Comparison between optical flow and cross-correlation methods for extraction of velocity fields from particle images

OpenOpticalFlow: An Open Source Program for Extraction of Velocity Fields from Flow Visualization Images

“…An error analysis of the optical flow method was given by Liu et al [11]. The general estimate for the total error of optical flow computation is given by:…”

“…In the second step, a simple scheme for correcting local illumination intensity changes is also based on the application of a Gaussian filter [11]. The selection of the std (or size) of a Gaussian filter is important to determine the local averaged intensity value for correction.…”

“…The time step ∆t is used to control the maximum displacement in synthetic particle images. This flow with particle images has been used as a typical case in the simulations to evaluate the accuracy of the optical flow method [11].…”

“…Physically, the optical flow is proportional to the light-ray-path-averaged velocity of fluid (or particles) weighted in a relevant field quantity like dye concentration, fluid density or particle concentration. The optical flow method has been used to study the flow structures of Jupiter's Great Red Spot (GRS), impinging jets, and laser-induced underwater shock wave [8][9][10][11]. A mathematical analysis of the variational solution of the optical flow and an iterative numerical algorithm are given by Wang et al [12].…”

“…A mathematical analysis of the variational solution of the optical flow and an iterative numerical algorithm are given by Wang et al [12]. The systematical error analysis of the optical flow method in velocity measurements is given by Liu et al [11] in comparison with the well-established cross-correlation method in particle image velocimetry (PIV).…”