We report on the dynamics and structure of the turbulent velocity field in a high-Rayleigh-number (Ra = 5.9 x 10(8))thermal convection cell with an aspect ratio of 4. Spectral density functions (measured with laser Doppler velocimetry) indicated the existence of a large-scale periodic component. The long-time mean flow field (measured with particle image velocimetry) revealed that the large-sca...

We suggest an approach to probing intermittency corrections to the Kolmogorov law in turbulent flows based on the autoregressive moving-average modeling of turbulent time series. We introduce an index Υ that measures the distance from a Kolmogorov-Obukhov model in the autoregressive moving-average model space. Applying our analysis to particle image velocimetry and laser Doppler velocimetry mea...

We studied the grid-generated turbulence by using Particle Image Velocimetry (PIV) technique. test on this already well flow new ways of analyzing spatially resolved PIV data, such as spatial spectra and structure functions. compare some characteristics with results Laser Doppler Anemometry (LDA).

Imaging flow velocity measurements are essential for the investigation of unsteady complex flow phenomena, e.g., in turbomachines, injectors and combustors. The direct optical measurement on fluid molecules is possible with laser Rayleigh scattering and the Doppler effect. However, the small scattering cross-section results in a low signal to noise ratio, which hinders time-resolved measurement...

A new measurement technique is being developed by NASA to measure off-surface flow fields. This method, Doppler global velocimetry, will allow quantification of complex three-dimensional flow fields at video camera rates. The entire flow field structure within a selected plane is measured simultaneously rather than by scanned, point-by-point measurements using conventional laser velocimetry. To...