109 results about "Robin boundary condition" patented technology

Systems and methods of simulating an explosion in time-marching finite element analysis are disclosed in the present invention. According to one aspect, a method is configured for increasing user (e.g., engineer or scientist) productivity by reducing computation time of simulating fluid-structure interaction due to an explosion. The method comprises a creation of a finite element analysis model that includes structure, surrounding fluid, a blast source of the explosion and a single layer of ambient elements each having a segment representing a boundary of the fluid facing the blast source. Each ambient element is associated with a particular finite element representing the fluid at the boundary. The ambient elements are configured to be situated between the blast source and the structure such that the simulation can be carried on a set of boundary conditions specified thereon. The boundary conditions comprise a set of nodal velocities that are determined from the empirical formula (e.g., Friedlander equation).

The invention discloses a structural dynamical model modification-based prestress recognition method, and relates to the prestress recognition of pre-tensioning structures. The method comprises the following steps: establishing a finite element model of a structure; converting the boundary condition such as clamped support or simple support into spring support in three or two directions, and applying an axial prestress at the same time; calculating a fixed frequency and a fixed vibration mode of the structure through commercial finite element software; carrying out test and recognition by utilizing a test modal analysis technology, so as to obtain the fixed frequency and the fixed vibration mode of the structure; and recognizing the spring support rigidity and prestress of the boundary at the same time on the basis of a model modification technology. The method is simple, high in recognition precision and convenient to operate; and through considering the influences of the boundary condition, the reliability is high. By taking MAC as a target function, the completeness of the test data is supplemented; the optimization through a genetic algorithm is more beneficial for obtaining the globally optimal solution; and the whole modification model can be automatically driven to carry out solving.

The invention relates to an interplanetary low-thrust transfer orbit design method based on polynomial approximation. Firstly, variable initial value guess is designed, the initial value guess of the transfer orbit design is given, then, the beginning and tail end boundary conditions of a detector are calculated, next, a second type Chebyshev polynomial is adopted for fitting the transfer orbit of the detector, the performance indexes and the constrained conditions are calculated, finally, whether the feasibility conditions are met or not is judged according to the calculated thrust restriction in accordance with whether the calculated performance indexes meet the optimum conditions or not, if all requirements are met, the optimization is successful, the optimum transfer orbit is obtained, and if one requirement is not met, the initial value guess of the design variable in the first step is regulated until the optimization is successful. The method utilizes the Chebyshev polynomial for approximating the low-thrust transfer orbit shape, the time is used as the independent variable, and the flight time restriction is avoided. The polynomial factor is determined through the beginning and tail end orbit state restriction of the detector, and the method has the advantage that the fast design on the low-thrust transfer orbits in different task types can be realized according to the given beginning and tail end boundary conditions.

Embodiments of the present invention provide a heterogeneous cluster system for CFD simulation calculation and a CFD calculation method. The heterogeneous cluster system for CFD simulation calculation comprises a central processing unit (CPU) and a hardware accelerator. The CPU is configured to divide the received CFD task into task blocks, according to the attribute of the CFD task, the CFD boundary condition and the performance parameter of the hardware accelerator, determine the hardware accelerator for calculating the task blocks, and transmit the task blocks to the hardware accelerator; and the hardware accelerator is configured to receive and calculate task blocks transmitted by the CPU and transmit the calculation result to the CPU. According to the technical scheme of the embodiments of the present invention, by constructing the heterogeneous cluster system integrating the CPU, the GPU and the FPGA, calculation resources are intelligently deployed according to the attribute of the CFD task, so that the bottleneck problem of CFD simulation calculation is solved and the running efficiency of the CFD application is improved.

The invention discloses an anomalous diffusion simulation method based on a discrete fraction order difference. The anomalous diffusion simulation method based on the discrete fraction order difference includes: using a one dimension classical diffusion equation for describing a diffusion phenomenon; defining the discrete fraction order difference, using the discrete fraction order difference to discretize the one dimension classical diffusion equation, and performing numerical simulation according to initial boundary conditions. Compared with a diffusion model built by using a classical fraction order diffusion equation, a diffusion model built by using the anomalous diffusion simulation method based on the discrete fraction order difference is concise in expression, and convenient and fast in numerical simulation on the premise of maintaining discrete memory effects.

