728 research outputs found
Lagrangian Raylaigh-Bénard convection
No full textUsing passive tracers as sensors, we obtain Lagrangian measurements of tracers position, velocity and temperature in Rayleigh-Bénard convection at Ra=10^7-10^9. We report on statistics of temperature, velocity, and heat transport (Nusselt number). We observe that the Nusselt number is characterized by a largely intermittent behavior, likely due to the interaction of temperature with turbulent velocity fluctuations
Large scale circulation in turbulent Rayleigh-Bénard convection
No full textStatistical properties of turbulent Rayleigh-Bénard convection (RBC) are investigated experimentally in a cylindrical cell of aspect ratio one. We specifically analyze the large scale circulation of RBC based on measurements of temperature fluctuations by small Ge sensors placed inside the cell. The resulting dependencies of Reynolds numbers on Rayleigh number up to 2x10^13 are compared to available theoretical and experimental results for similar geometries
Tuning Transitions in Rotating Rayleigh-Bénard Turbulence
No full textRayleigh-Bénard convection is a canonical system for the investigation of buoyancy-driven natural convection phenomena which abound in nature and technology. Under the influence of rotation and depending on the system parameters, the flow exhibits different regimes with disparate heat transfer characteristics even in the turbulent state. The present study attempts to tune the transitions between these regimes and thus control the heat transfer in practical applications. In particular, we explore the effect of addition of neutrally-buoyant thermally-conducting particles to the fluid. Following an experimental approach, we study the flow structure and heat transfer as functions of particle concentration and system parameters
Frite
No full textFrite is a non-linear 2D animation software developed as part of the MoStyle ANR project by Melvin Even, Pierre Bénard and Pascal Barla
Teaching olfaction at the time of the 'sensual turn'. The case of Pierre Bénard
No full text[EN] Teaching olfaction is changing these days as the olfaction professional world. The 'sensual turn' studied by Howes(2003) reveals the regain of interest in this badly loved sense. We focus on teaching olfaction in higher education with the case of Pierre Bénard: a perfumer, an expert in raw materials, an olfactory manager, and a teacher. This case gives an overview of an unknown field: teaching in olfaction and opens a new research field: education sciences in olfaction. We used a semi-directive interview in a clinical orientation and different exchanges in a cooperative methodology to collect new knowledge transmitted in higher education. By his way of considering olfaction, teaching, and art as a unique way to live, the singular course of Pierre Bénard seems symptomatic of this ‘sensual turn’.Cadiou, S. (2023). Teaching olfaction at the time of the 'sensual turn'. The case of Pierre Bénard. Editorial Universitat Politècnica de València. 499-506. https://doi.org/10.4995/HEAd23.2023.16021OCS49950
The heat transport in Rayleigh-Bénard convection: local scaling exponents
No full textUsing infrared thermography, the dimensionless local wall heat fluxNu(x; y) has been measured with high spatial resolution. The measurements at the heating plate of a cubic Rayleigh-Bénard cell show that the scaling exponent α in the Nu / Ra α scaling law depends on the position with respect to the surface. The results have been obtained in a small aspect ratio cell with αx = 1,αy = 0:26 and clearly show an effect of the sidewalls on the local and therefore also on the global scaling of the heat transport
Reynolds numbers near the ultimate state of turbulent Rayleigh-Bénard convection
No full textWe report on measurements of the mean-flow Reynolds number ReU and the rms fluctuation Reynolds number ReV in turbulent Rayleigh-Bénard convection as a function of the Rayleigh number Ra for 4 x 1011 < Ra < 2 1014 and Pr ' 0:8. Both can be described by the same power law with an effective exponent = 0:44, in agreement with predictions for ReU but in disagreement with predictions for ReV
Multiple transitions in rotating turbulent Rayleigh-Bénard convection
No full textSharp transitions between potentially different turbulent states are unexpected because one might think that they should be washed out by the prevailing intense fluctuations and short coherence lengths and times. Contrary to this expectation, we found a sequence of such transitions in turbulent rotating Rayleigh-Bénard convection as the rotation rate was increased. This phenomenon became most prominent at very large Rayleigh numbers up to 2 × 10^12 where the fluctuations are extremely vigorous. It was found in the heat transport as well as in the temperature gradient near the sample center. We conjecture that the transitions are between different large-scale structures which involve changes of symmetry and thus can not be gradual
Teaching olfaction at the time of the 'sensual turn'. The case of Pierre Bénard
No full textInternational audienceTeaching olfaction is changing these days as the olfaction professional world. The 'sensual turn' studied by Howes (2003) reveals the regain of interest in this badly loved sense. We focus on teaching olfaction in higher education with the case of Pierre Bénard: a perfumer, an expert in raw materials, an olfactory manager, and a teacher. This case gives an overview of an unknown field: teaching in olfaction and opens a new research field: education sciences in olfaction. We used a semi-directive interview in a clinical orientation and different exchanges in a cooperative methodology to collect new knowledge transmitted in higher education. By his way of considering olfaction, teaching, and art as a unique way to live, the singular course of Pierre Bénard seems symptomatic of this ‘sensual turn’
Analysis of turbulent Rayleigh-Bénard convection in the compound physical/scale space domain
No full textWe report the results from two distinct direct numerical simulations (DNS) of turbulent Rayleigh-Bénard convection (RBC) for Rayleigh number of 10^5 and Prandtl number of 0.7 in a laterally unbounded domain confined between two horizontal isothermal plates with no-slip and free-slip boundary conditions respectively. The central aim of the present work consists in a simultaneous description of both flows in a compound physical/scale space domain by using a generalized form of the classical Kolmogorov equation for the second-order velocity structure function. It has been found that the dynamics of the coherent structures in RBC, the so-called thermal plumes, are clearly reflected in the multi-scale energy budgets. In particular, the enlargement of thermal plumes following the impingement at the wall entails a transfer of scale-energy from small turbulent scales toward larger ones. This aspect shed light on the role of thermal plumes in turbulent RBC and could have a direct impact on future attempts to model the effects of small-scale motions in thermal convection
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