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  1. Old Comment
    SergeAS's Avatar

    Computational Core of HyperFLOW2D now open source, meet OpenHyperFLOW2D !

    Well, first of all it is necessary to agree on the terms.
    I do not know which solver you use. So let's start with their classification.

    At first:

    Solvers are dimensional and dimensionless. Most solvers dimensionless. In contrast OpenHyperFLOW2D - originally the dimensional solver as its core code was created for the engineering design. That is, all the differential equation in this case are written in dimensional form.

    Secondly:

    Solvers are use the concept of a gauge pressure (p_g) and using the absolute pressure directly. In case of gauge pressure concept, to obtain the absolute pressure we should add gauge pressure to the pressure, which operates solver.


    OpenHyperFLOW2D initially uses the concept of absolute pressure directly

    Next point, the physical aspect of your case.
    When you say "Oulet pressure BC - 0 P" it means outflow in the vacuum ?

    In my case outflow occurs in the atmosphere,
    that is equal to the ambient pressure 1.0e5 Pa

    If your solver uses the concept of a gauge pressure then your BC can mean both.

    It depends on the value of gauge pressure:

    p_g = 0 Pa -> vacuum outflow
    p_g = 1.e 5 Pa -> atmosphere outflow


    In the case of outflow in vacuum instability is normal. In this case, usually zero pressure replace a very small non-zero,
    but not everyone solver can be considered this (OpenHyperFLOW2D can)

    Now concerning the the initial and BC of the above case:

    Since the problem of axially symmetric, simulated only half the nozzle.
    Image obtained with a full nozzle in the postprocessor.

    BC:
    - X- axi - symmetry BC (radial velocity and gradients of all parameters is zero)
    - left boundary in chamber - Dirichlet BC with total pressure 7.2e6 Pa and total temperature 3338.5 K.
    concentration of combustion products - 100%, air - 0%
    - left boundary in ambient area - Dirichlet BC with total pressure 1.0e5 Pa and total temperature 300 K.
    concentration of combustion products - 0%, air - 100%
    - top boundary - Dirichlet BC with total pressure 1.0e5 Pa and total temperature 300 K.
    concentration of combustion products - 0%, air - 100%
    - right boundary - Neumann BC with zero gradient in axial direction
    - nozzle walls - "no-slip" BC

    Initial conditions:

    - chamber from left boundary to throat filled gas with total pressure 7.2e6 Pa and total temperature 3338.5 K.
    concentration of combustion products - 100%, air - 0%
    - another domain part is filled gas with total pressure 1.0e5 Pa and total temperature 300 K.
    concentration of combustion products - 0%, air - 100%

    The boundary between the domains simulates a frangible disc in throat of nozzle.

    So as not to attract attention spambots I do not give here my e-mail, but you can easily find it in any files header of OpenHyperFLOW2D project
    permalink
    Posted July 13, 2015 at 03:52 by SergeAS SergeAS is offline
  2. Old Comment

    Computational Core of HyperFLOW2D now open source, meet OpenHyperFLOW2D !

    Boundary conditions

    Yes i saw your supersonic nozzle picture.
    I am also trying to design a supersonic nozzle with a Exit Mach of 3.0
    but the results we diverging .
    I used BC as (Inlet-Pressure of 300000 P , Oulet pressure BC - 0 P , walls as stationary )
    so wanted to know your BC's and model setup details of how did you specify inlet , outlet and walls and did you use freestream conditions in the surrounding?

    hope you can help and this clearifies your question.
    and if you can share me your Email, i can send you picture showing geometry i am working on. (tried attaching picture over here but failed)

    Regards,
    Mehlam.
    permalink
    Posted July 12, 2015 at 14:02 by Mehlam Mehlam is offline
  3. Old Comment
    SergeAS's Avatar

    Computational Core of HyperFLOW2D now open source, meet OpenHyperFLOW2D !

    Quote:
    Originally Posted by Mehlam View Comment
    i am doing simillar work.
    can you tell me what initial & boundary conditions did you use?
    Also plz just which flow model you used??
    I do not quite understand your question. What do you mean by this case, "similar work"? The models, which are used in my code are briefly described in the wiki. Or you mean a picture with a Nozzle case that is show as an illustration?
    permalink
    Posted July 12, 2015 at 05:47 by SergeAS SergeAS is offline
  4. Old Comment

    Computational Core of HyperFLOW2D now open source, meet OpenHyperFLOW2D !

    i am doing simillar work.
    can you tell me what initial & boundary conditions did you use?
    Also plz just which flow model you used??
    permalink
    Posted July 11, 2015 at 23:06 by Mehlam Mehlam is offline
  5. Old Comment
    SergeAS's Avatar

    Dark side of Amdahl's law

    This is due to the fact that the one cluster was used Infiniband DDR and has nodes on NUMA architecture and a smaller cache (Opteron 285) against the other cluster which used SDR on the SMP (Xeon) and large cache.

    The addition for each node we has two data exchanges (except first and last node) on Infiniband and 3 exchanges of internal memory (SMP or NUMA).

    PS: If I use one process per node (exchange only for InfiniBand) that scalability will be even better, it's a paradox but a fact
    permalink
    Posted March 28, 2012 at 10:20 by SergeAS SergeAS is offline
  6. Old Comment
    lakeat's Avatar

    Dark side of Amdahl's law

    Hi, newbie here, why SDR shows better than DDR in your results?
    permalink
    Posted March 28, 2012 at 09:20 by lakeat lakeat is offline

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