The Research of Simulation on Eddy Current Separation Process Based on MATLAB and COMSOL

AbstractThe separation process of eddy current separator is effected by the structure parameters of magnetic roller, the working parameters of the separator and some parameters of the scrap metal, such as the material, the shape, the size and so on. This is a complex process of electric field and magnetic field coupling. During this process, the sorting function of separator is powered by the existence of the eddy current power in waste particles, and the separation effect is directly determined by the flying distance of the scrap metal in the separation process. This paper armed for studying the eddy current power and the flying distance of the waste particles in separation to realize the simulation of the separation process. The eddy current force was obtained by the finite element analysis of the magnetic roller based on COMSOL, and the flying distance was got by the joint simulation of COMSOL and MATLAB

Iteratively solving a kind of signorini transmission problem in a unbounded domain

In this paper, we are concerned with a kind of Signorini transmission problem in a unbounded domain. A variational inequality is derived when discretizing this problem by coupled FEM-BEM. To solve such variational inequality, an iterative method, which can be viewed as a variant of the D-N alternative method, will be introduced. In the iterative method, the finite element part and the boundary element part can be solved independently. It will be shown that the convergence speed of this iteration is independent of the mesh size. Besides, a combination between this method and the steepest descent method is also discussed

A Coupling of Local Discontinuous Galerkin and Natural Boundary Element Method for Exterior Problems

National Natural Science Foundation of China [11101368, 10531080, 11001168, 61075120]; Education Department of Zhejiang Province [Y200908907, Y201121696]; Fundamental Research Funds for the Central Universities of China [860360]In this paper, we apply the coupling of local discontinuous Galerkin (LDG) and natural boundary element method(NBEM) to solve a two-dimensional exterior problem. As a consequence, the main features of LDG and NBEM are maintained and hence the coupled approach benefits from the advantages of both methods. Referring to Gatica et al. (Math. Comput. 79(271):1369-1394, 2010), we employ LDG subspaces whose functions are continuous on the coupling boundary. In this way, the primitive variables become the only boundary unknown, and hence the total number of unknown functions is reduced. We prove the stability of the new discrete scheme and derive an a priori error estimate in the energy norm. Some numerical examples conforming the theoretical results are provided

Extrapolation methods to compute hypersingular integral in boundary element methods

National Natural Science Foundation of China [11101247, 11201209, 11101317]; Shandong Provincial Natural Science Foundation of China [ZR2011AQ020]; Shandong Province Higher Educational Science and Technology Program [J11LE08]; National Basic Research Program of China [2005CB321701]; Reward Fund of CAS for National PrizeThe composite trapezoidal rule for the computation of Hadamard finite-part integrals in boundary element methods with the hypersingular kernel 1/sin(2)(x - s) is discussed, and the main part of the asymptotic expansion of error function is obtained. Based on the main part of the asymptotic expansion, a series is constructed to approach the singular point. An extrapolation algorithm is presented and the convergence rate is proved. Some numerical results are also presented to confirm the theoretical results and show the efficiency of the algorithms

A Domain Decomposition Method Based on Natural BEM and Mixed FEM for Stationary Stokes Equations on Unbounded Domains

In this paper, a new domain decomposition method is suggested for the stationary Stokes equations on unbounded domain and its convergence is proved. We draw an artificial boundary to make the domain into two parts: one is bounded, in which we use the mixed finite element method; the other is unbounded, in which we apply the natural boundary reduction. Then we change the sub-problem on the unbounded domain onto a one in a bounded domain and we use the Dirichlet to Neumann(DtN) alternating algorithm to solve the resulting mixed system. The theoretical results as well as the numerical examples show that this method is very effective especially for problems over unbounded domains.National Natural Science Foundation of China [11001168, 11101368, 11201209]; Scientific Research Projects of Zhejing Province Educational Department of China [Y200908907]; Reward Fund of Chinese Academy of Sciences for National Prize Winner; Fundamental Research Funds for the Central Universities of China [lzujbky-2010-168

Effect of compressibility on the small-scale structures in hypersonic turbulent boundary layer

The effects of the wall temperature and local compressibility on the small-scale structures, local flow topology, and enstrophy production in the hypersonic turbulent boundary layer are numerically investigated. The colder wall temperature significantly enhances the unstable topologies and non-focal topologies near the wall, mainly due to stronger compressibility and more sheet-like structures. The eigenvalue decomposition of the strain rate tensor is introduced to investigate the mechanism of the enstrophy production and small-scale structures. It is shown that in the near wall region, the enstrophy production is mainly governed by the intermediate eigenvalue of strain-rate tensor through flow topologies unstable node/saddle/saddle (UN/S/S), stable focus/stretching (SFS), unstable focus/stretching, and unstable node/unstable node/unstable node, while the enstrophy destruction is primarily contributed by the intermediate eigenvalue through flow topologies stable node/saddle/saddle, stable focus/compressing (SFC), and stable node/stable node/stable node. Moreover, in the far wall region, the third eigenvalue in flow topology SFS and the intermediate eigenvalue in UN/S/S make major contributions to the enstrophy production, while the first eigenvalue in flow topologies unstable focus/compressing and SFC, and the intermediate eigenvalue in SFC mainly lead to the enstrophy destruction.& nbsp;Published under an exclusive license by AIP Publishing