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Slip Boundary Conditions (slip + boundary_condition)
Selected AbstractsCoupled lattice-Boltzmann and finite-difference simulation of electroosmosis in microfluidic channelsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 5 2004Dzmitry Hlushkou Abstract In this article we are concerned with an extension of the lattice-Boltzmann method for the numerical simulation of three-dimensional electroosmotic flow problems in porous media. Our description is evaluated using simple geometries as those encountered in open-channel microfluidic devices. In particular, we consider electroosmosis in straight cylindrical capillaries with a (non)uniform zeta-potential distribution for ratios of the capillary inner radius to the thickness of the electrical double layer from 10 to 100. The general case of heterogeneous zeta-potential distributions at the surface of a capillary requires solution of the following coupled equations in three dimensions: Navier,Stokes equation for liquid flow, Poisson equation for electrical potential distribution, and the Nernst,Planck equation for distribution of ionic species. The hydrodynamic problem has been treated with high efficiency by code parallelization through the lattice-Boltzmann method. For validation velocity fields were simulated in several microcapillary systems and good agreement with results predicted either theoretically or obtained by alternative numerical methods could be established. Results are also discussed with respect to the use of a slip boundary condition for the velocity field at the surface. Copyright © 2004 John Wiley & Sons, Ltd. [source] On the application of slip boundary condition on curved boundariesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2004Marek Behr Abstract Hydrodynamic simulations of sloshing phenomena often involve the application of slip boundary condition at the wetted surfaces. If these surfaces are curved, the ambiguous nature of the normal vector in the discretized problem can interfere with the application of such a boundary condition. Even the use of consistent normal vectors, preferred from the point of view of conservation, does not assure good approximation of the continuum slip condition in the discrete problem, and non-physical recirculating flow fields may be observed. As a remedy, we consider the Navier slip condition, and more successfully, the so-called BC-free boundary condition. Copyright © 2004 John Wiley & Sons, Ltd. [source] A full 3D finite element analysis of the powder injection molding filling process including slip phenomenaPOLYMER ENGINEERING & SCIENCE, Issue 1 2002C. J. Hwang A full 3D finite element analysis system has been developed to simulate a Powder Injection Molding (PIM) filling process for general three-dimensional parts. The most important features of the analysis system developed in this study are i) to incorporate the slip phenomena, the most notable rheological characteristics of PIM feedstock, into the finite element formulation based on a nonlinear penalty-like parameter and ii) to simulate the transient flow during the filling process with a predetermined finite element mesh with the help of a volume fill factor and a melt front smoothing scheme. The treatment of the nonlinear slip boundary condition was successfully validated via a steady state pipe flow. For the purpose of comparisons, not only the numerical simulations but also experimental short-shot experiments were performed with two 3D mold geometries using two typical materials of slip and no-slip cases. The good agreements between the numerical and experimental results indicate that the melt front tracking scheme successfully simulates the transient filling process. [source] On the evaluation of damping in MEMS in the slip,flow regimeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2006A. Frangi Abstract The analysis of fluid damping in micro-electro-mechanical systems (MEMS) is addressed. A mixed fast multipole boundary element method based on both velocity and traction integral equations is employed and adapted in order to account for slip boundary conditions. The formulation presented is applied to the analysis of a biaxial accelerometer and validated with experimental results. Copyright © 2006 John Wiley & Sons, Ltd. [source] Empirical slip and viscosity model performance for microscale gas flowINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2005Matthew J. McNenly Abstract For the simple geometries of Couette and Poiseuille flows, the velocity profile maintains a similar shape from continuum to free molecular flow. Therefore, modifications to the fluid viscosity and slip boundary conditions can improve the continuum based Navier,Stokes solution in the non-continuum non-equilibrium regime. In this investigation, the optimal modifications are found by a linear least-squares fit of the Navier,Stokes solution to the non-equilibrium solution obtained using the direct simulation Monte Carlo (DSMC) method. Models are then constructed for the Knudsen number dependence of the viscosity correction and the slip model from a database of DSMC solutions for Couette and Poiseuille flows of argon and nitrogen gas, with Knudsen numbers ranging from 0.01 to 10. Finally, the accuracy of the models is measured for non-equilibrium cases both in and outside the DSMC database. Flows outside the database include: combined Couette and Poiseuille flow, partial wall accommodation, helium gas, and non-zero convective acceleration. The models reproduce the velocity profiles in the DSMC database within an L2 error norm of 3% for Couette flows and 7% for Poiseuille flows. However, the errors in the model predictions outside the database are up to five times larger. Copyright © 2005 John Wiley & Sons, Ltd. [source] 2-D numerical simulation of differential viscoelastic fluids in a single-screw continuous mixer: Application of viscoelastic finite element methodsADVANCES IN POLYMER TECHNOLOGY, Issue 1 2003Robin K. Connelly Abstract Viscoelastic effects on mixing flows obtained with kneading paddles in a single-screw, continuous mixer were explored using 2-D finite element method numerical simulations. The single-mode Phan,Thien Tanner nonlinear, viscoelastic fluid model was used with parameters for a dough-like material. The viscoelastic limits of the simulations were found using elastic viscous stress splitting, 4 × 4 sub-elements for stress, streamline upwind, and streamline upwind Petrov,Galerkin (SUPG). Mesh refinement and comparison between methods was also done. The single-screw mixer was modeled by taking the kneading paddle as the point of reference, fixing the mesh in time. Rigid rotation and no slip boundary conditions at the walls were used with inertia taken into account. Results include velocity, pressure, and stress profiles. The addition of viscoelasticity caused the shear and normal stresses to vary greatly from the viscous results, with a resulting loss of symmetry in the velocity and pressure profiles in the flow region. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 22,41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10038 [source] Thorough analysis of the Oseen system in 2D exterior domainsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 15 2009Konieczny Abstract We construct Lp -estimates for the inhomogeneous Oseen system studied in a two-dimensional exterior domain , with inhomogeneous slip boundary conditions. The kernel of the paper is a result for the half space ,. Analysis of this model system shows us a parabolic character of the studied problem, resulting as an appearance of the wake region behind the obstacle. Main tools are given by the Fourier analysis to obtain the maximal regularity estimates. The results imply the solvability for the Navier,Stokes system for small velocity at infinity. Copyright © 2009 John Wiley & Sons, Ltd. [source] The destabilizing effect of boundary slip on Bénard convectionMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 7 2006Mark Webber Abstract We investigate the influence of slip boundary conditions on the onset of Bénard convection in an infinite fluid layer. It is shown that the critical Rayleigh number is a decreasing function of the slip length, and therefore boundary slip is seen to have a destabilizing effect. Chebyshev-tau and compound matrix formulations for solving the eigenvalue problem are presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||