The invention discloses a medium rough surface finite element electromagnetic simulation method based on integral boundary. The medium rough surface finite element electromagnetic simulation method based on the integral boundary mainly solves the problem that similarity of inhomogeneous media and approximate absorbing boundary are difficult to solve by integral equation class methods. The medium rough surface finite element electromagnetic simulation method based on the integral boundary comprises the achieving steps of using a monte carlo method for obtaining a medium rough surface, carrying out truncation processing and scattering on the medium rough surface through an artificial boundary, acquiring a finite element equation of a simulation area according to a functional method inside the simulation area, using an integral equation method for obtaining integral boundary conditions outside the simulation area, forming an electromagnetic coupled equation through continuous conditions, and finally obtaining radar scattering parameters of the medium rough surface by solving an electromagnetic coupled matrix equation. Compared with the prior art, the medium rough surface finite element electromagnetic simulation method based on the integral boundary can be more easily used for simulating inhomogeneous medium electromagnetic problems than the integral equation class methods, can improve electromagnetic simulation precision compared with the approximate absorbing boundary, and can be used for acquiring the electromagnetic scattering parameters of medium rough surface unbounded area problems.

The invention discloses a forward computation method of a motion equation of an elastic wave on a relief surface, relating to the field of processing and explanation of the seismic exploration data of oil seismic exploration. The forward computation method comprises the following steps of: converting an irregular computational domain into a regular computational domain under a new coordinate system by utilizing longitudinal coordinate transformation; educing a free boundary condition under the new coordinate system on the basis of a zero-traction free boundary; and computing a seismic wave field positioned on the free boundary by adopting an implicit difference scheme. The forward computation method can process complex terrains, is adapted to the surface relief, also enhances the computing efficiency and can better implement the free boundary condition.

The invention belongs to the technical field of grid computation, and specifically relates to a grid boundary condition processing method of unstructured grid CFD computation. The method comprises the following steps: establishing grid information; defining a boundary type; extracting grid outer boundary information; realizing the matching of a first node through a method of exhaustion; matching the remaining nodes in a wave front form; matching a boundary surface unit; and assigning a boundary condition. According to the method, a method for rapidly matching between unstructured boundary surfaces and grid surfaces is utilized, so that the grid boundary conditions of unstructured grids in Tecplot form can be rapidly mapped to corresponding boundary surfaces of infield body grids, the rapid processing of boundary condition information of the unstructured grids can be realized and the computer time can be effectively decreased.

The invention discloses a new submodel finite element analysis method based on cutting boundary deformation constraint. The content of the method comprises: building a complete machine simplified model, analyzing; carrying out postprocessing to cutting boundary nodes of the complete machine model; building a finite element model-a submodel of a partial structure; adding a deformation coupling constraint equation to the cutting boundary of the submodel, adding a displacement interpolation boundary condition and a force boundary condition; analyzing the submodel; and checking that the distance from a cutting boundary to a stress gathered region is far enough. The method of the invention is advantaged by that when applying the boundary conditions to the cutting boundary of the submodel, the displacement interpolation boundary condition is added to one part of the cutting boundary, the constraint equation and the force boundary condition are added to the other part; the accuracy of the boundary conditions of the submodel is ensured; compared with the traditional submodel finite element analysis method, in adoption of the new submodel finite element analysis method, the demand of the complete machine model is reduced; the complete machine model is greatly simplified; and the complete machine analysis efficiency and the calculation precision of the submodel are improved.

The invention discloses an Invar steel PMIG weaving welding temperature field and a deformation simulation method.A thermal-mechanical coupling model used for analyzing an Invar steel thick plate temperature field and a stress strain field; through reasonably setting welding technology parameters, a swinging route and pre-deformation, the established coupling model is solved and calculated by the utilization of related finite element analysis software, the Invar steel temperature field and strain field distribution and deformation conditions under the corresponding welding technology parameters are obtained through loading and solving thermal boundary conditions and mechanical boundary conditions, and then the welding technology is instructed and optimized.

