基于Realizable k-ε湍流模型的氨气泄漏数值模拟研究

针对液氨泄漏事故,为了分析不同泄漏点、不同排风条件下氨气的运移规律,以便合理设置应急处置装备、采取有效措施,基于Realizable k-ε的氨气泄漏有限元数值模拟分析方法,计算了液氨泄漏质量,模拟分析了增加排风口、不同液氨泄漏口及不同液氨泄漏量的氨气扩散规律及浓度变化情况。模拟结果表明:对流排风口位置对于泄漏氨气浓度影响较大,泄漏口位置对泄漏氨气扩散影响不显著;氨气泄漏量的增加使得泄漏口垂直方向氨气浓度显著增加。

应用Realizable k-ε湍流模型的振荡水翼绕流数值模拟研究(英文)

采用计算流体力学软件Fluent提供的Realizable k-ε湍流模型计算了振荡水翼的绕流问题,利用有限体积法求解雷诺平均N-S方程,空间离散应用二阶迎风格式,速度—压力耦合格式为SIMPLEC格式;为了验证该数值格式及湍流模型,计算了文献中的算例并做了对比;考察了不同参数对振荡水翼周围流场及受力特征的影响,研究表明在一定水翼攻角条件下,水翼振幅及振荡频率均对振荡水翼的涡结构产生发展及其受力特征具有明显的影响.

基于Realizable k-ε模型的控制阀流场特性研究

针对煤化工行业中专用控制阀易于磨损失效的问题,提出一种基于Realizable k-ε的有限元数值模拟分析方法.以不平衡单座式控制阀为研究对象,通过对其内部结构进行简化,得到有限元分析的物理模型,基于Preston磨损经验公式,对控制阀内流场不同初始速度下的压力、体积分数和湍流耗散率的分布特性进行分析.数值模拟结果表明,当初速度小于10m/s时,控制阀表面磨损最小.

基于Realizable湍流模型的弯管流动模拟分析

以工程实际中广泛应用的管道为基础,针对管道输送中弯管的薄弱环节,基于Fluent可实现湍流模型,分别采用定常与非定常模拟的方法,建立油水两相流流场的数学模型,研究弯管油水两相流动的速度、压力、流线部分的特性。研究结果表明定常与非定常数值模拟弯管两项流动都具有较好的模拟效果。

修正Realizable k-ε模型在高压淹没水射流中的应用

淹没水射流在工程中具有广泛的应用,空化是高压淹没水射流的基本特征。现有的空化模型仍不完善,对各种工况普适性较差,数值模拟仍存在较大误差。为了提高数值模拟对淹没水射流的预测能力,采用Realizable k-ε模型模拟淹没水射流,使用修正的模型常数并结合滞止压力实验验证,研究5~40 MPa射流压力下的修正模型常数。结果表明,对模型常数进行修正可有效地提高模型对0~70倍直径射程范围内淹没水射流轴心压力的预测能力,使误差降低至10%以内,可见使用修正常数的Realizable k-ε模型模拟高压淹没水射流是一种简便且准确的方法。

Realizable和SST湍流模型对修正尾翼弹的气动适应性

在气动仿真中,Realizable k-ε两方程模型和SST k-ω两方程模型应用较广。通过对超声速炮射修正尾翼弹的气动仿真,分析了这两种模型在解决该类外形复杂的弹丸的仿真计算的适应性。先进行了两种模型的数学分析,然后,对仿真计算结果进行了分析。计算结果表明:SST k-ω两方程模型其湍流动能和湍流动能耗散率比Realizable k-ε两方程模型更稳定,更适合计算修正尾翼弹的气动。

基于标准和Realizable k～ε湍流模型的阶梯式溢洪道流的数值模拟

采用Realizable k~ε湍流模型并结合VOF自由面追踪技术对阶梯式溢洪道流进行了数值模拟。计算所得水力特性与文献中的实验观察结论基本一致,验证了该模拟方法在分析阶梯式溢洪道流中的有效性。分析了3个不同阶梯处的竖直表面压强分布情况,对标准和Realizable k~ε这两种湍流模型的预测结果进行了比较,结果表明Realizable k~ε湍流模型在该问题的分析中优于标准k~ε湍流模型。

静水条件下倾斜射流的Realizable k-ε和RNG k-ε数值模拟研究

进行了静水条件下倾斜射流的实验与数值模拟,分析了不同工况下倾斜射流的运动轨迹、顶点高度、横截面宽度及浓度分布情况与规律。重点验证了Realizable k-ε和RNG k-ε两个湍流模型在该问题模拟中的适用性,结果证明这两个模型都可以较准确地计算出静水条件下倾斜射流的运动与稀释情况,但前者相对后者更为精确。

Physically Realizable Broadband Acoustic Metamaterials with Anisotropic Density

Transformation acoustics are concentrated for the purpose of designing novel acoustic devices to tailor acoustic waves to achieve desirable characteristics. However, these devices require fluid or fluid-like materials with an anisotropic density that generally does not exist in nature. Therefore, we introduce pentamode metamaterials into an alternating multilayer isotropic medium model to build fluid-like metamaterials with an anisotropic density. A 2D acoustic bending based on transformation acoustics is established and investigated to verify our method. This idea provides a method to design broadband and physically realizable acoustic metamaterials with an anisotropic density and is meaningful for the design of acoustic metamaterials.

