粘性流动的涡旋传输方程的一般表达式及其在任意曲线座标系中时展开式

It is well known that generally there are two ways to solve the problems of viscous flow in a turbomachine. One is to solve the Navier—Stokes equation (N-S) directly, and the other is to solve the equation of vorticity—transmission (V-T), However,even though the V-T equation is given out, it can only be used to solve a laminar flow problems,Therefore it is necessary to derive from it a general expansion of the time—average form for a turbulent flow. In this paper, a general V-T equation in vector form has been derived in a     

Effect of electromagnetic force on turbulent flow of molten metal in aluminum electrolysis cells

The standard κ-ε model was adopted to simulate the flow field of molten metal in three aluminum electrolysis cells with different anode risers. The Hartman number, Reynolds number and the turbulent Reynolds number of molten metal were calculated quantitatively. The turbulent Reynolds number is in the order of 10^3 , and Reynolds number is in the order of 104 if taking the depth of molten metal as the characteristic length. The results show that the molten metal flow is the turbulence of high Reynolds number, the turbulent Reynolds number is more appropriate than Reynolds number to be used to describe the turbulent characteristic of molten metal, and Hartman number displays very well that electromagnetic force inhibits turbulent motion of molten metal.     

Numerical Simulation of Methane Distribution and Sensor Placement in 2-Dimension Roadway

In order to provide a theoretical basis for methane sensor placement in the vertical direction of a tunnel, the software Fluent was used to simulate methane distribution. A geometric roadway model was established and divided by grids. Methane distribution in both level and vertical sections was simulated using a realizable k-ε model with the Fluent software according to a conservation equation in a turbulent state, a turbulent kinetic energy equation and a turbulent dissipation rate equation. The realizable k-ε model and the Fluent software were used to simulate methane distribution according to the principle of the conservation equation in a state of turbulent flow. The results show that after overflowing, a methane level with a certain thickness is formed. Methane density curves at three specific levels were internally consistent and methane density at higher levels is denser than that at lower levels. Methane distribution becomes thinner in the direction of wind and methane in the vertical direction becomes uniform if wind speed is high. The distance be- tween sensors and roof should be less than 300 mm which is in agreement with mine safety regulations.     

High performance parallel computing of large eddy simulation of the flow in a curved duct with square cross section

Large eddy simulation(LES) cooperated with a high performance parallel computing method is applied to simulate the flow in a curved duct with square cross section in the paper. The method consists of parallel domain decomposition of grids, creation of virtual diagonal bordered matrix, assembling of boundary matrix, parallel LDL^T decomposition, parallel solving of Poisson Equation, parallel estimation of convergence and so on. The parallel computing method can solve the problems that are difficult to solve using traditional serial compuling. Furthermore, existing microcnmputers can be fnlly used to resolve some large-scale problems of complex turbulent flow.     

On the Variational Problems of the Functionals with Derivatives of Higher Orders and Undetermined Boundary

According to the necessary condition of the functional taking the extremum, that is its first variation is equal to zero, the variational problems of the functionals for the undetermined boundary in the calculus of variations are researched, the functionals depend on single argument, arbitrary unknown functions and their derivatives of higher orders. A new view point is posed and demonstrated, i.e. when the first variation of the functional is equal to zero, all the variational terms are not independent to each other, and at least one of them is equal to zero. Some theorems and corollaries of the variational problems of the functionals are obtained.     

How to choose an appropriate transfer function in designing a simplest ANN to solve specific problems

How to irmrporate certain constraints known a prion into the transfer function to redure thenumber of hidden units of an MFNN in solving some specific probems is disussed. The N-bit parity andsymmetrical problems are used as examples and the derivation of the transfer function based on the a privriknowledge of the input patterns is given. It is shown that by use of the method proposed, only onc hiddenunit is needed in solving the parity and symmetry test problems.     

