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Développement d'une méthode de Boltzmann sur réseau pour la simulation d'écoulements visqueux en cuves agitées
| Content Provider | Semantic Scholar |
|---|---|
| Author | Stobiac, V. |
| Copyright Year | 2013 |
| Abstract | The major feature of the viscous flow is its resistance to motion. As the viscous forces are dominant the turbulent phenomena disappear, whereby the shape of the flow is determined by the geometry of the problem, the rheology of the fluid and the presence of several phases. In order to simulate such flows, the selected numerical tool used should be capable of accurately managing the geometry, the rheology and interactions between phases. In the scope of this thesis, numerical methods are assessed in order to improve the simulation of viscous flows in stirred tanks. In the case of mixing systems, computational fluid dynamics (CFD) is a facilitating tool which may be used to supplement experimental measurements. For instance, numerical simulations allow to readily visualize the flow inside the mixer and determine characteristic mixing numbers, such as the pumping capacity. However, simulation results are useful only if the impact of the numerical parameters on the accuracy is understood. Batch mixers for highly viscous fluids are quite tricky, rendering the simulation process highly challenging. First, the geometry of the mixing system is complex and time dependent. The complex shape of the geometry is though necessary and used to compensate the impossibility of achieving adequate mixing with the turbulence. Given that close clearance impellers are used to prevent the fluid stagnation near the tank, small gaps are found between the tank and impeller. Second, the physical properties of the mixture are also complex. The modelling approach should be able to account for the interaction between the phases (solid, liquid or gas). In the case of blending, only one single liquid phase is considered, thus the difficulty is concentrated on the rheology of the fluid. In this thesis, only blending will be examined. Notwithstanding such difficulties, the simulation of viscous mixing in stirred tanks has been the subject of many articles. It can be inferred from the literature that the finite element method (FEM) and finite volume method (FVM) have been the most commonly used approaches. Despite the use of ingenious ways to treat the complexity of the geometry (change of reference frame or immersed boundary conditions), the simulation of industrial mixing flows leads to a compromise between accuracy and computation time. This can be explained by the size and complexity of the system of equations to be solved. This limitation can be rather restrictive in the case of particularly complex geometries or highly non-Newtonian behaviors. For instance, most simulations of industrial mixing process consider only one single liquid phase. Conversely, few |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://publications.polymtl.ca/1073/1/2013_VincentStobiac.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
