This work deals with an application in parametric modeling of problems regarding pipelines buried in static system, written in C＋＋ using ObjectARX functions. The application is fully integrated with AutoCAD through ...This work deals with an application in parametric modeling of problems regarding pipelines buried in static system, written in C＋＋ using ObjectARX functions. The application is fully integrated with AutoCAD through saproms.dll and saproms.arx libraries where the stages of pre-processing, processing and post-processing are done in AutoCAD sotlware environment itself without having to export data to another processing environment. The analysis processing is done by functions whose algorithms are based on the solution of the coupling between the FEM （finite element method） and the BEM （boundary element method）. The representation of the homogeneous pipeline is made by the FEM using a finite element in the form of a cylindrical panel called CYS （cylindrical shell）, developed from the homogeneous isotropic model proposed initially by Djoudi Bahai, who uses the philosophy of the assumed deformation model （assumed strain based model）. The soil is taken to be a continuum infinite or semi-infinite elastic solid patterned by BEM where special boundary elements are proposed with curved surface or curved edges to represent the soil-structure interaction mainly in the areas of contact with the pipeline.展开更多
This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design metho...This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements ofT-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.展开更多
Electromagnetic tomography(EMT) is a non-invasive imaging technique capable of mapping the conductivity and permeability of an object. In EMT, eddy currents are induced in the object by the activation coils,and the re...Electromagnetic tomography(EMT) is a non-invasive imaging technique capable of mapping the conductivity and permeability of an object. In EMT, eddy currents are induced in the object by the activation coils,and the receiving coils can measure the EMT voltages. When the activation frequency is significantly large, we can treat the metallic targets as electrically perfect conductors(EPCs). In this situation, a thin skin approximation is reasonable and this type of scattering problem can be effectively treated by the boundary element method(BEM)formulated through integration equations. In this study, we compute three-dimensional(3D) sensitivity matrix between the sensors due to an EPC perturbation. Efficiency improvement is achieved through the utility of scalar magnetic potential. Two EPC objects, one sphere and one cube shaped, are simulated. The results agree well with the H dot H formula. Overall, we conclude that BEM can be used to calculate the 3D sensitivity matrix of an EMT system efficiently. This method is a general one for any shaped objects while the H dot H solution is only capable of producing the response for a small ball.展开更多
The boundary element method(BEM)is a popular method for solving acoustic wave propagation problems,especially those in exterior domains,owing to its ease in handling radiation conditions at infinity.However,BEM models...The boundary element method(BEM)is a popular method for solving acoustic wave propagation problems,especially those in exterior domains,owing to its ease in handling radiation conditions at infinity.However,BEM models must meet the requirement of 6–10 elements per wavelength,using the conventional constant,linear,or quadratic elements.Therefore,a large storage size of memory and long solution time are often needed in solving higher-frequency problems.In this work,we propose two new types of enriched elements based on conventional constant boundary elements to improve the computational efficiency of the 2D acoustic BEM.The first one uses a plane wave expansion,which can be used to model scattering problems.The second one uses a special plane wave expansion,which can be used tomodel radiation problems.Five examples are investigated to showthe advantages of the enriched elements.Compared with the conventional constant elements,the new enriched elements can deliver results with the same accuracy and in less computational time.This improvement in the computational efficiency is more evident at higher frequencies(with the nondimensional wave numbers exceeding 100).The paper concludes with the potential of our proposed enriched elements and plans for their further improvement.展开更多
The paper presents the variational formulation and well posedness of the coupling method offinite elements and boundary elements for radiation problem. The convergence and optimal errorestimate for the approximate sol...The paper presents the variational formulation and well posedness of the coupling method offinite elements and boundary elements for radiation problem. The convergence and optimal errorestimate for the approximate solution and numerical experiment are provided.展开更多
