Tomographic-PIV와 Volume-PTV에 의한 실린더 후류 계측

Abstract

3D-PTV (Volume PTV) measurements and Tomographic PIV measurements have been carried out for the measurements of the wakes around a cylinder. These techniques makes use of several simultaneous views of the illuminated particles and their 3D reconstruction as a centroid of particle for the volume PTV and as a light intensity distribution for the tomographic PIV.

For 3D-PTV measurements, two-camera system has been adopted using the conventional photogrammetry technique and the particle tracking algorithm. For tomographic PIV measurement, the MART algorithm, two-camera system has been adopted using the tomographic concept for the images reconstructed by multiple cameras. In this tomographic PIV, a 3D array of light intensity is yielded and discretized over voxels, and the reconstructed tomogram pair is analyzed by means of 3D cross-correlation with an iterative multigrid volume deformation technique, returning the three-component velocity vector distribution over the measurement volume. Detailed process for these techniques are discussed and a parametric study is carried out by means of a computer-simulated volume-PIV procedure.

The performances of the tomographic PIV technique have been discussed. In the performance test, a computer simulated experiment of a 3D particle motion field describing a vortex ring demonstrates the capability and potential of the proposed system with four cameras.

The capability of the technique in real experimental conditions is assessed with the measurement of the turbulent flow in the wake of a circular cylinder at Reynolds 630. And then its results are compared with the results obtained by the volume PTV in same experimental condition.