A technique for two-colour particle image velocimetry.

Abstract

To study the complex flowfields found in combustion, it is often necessary to acquire an instantaneous overall view of the flowfield. One method of achieving this is two-dimensional velocity mapping with particle image velocimetry (PIV). A two-colour PIV experimental apparatus has been developed expressly to meet the demands of combustion and related flowfields. This technique offers advantages over other PIV methods in that the absolute velocity vector direction is known and data processing requirements are reduced. A method for calculating the mean exposure from particles on colour film, based on Mie scattering theory, is developed. A technique optimized for analysis of two-colour PIV images is described. Two-colour PIV is demonstrated in the wake of a noncombusting n-heptane fuelled bluff-body burner, which presented a suitably complex flowfield including counter-rotating recirculation zones and centreline stagnation points. To complement these results, mean velocities obtained with LDA are also presented. This is the first report of spray velocity measurement by PIV.