With the aid of the properties of the hypersingular kernels, a geometric conversion approach was presented in this paper. The conversion leads to a general approach for the accurate and reliable numerical evaluation o...With the aid of the properties of the hypersingular kernels, a geometric conversion approach was presented in this paper. The conversion leads to a general approach for the accurate and reliable numerical evaluation of the hypersingular surface boundary integrals encountered in a variety of applications with boundary element method. Based on the conversion, the hypersingularity in the boundary integrals could be lowered by one order, resulting in the simplification of the computer code. Moreover, an integral transformation was introduced to damp out the nearly singular behavior of the kernels by the distance function defined in the local polar coordinate system for the nearly hypersingular case. The approach is simple to use, which can be inserted readily to computer code, thus getting rid of the dull routine deduction of formulae before the numerical implementations, as the expressions of these kernels are in general complicated. The numerical examples were given in three dimensional elasticity, verifying the effectiveness of the proposed approach, which makes it possible to observe numerically the behavior of the boundary integral values with hypersingular kernels across the boundary.展开更多
To address the issue that traditional finite element methods cannot fully consider the semi-infinite earth strata and have lower solution accuracy,a new equivalent force model for induced deformation during oil and ga...To address the issue that traditional finite element methods cannot fully consider the semi-infinite earth strata and have lower solution accuracy,a new equivalent force model for induced deformation during oil and gas reservoir development is derived from the perspective of semi-infinite strata.A brand-new volume boundary element numerical method solution has been developed and verified and tested.The influences of internal flow and flow boundary of the reservoir on strata deformation are equivalent to the impacts on strata deformation when external forces act at the interior and boundary of the reservoir,respectively.Calculation methods for the flow equivalent force and boundary equivalent force are provided.The deformation solution at any point in the strata can be obtained through the convolution of flow equivalent forces,boundary equivalent forces and Green’s functions.After discretization,the deformation solution at any point in the strata can be obtained by multiplying the grid boundary equivalent forces,grid flow equivalent forces with their corresponding grid boundary sources and grid volume sources respectively,and then summing them up.This numerical method is termed the Volumetric Boundary Element Method(VBEM).Compared with traditional commercial simulators,VBEM fully considers the effects of reservoir flow boundaries,pore pressure gradient fields within the reservoir,and fluid mass changes within pores on formation deformation.It eliminates the need for meshing outside the reservoir,achieves significantly improved solution accuracy,and provides a new technical framework for simulating deformation induced by reservoir development.展开更多
In low-permeability geothermal reservoirs,hydro-shearing of pre-existing natural fractures plays a crucial role in improving connectivity between injection and production wells,thereby enhancing heat extraction effici...In low-permeability geothermal reservoirs,hydro-shearing of pre-existing natural fractures plays a crucial role in improving connectivity between injection and production wells,thereby enhancing heat extraction efficiency.This process increases fracture conductivity through dilation caused by injectioninduced slip;however,it also carries the risk of inducing seismic events,posing significant challenges for geothermal operations.This study employs a coupled hydro-mechanical numerical model based on the boundary element method to simulate hydro-shearing under two distinct fluid injection scenarios:(1)monotonic injection and(2)cyclic injection regulated by a traffic light system(TLS).The model assesses the effectiveness of these injection regimes in enhancing fracture conductivity while mitigating seismic hazards.Results indicate that monotonic injection frequently triggers a cascade of seismic events,disrupting pressure and stress distributions on nearby faults and resulting in complex seismic and aseismic interactions.In contrast,TLS-regulated cyclic injection,when carefully managed,promotes stable slip behavior and improves fracture conductivity.This approach proves particularly effective over extended durations during the simultaneous stimulation of two parallel faults.However,in multi-stage stimulation scenariosdwhere natural fractures are stimulated sequentiallydTLS-based cyclic injection,while more efficient at enhancing conductivity,may increase seismicity risk with prolonged application,thereby limiting its safe operational window.展开更多
