This note reports a particle image velocimetry technique for obtaining fully resolved measurements of the velocity field u(x,y,z,t) throughout a four- dimensional spatiotemporal region on the inner scale in a near-isotropic stationary turbulence generated by a pair of vibrating grids in a water tank. The method uses a high-speed successive sweeping laser sheet and two synchronous high-speed stereo CCD cameras combined with a fast image processing system, so that the underlying full spatial velocity field and the corresponding kinetic energy dissipation rate field can be determined. Measurements confirm that the distribution of the dissipation rate field is a highly intermittent phenomenon, in which high kinetic energy dissipation rates occur infrequently and are correlated with regions of high principal strain rate, in consistent with the results found by Sreenivasan & Antonia. The fine structures of the kinetic energy dissipation rate field in the present turbulence are complex, containing line-like, blob-like, and sheet-like structures with the diameter, size, and thickness ranging in scale from 1 to 6 Kolmogorov scale (η) with a mean of about 3η. These data are useful for investigating topological features of fine structure turbulence.
|主出版物標題||IUTAM Symposium on Reynolds Number Scaling in Turbulent Flow: Proceedings of the IUTAM Symposium held in Princeton, NJ, U.S.A., 11–13 September 2002|
|編輯||Alexander J. Smits|
|出版狀態||已發佈 - 2004|