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  • fluent空气龄

    Fluent
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    I

    空气龄这个概念在通风领域应用比较广泛,我对此不大了解,但觉得这个物理概念上和停留时间相似。
    因此扩散系数本质上于空气或者示踪气体扩散系数相似。
    相关理论可以参考一下 https://age-of-air.forumotion.com/

    openfoam 里面的空气龄有个类似的solver, 可以参考一下 (19楼)
    https://www.cfd-online.com/Forums/openfoam-post-processing/68300-mean-age-air.html

  • banana method是什么意思

    OpenFOAM
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    DY大世界D

    @Cp_Zhao 明白了,感谢指点!!

  • 连续性方程不收敛怎么办

    Fluent
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    L

    连续方程 如果你是在模拟一个工程实际设备 这种不能达到-4的情况是比较常见 通常在-2左右 这代表在你的设备设计中间 真正的运行的时候 设备并不能保证一个进气和出气均衡的稳态(比如内部有一部分涡旋致使一部分进气永远在这里堆积) 而其他方面的原因上述几位已经讲解过了 对于工程模拟来说 连续性不达标的问题是比较常见的 你可以看看你的设备内部是不是存在涡旋流 或者是因为本身你的边界条件的设定是与实际不符合的 比如你在一个明显不均匀的出口面取了一个平均压力出口值 这样有的时候你需要扩充出口 直到真正符合工况的外界条件

  • 大家发朋友圈越来越少了

    CFD彩虹条
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    @李东岳 这两年的学生真的是过的没劲。。

  • ICEM大家怎么发音?

    Meshy
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    Q

    啊客母~

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    李东岳

    @hurricane007 我去,忘了。。。这个我当时打算自建一个免费的计算中心。后来发现一直需要给客户装机,电力都放在那面了,这个自己用的一直没搞起来。

    我距离百亿市场只是因为电路容量不够 :136:

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    supersoldierS

    @liqiwen 还可以对结构网格进行二次开发, [基于FLUENT软件的导弹意外点火情况下舱室维护仿真平台开发

    ](http://d.g.wanfangdata.com.cn/Thesis_D429353.aspx)这个论文的3.1.2节有讲用index来对ICEM CFD二次开发的功能。

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    可参考该篇博文:http://liusuanyatong.blog.163.com/blog/static/2155951572016527422386/

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    在方柱计算中,对升力系数进行FFT分析,取样数据点在10000左右,得到如下结果,主频与实验较为吻合,在高频处出现谐振,是由于方柱前缘分离剪切层中K-H不稳定性导致的升力系数高频振荡吗?谐振又是怎么产生的呢?
    诚心向各位前辈请教,求指导!
    FFT Power.jpg

  • fluent 模拟油滴的对流扩散

    Fluent
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    各位老师w71h11131532_1601213641_696.png ,我想模拟一下油滴在超临界水里下落过程中的对流和扩散问题:
    初步打算用VOF模型来捕捉相界面,但有一个问题VOF并不能解决扩散的问题。请问有没有什么比较好的解决方案?
    如果用UDF/UDS来解决扩散项的问题,请问能不能分享下类似的代码?

  • 关于negSumDiag()的一个问题

    OpenFOAM
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    G

    @wwzhao

    是的,OpenFOAM中面的方向定义永远是从小编号指向大编号,Gauss定理中面的方向指向外。也许把这些面分为大面和小面区分一下更容易理解。

    对于编号大于$P$的单元$U$,他们之间面上的量为:

    $$\phi_ f = \varpi \phi_{P} + (1 - \varpi) \phi_{U}$$

    $$\dot { m } _ { f } = ( \rho \mathbf { u } ) _ { f } \cdot \mathbf { S } _ { f }$$

