The setting parameters of the image enhancement times, the threshold level of the image binarization, and the size of the detecting area were investigated to confirm the accuracy of the four-time-step PTV. The particle density formed the peak distribution as a function of the threshold level of image binarization, and the peak decreased and flattened with the increase of the image enhancement times. Therefore, the wide valid selection of the threshold level of the image binarization and the preservation of high particle density were realized when the image sharpness times was set to be the upper limit of the adequate particle density for four-time-step PTV. Furthermore, as the tendency of the occurring ratio between the correct and error velocity suddenly changed with the variation of the size of detecting area of four-time-step PTV, the size of detecting area was set around that boarder to acquire the velocity field effectively.
