Energy Conservative Dissipative Particle Dynamics Simulation of Natural Convection in Liquids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Eiyad Abu-Nada
Keyword(s):  
Natural Convection ◽  
Prandtl Number ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
Dynamics Simulation ◽  
Wide Range ◽  
Convection Problem ◽  
Basic Features ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Dissipative particle dynamics with energy conservation (eDPD) was used to study natural convection in liquid domain over a wide range of Rayleigh Numbers. The problem selected for this study was the Rayleigh–Bénard convection problem. The Prandtl number used resembles water where the Prandtl number is set to Pr = 6.57. The eDPD results were compared to the finite volume solutions, and it was found that the eDPD method calculates the temperature and flow fields throughout the natural convection domains correctly. The eDPD model recovered the basic features of natural convection, such as development of plumes, development of thermal boundary layers, and development of natural convection circulation cells (rolls). The eDPD results were presented by means of temperature isotherms, streamlines, velocity contours, velocity vector plots, and temperature and velocity profiles.

scholarly journals Boundary layer structure in turbulent Rayleigh–Bénard convection

2012 ◽  
Vol 706 ◽  
pp. 5-33 ◽  
Author(s):  
Nan Shi ◽  
Mohammad S. Emran ◽  
Jörg Schumacher
Keyword(s):  
Boundary Layer ◽  
Natural Convection ◽  
Prandtl Number ◽  
Boundary Layers ◽  
Large Scale ◽  
Three Dimensional ◽  
Large Scale Circulation ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

AbstractThe structure of the boundary layers in turbulent Rayleigh–Bénard convection is studied by means of three-dimensional direct numerical simulations. We consider convection in a cylindrical cell at aspect ratio one for Rayleigh numbers of $\mathit{Ra}= 3\ensuremath{\times} 1{0}^{9} $ and $3\ensuremath{\times} 1{0}^{10} $ at fixed Prandtl number $\mathit{Pr}= 0. 7$. Similar to the experimental results in the same setup and for the same Prandtl number, the structure of the laminar boundary layers of the velocity and temperature fields is found to deviate from the prediction of Prandtl–Blasius–Pohlhausen theory. Deviations decrease when a dynamical rescaling of the data with an instantaneously defined boundary layer thickness is performed and the analysis plane is aligned with the instantaneous direction of the large-scale circulation in the closed cell. Our numerical results demonstrate that important assumptions of existing classical laminar boundary layer theories for forced and natural convection are violated, such as the strict two-dimensionality of the dynamics or the steadiness of the fluid motion. The boundary layer dynamics consists of two essential local dynamical building blocks, a plume detachment and a post-plume phase. The former is associated with larger variations of the instantaneous thickness of velocity and temperature boundary layer and a fully three-dimensional local flow. The post-plume dynamics is connected with the large-scale circulation in the cell that penetrates the boundary region from above. The mean turbulence profiles taken in localized sections of the boundary layer for each dynamical phase are also compared with solutions of perturbation expansions of the boundary layer equations of forced or natural convection towards mixed convection. Our analysis of both boundary layers shows that the near-wall dynamics combines elements of forced Blasius-type and natural convection.

Direct Numerical Simulation of a Low Prandtl Number Rayleigh–Bénard Convection in a Square Box

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Ojas Satbhai ◽  
Subhransu Roy ◽  
Sudipto Ghosh
Keyword(s):  
Nusselt Number ◽  
Steady State ◽  
Rayleigh Number ◽  
Prandtl Number ◽  
Dimensionless Temperature ◽  
Bénard Convection ◽  
Benard Convection ◽  
Wide Range ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Direct numerical simulations for low Prandtl number fluid (Pr = 0.0216) are used to study the steady-state Rayleigh–Bénard convection (RB) in a two-dimensional unit aspect ratio box. The steady-state RB convection is characterized by analyzing the time-averaged temperature-field, and flow field for a wide range of Rayleigh number (2.1 × 105 ⩽ Ra ⩽ 2.1 × 108). It is seen that the time-averaged and space-averaged Nusselt number (Nuh¯) at the hot-wall monotonically increases with the increase in Rayleigh number (Ra) and the results show a power law scaling Nuh¯∝Ra0.2593. The current Nusselt number results are compared with the results available in the literature. The complex flow is analyzed by studying the frequency power spectra of the steady-state signal of the vertical velocity at the midpoint of the box for different Ra and probability density function of dimensionless temperature at various locations along the midline of the box.

A dissipative particle dynamics simulation study on phase diagrams for the self-assembly of amphiphilic hyperbranched multiarm copolymers in various solvents

Soft Matter ◽  
2017 ◽  
Vol 13 (36) ◽  
pp. 6178-6188 ◽  
Author(s):  
Haina Tan ◽  
Chunyang Yu ◽  
Zhongyuan Lu ◽  
Yongfeng Zhou ◽  
Deyue Yan
Keyword(s):  
Phase Diagrams ◽  
Simulation Study ◽  
Self Assembly ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
The Self ◽  
Dynamics Simulation ◽  
Dynamics Simulations ◽  
First Time ◽  
Dissipative Particle Dynamics Simulation

This work discloses for the first time the self-assembly phase diagrams of amphiphilic hyperbranched multiarm copolymers in various solvents by dissipative particle dynamics simulations.

Sign in / Sign up

Export Citation Format

Share Document