Papers by Keyword: Boundary Element Method (BEM)

Abstract: When the bubble moves in the vicinity of a free surface, the movement will be affected by the buoyancy and the Bjerknes effect. Blake and Gibson proposed the criterion which determined the motion direction of the jet and the dynamics of bubble. They proposed the jet wouldn’t be formed in the condition that . Based on the potential flow theory, boundary element method (BEM) is used to calculate three typical examples in this paper in order to study the dynamics of the bubble under the combined action of the Bjerknes effect of the free surface and the buoyancy. It is found out during the analysis that the Blake criterion is applicable to predict the conditions that and .

Abstract: Based on simulation and test, a method for engine acoustical source characteristic extraction and acoustic optimization was presented. The intake noise of engine of commercial bus with four different acoustical loads was measured and the characteristic of the noise was extracted using the four-load method. The values of intake noise calculated by BEM were compared with the values measured in the vehicle intake noise test. The comparison result showed that the simulation values agreed with the experimental ones at most of the range which indicated that the extracted result was reliable. The anechoic frequency was determined by analyzing the intake noise spectrum measured in the vehicle intake noise test. Finally, an effective scheme adding a Helmholtz resonator and a quarter wave tube was proposed by simulation, applied to the real vehicle and verified in the test. The acoustic performance of the intake system was improved significantly.

Abstract: Control problems are considered for a two-dimensional model describing wave scattering in an unbounded homogenous medium containing an impenetrable covered (cloaked) boundary. The control is a surface impedance which enters the boundary condition as a coefficient. The solvability of the original scattering problem for 2-D Helmholtz equation and of the control problem is proved. Optimality system dгescribing the necessary extremum conditions are derived. The algorithm for numerical solving of the control problem based on the optimality system and boundary element method is designed.

Abstract: Using the Laplace transform and freezing time variable, the problem in the time domain into the frequency domain to solve the problem. The establishment of a crack unit model in the frequency domain, and the boundary integral equation and discrete form containing the crack unit has been deduced. While using Durbin algorithm suitable for transient dynamic response of the inverse Laplace transform, the amount of stress intensity factor of a set of transformation parameters corresponding to the frequency domain into a time domain to obtain the dynamic stress intensity factor of time curve, and calculate the stress intensity factor compared to the boundary finite element method has a Laplace transform high precision, easy to save CPU time and data preparation features, we recommend using this method to calculate the dynamic stress intensity factor.

Abstract: This paper presents a state-of-the-art in the use of localized Lagrange multipliers (LLMs)for 3D frictional contact problems coupling the Finite Element Method (FEM) and the BoundaryElement Method (BEM). Resolution methods for the contact problem between non-matching mesheshave traditionally been based on a direct coupling of the contacting solids using classical Lagrangemultipliers. These methods tend to generate strongly coupled systems that require a deep knowledgeof the discretization characteristics on each side of the contact zone complicating the process ofmixing different numerical techniques. In this work a displacement contact frame is inserted betweenthe FE and BE interface meshes, discretized and finally connected to the contacting substructuresusing LLMs collocated at the mesh-interface nodes. This methodology will provide a partitionedformulation which preserves software modularity and facilitates the connection of non-matching FEand BE meshes.

Abstract: Relations between different solutions of an interface crack in a neighborhood of the crack tip given by the open model, frictionless and frictional contact models of interface cracks are analyzed numerically for a penny-shaped interface crack subjected to remote tension. A new analytic expression for the size of the near-tip contact zone in presence of Coulomb friction between crack faces is proposed in the so-called case of the contact zone field embedded in the oscillatory field.

Abstract: Wear is present in all mechanical interface interaction problems –contact, fretting, orrolling-contact–, and it is one of the main reasons for inoperability in mechanical components. Thepresented work is a review of recent research carried out by the authors [1, 2, 3]. A boundary-element-based methodology to compute anisotropic wear on 3D contact, fretting, or rolling-contact conditionsis presented. Damage on the geometries of the solids and the contact pressures evolution under or-thotropic tribological properties can be predicted using this contact framework, where the formulationuses the Boundary Element Method to compute the elastic inuence coefcients. Contact problem isbased on an Augmented Lagrangian formulation, and restrictions fullment is established by a set ofprojection functions. The boundary element anisotropic wear formulation presented is illustrated withsome examples, in which some studies about the inuence of anisotropic wear on contact variablesevolution are shown.

Abstract: The boundary element method was introduced to calculate the thermal resistance between pipe outside surface and the borehole inner surface of vertical U-shaped pipe underground heat exchanger. The effects of U-tube diameter, borehole diameter and tube spacing on the thermal resistance were also discussed. The results showed that it took only 10 min to complete a simulation of an underground heat pump running continually for 1000 h, which took least 3 h to complete the same cycle through finite volume method. When the thermal conductivity λ of the backfill material was 1.8 W/m²·K, the thermal resistance of the U-shaped pipe decreased with the increase in the tube spacing, it decreased with the increase in the U-tube diameter, however, it increased when the borehole diameter increased.

Abstract: Isogeometric finite element methods and more recently boundary element methods have been successfully applied to problems in mechanical engineering and have led to an increased accuracy and a reduction in simulation effort. Isogeometric boundary element methods have great potential for the simulation of problems in geomechanics, especially tunneling because an infinite domain can be considered without truncation. In this paper we discuss the implementation of the method in the research software BEFE++. Based on an example of a spherical excavation we show that a significant reduction in the number of parameters for describing the excavation boundary as well as an improved quality of the results can be obtained.

Abstract: The boundary element method , combined with the least squares method is proposed to determine the anisotropic elastic plane Laurent series of coefficients a boundary element method of least squares . This method sets the boundary element method and Laurent series method is a long one, not only high accuracy, while access to the plane problem abundance analytical solutions to the infinite domain oval hole of stress concentration problems as an example, the results of the calculation results with the analytical solution compared to illustrate the method is to solve the proble of elastic plane an effective way .