    对于编号小于$P$的单元$L$,他们之间面上的量为:

    $$\phi_ f = (1 - \varpi) \phi_{P} + \varpi\phi_{L}$$

    $$\dot { m } _ { f } =- ( \rho \mathbf { u } ) _ { f } \cdot \mathbf { S } _ { f }$$

    $$
    \sum _ { f \sim n b ( P ) } ( \rho \mathbf { u } \phi ) _ { f } \cdot \mathbf { S } _ { f }
    = \sum _ { N \in L ( P ) } \left( - \dot { m } _ { f } \phi _ { f } \right) + \sum _ { N \in U ( P ) } \dot { m } _ { f } \phi _ { f }
    $$
    $$
    = \sum _ { N \in L ( P ) } - \dot { m } _ { f } \left[ ( 1 - \varpi ) \phi _ { P } + \varpi \phi _ { N } \right] + \sum _ { N \in U ( P ) } \dot { m } _ { f } \left[ \varpi \phi _ { P } + ( 1 - \varpi ) \phi _ { N } \right]
    $$

    $$
    = \left( \sum _ { N \in L ( P) } - \dot { m } _ { f } ( 1 - \varpi ) + \sum _ { N \in U ( P ) } \dot { m } _ { f } \varpi \right) \phi _ { P } + \sum _ { N \in L ( P ) } - \dot { m } _ { f } \varpi \phi _ { N } + \sum _ { N \in U ( P ) } \dot { m } _ { f } ( 1 - \varpi ) \phi _ { N }
    $$

    这样可以看出lower存的是 $- \varpi _ { f } \dot { m } _ { f } $, upper存的是$\dot { m } _ { f } ( 1 - \varpi ) _ { f } $.并且diag存的是
    $$a _ { P } = -[\sum _ { N \in L ( P ) } \dot { m } _ { f } ( 1 - \varpi ) + \sum _ { N\in U ( P ) } (-\dot { m } _ { f } \varpi )]$$

  • 周期网格角部处理问题

    Meshy
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    piteqiuP

    我这个是一个圆柱,分成1/26,成为周期对称模型。中间是空气,不能省略。

  • Fluent 如何设置降雪粒子

    Fluent
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    I

    @caizhao https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016JD025316
    可以参考一下这篇文章
    上面链接打不开的话,可以用下面这个
    https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JD025316

  • 大涡模拟LES

    Fluent
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    @纵浪大化 好的,常常交流联系

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    bestucanB

    @李东岳 我就记得我之前搞过,后来坑太深了,就没搞了。

    这些涉及到图形处理的各个层,又是平台不同,又是商业公司夹私货,那些个组件的名字本来就乱七八糟,缩写规则还不一样。想短时间了解就更乱。

    大概就是,可以软件渲染(OSMesa),可以硬件渲染(EGL)。
    其实都是基于Open GL,就这三个英语词空格隔开一起搜都一大堆讲更多术语关系的文章。

    paraview 默认用软件渲染,想要硬件渲染把 EGL 编译选项打开就行了,这就有个忘了打开报错的:
    https://discourse.paraview.org/t/build-paraview-for-nvidia-gpu/8309
    但这个是单GPU的,不知道多GPU的怎么搞,

    我的GPU是当显卡用的,一开paraview就调用GPU,当然是为“图形界面渲染"的,不是为“paraview渲染”的,这俩还都是opengl下面的,那些名词太乱了。

    我试着编了一下 pvserver能多线程跑在GPU上,
    Screenshot from 2022-06-11 15-52-46.png
    就是这个方法:
    https://github.com/Kitware/ParaView/blob/master/Documentation/dev/build.md

    当然编译之前已经安装好nvidia自带的驱动了。

    nvidia 早些年自己出过 paraview 的插件:
    https://www.nvidia.com/en-us/data-center/index-paraview-plugin/
    不过是针对 paraview 5 的

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    P

    英国谢菲尔德大学(The University of sheffield)Energy2050团队(http://energy2050.ac.uk)在招一个做CFD方向的全奖博士,做旋转填料床反应器捕捉二氧化碳的CFD仿真研究,对此职位感兴趣的研究生或者优秀本科毕业生可以申请(可直博),目前的申请截止日期是2022年7月22日(可能推迟),如来不及,入学时间可推迟到明年一月。

    谢菲尔德大学,世界百强名校,著名的CFD仿真软件Fluent的发源地,课题组学术氛围很好,适合静心搞科研。课题组在CFD领域有几十年的研究基础,在CCUS领域有丰富的研究资源,课题紧扣国内火热的"双碳"主题,该细分方向组里有7年的研究基础了,可以在前人的基础上接着做。