Hydraulic fracturing plays a critical role in enhancing shale gas production in deep shale reservoirs.Conventional hydraulic fracturing simulation methods rely on prefabricated grids,which can be hindered by the chall...Hydraulic fracturing plays a critical role in enhancing shale gas production in deep shale reservoirs.Conventional hydraulic fracturing simulation methods rely on prefabricated grids,which can be hindered by the challenge of being computationally overpowered.This study proposes an efficient fracturing simulator to analyze fracture morphology during hydraulic fracturing processes in deep shale gas reservoirs.The simulator integrates the boundary element displacement discontinuity method and the finite volume method to model the fluid-solid coupling process by employing a pseudo-3D fracture model to calculate the fracture height.In particular,the Broyden iteration method was introduced to improve the computational efficiency and model robustness;it achieved a 46.6%reduction in computation time compared to the Newton-Raphson method.The influences of horizontal stress differences,natural fracture density,and natural fracture angle on the modified zone of the reservoir were simulated,and the following results were observed.(1)High stress difference reservoirs have smaller stimulated reservoir area than low stress difference reservoirs.(2)A higher natural fracture angle resulted in larger modification zones at low stress differences,while the effect of a natural fracture angle at high stress differences was not significant.(3)High-density and long natural fracture zones played a significant role in enhancing the stimulated reservoir area.These findings are critical for comprehending the impact of geological parameters on deep shale reservoirs.展开更多
This study explores a sensitivity analysis method based on the boundary element method(BEM)to address the computational complexity in acoustic analysis with ground reflection problems.The advantages of BEM in acoustic...This study explores a sensitivity analysis method based on the boundary element method(BEM)to address the computational complexity in acoustic analysis with ground reflection problems.The advantages of BEM in acoustic simulations and its high computational cost in broadband problems are examined.To improve efficiency,a Taylor series expansion is applied to decouple frequency-dependent terms in BEM.Additionally,the SecondOrder Arnoldi(SOAR)model order reduction method is integrated to reduce computational costs and enhance numerical stability.Furthermore,an isogeometric sensitivity boundary integral equation is formulated using the direct differentiation method,incorporating Cauchy principal value integrals and Hadamard finite part integrals to handle singularities.The proposed method improves the computational efficiency,and the acoustic sensitivity analysis provides theoretical support for further acoustic structure optimization.展开更多
The stochastic boundary element method(SBEM)is developed in this paper for 3D problems with body forces and reliability analysis of engineering structures.The integral equations of SBEM are established by the approach...The stochastic boundary element method(SBEM)is developed in this paper for 3D problems with body forces and reliability analysis of engineering structures.The integral equations of SBEM are established by the approach of partial derivation with respect to stochastic variables,considering the yield limit,rotation speeds and material density to be the fundamental stochastic variables.Through analyzing a numerical example and a turbo-disk of an aeroengine,the results show that the method developed is successful.展开更多
In this paper, an identification method to estimate the unbalances is introduced, which is based on the boundary element method (BEM). By using the vibration response measured at some points on the flexible rotor the ...In this paper, an identification method to estimate the unbalances is introduced, which is based on the boundary element method (BEM). By using the vibration response measured at some points on the flexible rotor the unbalances can be identified conveniently. Therefore, the rotor can be balanced without test runs.展开更多
The matrix expression for the 3 D transient dynamic boundary integral equation in Laplace transform space is obtained and the degenerative element method has been implemented to treat the kernel function over the sin...The matrix expression for the 3 D transient dynamic boundary integral equation in Laplace transform space is obtained and the degenerative element method has been implemented to treat the kernel function over the singular element. In the computer program BEMTDY the Koizumi′s numerical inversion method is used and three examples of the 3 D vibrated foundation under harmonic forces and the influence with both adjacent foundations are studied.展开更多
An analytical model of a floating heaving box integrated with a vertical flexible porous membrane placed right next to the box applications to wave energy extraction and breakwater systems is developed under the reduc...An analytical model of a floating heaving box integrated with a vertical flexible porous membrane placed right next to the box applications to wave energy extraction and breakwater systems is developed under the reduced wave equation.The theoretical solutions for the heave radiating potential to the assigned physical model in the corresponding zones are attained by using the separation of variables approach along with the Fourier expansion.Applying the matching eigenfunction expansion technique and orthogonal conditions,the unknown coefficients that are involved in the radiated potentials are determined.The attained radiation potential allows the computation of hydrodynamic coefficients of the heaving buoy,Power Take-Off damping,and wave quantities.The accuracy of the analytical solution for the hydrodynamic coefficients is demonstrated for different oblique angles with varying numbers of terms in the series solution.The current analytical analysis findings are confirmed by existing published numerical boundary element method simulations.Several numerical results of the hydrodynamic coefficients,power capture,power take-off optimal damping,and transmission coefficients for numerous structural and physical aspects are conducted.It has been noted that the ideal power take-off damping increases as the angle of incidence rises,and the analysis suggests that the ability to capture waves is more effective in shallower waters compared to deeper ones.展开更多
