In this paper, the boundary element method is applied to investigate the internal state of stress of autofretted tube with notch and the calculated results are important in the practical design.
In this paper we consider two problems. The first is connected with the optimal recovery of functions satisfyiog boundary conditions. The second is the characterization of the unique func- tion whose r-th derivative h...In this paper we consider two problems. The first is connected with the optimal recovery of functions satisfyiog boundary conditions. The second is the characterization of the unique func- tion whose r-th derivative has minimum L_∞-norm, taking given values of alternating signs and satis fying boundary conditions.展开更多
The numerical quadrature methods for dealing with the problems of singular and near-singular integrals caused by Burton-Miller method are proposed, by which the conventional and fast multipole BEMs （boundary element ...The numerical quadrature methods for dealing with the problems of singular and near-singular integrals caused by Burton-Miller method are proposed, by which the conventional and fast multipole BEMs （boundary element methods） for 3D acoustic problems based on constant elements are improved. To solve the problem of singular integrals, a Hadamard finite-part integral method is presented, which is a simplified combination of the methods proposed by Kirkup and Wolf. The problem of near-singular integrals is overcome by the simple method of polar transformation and the more complex method of PART （Projection and Angular ＆ Radial Transformation）. The effectiveness of these methods for solving the singular and near-singular problems is validated through comparing with the results computed by the analytical method and/or the commercial software LMS Virtual.Lab. In addition, the influence of the near-singular integral problem on the computational precisions is analyzed by computing the errors relative to the exact solution. The computational complexities of the conventional and fast multipole BEM are analyzed and compared through numerical computations. A large-scale acoustic scattering problem, whose degree of freedoms is about 340,000, is implemented successfully. The results show that, the near singularity is primarily introduced by the hyper-singular kernel, and has great influences on the precision of the solution. The precision of fast multipole BEM is the same as conventional BEM, but the computational complexities are much lower.展开更多
A numerical method of solving acoustic wave scattering pnblem in fluids is described. Radiation boundary condition (RBC) obtained by factorization method of Helmholtz equation is applied to transforming the exterior b...A numerical method of solving acoustic wave scattering pnblem in fluids is described. Radiation boundary condition (RBC) obtained by factorization method of Helmholtz equation is applied to transforming the exterior boundary value problem in unbounded region into one in a finite region. Combined with RBC and scatterer surface boundary condition, Helmholtz equation is solved numerically by the finite difference method. Computational results for sphere and prolate spheroidal scatterers are in excellent agreement with eigenfunction solutions and much better than the results of OSRC method.展开更多
To solve the problem whereby an oil reservoir with applicable boundaries of the current sand-inhibiting and water-control agent is unclear,a supramolecular sand-inhibiting and water-control agent PDKM was prepared usi...To solve the problem whereby an oil reservoir with applicable boundaries of the current sand-inhibiting and water-control agent is unclear,a supramolecular sand-inhibiting and water-control agent PDKM was prepared using acrylamide(AM),methacryloxyethyltrimethyl ammonium chloride(DMC),styrene(SM),and γ-methacryloyloxypropyltrimethoxysilane(KH570)as comonomers.The molecular structure of PDKM was verified by ^(1)H-NMR and FT-IR.On the basis of establishing an evaluation method that can screen the performance of sand-inhibiting agent at a flow rate of 100 mL/min,the oil reservoir applicable boundaries of PDKM were obtained through the evaluation of sand-inhibiting and water-control performance.The experimental results show that when the concentration of PDKM is 5000 mg/L,the oil reservoir conditions are temperature≤90℃,formation water salinity≤21,249 mg/L,the degree of sand production corresponding to slight sand production and particle migration,crude oil viscosity≤50 mPa⋅s,primary water flooding water cut≥75%,and formation permeability contrast≤2.The performance with respect to sand inhibiting and water control can all reach an excellent level.There-fore,the PDKM solves the problem whereby the applicability of the current sand-inhibiting and water-control agent is unclear,and provides direction for the selection of suitable products in the oilfield production site.展开更多
文摘In this paper, the boundary element method is applied to investigate the internal state of stress of autofretted tube with notch and the calculated results are important in the practical design.
