J. Vierendeels | Ghent University (original) (raw)
Papers by J. Vierendeels
Computers & Chemical Engineering, 2002
For the calculation of gas Á/solid flow in circulating fluidized beds, a Eulerian Á/Eulerian appr... more For the calculation of gas Á/solid flow in circulating fluidized beds, a Eulerian Á/Eulerian approach is taken. An integration scheme based on dual time stepping and a finite volume technique is developed and implemented in 3D. The inviscid part of the equations is treated following an extension of the preconditioned advection upstream splitting method (AUSMP) to two-phase flows. Calculations on an industrial size straight riser are performed. The influence of the inelasticity of particle Á/particle collisions on the stability of the flow is investigated. Further, the effects of a double abrupt side outlet configuration are shown. #
Plasma Chemistry and Plasma Processing
The effect of calculating thermodynamic and transport properties of a gas mixture with mixing rul... more The effect of calculating thermodynamic and transport properties of a gas mixture with mixing rules on the flow field in the modeling of a thermal plasma jet was studied. A 3D large eddy simulation model of a non-transferred direct current hybrid water/argon plasma torch issuing in nitrogen atmosphere at 400 K was developed to compare three different models for the calculation of transport and thermodynamic properties of the ternary gas mixture. In the first model, thermodynamic and transport properties of the pure gases are used with mixing rules to estimate the mixture properties. In the second model, the properties of plasma gas (Ar/H2O) are calculated rigorously and mixing rules are used for estimating the properties of the mixture of plasma gas and nitrogen. In the third model, the thermodynamic and transport properties of the ternary gas mixture are calculated rigorously without any mixing rules. From numerical results, the error introduced by using mixing rules was evaluated ...
IEEE Transactions on Magnetics, 2015
Advances in Fluid Mechanics VII, 2008
A 3D Reynolds Averaged Navier, Stokes (RANS) model of a meandering channel with rectangular cross... more A 3D Reynolds Averaged Navier, Stokes (RANS) model of a meandering channel with rectangular cross-section has been developed using the commercial software package FLUENT 6.2. This model solves the 3D Navier-Stokes equations using the PISO scheme for the pressure-...
ABSTRACT Concrete pumping has become a widely applied placing technique. However, the pumping pre... more ABSTRACT Concrete pumping has become a widely applied placing technique. However, the pumping pressure estimation which is based on the rheological and tribological properties of concretes has not been well optimized. Due to its typical rheological properties, the traditional concrete flows in a pipe only by sliding on the pipe wall. This movement is governed by the local velocities developed in the slip layer which is situated at the concrete-wall interface. As a result, the slip layer thickness and rheological properties become the determining factors on the flow of the traditional concrete in the pipe. In order to study the behavior of the slip layer, a coaxial cylinders tribometer has been developed. This paper shows the influences of the eccentricity effects on the overestimation of the slip layer thickness. This overestimation results an incorrect prediction of the flow profile and the pumping pressure calculation. A modification on the working principle of the tribometer is suggested and validated by experimentations.
Computational Fluid Dynamics 2006, 2009
We propose an automatization procedure to find an optimal value of the parameter used in some rel... more We propose an automatization procedure to find an optimal value of the parameter used in some relaxation schemes. The basis of the method is formed by an aggregation-type procedure into a single aggregate and is meant to be applicable as a patch for existing codes.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2015
ABSTRACT In the context of the forthcoming next generation of Radioactive Ion Beams (RIBs) facili... more ABSTRACT In the context of the forthcoming next generation of Radioactive Ion Beams (RIBs) facilities based on an Isotope Separation On Line (ISOL) method, the development of production targets capable of dissipating the high power deposited by the primary beam is a major challenge. The concept of a high-power target based on a liquid Pb-Bi loop incorporating a heat-exchanger and a diffusion chamber was proposed within EURISOL DS and is being developed within the LIEBE1 project. Due to the non-static character of the target, specific hydrodynamics issues are of concern. In this paper, these issues are studied mostly based on three-dimensional (3D) Computational Fluid Dynamics analysis of the flow of the Lead Bismuth Eutectic (LBE) target, resulting in optimized designs. The concept and hydrodynamic challenges of generating RIBs from a liquid-metal-loop target irradiated with a high-power primary beam are presented. The optimization of the target design has been conducted keeping in mind the need for a fast and efficient release of short-lived isotopes.
