Experimental and numerical study on the wavy instability in a Rayleigh-Bénard-Poiseuille flow: non linear effects.

International audienceA combined experimental and numerical study of a Rayleigh-Bénard-Poiseuille air flow in a rectangular channel is presented. The aim of the present paper is to characterize a secondary instability, referred to as wavy instability and known to be a convective instability, with the objective to identify the best situation for an optimal homogenization of heat transfers in the system. A periodic mechanical excitation is introduced at channel inlet and the spatial and temporal evolution of the temperature fluctuations are analyzed, depending on the Rayleigh number, the frequency and the amplitude of the perturbation. The Reynolds number is fixed. As the saturated state is a priori the best situation to homogenize the transfers, the objective is to expand the saturation area and to generate a maximum saturation amplitude value. It is shown that the best choice is a high Rayleigh number or/and a large magnitude of perturbation associated with a specific low value of the forcing frequency

Thermal convection and emergence of isolated vortices in soap bubbles

A novel thermal convection cell consisting of half a soap bubble heated at the equator is introduced tostudy thermal convection and the movement of isolated vortices. The soap bubble, subject to stratification,develops thermal convection at its equator. A particular feature of this cell is the emergence of isolatedvortices. These vortices resemble hurricanes or cyclones and similarities between our observed structuresand these natural objects are found. This is brought forth through a study of the mean square displacementof these objects showing signs of superdiffusion

Laminar and Intermittent flow in a tilted heat pipe

WOS:000331787700001International audienceHeat transfer measurements performed by Riedinger et al. (Phys. Fluids, 25, 015117 (2013)) showed that in an inclined channel, heated from below and cooled from above with adiabatic walls, the flow is laminar or intermittent (local bursts can occur in the laminar flow) when the inclination angle is sufficiently high and the applied power sufficiently low. In this case, gravity plays a crucial role in the characteristics of the flow. In this paper, we present velocity measurements, and their derived tensors, obtained with Particle Image Velocimetry inside the channel. We, also, propose a model derived from a jet interpretation of the flow. Comparison between experiment and model shows a fair agreement

Intensity of vortices: from soap bubbles to hurricanes

By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones

Additional file 3 of Immunogenetic variation shapes the gut microbiome in a natural vertebrate population

The identity of 19 amplicon sequencing variants (ASVs) identified in the negative extraction controls. A taxonomic breakdown and the number of reads associated with each ASV is provided. ASVs were either filtered from the dataset before further analysis or retained. In the second tab is a detailed breakdown of number of reads with each ASV present in each sample, along with whether it is a negative control or faecal sample, and whether it was sequenced in the 1st, 2nd, or 3rd sequencing run