    具体招聘信息如下:
    We have a fully funded PhD studentship and look for applicants open to both UK and international students: Engineering doctorate (EngD): Predicting performance of intensified carbon capture inside rotating packed beds using CFD modelling

    If you know any good students from China, or the UK, please encourage them to apply.
    Any questions then let them to contact Professor Lin Ma: https://www.sheffield.ac.uk/mecheng/people/academic/lin-ma

    The advert is on findaphd.com: https://www.findaphd.com, search for the project 搜索 predicting performance of intensified carbon capture inside rotating packed beds using cfd modelling。

    或直接通过以下链接:https://www.findaphd.com/phds/project/engineering-doctorate-engd-predicting-performance-of-intensified-carbon-capture-inside-rotating-packed-beds-using-cfd-modelling/?p145128#opennewwindow

    Please make sure that they apply through the university of sheffield website: https://www.sheffield.ac.uk/postgraduate/phd/apply/applying.

    课题介绍:

    Carbon capture is considered the only technology able to decarbonise the hard-to-abate industries. many of these industries utilise legacy sites with little space for large new unit operations required in conventional carbon capture. rotating packed beds (RPB) look to solve this problem by intensifying carbon capture and reducing the footprint required by up to ten times, while also significantly decreasing the capital cost of these units. when combined with proprietary solvents, it is believed the cost of capture can be reduced to $30/tonne CO2 in some cases, helping to enable the rapid uptake of carbon capture and progression towards net zero.

    RPB are a novel technology that utilise the principles of process intensification to enhance the performance of mass transfer processes between fluids. given the application of rpb to the field of CO2 capture is relatively new, there is uncertainty regarding the impact of different process variables on the performance of the rpb that would otherwise require a significant amount of practical experimentation to investigate. computational fluid dynamics can enable the process to be accurately modelled, allowing for quick and inexpensive prediction of performance under various conditions.

    In this project a rotating packed bed absorber will be modelled in ansys fluent, with validation of the model’s outputs through use of the 1 tonnes of co2 per day (TPD) pilot-scale rotating packed bed absorber at the university of sheffield’s translational energy research centre. Initial research will involve investigating the impact of operational conditions and physical properties of the solvent on capture performance. As the project continues, the scope will widen to include sensitivity analysis of design parameters and the impact of scaling the RPB absorber on the existing project outputs and learnings. Additionally, further rotating unit operations could also be investigated.

    This project will utilise and develop your knowledge surrounding CFD modelling, mass and heat transfer, reaction kinetics and chemical equilibria. You will work closely with carbon clean, a global leader in the development of carbon capture technology and pioneers in the use of RPB for industrial decarbonisation. Your findings could directly impact the design and operation of commercial working carbon capture facilities, supporting the pathway to net zero.

    We are seeking applicants to start in september 2022.

    The project will be part of the EPSRC-supported centre for doctoral training in resilient decarbonised fuel energy systems. The student who undertakes it will be one of a cohort of over 50 students in a broad range of disciplines across the universities of sheffield, nottingham and cardiff.

    The research work will be based in the energy research group within the department of mechanical engineering and the translational energy research centre (TERC) at sheffield which is a brand new, high profile, innovation focused national research facility. You will be working within an exciting and dynamic group with approximately over 60 researchers undertaking a broad area of energy research with approximately three years' extensive research time in industry, preparing for high-level careers in the energy sector.

    Funding notes
    The studentship will cover full university fees and a tax-free, enhanced annual stipend of £20,352, including £16,062 (2022/2023) a year for four years and a stipend enhancement of £3,750 per annum.

    英国的全奖机会非常少,机会难得,欢迎各位优秀的CFDer申请!

  • 安装ntfs-3g

    CFD彩虹条
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    李东岳
    wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo && yum -y install ntfs-3g
  • SA模型计算射流

    Fluent
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    I

    @楼道男孩 SA用来射流中不多,一般用 k-w之类的 或者v2f

  • SnappyHexMesh为什么总是无法移除固体

    OpenFOAM
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    DY大世界D

    画网格过程中出现这个提示是什么意思
    1.png

  • 国产CFD软件

    CFD彩虹条
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    D

    @bestucan 还是那四个字:适者生存