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Real-time Visualization Techniques for Modelling of Combustion and Fluids

My PhD thesis, which was defended 27.4.2006 in Czech Technical university in Prague.

The field of my research was applied Computational Fluid Dynamics - particularly simulation and visualization of combustion processes, based on fast computation of air flow using effective computational schemes for Euler equations and particle systems. It resulted in creation of real-time fluid based methods for interactive modelling of combustion dynamics in industry coal boilers used in power plants.

  • The .pdf document contains the PhD thesis itself
  • The .ppt document is the presentation before the defence committee
  • The .zip package contains the PhD thesis statement, reviews of the thesis by Doc. RNDr. Andrej Ferko, PhD, Prof. Vassilis Gekas and doc. Dr. Ing. Pavel Zemčík
Keywords: Combustion, Visualization, Particle systems, Simulation, Unsteady datasets, Hardware acceleration, Education
Thesis text (14.9 MB ) | Presentation (3.2 MB ) | Reviews (3.5 MB ) | BibTeX (0.4 KB )


Nowadays, complex simulation programs are used for modelling of combustion processes in power plant boilers. They allow designers to experiment extensively with the computer models of the boilers without necessity to build their physical models. These simulation methods are widely used and several program packages (e.g. FLUENT) are available on the market. The use of these systems led to increased quality of the design and their use has been widely adopted by designers around the world. General disadvantage of these simulation programs is the complexity of simulation, which results in very time-consuming calculations. This situation does not allow quickly investigate various conditions in the boiler and the results of parameter changes during the combustion process nor study in the real-time the dynamics of the combustion process.

In the thesis, we present techniques, which together form a solution allowing real-time simulation and visualization of these processes. We propose a solution based on simplified fluid flow and combustion process computation. We use structured cell grid representation of the combustion space. We use fast fluid simulation, based on Euler equation and continuity equation. Thus, for the specified time step, we compute changes of the mass flow pressure, velocity and other characteristics inside each cell. The changes of the cell characteristic are also based on the characteristics of the nearest neighbours of the cell. The results of the flow simulation are immediately used for the other parts of the computation.

The concept of the virtual coal particles, based on the interaction of the air mass inside the cell with the coal particles, allows fast combustion simulation. It also gives possibility of easy tracking of the flow of combustibles and allows visualizing dynamics of the entire combustion process.

We also describe our concept of pre-calculated Fluid Simulator States. It is an extension for structured fluid simulators and solvers, which are used widely in computer graphics and simulation applications. It is based on storing pre-calculated Fluid Simulator States (FSS). The simulation using our extension is based on partial computation with synchronous utilization of pre-calculated Fluid Simulator States stored on disk drives. The disk space requirements are less demanding by several orders than the ones needed for saving corresponding unsteady data sets. This allows better scalability and storing and replaying results of complex tasks with large grids and/or ten thousands of particles.

We organize pre-calculated Fluid Simulator States (FSS) in hierarchical tree structures allowing incremental solving, interactive replaying and modifications of the simulated tasks. Thus, the parameters and boundary conditions of the simulation can be modified in real-time during replaying. We proposed also hierarchical tree structures with Unsteady (time-varying) Datasets, which brings interesting interactive features to applications using these datasets.

We have also designed and implemented visualization of the computed results from our fluid simulator. We use the OpenGL graphics library for fast and portable visualization of our results, including fast visualization of virtual coal particle system and high quality grid cell visualization using interpolation using bicubic splines. For that purpose, we developed hardware-accelerated visualization using the current generation of graphics accelerators. The presented method offers real-time rendering of grid-structured data. The method uses bicubic spline interpolation and uses graphics hardware ability to map numeric values to a texture. It allows us also to render isolines of the visualized data and dynamically change the visualization parameters. We have compared the visual quality of produced images with the commonly used linear interpolation visualization methods.

The implementation of the above-described techniques has been used to develop the application My Pulverized Coal Combustion, which allows real-time interaction with the boiler model – e.g. allows changing up the inlet characteristic, such as mass flow of the air and coal, velocity of the flow, positions of the inlet without need to restart the simulation. A common, low-cost hardware was used to perform all computations and visualization. Overall, the solution allows real-time, immediate interaction of the user with the model during simulation and visualization – e.g. changing coal inlets, combustible properties and other input parameters during simulation. The solution allows real-time monitoring of about 50 basic cell volumes characteristics and statistics inside the boiler, and about 10 pulverized coal particle characteristics. All these features are available immediately, without need to wait hours for complex calculations to finish. Our solution is especially suitable for education purposes in power engineering.

The concept of our fluid simulator and the other techniques are implemented in 2D. They may be used in general fluids computation and modelling, thus not only for the combustion applications. The components have been designed as independent blocks, which could reusable in other projects.

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