Statistical Results Concerning the Precision of the Methods of Correlation and Interpolation Sub-Pixel Used in Video PIV
INSTITUT FRANCO-ALLEMAND DE RECHERCHES SAINT-LOUIS (FRANCE)
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In this report, large lines of an analytical model allowing the calculation of the levels of gray delivered by a CCD camera at the time of shooting by the Velocimetry by Images of Particles PIV method are recalled. The image of the particles illuminated by the laser plan is given starting from a relation of convolution between the impulse response of the objective and the geometrical image of these particles, and the CCD camera is modelled by effects of space integration, of profit and of quantification. This model is validated on a precise case of shootings of PIV. The principles of the traditional methods of correlation autocorrelation and cross correlation and of interpolation subpixel barycentre, adjustment by parabolic and Gaussian function allowing the determination of displacement of the particles are also pointed out. This report continues with the numerical simulations, based on the preceding model, corresponding to two configurations of particles the first configuration relates to the ideal case of only one particle with surface of interrogation and the second configuration, the more realistic case, of a variable number of particles per surface of interrogation. In these two configurations, the sources of noise are not taken into account.