Due to its architecture,the graphics processing unit(GPU)is specially well-suited to address problems that can be expressed as data-parallel computations with high arithmetic intensity.One example of such problem is t...Due to its architecture,the graphics processing unit(GPU)is specially well-suited to address problems that can be expressed as data-parallel computations with high arithmetic intensity.One example of such problem is the Boundary Elements Method(BEM).This work addresses the implementation of the direct version of BEM for 2D elastostatics.For the present implementation,constant boundary elements are used.According to the formulation of BEM,every term of both influence matrices(G^ij and H^ij)is independent of each other.In classical CPU serial implementations,these terms are calculated in a sequence of two loops:for the field point i and for the source point j.On the other hand,from the point of view of the GPU parallel processing paradigm,the calculation of every one of these terms can be assigned to a thread(GPU's elementary unit of calculation)and calculated simultaneously.The transposition of the influence equation to an algebraic linear system of equations is also parallelized.Standard Gaussian quadrature is applied to integrate each term of influence matrices.The code was developed on a NVidia CUDA programming environment and executed on a GeForce GTX 280 graphics card hosted by a regular Intel Core2Duo CPU.The efficiency of the implemented strategies is investigated by solving a classical elastostatics problem.展开更多
This work deals with the analysis of soil-structure interaction modeling of pipeline problems in static behavior using the coupling between FEM(finite element method)and BEM(boundary element method).The representation...This work deals with the analysis of soil-structure interaction modeling of pipeline problems in static behavior using the coupling between FEM(finite element method)and BEM(boundary element method).The representation of the pipe is made by MEF using one fmite element in the cylindrical panel formulated from the theory of equivalent discrete layers(Layerwise theory),proposed by J.N.Reddy.The soil is represented by elastic continum infimite or semi-infinite and modeled using boundary elements with special curved surface,associated with cylindrical panel used to represent the soil-structure interaction within the soil,especially at the contact surface with the pipe.展开更多
This paper develops the boundary element method, the authors employ two-layered earth Green 's functions as the weighting functions of residual and derive boundary integral equations. The forward problems of point...This paper develops the boundary element method, the authors employ two-layered earth Green 's functions as the weighting functions of residual and derive boundary integral equations. The forward problems of point sources on 2 - D and 3-D structures with an influencing cover are solved by this method. The results show that this method markedly improves the original boundary element method. The features of the improved method are greater numerical accuracy and much smaller systems of equations and thus considerable savings for the storage capacity of computers, allowing us to solve the above problems with only ordinary microcomputers. The results in this paper extend the scope of applying the boundary element method while using electrical methods for geophysical prospecting.展开更多
In the present paper, we examine the performance of an efficient type of wave-absorbing porous marine structure under the attack of regular oblique waves by using a Multi-Domain Boundary Element Method(MDBEM). The str...In the present paper, we examine the performance of an efficient type of wave-absorbing porous marine structure under the attack of regular oblique waves by using a Multi-Domain Boundary Element Method(MDBEM). The structure consists of two perforated vertical thin barriers creating what can be called a wave absorbing chamber system. The barriers are surface piercing, thereby eliminating wave overtopping. The problem of the interaction of obliquely incident linear waves upon a pair of perforated barriers is first formulated in the context of linear diffraction theory. The resulting boundary integral equation, which is matched with far-field solutions presented in terms of analytical series with unknown coefficients, as well as the appropriate boundary conditions at the free surface, seabed, and barriers, is then solved numerically using MDBEM. Dissipation of the wave energy due to the presence of the perforated barriers is represented by a simple yet effective relation in terms of the porosity parameter appropriate for thin perforated walls. The results are presented in terms of reflection and transmission coefficients. The effects of the incident wave angles, relative water depths, porosities, depths of the walls, and other major parameters of interest are explored.展开更多
