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Thread: Probably basic, but...

  1. #1
    Adobe Evangelist emisnug's Avatar
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    Probably basic, but...

    Solidworks flow simulator - something I really have no idea how to operate properly. Does anyone have any tips on how to get a realistic flow pattern?

  2. #2
    Insider PBSteve's Avatar
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    This takes a lot of time to get right. I'll write up a few tips when I get home tonight.

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    Adobe Evangelist emisnug's Avatar
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    I'm certain it does - I have a very very basic idea of how it works, but nothing beyond what my math skills (which haven't been used in earnest for about a decade) can tell me.

    Cheers Steve

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    Insider PBSteve's Avatar
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    Okiedokie... Let's just dive right in, shall we? It should be noted that this is as much an art as it is a science, so keep that in mind as you go along.

    To start, you need a model. You can use an assembly, but I find it easier to just make a part that represents your assembly. You can do this either by saving them as a part, or by building a new part with the appropriate cavities, or by inserting files, etc. I would recommend getting rid of any tiny parts of the cavity (o-ring glands and associated clearance dimensions especially). One of the big downfalls of the Flow Simulator in Solidworks (IMO) is that it can't simulate moving parts - so no valves closing, and no paintballs going down the barrel. Bummer.

    Anyway, you don't really need to know the details of the CFD solver to use it. There are technical papers out there which go through all the equations which I've skimmed, but to be honest there's not really a clear connection between the math stuff and what's going on in the user interface. If you're doing stuff that requires immense detail it could be useful, but IMO this is simple enough to pretty much ignore things.

    Here's a video I used to learn how to work a "transient" analysis, which IMO is the best for a paintball related application. There are a few things they don't go into so I'll cover those below.



    I actually totally neglected the table-driven valve deal, but whatever.

    For paintball, there are a couple tricks you can use. First, starting with a "solid volume" of air to emulate the shot chamber. You can do this using the "initial condition" property in the input data of your simulation. Create a solid body that represents the initial volume of your shot chamber (I've heard you can do this "within Flow Simulation, under Check Geometry, there is an option to save the fluid domain as a solid body"), then indicate that body on your initial condition, and set to the appropriate pressure.

    Another, and I think this one is pretty important, is to use "local mesh" to get the mesh fine where you want resolution, instead of using the adaptive mesh. If you use the adaptive mesh, your simulation will likely just explode (mine often went from being 2-3 hours to 72+ hours after one mesh refinement).



    Practice meshing before you do anything. Start as coarse as possible and make it finer until you think it's appropriately fine for the resolution you want and the computational power you have available. I would recommend trying to get at least 3-4 cells across any important orifices.

    I'm being a bit vague here because there is an immense amount of information on the solidworks website that I can't hope to cover - I highly recommend finding a video like the one I posted above and working through it using the solidworks help files and on the forums.

    http://www.academia.edu/3713889/Soli...-2012-tutorial
    Last edited by PBSteve; 10-01-2014 at 12:57 PM.
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  5. #5
    Adobe Evangelist emisnug's Avatar
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    Well, I've spent the weekend working through all of this and a few tutorials I found online - Steve, you've been a massive help! Cheers!

  6. #6
    Insider PBSteve's Avatar
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    Great, glad I could give you a place to start.
    Ever so many citizens of this republic think they ought to believe that the Universe is a monarchy, and therefore they are always at odds with the republic. -Alan Watts

    I work for the company building the Paragon

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