The Study and Investigation of Electron Trajectories in Free Electron Laser with Realizable Helical Wiggler and Ion Channel Guiding: A Computational Study

The following article has been retracted due to the investigation of complaints received against it. Mr. Mohammadali Ghorbani (corresponding author and also the last author) cheated the author’s name: Alireza Heidari. The scientific community takes a very strong view on this matter and we treat all unethical behavior such as plagiarism seriously. This paper published in Vol.3 No.3, 278-281, 2012, has been removed from this site.

旋流燃烧器数值模拟中Realizable κ-ε和RSM模型的比较

使用RKE模型和RSM模型对某旋流燃烧器进行3D冷态湍流流动模拟计算,并从精度、计算量和收敛性3个方面对两个模型进行了比较。通过与PIV所测得的出口冷态流场对比表明,两个模型均可以较准确地预测燃烧器出口的宏观流场、径向速度和轴向速度分布。相比较而言,RSM模型在预报流场速度峰值的位置、回流区的大小、主流射流宽度等方面比RKE模型更准确一些,在收敛性上RSM模型也占优,而在计算量上,RSM模型略大一些,但对反应流计算,两个模型计算量基本一致。研究表明在模拟旋流燃烧器流场时RSM模型具有一定的优越性,建议优先考虑。

Distribution,abundance,and realized niches of meroplankton by two different mesh size nets during spring 2017 in the Southern Yellow Sea,China

Meroplankton play a crucial role in both benthic and pelagic ecosystems.Existing quantitative research on estimating the quantities of meroplankton groups is both underrepresented and inaccurate.To investigate and evaluate the influence of varying mesh sizes(505 and 160μm)on the sampling efficiency of meroplankton,we conducted an examination using two commonly used plankton nets during the spring season in the Southern Yellow Sea(SYS).Our study revealed a total of 12 meroplankton groups,with 9 groups identified in the 505-μm mesh nets and 11 groups in the 160-μm mesh nets.The results demonstrated the superior collection efficiency of the 160-μm net compared to the 505-μm net across the majority of meroplankton groups.Furthermore,we focused on exploring the abundance,distribution patterns,and realized niches of meroplankton collected by the two mesh size nets,and observed that the distribution of meroplankton closely resembled the distribution of possible benthic adults in the SYS.Correlation analysis of the six dominant groups collected in the 160-μm mesh nets revealed that seawater temperature and salinity emerged as the key environmental factors driving variations in meroplankton abundance within the SYS.This study also found that a smaller mesh size net does not necessarily capture meroplankton more comprehensively.A comprehensive understanding of the ecological characteristics of meroplankton requires the combination of two types of nets for research.Our research significantly advances our understanding of the quantification,abundance,and distribution of meroplankton,serving as a valuable contribution to the broader landscape of detailed quantitative meroplankton studies.

Design of a Metasurface Antenna Based on Characteristic Mode Theory

A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutually orthogonal principal modes of the optimized periodic patch structure areexcited by a center-feed dipole.A differential feeding network is employed to realize impedance matching.Prototype with profile height of 0.07λ_(0)(λ_(0)is the wavelength in free space at the lowest operatingfrequency)is fabricated and assembled to verify the simulation results.The measured results show that thereflectance coefficient of proposed matesurface antenna is less than-10 dB in the whole operating bandrange from 4.2 GHz to 5.5 GHz,a relative bandwidth of 26.8%is achieved,and the maximummeasured realized gain is more than 9 dBi with a maximum radiation efficiency of 90%.The designprovides a guideline on the application of characteristic modes(CMs)to radiation problems.

Metaverse Upsurge Drives Virtual Human Industry to Upgrade

The concept of a virtual human is rapidly fermenting with the boom of the metaverse in 2020.In March 2021,Roblox,a game company focusing on the socialization of teenagers’games and the free realization of UGC,went public.In its prospectus,Roblox is defined as the concept of the metaverse.Under this background,as the direct embodiment of“virtual identity”and“virtual reality coexisting”under the concept of the metaverse,the emerging definition of virtual human and its representative virtual image has gradually caught the attention of the public.

Practices and Reflections of CNOOC on Building World-Class Enterprises

At present,China is facing new strategic opportunities as well as risks and challenges in its development.Faced with the challenges brought by current global major risks,China urgently needs to build a group of world-class enterprises as ballast stones.Accelerating the development of a number of world-class enterprises is an important support for China to enhance its comprehensive strength and international competitiveness,and is crucial for the realization of the strategic blueprint for socialist modernization.After more than forty years of reform and opening up,Chinese enterprises have rapidly developed and grown stronger,with their position rising and their influence in the global market increasing continuously.However,Chinese enterprises are“large in size but not yet strong enough”.In this context,this paper systematically analyzes the practical significance and theoretical connotation of building world-class enterprises and the status quo of building world-class enterprises in China and takes CNOOC as an example to deeply analyze the practices of large central enterprises to build world-class enterprises at the levels of group and subsidiaries,providing a reference for Chinese enterprises to accelerate their progress towards world-class enterprises.