A high order boundary element method was developed for the complex velocity potential problem. The method ensures not only the continuity of the potential at the nodes of each element but also the velocity. It can be ...A high order boundary element method was developed for the complex velocity potential problem. The method ensures not only the continuity of the potential at the nodes of each element but also the velocity. It can be applied to a variety of velocity potential problems. The present paper, however, focused on its application to the problem of water entry of a wedge with varying speed. The continuity of the velocity achieved herein is particularly important for this kind of nonlinear free surface flow problem, because when the time stepping method is used, the free surface is updated through the velocity obtained at each node and the accuracy of the velocity is therefore crucial. Calculation was made for a case when the distance S that the wedge has travelled and time t follow the relationship s=Dtα, where D and α are constants, which is found to lead to a self similar flow field when the effect due to gravity is ignored.展开更多
文摘This work deals with an application in parametric modeling of problems regarding pipelines buried in static system, written in C＋＋ using ObjectARX functions. The application is fully integrated with AutoCAD through saproms.dll and saproms.arx libraries where the stages of pre-processing, processing and post-processing are done in AutoCAD sotlware environment itself without having to export data to another processing environment. The analysis processing is done by functions whose algorithms are based on the solution of the coupling between the FEM （finite element method） and the BEM （boundary element method）. The representation of the homogeneous pipeline is made by the FEM using a finite element in the form of a cylindrical panel called CYS （cylindrical shell）, developed from the homogeneous isotropic model proposed initially by Djoudi Bahai, who uses the philosophy of the assumed deformation model （assumed strain based model）. The soil is taken to be a continuum infinite or semi-infinite elastic solid patterned by BEM where special boundary elements are proposed with curved surface or curved edges to represent the soil-structure interaction mainly in the areas of contact with the pipeline.
基金International Science&Technology Cooperation Program of China under Grant No.2014DFA70950Tsinghua University Initiative Scientific Research Program under Grant No.2012THZ02-1National Natural Science Foundation of China under Grant No.91315301
文摘This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements ofT-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.
基金the National Natural Science Foundation of China(No.50937005)the Shanghai Maritime University Science and Technology Program(No.20120064)
文摘Electromagnetic tomography(EMT) is a non-invasive imaging technique capable of mapping the conductivity and permeability of an object. In EMT, eddy currents are induced in the object by the activation coils,and the receiving coils can measure the EMT voltages. When the activation frequency is significantly large, we can treat the metallic targets as electrically perfect conductors(EPCs). In this situation, a thin skin approximation is reasonable and this type of scattering problem can be effectively treated by the boundary element method(BEM)formulated through integration equations. In this study, we compute three-dimensional(3D) sensitivity matrix between the sensors due to an EPC perturbation. Efficiency improvement is achieved through the utility of scalar magnetic potential. Two EPC objects, one sphere and one cube shaped, are simulated. The results agree well with the H dot H formula. Overall, we conclude that BEM can be used to calculate the 3D sensitivity matrix of an EMT system efficiently. This method is a general one for any shaped objects while the H dot H solution is only capable of producing the response for a small ball.
基金the National Natural Science Foundation of China(https://www.nsfc.gov.cn/,Project No.11972179)the Natural Science Foundation of Guangdong Province(http://gdstc.gd.gov.cn/,No.2020A1515010685)the Department of Education of Guangdong Province(http://edu.gd.gov.cn/,No.2020ZDZX2008).
文摘The boundary element method(BEM)is a popular method for solving acoustic wave propagation problems,especially those in exterior domains,owing to its ease in handling radiation conditions at infinity.However,BEM models must meet the requirement of 6–10 elements per wavelength,using the conventional constant,linear,or quadratic elements.Therefore,a large storage size of memory and long solution time are often needed in solving higher-frequency problems.In this work,we propose two new types of enriched elements based on conventional constant boundary elements to improve the computational efficiency of the 2D acoustic BEM.The first one uses a plane wave expansion,which can be used to model scattering problems.The second one uses a special plane wave expansion,which can be used tomodel radiation problems.Five examples are investigated to showthe advantages of the enriched elements.Compared with the conventional constant elements,the new enriched elements can deliver results with the same accuracy and in less computational time.This improvement in the computational efficiency is more evident at higher frequencies(with the nondimensional wave numbers exceeding 100).The paper concludes with the potential of our proposed enriched elements and plans for their further improvement.
