Publications 34

Here we present a list of publications that were a result of projects funded by EuHIT or were published by members of EuHIT consortium.

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  • Article
    Niemela, J. J.; Skrbek, L.; Sreenivasan, K. R.; Donnelly, R. J.
    Nature. 2000, Vol. 404, Issue 6780, p. 837-840. DOI: 10.1038/35009036
    • Abstract Turbulent convection occurs when the Rayleigh number (Ra)—which quantifies the relative magnitude of thermal driving to dissipative forces in the fluid motion—becomes sufficiently high. Although many theoretical and experimental studies of turbulent convection exist, the basic properties of heat transport remain unclear. One important question concerns the existence of an asymptotic regime that is supposed to occur at very high Ra. Theory predicts that in such a state the Nusselt number (Nu), representing the global heat transport, should scale as \( \text{Nu} \propto \text{Ra}^{\beta }\) with \( \beta = 1/2 \). Here we investigate thermal transport over eleven orders of magnitude of the Rayleigh number (\( 10^{6} \leq \text{Ra} \leq 10^{17} \)), using cryogenic helium gas as the working fluid. Our data, over the entire range of Ra, can be described to the lowest order by a single power-law with scaling exponent \( \beta \) close to 0.31. In particular, we find no evidence for a transition to the \( \text{Ra}^{1/2} \) regime. We also study the variation of internal temperature fluctuations with Ra, and probe velocity statistics indirectly.
  • Article
    Redondo, J.M.; Tellez, J.D.; Sanchez, J.M.
    Trudy ISP RAN/Proc. ISP RAS. 2017, Vol. 29, Issue 2, p. 215-230. DOI: 10.15514/ISPRAS-2017-29(2)-8
    • Keywords Convection; thermoelectricity; Peltier effect; experiments; numerical simulation; K-e Model; turbulence; digiFlow
    • Abstract Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled generating a buoyant heat flux. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized using the open software tools of DigiFlow. When convective heating and cooling takes place in the side wall of a stratified enclosed cell, the combination of internal waves and buoyancy driven turbulence is much more complicated if the Rayleigh and Reynolds numbers are high. Higher order moments calculations and intermittency are important in order to study mixing in complex flows. Here some examples are shown using the Thermoelectric Convection Didactive Device (TCDD) built by BEROTZA, mainly in a symmetric two dimensional pattern, but many other combinations, using heating-cooling and angles with the vertical are possible in order to validate more complex numerical experiments.
  • Article
    Selvam, K.; Öngüner, E.; Peixinho, J.; El-Sayed, Z.; Egbers, C.
    Journal of Fluids Engineering. 2018, Vol. 140, Issue 8. DOI: 10.1115/1.4039294
  • Article
    Toffoli, A.; Proment, D.; Salman, H.; Monbaliu, J.; Frascoli, F.; Dafilis, M.; Stramignoni, E.; Forza, R.; Manfrin, M.; Onorato, M.
    Phys. Rev. Lett.. 2017, Vol. 118, Issue 14, p. 144503. DOI: 10.1103/PhysRevLett.118.144503
    • Publication URL
    • Abstract We investigate experimentally the statistical properties of a wind-generated wave field and the spontaneous formation of rogue waves in an annular flume. Unlike many experiments on rogue waves where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. What is unique about the present experiment is that the annular geometry of the tank makes waves propagating circularly in an unlimited-fetch condition. Within this peculiar framework, we discuss the temporal evolution of the statistical properties of the surface elevation. We show that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition. Our results shed new light on the formation of rogue waves in a natural environment.