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Elsinga, G.E. (author), Ishihara, Takashi (author), Hunt, J.C.R. (author)Direct numerical simulations up to Reλ = 1445 show that the scaling exponents for the enstrophy and the dissipation rate extrema are different and depend on the Reynolds number. A similar Reynolds number dependence of the scaling exponents is observed for the moments of the dissipation rate, but not for the moments of the enstrophy. Significant...journal article 2023
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Van Hout, R. (author), Hershkovitz, A. (author), Elsinga, G.E. (author), Westerweel, J. (author)A combination of time-resolved tomographic particle image velocimetry, refractive index matching technique and machine vision algorithms was used to measure the translational and rotational motion of freely moving, nearly neutrally buoyant spheres in a fully developed turbulent boundary layer (TBL). Located in the buffer and logarithmic...journal article 2022
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Nanda, S. (author), Westerweel, J. (author), van Terwisga, T.J.C. (author), Elsinga, G.E. (author)Following their inception, vortex cavities emanating from stationary wing tips in cavitation tunnels are often observed to grow. These effects are usually attributed to the free and dissolved non-condensable gases in the liquid. However, a detailed mechanism for the cavity's growth is not known. Consequently, the repeatability of vortex...journal article 2022
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Elsinga, G.E. (author), Ishihara, T. (author), Hunt, J. C.R. (author)The Richardson-scaling law states that the mean square separation of a fluid particle pair grows according to twithin the inertial range and at intermediate times. The theories predicting this scaling regime assume that the pair separation is within the inertial range and that the dispersion is local, which means that only eddies at the scale...journal article 2022
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Fiscaletti, D. (author), Ragni, D. (author), Overmars, E.F.J. (author), Westerweel, J. (author), Elsinga, G.E. (author)The small scales of turbulence in a high-Reynolds-number jet (R e λ≈ 350) are investigated with a µPIV setup to overcome the optical limitations of conventional tomographic PIV setups. With the aim of validating the performances of tomographic long-distance µPIV, analyses are carried out involving statistical aspects of the small scales of...journal article 2022
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Characteristics of the intense vorticity structures in isotropic turbulence at high Reynolds numbersGhira, A. A. (author), Elsinga, G.E. (author), Da Silva, C. B. (author)Direct numerical simulations (DNS) of forced (statistically stationary) isotropic turbulence are used to assess the characteristics of the intense vorticity structures (IVS) or "worms"at higher Reynolds numbers than previously available. The simulations cover a range of Taylor-based Reynolds numbers in the range 90≤Reλ≤399, for a resolution...journal article 2022
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Shariff, Karim (author), Elsinga, G.E. (author)Viscous vortex layers subject to a more general uniform strain are considered. They include Townsend's steady solution for plane strain (corresponding to a parameter a = 1), in which all the strain in the plane of the layer goes toward vorticity stretching, as well as Migdal's recent steady asymmetric solution for axisymmetric strain (a = 1/2...journal article 2021
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Ujjaini Kempaiah, K. (author), Scarano, F. (author), Elsinga, G.E. (author), van Oudheusden, B.W. (author), Bermel, Leon (author)The reduction of turbulent skin-friction drag and the response of vortical structures in a zero-pressure gradient, turbulent boundary layer subjected to spanwise wall oscillation is investigated using planar and tomographic particle image velocimetry (PIV). The experiments are conducted at a momentum based Reynolds number of 1000, while the...journal article 2020
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Gül, M. (author), Elsinga, G.E. (author), Westerweel, J. (author)This paper provides an experimental investigation on the internal shear layers and the edges of the uniform momentum zones (UMZs) in a turbulent pipe flow. The time-resolved stereoscopic particle image velocimetry data are acquired in the cross-section of the pipe, and span the range of Reynolds number Reτ=340--1259. In the first part of the...journal article 2020
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Tokgoz, S. (author), Elsinga, G.E. (author), Delfos, R. (author), Westerweel, J. (author)We report on the experimental investigation of the large-scale instantaneous flow structures in turbulent Taylor–Couette flow using tomographic particle image velocimetry. The results indicate three distinct regimes for counter-rotating flow within a shear Reynolds number range of 11000<ReS<47000 . Close to only inner cylinder rotation,...journal article 2020
