Based on the idea of the developed 3D-FSM.DDM boundary element method, the field with muti-medium was formulized firstly, then connected at the interface of two fields according to the continuous conditions of stress ...Based on the idea of the developed 3D-FSM.DDM boundary element method, the field with muti-medium was formulized firstly, then connected at the interface of two fields according to the continuous conditions of stress and displacement, after that, a boundary value problem with unified model was formed and solved. Ultimately, an applied numerical simulation system was developed. It was compared with the model having analytical solution for verifying the applicability and the calculating precision.展开更多
To achieve the dual demand of resisting violent impact and attenuating vibration in vibration-impact-safety of protection for precision equipment such as MEMS packaging system, a theo- retical mathematical model of mu...To achieve the dual demand of resisting violent impact and attenuating vibration in vibration-impact-safety of protection for precision equipment such as MEMS packaging system, a theo- retical mathematical model of multi-medium coupling shock absorber is presented. The coupling of quadratic damping, linear damping, Coulomb damping and nonlinear spring are considered in the model. The approximate theoretical calculating formulae are deduced by introducing transformation-tactics. The contrasts between the analytical results and numerical integration results are developed. The resisting impact characteristics of the model are also analyzed in progress. In the meantime, the optimum model of the parameters matching selection for design of the shock absorber is built. The example design is illustrated to confirm the validity of the modeling method and the theoretical solution.展开更多
The effects of non-physical mixing on interface development are still not reasonably evaluated when diffuse interface methods(DIMs)are employed to treat the two-medium flows with immiscible interfaces,especially for c...The effects of non-physical mixing on interface development are still not reasonably evaluated when diffuse interface methods(DIMs)are employed to treat the two-medium flows with immiscible interfaces,especially for compressible multimedium flows with geometrical source terms.In this work,we simulate radially symmetric multi-medium flows employing the sharp interface methods(SIMs)and DIMs to evaluate their performance such as pressure dislocations,mass conservation,and convergence.The g-based model and the five-equation transport model are two common DIMs,which are extended to equations with geometrical source terms combined with discontinuous Galerkin(DG)methods.For the SIMs,we employ the classical modified ghost fluid method(MGFM)and its second-order extension(2nd-MGFM)developed recently.Numerical results exhibit that the 2nd-MGFM is more effective in maintaining the interfacial pressure equilibrium relative to the MGFM.The DIMs can always maintain the pressure continuity naturally and total mass conservation,which is not available for SIMs.Further,under the premise of immiscible interfaces defined artificially,the DIMs cannot provide satisfactory single medium mass conservation,while the SIMs have a smaller mass error.In addition,compared to the other three methods,the 2nd-MGFM has higher confidence for radially symmetric flows,matching the exact solution in sparser grids.展开更多
Tight multi-medium oil reservoirs are the main source of hydrocarbon resources around the world.Acid fracturing is the most effective technology to improve productivity in such reservoirs.As carbonates are primarily c...Tight multi-medium oil reservoirs are the main source of hydrocarbon resources around the world.Acid fracturing is the most effective technology to improve productivity in such reservoirs.As carbonates are primarily composed of dolomite and calcite,which are easily dissolved by hydrochloric acid,high-permeability region will be formed near the well along with the main artificial fracture when acid fracturing is implemented in tight multi-medium oil reservoirs.In this study,a comprehensive composite linear flow model was developed to simulate the transient pressure behavior of an acid fracturing vertical well in a naturally fractured vuggy carbonate reservoir.By utilizing Pedrosa's substitution,perturbation,Laplace transformation and Stehfest numerical inversion technol-ogy,the pressure behavior results were obtained in real time domain.Furthermore,the result of this model was validated by comparing with those of previous literature.Additionally,the influences of some prevailing parameters on the type curves were analyzed.Moreover,the proposed model was applied to an acid fracturing well to evaluate the effectiveness of acid fracturing measures,to demonstrate the practicability of the proposed model.展开更多
为了更好地模拟多材料介质无压渗流问题,提出了一种基于颗粒离散元的离散颗粒渗流模型(discrete seepage element model,DSEM)。该模型将连续介质离散化为密集堆积的颗粒系统,赋予颗粒流体性质,并通过颗粒间压力差模拟渗流过程。DSEM模...为了更好地模拟多材料介质无压渗流问题,提出了一种基于颗粒离散元的离散颗粒渗流模型(discrete seepage element model,DSEM)。该模型将连续介质离散化为密集堆积的颗粒系统,赋予颗粒流体性质,并通过颗粒间压力差模拟渗流过程。DSEM模型能够自动计算自由面位置和水头分布,无须预设自由面位置。为了验证DSEM模型的有效性,首先,模拟了土坝渗流问题,模拟结果与室内模型试验结果一致。随后,模拟了双材料矩形坝和分层土体渗流问题,并与其他数值方法进行比较,证明了DSEM在多种材料问题中的有效性。最后,将DSEM应用于分区梯形坝的渗流问题,成功计算了不同渗透系数下的自由面位置。研究结果表明,DSEM模型适用于多材料介质的无压渗流问题,为工程渗流问题提供了一种新的有效计算方法。展开更多
文摘Based on the idea of the developed 3D-FSM.DDM boundary element method, the field with muti-medium was formulized firstly, then connected at the interface of two fields according to the continuous conditions of stress and displacement, after that, a boundary value problem with unified model was formed and solved. Ultimately, an applied numerical simulation system was developed. It was compared with the model having analytical solution for verifying the applicability and the calculating precision.
