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Vorticity-Bases Adaptive Mesh Refinement for Upscaling of Highly Heterogeneous Porous Media

Shahriari, Arjang | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42557 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Firoozabadi, Bahar
  7. Abstract:
  8. The results of numerical simulation of underground flows are greatly affected not only by the discretization method of flow equations, but also by the way that the geological domain is upscaled. Including the detailed knowledge of heterogeneous permeability distribution is mostly neither feasible nor computationally efficient. So it is important to develop efficient grid generation and upscaling methods to simplify the fine-scale flow model while still including the impact of the heterogeneities as far as possible. Thus regions where parameters of interest have larger values or higher changes require finer grid blocks and regions with lower values or minor changes should have coarser grid blocks. In this manner the simulation time is reduced and upscaling procedure will be more accurate. Grid generations are commonly based on flow or permeability variables. More recently a gridding technique has been developed which comprises both permeability and flow characteristics using a single quantity named “vorticity” which is extracted from single-phase flow simulation. In this work vorticity is used as criterion to control the size of grid blocks. The only proposed method for vorticity-based grid generation in Cartesian Coordinates is Moving Window Method which is not appropriate enough, since in this method unnecessary regions are also refined. In the current work we have implemented more appropriate techniques to generate vorticity-based adaptively refined grids namely Cartesian Cell-Based Anisotropic Refinement Method and Wavelet Transformation Method. These new techniques therewith Moving Window Method are used to generate grids for different models. The results of 2D simulations of two-phase immiscible flows in porous media with different boundary conditions are demonstrated. To investigate the applicability and advantages of these unstructured girds, different comparisons are made with the corresponding fine grid models. In addition, comparisons between permeability-based and vorticity-based grid generations using these techniques are also presented
  9. Keywords:
  10. Mesh Generation ; Upscaling ; Wavelet Transform ; Moving Window ; Cartesian Cell-Based Anisoropic Refinement

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