title: High dynamic velocity range particle image velocimetry using multiple pulse separation imaging.
abstract: The dynamic velocity range of particle image velocimetry (PIV) is determined by the maximum and minimum resolvable particle displacement. Various techniques have extended the dynamic range, however flows with a wide velocity range (e.g., impinging jets) still challenge PIV algorithms. A new technique is presented to increase the dynamic velocity range by over an order of magnitude. The multiple pulse separation (MPS) technique (i) records series of double-frame exposures with different pulse separations, (ii) processes the fields using conventional multi-grid algorithms, and (iii) yields a composite velocity field with a locally optimized pulse separation. A robust criterion determines the local optimum pulse separation, accounting for correlation strength and measurement uncertainty. Validation experiments are performed in an impinging jet flow, using laser-Doppler velocimetry as reference measurement. The precision of mean flow and turbulence quantities is significantly improved compared to conventional PIV, due to the increase in dynamic range. In a wide range of applications, MPS PIV is a robust approach to increase the dynamic velocity range without restricting the vector evaluation methods.
authors.affiliation: Mechanical Engineering Department, Parsons Building, Trinity College, Dublin 2, Ireland. tso1@hw.ac.uk
authors.forename: Tim
authors.initials: T
authors.lastname: Persoons
authors.forename: Tadhg S
authors.initials: TS
authors.lastname: O'Donovan