47 results found
Alpresa P, Sherwin S, Weinberg P, et al., 2018, Orbitally shaken shallow fluid layers. I. Regime classification, Physics of Fluids, Vol: 30, ISSN: 1070-6631
© 2018 Author(s). Orbital shakers are simple devices that provide mixing, aeration, and shear stress at multiple scales and high throughput. For this reason, they are extensively used in a wide range of applications from protein production to bacterial biofilms and endothelial cell experiments. This study focuses on the behaviour of orbitally shaken shallow fluid layers in cylindrical containers. In order to investigate the behaviour over a wide range of different conditions, a significant number of numerical simulations are carried out under different configuration parameters. We demonstrate that potential theory - despite the relatively low Reynolds number of the system - describes the free-surface amplitude well and the velocity field reasonably well, except when the forcing frequency is close to a natural frequency and resonance occurs. By classifying the simulations into non-breaking, breaking, and breaking with part of the bottom uncovered, it is shown that the onset of wave breaking is well described by Δh/(2R) = 0.7Γ, where Δh is the free-surface amplitude, R is the container radius, and Γ is the container aspect ratio; Δh can be well approximated using the potential theory. This result is in agreement with standard wave breaking theories although the significant inertial forcing causes wave breaking at lower amplitudes.
Alpresa P, Sherwin S, Weinberg P, et al., 2018, Orbitally shaken shallow fluid layers. II. An improved wall shear stress model, Physics of Fluids, Vol: 30, ISSN: 1070-6631
© 2018 Author(s). A new model for the analytical prediction of wall shear stress distributions at the base of orbitally shaken shallow fluid layers is developed. This model is a generalisation of the classical extended Stokes solution and will be referred to as the potential theory-Stokes model. The model is validated using a large set of numerical simulations covering a wide range of flow regimes representative of those used in laboratory experiments. It is demonstrated that the model is in much better agreement with the simulation data than the classical Stokes solution, improving the prediction in 63% of the studied cases. The central assumption of the model - which is to link the wall shear stress with the surface velocity - is shown to hold remarkably well over all regimes covered.
van Reeuwijk M, Krug D, Holzner M, 2018, Small-scale entrainment in inclined gravity currents, Environmental Fluid Mechanics, Vol: 18, Pages: 225-239, ISSN: 1567-7419
© 2017, The Author(s). We investigate the effect of buoyancy on the small-scale aspects of turbulent entrainment by performing direct numerical simulation of a gravity current and a wall jet. In both flows, we detect the turbulent/nonturbulent interface separating turbulent from irrotational ambient flow regions using a range of enstrophy iso-levels spanning many orders of magnitude. Conform to expectation, the relative enstrophy isosurface velocity v n in the viscous superlayer scales with the Kolmogorov velocity for both flow cases. We connect the integral entrainment coefficient E to the small-scale entrainment and observe excellent agreement between the two estimates throughout the viscous superlayer. The contribution of baroclinic torque to v n is negligible, and we show that the primary reason for reduced entrainment in the gravity current as compared to the wall-jet are 1) the reduction of v n relative to the integral velocity scale u T ; and 2) the reduction in the surface area of the isosurfaces.
Bozovic R, Maksimovic C, Mijic A, et al., 2017, Blue Green Solutions. A Systems Approach to Sustainable and Cost-Effective Urban Development
This guide presents an innovative framework to systematically unlock the multiple benefits of city natural infrastructure; thus producing resilient, sustainable and cost-effective solutions. The framework is applicable at a building, neighbourhood and city-scale and is suitable both for new and retrofit developments.
Craske J, Salizzoni P, van Reeuwijk M, 2017, The turbulent Prandtl number in a pure plume is 3/5, JOURNAL OF FLUID MECHANICS, Vol: 822, Pages: 774-790, ISSN: 0022-1120
Ghim M, Alpresa P, Yang S-W, et al., 2017, Visualization of three pathways for macromolecule transport across cultured endothelium and their modification by flow, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 313, Pages: H959-H973, ISSN: 0363-6135
Holzner M, van Reeuwijk M, 2017, The turbulent/nonturbulent interface in penetrative convection, JOURNAL OF TURBULENCE, Vol: 18, Pages: 260-270, ISSN: 1468-5248
Krug D, Holzner M, Marusic I, et al., 2017, Fractal scaling of the turbulence interface in gravity currents, JOURNAL OF FLUID MECHANICS, Vol: 820, ISSN: 0022-1120
Suter I, Maksimovic C, van Reeuwijk M, 2017, A neighbourhood-scale estimate for the cooling potential of green roofs, URBAN CLIMATE, Vol: 20, Pages: 33-45, ISSN: 2212-0955
