Gas-phase velocity field measurements in sprays without particle seeding

A laser-based technique is presented that can be used to measure the instan taneous velocity field of the continuous phase in sprays and aerosols. In c ontrast to most well established laser-based velocity measurement technique s, this method is independent of particle seeding and Mie scattering. Inste ad of that it is based on gaseous flow tracers and laser-induced fluorescen ce (LIF). Inhomogeneous tracer gas distributions, which are created by an i ncomplete, turbulent mixing process, are exploited for flow tracing. The ve locity field can be measured close to the droplets, because frequency-shift ed LIF is separated from Mie scattering by optical filters. Validation test s and results from a water spray in air are given. Accuracy and spatial res olution are discussed in detail.