基于SGS模型的茶盘造型设计研究

为进一步拓展产品设计路径,基于管理学中的SGS(门径管理系统,Stage-Gate-System的简称)模型开发产品设计流程,面向用户需求展开SGS模型在产品设计中的应用。以茶盘造型的概念设计为例,结合SGS模型的产品开发方法,优化设计程序,从而解决茶具设计的适用性、美观性及安全性等问题,最终,通过导入SGS模型,提高了茶具设计的用户评价度,为同类产品的造型设计提供参考。

Evaluation of Subgrid-scale Models in Large-eddy Simulations of Turbulent Flow in a Centrifugal Pump Impeller

The current research of large eddy simulation （LES） of turbulent flow in pumps mainly concentrates in applying conventional subgrid-scale （SGS） model to simulate turbulent flow, which aims at obtaining the flow field in pump. The selection of SGS model is usually not considered seriously, so the accuracy and efficiency of the simulation cannot be ensured. Three SGS models including Smagorinsky-Lilly model, dynamic Smagorinsky model and dynamic mixed model are comparably studied by using the commercial CFD code Fluent combined with its user define function. The simulations are performed for the turbulent flow in a centrifugal pump impeller. The simulation results indicate that the mean flows predicted by the three SGS models agree well with the experimental data obtained from the test that detailed measurements of the flow inside the rotating passages of a six-bladed shrouded centrifugal pump impeller performed using particle image velocimetry （PIV） and laser Doppler velocimetry （LDV）. The comparable results show that dynamic mixed model gives the most accurate results for mean flow in the centrifugal pump impeller. The SGS stress of dynamic mixed model is decompose into the scale similar part and the eddy viscous part. The scale similar part of SGS stress plays a significant role in high curvature regions, such as the leading edge and training edge of pump blade. It is also found that the dynamic mixed model is more adaptive to compute turbulence in the pump impeller. The research results presented is useful to improve the computational accuracy and efficiency of LES for centrifugal pumps, and provide important reference for carrying out simulation in similar fluid machineries.

Applying resolved-scale linearly forced isotropic turbulence in rational subgrid-scale modeling

In previous attempts of rational subgrid-scale (SGS) modeling by employing the Kolmogorov equation of filtered (KEF) quantities, it was necessary to assume that the resolved-scale second-order structure function is stationary. Forced isotropic turbulence is often used as a framework for establishing and validating such SGS models based on stationary restrictions, for it generates statistical stationary samples. However, traditional forcing method at low wavenumbers cannot provide an analytic form of forcing term for a complete KEF in physical space, which has been illustrated to be essential in the modeling of such SGS models. Thus, an alternative forcing method giving an analytic forcing term in physical space is needed for rational SGS modeling. Giving an analytic linear driving term in physical space, linearly forced isotropic turbulence should be considered an ideal theoretical framework for rational SGS modeling. In this paper, we demonstrate the feasibility of establishing a rational SGS model with stationary restriction based on linearly forced isotropic turbulence. The performance of this rational SGS model is validated. We, therefore, propose the use of linearly forced isotropic turbulence as a complement to free-decaying isotropic turbulence and low-wavenumber forced isotropic turbulence for SGS model validations.

Mathematical Constraints in Multiscale Subgrid-Scale Modeling of Nonlinear Systems

To shed light on the subgrid-seale （SGS） modeling methodology of nonlinear systems such as the Navier-Stokes turbulence, we define the concepts of assumption and restriction in the modeling procedure, which are shown by generalized derivation of three general mathematical constraints for different combinations of restrictions. These constraints are verified numerically in a one-dimensional nonlinear advection equation. This study is expected to inspire future research on the SGS modeling methodology of nonlinear systems.

A SECOND-ORDER DYNAMIC SUBGRID-SCALE STRESS MODEL

A second-order dynamic model based on the general relation between the subgrid-scale stress and the velocity gradient tensors was proposed. A priori test of the second-order model was made using moderate resolution direct numerical simulation date at high Reynolds number ( Taylor microscale Reynolds number R-lambda = 102 similar to 216) for homogeneous, isotropic forced flow, decaying flow, and homogeneous rotating flow. Numerical testing shows that the second-order dynamic model significantly improves the correlation coefficient when compared to the first-order dynamic models.

Stochastic modeling of subgrid-scale effects on particle motion in forced isotropic turbulence

The subgrid-scale effects on particle motion were investigated in forced isotropic turbulence by DNS and priorLES methods.In the DNS field,the importance of Kolmogorov scaling to preferential accumulation was validated by comparing the radial distribution functions under various particle Stokes numbers.The prior-LES fields were generated by filtering the DNS data.The subgrid-scale Stokes number(StSGS)is a useful tool for determining the effects of subgrid-scale eddies on particle motion.The subgrid-scale eddies tend to accumulate particles with StSGSb 1 and disperse particles with 1 b StSGSb 10.For particles with StSGS?1,the effects of subgrid-scale eddies on particle motion can be neglected.In order to restore the subgrid-scale effects,the Langevin-type stochastic model with optimized parameters was adopted in this study.This model is effective for the particles with StSGS N 1 while has an adverse impact on the particles with StSGSb 1.The results show that the Langevin-type stochastic model tends to smooth the particle distribution in the isotropic turbulence.

