Turbulence Kelvin Helmoltz homework


Just following the guideline vídeo for the Kelvin helmoltz instability.

Should the gravity in the vertical direction be enabled?

thanks for the output.


  • KremellaKremella Posts: 3,123Admin
    edited November 2020


    For KH instability, the following condition must be satisfied. Please take a look at the results slide of this simulation example (slide 6)

    Here is the link:

    In the simulation example video, we use two same fluids (air and air). Because rho_1 = rho_2, the RHS term (of the inequation) becomes 0. It will not matter if you turn on or off the gravity term. This is why you see that there is no gravity term enabled in the simulation video. As long as U_1 is not equal to U_2 (for such a case), the above condition for KH instability will be satisfied.

    However, when we use two different fluids (in the case of air and water vapor), it is important to check if the above condition is satisfied. It is, therefore, necessary to activate the gravity term (in the negative y-direction). For the velocities and fluid properties mentioned in the results slide, I strongly recommend that you calculate your LHS and RHS terms to understand KH instability better.

    I hope this answers your question.

    Thank you.


  • AbubakarAbubakar Posts: 140Member
    edited January 29

    Hi Karthik,

    As of know, like you people are providing course's for free so, will it free in the future also. If, no then please ? provide for free. As I'm a student and I am from middle class i can't buy this course's. And ANSYS is the well known and established company ANSYS can provide these course's for free for the sake of education upskill. And would like to thank ANSYS and instructor of the course's for providing these course's for free.

    Thank you,

    Abubakar khan

  • KremellaKremella Posts: 3,123Admin


    Thank you very much for this feedback. We will definitely keep this in mind as we keep adding new courses. And I'm glad you are taking these courses and learning modeling and simulation.

    Good luck!


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