基金Partially supported by Ministry of Science under Project MM--414.
文摘In this paper we consider two problems. The first is connected with the optimal recovery of functions satisfyiog boundary conditions. The second is the characterization of the unique func- tion whose r-th derivative has minimum L_∞-norm, taking given values of alternating signs and satis fying boundary conditions.
基金supported by the National Natural Science Foundation of China(11304344,11404364)the Project of Hubei Provincial Department of Education(D20141803)+1 种基金the Natural Science Foundation of Hubei Province(2014CFB378)the Doctoral Scientific Research Foundation of Hubei University of Automotive Technology(BK201604)
文摘The numerical quadrature methods for dealing with the problems of singular and near-singular integrals caused by Burton-Miller method are proposed, by which the conventional and fast multipole BEMs （boundary element methods） for 3D acoustic problems based on constant elements are improved. To solve the problem of singular integrals, a Hadamard finite-part integral method is presented, which is a simplified combination of the methods proposed by Kirkup and Wolf. The problem of near-singular integrals is overcome by the simple method of polar transformation and the more complex method of PART （Projection and Angular ＆ Radial Transformation）. The effectiveness of these methods for solving the singular and near-singular problems is validated through comparing with the results computed by the analytical method and/or the commercial software LMS Virtual.Lab. In addition, the influence of the near-singular integral problem on the computational precisions is analyzed by computing the errors relative to the exact solution. The computational complexities of the conventional and fast multipole BEM are analyzed and compared through numerical computations. A large-scale acoustic scattering problem, whose degree of freedoms is about 340,000, is implemented successfully. The results show that, the near singularity is primarily introduced by the hyper-singular kernel, and has great influences on the precision of the solution. The precision of fast multipole BEM is the same as conventional BEM, but the computational complexities are much lower.
基金The Project is supported by the National Natural Science Foundation of China.
文摘A numerical method of solving acoustic wave scattering pnblem in fluids is described. Radiation boundary condition (RBC) obtained by factorization method of Helmholtz equation is applied to transforming the exterior boundary value problem in unbounded region into one in a finite region. Combined with RBC and scatterer surface boundary condition, Helmholtz equation is solved numerically by the finite difference method. Computational results for sphere and prolate spheroidal scatterers are in excellent agreement with eigenfunction solutions and much better than the results of OSRC method.
基金supported by the National Natural Science Foundation of China(General Program)(Grant No.52474071)the Provincial Key R&D Program of Shandong(2022CXGC020303)the financial support from the China Scholarship Council(TM Lei,Grant No.202406450004).
文摘To solve the problem whereby an oil reservoir with applicable boundaries of the current sand-inhibiting and water-control agent is unclear,a supramolecular sand-inhibiting and water-control agent PDKM was prepared using acrylamide(AM),methacryloxyethyltrimethyl ammonium chloride(DMC),styrene(SM),and γ-methacryloyloxypropyltrimethoxysilane(KH570)as comonomers.The molecular structure of PDKM was verified by ^(1)H-NMR and FT-IR.On the basis of establishing an evaluation method that can screen the performance of sand-inhibiting agent at a flow rate of 100 mL/min,the oil reservoir applicable boundaries of PDKM were obtained through the evaluation of sand-inhibiting and water-control performance.The experimental results show that when the concentration of PDKM is 5000 mg/L,the oil reservoir conditions are temperature≤90℃,formation water salinity≤21,249 mg/L,the degree of sand production corresponding to slight sand production and particle migration,crude oil viscosity≤50 mPa⋅s,primary water flooding water cut≥75%,and formation permeability contrast≤2.The performance with respect to sand inhibiting and water control can all reach an excellent level.There-fore,the PDKM solves the problem whereby the applicability of the current sand-inhibiting and water-control agent is unclear,and provides direction for the selection of suitable products in the oilfield production site.