A new mixed subgrid-scale model for large eddy simulation of turbulent drag-reducing flows of viscoelastic fluids

A mixed subgrid-scale（SGS） model based on coherent structures and temporal approximate deconvolution（MCT） is proposed for turbulent drag-reducing flows of viscoelastic fluids. The main idea of the MCT SGS model is to perform spatial filtering for the momentum equation and temporal filtering for the conformation tensor transport equation of turbulent flow of viscoelastic fluid, respectively. The MCT model is suitable for large eddy simulation（LES） of turbulent dragreducing flows of viscoelastic fluids in engineering applications since the model parameters can be easily obtained. The LES of forced homogeneous isotropic turbulence（FHIT） with polymer additives and turbulent channel flow with surfactant additives based on MCT SGS model shows excellent agreements with direct numerical simulation（DNS） results. Compared with the LES results using the temporal approximate deconvolution model（TADM） for FHIT with polymer additives, this mixed SGS model MCT behaves better, regarding the enhancement of calculating parameters such as the Reynolds number.For scientific and engineering research, turbulent flows at high Reynolds numbers are expected, so the MCT model can be a more suitable model for the LES of turbulent drag-reducing flows of viscoelastic fluid with polymer or surfactant additives.

A new dynamic subgrid-scale model using artificial neural network for compressible flow

The subgrid-scale(SGS)kinetic energy has been used to predict the SGS stress in compressible flow and it was resolved through the SGS kinetic energy transport equation in past studies.In this paper,a new SGS eddy-viscosity model is proposed using artificial neural network to obtain the SGS kinetic energy precisely,instead of using the SGS kinetic energy equation.Using the infinite series expansion and reserving the first term of the expanded term,we obtain an approximated SGS kinetic energy,which has a high correlation with the real SGS kinetic energy.Then,the coefficient of the modelled SGS kinetic energy is resolved by the artificial neural network and the modelled SGS kinetic energy is more accurate through this method compared to the SGS kinetic energy obtained from the SGS kinetic energy equation.The coefficients of the SGS stress and SGS heat flux terms are determined by the dynamic procedure.The new model is tested in the compressible turbulent channel flow.From the a posterior tests,we know that the new model can precisely predict the mean velocity,the Reynolds stress,the mean temperature and turbulence intensities,etc.

Rational subgrid-scale modelling: a short survey

We review the previous attempts of rational subgrid-scale （SGS） modelling by employing theKolmogorov equation of filtered quantities. Aiming at explaining and solving the underlyingproblems in these models, we also introduce the recent methodological investigations for therational SGS modelling technique by defining the terms of assumption and restriction. Thesemethodological works are expected to provide instructive criterions for not only the rational SGSmodelling, but also other types of SGS modelling practices.

融合Kano-MD-SG的气体安全检测仪设计研究

目的解决气体安全检测仪研发中市场需求差异化高、研发投入有限等问题。方法首先,采用改进的Kano模型对研发人员和用户进行需求调研,确定设计需求;其次,基于模块化设计理念,确立功能与造型之间的对应关系,提出了“基础单元+外壳造型”的开发策略;最后,结合材料与工艺,运用形状文法生成大量造型方案,优选并确定最终方案。结果构建集成了Kano模型、模块化设计、形状文法的产品创新设计方法,准确获得了研发需求,完成了气体安全检测仪的创新设计。结论该创新设计方法有效解决了气体安全检测仪研发中的现实问题,为安全装备类产品提供了多元化设计思路。

基于LU-SGS的非结构弹簧网格迭代算法

针对运动间断拟合中需频繁更新网格点位置的特点,提出一种基于LU-SGS(lower-upper symmetricGauss-Seidel)迭代方法的非结构弹簧网格运动算法.根据弹簧网格原理构建与网格拓扑关系相对应的稀疏系数矩阵,将LU-SGS思想成功引入动网格迭代算法,并辅以合理的网格运动管理策略,实现动网格的快速迭代.研究表明,在非结构网格下,LU-SGS算法可以满足运动间断拟合的需求,在流场隐式时间推进时,仍能保证获得稳定解;与传统的SOR方法相比,计算时耗减少20%以上.

基于SGS流程的竞争情报与产品创新团队跨职能协作模式研究

[目的/意义]经济全球化趋势有利于资本和产品全球性流动,围绕新产品开发流程,建立跨职能产品创新团队,将有效推动跨职能间信息流转,对产品创新绩效产生积极影响。[方法/过程]文章基于SGS新产品开发流程,探索在新产品开发过程中以竞争情报与产品创新来组建跨职能团队,并根据不同企业发展现状与组织特点,研究建立不同组织模式的跨职能协作团队,并将团队协作嵌入新产品开发流程,从而提升企业产品开发的成功效率。[结果/结论]竞争情报团队跨职能协作模式,对打破传统开发流程中各环节松散耦合的弊端具有推动意义,能有效提升企业产品开发的科学决策效率。

Analysis of hohlraum energetics of the SG series and the NIF experiments with energy balance model

The basic energy balance model is applied to analyze the hohlraum energetics data from the Shenguang(SG)series laser facilities and the National Ignition Facility(NIF)experiments published in the past few years.The analysis shows that the overall hohlraum energetics data are in agreement with the energy balance model within 20%deviation.The 20%deviation might be caused by the diversity in hohlraum parameters,such as material,laser pulse,gas filling density,etc.In addition,the NIF's ignition target designs and our ignition target designs given by simulations are also in accordance with the energy balance model.This work confirms the value of the energy balance model for ignition target design and experimental data assessment,and demonstrates that the NIF energy is enough to achieve ignition if a 1D spherical radiation drive could be created,meanwhile both the laser plasma instabilities and hydrodynamic instabilities could be suppressed.

