46 results about "Boundary integral equations" patented technology

The disclosure is directed to a method of representing fluid flow response to imposed conditions in a physical fluid reservoir through wells. The invention utilizes techniques and formulas of unprecedented accuracy and speed for computations for a fundamental element in analysis of fluid movement through subterranean reservoirs—the calculation of Green's and Neumann functions in finite three-dimensional space. The method includes modeling of pressure and/or flow rate observables at wells in said reservoir using an easily computable, closed-form Green's or Neumann function for a linear well segment in arbitrary orientation within a three dimensional cell of spatially invariant but anisotropic permeability. The method further includes the modeling of fluid flow in the physical fluid reservoir with an assemblage of linear well segments operating in unison with uniform flux density to represent arbitrary well trajectory. The method further includes modeling reservoir flow through one or more linear well segments of non-uniform flux related by a constitutive expression linking pressure distribution and flow rate within the well. The method further includes generalization through integration of easily computable Green's or Neumann functions to represent fractures or fractured wells in modeling fluid flow in a physical reservoir. The system includes modeling fluid flow through a mesh representation of the physical fluid reservoir containing one or more wells represented by easily computable Green's or Neumann functions. The system further includes modeling of flow in the physical reservoir via a numerical method in which the values of pressure and flux assigned to the mesh are related to observables at the well using aforementioned easily computable Green's or Neumann functions. The system further includes the coupling of well and mesh values within the numerical solution method for well observation or feedback control. The system still further includes the localization of the well model to the properties assigned to only those mesh elements penetrated by the well using boundary integral equation methods. The invention also incorporates the addition of transients in fluid flow towards a steady or pseudo-steady state, and use thereof, in the above constructs.

The invention provides a three-dimensional numerical simulation method for ship large-scale rolling motion, which comprises the following steps of reading a grid file to carry out ship hydrostatic calculation; calculating an influence coefficient matrix of boundary integral equation for Taylor expansion boundary element method; solving velocity potential of laminated modes and its spatial first and second derivatives and mj terms; carrying out the green's function in time domain and its spatial derivative solution; calculating a roll damping coefficient; carrying out the irregular wave decomposition, linear superposition into incident wave time calendar; carrying out the direct time-domain disturbance wave force calculation by taylor expansion boundary element method; calculating incidentwave force and hydrostatic recovery force; modeling a large-scale motion forecasting equation; using the fourth-order runge-kutta method to solve the motion equation step by step to evaluate the nonlinear motion of the ship in the top wave or oblique wave; and carrying out the numerical simulation and characteristic statistics of ship large amplitude motion in irregular waves. The method of the invention can predict the large amplitude motion of a container ship in regular waves and irregular waves, and can be used for numerical simulation and characteristic statistics of the large amplitude motion of a ship in irregular waves.

A computer program product, an apparatus, and a method for modeling equivalent surface sources on a closed, arbitrarily shaped object that result from the imposition of an arbitrary time-harmonic incident field (e.g., a radar wave) are provided. An object divided into by a plurality of patches 302 and parameters for the incident field and the properties of the object 304 are provided to the system. Next, the system produces a discretized representation of a well-conditioned boundary integral equation in the form of a well-conditioned matrix equation, modeling the interaction between the incident field and the object 306. The well-conditioned linear system is solved numerically to determine equivalent surface sources on the object 308. The equivalent sources may then be used to determine electromagnetic fields resulting therefrom 310. The invention provides improved computational efficiency as well as increased modeling accuracy by effectively reducing the numerical precision necessary.

The invention provides a ship motion prediction method based on a Taylor expansion boundary element method. The method comprises the steps of reading the grid file and carrying out hydrostatic calculation; calculating the influence coefficient matrix of a boundary integral equation needed by the taylor expansion boundary element method; solving the velocity potential of laminated modes and its spatial first and second derivatives and Mj terms; solving the green's function in time domain and its spatial derivative; solving the instantaneous terms of radiation velocity potential and their spatial first and second derivatives; solving the radiation velocity potential memory term and its spatial first and second derivatives; solving the impulse response function of added mass, wave-making damping and radiation wave force; solving the impulse response function of whole wave incident velocity potential; diffraction velocity potential and its first and second derivatives in space, solving theimpulse response function of diffraction wave force; solving the ship motion in full wave direction; analyzing and calculating the ship motion spectrum under different sea conditions. The invention can predict the hydrodynamic coefficients of three main ship types, wave loads, six-degree-of-freedom motion of the ship in full wave direction, and ship motion spectrum analysis under various sea conditions.