ABSTRACT The behavior of concrete flowing in a pipe is a key factor for mastering the concrete pu... more ABSTRACT The behavior of concrete flowing in a pipe is a key factor for mastering the concrete pumping technique. Due to the non-homogeneity of concrete, the concentration of particles (aggregate, sand, cement…) is not the same everywhere in the pipe. Particularly in the highly sheared zone near the wall, the concentration of coarse particles is much lower than that in the bulk. As a result, the rheological properties across the cross section vary with the distance from the wall. This phenomenon affects directly the velocity profile across the section. However, the velocity profile of concrete flowing in a pipe has never been quantitatively measured. This paper shows an experimental method to accurately measure the velocity profile. On the other hand, the influence of the variation of the rheological properties on the velocity profile across the pipe is also studied. Finally, a comparison between experimental analyses and numerical simulations shows reasonable correlation. This paper concentrates on the difference between the flow of a self-compacting concrete and that of a traditional concrete based on their different rheological properties.
International Journal of Numerical Methods for Heat & Fluid Flow, 2003
A numerical scheme that has already proved to be efficient and accurate for laminar heat transfer... more A numerical scheme that has already proved to be efficient and accurate for laminar heat transfer is extended for turbulent, axisymmetric heat transfer calculations. The extended scheme is applied to the steady-state heat transfer of axisymmetric turbulent jets, impinging onto a flat plate. Firstly, the low-Reynolds version of the standard k-ɛ model is employed. As is well known, the classical
Lecture Notes in Physics, 1998
Discretization of viscous incompressible and viscous low Mach number flows often leads to a syste... more Discretization of viscous incompressible and viscous low Mach number flows often leads to a system of equations which is difficult to solve. This has two reasons: first, high aspect ratio grids result in a numerically-anisotropic behaviour of the diffusive and acoustic terms and second, especially in low Mach number flow, the ratio of the eigenvalues of the inviscid system may become very high. We implemented a new discretization method, using an explicit third order discretization for the convective part, a line implicit central discretization for the acoustic part and for the diffusive part. The lines are chosen in the direction of the gridpoints with shortest connection. The preconditioned semi-implicit line method is used in multistage form because of the explicit third order discretization of the convective part. Multigrid is used as acceleration technique. It is shown in the paper that the convergence is very good, independent of the grid aspect ratio and the Mach number.
14th Computational Fluid Dynamics Conference, 1999
Proceedings of 10th World Congress on Computational Mechanics, 2014
Proceedings of the Sixth International Conference on Engineering Computational Technology, 2008
ABSTRACT
Computers & Chemical Engineering, 2002
For the calculation of gas Á/solid flow in circulating fluidized beds, a Eulerian Á/Eulerian appr... more For the calculation of gas Á/solid flow in circulating fluidized beds, a Eulerian Á/Eulerian approach is taken. An integration scheme based on dual time stepping and a finite volume technique is developed and implemented in 3D. The inviscid part of the equations is treated following an extension of the preconditioned advection upstream splitting method (AUSMP) to two-phase flows. Calculations on an industrial size straight riser are performed. The influence of the inelasticity of particle Á/particle collisions on the stability of the flow is investigated. Further, the effects of a double abrupt side outlet configuration are shown. #
Plasma Chemistry and Plasma Processing
The effect of calculating thermodynamic and transport properties of a gas mixture with mixing rul... more The effect of calculating thermodynamic and transport properties of a gas mixture with mixing rules on the flow field in the modeling of a thermal plasma jet was studied. A 3D large eddy simulation model of a non-transferred direct current hybrid water/argon plasma torch issuing in nitrogen atmosphere at 400 K was developed to compare three different models for the calculation of transport and thermodynamic properties of the ternary gas mixture. In the first model, thermodynamic and transport properties of the pure gases are used with mixing rules to estimate the mixture properties. In the second model, the properties of plasma gas (Ar/H2O) are calculated rigorously and mixing rules are used for estimating the properties of the mixture of plasma gas and nitrogen. In the third model, the thermodynamic and transport properties of the ternary gas mixture are calculated rigorously without any mixing rules. From numerical results, the error introduced by using mixing rules was evaluated ...
IEEE Transactions on Magnetics, 2015
Advances in Fluid Mechanics VII, 2008
A 3D Reynolds Averaged Navier, Stokes (RANS) model of a meandering channel with rectangular cross... more A 3D Reynolds Averaged Navier, Stokes (RANS) model of a meandering channel with rectangular cross-section has been developed using the commercial software package FLUENT 6.2. This model solves the 3D Navier-Stokes equations using the PISO scheme for the pressure-...