A novel hybrid FEM-BEM method for 3D eddy current field calculation using current density J

To solve a large eddy current field is one of the most difficult problems in the numerical computation of electromagnetic field. For this purpose, currently, the FEM and the BEM are widely used. The former is good at dealing with the close regions, nonlinearity and complicated mediums and the latter is fit to solve the problems of open regions and linearity. However, for complicated eddy current field problems in electrical engineering, either the FEM or the BEM is not successful. Therefo…     

Analysis of metropolis parking problems and solutions based on GIS

The rapid development of the social economy strongly promotes the urbanization and motorization.Meanwhile,parking problems become serious due to the long-term imbalance between parking demands and facility constructions.Thus there is an increasing urgency in finding solutions for parking problems.Based on the methodology framework of geographic information system(GIS),the metropolis parking problems are discussed in this paper.The characteristics of parking demand and the reasons for parking problems are investigated in detail.Then,the basic parking principle and strategies for solving parking problems are suggested with the example of Beijing.The results are hoped to improve the parking environment in metropolis.     

A three-equation turbulence model for high-speed flows

Adding a new equation to the two-equation K-turbulence model framework,this paper proposed a three-equation turbulence model to determine the density variance for high-speed aero-optics and high-speed compressible turbulent flows.Simulations were performed with the new model for supersonic and hypersonic flat-plate turbulent boundary layer and hypersonic ramp flows.The results showed that the prediction with the present model agrees well with the experimental data and is significantly better than the Lutz’s model in predicting the density variance for the flat-plate flows.Furthermore,the present model can produce more accurate skin pressure and skin heat flux distributions than the original K-model in simulating hypersonic compression ramp flows with separation and reattachment and shock/boundary layer interactions.Without introducing a variety of ad hoc wall damping and wall-reflection terms,the proposed three-equation turbulence model is applicable to highspeed aero-optics and turbulent flows of real vehicles of complex configuration.     

New Variational Solution for the Space Contact Problem

In the recent thirty years,a great of investigations have been made in the Wiener-Hopf equations and variational inequalities as two mutually independent problems.In this paper,we investigate the equivalence of the solution of variational inequality and the inversion of the Toeplitz operator when the projection operators P,Q are linear.The solution of general Wiener-Hopf equation is concluded as the solution of a variational problem.Thus an approximation method of obtaining the maximum value by variational is proposed to obtain the approximation of general Wiener-Hopf equation and apply it to the space contact problems in the elasticity theory.Especially,the solution representation is given in case that the projection of contact surface is round.The closing-form solution is also given when the known displacement is a polynomial of even power.     

Hybrid particle swarm optimization with chaotic search for solving integer and mixed integer programming problems

A novel chaotic search method is proposed,and a hybrid algorithm combining particle swarm optimization（PSO） with this new method,called CLSPSO,is put forward to solve 14 integer and mixed integer programming problems.The performances of CLSPSO are compared with those of other five hybrid algorithms combining PSO with chaotic search methods.Experimental results indicate that in terms of robustness and final convergence speed,CLSPSO is better than other five algorithms in solving many of these problems.Furthermore,CLSPSO exhibits good performance in solving two high-dimensional problems,and it finds better solutions than the known ones.A performance index（PI） is introduced to fairly compare the above six algorithms,and the obtained values of（PI） in three cases demonstrate that CLSPSO is superior to all the other five algorithms under the same conditions.     

Numerical simulation of gas-liquid two-phase jet flow in air-bubble generator

Air-bubble generator is the key part of the self-inspiration type swirl flotation machines,whose flow field structure has a great effect on flotation.The multiphase volume of fluid(VOF),standard k-ε turbulent model and the SIMPLE method were chosen to simulate the present model;the first order upwind difference scheme was utilized to perform a discrete solution for momentum equation.The distributing law of the velocity,pressure,turbulent kinetic energy of every section along the flow direction of air-bubble generator was analyzed.The results indicate that the bubbles are heavily broken up in the middle cross section of throat sect and the entrance of diffuser sect along the flow direction,and the turbulent kinetic energy of diffuser sect is larger than the entrance of throat sect and mixing chamber.     

Study of Fussy Clustering of Engineering Geological Environment with GIS

Based on previous evaluating methods, a new method which combines GIS with Fussy Clustering algorithm is proposed and applied in evaluating the engineering geological environment of the research area of XuZHou City in this paper. By analyzing the characteristics and formation of engineering geological environment, the major problems are discussed, including stability of basement rock, sandy soil liquefaction and cultural stratum. According to effecting factors of these problems, the stability of every engineering geological problem in the worked area is classified into different classes. Then, the Fussy Clustering method is used in assessing all conditions of engineering geological environment. Finally, the evaluation is fulfilled in the whole studied area. The calculating result shows the method is feasible.     

