Simulation experiment concerning applicability of digital image processing system using correlation method.

In the previous report, velocity vectors and vorticity contours of an unsteady viscous diffusing free doublet flow field were analyzed using a digital image processing system based on the correlation method. In it a serious problem was pointed out oncerning the identification of the tracers using the correlation method for the flow patterns with sharp gradients of velocity and great vorticity. The purpose of the present study is to propose a quantitative limit of the applicability of the digital image processing system using the correlation method. Some experimental simulations were carried out employing the analytical solution of the same doublet flow field as a flow model. The effects of the correlation region size on the erroneous vectors due to the sharp gradient of velocity and great vorticity were discussed in detail.