacent interrogation volumes. The velocity field produced has 224 x 393 x 28 voxels.