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Square Channel (square + channel)

Distribution by Scientific Domains
Chemistry50%

Selected Abstracts

Bounds on outputs of the exact weak solution of the three-dimensional Stokes problem

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2009
Zhong Cheng
Abstract A method for obtaining rigorous upper and lower bounds on an output of the exact weak solution of the three-dimensional Stokes problem is described. Recently bounds for the exact outputs of interest have been obtained for both the Poisson equation and the advection-diffusion-reaction equation. In this work, we extend this approach to the Stokes problem where a novel formulation of the method also leads to a simpler flux calculation based on the directly equilibrated flux method. To illustrate this technique, bounds on the flowrate are calculated for an incompressible creeping flow driven by a pressure gradient in an endless square channel with an array of rectangular obstacles in the center. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A 3D incompressible Navier,Stokes velocity,vorticity weak form finite element algorithm

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2002
K. L. Wong
Abstract The velocity,vorticity formulation is selected to develop a time-accurate CFD finite element algorithm for the incompressible Navier,Stokes equations in three dimensions. The finite element implementation uses equal order trilinear finite elements on a non-staggered hexahedral mesh. A second order vorticity kinematic boundary condition is derived for the no slip wall boundary condition which also enforces the incompressibility constraint. A biconjugate gradient stabilized (BiCGSTAB) sparse iterative solver is utilized to solve the fully coupled system of equations as a Newton algorithm. The solver yields an efficient parallel solution algorithm on distributed-memory machines, such as the IBM SP2. Three dimensional laminar flow solutions for a square channel, a lid-driven cavity, and a thermal cavity are established and compared with available benchmark solutions. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Viscous co-current downward Taylor flow in a square mini-channel

AICHE JOURNAL, Issue 7 2010
Özge Keskin
Abstract This article presents a computational study of the co-current downward Taylor flow of gas bubbles in a viscous liquid within a square channel of 1 mm hydraulic diameter. The three-dimensional numerical simulations are performed with an in-house computer code, which is based on the volume-of-fluid method with interface reconstruction. The computed (always axi-symmetric) bubble shapes are validated by experimental flow visualizations for varying capillary number. The evaluation of the numerical results for a series of simulations reveals the dependence of the bubble diameter and the interfacial area per unit volume on the capillary number. Correlations between bubble velocity and total superficial velocity are also provided. The present results are useful to estimate the values of the bubble diameter, the liquid film thickness and the interfacial area per unit volume from given values of the gas and liquid superficial velocities. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

A new lanthanum titanium oxy­sulfide, La16Ti5S17+xO17, with x,=,0.75,(9)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2003
Vincent Meignen
The title compound, hexadecalanthanum pentatitanium heptadeca­sulfide heptadecaoxide, La16Ti5S17+xO17 [x,= 0.75,(9)], has been obtained as a by-product in the preparation of new oxy­chalcogenide compounds in the La/Ti/Ag/S/O system. La16Ti5S17+xO17 crystallizes in the tetragonal system (space group I4/m) and is isostructural with Nd16Ti5S17O17. The structure of the title compound consists of an [La2S2] rock-salt-type framework, which delimits [001] square channels containing two types of chains of corner-sharing Ti(O,S)6 octahedra. These chains are connected through La(O,S)n polyhedra. [source]