title: Scattering effects at near-wall flow measurements using Doppler global velocimetry.
abstract: Doppler global velocimetry (DGV) is considered to be a useful optical measurement tool for acquiring flow velocity fields. Often near-wall measurements are required, which is still challenging due to errors resulting from background scattering and multiple-particle scattering. Since the magnitudes of both errors are unknown so far, they are investigated by scattering simulations and experiments. Multiple-particle scattering mainly causes a stochastic error, which can be reduced by averaging. Contrary to this, background scattering results in a relative systematic error, which is directly proportional to the ratio of the background scattered light power to the total scattered light power. After applying a correction method and optimizing the measurement arrangement, a subsonic flat plate boundary layer was successfully measured achieving a minimum wall distance of 100 μm with a maximum relative error of 6%. The investigations reveal the current capabilities and perspectives of DGV for near-wall measurements.
authors.affiliation: Laboratory for Measurement and Testing Techniques, Technische Universität Dresden, Helmholtzstr. 18, 01062 Dresden, Germany. andreas.fischer2@tu‐dresden.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Fischer
authors.forename: Daniel
authors.initials: D
authors.lastname: Haufe
authors.forename: Lars
authors.initials: L
authors.lastname: Büttner
authors.forename: Jürgen
authors.initials: J
authors.lastname: Czarske