Laser pulse separation measurements for spectral flow analysis using particle image velocimetry

Abstract

A feedback methodology is developed for the correction of timing errors in double pulse laser systems operating at high repetition frequencies. With continuing developments in non-intrusive measurement techniques, such as particle image velocimetry, there is an ever-increasing demand for simultaneous high spatial and temporal resolution, which can make them well suited to the spectral characterization of fluid flows. This application places significant importance on the accuracy and repeatability of the timing between successive laser pulses of high-speed, double-pulsed laser systems, as any timing errors propagate directly into the computed velocity vectors and indirectly into all other derived quantities, including the spectral analysis of the flow. The present work proposes a feedback methodology to measure and correct for such errors in a time-resolved manner. Lastly, the proposed methodology is demonstrated on a test case of a cylinder wake, and the results are compared to corresponding hotwire measurements.

Keywords

• timing error
• particle image velocimetry (piv)
• double-pulsed laser
• power spectra
• hot wire anemometry