Searched for: author%3A%22van+de+Water%2C+W.%22
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van de Water, W. (author), Dam, Nico (author), Calzavarini, Enrico (author)
Molecular tagging is used to study the dispersion and deformation of patterns written in turbulent air. The writing is done by fusing O2 and N2 molecules into NO in the focus of a strong ultraviolet laser beam. By crossing several of these laser beams, patterns that have both small and large scales can be painted. The patterns are visualized...
journal article 2024
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Reijtenbagh, J. (author), Westerweel, J. (author), van de Water, W. (author)
In our experiment a vortical flow behind a traveling plate turns into turbulence. By exactly repeating this experiment 42 times with a robot, we study the statistics of this transition. In each realization the fate of the flow is followed over 1.7 s when the plate travels with a constant velocity. It suddenly turns turbulent at a scaled...
journal article 2023
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Bruno, Domenico (author), Frezzotti, Aldo (author), Jamali, S.H. (author), van de Water, W. (author)
Spectral line shape models can successfully reproduce experimental Rayleigh-Brillouin spectra, but they need knowledge about the bulk viscosity ηb. Light scattering involves GHz frequencies, but since ηb is only documented at low frequencies, ηb is usually left as a free parameter, which is determined by a fit of the model to an experimental...
journal article 2023
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van de Water, W. (author)
I comment on the recent article Grüneisen approach for universal scaling of the Brillouin shift in gases by Liang et al (2022 New J. Phys. 24 103005). While the result of this article indeed provides a parametrization of measured Rayleigh Brillouin scattering spectra, I argue that the association with the Grüneisen effect is fortuitous. The...
review 2023
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van de Water, W. (author), Dam, Nico (author), Calzavarini, Enrico (author)
We study the dispersion of tiny molecular clouds in turbulence by writing patterns in turbulent air and following their deformation in time. The writing is done by fusing O2 and N2 molecules into NO in the focus of a strong ultraviolet laser beam. By crossing several of these laser beams, patterns that have both small and large scales can be...
journal article 2022
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Eisma, H.E. (author), Westerweel, J. (author), van de Water, W. (author)
A scalar emanating from a point source in a turbulent boundary layer does not mix homogeneously, but is organized in large regions with little variation of the concentration: uniform concentration zones. We measure scalar concentration using laser-induced fluorescence and, simultaneously, the three-dimensional velocity field using tomographic...
journal article 2021
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Reijtenbagh, J. (author), Westerweel, J. (author), van de Water, W. (author)
We study the relation between large-scale structures in the concentration field with those in the velocity field in a dye-seeded turbulent jet. The scalar concentration in a plane is measured using laser-induced fluorescence. Uniform concentration zones of an advected scalar are indentified using cluster analysis. We simultaneously measure...
journal article 2021
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van den Berg, Joris (author), Bazuin, Rens (author), Jux, Constantin (author), Sciacchitano, A. (author), Westerweel, J. (author), van de Water, W. (author)
Abstract: Our quest is for the thumb and finger positions that maximize drag in front crawl swimming and thus maximize propulsion efficiency. We focus on drag in a stationary flow. Swimming is in water, but using Reynolds similarity the drag experiments are done in a wind tunnel. We measure the forces on real-life models of a forearm with...
journal article 2021
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Lau, Y.M. (author), Westerweel, J. (author), van de Water, W. (author)
We use Faraday waves to measure interfacial tension σ between two immiscible fluids, with an interest in (ultra)low values of σ. The waves are excited by vertically oscillating the container in which the fluids reside. Using linear stability theory, we map out the accessible range of interfacial tensions. The smallest value (σmin ≈ 5 × 10-4 N...
journal article 2020
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Bocanegra Evans, Humberto (author), Dam, Nico (author), Bertens, Guus (author), van de Water, W. (author)
We present a new technique to study preferential concentration of droplets in a turbulent air flow. Preferential concentration is the tendency of droplets to cluster in regions of strain, while avoiding regions of rotation. We study the properties of the droplet concentration field in zero mean flow turbulence that was created using an array...
journal article 2020
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van Houwelingen, Josje (author), Holten, Ad P.C. (author), Clercx, Herman J.H. (author), Kunnen, Rudie P.J. (author), Molenaar, Jaap (author), van de Water, W. (author)
Abstract: We discuss the application of synthetic aperture particle image velocimetry for measuring the flow around human swimmers using small bubbles as tracer. We quantify the two-dimensional projection of the velocity field in planes perpendicular to the viewing direction of an array of six cameras. With help of simulations, modelled after...
journal article 2020
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Jamali, S.H. (author), de Groen, M. (author), Moultos, O. (author), Hartkamp, Remco (author), Vlugt, T.J.H. (author), Ubachs, Wim (author), van de Water, W. (author)
Rayleigh-Brillouin light scattering spectra of CO2 at ultraviolet wavelengths are computed from molecular dynamics which depends on intermolecular potentials only. We find excellent agreement with state of the art experimental data. This agreement was reached in a minimal computational box with sides one scattering wavelength long and...
journal article 2019
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van den Berg, Joris (author), Jux, C. (author), Sciacchitano, A. (author), van de Water, W. (author), Westerweel, J. (author)
The flow field around a full-scale swimmer’s hand model with varying thumb positions is investigated by robotic volumetric PIV. The experiment is conducted in the Open Jet Facility wind tunnel at TU Delft at 15m/s. Quantitative flow field information is constructed with 3D-PTV in a 120 liter volume, encompassing the full hand and arm. The effect...
conference paper 2019
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Wang, Yuanqing (author), Ubachs, Wim (author), van de Water, W. (author)
Rayleigh-Brillouin scattering spectra of CO <sub>2</sub> were measured at pressures ranging from 0.5 to 4 bars and temperatures from 257 to 355 K using green laser light (wavelength 532 nm, scattering angle of 55.7°). These spectra were compared to two line shape models, which take the bulk viscosity as a parameter. One model applies to the...
journal article 2019
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Eisma, H.E. (author), Tam, D.S.W. (author), Westerweel, J. (author), van de Water, W. (author)
We present results on the analysis of measurements on the dispersion of a contaminant in a turbulent boundary layer. The contaminant is a fluorescent dye (Rh.-B) that was introduced in a turbulent boundary layer (푅푅푒푒# = 3050) in a water channel. The velocity field was measured by means of tomographic PIV. Simultaneously, the concentration field...
conference paper 2018
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van Houwelingen, J. (author), van de Water, W. (author), Kunnen, R.P.J. (author), van Heijst, GJF (author), Clerx, H.J.H. (author)
Understanding the power balance of a swimmer, who needs to overcome power losses to drag and to water set in motion, requires detailed insight into the hydrodynamics of the flow around the swimmer. This will be done from a hydrodynamic point of view with techniques familiar from fluid mechanics. One of our objectives is to develop a system to...
conference paper 2016
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The result of a particle-image velocimetry (PIV) measurement is a velocity field averaged over interrogation windows. This severely affects the measurement of small-scale turbulence quantities when the interrogation window size is much larger than the smallest length scale in turbulence. A direct measurement of the dissipation rate demands the...
conference paper 2015
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A cloud of droplets evolves under the influence of strong turbulence. The droplets are made from a phosphorescent fluid. From this cloud we select at t = 0 a narrow line by exciting the droplets with a UV laser, which causes them to glow for a few milliseconds. The dispersion of this line is followed in time using a fast intensified camera. A...
conference paper 2015
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