A dynamic model with substructures for contact-impact analysis of flexible multibody systems

In the fields of science and engineering, many kinds of impact problems of flexible multi-body systems, such as impact of objects on a spacecraft and collision caused by locking of space-craft extension mechanisms, are frequently encountered. They are referred to as contact-impact problems when people are not interested in the local deformation close to contact points but in the transient dynamic response in contact-impact duration. It is necessary to investigate contact- impact dynamics of f…     

A new evolutionary algorithm for constrained optimization problems

To solve single-objective constrained optimization problems,a new population-based evolutionary algorithm with elite strategy(PEAES) is proposed with the concept of single and multi-objective optimization.Constrained functions are combined to be an objective function.During the evolutionary process,the current optimal solution is found and treated as the reference point to divide the population into three sub-populations:one feasible and two infeasible ones.Different evolutionary operations of single or multi-objective optimization are respectively performed in each sub-population with elite strategy.Thirteen famous benchmark functions are selected to evaluate the performance of PEAES in comparison of other three optimization methods.The results show the proposed method is valid in efficiency,precision and probability for solving single-objective constrained optimization problems.     

Analysis of solid particle clusters in coherent structures of turbulent channel flow

A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures.The fluid phase is calculated by large eddy simulation and particles are tracked using Lagrangian trajectory method.The flow Reynolds number is 180 based on the friction velocity and half-width of the channel.The particle is lycopodium with St=0.93which may well follow the fluid phase.The mean and fluctuating velocities of both two phases are obtained,which are in good agreement with previous data.The strongest accumulations of particles in low-speed streak structures are observed at y+=11.3.Moreover,once particles are captured in low-speed streaks,most of them will reside there for a long period.Particles clustered in low-speed streaks obtain smaller instantaneous wall-normal and spanwise velocities than those out of there,which induce a larger particle flux into low-speed streaks than that out of there.The study is important for understanding particle dispersion mechanisms in gas-particle turbulent channel flows.     

Explicit formulation of the J_2-integral in anisotropic materials and its application in microcrack shielding problems

The explicit formulation of the J2-integral in anisotropic bodies and its application in microcrack shielding problems are discussed. With analytical treatments and numerical examinations, it is proved that there is a redistribution law for the remote J-integral in a discrete model of microcrack shielding problems, i.e. the projected conservation law of the Jk-vector. In this law, the J2-integral which was disregarded by Herrmann (1981) is proved to be of the same significance as the J1-integral. It is also concluded that the two energy dissipative processes due to the mi crocrack damage, i. e. the reduction in the effective moduli and the release of residual stresses, can be described by using the dissipation of the remote J-integral spreading across the microcrack damage zone.     

Robust Topology Optimization of Vehicle Suspension Control Arm

A robust topology optimization design framework is developed to solve lightweight structural design problems under uncertain conditions. To enhance the calculation accuracy and flexibility of the statistical moments of robust analysis, number theory integral method is applied to sample point selection and weight assignment. Both the structure topology optimization and number theory integral methods are combined to form a new robust topology optimization method. A suspension control arm problem is provided as a demonstration of robust topology optimization methods under loading uncertainties. Based on the results of deterministic and robust topology optimization, it is demonstrated that the proposed robust topology optimization method can produce a more robust design than that obtained by deterministic topology optimization. It is also found that this new approach is easy to apply in the existing commercial topology optimization software and thus feasible in practical engineering problems.     

Experimental and numerical study on the flapping motion of submerged turbulent plane jet

A submerged,vertical turbulent plane water jet impinging onto a free surface will be self-excited into a flapping oscillation when the jet velocity,leaving the jet orifice,exceeds a critical value.The flapping phenomenon was verified simultaneously in this paper by laser Doppler velocimeter measurement and numerical analyses with volume of fluid approach coupled with a large eddy simulation turbulent model.The general agreement of mean velocities between numerical predictions and experimental results in self-similar region is good for two cases:Reynolds numbers 2090 and 2970,which correspond to the stable impinging jet and flapping jet.Results show that the flapping jet is a new flow pattern for submerged turbulent plane jets with characteristic flapping frequency,and that the decay of the mean velocity along the jet centerline is considerably faster than that of the stable impinging state.