The relationship between capillary pressure and saturation plays a critical role in the characterization of two-phase flow and transport in aquifers and oil reservoirs. This relationship is usually determined under th...The relationship between capillary pressure and saturation plays a critical role in the characterization of two-phase flow and transport in aquifers and oil reservoirs. This relationship is usually determined under the static condition, where capillary pressure is the only function of saturation. However,considerable experiments have suggested that the dependence of capillary pressure on desaturation rate is under the dynamic condition. Thus, a more general description of capillary pressure that includes dynamic capillary effect has been approved widely. A comprehensive understanding of the dynamic capillary effect is needed for the investigation of the two-phase flow in porous media by various methods. In general, dynamic capillary effect in porous media can be studied through the laboratory experiment, pore-to macro-scale modeling, and artificial neural network. Here, main principle and research procedures of each method are reviewed in detail. Then, research progress, disadvantages and advantages are discussed, respectively. In addition, upscaling study from pore-to macro-scale are introduced, which explains the difference between laboratory experiment and pore-scale modeling. At last, several future perspectives and recommendations for optimal solution of dynamic capillary effect are presented.展开更多
In this study,we focus mainly on the problem of finding the minimum-length path through a set of circular regions by a fixed-wing unmanned aerial vehicle.Such a problem is referred to as the Dubins traveling salesman ...In this study,we focus mainly on the problem of finding the minimum-length path through a set of circular regions by a fixed-wing unmanned aerial vehicle.Such a problem is referred to as the Dubins traveling salesman problem with neighborhoods(DTSPN).Algorithms developed in the literature for solving DTSPN either are computationally demanding or generate low-quality solutions.To achieve a better trade-off between solution quality and computational cost,an efficient gradient-free descent method is designed.The core idea of the descent method is to decompose DTSPN into a series of subproblems,each of which consists of finding the minimum-length path of a Dubins vehicle from a configuration to another configuration via an intermediate circular region.By analyzing the geometric properties of the subproblems,we use a bisection method to solve the subproblems.As a result,the descent method can efficiently address DTSPN by successively solving a series of subproblems.Finally,several numerical experiments are carried out to demonstrate the descent method in comparison with several existing algorithms.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 42102149)the Fundamental Research Funds for the Central Universities (No. 2462021YXZZ005)。
文摘The relationship between capillary pressure and saturation plays a critical role in the characterization of two-phase flow and transport in aquifers and oil reservoirs. This relationship is usually determined under the static condition, where capillary pressure is the only function of saturation. However,considerable experiments have suggested that the dependence of capillary pressure on desaturation rate is under the dynamic condition. Thus, a more general description of capillary pressure that includes dynamic capillary effect has been approved widely. A comprehensive understanding of the dynamic capillary effect is needed for the investigation of the two-phase flow in porous media by various methods. In general, dynamic capillary effect in porous media can be studied through the laboratory experiment, pore-to macro-scale modeling, and artificial neural network. Here, main principle and research procedures of each method are reviewed in detail. Then, research progress, disadvantages and advantages are discussed, respectively. In addition, upscaling study from pore-to macro-scale are introduced, which explains the difference between laboratory experiment and pore-scale modeling. At last, several future perspectives and recommendations for optimal solution of dynamic capillary effect are presented.
基金Project supported by the National Natural Science Foundation of China(Nos.61903331 and 61703366)the Fundamental Research Funds for the Central Universities,China(No.2019FZA4024)。
文摘In this study,we focus mainly on the problem of finding the minimum-length path through a set of circular regions by a fixed-wing unmanned aerial vehicle.Such a problem is referred to as the Dubins traveling salesman problem with neighborhoods(DTSPN).Algorithms developed in the literature for solving DTSPN either are computationally demanding or generate low-quality solutions.To achieve a better trade-off between solution quality and computational cost,an efficient gradient-free descent method is designed.The core idea of the descent method is to decompose DTSPN into a series of subproblems,each of which consists of finding the minimum-length path of a Dubins vehicle from a configuration to another configuration via an intermediate circular region.By analyzing the geometric properties of the subproblems,we use a bisection method to solve the subproblems.As a result,the descent method can efficiently address DTSPN by successively solving a series of subproblems.Finally,several numerical experiments are carried out to demonstrate the descent method in comparison with several existing algorithms.
