The measurement of a free air jet using particle image velocimetry (PIV) and laser doppler anemometry (LDA)

摘要

The velocity of a free jet emitted from a 120 mm{sup}2 nozzle has been measured using both Particle Image Velocimetry, (PIV), and Laser Doppler Anemometry, (LDA). The measurements were made by the University of Warwick and DERA respectively.The PIV data was captured at video rate using a CCD camera and frame grabber. The PW data has been analysed in two ways. Firstly a correlation technique has been used to provide a local spatially averaged but near instantaneous measurement of a singlevideo frame. Secondly, the same frame has also been analysed using a particle tracking method to remove the spatial averaging. The intensity distribution of the particle images has been used to estimate the image centres according to the centre of massapproximation. The time averaged result of the sequence of video frames, analysed using particle tracking, is also presented for comparison with the LDA data.