Helium-filled soap bubbles tracing fidelity in wall-bounded turbulence
| Autor: | Andrea Sciacchitano, David Engler Faleiros, Fulvio Scarano, Marthijn Tuinstra |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Fluid Flow and Transfer Processes
Physics Soap bubble Buoyancy Turbulence Bubble Computational Mechanics General Physics and Astronomy Reynolds number Mechanics engineering.material Boundary layer thickness 01 natural sciences 010305 fluids & plasmas 010309 optics Physics::Fluid Dynamics symbols.namesake Particle image velocimetry Mechanics of Materials Particle tracking velocimetry 0103 physical sciences engineering symbols |
| Zdroj: | Experiments in Fluids: experimental methods and their applications to fluid flow, 59 |
| ISSN: | 0723-4864 |
| Popis: | The use of helium-filled soap bubbles (HFSB) as flow tracers for particle image velocimetry (PIV) and particle tracking velocimetry (PTV) to measure the properties of turbulent boundary layers is investigated in the velocity range from 30 to 50 m/s. The experiments correspond to momentum thickness-based Reynolds numbers of 3300 and 5100. A single bubble generator delivers nearly neutrally buoyant HFSB to seed the air flow developing over the flat plate. The HFSB motion analysis is performed by PTV using single-frame multi-exposure recordings. The measurements yield the local velocity and turbulence statistics. Planar two-component-PIV measurements with micron-sized droplets (DEHS) conducted under the same conditions provide reference data for the quantities of interest. In addition, the behavior of air-filled soap bubbles is studied where the effect of non-neutral buoyancy is more pronounced. The mean velocity profiles as well as the turbulent stresses obtained with HFSB are in good agreement with the flow statistics obtained with DEHS particles. The study illustrates that HFSB tracers can be used to determine the mean velocity and the turbulent fluctuations of turbulent boundary layers above a distance of approximately two bubble diameters from the wall. This work broadens the current range of application of HFSB from external aerodynamics of large-scale-PIV experiments towards wall-bounded turbulence. |
| Databáze: | OpenAIRE |
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