10:40
Computational Fluid and Solid Mechanics: Computational Fluid Dynamics (Part 2)
Chair: Alf Gerisch
10:40
25 mins
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Modeling and Simulation of Bed Dynamics in Oxyfuel Fluidized Bed Boiler
Michal Beneš, Pavel Strachota, Pavel Eichler, Jakub Klinkovský, Miroslav Kolář, Jakub Solovský, Alexandr Žák
Abstract: Our team deals with CFD algorithms for the simulation of the complex processes during combustion in fluidized bed boilers. Focus is put on the promising oxyfuel technology allowing carbon dioxide capture, storage, and utilization. We work in close collaboration with the experimentalists so that simulations can be tightly tailored to the experimental setup.
This contribution focuses on modeling the hydrodynamics of the bubbling fluidized bed under conditions specific for oxyfuel combustion of biomass. We begin by briefly introducing the 3D model of the experimental facility and the available data for simulation design. Two multiphase flow models based on both continuum and discrete particle description of the solid phases (limestone and granular biomass fuel) are introduced. Features of both approaches are discussed and compared in the given context. In particular, modeling of drag force for non-spherical particles and biomass particle attrition are considered, with further discussion on particle burnout and devolatilization. The treatment of dense solid phase in both types of models is also explained.
Subsequently, the design of the custom parallel finite volume solvers based on OpenFOAM is laid out and the simulation results obtained by both models in several setups are demonstrated.
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11:05
25 mins
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Analysis of Kuramoto-Sivashinsky model of flame/smoldering front by means of curvature driven flow
Miroslav Kolar, Shunsuke Kobayashi, Yasuhide Uegata, Shigetoshi Yazaki, Michal Benes
Abstract: In this paper we summarize our results on the investigation of the Kuramoto-Sivashinsky model, which describes the motion of flame/smoldering interface. We propose the generalization of the model formulated in terms of mathematical theory of moving parametrized curves, and investigate it from numerical and analytical point of view. In the part dedicated to computational studies, we present the verification of our scheme by measurement of experimental order of convergence. In the analytical part of the paper we summarize biffurcation analysis of the model and study of rotational wave solutions.
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11:30
25 mins
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Eigenmode analysis of the incompressible Navier-Stokes equations
Fredrik Laurén, Jan Nordström
Abstract: Solvers that rapidly converge to a unique steady-state solution are important in many fluid- dynamic applications. Different numerical techniques such as local time-stepping and multigrid are often used to enhance the convergence rate. A fundamental requirement of the underlying initial-boundary value problem is that its spectrum resides in the appropriate half of the complex plane. If not, convergence acceleration techniques will most likely fail.
We will derive the spectrum for the two-dimensional incompressible Navier-Stokes equations and analyze the convergence rates of different sets of commonly used boundary conditions (see the attached file for more details).
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