The invention discloses a transient temperature calculation method based on an improved triple reciprocal boundary element method, comprising the following steps: adopting a multiple time scheme to determine a calculation time sequence; obtaining a frequency domain equation of a transient heat conduction problem based on Laplace transform, and determining frequency domain parameters of the frequency domain equation based on analysis time t and an inverse Laplace transformation method; obtaining a boundary-domain integral equation of the frequency domain equation based on a modified Helmholtz fundamental solution; based on an improved triple reciprocity formula, transforming a domain integral contained in the boundary-domain integral equation to equivalent boundary integral, to obtain a pure boundary integral equation; solving a frequency domain boundary integral equation based on a theoretical surface mesh of a boundary element method and intra-domain interpolation points; performing inverse Laplace transformation on a solution in frequency domain, and solving time domain temperature distribution. The invention provides an improved triple reciprocity method calculation formula withlow degree of freedom expression, thereby greatly reducing calculation time of the triple reciprocity method and saving storage space at the same time.

The invention discloses a mechanical noise far field sound pressure prediction method based on an inverse boundary element method, and belongs to the sound pressure prediction field. A microphone array is arranged in a wavelength of the highest analysis frequency of a target sound source, a test surface is bigger than a positive projection plane of a target sound source. One wavelength contains at least two measuring points. A reference microphone is arranged near the target sound source, and a field point complex sound pressure after cross spectrum of the microphone array and the reference microphone is obtained through measuring. a transmission relation of a field point complex sound pressure and a normal vibration speed is created based on the inverse boundary element method, and a transmission matrix is obtained. The transmission matrix is subjected to singular value decomposition, and a normal vibration speed is obtained. A far field sound pressure py is predicted according to the normal vibration speed. the relation of the far field sound pressure and the normal vibration speed is created according to a boundary integration equation, py=ATMyvn, and ATMy is the transmission matrix corresponding to the far field sound pressure. The prediction method is suitable for a surface with a complex structure and has an advantage of high precision.

The invention proposes an elastic fracture simulation method based on a dual boundary element and strain energy optimization analysis. The two basic problems related to three-dimensional linear elastic fracture are handled. A model containing an overlapped cleft surface is expressed by using a dual boundary element method, and a super-singular boundary integral equation is solved by using a semi-analytic method. The continuous attribute from the contact load and released by the strain energy at the front end of the crack is represented by introducing a contact force model. A fracture factor ofthe extension distance of the crack is calculated within the fracture duration to perform accurate control on the extension of the cracking end.

The invention relates to a seismic migration method for a coupled transmission coefficient, which comprises the following steps of: 1) dividing different depth layers by taking the earth surface as an initial point, namely dividing underground media to be explored into different depth layers according to different depth intervals, and assuming the different depth intervals of the underground media to be explored as different horizontal sheets, wherein the thickness of the horizontal sheets is the depth interval of the underground media to be explored; 2)based on a Lippmann-Schwinger integral equation, solving the Lippmann-Schwinger equation by establishing an integral equation of an upper boundary gamma1 and a lower boundary gamma2 of a seismic wave field in in the closed area omega of any horizontal sheet; 3) establishing a boundary integral equation at the lower boundary gamma2 of the closed area omega according to a transmission effect of the lower boundary gamma2 of the horizontal sheet; and 4) solving a seismic migration wave field according to the transmission and reflection effects between the horizontal sheets and of the upper boundaries and lower boundaries of the horizontal sheets. The seismic migration method can be widely applied to a seismic migration technology for imaging a complex oil exploration structure.

The invention discloses a method and system for measuring the hydrodynamic response of a floating body under the wave action. The method comprises the following steps of establishing a floating body geometric model and determining a calculation domain; meshing the boundary and storing the node information of the mesh; establishing boundary integral equation and rigid body motion equation; solvingthe boundary integral equation and rigid body motion equation at the initial time, and obtaining the velocity potentials of each node on the solid boundary at the initial time, the velocity potentialderivatives of each node on the free surface boundary, the wave forces on the floating body and the displacement, velocity and acceleration of the floating body motion; according to the parameters ofeach node at the initial time, calculating the velocity potential of each node on the solid boundary at the next time, the velocity potential derivative of each node on the free surface boundary, thewave force on the floating body and the displacement, velocity and acceleration of the floating body motion. The present invention solves the problem of insufficient consideration of nonlinearity in the process of interaction between wave and structure in the prior art, and improves the calculation accuracy.

The embodiment of the invention provides a reservoir flow numerical simulation method and system after heterogeneous fracturing. The method comprises the following steps: obtaining a discrete fracturenetwork after heterogeneous fracturing and a transformation area reservoir range; dividing the boundary of the discrete fracture network and the reservoir into a plurality of fracture micro-elementsand a plurality of boundary units; converting the flowing differential equation of the reservoir into a boundary integral equation of the corresponding reservoir, and solving to obtain a boundary element solution of the reservoir; coupling the discrete fracture flow equation and the reservoir boundary element solution to obtain a discrete fracture network-two-region flow coupling matrix; and performing flow numerical simulation on the reservoir according to the discrete fracture network-two-region flow coupling matrix. From the perspective of seepage mathematical model establishment, a fracturing fracture network formed by artificial fractures, induced fractures and natural fractures is extracted into a discrete fracture network-two-region heterogeneous conceptual model, and the discrete fracture network-two-region heterogeneous conceptual model can be used for simulating flow behaviors under different arbitrary reservoir two-region heterogeneous forms and arbitrary fracture network distribution combinations.