基金This project is supported by National Defense Science Foundation of China (No.00J16.2.5.DZ0502)Foundation for Qualified Personnel of Jiangsu University, China(No.04JDG027)Provincial Natural Science Foundation of Guangxi. China(No.0339037, No.0141042).
文摘To achieve the dual demand of resisting violent impact and attenuating vibration in vibration-impact-safety of protection for precision equipment such as MEMS packaging system, a theo- retical mathematical model of multi-medium coupling shock absorber is presented. The coupling of quadratic damping, linear damping, Coulomb damping and nonlinear spring are considered in the model. The approximate theoretical calculating formulae are deduced by introducing transformation-tactics. The contrasts between the analytical results and numerical integration results are developed. The resisting impact characteristics of the model are also analyzed in progress. In the meantime, the optimum model of the parameters matching selection for design of the shock absorber is built. The example design is illustrated to confirm the validity of the modeling method and the theoretical solution.
基金supported under the National Natural Science Foundation of China(No.12101029)the Postdoctoral Fellowship Program of CPSF under Grant(No.GZC20233380).
文摘The effects of non-physical mixing on interface development are still not reasonably evaluated when diffuse interface methods(DIMs)are employed to treat the two-medium flows with immiscible interfaces,especially for compressible multimedium flows with geometrical source terms.In this work,we simulate radially symmetric multi-medium flows employing the sharp interface methods(SIMs)and DIMs to evaluate their performance such as pressure dislocations,mass conservation,and convergence.The g-based model and the five-equation transport model are two common DIMs,which are extended to equations with geometrical source terms combined with discontinuous Galerkin(DG)methods.For the SIMs,we employ the classical modified ghost fluid method(MGFM)and its second-order extension(2nd-MGFM)developed recently.Numerical results exhibit that the 2nd-MGFM is more effective in maintaining the interfacial pressure equilibrium relative to the MGFM.The DIMs can always maintain the pressure continuity naturally and total mass conservation,which is not available for SIMs.Further,under the premise of immiscible interfaces defined artificially,the DIMs cannot provide satisfactory single medium mass conservation,while the SIMs have a smaller mass error.In addition,compared to the other three methods,the 2nd-MGFM has higher confidence for radially symmetric flows,matching the exact solution in sparser grids.
文摘Tight multi-medium oil reservoirs are the main source of hydrocarbon resources around the world.Acid fracturing is the most effective technology to improve productivity in such reservoirs.As carbonates are primarily composed of dolomite and calcite,which are easily dissolved by hydrochloric acid,high-permeability region will be formed near the well along with the main artificial fracture when acid fracturing is implemented in tight multi-medium oil reservoirs.In this study,a comprehensive composite linear flow model was developed to simulate the transient pressure behavior of an acid fracturing vertical well in a naturally fractured vuggy carbonate reservoir.By utilizing Pedrosa's substitution,perturbation,Laplace transformation and Stehfest numerical inversion technol-ogy,the pressure behavior results were obtained in real time domain.Furthermore,the result of this model was validated by comparing with those of previous literature.Additionally,the influences of some prevailing parameters on the type curves were analyzed.Moreover,the proposed model was applied to an acid fracturing well to evaluate the effectiveness of acid fracturing measures,to demonstrate the practicability of the proposed model.
文摘为了更好地模拟多材料介质无压渗流问题,提出了一种基于颗粒离散元的离散颗粒渗流模型(discrete seepage element model,DSEM)。该模型将连续介质离散化为密集堆积的颗粒系统,赋予颗粒流体性质,并通过颗粒间压力差模拟渗流过程。DSEM模型能够自动计算自由面位置和水头分布,无须预设自由面位置。为了验证DSEM模型的有效性,首先,模拟了土坝渗流问题,模拟结果与室内模型试验结果一致。随后,模拟了双材料矩形坝和分层土体渗流问题,并与其他数值方法进行比较,证明了DSEM在多种材料问题中的有效性。最后,将DSEM应用于分区梯形坝的渗流问题,成功计算了不同渗透系数下的自由面位置。研究结果表明,DSEM模型适用于多材料介质的无压渗流问题,为工程渗流问题提供了一种新的有效计算方法。