基于SGS模型的建筑火灾烟气数值模拟与实验验证

研究合理的火灾烟气运动数值模拟方法,指导建筑结构中防排烟与通风装置的设计布局。在大涡模拟方法的基础上,结合SGS湍流燃烧模型,对某地下通道内的火灾烟气运动进行数值计算。得出不同火源功率与排烟补风情况下通道内烟气温度分布与蔓延情况。设计4种对应于模拟工况的实验,对数值计算结果进行验证。根据验证结果可以看出,提出的改进方法对于建筑火灾烟气运动规律的计算比较合理。

国家电网企业信息架构模型SG-EA的构建与应用

企业信息系统变得越来越复杂,提升其对业务运行的支撑,是满足发展战略需要的最佳选择。提出了一种基于企业架构设计方法论,从企业全局角度进行企业架构模型的构建与应用,探讨了方法的理论依据、分析元模型与视图的构建过程、应用场景和应用成效。此方法论不但使信息系统与业务一致性分析更加标准化、自动化,而且容易构建稳健的企业信息系统架构,促进企业IT战略与企业业务战略的匹配,实现数据共享、模块集成、业务协同,满足未来不断变化的业务需求。

基于SG/Simulink无刷直流电机混合建模与仿真研究

System Generator(SG)为基于 FPGA 的硬件平台开发提供了便捷的设计方式和灵活的编程手段,Matlab/Simulik 是通用性的离线仿真工具,其模块化的建模方法具有高效、直观的特点。结合两者的优点,提出了 SG/Simulink 混合建模新方法,利用 SG 建立无刷直流电机(BLDCM)控制系统部分,Simulink 仿真 BLDCM 本体,通过 SG 中的 Gateway 模块,实现两者的无缝连接。仿真结果符合理论分析,证明了该方法的有效性和可行性。

基于SG-CIM的配电网数据平台及应用开发

国家电网公司提出的SG-CIM模型为我国电网建模和信息交互建立了统一的规范,方便了不同系统和应用间的信息集成。在现有SG-CIM模型的基础上,根据配电网业务需要,扩展了模型的类、属性以及相互关系。为克服电力系统安全分区对信息交互的影响,在安全Ⅲ区建立了数据汇聚平台。在统一数据源的基础上,构建了一体化平台。根据业务要求,进行了对象聚合,同时构建了实时数据平台,提高实时数据传输速度。在此基础上,以GIS为依托,根据业务流程,集成了跨系统的信息,开发了多个高级应用,并在工程中得到实践。

西北干旱区SG-SPAC系统水力模型的建立

文章论述了西北干旱区水资源的特点 ,利用现代农田水分研究方法研究了干旱区地表水、地下水、土壤、植物、大气连续体 (SG SPAC)系统的水分转化规律 ,建立了地表水、地下水和土壤水之间的水力耦合模型 ,为干旱区的水资源规划、开发和生态环境保护奠定了科学的基础。

基于IEC61968和SG-CIM的物联网系统与配网自动化数据交互模型

针对物联网示范工程建设中涉及的与多业务系统之间的信息集成需求,解决各应用系统间的数据冗余、信息孤岛及数据交互缺乏标准等问题非常重要。文章以IEC61968标准及国家电网公司SG-CIM模型为基础,研究制定了现有的物联网示范系统与配网自动化系统的数据交互模型,以此模型为基础研发了基于物联网的配网故障点精确定位高级应用功能并进行了验证。实践表明,该数据交互模型可有效解决物联网系统安全、高效地与多业务系统进行信息集成和数据交互问题,对于研发物联网系统在配网中的高级应用功能具有重要作用,也为物联网在配电网中的深化应用奠定了基础。

基于SG-CIM的企业数据库模型设计与应用

针对如何有效利用智能电网产生的海量数据问题,文中开发了基于国家电网公司企业统一信息模型(State grid-common information model,SG-CIM)的企业数据库模型系统,实现了系统之间的信息交互,电网的可视化操作,对电网相关业务进行分析管理,包括故障抢修,业务处理,电力分析计算等。首先,基于企业的业务领域不同,将其划分为12个主题域,并细致化每个主题的属性;其次,针对企业实际情况,分析企业数据库的设计需求,并对其进行具体的设计;最后采用Enterprise Architect软件对电网企业数据库进行UML建模,并将开发的系统应用于电网公司,实际应用效果验证了开发系统的有效性以及可靠性。