Skip to content
  • 求解器寻找

    OpenFOAM
    3
    0 赞同
    3 帖子
    4k 浏览
    L

    谢谢啦,主要想找一个带相变的可压缩气液两相流的solver,我再找找试试~

  • 0 赞同
    2 帖子
    3k 浏览
    T

    找到数值发散的原因了,是热流密度设置过大

  • 比冲?

    Algorithm
    2
    0 赞同
    2 帖子
    4k 浏览
    H

    @liujuncfd 这恐怕不行吧,比冲是推力除以单位时间消耗燃料的质量(或重量)。

  • 关于动压、静压和总压的一些理解

    Algorithm
    1
    0 赞同
    1 帖子
    3k 浏览
    H

    实际工程上说的压力是什么压,压力表测到的是什么压,还有就是数值模拟计算得到的压力结果我们应该关注什么压呢?或者说从动压静压总压分布图上我们能看出什么东西。谢谢

  • 0 赞同
    4 帖子
    5k 浏览
    C

    @Dingcy 在 如何输出出口escape的颗粒数量随时间变化的曲线? 中说:

    如何输出出口escape的颗粒数量随时间变化的曲线?之前算单向流的时候我输出出口浓度随时间变化曲线是通过paraview那个plot selection over time, 但是现在这个颗粒好像不能那么整了....:136:
    1c05a757-a68a-499f-bfc9-1582a3c49a26-image.png
    前辈您好,请问这个操作怎么实现,得到下图:134:

  • CFD青年成长支持计划(2021)

    公告
    137
    0 赞同
    137 帖子
    165k 浏览
    F

    想问一下李老师这个计划还有吗!!很想要这本湍流模型:mianmo:

  • 0 赞同
    5 帖子
    6k 浏览
    学流体的小明

    fvSolution里面的pFinal,relTol应该调到0吧。
    矩阵最终求解的这些*Final一般都强制要求满足容差。
    应该是这个原因导致你某一步没收敛,或者误差逐渐积累,导致发散。

  • 翻到之前的基金申请拒信

    CFD彩虹条
    6
    0 赞同
    6 帖子
    8k 浏览
    李东岳

    不知道他们几千万的CFD算法研究经费都是怎么构成的 :143:

  • 什么样的模拟才叫大涡模拟(LES)?

    Algorithm
    10
    0 赞同
    10 帖子
    29k 浏览
    小狗狗

    流体的动能通过涡耗散,而空间网格最小尺寸决定了你数值计算能捕捉到的最小涡的尺寸,因此小于你网格能够捕捉的尺寸的涡,其含有的动能无法通过数值模拟耗散掉。为了解决这个问题,可以理解为增加了一个和“空间尺度”有关的人工耗散,进而对小尺度的涡进行耗散,因此叫做大涡模拟。而刻画这个小涡空间尺度的标准和你的第一层网格有关,因为其决定了小涡的最大尺寸(也就是在空间上被过滤的小涡的最大尺寸)。

  • 求助柱面网格质量差的问题

    Meshy
    6
    0 赞同
    6 帖子
    12k 浏览
    AlexA

    我认为这个是和几何无关的,衡量网格质量的参数中有一个叫aspect ratio,这个值为1时最好,像那种类似薄片或者细长的网格,这个值会很大,这种网格一般质量很差。

  • snappyHexMesh画内部网格

    Meshy
    6
    0 赞同
    6 帖子
    11k 浏览
    Z

    @chengan-wang 你好,请问你说少了一个定义是啥?我好像遇到了和你一样的问题,先谢谢啦。

  • 瞬态计算问题

    Fluent
    6
    0 赞同
    6 帖子
    9k 浏览

    @cccrrryyy 受教了,谢谢您的指导,您说得对极了,假如要真能收敛,应该最大默认的最大迭代步数是够用的了,问题还是出在格式上,我把格式调成PISO,压力调成standard,然后步长变成0.0001的一半之后,这个问题就解决了,cfl数在fluent里输出的问题我会自己琢磨的,谢谢您!

  • 如何理解CFD计算中的数值噪声?

