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Unread postAuthor: D_Hall » Sun Jan 17, 2010 7:09 pm

rp181 wrote:I say smush (what a great word...) HGDT and GGDT together for a single utility.

That one will probably happen as well.

Also plan a 3rd utility to model springers (they should be simple enough to model...why not do it?).
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Unread postAuthor: niglch » Sun Jan 17, 2010 7:46 pm

Here are some things I have thought about:

Define a custom fuel by specifying its properties (heat and rate of combustion and whatever else is relevant in the model). This could work for people who want to see how some weird fuel would work (like hydrogen, methane, etc.) in their design. A way to control the % oxygen in the fuel mix would be useful too.

Display graphs of multiple gun designs on the same plot for comparison. A feature to export the graph into an image would also be nice.

For hybrid guns, a "piston" option might be good (instead of just burst disk). You would need to specify the surface area of the piston faces, piston weight, and the spring pressure behind the piston.
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Unread postAuthor: MrCrowley » Sun Jan 17, 2010 8:07 pm

Maybe have '1" Sprinkler Valve' as an option under valves and when selected it automatically fills in some of the parameters (but not pilot volume or Vent diameter for exapmle). Just saves time I guess.

It's not for me, but for new members who always get told to go to your site, download GGDT and then they have no idea what to put for a sprinkler valve.
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Unread postAuthor: rp181 » Sun Jan 17, 2010 8:48 pm

I think if some people came up with sets of data, D_Hall could easily implement presets.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 17, 2010 10:02 pm

D_Hall wrote:Sabots are definitely on the list.


Good to hear :)

Some presets for commonly used sprinkler/QEV valves would also be helpful for those with little experience.

Also plan a 3rd utility to model springers (they should be simple enough to model...why not do it?)


It would be hard to take dieseling into account, so that would probably be useful only for small airsoft style projects.

Here's an ambitious suggestion, is there a way to combine data input with dewey-1's amazing 3d models in order to create a vague visual representation of the launcher, assuming the use of standard fittings?
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Unread postAuthor: JDP12 » Sun Jan 17, 2010 11:24 pm

Overall I'm pretty hAppy with the both, but yes saboted projectiles would be nice, as that is my current project. ( dumping a semi auto gun for advancements on my combustion)
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Unread postAuthor: frocksie » Mon Jan 18, 2010 12:49 am

Like niglch said, a piston valve option in HGDT would be very helpful.

Also, would it be possible to model elbows and other elements that change the direction of airflow instead of an inline cannon?
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Unread postAuthor: Davidvaini » Mon Jan 18, 2010 1:08 am

perhaps we could put our minds together on this project D-hall...

I am a programmer myself, I created the co2 fill calculator. It doesn't exactly go with GGDT, but is very useful for people wondering what pressure a certain sized pipe at a certain temperature would be from a certain amount of co2.

Perhaps a new easy to use interface, Tab system or something.
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Unread postAuthor: spudamine » Mon Jan 18, 2010 2:51 am

I'm liking the sabots as well.
An option to save the output as a .txt file for import into excel (or some other spreadsheet). would allow plotting multiple performance graphs together amongst other things.
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Unread postAuthor: psycix » Mon Jan 18, 2010 8:01 am

The possibility to enter "X-Y" (X and Y being numbers) in one field (only one field, two will error!*) and it will draw a graph of all results for values ranging from X to Y.
For example I enter 10-80 in projectile mass and select kinetic energy as the result. Then it should draw a graph with mass on the X axis and KE on the Y axis.

*Two fields would be possible too, giving a three dimensional graph and something for your CPU to do (multicore support?).

Another thing I would like to see is a manual step size of time in the simulation, setting a longer and heavier calculation and being more accurate or, a shorter, less accurate one.
In GGDT I often see a graph made of straight lines shaping a curve, smaller steps would produce a smoother, and thus more accurate curve.

Valve presets should indeed be added for the ease of use.
With a bit of research and measuring one should be able to find the seat diameter and flow coefficient of a valve.
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Unread postAuthor: ramses » Mon Jan 18, 2010 10:09 am

I would like to see a "Sensitivity studies" option in GGDT. I find it much more useful than the optimization tool that is included in GGDT.

It would also be somewhat helpful to set different units independently for every measurement. (bore in mm, barrel length in feet, etc.

I also like psycix' idea about the graphs, and the valves. It would be a good idea to have an option to hide the presets so that experienced users using custom valves wouldn't have to sort through a whole bunch of stuff to find what they are looking for.


Will you be releasing the light gas gun simulator here also?
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Unread postAuthor: btrettel » Mon Jan 18, 2010 10:27 am

A lot of the ideas mentioned here are pretty good. The presets idea could be very helpful to newbies.

Also, would it be possible to model elbows and other elements that change the direction of airflow instead of an inline cannon?


Any flow restrictions from a gas chamber to the barrel introduced would be captured by the right flow coefficient. The flow coefficient really is a fudge factor as it depends on more than the valve flow; other elements and the pilot valve will definitely affect it.

However, this doesn't account for energy losses through the fitting. As far as I know, GGDT never did, and I'm not certain if accounting for energy losses would make any significant difference. This was something I was considering investigating. You're welcome to investigate yourself D_Hall.

Another thing I would like to see is a manual step size of time in the simulation, setting a longer and heavier calculation and being more accurate or, a shorter, less accurate one.
In GGDT I often see a graph made of straight lines shaping a curve, smaller steps would produce a smoother, and thus more accurate curve.


Unless the computer has infinite precision, smaller step sizes could actually be less accurate. Round-off error could accumulate and easily be larger than the "truncation" error (the error associated with using a numerical method in the first place). So don't go overboard... but this would be an neat feature to have.

Also, depending on what approach D_Hall's takes for parts, there could be some severe restrictions on the time step. These would have to be made clear in the interface. One common one (if he makes a PDE solver for accuracy at higher velocities) is the CFL condition, and there usually are other conditions on top of that.
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Unread postAuthor: D_Hall » Mon Jan 18, 2010 10:44 am

spudamine wrote:I'm liking the sabots as well.
An option to save the output as a .txt file for import into excel (or some other spreadsheet). would allow plotting multiple performance graphs together amongst other things.

And again, the existing versions already have this (file->export).

Will you be releasing the light gas gun simulator here also?

No, Uncle Sam paid for that so (unlike the codes I wrote on my own time) I can't just release it on a whim. Besides, the last time I touched it it didn't work worth a damn (project I was writing it for was canceled so it was a moot point to keep tinkering... And for the future I think I'm going to advocate we get a new gun).
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Last edited by D_Hall on Mon Jan 18, 2010 11:57 am, edited 1 time in total.
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Unread postAuthor: D_Hall » Mon Jan 18, 2010 10:49 am

[doh]
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Unread postAuthor: ramses » Mon Jan 18, 2010 2:09 pm

D_Hall wrote:No, Uncle Sam paid for that so (unlike the codes I wrote on my own time) I can't just release it on a whim. Besides, the last time I touched it it didn't work worth a damn (project I was writing it for was canceled so it was a moot point to keep tinkering... And for the future I think I'm going to advocate we get a new gun).


I suppose I will just need to get off my ass and attempt to learn programming and fluid dynamics. But first I need access to a computer with more than 128mb ram, and a processor faster than 866mhz...

Since the project was canceled, wouldn't the code be releasable?

And if you get a new LGG, will the old one be sold at a government surplus auction? I bet if everyone on this forum pitched in, we could buy it.
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