The invention discloses a plate structure-sound field coupling analysis method. The method includes the steps that a finite element method and a radial point interpolation method are combined, and dispersing is conducted on a system kinetic equation of a plate structure; a boundary integral equation of a sound field domain is established according to a boundary element method; a structure-sound field coupling equation is established according to a dispersed system kinetic equation, the boundary integral equation and the structure-sound field coupling boundary condition. The invention further discloses a plate structure-sound field coupling analysis device corresponding to the plate structure-sound field coupling analysis method and a computing device with the plate structure-sound field coupling analysis device.

The invention discloses a method for establishing a three-dimensional percolation model of a volume fracturing horizontal well in a tight reservoir, which comprises the following steps of firstly establishing a three-dimensional percolation basic solution based on a boundary element method; establishing a point source physical model of a space of an infinite tight reservoir; establishing the mathematical model corresponding to the physical model of point source, solving the mathematical model to obtain the three-dimensional percolation basic solution; secondly, establishing the seepage model based on the basic solution of three-dimensional seepage; transforming the differential equation of regional seepage into the boundary integral equation; discreting the boundaries into finite-sized boundary elements; discreting the boundary integral equation on the boundary element; and writing the algebraic equation in the form of a matrix equation; depending on whether the boundary stress and flow rate are known, performing the corresponding operation. The invention has the advantages that the three-dimensional seepage flow model is obtained, the influence of the intersection of different fractures and the stress sensitivity of the reservoir is considered, and the influence of the complex fracturing network on the seepage flow can be more truly simulated.

The invention discloses a method for no-reference quantitative inspection of panel thinning defect based on Lamb wave. The method comprises the following steps: solving a coefficient of the required Lamb wave reflection modal; solving a green function in a zero-defect panel; constructing a boundary integral equation by use of the dynamics reciprocal theory and far-field basic solution; substituting a reflection coefficient into the boundary integral equation and performing inverse Fourier transform to finally obtain a defect expression; and reconstructing the defect position and shape in the panel. In the invention, the problems of quantitative inspection of panel thinning defect are effectively solved, the panel defect is reconstructed by directly using the reflection information of Lamb wave without referring to any condition in advance, and an efficient and accurate method is provided for engineering quantitative detection.

The invention discloses a no-reference SH wave guide method used for flat plate thinning defect quantitative detection. Defect reconstruction is conducted on a flat plate by means of no-reference SH wave guide, and the specific position and shape of a defect are given. The method includes the steps that mode separation is conducted on a total field, and a reflection coefficient of a required SH wave guide mode is obtained; a green function in the no-defect flat plate is solved, and a approximate solution of a far field is obtained; a boundary integral equation is solved, and the shape of the defect in the flat plate is reconstructed in a no-reference mode. The method relates to a quantitative detection technology, people do not need to refer to the approximate position of the defect in advance, a defect expression is directly induced theoretically, a whole component can be detected at a time, an efficient and precise scheme is provided for ultrasonic wave guide quantitative detection, the method has important application value in engineering, and a whole structure can be detected at a time. Detection can be conducted without removing coating and insulating layers, and complex rotating and walking devices are not needed. Defect sensitivity and precision are high, energy consumption is low, and the method is economical.

An object of the present invention is to provide a boundary element analytic method and a boundary element analytic program, which are capable of coping with the problem of diversity in symmetric property to be encountered when carrying out an analytic operation by taking advantage of the symmetric property of a subject to be analyzed, and thus providing an efficient analysis.

Various types of data for the use in the boundary element analysis, which have been previously input at step S101, are stored at step S102. To carry out this operation, at least boundary element definition information for defining a boundary element in the subject to be analyzed and state quantity information in which boundary element identification information for identifying the defined boundary element is associated with the boundary element for each state quantity thereof. At step 103, the input different types of data are used to generate a digitized boundary integral equation with a boundary value at a point of element on each defined boundary element taken as a variable. Then, at step S104, the generated boundary integral equation is assigned with the input boundary condition to sort out any unknowns, thus obtaining the simultaneous equations. The obtained simultaneous equations are then solved to determine respective values for the unknowns.

The invention discloses a boundary condition setting method for processing irregular frequency in ship hydrodynamic calculation, and relates to the field of ship hydrodynamic calculation. The method comprises the following steps: acquiring three unit correspondence relationships enabling the distance between every two subunits in a hull wet surface grid unit, a first-layer cover grid unit, a second-layer cover grid unit and a third-layer cover grid unit which are adjacent to a hull waterline to be minimumbased on the three-dimensional hydroelasticity equations of the hull and the three-dimensional boundary element method. expanding a boundary integral equation by adopting a method of scaling and assigning boundary conditions on the layered cover grid units, so so to further solve the radiation potential source intensity and diffraction potential source intensity of the hull wet surface grid units and the cover grid units in the waterline plane. The sudden change problem of boundary conditions of hull wet surface grids and capping grids is solved; the application of the irregular frequency elimination method in ship hydrodynamic force calculation is achieved.