Local field correction PIV, implemented by means of simple algorithms, andmultigrid versions

Local field correction particle image velocimetry (LFCPIV), which was first presented in 1997, is the only correlation PIV method able to resolve flow structures smaller than the interrogation window. It presents advantages o ver conventional systems and thus offers an alternative in the field of sup er-resolution methods. Improvements of the initial version are likely to pr omote its application even further. The issues defining some of these possi ble improvements were already indicated in the paper that originally introd uced LFCPIV, but not developed. This work presents refinements and also sim plifications of the technique, so that it can be applied using current algo rithms of advanced correlation PIV systems. Furthermore, these refinements reduce the measurement error and enlarge the range of application of LFCPIV . In particular, the application of the system is no longer constrained to images with mean distances between particles larger than 4 pixels. Besides that, the use of interrogation windows smaller than in its previous version is evaluated. This allows multigrid LFCPIV implementations. The results sh ow how multi.-rid LFCPIV can obtain better measurements than can the usual multigrid PIV, but still the refined version of the LFCPIV technique perfor ms even better, at the expense of a larger computing time. The performance of these methods is evaluated for synthetic and real images. This includes examples in which the ability to cope with gradients in velocity, gradients in seeding density and the presence of boundaries is highlighted.