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Elsinga, G.E. (author), Da Silva, C. B. (author)The average patterns of the velocity and scalar fields near turbulent/non-turbulent interfaces (TNTI), obtained from direct numerical simulations (DNS) of planar turbulent jets and shear free turbulence, are assessed in the strain eigenframe. These flow patterns help to clarify many aspects of the flow dynamics, including a passive scalar,...journal article 2019
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Valori, V. (author), Elsinga, G.E. (author), Rohde, M. (author), Westerweel, J. (author), van der Hagen, T.H.J.J. (author)Abstract: The feasibility of particle image velocimetry (PIV) in a thermally convective supercritical fluid was investigated. Hereto a Rayleigh–Bénard convection flow was studied at pressure and temperature above their critical values. The working fluid chosen was trifluoromethane because of its experimentally accessible critical point. The...journal article 2019
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van Hout, R.L.H. (author), Eisma, H.E. (author), Elsinga, G.E. (author), Westerweel, J. (author)In many applications, finite-sized particles are immersed in a turbulent boundary layer (TBL) and it is of interest to study wall effects on the instantaneous shedding of turbulence structures and associated mean velocity and Reynolds stress distributions. Here, 3D flow field dynamics in the wake of a prototypical, small sphere (D+=50, 692<...journal article 2018
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Gül, M. (author), Elsinga, G.E. (author), Westerweel, J. (author)This paper describes the hysteresis in the torque for Taylor–Couette flow in the turbulent flow regime for different shear Reynolds numbers, aspect ratios and boundary conditions. The hysteresis increases with decreasing shear Reynolds number and becomes more pronounced as the aspect ratio is increased from 22 to 88. Measurements conducted in...journal article 2018
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Dash, A. (author), Elsinga, G.E. (author)While laboratory experiments, numerical simulations as well as field tests have underlined the influence of noise barriers in dispersing vehicular emissions and reducing downwind peak concentrations, these pollutants still remain in the atmosphere. Artificial pollutant sinks (for example, particle capturing or toxic gas treating devices)...journal article 2018
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Eisma, H.E. (author), Tomas, J.M. (author), Pourquie, M.J.B.M. (author), Elsinga, G.E. (author), Jonker, H.J.J. (author), Westerweel, J. (author)Simultaneous particle-image velocimetry and laser-induced fluorescence combined with large-eddy simulations are used to investigate the flow and pollutant dispersion behaviour in a rural-to-urban roughness transition. The urban roughness is characterized by an array of cubical obstacles in an aligned arrangement. A plane fence is added one...journal article 2018
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Goudar Vishwanathappa, M. (author), Elsinga, G.E. (author)The motion of tracer particles is kinematically simulated around three elementary flow patterns; a Burgers vortex, a shear-layer structure with coincident vortices and a node-saddle topology. These patterns are representative for their broader class of coherent structures in turbulence. Therefore, examining the dispersion in these elementary...journal article 2018
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- Valori, V. (author), Elsinga, G.E. (author), Rohde, M. (author), Tummers, M.J. (author), Westerweel, J. (author), van der Hagen, T.H.J.J. (author) journal article 2017
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Elsinga, G.E. (author), Ishihara, T. (author), Goudar Vishwanathappa, M. (author), da Silva, C.B. (author), Hunt, J.C.R. (author)The scaling of turbulent motions is investigated by considering the flow in the eigenframe of the local strain-rate tensor. The flow patterns in this frame of reference are evaluated using existing direct numerical simulations of homogeneous isotropic turbulence over a Reynolds number range from up to 1131, and also with reference to data for...journal article 2017
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Tomas, J.M. (author), Eisma, H.E. (author), Pourquie, M.J.B.M. (author), Elsinga, G.E. (author), Jonker, H.J.J. (author), Westerweel, J. (author)Both large-eddy simulations (LES) and water-tunnel experiments, using simultaneous stereoscopic particle image velocimetry and laser-induced fluorescence, have been used to investigate pollutant dispersion mechanisms in regions where the surface changes from rural to urban roughness. The urban roughness was characterized by an array of...journal article 2017