基于有限体积模拟的模锻优化设计

在锻造等金属大变形的工艺设计中,相关参数的确定很大程度上依赖于经验公式,而有限元法在金属大变形过程数值模拟中有明显的局限性,且模拟结果难以验证。本文基于有限体积法模拟了一典型开式模锻过程,并在通用经验值允许的范围内,根据模拟结果调整工艺设计中的参数设置,有效避免了一种锻件常见缺陷。通过分析变形过程特定时段的变形区形状、分流面的变化及变形力分布曲线,结合相关塑性理论验证了模拟结果的正确性,实现了工艺优化设计。研究证明理论预测与数值模拟相“拟合”的方法可以代替实验用于指导生产实践。     

THE EFFECT OF OIL CAVITY DEPTH ON TEMPERATURE FIELD IN HEAVY HYDROSTATIC THRUST BEARING

For a heavy hydrostatic bearing with a high linear velocity,the results of numerical calculations often differ from practical conditions if the viscosity is considered as constant.In this article,the influence of the oil cavity depth on the temperature field in the heavy hydrostatic bearing is discussed in the context of variable viscosity.The viscosity-temperature relations for the gap oil film are first established by fitting B-Spline curves,then,numerical calculations for the temperature field in the heavy hydrostatic bearing of different oil cavity depths are carried out based on Finite Volume Method (FVM) under the same rotating speed,and the influence of the oil cavity depth on the temperature distribution in the gap oil film of the hydrostatic bearing is discussed.The results of numerical calculations provide the temperature distribution state inside the hydrostatic bearing,which would help the selection and the design of hydrostatic bearings in engineering practice.     

Numerical simulation of transport phenomena in continuous casting of steel plates with electromagnetic brake

The present work numerically investigates two-dimensional (2-D) solidification transport phenomena (EM-STP) during continuous casting (CC) process in the absence and the presence of static magnetic fields (SMFs), based on a unified numerical model. For the purpose of controlling vortexes, the electromagnetic brake (EMBR) effects of various SMFs under the given depth of submerged entry nozzle (SEN) and the same casting velocity V0 are investigated. ANSYS software is used to analyze the SMFs that applied to the EMCC process, and then a data-conversion program based on the principle of linear interpolation proposed previously is used to deal with the issue of data-format-matching between FEM and FVM. The simulation results indicate that, an appropriate SMF can effectively suppress the bulk liquid flow in CC-process of steel plate, and with increase of the intensity of applied magnetic fields, the vortexes become weaker and the oscillating amplitude of impinging jet decreases. Based on the knowledge gained from the EMCC-STP analysis and by comparing the results with the applied magnetic fields with those without magnetic fields, it is found that a SMF with |Bmax|=55×10-3 T can meet the need of braking, and consequently improve the quality of casting by reducing the penetration of non-metallic inclusions, as well as avoiding breakout, macro-segregation and crack ultimately.     

Thermal analysis in coated cutting tools

This work studies the heat influence in cutting tools considering the variation of the coating thickness and the heat flux. K10 and diamond tools substrate with TiN and Al₂O₃ coatings were used. The numerical methodology utilizes the ANSYS^® CFX software. Boundary conditions and constant thermo physical properties of the solids involved in the numerical analysis are known. To validate the proposed methodology an experiment is used. The TiN and Al₂O₃ coatings did not show satisfying results during a continuous cutting process. It showed a slight reduction in the heat flux for the 10 (µm) TiN and Al₂O₃ coatings.     

长方形截面通道内的充分发展对流换热问题的数值研究

利用FVM（有限容积法）研究了长方形截面通道内的充分发展对流换热问题，得出了壁温均匀下不同高、宽比长方形截面通道内流动与换热的充分发展区域的阻力系数及Nu数．数值研究结果表明，该方法可获得较准确的解，     

NONSTRUCTED GRID MESH FINITE VOLUME METHOD AND APPLICATION

Finite Volume Method (FVM) which can solve fluid problems effectively is used in this paper. Gauss theorem is used to transfer volume integration to area integration , by which the relation formula of the nodes around each element is founded based on the constancy of the flux into and out of the element. With that the discrete equations are obtained. This method with free cubic element is applied in 3D seepage and tidal flow problems. From the practice it can be found that seepage flux is more accurate than FEM and FVM also has the advantages of good stability, convenience of solving. easy programming, less computing time and storage.     

考虑涌潮作用的钱塘江二维泥沙输移数值模拟

钱塘江涌潮前后水位、流速和含沙量等物理量存在突变，给数值模拟带来了很大的困难，传统的数值模型往往不能准确模拟涌潮作用下的泥沙输移。在已建立的二维涌潮数值模型的基础上，应用基于准确Riemann解的Godunov格式建立了二维泥沙数值模型，模型首先检验了纯对流问题，然后模拟了钱塘江涌潮作用下的泥沙输移，计算结果反映了涌潮到达时刻含沙量的突变过程以及涌潮对泥沙输移的影响，揭示了钱塘江河口高含沙量区成因，以及涌潮是钱塘江河口大冲大淤的机理之一。     

Study on the fluid/structure interaction at different inlet pressures in molded packaging

This paper presents the computational study of fluid/structure interaction (FSI) analysis in the molding process using the Mesh-based parallel Code Coupling Interface (MpCCI) method with finite volume coding (FLUENT 6.3) and finite element coding (ABAQUS 6.9). The FSI analysis is implemented on the molded package during the encapsulation process with different inlet pressures. Real-time flow visualization, deformation and stress of the silicon die during the encapsulation process are presented in this paper. A fluctuation phenomenon of the silicon die is found in the encapsulation process when the inlet pressure increases. The maximum deformation during the process is determined at different locations on the silicon die, calculated during the final stage of the filling process. The deformation and stress of the die is exponentially increased with increasing inlet pressure. The maximum stress on the solder bump is concentrated near to the inlet gate. Thus, the present FSI analysis approach is expected to be a guideline or reference and provides better understanding of the encapsulation process for package design in the microelectronic industry.     

考虑环流横向输沙及河岸变形的平面二维扩展数学模型

本文考虑弯道环流输沙效应，在泥沙运动基本方程中增加了反映环流横向输沙附加项，对平面二维水沙数学模型的悬移质、推移质输沙方程和河床变形过程进行了扩展。借助土力学中关于边坡稳定性理论中的圆弧滑动法，并引入多杈树搜索方法，建立了适用于平面二维数学模型的河岸崩塌变形计算方法。经扩展后的平面二维水沙数学模型能模拟环流横向输沙及由其引起的河床冲淤和河岸变形，并应用该模型模拟了弯道发生、发展过程，计算结果与已有的认识是一致的。     

用通度系数法数值模拟水电站岔管水流

本文在有限体积法和ＳＩＭＰＬＥ算法中，引入通度系数的概念处理计算区域的不规则边界问题，并把通度系数的概念引入Ｋ－ε紊流模型中，推导了考虑通度系数的二维有限体积法的数值离散格式。以东江水电站一级洞贫管为例，计算了岔管内的流动特性。计算结果能真实地模拟中岔管内水流的流动规律，表明用通度系数法模拟岔管内的流动特性是行之有效的。