Improved GSI out-of-focus technique for application to dense sprays and PIV measurements.

An improved scheme for the GSI out of focus technique is proposed. The new approach makes use of double laser pulses with crossed polarizations and of a single CCD for the image acquisition. The use of different polarizations permits a fine recognition of the droplet doublet images from which the velocity of each droplet is determined in addition to its diameter. The new scheme improves the signal to noise ratio and decreases data rejection, thus permitting the extension of the technique to dense sprays. More, the utilisation of beams with different polarisations permits to determine also the velocity direction beside its modulus.