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backward-facing-step
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DSMC simulation of subsonic flow through nanochannels and micro/nano backward-facing steps
, Article International Communications in Heat and Mass Transfer ; Volume 38, Issue 10 , 2011 , Pages 1443-1448 ; 07351933 (ISSN) ; Roohi, E ; Sharif University of Technology
2011
Abstract
In this study, we use direct simulation Monte Carlo method to simulate subsonic flow in nanochannels and micro/nanoscale backward-facing (BF) step considering a wide range of Knudsen number regimes. The nanochannel flow simulation indicates that the nanoscale flow through the nanochannel resembles unique features such as encountering negative pressure deviation behavior and observing flat velocity profiles at higher Knudsen number regimes. On the other hand, the micro/nano BF step flow simulations demonstrate that the length of separation region considerably decreases as the flow becomes more rarefied and approaches the transition regime. Meanwhile, the variations in the flow properties are...
Three-dimensional compressible-incompressible turbulent flow simulation using a pressure-based algorithm
, Article Computers and Fluids ; Volume 37, Issue 6 , 2008 , Pages 747-766 ; 00457930 (ISSN) ; Darbandi, M ; Taeibi Rahni, M ; Sharif University of Technology
2008
Abstract
In this work, we extend a finite-volume pressure-based incompressible algorithm to solve three-dimensional compressible and incompressible turbulent flow regimes. To achieve a hybrid algorithm capable of solving either compressible or incompressible flows, the mass flux components instead of the primitive velocity components are chosen as the primary dependent variables in a SIMPLE-based algorithm. This choice warrants to reduce the nonlinearities arose in treating the system of conservative equations. The use of a new Favre-averaging like technique plays a key role to render this benefit. The developed formulations indicate that there is less demand to interpolate the fluxes at the cell...
Using fully implicit conservative statements to close open boundaries passing through recirculations
, Article International Journal for Numerical Methods in Fluids ; Volume 53, Issue 3 , 2007 , Pages 371-389 ; 02712091 (ISSN) ; Vakilipour, S ; Sharif University of Technology
2007
Abstract
The numerical solution of the fluid flow governing equations requires the implementation of certain boundary conditions at suitable places to make the problem well-posed. Most of numerical strategies exhibit weak performance and obtain inaccurate solutions if the solution domain boundaries are not placed at adequate locations. Unfortunately, many practical fluid flow problems pose difficulty at their boundaries because the required information for solving the PDE's is not available there. On the other hand, large solution domains with known boundary conditions normally need a higher number of mesh nodes, which can increase the computational cost. Such difficulties have motivated the CFD...
Comparative analysis of the boundary transfer method with other near-wall treatments based on the k-ε turbulence model
, Article European Journal of Mechanics, B/Fluids ; Vol. 44, issue , 2014 , pp. 22-31 ; ISSN: 09977546 ; Basirat Tabrizi, H ; Farhadpour, F. A ; Sharif University of Technology
Abstract
Accurate description of wall-bounded turbulent flows requires a fine grid near walls to fully resolve the boundary layers. We consider a locally simplified transport model using an assumed near-wall viscosity profile to project the wall boundary conditions using the boundary transfer method. Related coefficients are obtained numerically. By choosing a near-wall viscosity profile, we derive an analytic wall function, which significantly reduces the CPU costs. The performance of this wall function is compared to other near-wall treatments proposed in the literature for two frequently used benchmark cases: near-equilibrium channel flow and flow over a backward-facing step with separation and...
High-order accurate numerical solution of incompressible slip flow and heat transfer in microchannels
, Article Lecture Notes in Computational Science and Engineering, 22 June 2009 through 26 June 2009 ; Volume 76 LNCSE , June , 2011 , Pages 419-427 ; 14397358 (ISSN); 9783642153365 (ISBN) ; Mohafez, M. H ; Khajeh Saeed, A ; Sharif University of Technology
2011
Abstract
A high-order accurate implicit operator scheme is used to solve steady incompressible slip flow and heat transfer in 2D microchannels. The present methodology considers the solution of the Navier-Stokes equations using the artificial compressibility method with employing the Maxwell and Smoluchowski boundary conditions to model the slip flow and temperature jump on the walls in microchannels. Since the slip and temperature jump boundary conditions contain the derivatives of the velocity and temperature profiles, using the compact method the boundary conditions can be easily and accurately implemented. The computations are performed for a 2D microchannel and a 2D backward facing step in the...
Investigation of obstacle effect to improve conjugate heat transfer in backward facing step channel using fast simulation of incompressible flow
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; 2017 , Pages 1-16 ; 09477411 (ISSN) ; Moazezi, A ; Sharif University of Technology
Abstract
The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In...
Investigation of obstacle effect to improve conjugate heat transfer in backward facing step channel using fast simulation of incompressible flow
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 54, Issue 1 , 2018 , Pages 135-150 ; 09477411 (ISSN) ; Moazezi, A ; Sharif University of Technology
Springer Verlag
2018
Abstract
The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In...
An implicit dual-time stepping high-order nodal discontinuous Galerkin method for solving incompressible flows on triangle elements
, Article Mathematics and Computers in Simulation ; Volume 168 , 2020 , Pages 173-214 ; Hejranfar, K ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this work, a high-order nodal discontinuous Galerkin method (NDGM) is developed and assessed for the simulation of 2D incompressible flows on triangle elements. The governing equations are the 2D incompressible Navier–Stokes equations with the artificial compressibility method. The discretization of the spatial derivatives in the resulting system of equations is made by the NDGM and the time integration is performed by applying the implicit dual-time stepping method. Three numerical fluxes, namely, the local Lax–Friedrich, Roe and AUSM+-up are formulated and applied to assess and compare their accuracy and performance in the simulation of incompressible flows using the NDGM. Several...
Implementing a high-order accurate implicit operator scheme for solving steady incompressible viscous flows using artificial compressibility method
, Article International Journal for Numerical Methods in Fluids ; Volume 66, Issue 8 , July , 2011 , Pages 939-962 ; 02712091 (ISSN) ; Khajeh Saeed, A ; Sharif University of Technology
2011
Abstract
This paper uses a fourth-order compact finite-difference scheme for solving steady incompressible flows. The high-order compact method applied is an alternating direction implicit operator scheme, which has been used by Ekaterinaris for computing two-dimensional compressible flows. Herein, this numerical scheme is efficiently implemented to solve the incompressible Navier-Stokes equations in the primitive variables formulation using the artificial compressibility method. For space discretizing the convective fluxes, fourth-order centered spatial accuracy of the implicit operators is efficiently obtained by performing compact space differentiation in which the method uses block-tridiagonal...
Numerical study of solid fuel evaporation and auto-ignition in a dump combustor
, Article Acta Astronautica ; Volume 67, Issue 7-8 , 2010 , Pages 774-783 ; 00945765 (ISSN) ; Farshchi, M ; Sharif University of Technology
2010
Abstract
Evaporation of polymeric solid fuels in backward facing step geometry subject to an inlet oxidizer flow at elevated temperatures is considered and convective heating of the fuel surface by the hot oxidizing inlet flow and subsequent mixing of the evaporated fuel with the oxidizer flow and its combustion is numerically studied. The objective of this work is to gain insight into the auto-ignition of the fuel and its controlling parameters in this configuration. The system of governing equations is solved with a finite volume approach using a structured grid in which the AUSM scheme is used to calculate the gas phase convective fluxes. The flowfield is turbulent and the SpalartAllmaras...