    Algorithm
    2
    0 赞同
    2 帖子
    4k 浏览
    bestucanB

    比如
    当用浮点数乘除得到一个整数的时候,很可能是 0.99999999999 1.0000000001。
    这个完全无法预测。写函数解决?可是又不知道它本该是整数还是很接近这个整数。

  • 0 赞同
    2 帖子
    3k 浏览
    S

    来个人回复一下嘛

  • UCSD-SDSU 联合博士项目招生

    CFD彩虹条
    1
    0 赞同
    1 帖子
    2k 浏览
    O

    Job description
    We provide the opportunity for the joint Ph.D. program between UCSD and SDSU.

    Research motivation
    Do you know that measurement in a turbulent environment has its own "sixth
    sense"? In fluid dynamical systems, measurements can be used to figure out
    events that happened far away from the probing location.
    Through state-of-art data assimilation techniques, we can trace back the origin
    of any information we have measured. We used this technique to locate the
    release of a pollution release, and reconstruct unknown flow fields from limited
    measurements.

    Are you self-motivated to do a Ph.D. in interdisciplinary researches about fluid
    dynamics, inverse problems, and optimization? We are looking for Ph.D. students
    that are willing to spend time studying in an encouraging and creative
    environment!

    There has been a long-hovering question about how to combine experimental
    measurements with numerical simulations. Especially in terms of designing a
    turbulence model that agrees with experimental studies. In addition, the design
    of sensor networks or sensor weighting can be optimized in terms of the amount
    of information obtained.
    In this Ph.D. project, you will develop novel simulation techniques that combine
    machine learning techniques with data assimilation.

    The required skills and preferred profile
    We are looking for self-motivated young researchers from mechanical
    engineering, aerospace engineering, computational physics, applied mathematics,
    or other closely related areas.

    Familiar with MATLAB and FORTRAN with MPI. C++ and python is a plus. Good conceptual understanding of calculus and linear algebra. Experience with simple machine learning algorithms. Good communication skills including presentation skills, academic writing
    with latex or word. Please note that the GRE is required for all JDP applicants and cannot be
    waived. Having a part-time hobby is a plus.

    Location
    Work is carried out in the Data Assimilation group at Aerospace Engineering, San Diego State University.
    We study various inverse problems in fluid dynamics using numerical simulations
    with the discrete adjoint operator.
    For further information, please visit us at
    https://qiwang.sdsu.edu/

    Information and application
    Interested applicants should visit
    https://www.engineering.sdsu.edu/admissions/jointdoc_areomech.aspx
    for more details about applying for the joint program.
    Meanwhile, please reach out to Qi Wang (qwang4@sdsu.edu), including:
    • A short description of your qualifications and motivation to apply for this
    position.
    • CV or resume.
    • Transcripts from your Bachelor and Master degrees.
    Selected candidates will be invited to an interview and should prepare a
    scientific presentation as part of the requirements.

    We highly value diversity at our university. Applicants from all backgrounds are
    welcomed.

  • 分区运行时的错误,使用的虚拟机

    OpenFOAM
    7
    0 赞同
    7 帖子
    8k 浏览
    S

    @李东岳 李老师,这是我自己编译的一个求解器,我在constant文件夹下将g从(0 0 -9.8)改为(0 0 0),后消失了,但是不符合正常要求呀

  • 0 赞同
    5 帖子
    6k 浏览
    W

    @李东岳 感谢东岳老师的回复。已解决。需要在system里有一个单独的forceCoeffs文件,然后在controlDict里的添加functions{#include "forceCoeffs"},这样会在输出文件里输出每一步的Cd等相关信息。感谢老师!

  • 不同湍流强度下的来流

    OpenFOAM
    11
    0 赞同
    11 帖子
    18k 浏览
    李东岳

    @pengdi LES这么添加是不对的。你那个公式是RANS的k,不是k_sgs。LES那面如果你用smagorinsky,不需要给k

  • 气流中水滴内部流场模拟

    Fluent
    4
    0 赞同
    4 帖子
    6k 浏览
    W

    网格问题?液滴被设置成壁面了?

  • 0 赞同
    5 帖子
    7k 浏览
    L

    @李东岳 嗯,两个一起下下来就可以的,之前理解错了。