Spectra and probability distributions of thermal flux in turbulent Rayleigh-Bénard convection
The spectra of turbulent heat flux H(k) in Rayleigh-Bénard convection with and without uniform rotation are presented. The spectrum H(k) scales with wave number k as ∼k−2. The scaling exponent is almost independent of the Taylor number Ta and Prandtl number Pr for higher values of the reduced Rayleigh number r (>103). The exponent, however, depends on Ta and Pr for smaller values of r ( (Source: Physics of Fluids)
Source: Physics of Fluids - May 10, 2016 Category: Physics Authors: Hirdesh K. Pharasi, Deepesh Kumar, Krishna Kumar and Jayanta K. Bhattacharjee Source Type: research
“Immortal” liquid film formed by colliding bubble at oscillating solid substrates
This paper presents an experimental study of the behavior of an ascending air bubble (equivalent radius 0.74 mm) colliding with a solid substrate. The substrate is either motionless or oscillating with a precisely adjusted acceleration, slightly higher than gravity. It is shown that the stability of the liquid film formed between the striking bubble and the solid surface depends not only on the hydrophobic/hydrophilic properties of the solid but also on the energetic interrelations in the system. The results indicate that the rupture of the bubble and its attachment at a smooth hydrophobicsolid surface are related to the v...
Source: Physics of Fluids - May 10, 2016 Category: Physics Authors: Jan Zawala Source Type: research
Rebound of continuous droplet streams from an immiscible liquid pool
We report on the rebound of high velocity continuous water droplet streams from the surface of an immiscible oil pool. The droplets have diameters and velocities of less than 90 μm and 15 m/s, respectively, and were created at frequencies up to 60 kHz. The impact and rebound of continuous droplet streams at this scale and velocity have been largely unexplored. This regime bridges the gap between single drop and jet impacts. The impinging droplets create a divot at the surface of the oil pool that had a common characteristic shape across a wide-range of droplet and oil properties. After impact, the reflected droplets maint...
Source: Physics of Fluids - May 10, 2016 Category: Physics Authors: William J. Doak, Danielle M. Laiacona, Guy K. German and Paul R. Chiarot Source Type: research
High-frequency sound wave propagation in binary gas mixtures flowing through microchannels
The propagation of high-frequency sound waves in binary gas mixtures flowing through microchannels is investigated by using the linearized Boltzmann equation based on a Bhatnagar-Gross-Krook (BGK)-type approach and diffuse reflection boundary conditions. The results presented refer to mixtures whose constituents have comparable molecular mass (like Ne-Ar) as well as to disparate-mass gas mixtures (composed of very heavy plus very light molecules, like He-Xe). The sound wave propagation model considered in the present paper allows to analyze the precise nature of the forced-sound modes excited in different gas mixtures. (So...
Source: Physics of Fluids - May 10, 2016 Category: Physics Authors: M. Bisi and S. Lorenzani Source Type: research
Some bifurcation routes to chaos of thermocapillary convection in two-dimensional liquid layers of finite extent
As a part of the preliminary studies for the future space experiment (Zona-K) in the Russian module of the International Space Station, some bifurcation routes to chaos of thermocapillary convection in two-dimensional liquid layers filled with 10 cSt silicone oil have been numerically studied in this paper. As the laterally applied temperature difference is raised, variations in the spatial structure and temporal evolution of the thermocapillary convection and a complex sequence of transitions are observed. The results show that the finite extent of the liquid layer significantly influences the tempo-spatial evolution of t...
Source: Physics of Fluids - May 9, 2016 Category: Physics Authors: K. Li, B. Xun and W. R. Hu Source Type: research
