Modeliranje turbulentnog dvofaznog toka aero-smeše sprašenog uglja u gorioničkim kanalima sa jednostepenim turbulatorima

The subject of this work is turbulent two-phase flow through air-coal channel(s) of complex geometry. The aim of this work is numerical optimization of fluid flow and coal particle distribution in reconstructed air-coal mixture channels. The single blade turbulator has been used to increase turbulence in the vertical section of an air-coal mixture channel. Standard k-ω turbulent model has been used for modeling turbulence. Lagrangian multiphase model has been used for discrete phase (coal particles) modeling. Although better particle distribution is reached using single blade turbulators, particle concentration in the evaluation section (where plasma generators will be built in) still remains anisotropic. Because uniform coal particle distribution is of great importance for the proper work of plasma generators, other solutions for achieving this goal will be the object of the future analysis.Predmet ovog rada je turbulentno dvofazno strujanje kroz gorioničke kanale aero-smeše sprašenog uglja kompleksne geometrije. Cilj ovog rada je numerička optimizacija strujnog toka i raspodele čestica sprašenog uglja u rekonstruisanim gorioničkim kanalima. Za povećanje turbulencije, u vertikalnom delu gorioničkog kanala aero smeše ugrađen je jednostepeni turbulator. Za modeliranje turbulencije korišćen je standardni k-ω turbulentni model. Lagranžeov pristup je korišćen za modeliranje sekundarne faze (čestica sprašenog uglja). Iako je upotrebom jednostepenih turbulatora postignuta bolja raspodela čestica sprašenog uglja, koncentracija čestica u prelaznom delu (u kome će biti ugrađeni plazma generatori) ostaje neravnomerna. Kako je ravnomerna raspodela čestica sprašenog uglja od esencijalnog značaja za pravilan rad plazma generatora, druga rešenja za postizanje ravnomerne raspodele čestica će biti predmet buduće analize

Multiphase flow of immiscible fluids on unstructured moving meshes

Figure 1: Multiple fluids with different viscosity coefficients and surface tension densities splashing on the bottom of a cylindrical container. Observe that the simulation has no problem dealing with thin sheets. In this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between fluids is represented by a set of faces in the simplicial complex. This approach ensures that the underlying discretization matches the physics and avoids the additional book-keeping required in grid-based methods where multiple fluids may occupy the same cell. Our Lagrangian approach naturally leads us to adopt a finite element approach to simulation, in contrast to the finite volume approaches adopted by a majority of fluid simulation techniques that use tetrahedral meshes. We characterize fluid simulation as an optimization problem allowing for full coupling of the pressure and velocity fields and the incorporation of a second-order surface energy. We introduce a preconditioner based on the diagonal Schur complement and solve our optimization on the GPU. We provide the results of parameter studies as well as

Turbulent Two-Phase Flow Modeling of Air-Coal Mixture Channels with Single Blade Turbulators

Abstract. Subject of this work is turbulent two-phase flow through air-coal channel(s) of complex geometry. Air flow through all eight air-coal mixture channels was simulated in first stage. Velocity and pressure field were obtained as results of this simulation. One channel was selected, based on obtained results from first case. Two-phase flow was simulated in this channel. Lagrangian multiphase model was used for discrete phase (coal particles) modeling. Two-phase flow in air-coal mixture channel without turbulator was simulated next. After that, two-phase flow in air-coal mixture channels with two different turbulator heights was simulated. Turbulators were set parallel to velocity vectors at inlet. Finally turbulators were rotated for 12 deg. around x-axis in positive mathematical direction, and simulation was repeated for both turbulator heights. The aim of this work is numerical optimization of fluid flow and coal particle distribution in reconstructed air-coal mixture channels. Single blade turbulator was used to increase turbulence in vertical section of air-coal mixture channel. Standard k-ω turbulent model was used for modeling turbulence. Lagrangian multiphase model was used for modeling coal particle distribution. More uniform coal particle distribution has been achieved using single blade turbulators. Results show that there is no significant difference in coal particle distribution between all four cases in which different turbulator geometry and position was used. Upon these conclusions, technologically simplest solution, turbulator with low height, can be suggested. Although better particle distribution is reached using single blade turbulators, particle concentration in evaluation section (where plasma generators will be built in) still remained anisotropic. Because uniform coal particle distribution is of great importance for proper work of plasma generators, other solutions for achieving this goal will be object of future analysis

Multiphase flow of immiscible fluids on unstructured moving meshes

pre-printIn this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between fluids is represented by a set of faces in the simplicial complex. This approach ensures that the underlying discretization matches the physics and avoids the additional book-keeping required in grid-based methods where multiple fluids may occupy the same cell. Our Lagrangian approach naturally leads us to adopt a finite element approach to simulation, in contrast to the finite volume approaches adopted by a majority of fluid simulation techniques that use tetrahedral meshes. We characterize fluid simulation as an optimization problem allowing for full coupling of the pressure and velocity fields and the incorporation of a second-order surface energy. We introduce a preconditioner based on the diagonal Schur complement and solve our optimization on the GPU. We provide the results of parameter studies as well as a performance analysis of our method, together with suggestions for performance optimization