基金This research was supported in part by the Institute for Mathematics and its applications with funds provided by NSF, USA
文摘The paper presents the variational formulation and well posedness of the coupling method offinite elements and boundary elements for radiation problem. The convergence and optimal errorestimate for the approximate solution and numerical experiment are provided.
文摘With the aid of the properties of the hypersingular kernels, a geometric conversion approach was presented in this paper. The conversion leads to a general approach for the accurate and reliable numerical evaluation of the hypersingular surface boundary integrals encountered in a variety of applications with boundary element method. Based on the conversion, the hypersingularity in the boundary integrals could be lowered by one order, resulting in the simplification of the computer code. Moreover, an integral transformation was introduced to damp out the nearly singular behavior of the kernels by the distance function defined in the local polar coordinate system for the nearly hypersingular case. The approach is simple to use, which can be inserted readily to computer code, thus getting rid of the dull routine deduction of formulae before the numerical implementations, as the expressions of these kernels are in general complicated. The numerical examples were given in three dimensional elasticity, verifying the effectiveness of the proposed approach, which makes it possible to observe numerically the behavior of the boundary integral values with hypersingular kernels across the boundary.
基金Supported by the China National Natural Science Foundation Project(52274048)Beijing Natural Science Foundation Project(3222037)。
文摘To address the issue that traditional finite element methods cannot fully consider the semi-infinite earth strata and have lower solution accuracy,a new equivalent force model for induced deformation during oil and gas reservoir development is derived from the perspective of semi-infinite strata.A brand-new volume boundary element numerical method solution has been developed and verified and tested.The influences of internal flow and flow boundary of the reservoir on strata deformation are equivalent to the impacts on strata deformation when external forces act at the interior and boundary of the reservoir,respectively.Calculation methods for the flow equivalent force and boundary equivalent force are provided.The deformation solution at any point in the strata can be obtained through the convolution of flow equivalent forces,boundary equivalent forces and Green’s functions.After discretization,the deformation solution at any point in the strata can be obtained by multiplying the grid boundary equivalent forces,grid flow equivalent forces with their corresponding grid boundary sources and grid volume sources respectively,and then summing them up.This numerical method is termed the Volumetric Boundary Element Method(VBEM).Compared with traditional commercial simulators,VBEM fully considers the effects of reservoir flow boundaries,pore pressure gradient fields within the reservoir,and fluid mass changes within pores on formation deformation.It eliminates the need for meshing outside the reservoir,achieves significantly improved solution accuracy,and provides a new technical framework for simulating deformation induced by reservoir development.
基金the financial support of the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(Contract number VHNG-1516).
文摘In low-permeability geothermal reservoirs,hydro-shearing of pre-existing natural fractures plays a crucial role in improving connectivity between injection and production wells,thereby enhancing heat extraction efficiency.This process increases fracture conductivity through dilation caused by injectioninduced slip;however,it also carries the risk of inducing seismic events,posing significant challenges for geothermal operations.This study employs a coupled hydro-mechanical numerical model based on the boundary element method to simulate hydro-shearing under two distinct fluid injection scenarios:(1)monotonic injection and(2)cyclic injection regulated by a traffic light system(TLS).The model assesses the effectiveness of these injection regimes in enhancing fracture conductivity while mitigating seismic hazards.Results indicate that monotonic injection frequently triggers a cascade of seismic events,disrupting pressure and stress distributions on nearby faults and resulting in complex seismic and aseismic interactions.In contrast,TLS-regulated cyclic injection,when carefully managed,promotes stable slip behavior and improves fracture conductivity.This approach proves particularly effective over extended durations during the simultaneous stimulation of two parallel faults.However,in multi-stage stimulation scenariosdwhere natural fractures are stimulated sequentiallydTLS-based cyclic injection,while more efficient at enhancing conductivity,may increase seismicity risk with prolonged application,thereby limiting its safe operational window.