The invention belongs to the technical field of reactive voltage control of a power grid, in particular relates to a layered and zoned reactive voltage analysis method based on a boundary condition. The layered and zoned reactive voltage analysis method comprises the following steps of making the power grid layered and zoned; determining a researched zone and a boundary thereof; inputting maximum daily load, minimum daily load, output of a power generator, the boundary condition, a reactive compensation configuration condition and a limit value of a regional power grid; carrying out power flow calculation, adjusting reactive compensation capacity, and adjusting the boundary of the regional power grid to the boundary condition; judging whether an out-of-limit situation exists in the voltage in a region or not; and judging whether a power factor of each main transformer conforms to the stipulation of the limit value or not. According to the layered and zoned reactive voltage analysis method, reactive voltage correction and reactive voltage optimization can be fulfilled, the reactive voltage analysis efficiency of a large-sized power grid can be substantially improved, focused analysis can be conducted with regard to a local power grid, and the layered and zoned reactive voltage analysis method is suitably used for situations with relatively complete data of the local power grid and insufficient data of a large power grid; and the layered and zoned reactive voltage analysis method is easy to understand and implement, is proximate to actual running of the power grid, and is suitably for on-line application.

The invention aims to provide a method for analyzing vibration in a structural surface of a rectangular plate under a non-uniform elastic constrained boundary condition. The method comprises the following steps: adopting Fourier series for unfolding the rigidity of a constraining linear spring in a non-uniform plane; adopting an energy principle for describing the vibration in the structural surface of the rectangular plate; applying a load in the plane at any acting angles to the structure of the rectangular plate; establishing the vibration displacement boundary smooth series in the structural surface of the rectangular plate; solving the system of vibration linear equations in the structural surfaces of any non-uniform boundary rectangular plates, thereby acquiring the vibration in the structural surface of the rectangular plate and forcing to respond and admit. Compared with the traditional methods, such as, the finite element method, and the like, the method provided by the invention has the advantage that the operation for the nodes is not required for the processing of the boundary condition in a non-uniform plane, so that the time for modeling and calculating is greatly saved. A rigidity distribution function of the spring can be adjusted for realizing any classic boundary conditions, uniform elastic constrained boundary conditions and non-uniform elastic constrained boundary conditions.

The invention aims at providing a rigid cylinder vortex-induced vibration testing device capable of achieving nonlinear boundary conditions. The rigid cylinder vortex-induced vibration testing device comprises nonlinear springs, a vertical restraining mechanism, a cylinder model, a support, a clamp, a supporting frame and a data collecting and analyzing processing part. The data collecting and analyzing processing part is used for collecting and analyzing vibration data of the cylinder model. The vertical restraining mechanism is composed of box iron, a cardan joint, a bolt and an aluminum alloy pipe. The adopted cardan joint has the advantages of being small in damping and flexible in structure. The vertical restraining mechanism is used for enabling vibration of the cylinder model to be kept in the same horizontal plane. A nonlinear boundary cylinder system is jointly composed of the vertical restraining mechanism, the support and the nonlinear springs. The rigid cylinder vortex-induced vibration testing device can be applied to rigid cylinder vortex-induced vibration tests of a circulating water channel or a towing tank, and the vortex-induced vibration mechanism under nonlinear rigidity such as contact between a seabed suspended span pipe and the seabed can be truly simulated.

The invention relates to a formwork support system derivative design method. 1. Determine the boundary conditions and calculation steps of the formwork support system; 2, establish a parametric modelaccording to that boundary condition; 3, load and internal force calculation; 4. Checking the stress and displacement of the structure, outputting the calculation result to check whether it meets thedesign requirements; 5, count that engineering quantity of the design scheme; 6, upload that publishing program to the cloud; 7, compute various combinations according with that boundary conditions byusing the cloud computing capability, and obtaining thousands of design scheme; 8, arrange that statistical data of the project quantity according to the calculation result, and comparing and selecting the most design scheme. This method adopts the derivative design principle, according to the set boundary condition scope and the step distance request, compiles the program to construct the model,outputs the stress, the displacement and the project quantity statistical result, utilizes the cloud computing ability, has greatly improved the design efficiency, and reduced the engineering material, saves the cost.