A simple finite volume method for adaptive viscous liquids

© Christopher Batty & Ben Houston | ACM 2011. This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in SCA '11: Proceedings of the 2011 ACM SIGGRAPH/Eurographics Symposium on Computer Animation, http://dx.doi.org/10.1145/2019406.2019421We present the first spatially adaptive Eulerian fluid animation method to support challenging viscous liquid effects such as folding, coiling, and variable viscosity. We propose a tetrahedral node-based embedded finite volume method for fluid viscosity, adapted from popular techniques for Lagrangian deformable objects. Applied in an Eulerian fashion with implicit integration, this scheme stably and efficiently supports high viscosity fluids while yielding symmetric positive definite linear systems. To integrate this scheme into standard tetrahedral mesh-based fluid simulators, which store normal velocities on faces rather than velocity vectors at nodes, we offer two methods to reconcile these representations. The first incorporates a mapping between different degrees of freedom into the viscosity solve itself. The second uses a FLIP-like approach to transfer velocity data between nodes and faces before and after the linear solve. The former offers tighter coupling by enabling the linear solver to act directly on the face velocities of the staggered mesh, while the latter provides a sparser linear system and a simpler implementation. We demonstrate the effectiveness of our approach with animations of spatially varying viscosity, realistic rotational motion, and viscous liquid buckling and coiling

Model-reduced variational fluid simulation

We present a model-reduced variational Eulerian integrator for incompressible fluids, which combines the efficiency gains of dimension reduction, the qualitative robustness of coarse spatial and temporal resolutions of geometric integrators, and the simplicity of sub-grid accurate boundary conditions on regular grids to deal with arbitrarily-shaped domains. At the core of our contributions is a functional map approach to fluid simulation for which scalar- and vector-valued eigenfunctions of the Laplacian operator can be easily used as reduced bases. Using a variational integrator in time to preserve liveliness and a simple, yet accurate embedding of the fluid domain onto a Cartesian grid, our model-reduced fluid simulator can achieve realistic animations in significantly less computational time than full-scale non-dissipative methods but without the numerical viscosity from which current reduced methods suffer. We also demonstrate the versatility of our approach by showing how it easily extends to magnetohydrodynamics and turbulence modeling in 2D, 3D and curved domains

Tetrahedral Embedded Boundary Methods for Accurate and Flexible Adaptive Fluids

This is the peer reviewed version of the following article: Batty, C., Xenos, S., & Houston, B. (2010, May). Tetrahedral embedded boundary methods for accurate and flexible adaptive fluids. In Computer Graphics Forum (Vol. 29, No. 2, pp. 695-704). Oxford, UK: Blackwell Publishing Ltd., which has been published in final form at https://doi.org/10.1111/j.1467-8659.2009.01639.x. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.When simulating fluids, tetrahedral methods provide flexibility and ease of adaptivity that Cartesian grids find difficult to match. However, this approach has so far been limited by two conflicting requirements. First, accurate simulation requires quality Delaunay meshes and the use of circumcentric pressures. Second, meshes must align with potentially complex moving surfaces and boundaries, necessitating continuous remeshing. Unfortunately, sacrificing mesh quality in favour of speed yields inaccurate velocities and simulation artifacts. We describe how to eliminate the boundary‐matching constraint by adapting recent embedded boundary techniques to tetrahedra, so that neither air nor solid boundaries need to align with mesh geometry. This enables the use of high quality, arbitrarily graded, non‐conforming Delaunay meshes, which are simpler and faster to generate. Temporal coherence can also be exploited by reusing meshes over adjacent timesteps to further reduce meshing costs. Lastly, our free surface boundary condition eliminates the spurious currents that previous methods exhibited for slow or static scenarios. We provide several examples demonstrating that our efficient tetrahedral embedded boundary method can substantially increase the flexibility and accuracy of adaptive Eulerian fluid simulation

Simulating liquids on dynamically warping grids

We introduce dynamically warping grids for adaptive liquid simulation. Our primary contributions are a strategy for dynamically deforming regular grids over the course of a simulation and a method for efficiently utilizing these deforming grids for liquid simulation. Prior work has shown that unstructured grids are very effective for adaptive fluid simulations. However, unstructured grids often lead to complicated implementations and a poor cache hit rate due to inconsistent memory access. Regular grids, on the other hand, provide a fast, fixed memory access pattern and straightforward implementation. Our method combines the advantages of both: we leverage the simplicity of regular grids while still achieving practical and controllable spatial adaptivity. We demonstrate that our method enables adaptive simulations that are fast, flexible, and robust to null-space issues. At the same time, our method is simple to implement and takes advantage of existing highly-tuned algorithms