Wind Tunnel Simulations


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    Default Wind Tunnel Simulations

    Are there any SolidWorks users here that are far enough along in experience to answer a question or two about setting up a wind tunnel simulation for an upcoming project I'll be working on soon?

    First off, I've watched several YouTube videos on the subject and I do have a very basic understanding about how to go about it but, beyond that the videos I've watched have been produced by knowledgeable individuals that happen to have such thick accents that it's hard to understand all of what they are saying. Other videos on the subject are formatted so that there is no voice-over whatsoever so they are obviously targeted to those who already know enough about the subject to understand what all the mouse clicking is about. I can't read minds and I can't understand much of the heavily accented narration that comes along with what otherwise appear to be informative made videos.

    I'm trying to set up a wind tunnel simulation for an air gun pellet design. I need to see how the air will flow around and past my pellet designs at various velocities. I've heard and read that it's not possible to impart the simulated spin that the pellet would have while in flight but I don't know if this is true or if the extent of experience of the blog or video author is such that they personally don't know how to digitally impart that spin. It may be that the older version of SolidWorks that I'm working with will not allow for this but, no matter. I'm sitll hoping that one of our more experienced SolidWorks guys might be able to chime in or maybe give me an internet link to some clearer information on this particular aspect of SolidWorks.

    Thanks in advance.

    MetalShavings

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    Default Re: Wind Tunnel Simulations

    Do you have a precise accurate 3D model?
    Anything special about a sphere i need to know?
    Surface finish?
    How about just making them and physically testing?



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    Default Re: Wind Tunnel Simulations

    Quote Originally Posted by bostosh View Post
    How about just making them and physically testing?
    Some Schlieren photography equipment would be fun to setup! Bet it would be cheaper to model the problem for the most part. Can a air gun round have a boat tail?



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    Default Re: Wind Tunnel Simulations

    Quote Originally Posted by bostosh View Post
    Do you have a precise accurate 3D model?
    Anything special about a sphere i need to know?
    Surface finish?
    How about just making them and physically testing?
    All common sense questions but, the reason for wanting to find out how to go about this is because although I do have a basic model designed, I want to be able to set up the wind tunnel so that I can tweak that basic design as many times as I need to in order to get it to the optimum ballistic coefficient for the given velocity levels of the particular air rifle I'll be using to shoot them with.

    The surface finish is one of the features to be tweaked. Since they'll be made of cast or swaged lead I'll be sticking to a smooth surface finish but if you are familiar with lead bullet/pellet casting or swaging, the "Lube-Grooves" or the Wasp-Waisted outside geometry can add as much to the surface finish as any kind of texturing might add. I was kind of afraid that this was going happening when I posted my initial inquiry. I was afraid that my initial question would be misconstrued and the specific subject at hand would start to go off in the wrong direction.

    What I really want to know is if it's possible, within the SolidWorks CAD software to simulate the spin that my pellet will have as it flies through the air? By being able to simulate that spin, along with the air flowing around that pellet in flight, I'll be able to better tweak the surface geometry of my pellet design.

    As far as making it first and testing it; Been There and Done That. It's a long and tiresome trial and error undertaking and for a small project like this it's just not worth it. This is why I thought I'd do my testing in a simulated wind tunnel using the SolidWorks CAD software.

    MetalShavings



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    Default Re: Wind Tunnel Simulations

    Quote Originally Posted by mountaindew View Post
    Some Schlieren photography equipment would be fun to setup! Bet it would be cheaper to model the problem for the most part. Can a air gun round have a boat tail?
    My particular design does incorporate an integral Boat Tail. Many will tell you that because of the slower velocities of an air rifle in general a Boat Tail will not yield enough benefit to make any real difference in the performance of the pellet. For the most part, these internet experts are just repeating what they've read from other self-appointed internet experts. They have no real hands on or first hand knowledge of this kind of stuff.

    I'm no expert either but I have done my due diligence in searching for some answers about bullet/pellet design which included reading the actual papers from the bullet designers and rocket scientist who come up with alot of these facts and figures. From what I've found, even the slower moving projectiles can benefit from a correctly proportioned and angled Boat Tail for a projectile moving within slower velocity windows. This is just another reason I'm trying to set up a wind tunnel simulation of my pellet designs. It would allow me to go back and tweak the Boat Tail angle and length to get it just right for the velocity window that my air rifle is shooting at.

    By the way, I've watched some YouTube videos using the type of photography you've alluded to and it looks cool as hell.

    Also; I'm a member of the SolidWorks forum on the SolidWorks website where I posted the same question. I have yet to get any replies there either so I won't be completely surprised if no one hear can offer up a yes or no answer. The main reason for asking my question here is because I know from experience that when a person doesn't have the training in such and such a software but still knows enough to use said-software, they are more likely to have found a work-around that will do the very thing that the experts said could not be done. Those who are formally trained in the use of the SolidWorks CAD software are by osmosis, also trained to believe in the limitations of that software. As such, they generally do not explore outside the box of their formal training. It's the self-taught goobers like myself who are to ignorant to know better that will try to find work-arounds for problems like this wind tunnel thing. I have yet to find that work-around so I though I'd ask here.

    MetalShavings

    Last edited by MetalShavings; 04-23-2018 at 12:31 PM.


