Mark L. Sawley

Optimization of a Kenics static mixer for non-creeping flow conditions

Computational Fluid Dynamics (CFD) has been employed for the optimization of the mixing efficiency of a Kenics static mixer. A series of numerical simulations has been undertaken for non-creeping flow conditions to determine the optimal twist angle of the mixing elements. The mixer efficiency has been assessed by considering the computed pressure drop along the mixer and the size of the fluid structures remaining at the mixer outlet. Contrary to the results of previous investigations for creeping flows, it is shown that for the present non-creeping Bow conditions, the twist angle of 180 degrees employed in the standard Kenics design is optimal. It is demonstrated that CFD provides an invaluable tool for mixer design optimization, despite the significant computational resources necessary to undertake the present study

Parallel computation and analysis of the flow in a static mixer

The use of a high-performance parallel computer system has been investigated to compute the incompressible flow and mixing efficiency of a static mixer. The flow computation is performed using a conventional Eulerian approach, by resolving the governing flow equations on a block-structured computational mesh. To examine the mixing process, a Lagrangian approach involving particle tracking is employed. The parallelization of both the flow computation and particle tracking phases of the numerical simulation, which are performed independently, is described. It is shown that a highperformance parallel computer system provides the possibility for more detailed and accurate simulations, leading to greater insights into the flow behaviour and mixing properties

Coupled Euler/boundary-layer method for nonequilibrium, chemically reacting hypersonic flows

Reference LIN-ARTICLE-2007-013View record in Web of Science Record created on 2007-06-22, modified on 2016-08-08

En route to multi-model scheme for clinker comminution with chemical grinding aids

We present a multimodel simulation approach, targeted at understanding the behaviour of comminution and the effect of grinding aids in industrial cement mills. On the atomistic scale, we use molecular dynamics (MD) simulations with validated force field models to quantify elastic and structural properties, cleavage energies as well as the organic interactions with mineral surfaces. Simulations based on the discrete element method (DEM) are used to integrate the information gained from MD simulations into the clinker particle behaviour at larger scales. Computed impact energy distributions from DEM mill simulations can serve as a link between large scale industrial and laboratory sized mills. They also provide the required input for particle impact fragmentation models. Such a multiscale, multimodel methodology paves the way for a structured approach to the design of chemical additives aimed at improving mill performance.We present a multimodel simulation approach, targeted at understanding the behaviour of comminution and the effect of grinding aids in industrial cement mills. On the atomistic scale, we use molecular dynamics (MD) simulations with validated force field models to quantify elastic and structural properties, cleavage energies as well as the organic interactions with mineral surfaces. Simulations based on the discrete element method (DEM) are used to integrate the information gained from MD simulations into the clinker particle behaviour at larger scales. Computed impact energy distributions from DEM mill simulations can serve as a link between large scale industrial and laboratory sized mills. They also provide the required input for particle impact fragmentation models. Such a multiscale, multimodel methodology paves the way for a structured approach to the design of chemical additives aimed at improving mill performance.

Parallel multi-block computations of incompressible flows for industrial applications

Reference LIN-CONF-2007-015View record in Web of Science Record created on 2007-07-20, modified on 2016-08-08

Hypersonic flow in chemical non-equilibrium: A comparison of thin-layer Navier-Stokes and coupled Euler/boundary layer computations

Abstract A comparison of the computed flowfields for viscous hypersonic flow in chemical non-equilibrium is presented. Two different approximations of the aerothermochemistry equations have been considered: the thin-layer Navier-Stokes equations and a second-order coupling of the Euler and boundary layer equations. To avoid discrepancies arising from the choice of the physical and chemical models, the test case considered has been defined in a precise manner. In addition, close attention is paid to the appropriate flowfield properties to be compared. The detailed agreement obtained in the computed solutions for hypersonic flow over a hyperboloid provides a verification of the accuracy of the numerical methods employed.

Parallel multi-block computations of three-dimensional incompressible flows

Parallel computation has shown to provide considerable potential for the numerical simulation of complex three-dimensional flows. A number of studies have shown that CFD codes can be parallelized for efficient use on present-day parallel computer systems. However, of particular importance for industrial applications is the total time to solution, comprised not only of the resolution of the flow equations but also the pre- and post-processing phases. Results are presented of a study of the use of high-performance parallel computing to facilitate such numerical simulations. This study is being undertaken using a 256-processor Cray T3D system, within the framework of the joint Cray Research-EPFL Parallel Application Technology Program.

A comparative study of the use of the data-parallel approach for compressible flow calculations

The results are presented of an investigation into the use of the data-parallel programming approach on four different massively-parallel computers: the MasPar MP-1 and MP-2 and the Thinking Machines CM-200 and CM-5. A code to calculate inviscid compressible flow, originally written in FORTRAN 77 for a traditional vector computer, has been re-written entirely in Fortran 90 to take advantage of the compilers available on the massively-parallel computers. It is shown that the discretization of the governing equations on a regular mesh is well adapted to data parallelism. For a typical test problem of supersonic flow through a ramped duct, computational speeds have been achieved using these massively-parallel computers that are superior to those obtained using a single processor of a Cray Y-MP. In addition, this study has enabled the question of code portability between the different computers to be assessed.

Non-equilibrium hypersonic flow simulations using the second-order boundary layer equations

Abstract A coupled Euler/boundary layer method to calculate hypersonic re-entry flows in chemical non-equilibrium is described. The flow is divided into two regions, with the second-order boundary layer equations being applied in the inner (viscous) region and the Euler equations in the outer (inviscid) region. It is shown that this allows a good matching of the calculated profiles at the interface between the two regions. The inclusion of second-order effects is shown not only to modify significantly the calculated boundary layer profiles, but also to have a large influence on the computed surface coefficients.

Distributed run-time visualization and solution steering of parallel flow simulations

A run-time visualization and solution-steering tool, TPview, has been developed to overcome difficulties commonly encountered with large-scale numerical simulations on high-performance parallel computer systems. TPview provides the interface between the parallel computer system and the visualization software running on a remote workstation. During the computation cycle, data distributed across multiple processors are periodically sent via sockets to the workstation for rendering. In addition, internal parameters of the simulation code can be modified using a user-defined graphical interface, enabling remote guiding of the solution procedure. It is shown that such a run-time visualization and solution-steering tool can be implemented with minimal effort from the programmer and end user. Examples are presented of the use of TPview in conjunction with a parallel multiblock flow solver and a commercial visualization package. These examples demonstrate its ability to provide greater insights for the analysis o...