Begell House Inc.
International Journal for Multiscale Computational Engineering
JMC
1543-1649
7
6
2009
SPECIAL ISSUE for the Delft Center for Computational Science and Engineering Symposium, September 19, 2008, Delft, The Netherlands
vii
Kees
Vuik
Chris R.
Kleijn
Section of Transport Phenomena, Department of Chemical Engineering, Faculty of Applied Sciences Delft University of Technology and J. M. Burgerscentre for Fluid Dynamics Julianalaan, 2628 BL Delft
Elimination of Fast Modes in the Coupled Process of Chemistry and Diffusion in Turbulent Nonpremixed Flames: An Application of the REDIM Approach
487-508
Dirk J.E.M.
Roekaerts
Department Process and Energy, Delft University of Technology, Leeghwaterstraat 44, 2628 CA Delft ; Department of Multi-Scale Physics, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft
Bart
Merci
Department of Mechanics of Flow, Heat and Combustion, Ghent University, St-Pietersnieuwstraat 41, 9000 Gent; and Postdoctoral Fellow of the Fund of Scientific Research - Flanders,Belgium
Bertrand
Naud
Modeling and Numerical Simulation Group, Energy Dept., Ciemat, Avda. Complutense 22, 28040 Madrid, Spain
Ulrich
Maas
Institute for Technical Thermodynamics, Karlsruhe University (TH), Kaiserstraβe 12, 76131 Karlsruhe, Germany
A computational study has been made of bluff-body stabilized turbulent jet flames with strong turbulence-chemistry interaction (Sydney Flames HM1 and HM3). The wide range of scales in the problem is described using a combination of a standard second moment turbulence closure, a joint scalar transported probability density function (PDF) method and the Reaction-Diffusion Manifold (REDIM) technique. The latter provides a reduction of a detailed chemistry mechanism, taking into account effects of laminar diffusion. In an a priori test it is evaluated to what extent the single shot experimental data are located on the reaction-diffusion manifold. Next, computed spatial profiles of mean and variance of independent and dependent scalar variables and profiles of conditional averages and variances (conditional on mixture fraction) are compared to the experimental results. The quality of these predictions is interpreted in relation to the a priori analysis. In general, simulations using the REDIM approach for reduction of detailed C2-chemistry confirm earlier findings for micro-mixing model behavior, obtained with a skeletal C1-mechanism. Nevertheless it is concluded that the experiments show important features that are not described by the currently used REDIM.
Some Issues Related to the Use of Immersed Boundary Methods to Represent Square Obstacles
509-522
M.B.J.M.
Pourquie
Laboratory for Aero- and Hydrodynamics, Department of Mechanical Engineering, Delft University of Technology, Leeghwaterstraat 21, 2628CA Delft, The Netherlands
Wim-Paul
Breugem
Laboratory for Aero- and Hydrodynamics, Department of Mechanical Engineering, Delft University of Technology, Leeghwaterstraat 21, 2628CA Delft, The Netherlands
Bendiks Jan
Boersma
Department of mechanical engineering Delft University of Technology Leeghwaterstraat 44, 2628 CA Delft, The Netherlands
Three aspects of immersed boundary methods are studied, namely, the influence of the region inside an obstacle on the flow outside the obstacle, the possibility to calculate local surface fluxes, and the numerical stability when compared to standard body-fitted methods.
Numerical Solutions of Some Diffuse Interface Problems: The Cahn-Hilliard Equation and the Model of Thomas and Windle
523-543
F. J.
Vermolen
Delft Institute of Applied Mathematics, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands
M. Gholami
Gharasoo
Helmholz Zentrum fur Umweltforschung, Permoserstr. 15, 04318, Leipzig, Germany
Pacelli L.J.
Zitha
Helmholz Zentrum fur Umweltforschung, Permoserstr. 15, 04318, Leipzig, Germany; Delft University of Technology, Department of Geotechnology, 2628 CN Delft, The Netherlands
J.