文摘Hydraulic fracturing plays a critical role in enhancing shale gas production in deep shale reservoirs.Conventional hydraulic fracturing simulation methods rely on prefabricated grids,which can be hindered by the challenge of being computationally overpowered.This study proposes an efficient fracturing simulator to analyze fracture morphology during hydraulic fracturing processes in deep shale gas reservoirs.The simulator integrates the boundary element displacement discontinuity method and the finite volume method to model the fluid-solid coupling process by employing a pseudo-3D fracture model to calculate the fracture height.In particular,the Broyden iteration method was introduced to improve the computational efficiency and model robustness;it achieved a 46.6%reduction in computation time compared to the Newton-Raphson method.The influences of horizontal stress differences,natural fracture density,and natural fracture angle on the modified zone of the reservoir were simulated,and the following results were observed.(1)High stress difference reservoirs have smaller stimulated reservoir area than low stress difference reservoirs.(2)A higher natural fracture angle resulted in larger modification zones at low stress differences,while the effect of a natural fracture angle at high stress differences was not significant.(3)High-density and long natural fracture zones played a significant role in enhancing the stimulated reservoir area.These findings are critical for comprehending the impact of geological parameters on deep shale reservoirs.
基金supported by the Shanxi Scholarship Council of China(Grant No.2023-036)the Natural Science Foundation of Shanxi Province(Grant No.202303021222020).
文摘This study explores a sensitivity analysis method based on the boundary element method(BEM)to address the computational complexity in acoustic analysis with ground reflection problems.The advantages of BEM in acoustic simulations and its high computational cost in broadband problems are examined.To improve efficiency,a Taylor series expansion is applied to decouple frequency-dependent terms in BEM.Additionally,the SecondOrder Arnoldi(SOAR)model order reduction method is integrated to reduce computational costs and enhance numerical stability.Furthermore,an isogeometric sensitivity boundary integral equation is formulated using the direct differentiation method,incorporating Cauchy principal value integrals and Hadamard finite part integrals to handle singularities.The proposed method improves the computational efficiency,and the acoustic sensitivity analysis provides theoretical support for further acoustic structure optimization.
文摘The stochastic boundary element method(SBEM)is developed in this paper for 3D problems with body forces and reliability analysis of engineering structures.The integral equations of SBEM are established by the approach of partial derivation with respect to stochastic variables,considering the yield limit,rotation speeds and material density to be the fundamental stochastic variables.Through analyzing a numerical example and a turbo-disk of an aeroengine,the results show that the method developed is successful.
文摘In this paper, an identification method to estimate the unbalances is introduced, which is based on the boundary element method (BEM). By using the vibration response measured at some points on the flexible rotor the unbalances can be identified conveniently. Therefore, the rotor can be balanced without test runs.
文摘The matrix expression for the 3 D transient dynamic boundary integral equation in Laplace transform space is obtained and the degenerative element method has been implemented to treat the kernel function over the singular element. In the computer program BEMTDY the Koizumi′s numerical inversion method is used and three examples of the 3 D vibrated foundation under harmonic forces and the influence with both adjacent foundations are studied.
基金Open access funding provided by FCT|FCCN(b-on)the Strategic Research Plan of the Centre for Marine Technology and Ocean Engineering(CENTEC),which is financed by the Portuguese Foundation for Science and Technology(Fundação para a Ciência e Tecnologia-FCT)under contract UIDB/UIDP/00134/2020.
文摘An analytical model of a floating heaving box integrated with a vertical flexible porous membrane placed right next to the box applications to wave energy extraction and breakwater systems is developed under the reduced wave equation.The theoretical solutions for the heave radiating potential to the assigned physical model in the corresponding zones are attained by using the separation of variables approach along with the Fourier expansion.Applying the matching eigenfunction expansion technique and orthogonal conditions,the unknown coefficients that are involved in the radiated potentials are determined.The attained radiation potential allows the computation of hydrodynamic coefficients of the heaving buoy,Power Take-Off damping,and wave quantities.The accuracy of the analytical solution for the hydrodynamic coefficients is demonstrated for different oblique angles with varying numbers of terms in the series solution.The current analytical analysis findings are confirmed by existing published numerical boundary element method simulations.Several numerical results of the hydrodynamic coefficients,power capture,power take-off optimal damping,and transmission coefficients for numerous structural and physical aspects are conducted.It has been noted that the ideal power take-off damping increases as the angle of incidence rises,and the analysis suggests that the ability to capture waves is more effective in shallower waters compared to deeper ones.
