DSPIV Measurements of Velocity Gradient Tensor Fields in Turbulent Flows
Abstract
A dual-plane stereo particle image velocimetry (DSPIV) technique allows highly-resolved measurements of the full nine-component velocity gradient tensor field partial u_i/ partial xj at the quasi-universal intermediate and small scales of turbulent shear flows. The method is based on two simultaneous, independent stereo PIV measurements in differentially-spaced light sheet planes. Thickness, separation, coincidence, and parallelism of the light sheets dictates the resolution and accuracy. Overall errors including limits on the accuracy of independent dual light sheet generation and positioning are found from coincident-plane imaging tests to be 9% and 16% in the in- and out-of-plane derivative components. Separated-plane imaging tests in a turbulent shear flow show excellent similarity in the components of partial u_i/ partial x_j, and give mean-square gradient values within 1-4% of ideal isotropic limit values. Resulting measured divergence values indicate overall rms errors of 8.9% and 11.7% in the off- and on-diagonal components of the velocity gradients.
- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- November 2004
- Bibcode:
- 2004APS..DFD.EP001M