Pragmatist View of Human Rights:Theoretical Explanations of China’s Human Rights Practice

The pragmatist view of human rights represents a the-oretical condensation of the Chinese practice in human rights devel-opment.In view of the problem of circular idling between rights and claims caused by the traditional view of human rights of focusing on contents and not valuing implementation,social segmentation caused by empty talks on interests and claims while ignoring social develop-ment,and the phenomenon of the issue of human rights completely becoming empty and useless political rhetoric,the pragmatic view of human rights,based on the fact that there is a gap between the claims and realization of human rights,emphasizes that instead of blindly ex-panding the types of rights in term of text,it is better to base on prac-tice and promote the maximum realization of existing rights through development.The pragmatist view of human rights attaches impor-tance to relevant economic,social and cultural basis to promote the realization of human rights,rather than only focusing on the claims themselves;it pays greater attention to enhancing the realization of rights,rather than the distribution of rights under the total limit;it ad-vocates more for cooperativism in the realization of rights,rather than confrontation.The pragmatic concept of human rights takes Marxism as its theoretical basis and the gene of practice and the dimension of development as its theoretical characteristics,and promotes the devel-opment of human rights through the realization of rights.

Construction of Regional Ecological Capital Operation Mechanism System from the Perspective of Green Economy Development

Green development has gradually become the main theme of the current world economic development.Green transformation development and cracking the contradiction between ecology and economy need to build an effective ecological capital operation system and mechanism to support,encourage the effective operation of regional ecological capital,promote the appreciation and preservation of ecological capital,and escort the operation.This paper constructs a four-in-one regional ecological capital operation mechanism system,in which the"accumulation mechanism"is the prerequisite,the"conversion mechanism"is the key link,the"compensation mechanism"is an important supplement,and the"incentive mechanism"is the safeguard measure,which aims to ensure the smooth progress of the construction of beautiful China in the new era and realize the socialist modern power.

Critical Success Factors for Citizen Development

The purpose of the research was to assess the impact of Citizen Development activities on digital transformation. The research identified eight categories that contribute to the success of Low-code No-code (LCNC) projects: 1) Strategy;2) Infrastructure;3) Technology;4) Processes & Procedures;5) Governance;6) Culture;7) People;8) Goals & Metrics and selected six critical success factors from these categories: 1) Operational Efficiency;2) Time Savings;3) Timeframe to Realize Value;4) Employee Engagement;5) Participation;6) Number of Sponsored Ideas. End users of the digital transformation efforts through Citizen Development were asked to assess the six critical success measures in terms of performance and importance criteria. The research results identified that focus should be applied to improving “Timeframe to Realize Value”, on “Operational Efficiency”, and on “Time Savings” to deliver success.

潜航器微气泡减阻数值模拟方法研究

近年来微气泡减阻技术应用于水面舰船的相关研究取得重要进展,许多舰船已经采用了此类技术。然而该技术在潜航器上的应用整体上仍处于理论分析和试验测试阶段。以回转体潜航器简化模型为研究对象,利用多孔介质来简化喷气小孔,并结合不可压缩水体和可压缩理想气体的流体体积(VOF)方法,建立了Realizableε-k湍流计算模式。通过拖曳试验验证了多孔介质等效喷气小孔的合理性和数值模式的准确性,结合试验和数值结果探究了微气泡减阻技术对潜航器航行阻力的影响。数值结果显示,气泡对潜航器尾流低速区的改变使尾部压力分布产生变化从而导致压差阻力增高。同时气泡可以显著降低其覆盖区域的黏性阻力。并且随着来流速度的提高,气泡覆盖范围扩大,黏性减阻率持续增加。进一步地,建立了加长改进模型,数值模拟结果表明,微气泡减阻技术不仅能大幅减小黏性阻力,还能有效减小模型总阻力。

风雨场条件下汽车乘员舱气动噪声数值模拟

本研究以某汽车为研究对象,基于数值模拟探讨不同降雨量工况下的汽车乘员舱气动噪声声压级水平。采用Realizable k-ε/LES湍流模型来模拟无雨时的单相流流场,再添加离散相模型(DPM)来模拟有雨时的两相流流场,以声类比(FW-H)方法获得了不同降雨量下车身表面各子系统的1/3倍频程平均输入激励,采用混合有限元-统计能量分析(FE-SEA)方法获得了驾驶员耳旁气动噪声声压级水平。仿真结果表明:在20-1000Hz频段内,有雨工况下的驾驶员耳旁的声压级在各中心频率处都低于无雨工况,小雨工况和中雨工况下的驾驶员耳旁总声压级较为接近,大雨工况下的驾驶员耳旁总声压级最低。