文摘Due to its architecture,the graphics processing unit(GPU)is specially well-suited to address problems that can be expressed as data-parallel computations with high arithmetic intensity.One example of such problem is the Boundary Elements Method(BEM).This work addresses the implementation of the direct version of BEM for 2D elastostatics.For the present implementation,constant boundary elements are used.According to the formulation of BEM,every term of both influence matrices(G^ij and H^ij)is independent of each other.In classical CPU serial implementations,these terms are calculated in a sequence of two loops:for the field point i and for the source point j.On the other hand,from the point of view of the GPU parallel processing paradigm,the calculation of every one of these terms can be assigned to a thread(GPU's elementary unit of calculation)and calculated simultaneously.The transposition of the influence equation to an algebraic linear system of equations is also parallelized.Standard Gaussian quadrature is applied to integrate each term of influence matrices.The code was developed on a NVidia CUDA programming environment and executed on a GeForce GTX 280 graphics card hosted by a regular Intel Core2Duo CPU.The efficiency of the implemented strategies is investigated by solving a classical elastostatics problem.
文摘This work deals with the analysis of soil-structure interaction modeling of pipeline problems in static behavior using the coupling between FEM(finite element method)and BEM(boundary element method).The representation of the pipe is made by MEF using one fmite element in the cylindrical panel formulated from the theory of equivalent discrete layers(Layerwise theory),proposed by J.N.Reddy.The soil is represented by elastic continum infimite or semi-infinite and modeled using boundary elements with special curved surface,associated with cylindrical panel used to represent the soil-structure interaction within the soil,especially at the contact surface with the pipe.
文摘This paper develops the boundary element method, the authors employ two-layered earth Green 's functions as the weighting functions of residual and derive boundary integral equations. The forward problems of point sources on 2 - D and 3-D structures with an influencing cover are solved by this method. The results show that this method markedly improves the original boundary element method. The features of the improved method are greater numerical accuracy and much smaller systems of equations and thus considerable savings for the storage capacity of computers, allowing us to solve the above problems with only ordinary microcomputers. The results in this paper extend the scope of applying the boundary element method while using electrical methods for geophysical prospecting.
文摘In the present paper, we examine the performance of an efficient type of wave-absorbing porous marine structure under the attack of regular oblique waves by using a Multi-Domain Boundary Element Method(MDBEM). The structure consists of two perforated vertical thin barriers creating what can be called a wave absorbing chamber system. The barriers are surface piercing, thereby eliminating wave overtopping. The problem of the interaction of obliquely incident linear waves upon a pair of perforated barriers is first formulated in the context of linear diffraction theory. The resulting boundary integral equation, which is matched with far-field solutions presented in terms of analytical series with unknown coefficients, as well as the appropriate boundary conditions at the free surface, seabed, and barriers, is then solved numerically using MDBEM. Dissipation of the wave energy due to the presence of the perforated barriers is represented by a simple yet effective relation in terms of the porosity parameter appropriate for thin perforated walls. The results are presented in terms of reflection and transmission coefficients. The effects of the incident wave angles, relative water depths, porosities, depths of the walls, and other major parameters of interest are explored.
文摘A high order boundary element method was developed for the complex velocity potential problem. The method ensures not only the continuity of the potential at the nodes of each element but also the velocity. It can be applied to a variety of velocity potential problems. The present paper, however, focused on its application to the problem of water entry of a wedge with varying speed. The continuity of the velocity achieved herein is particularly important for this kind of nonlinear free surface flow problem, because when the time stepping method is used, the free surface is updated through the velocity obtained at each node and the accuracy of the velocity is therefore crucial. Calculation was made for a case when the distance S that the wedge has travelled and time t follow the relationship s=Dtα, where D and α are constants, which is found to lead to a self similar flow field when the effect due to gravity is ignored.
