10.1002/(SICI)1097-0363(19990730)30:6<743International Journal for Numerical Methods in Fluids306743-761IJNF

Geurts, Bernardus J.

Kuerten, Johannes G.M.

Toose, E.M.

Lee, T.S.

Shi, Z.D.

ScholarBank@NUS

Effects of reynolds number on physiological-type pulsatile flows in a pipe with ring-type constrictions

The boundary integral formulation of the solution to the Stokes equations is used to describe the deformation of small compound non-Newtonian axisymmetric drops suspended in a Newtonian fluid that is subjected to an axisymmetric flow field. The non-Newtonian stress is treated as a source term in the Stokes equations, which yields an extra integral over the domains containing non-Newtonian material. By transforming the integral representation for the velocity to cylindrical co-ordinates and performing the integration over the azimuthal direction analytically, the dimension of the problem can be reduced from three to two. A boundary element method for the remaining two-dimensional problem aimed at the simulation of the deformation of such axisymmetric compound non-Newtonian drops is developed. Apart from a numerical validation of the method, simulation results for a drop consisting of an Oldroyd-B fluid and a viscoelastic material are presented. Moreover, the method is extended to compound drops that are composed of a viscous inner core encapsulated by a viscoelastic material. The simulation results for these drops are verified against theoretical results from literature. Moreover, it is shown that the method can be used to identify the dominant break-up mechanism of compound drops in relation to the specific non-Newtonian character of the membrane. The boundary integral formulation of the solution to the Stokes equations is used to describe the deformation of small compound non-Newtonian axisymmetric drops suspended in a Newtonian fluid that is subjected to an axisymmetric flow field. The non-Newtonian stress is treated as a source term in the Strokes equations, which yields an extra integral over the domains containing non-Newtonian material. By transforming the integral representation for the velocity to cylindrical co-ordinates and performing the integration over the azimuthal direction analytically, the dimension of the problem can be reduced from the three to two. A boundary element method for the remaining two-dimensional problem aimed at the simulation of the deformation of such axisymmetric compound non-Newtonian drops is developed. Apart from a numerical validation of the method, simulation results for a drop consisting of an Oldroyd-B fluid and a viscoeleastic material are presented. Moreover, t method is extended to compound drops that are composed of a viscous inner core encapsulated by a viscoelastic material. The simulation results for these drops are verified against theoretical results from literature. Moreover, it is shown that the method can be used to identify the dominant break-up mechanism of compound drops in relation to the specific non-Newtonian character of the membran

Geurts, B.J.

Kuerten, J.G.M.

Pure OAI Repository

A 2D boundary element method for simulating the deformation of axisymmetric compound non-Newtonian drops

International audienceWe present a front tracking algorithm for the solution of the 2Dincompressible Navier-Stokes equations with interfaces and surfaceforces. More particularly, we focus our attention on the accuratedescription of the surface tension terms and the associated pressurejump. We consider the stationary Laplace solution for a bubble withsurface tension. A careful treatment of the pressure gradient terms atthe interface allows us to reduce the spurious currents to the machineprecision. Good results are obtained for the oscillation of a capil-lary wave compared with the linear viscous theory. A classical test ofRayleigh-Taylor instability is presented

Popinet, S.

Zaleski, S.

Archive Ouverte en Sciences de l'Information et de la Communication

A front-tracking algorithm for accurate representation of surface tension

The boundary integral formulation of the solution to the Stokes equations is used to describe the deformation of small compound non-Newtonian axisymmetric drops suspended in a Newtonian fluid that is subjected to an axisymmetric flow field. The non-Newtonian stress is treated as a source term in the Stokes equations, which yields an extra integral over the domains containing non-Newtonian material. By transforming the integral representation for the velocity to cylindrical co-ordinates and performing the integration over the azimuthal direction analytically, the dimension of the problem can be reduced from three to two. A boundary element method for the remaining two-dimensional problem aimed at the simulation of the deformation of such axisymmetric compound non-Newtonian drops is developed. Apart from a numerical validation of the method, simulation results for a drop consisting of an Oldroyd-B fluid and a viscoelastic material are presented. Moreover, the method is extended to compound drops that are composed of a viscous inner core encapsulated by a viscoelastic material. The simulation results for these drops are verified against theoretical results from literature. Moreover, it is shown that the method can be used to identify the dominant break-up mechanism of compound drops in relation to the specific non-Newtonian character of the membrane

NARCIS 

Nicholas Lavery

Cronfa at Swansea University

Iterative and multigrid methods in the finite element solution of incompressible and turbulent fluid flow

University of Twente Research Information

English

The influence of the exit boundary conditions on the vanishing first derivative of the velocity components and constant pressure on the large eddy simulation of the fully developed turbulent channel flow has been investigated for equidistant and stretched grids at the channel exit. Results show that the chosen exit boundary conditions introduce some small disturbances that are mostly damped by the grid stretching. The difference of rms values between the fully developed turbulent channel flow with periodicity conditions and the fully developed channel flow using inlet and the exit boundary conditions is less than 10% for the equidistant grids and less than 5% for the stretched grids. The chosen boundary conditions are of interest because they may be used in complex problems with back flow at the exit

Cziesla, T.

Biswas, G.

Mitra, N. K.

Publications of the IAS Fellows

Large eddy simulation in a turbulent channel flow using exit boundary conditions

Effects of reynolds number on physiological-type pulsatile flows in a pipe with ring-type constrictions

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ScholarBank@NUS

Pure OAI Repository

Pure OAI Repository

Archive Ouverte en Sciences de l'Information et de la Communication

NARCIS

Cronfa at Swansea University

University of Twente Research Information

Publications of the IAS Fellows