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incompressible-flow
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Numerical Solution of Incompressible Turbulent Flow by Using High-Order Accurate FDLBM and Applying LES
, M.Sc. Thesis Sharif University of Technology ; Hejranfar, Kazem (Supervisor)
Abstract
In this study, a high-order finite-difference lattice Boltzmann method (FDLBM) is used to simulate the two-dimensional incompressible flows. Here, the incompressible form of the lattice Boltzmann (LB) equation in the two-dimensional generalized curvilinear coordinates is considered and the resulting equation is discretized based on both the third- and fifth-order upwind finite-difference schemes. The time integration of the present flow solver is performed by the fourth-order Runge-Kutta method. Several incompressible laminar flow problems are simulated to examine the accuracy and performance of the developed high-order FDLBM solver. The present results are compared with the existing...
Electrokinetic mixing and displacement of charged droplets in hydrogels
, Article Transport in Porous Media ; Vol. 104, Issue. 3 , Jun , 2014 , pp. 469-499 ; ISSN: 01693913 ; Sharif University of Technology
Abstract
Mixing in droplets is an essential task in a variety of microfluidic systems. Inspired by electrokinetic mixing, electric field-induced hydrodynamic flow inside a charged droplet embedded in an unbounded polyelectrolyte hydrogel is investigated theoretically. In this study, the polyelectrolyte hydrogel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which is located at the plane of shear, with the electrostatic potential ζ. The fluid inside the droplet attains a finite velocity owing to hydrodynamic coupling with the...
Solving combined natural convection-radiation in participating media considering the compressibility effects
, Article 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014 ; 13- 17 January , 2014 ; ISBN: 9781624102561 ; Abrar, B ; Schneider, G. E ; Sharif University of Technology
Abstract
In this work, we aim to study the effect of temperature gradients on the combined natural convection-radiation heat transfer problem in participating media. To impose this combined effect, we first solve the radiative transfer equation in an absorbing and emitting media. Then, we suitably add the radiation source terms to the energy equation and solve the fluid flow equations. Literature shows that many incompressible algorithms use the Boussinesq assumption to model the thermobuoyant force; however, the validity of this assumption is limited to cases with low temperature gradient distributions. Evidently, Boussinesq assumption would result in considerable errors in high temperature gradient...
A modified SPH method for simulating motion of rigid bodies in Newtonian fluid flows
, Article International Journal of Non-Linear Mechanics ; Volume 47, Issue 6 , 2012 , Pages 626-638 ; 00207462 (ISSN) ; Fatehi, R ; Manzari, M. T ; Sharif University of Technology
2012
Abstract
A weakly compressible smoothed particle hydrodynamics (WCSPH) method is used along with a new no-slip boundary condition to simulate movement of rigid bodies in incompressible Newtonian fluid flows. It is shown that the new boundary treatment method helps to efficiently calculate the hydrodynamic interaction forces acting on moving bodies. To compensate the effect of truncated compact support near solid boundaries, the method needs specific consistent renormalized schemes for the first and second-order spatial derivatives. In order to resolve the problem of spurious pressure oscillations in the WCSPH method, a modification to the continuity equation is used which improves the stability of...
Simulation of turbulent swirling flow in convergent nozzles
, Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 258-265 ; 10263098 (ISSN) ; Kebriaee, A ; Sharif University of Technology
Abstract
This work simulates the turbulent boundary layer of an incompressible viscous swirling flow through a conical chamber. To model the pressure gradient normal to the wall, the radial and tangential velocity components across the boundary layer have been calculated by both the integral and numerical methods. The numerical solution is accomplished by finite difference, based on the finite volume method. The results show that the radial and tangential boundary layer thicknesses depend on the velocity ratios, Reynolds number and nozzle angle. The peak of radial and tangential boundary layer thicknesses are located at zL≈0.2 and zL≈0.8 from the nozzle inlet, respectively. Due to the short length of...
A consistent and fast weakly compressible smoothed particle hydrodynamics with a new wall boundary condition
, Article International Journal for Numerical Methods in Fluids ; Volume 68, Issue 7 , May , 2012 , Pages 905-921 ; 02712091 (ISSN) ; Manzari, M. T ; Sharif University of Technology
2012
Abstract
A modified weakly compressible smoothed particle hydrodynamics (WCSPH) is presented, which utilizes consistent discretization schemes for spatial derivatives in the flow equations. Here, each SPH particle is considered as a computational point that represents a specific part of the fluid. To overcome non-physical oscillations that usually arise in standard WCSPH, we modified the mass conservation equation by using a numerical filter. This modification is based on the difference between two discretization schemes used for the term ∇{dot operator}∇Pρ. Furthermore, a new implementation of wall boundary condition in SPH is introduced. This condition is imposed on the pressure of wall boundary...
