Cylinder moving in fluid,Solution diverging

Discussion in 'Hydrodynamics and Aerodynamics' started by arun_naval, Feb 27, 2013.

  1. arun_naval
    Joined: Apr 2010
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Newcastle

    arun_naval New Member

    Dear All,

    I had posted a thread yesterday regarding some help on problem of oscillating cylinder. Since i did not get any reply i thought of making the problem a little more simpler,before i could go on with the oscillating cylinder.I have considered a translating cylinder in +X dir and fluid flow towards -X. The velocity of cylinder is 5m/s and that of fluid is 20m/s. I have attached the meshing snap shot.

    I am using polyhedral and prism layer meshing. The motion is defined using DFBI morphing. Inlet and outlet,top and bottom regions are fixed in physics condition, Cylinder is as six DOf body and symmetry defined using grid velocity.

    The grid velocity is same as the velocity of the cylinder. I have tried various time steps. At first the solution was not even starting but after a couple of hours of reading and working i have got it running and the cylinder is also moving but the residuals are continuously increasing. It runs for sometime and then an error message is displayed which is attached.

    Can any one please guide me with the problem?

    Once i can establish this i can move on to the problem of an oscillating cylinder.

    Again if anyone can give me some idea of how to define the oscillations, it will be of great help.

    Please advice

    Regards
    Arun
     

    Attached Files:

  2. baeckmo
    Joined: Jun 2009
    Posts: 1,117
    Likes: 116, Points: 63, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    The message means that grid elements are "crossing" instead of attaching to the structure of nearby elements. What program are you using? Often, when a mesh error message is displayed, the error zone will be marked, for instance with the crossing boundaries in red. If this function is available, you may have to zoom in and visually check the regions close to the cylinder.

    I would first search for anomalies in the zone where hexagonal elements meet the prismatic ones.
     
  3. arun_naval
    Joined: Apr 2010
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Newcastle

    arun_naval New Member

    Hello,
    I am using Star CCM+. It does not show any highlighted zone. I will check for the transition zone again. I am not sure if i could use mesh morpher for this problem. Should i be using some other motion methods?

    Thanks
    Regards
    Arun
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.