A calculation method for checking ultimate strength of a fan underframe includes: using finite element analysis software as a platform for modeling, performing finite element meshing, setting connecting structure load and boundary conditions, and calculating to obtain stress condition of the underframe. The step of setting the connecting structure load and boundary conditions includes: establishing nodes at the center of a hub and at the center of a bearing, connecting the nodes through a three-dimensional beam unit, and simulating spindle transfer load. A central point of a main bearing block is connected with an inner ring surface unit of the main bearing through a link unit which bears only pressure. The method has the advantages that calculated stress of the underframe and calculated danger positions are more accurate and the actual stress relation of the underframe is satisfied.

The invention relates to an implementation method for a mixed absorbing boundary condition applied to a variable density acoustic wave equation. The implementation method comprises the steps of dividing a whole simulation region into an internal region and a boundary region, calculating the wave field value of a sound wave of each absorbing boundary layer by using the variable density acoustic wave equation and a variable density AWWE (Arbitrary Wide-angle wave equation) respectively, and performing linear weighting on the two calculation results to obtain the wave field value of the sound wave of each absorbing boundary layer. On the basis of realizing a single variable density AWWE absorbing boundary layer and in 2D (2 dimensional) and 3D (3 dimensional) space coordinate systems, the wave field value of the sound wave of each absorbing boundary layer is calculated by respectively adopting a combination mode of processing edges of the variable density AWWE and processing angles of a modified 15-degree one-way wave equation, and a combination mode of processing faces of the variable density AWWE, the processing edges of the modified 15-degree one-way wave equation and the processing angles of a 5-degree one-way wave equation, and the mixed absorbing boundary condition of the variable density AWWE is realized. The implementation method can be widely applied to the numerical simulation of constant density and variable density acoustic wave equations.

The present invention belongs to the technical field of numerical analysis of three-dimensional thermal analysis and relates to a three-dimensional finite element simulation method based on heat radiation boundary conditions. The method comprises: carrying out modeling on a device to be subjected to the thermal analysis, introducing radiation boundary conditions into the heat conduction problem, and obtaining the finite element weak form of the heat radiation boundary conditions by adopting the method of Galerkin residual weighting; using the tetrahedral meshed model to select the second-orderlaminated basis function and the discrete finite element weak form equation, obtaining a finite element matrix and aright-end vector by cooperating with the Newton-Raphson iteration method, and integrating the final equation; and finally, by using the scientific nonlinear convergence criteria, through continuous iteration, quickly and accurately obtaining final numerical results.

The invention discloses an immersed boundary implicit iterative solving method meeting no-slip boundary conditions and continuity conditions; the method mainly comprises the steps of using a viscous incompressible flow N-S control equation, expanding a momentum equation along a feature line to perform time discretization, using a finite element method to perform spatial discretization, and adding additional body force to the discretized control equation; using a direct force method to solve the additional body force so that interpolation speed on the boundary is equal to expected speed distribution; when a fractional step method is in use, dividing the additional body force into two parts according to whether it is coupled to pressure, and solving the two parts respectively; performing speed correction in iterative computation of the additional body force and pressure to obtain final flow field distribution. The problem of an existing immersed boundary method that no-slip boundary conditions and continuity conditions cannot be met at same time is solved; after the additional body force is divided into two parts, the cost of solving a component item uncoupled to the pressure is effectively reduced, and the computing efficiency of the immersed boundary method is improved.

The invention discloses a reverse time migration method of a carbonatite reservoir. By aiming at a phenomenon that a fracture-cavity pore construction of carbonatite is always companied with fracture and big-angle form distortion formed due to construction movement, the reverse time migration method is used for precisely depicting the carbonatite. A finite difference method is used for solving a wave equation to simulate a seismic wave field; a processing method for the wave field to transmit to a boundary adopts a PML (Perfectly Matched Layer) absorbing boundary condition; a seismic origin wave field recovery part adopts a reverse PML wave field recovery technology; and a calculation part adopts a GPU (Graphics Processing Unit) parallel acceleration technology. The PML absorbing boundary condition is adopted, so that the invention can more effectively eliminate boundary reflection interference than a random boundary condition; since the reverse PML wave field recovery technology is adopted, compared with a traditional wave field storage strategy, the invention can greatly reduce requirements on a storage amount on the premise that a calculated amount is not increased, a wave field recovery effect is good, amplitude fading is avoided, and operation efficiency is improved by adopting the GPU parallel acceleration technology.