Dynamics of Micrometer-Sized Particles in a Separated Step Flow
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Particles in the diameter range from 1 to 70 μm were suspended in an air flow and the particle motion over a backward-facing step was measured by means of laser-Doppler anemometry. Thus, the local and integral flow quantities, i.e. the mean and turbulent velocity data could be measured precisely. In the experiments, monodispersed particle size distributions were used to exclude particle size related information ambiguity, known as triggering or size bias. The results of this study show qualitatively and quantitatively the difference in time-averaged particle dynamics for selected particle sizes in a backward-facing step flow. The experiments show the changes in the particle velocity field when compared with the velocity field of the continuous phase deduced from the 1 μm particles. Additionally, the results imply the strong influences which different particle sizes have on flow data measurement when size effects are not taken into account with particle-related optical measuring techniques.
KeywordsParticle Number Concentration Reattachment Length Step Flow Starch Particle Separate Flow Region
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