ABSTRACT Concrete pumping has become a widely applied placing technique. However, the pumping pre... more ABSTRACT Concrete pumping has become a widely applied placing technique. However, the pumping pressure estimation which is based on the rheological and tribological properties of concretes has not been well optimized. Due to its typical rheological properties, the traditional concrete flows in a pipe only by sliding on the pipe wall. This movement is governed by the local velocities developed in the slip layer which is situated at the concrete-wall interface. As a result, the slip layer thickness and rheological properties become the determining factors on the flow of the traditional concrete in the pipe. In order to study the behavior of the slip layer, a coaxial cylinders tribometer has been developed. This paper shows the influences of the eccentricity effects on the overestimation of the slip layer thickness. This overestimation results an incorrect prediction of the flow profile and the pumping pressure calculation. A modification on the working principle of the tribometer is suggested and validated by experimentations.
Computational Fluid Dynamics 2006, 2009
We propose an automatization procedure to find an optimal value of the parameter used in some rel... more We propose an automatization procedure to find an optimal value of the parameter used in some relaxation schemes. The basis of the method is formed by an aggregation-type procedure into a single aggregate and is meant to be applicable as a patch for existing codes.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2015
ABSTRACT In the context of the forthcoming next generation of Radioactive Ion Beams (RIBs) facili... more ABSTRACT In the context of the forthcoming next generation of Radioactive Ion Beams (RIBs) facilities based on an Isotope Separation On Line (ISOL) method, the development of production targets capable of dissipating the high power deposited by the primary beam is a major challenge. The concept of a high-power target based on a liquid Pb-Bi loop incorporating a heat-exchanger and a diffusion chamber was proposed within EURISOL DS and is being developed within the LIEBE1 project. Due to the non-static character of the target, specific hydrodynamics issues are of concern. In this paper, these issues are studied mostly based on three-dimensional (3D) Computational Fluid Dynamics analysis of the flow of the Lead Bismuth Eutectic (LBE) target, resulting in optimized designs. The concept and hydrodynamic challenges of generating RIBs from a liquid-metal-loop target irradiated with a high-power primary beam are presented. The optimization of the target design has been conducted keeping in mind the need for a fast and efficient release of short-lived isotopes.
ABSTRACT The behavior of concrete flowing in a pipe is a key factor for mastering the concrete pu... more ABSTRACT The behavior of concrete flowing in a pipe is a key factor for mastering the concrete pumping technique. Due to the non-homogeneity of concrete, the concentration of particles (aggregate, sand, cement…) is not the same everywhere in the pipe. Particularly in the highly sheared zone near the wall, the concentration of coarse particles is much lower than that in the bulk. As a result, the rheological properties across the cross section vary with the distance from the wall. This phenomenon affects directly the velocity profile across the section. However, the velocity profile of concrete flowing in a pipe has never been quantitatively measured. This paper shows an experimental method to accurately measure the velocity profile. On the other hand, the influence of the variation of the rheological properties on the velocity profile across the pipe is also studied. Finally, a comparison between experimental analyses and numerical simulations shows reasonable correlation. This paper concentrates on the difference between the flow of a self-compacting concrete and that of a traditional concrete based on their different rheological properties.
International Journal of Numerical Methods for Heat & Fluid Flow, 2003
A numerical scheme that has already proved to be efficient and accurate for laminar heat transfer... more A numerical scheme that has already proved to be efficient and accurate for laminar heat transfer is extended for turbulent, axisymmetric heat transfer calculations. The extended scheme is applied to the steady-state heat transfer of axisymmetric turbulent jets, impinging onto a flat plate. Firstly, the low-Reynolds version of the standard k-ɛ model is employed. As is well known, the classical
Lecture Notes in Physics, 1998
Discretization of viscous incompressible and viscous low Mach number flows often leads to a syste... more Discretization of viscous incompressible and viscous low Mach number flows often leads to a system of equations which is difficult to solve. This has two reasons: first, high aspect ratio grids result in a numerically-anisotropic behaviour of the diffusive and acoustic terms and second, especially in low Mach number flow, the ratio of the eigenvalues of the inviscid system may become very high. We implemented a new discretization method, using an explicit third order discretization for the convective part, a line implicit central discretization for the acoustic part and for the diffusive part. The lines are chosen in the direction of the gridpoints with shortest connection. The preconditioned semi-implicit line method is used in multistage form because of the explicit third order discretization of the convective part. Multigrid is used as acceleration technique. It is shown in the paper that the convergence is very good, independent of the grid aspect ratio and the Mach number.
14th Computational Fluid Dynamics Conference, 1999
Proceedings of 10th World Congress on Computational Mechanics, 2014
Proceedings of the Sixth International Conference on Engineering Computational Technology, 2008
ABSTRACT