Pressure question

[velocity3x]

You missed the unquote by the way.

Yes I did but..... I did get the pressure / force question correct.

[Davidvaini]

make sure you run GGDT as administrator..sometimes that error will come up if you dont.

and if you cant run it as administrator, ask your parents for permission.

[Gun Freak]

We all have administrative privledges or whatever.

[btrettel]

Gun Freak, have you tried my suggestion? The thread below I believe contains the relevant information. If not, try the other ones that come up in the search I mentioned.

http://www.spudfiles.com/spudtech_archi ... f=1&t=3154

[D_Hall]

It is the premiere tool for gas gun design.

To be fair, I think it's more accurate to simply refer to it as the most popular.

Jimmy101 and Btrettel both put out codes that are every bit as good as GGDT(*). And I believe they're open source for those who want to look at the guts of such programs.




(*) And possibly better for transonic. I know Btrettel is workign that issue harder than I did when I was writing GGDT. Although I'm prepping for a full rewrite...

[velocity3x]

Although I'm prepping for a full rewrite...

D_Hall
I recently had use of some radar equipment and operators. For laughs, they tracked my golf ball cannon. I fired 5 shots ranging from 685-1194.22 fps. I entered the firing psi into GGDT after each shot and GGDT predicted the velocity to be only 3-7 fps slower than the actual shot. If GGDT has a problem.... it wasn't apparent in my tests.

[CpTn_lAw]

Yup, you did a great job writing those programs D_Hall. HGDT works great , GGDT works great. What language did you write it in?

[Gun Freak]

Gun Freak, have you tried my suggestion? The thread below I believe contains the relevant information. If not, try the other ones that come up in the search I mentioned.

http://www.spudfiles.com/spudtech_archi ... f=1&t=3154

I did everything they said to do on that thread except the one about right clicking on the ini file. Where is that file? It's not in the GGDT folder for me.

[CpTn_lAw]

Right click ==> Run in compatibility mode ==> windows vista.

[Gun Freak]

I got it to run... finally. What does "barrel choking flow" mean?

[D_Hall]

I got it to run... finally. What does "barrel choking flow" mean?

It means that the choke point in your flow isn't in the valve (which is often the case), but rather in the breech of your barrel. This is actually a good thing, but it also means that upgrading your valve will not result in better performance.



edit(s)....

@Velocity: Thanks. It's rare to get reliable feedback.

@Cptn: Again, thanks. I wrote it in Visual Basic 6.0 but don't imagine for a second that was my preferred language. It just happened to be the development environment I had lying around so I used it. Historically, I'm an ANSI C guy (I loooove C). So I've purchased MS Developer's Studio 2008 (which includes Visual C++). I've not a lot of experience with non-ANSI compliant C so there'll definitely be a learning curve, but there are so many things that I would like to do with the code that I simply don't know how to do in Visual Basic but would be trivial to do in C.

[Gun Freak]

but rather in the breech of your barrel.

My barrel does not have a breech, it is a co-ax.

[Ragnarok]

My barrel does not have a breech

So it's a barrel with only one end?

In this sense, breech is being used as a term for the non-muzzle end of the barrel. It might typically refer to breech loading, but what else would you call "the other end of the barrel"?

[Gun Freak]

So is it being choked because the ammo or what?

[D_Hall]

So is it being choked because the ammo or what?

It's being choked because that's where the flow chokes. That's what fluids do in non-trivial pressure differential driven flows; they choke.

Beyond that, I'm not sure what to say... You haven't the education to understand the explanation. Or perhaps I'm a bad teacher. Anybody got a super-basic explanation for the concept of choked flow?