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    Default Re: Wind Tunnel Simulations

    Hi-speed Photography of ball into a "cloud chamber" will leave a condensation/compression trail



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    Default Re: Wind Tunnel Simulations

    Quote Originally Posted by MetalShavings View Post
    My particular design does incorporate an integral Boat Tail. Many will tell you that because of the slower velocities of an air rifle in general a Boat Tail will not yield enough benefit to make any real difference in the performance of the pellet. For the most part, these internet experts are just repeating what they've read from other self-appointed internet experts. They have no real hands on or first hand knowledge of this kind of stuff.

    I'm no expert either but I have done my due diligence in searching for some answers about bullet/pellet design which included reading the actual papers from the bullet designers and rocket scientist who come up with alot of these facts and figures. From what I've found, even the slower moving projectiles can benefit from a correctly proportioned and angled Boat Tail for a projectile moving within slower velocity windows. This is just another reason I'm trying to set up a wind tunnel simulation of my pellet designs. It would allow me to go back and tweak the Boat Tail angle and length to get it just right for the velocity window that my air rifle is shooting at.

    By the way, I've watched some YouTube videos using the type of photography you've alluded to and it looks cool as hell.

    Also; I'm a member of the SolidWorks forum on the SolidWorks website where I posted the same question. I have yet to get any replies there either so I won't be completely surprised if no one hear can offer up a yes or no answer. The main reason for asking my question here is because I know from experience that when a person doesn't have the training in such and such a software but still knows enough to use said-software, they are more likely to have found a work-around that will do the very thing that the experts said could not be done. Those who are formally trained in the use of the SolidWorks CAD software are by osmosis, also trained to believe in the limitations of that software. As such, they generally do not explore outside the box of their formal training. It's the self-taught goobers like myself who are to ignorant to know better that will try to find work-arounds for problems like this wind tunnel thing. I have yet to find that work-around so I though I'd ask here.

    MetalShavings
    No expert either , not even a layman I do understand that little things can make all the difference in most disciplines. Combine enough of them and your out in front!
    I think a coke bottle waste allows you to move the shock wave for or aft of object I watch to much tv



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    Default Re: Wind Tunnel Simulations

    Quote Originally Posted by mountaindew View Post
    No expert either , not even a layman I do understand that little things can make all the difference in most disciplines. Combine enough of them and your out in front!
    I think a coke bottle waste allows you to move the shock wave for or aft of object I watch to much tv
    You're right, it does do that. It also imparts drag on the projectile in the same way the tail of a shuttle-cock maintains stability in the sport of badminton. As air guns have evolved, what this has left modern air gunners with are antiquated ammo designs that were really designed to be shot out of much slower velocity producing air rifles and pistols.

    What we have now days are cutting edge air rifles capable of producing velocities and impact energy comparable to .22 rimfire rounds and higher. Shooting conventional pellets at .22 rimfire velocities is not conducive to accuracy. It's like having a state of the art jet fighter being kept aloft by a propeller driven engine. There is a need for a re-vamping of air gun ammo that gets shot out of the cutting edge air rifles. There's nothing wrong with the pellets of yesteryear. I still shoot those too. It's just that they are no longer optimal when shot at the higher velocities now attainable, and it seems like the air gun ammo manufactures are reluctant to step up and improve on those 1st-generation pellet designs. It almost seems that they fear that their customers will completely abandon those 1st-generation pellet designs in favor of the more modern ammo.

    They may very well do that but only until they find out that the newer pellets generally won't perform well in the slower velocity air rifles.

    For the most part, the only ones trying to come up with better air gun ammo are lone-wolf tinkerers and boutique ammo manufactures.

    MetalShavings



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    Default Re: Wind Tunnel Simulations

    This is out of the range of SW. There are some CFD plugins that will cost you a pretty penny. You'll need a high end simulation package like NASTRAN. You can do quite a bit of CFD with some open source packages on LINUX. Just do some searching.



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    Default Re: Wind Tunnel Simulations

    Quote Originally Posted by warrenb View Post
    This is out of the range of SW. There are some CFD plugins that will cost you a pretty penny. You'll need a high end simulation package like NASTRAN. You can do quite a bit of CFD with some open source packages on LINUX. Just do some searching.
    I finally got some answers from some of the guys over on the SolidWorks community website pages. They seem to concur with your statement. I have absolutely no reason to believe you guys are wrong; especially since most folks who use any kind of CAD software are generally more experienced than I am. It does get confusing though when I'm able to find tutorials that claim to show how to go about doing a "Flow-Simulation" utilizing a moving model within a Wind-Tunnel. These videos look legitimate enough; the problem is that the person doing the presenting or talking on these videos has such a thick accent that they are barely understandable so it makes the overall tutorial a little confusing to anyone who doesn't already know what they are trying to teach.

    I mentioned this in my initial post. Some of the other videos on this subject that also appear to be legitimate as to how to go about this are made without anyone talking at all. It's just a bunch of mouse clicks and arrow pointing. These too are geared toward those who already know, or at least know way more than I do about this particular subject or techinque. I can just about make out what they are alluding to but, not quite. It's like having something right at the tip of your tongue but not quite being able to get a handle on it. I haven't given up yet. In the back of my mind I still believe that there is a work-around for this "Flow-Simulation/Wind-Tunnel" test. It's just that I have yet to discover it or the persons who have discovered a work-around.

    I seem to remember coming across the answer I'm looking for a couple of years back but at that time I had just gotten my hands on the SolidWorks software and I was doing alot of experimenting. I can't seem to find that information. I'm going to quit looking so hard and I think if I do that the information I'm looking for will just fall into my lap from out of nowhere. That's usually how these things happen for me.

    MetalShavings

    Last edited by MetalShavings; 04-28-2018 at 12:24 PM.


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