A remedy for numerical oscillations in weakly compressible smoothed particle hydrodynamics
, Article International Journal for Numerical Methods in Fluids ; Volume 67, Issue 9 , September , 2011 , Pages 1100-1114 ; 02712091 (ISSN) ; Manzari, M. T ; Sharif University of Technology
2011
Abstract
Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) can lead to non-physical oscillations in the pressure and density fields when simulating incompressible flow problems. This in turn may result in tensile instability and sometimes divergence. In this paper, it is shown that this difficulty originates from the specific form of spatial discretization used for the pressure term when solving the mass conservation equation. After describing the pressure-velocity decoupling problem associated with the so-called colocated grid methods, a modified approach is presented that overcomes this problem using a different discretization scheme for the second derivative of pressure. The modified...
Study of subsonic-supersonic gas flow through micro/nanoscale nozzles using unstructured DSMC solver
, Article Microfluidics and Nanofluidics ; Volume 10, Issue 2 , February , 2011 , Pages 321-335 ; 16134982 (ISSN) ; Roohi, E ; Sharif University of Technology
2011
Abstract
We use an extended direct simulation Monte Carlo (DSMC) method, applicable to unstructured meshes, to numerically simulate a wide range of rarefaction regimes from subsonic to supersonic flows through micro/nanoscale converging-diverging nozzles. Our unstructured DSMC method considers a uniform distribution of particles, employs proper subcell geometry, and follows an appropriate particle tracking algorithm. Using the unstructured DSMC, we study the effects of back pressure, gas/surface interactions (diffuse/specular reflections), and Knudsen number on the flow field in micro/nanoscale nozzles. If we apply the back pressure at the nozzle outlet, a boundary layer separation occurs before the...
Evaluation of a pressure splitting formulation for Weakly Compressible SPH: Fluid flow around periodic array of cylinders
, Article Computers and Mathematics with Applications ; 2016 ; 08981221 (ISSN) ; Manzari, M. T ; Fatehi, R ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this paper, a pressure splitting formulation is proposed for Weakly Compressible SPH (WC-SPH) method and its capability in the suppression of the spurious oscillations is studied by conducting a stability analysis. The proposed formulation is implemented within the framework of a consistent SPH method. The predictions from the theoretical analysis are verified by the results of numerical test-cases. This method is applied to the incompressible fluid flow around periodic array of circular cylinders. The accuracy and the convergence of the results are investigated for benchmark problems. The results are also compared with those of the conventional WC-SPH method. In a similar test-case, the...
Chebyshev collocation spectral lattice Boltzmann method for simulation of low-speed flows
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 91, Issue 1 , January , 2015 ; 15393755 (ISSN) ; Hajihassanpour, M ; Sharif University of Technology
American Physical Society
2015
Abstract
In this study, the Chebyshev collocation spectral lattice Boltzmann method (CCSLBM) is developed and assessed for the computation of low-speed flows. Both steady and unsteady flows are considered here. The discrete Boltzmann equation with the Bhatnagar-Gross-Krook approximation based on the pressure distribution function is considered and the space discretization is performed by the Chebyshev collocation spectral method to achieve a highly accurate flow solver. To provide accurate unsteady solutions, the time integration of the temporal term in the lattice Boltzmann equation is made by the fourth-order Runge-Kutta scheme. To achieve numerical stability and accuracy, physical boundary...
Developing a unified FVE-ALE approach to solve unsteady fluid flow with moving boundaries
, Article International Journal for Numerical Methods in Fluids ; Volume 63, Issue 1 , 2010 , Pages 40-68 ; 02712091 (ISSN) ; Darbandi, M ; Taeibi Rahni, M ; Sharif University of Technology
Abstract
In this study, an arbitrary Lagrangian-Eulerian (ALE) approach is incorporated with a mixed finite-volume-element (FVE) method to establish a novel moving boundary method for simulating unsteady incompressible flow on non-stationary meshes. The method collects the advantages of both finite-volume and finite-element (FE) methods as well as the ALE approach in a unified algorithm. In this regard, the convection terms are treated at the cell faces using a physical-influence upwinding scheme, while the diffusion terms are treated using bilinear FE shape functions. On the other hand, the performance of ALE approach is improved by using the Laplace method to improve the hybrid grids, involving...
Numerical investigation of thermo fluid mechanics of differentially heated rotating tubes
, Article Heat Transfer Engineering ; Volume 31, Issue 3 , 2010 , Pages 201-211 ; 01457632 (ISSN) ; Farhanieh, B ; Sharif University of Technology
2010
Abstract
Three-dimensional simulation of incompressible flow in rotating tubes for both laminar and turbulent flows has been performed using a finite-volume method for elliptic flows. The influence of Reynolds number on the velocity field and the effects of temperature gradient on temperature profiles have been presented by numerical simulations. Also the effects of velocity field, flow regime, and temperature distribution along the tube have been studied from different points of view. The results have been calculated for rotational Reynolds numbers ranging from 1000 to 320,000. The comparisons between numerically calculated velocity field and the Nusselt number have shown satisfactory agreement with...
