Print Email Facebook Twitter The slip velocity of nearly neutrally buoyant tracers for large-scale PIV Title The slip velocity of nearly neutrally buoyant tracers for large-scale PIV Author Engler Faleiros, D. (TU Delft Transport Engineering and Logistics; Royal Netherlands Aerospace Centre NLR) Tuinstra, Marthijn (Royal Netherlands Aerospace Centre NLR) Sciacchitano, A. (TU Delft Aerodynamics) Scarano, F. (TU Delft Aerodynamics) Date 2021 Abstract The behaviour of nearly neutrally buoyant tracers is studied by means of experiments with helium-filled soap bubbles and numerical simulations. The current models used for estimating the slip velocity of heavy micro particles and neutrally buoyant particles are reviewed and extended to include the effect of unsteady forces and particle Reynolds number. The particle motion is analysed via numerical simulations of a rectilinear oscillatory flow and in the flow around an airfoil within a particle flow parameter space that is typical of large-scale PIV experiments. An empirical relation is obtained that estimates the particle slip velocity, depending on the particle-to-fluid density ratio, the particle Reynolds number and frequency of the local flow fluctuations. The model developed is applied to assess the slip velocity of helium-filled soap bubbles in a large-scale experiment conducted at the German–Dutch wind (DNW) tunnels in the flow around an airfoil, with chord Reynolds numbers up to three millions. Furthermore, a procedure is proposed that can be used to retrieve the bubbles mean density and dispersion from measurements of mean velocity and fluctuations, respectively. Graphic abstract: [Figure not available: see fulltext.] To reference this document use: http://resolver.tudelft.nl/uuid:d1a38ea9-afde-4a88-8200-71a82ce14fd1 DOI https://doi.org/10.1007/s00348-021-03274-9 ISSN 0723-4864 Source Experiments in Fluids: experimental methods and their applications to fluid flow, 62 (9) Part of collection Institutional Repository Document type journal article Rights © 2021 D. Engler Faleiros, Marthijn Tuinstra, A. Sciacchitano, F. Scarano Files PDF Faleiros2021_Article_TheS ... eutral.pdf 6.11 MB Close viewer /islandora/object/uuid:d1a38ea9-afde-4a88-8200-71a82ce14fd1/datastream/OBJ/view