Verso L, van Reeuwijk M, Gurka R, et al., 2017, Experimental study of the initial growth of a localized turbulent patch in a stably stratified fluid, INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, Vol: 66, Pages: 127-136, ISSN: 0142-727X
Verso L, van Reeuwijk M, Liberzon A, 2017, Steady state model and experiment for an oscillating grid turbulent two-layer stratified flow, PHYSICAL REVIEW FLUIDS, Vol: 2, ISSN: 2469-990X
Craske J, van Reeuwijk M, 2016, Generalised unsteady plume theory, JOURNAL OF FLUID MECHANICS, Vol: 792, Pages: 1013-1052, ISSN: 0022-1120
Schmidt L, Fouxon I, Krug D, et al., 2016, Clustering of particles in turbulence due to phoresis, PHYSICAL REVIEW E, Vol: 93, ISSN: 2470-0045
van Reeuwijk M, Salizzoni P, Hunt GR, et al., 2016, Turbulent transport and entrainment in jets and plumes: A DNS study, PHYSICAL REVIEW FLUIDS, Vol: 1, ISSN: 2469-990X
Craske J, Debugne ALR, van Reeuwijk M, 2015, Shear-flow dispersion in turbulent jets, JOURNAL OF FLUID MECHANICS, Vol: 781, Pages: 28-51, ISSN: 0022-1120
Craske J, van Reeuwijk M, 2015, Energy dispersion in turbulent jets. Part 1. Direct simulation of steady and unsteady jets, JOURNAL OF FLUID MECHANICS, Vol: 763, Pages: 500-537, ISSN: 0022-1120
Craske J, van Reeuwijk M, 2015, Energy dispersion in turbulent jets. Part 2. A robust model for unsteady jets, JOURNAL OF FLUID MECHANICS, Vol: 763, Pages: 538-566, ISSN: 0022-1120
Morel CRG, van Reeuwijk M, Graf T, 2015, Systematic investigation of non-Boussinesq effects in variable-density groundwater flow simulations, JOURNAL OF CONTAMINANT HYDROLOGY, Vol: 183, Pages: 82-98, ISSN: 0169-7722
van Reeuwijk M, Craske J, 2015, Energy-consistent entrainment relations for jets and plumes, JOURNAL OF FLUID MECHANICS, Vol: 782, Pages: 333-355, ISSN: 0022-1120
van Reeuwijk M, Hadziabdic M, 2015, Modelling high Schmidt number turbulent mass transfer, INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, Vol: 51, Pages: 42-49, ISSN: 0142-727X
van Reeuwijk M, Holzner M, 2014, The turbulence boundary of a temporal jet, JOURNAL OF FLUID MECHANICS, Vol: 739, Pages: 254-275, ISSN: 0022-1120
Craske J, van Reeuwijk M, 2013, Robust and accurate open boundary conditions for incompressible turbulent jets and plumes, COMPUTERS & FLUIDS, Vol: 86, Pages: 284-297, ISSN: 0045-7930
Jonker HJJ, van Reeuwijk M, Sullivan PP, et al., 2013, On the scaling of shear-driven entrainment: a DNS study, JOURNAL OF FLUID MECHANICS, Vol: 732, Pages: 150-165, ISSN: 0022-1120
Lari KS, van Reeuwijk M, Maksimovic C, 2013, The role of geometry in rough wall turbulent mass transfer, HEAT AND MASS TRANSFER, Vol: 49, Pages: 1191-1203, ISSN: 0947-7411
Lari KS, van Reeuwijk M, Maksimovic C, 2013, The role of geometry in rough wall turbulent mass transfer (vol 49, pg 1191, 2013), HEAT AND MASS TRANSFER, Vol: 49, Pages: 1523-1523, ISSN: 0947-7411
Jonker HJJ, Van Reeuwijk M, Sullivan PP, et al., 2012, Interfacial layers in clear and cloudy atmospheric boundary layers, 7th International Symposium on Turbulence, Heat and Mass Transfer, Publisher: International Centre for Heat and Mass Transfer
This paper reports on some recent advances in the understanding of the behaviour of atmosphericinterfacial layers. We focus on those interfaces where a turbulent layer is separated from a quiescentlayer by a relatively strong density gradient and study in particlar the entrainment rate, i.e. the rate withwhich the mixed layer penetrates into the quiescent layer by entraining fluid across the density interface.Making use of massively parallelized supercomputers, we conduct a large number of Direct NumericalSimulations (DNS) for a wide range of conditions and study the impact exerted on the entrainment rate bythe Reynolds number, the Prandtl/(Schmidt) number, and the strength of the density jump represented bythe Richardson number. We study two cases that are relevant for the atmosphere (/ocean), i.e. I] whereturbulence is generated by a surface buoyancy flux, and II] where turbulence is generated by shear (surfacemomentum flux). Of course with DNS one cannot simulate the high Reynolds numbers encountered in atmosphericcontexts, but present computer resources do allow us to faithfully simulate the classical laboratoryexperiments on these situations and even achieve Reynolds numbers more than ten times larger.
van Reeuwijk M, Lari KS, 2012, Asymptotic solutions for turbulent mass transfer at high Schmidt number, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 468, Pages: 1676-1695, ISSN: 1364-5021
van Reeuwijk M, Lari KS, 2012, Asymptotic solutions for turbulent mass transfer augmented by a first order chemical reaction, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, Vol: 55, Pages: 6485-6490, ISSN: 0017-9310
Lari KS, van Reeuwijk M, Maksimovic C, et al., 2011, Combined bulk and wall reactions in turbulent pipe flow: decay coefficients and concentration profiles, JOURNAL OF HYDROINFORMATICS, Vol: 13, Pages: 324-333, ISSN: 1464-7141
van Reeuwijk M, 2011, A mimetic mass, momentum and energy conserving discretization for the shallow water equations, COMPUTERS & FLUIDS, Vol: 46, Pages: 411-416, ISSN: 0045-7930
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