Molecular Dynamic Simulation of Surface Roughness Effects on Nanoscale Flows

2009 ◽  
Author(s):  
Ali Kharazmi ◽  
Reza Kamali
Keyword(s):  
Surface Roughness ◽  
Solid Wall ◽  
Intermolecular Forces ◽  
Intermolecular Potential ◽  
Roughness Effects ◽  
Time Step ◽  
Restoring Force ◽  
Rapid Sampling ◽  
Micro Channels ◽  
Fifth Order

In the present study, a molecular based scheme has been developed for simulating flows in nano- and micro-channels with roughness. In micro channel flow, there is some difference on the flow friction between roughness and cavitations which is not well studied. The presented approach is based on the molecular dynamics (namely MD) in which different ensemble has been used. For modeling the simulation the classical Newtonian particles are allowed to obey Newtonian mechanics and intermolecular forces are founded by integrating intermolecular potential. Lennard-Jones potential is used to model the interactions between particles. Particles equation of motion is integrated using fifth order Gear predictor-corrector. To ensure rapid sampling of phase space, the time step is made as large as possible. Periodic boundary condition is implemented via minimum image convention. Each atom of the solid wall is anchored at its lattice site by a harmonic restoring force and its temperature has been controlled by utilizing Nose-Hoover thermostat. The roughness is implemented on the lower channel wall. To make a comparison between the effect of roughness and cavitation, the same dimension is used for both for different aspect ratio. To allow comparison with previous results the same fluid density has been used. The effects of surface roughness and cavitation on velocity distribution of hydrophobic and hydrophilic wall undergoing Poiseuille flow are presented.

The Influence of Solid Wall-Fluid Molecular Interaction on Transport Properties of Gases in a Mini/micro Channel

2011 ◽  
Vol 354-355 ◽  
pp. 9-18
Author(s):  
Tong Liu ◽  
Min Shan Liu ◽  
Qi Wu Dong
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Transport Properties ◽  
Molecular Interaction ◽  
Solid Wall ◽  
Continuum Hypothesis ◽  
Intermolecular Forces ◽  
Integral Approach ◽  
Micro Channels ◽  
Macro Scale

The physical model and analytical method are put forward for considering the molecular interaction between solid wall and gas fluid when dealing with convective heat transfer in macro/mini/micro channels based on the boundary layer theory concept, the molecular kinetic theory of gases, structural chemistry and continuum hypothesis. The influence rule of wall-fluid intermolecular forces to the transport properties of gases located in boundary layer region is studied applying proposed models. The gas density variation distribution equation including the wall-fluid molecular interaction is derived with continuum media integral approach. The theoretical results show that the fluid diffusion is independent of the wall-fluid interaction but visosity and heat conductivity not. According to the gas molecular density distribution function and molecular dynamics, new formulae were developed for calculating viscidity coefficient and thermal conductivity with wall-fluid interacting effect for a fluid. The research results provide scientific reference for further study and exploitation on fluid flow and heat transfer of mini/micro channels. In addition, the formulae offered in this paper to compute the transport properties of gases are also suitable for fine analysis of boundary layer in macro-scale channels.

Effects of Surface Roughness on Flows Through Nano/Micro Channel Based Biomedical Devices: A Study by Lattice Boltzmann Method

2007 ◽  
Author(s):  
Mohammed S. Mayeed ◽  
Golam M. Newaz
Keyword(s):  
Surface Roughness ◽  
Boundary Conditions ◽  
Lattice Boltzmann ◽  
Rough Boundary ◽  
Biomedical Devices ◽  
Roughness Effects ◽  
Average Roughness ◽  
Flow Profiles ◽  
Micro Channels ◽  
Boltzmann Method

The objective of this research is to study the effects of surface roughness on flows through nano/micro channels with a focus on designing better biomedical devices. A two dimensional computational model for fluid flow based on Lattice Boltzmann (LB) method has been applied first to a 10 μm width channel with flat boundary conditions and the flow profiles have been found to have an excellent comparison with analytical results. Rough boundary conditions using rectangular tooth-shaped corrugations giving about 0.25 μm average roughness have then been applied to the same 10 μm channel flow. We have observed significant differences in the velocity profiles between the flows with rough and flat boundary conditions. Boundary slips have also been observed in case of flows with rough boundary conditions. Surface roughness effects have increased or the differences between the flows with rough and flat boundary conditions have increased with decreased channel widths.

Surface roughness effects on the reinforcement of cement mortars through 3D printed metallic fibers

2016 ◽  
Vol 99 ◽  
pp. 305-311 ◽  
Author(s):  
Ilenia Farina ◽  
Francesco Fabbrocino ◽  
Francesco Colangelo ◽  
Luciano Feo ◽  
Fernando Fraternali
Keyword(s):  
Surface Roughness ◽  
Roughness Effects ◽  
Cement Mortars ◽  
3D Printed ◽  
Metallic Fibers

VIBRATIONAL FREQUENCY PERTURBATIONS IN THE RAMAN SPECTRUM OF COMPRESSED GASEOUS HYDROGEN

1964 ◽  
Vol 42 (6) ◽  
pp. 1058-1069 ◽  
Author(s):  
A. D. May ◽  
G. Varghese ◽  
J. C. Stryland ◽  
H. L. Welsh
Keyword(s):  
Raman Band ◽  
Intermolecular Forces ◽  
Hydrogen Gas ◽  
High Spectral Resolution ◽  
Intermolecular Potential ◽  
Dispersion Forces ◽  
Frequency Shifts ◽  
Linear Coefficient ◽  
Relative Population ◽  
Good Agreement

The frequencies of the Q(J) lines of the fundamental Raman band of compressed hydrogen gas were measured with high spectral resolution for a series of densities from 25 to 400 Amagat units at 300 °K and 85 °K. The frequency shifts are expressed as a power series in the gas density. The linear coefficient at a given temperature has the form aJ = ai + ae(nJ/n), where ai, constant for all the Q lines, can be interpreted in terms of isotropic intermolecular forces, and ae(nJ/n), proportional to the relative population of the initial J level, arises from the inphase coupled oscillation of pairs of molecules. The temperature variation of ai is analyzed on the basis of the Lennard-Jones intermolecular potential and the molecular pair distribution function. The repulsive overlap forces and the attractive dispersion forces give, respectively, positive and negative contributions to ai, which can be characterized by the empirical parameters Krep and Katt. The values of Katt and ae are in good agreement with calculations based on the polarizability model of the dispersion forces. The relation of the results to the Raman frequency shifts in solid hydrogen is discussed.

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