Evaluation of a full-scale helium-filled soap bubble generator

Gibeau, Bradley; Gingras, Drew; Ghaemi, Sina

doi:10.1007/s00348-019-2853-8

Cited by 14 publications

(18 citation statements)

References 18 publications

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“…The test section has dimensions () and a contraction ratio of 6.3 : 1. Previous investigations have shown that the mean free stream velocity remains uniform within 1 % across the span (Johnson & Kostiuk 2000; Gibeau, Gingras & Ghaemi 2020). The side walls of the wind tunnel are acrylic for optical access, as are some sections of the upper wall.…”

Section: Methodsmentioning

confidence: 94%

Low- and mid-frequency wall-pressure sources in a turbulent boundary layer

Gibeau

Ghaemi

2021

J. Fluid Mech.

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Section: Methodsmentioning

confidence: 94%

Low- and mid-frequency wall-pressure sources in a turbulent boundary layer

Gibeau

Ghaemi

2021

J. Fluid Mech.

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“…The time response dispersion of about 40 µs was found to be independent of the regime of production. Gibeau and Ghaemi (2018) and Gibeau et al (2020) performed similar experiments and also obtained mean time responses below 10 µs for bubbles approaching neutral buoyancy; however, standard deviations as high as 180 µs were reported. The dispersion of the physical properties of HFSB tracers could therefore represent a more critical phenomenon than matching the ensemble average density of the tracers to the air density.…”

Section: Introductionmentioning

confidence: 68%

“…Re p is the particle time response typically used in the study of HFSB tracing fidelity (Scarano et al 2015;Morias et al 2016;Faleiros et al 2019;Gibeau et al 2020). Similarly to Eq.…”

Section: Simplifications To the Equation Of Particle Motionmentioning

confidence: 99%

“…Applying the procedure experimentally, a mean time response of approximately 10 µs was measured for submillimetre HFSB. The methodology was followed by many authors for the study of HFSB tracing fidelity (Morias et al 2016;Gibeau and Ghaemi 2018;Faleiros et al 2019;Gibeau et al 2020). Morias et al (2016) reported measurements of the standard deviation of HFSB time response of 40-50 µs, exceeding its mean.…”

Section: Introductionmentioning

confidence: 99%

“…1 Timeline of main contributions regarding control of HFSB generation (focused on the generation of neutrally buoyant bubbles) and quantification of their tracing fidelity. A complete overview of HFSB generation would also have to include the works of Hale et al (1969), Okuno et al (1993), Caridi et al (2016), Gibeau et al (2020), among others Additionally, a set of experiments in a large-scale aerodynamic wind tunnel is conducted to examine the tracer behaviour of HFSB at high-Reynolds-number flows, under similar conditions than the simulations. The potential of the proposed model to assess PIV measurement errors using HFSB is demonstrated via application to experimental data, from which the HFSB density is retrieved, helping to identify the source of velocity errors.…”

Section: Introductionmentioning

confidence: 99%

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The slip velocity of nearly neutrally buoyant tracers for large-scale PIV

Faleiros

Tuinstra²,

Sciacchitano

et al. 2021

Exp Fluids

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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

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Air-filled soap bubbles for volumetric velocity measurements

et al. 2021

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The use of air-filled soap bubbles for volumetric velocimetry in air flows is demonstrated experimentally. The tracers are produced by a novel system that seeds high number density soap bubble streams for particle image velocimetry applications. Particle number density considerations, spatial resolution and response time scales are discussed in light of current seeding techniques for volumetric measurements. The micro soap bubbles are employed to measure the 3D velocity field in intermediate size flow volumes of 75 − 500 cm 3 , which are difficult to measure with existing tracers such as liquid droplets or relatively large helium-filled soap bubbles, while resolving small scale flow variations. The mean volumetric concentration of approximately 50 tracers per cm 3 provides a potential for highresolution measurements. Finally, the methodology is demonstrated for velocity measurements in the wake of a sphere immersed in a turbulent boundary layer. Both the wake structures and the boundary layer statistics are characterized successfully with a reasonable spatial resolution.

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Evaluation of a full-scale helium-filled soap bubble generator

Cited by 14 publications

References 18 publications

Low- and mid-frequency wall-pressure sources in a turbulent boundary layer

Low- and mid-frequency wall-pressure sources in a turbulent boundary layer

The slip velocity of nearly neutrally buoyant tracers for large-scale PIV

Air-filled soap bubbles for volumetric velocity measurements

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