Hyperelastic materials modelling using a strain measure consistent with the strain energy postulates
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 3 , 2010 , Pages 591-602 ; 09544062 (ISSN) ; Naghdabadi, R ; Kargarnovin, M. H ; Sharif University of Technology
Abstract
In this article, a strain energy density function of the Saint Venant-Kirchhoff type is expressed in terms of a Lagrangian deformation measure. Applying the governing postulates to the form of the strain energy density, the mathematical expression of this measure is determined. It is observed that this measure, which is consistent with the strain energy postulates, is a strain type with the characteristic function more rational than that of the Seth-Hill strain measures for hyperelastic materials modelling. In addition, the material parameters are calculated using a novel procedure that is based on the correlation between the values of the strain energy density (rather than the stresses)...
Oscillatory response of charged droplets in hydrogels
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 234 , 2016 , Pages 215-235 ; 03770257 (ISSN) ; Sharif University of Technology
Elsevier
2016
Abstract
Characterization of droplet-hydrogel interfaces is of crucial importance to engineer droplet-hydrogel composites for a variety of applications. In order to develop electrokinetic diagnostic tools for probing droplet-hydrogel interfaces, the displacement of a charged droplet embedded in a polyelectrolyte hydrogel exposed to an oscillating electric field is determined theoretically. The polyelectrolyte hydrogel is modeled as an incompressible, charged, porous, and elastic solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no charges within the droplet. The droplet-hydrogel interface is modeled as a surface with the thickness of zero...
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...
Chebyshev collocation spectral lattice boltzmann method in generalized curvilinear coordinates
, Article Computers and Fluids ; Volume 146 , 2017 , Pages 154-173 ; 00457930 (ISSN) ; Hajihassanpour, M ; Sharif University of Technology
Abstract
In this work, the Chebyshev collocation spectral lattice Boltzmann method is implemented in the generalized curvilinear coordinates to provide an accurate and efficient low-speed LB-based flow solver to be capable of handling curved geometries with non-uniform grids. The low-speed form of the D2Q9 and D3Q19 lattice Boltzmann equations is transformed into the generalized curvilinear coordinates and then the spatial derivatives in the resulting equations are discretized by using the Chebyshev collocation spectral method and the temporal term is discretized with the fourth-order Runge–Kutta scheme to provide an accurate and efficient low-speed flow solver. All boundary conditions are...
High-order weighted essentially nonoscillatory finite-difference formulation of the lattice boltzmann method in generalized curvilinear coordinates
, Article Physical Review E ; Volume 95, Issue 2 , 2017 ; 24700045 (ISSN) ; Saadat, M. H ; Taheri, S ; Sharif University of Technology
Abstract
In this work, a high-order weighted essentially nonoscillatory (WENO) finite-difference lattice Boltzmann method (WENOLBM) is developed and assessed for an accurate simulation of incompressible flows. To handle curved geometries with nonuniform grids, the incompressible form of the discrete Boltzmann equation with the Bhatnagar-Gross-Krook (BGK) approximation is transformed into the generalized curvilinear coordinates and the spatial derivatives of the resulting lattice Boltzmann equation in the computational plane are solved using the fifth-order WENO scheme. The first-order implicit-explicit Runge-Kutta scheme and also the fourth-order Runge-Kutta explicit time integrating scheme are...
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...
On coarse grids simulation of compressible mixing layer flows using vorticity confinement
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 140, Issue 3 , 2018 ; 00982202 (ISSN) ; Ebrahimi, M ; Sadri, M ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2018
Abstract
In this work, the capability and performance of the vorticity confinement (VC) implemented in a high-order accurate flow solver in predicting two-dimensional (2D) compressible mixing layer flows on coarse grids are investigated. Here, the system of governing equations with incorporation of the VC in the formulation is numerically solved by the fourth-order compact finite difference scheme. To stabilize the numerical solution, a low-pass high-order filter is applied, and the nonreflective boundary conditions are used at the farfield and outflow boundaries to minimize the reflections. At first, the numerical results without applying the VC are validated by available direct numerical...
Application of a preconditioned high-order accurate artificial compressibility-based incompressible flow solver in wide range of Reynolds numbers
, Article International Journal for Numerical Methods in Fluids ; Volume 86, Issue 1 , 2018 , Pages 46-77 ; 02712091 (ISSN) ; Parseh, K ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
In the present study, the preconditioned incompressible Navier-Stokes equations with the artificial compressibility method formulated in the generalized curvilinear coordinates are numerically solved by using a high-order compact finite-difference scheme for accurately and efficiently computing the incompressible flows in a wide range of Reynolds numbers. A fourth-order compact finite-difference scheme is utilized to accurately discretize the spatial derivative terms of the governing equations, and the time integration is carried out based on the dual time-stepping method. The capability of the proposed solution methodology for the computations of the steady and unsteady incompressible...