Using Vorticity as an Indicator for the Generation of Optimal Coarse Grid Distribution |
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Authors: | Mohammad Ali Ashjari Bahar Firoozabadi Hassan Mahani |
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Affiliation: | (1) Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran;(2) Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran |
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Abstract: | An improved vorticity-based gridding technique is presented and applied to create optimal non-uniform Cartesian coarse grid for numerical simulation of two-phase flow. The optimal coarse grid distribution (OCGD) is obtained in a manner to capture variations in both permeability and fluid velocity of the fine grid using a single physical quantity called “vorticity”. Only single-phase flow simulation on the fine grid is required to extract the vorticity. Based on the fine-scale vorticity information, several coarse grid models are generated for a given fine grid model. Then the vorticity map preservation error is used to predict how well each coarse grid model reproduces the fine-scale simulation results. The coarse grid model which best preserves the fine-scale vorticity, i.e. has the minimum vorticity map preservation error is recognized as an OCGD. The performance of vorticity-based optimal coarse grid is evaluated for two highly heterogeneous 2D formations. It is also shown that two-phase flow parameters such as mobility ratio have only minor impact on the performance of the predicted OCGD. |
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Keywords: | Upscaling Vorticity Non-uniform grid Optimal coarse grid generation Porous media Two-phase flow |
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