Bruining
Department of Geotechnology, Delft University of Technolgy, Stevinweg 1, 2628 CN Delft, The Netherlands
We consider partial differential equations with a suddenly changing parameter. The equations that we study are the Cahn-Hilliard equation, for binary and multicomponent mixtures (i.e., vector Cahn-Hilliard equations), and a stress-enhanced diffusion equation. Numerical strategies to solve these equations are analyzed in terms of discretization and time integration. Results are presented and form the basis for further research. Next to the numerical analysis, we consider some analytic properties such as mass conservation and decrease of energy.
Hybrid Simulations of Two-Way Coupled Turbulent Magnetohydrodynamic Flows
545-558
Sasa
Kenjeres
Transport Phenomena Section, Department of Chemical Engineering, Faculty of Applied
Sciences, Delft University of Technology and J.M. Burgerscentrum for Fluid Mechanics,
Delft, The Netherlands
We have applied a hybrid approach that combines the transient Reynolds-averaged Navier-Stokes (T-RANS) method for velocity and hydrodynamical turbulence with a direct numerical solving (DNS) of the magnetic induction equation for two-way coupled turbulent magnetohydrodynamic (MHD) flows. An originally developed electromagnetically extended two-equations (k-) eddy-viscosity-based model was used for the hydrodynamical turbulence closure. The validation of the hybrid approach was performed by simulating the Riga-dynamo experimental setup, which is characterized by an intermediate value of the magnetic Reynolds number (Rem 20) and a very high value of the hydrodynamical Reynolds number (Re 3.5 106). Numerical simulations provided all general features of the magnetic saturation regime with the frequency and amplitude of the generated magnetic field in good agreement with available experiments.
Computational Study of Hydrodynamics of a Standard Stirred Tank Reactor and a Large-Scale Multi-Impeller Fermenter
559-576
O.
Gunyol
Delft University of Technology, Department of Multi-Scale Physics, Prins Bernhardlaan 6, 2628 BW Delft, The Netherlands
R. F.
Mudde
Delft University of Technology, Department of Multi-Scale Physics, Prins Bernhardlaan 6, 2628 BW Delft, The Netherlands
We present single-phase simulations of the fully turbulent flow in a standard stirred tank reactor and a large-scale multi-impeller fermenter, both stirred by Rushton turbines. The mean flow characteristics and the turbulence predictions were obtained by solving the Reynolds-averaged Navier-Stokes (RANS) equations using the commercial computational fluid dynamics (CFD) code, Fluent 6.3. The standard, realisable and RNG k- models, and the Reynolds stress model (RSM) were employed for the modeling of turbulence. A moving reference frame (MRF) model was used for the modeling of the moving parts. Results showed that using the standard k - model, good predictions of the impeller power number can be calculated from the integrated turbulence kinetic energy dissipation rate as long as the grid resolution is sufficient. The underprediction in the power number was only 5% unlike the earlier studies, where values up to 50% were reported. The impeller flow number calculated was also in good agreement with the experimental values reported in the literature. The predictions of the turbulence kinetic energy and the turbulence energy dissipation profiles at the impeller discharge stream revealed that, despite its simple form, the standard k - model gave the best predictions, except in the close vicinity of the blade tip, where the RSM model matched better with the experimental data.
Inverse Shallow-Water Flow Modeling Using Model Reduction
577-594
Muhammad Umer
Altaf
Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands
Arnold W.
Heemink
Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands
Martin
Verlaan
Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands
The idea presented in this paper is variational data assimilation based on model reduction using proper orthogonal decomposition. An ensemble of forward model simulations is used to determine the approximation of the covariance matrix of the model variability, and only the dominant eigenvectors of this matrix are used to define a model subspace. An approximate linear reduced model is obtained by projecting the original model onto this reduced subspace. Compared to the classical variational method, the adjoint of the tangent linear model is replaced by the adjoint of a linear reduced forward model. Thus, it does not require the implementation of the adjoint of the tangent linear model. The minimization process is carried out in reduced subspace and hence reduces the computational cost. Twin experiments using an operational storm surge prediction model in the Netherlands, the Dutch Continental Shelf Model are performed to estimate the water depth, with the findings that the approach with relatively little computational cost and without the burden of implementation of the adjoint model can be used in variational data assimilation.
INDEX to Volume 7
595-602