This work presents a numerical analysis of entropy generation in Γ-Shaped enclosure that was submitted to the natural convection process using a simple thermal lattice Boltzmann method (TLBM) with the Boussinesq approximation.  A 2D thermal lattice Boltzmann method with 9 velocities, D2Q9, is used to solve the thermal flow problem. The simulations are performed at a constant Prandtl number (Pr ...

We report results for the temperature profiles of turbulent Rayleigh-Bénard convection (RBC) in the interior of a cylindrical sample of aspect ratio Γ≡D/L=0.50 (D and L are the diameter and height, respectively). Both in the classical and in the ultimate state of RBC we find that the temperature varies as A×ln(z/L)+B, where z is the distance from the bottom or top plate. In the classical state,...

The central open question about Rayleigh–Bénard convection – buoyancy-driven flow in a fluid layer heated from below and cooled above is how vertical heat flux depends on the imposed temperature gradient strongly nonlinear regime where flows are typically turbulent. quantitative challenge to determine Nusselt number $Nu$ Rayleigh $Ra$ $Ra\to \infty$ limit for fluids of fixed finite Prandtl $Pr$...

OBJECTIVES To determine which variables at baseline are predictive for the development of rheumatoid arthritis (RA) from palindromic rheumatism (PR) in a Japanese population. METHODS Anti-cyclic citrullinated peptide (anti-CCP) antibodies, joint involvement pattern, genotypes of HLA-DRB1, peptidylarginine deiminase (PADI4), and protein tyrosine phosphatase (PTPN22) were examined in 28 patient...

A new upper bound on the rate of vertical heat transport is established in 3 dimensions for stress-free velocity boundary conditions on horizontally periodic plates. For large (but finite) Prandtl numbers this bound is an improvement over the ‘ultimate’ Ra scaling and in the limit of infinite Pr, agrees with the bound of Ra recently derived in that limit. keywords: Rayleigh-Bénard convection, B...

The present paper is an experimental investigation of roughness effects on nucleate pool boiling of refrigerant R113 on horizontal circular copper surfaces. The copper samples were treated by different sand paper grit sizes to achieve different surface roughness. The average surface roughness of the four samples was 0.901, 0.735, 0.65, and 0.09, respectively. The experiments were performed in t...

We studied thermal turbulence in a low Prandtl number, Pr, fluid using liquid Hg (Pr ­ 0.024). For Rayleigh numbers (106 , Ra , 108), the histogram of temperature fluctuations at the center of the cell (aspect ratio 1), and the scaling laws for the Nusselt number and the large scale flow, all showed He-like hard turbulence. However, the cascade range of the frequency spectrum of the temperature...

In this study, the effects of Prandtl number on the primary and secondary instability of the Rayleigh-Benard convection problem has been investigated using the lattice Boltzmann method. Two different cases as Pr=5.8 and 0.7 representing the fluid in liquid and gas conditions are examined. A body forces scheme of the lattice Boltzmann method was presented. Two types of boundary conditions in the...

The aim of this paper is to contribute to the understanding of and to model the processes controlling the amplitude of the wind of Rayleigh-Bénard convection. We analyze results from direct simulation of an L/H=4 aspect-ratio domain with periodic sidewalls at Ra=(10(5), 10(6), 10(7), 10(8)) and at Pr=1 by decomposing independent realizations into wind and fluctuations. It is shown that, deep in...