Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 60 users online :: 6 registered, 0 hidden and 54 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], MCRKilljoy, MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Just bought some new software...

All non-spudgun related discussion goes here such as projects, theories, serious questions, etc. All "off-topic" posts (aka useless posting, determined by moderators) will be removed.
Sponsored 
  • Author
    Message

Unread postAuthor: D_Hall » Mon Jan 18, 2010 3:57 pm

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

Sure, if it existed as a program of record. It doesn't as the sim itself wasn't funded (just the testing). It didn't work worth a damn anyways. Not worth your time.

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.

LGGs are regulated under ITAR. As such, it would be illegal for it to be sold in a useable condition. So... You really in the market for an LGG that's been cut up with a cutting torch or similar?
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1760
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Unread postAuthor: ramses » Mon Jan 18, 2010 6:13 pm

D_Hall wrote:LGGs are regulated under ITAR. As such, it would be illegal for it to be sold in a useable condition.


Wow. Mentioned by name... Reading through the list, some stuff seems to be ridiculous... bearings and bearing systems. CNC-adaptable machines.... Bismuth over 99.98%... Vacuum valves... What the heck?

Also, that is international traffic in arms. I live in the states. Does that change anything?
So... You really in the market for an LGG that's been cut up with a cutting torch or similar?


could you weld on some flanges while you're at it? :D

Or add a 6" porting poppoff valve to keep things under 2Km/sec, that I/we can weld shut later?[/i]
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

Unread postAuthor: Ragnarok » Mon Jan 18, 2010 6:40 pm

psycix wrote: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.

As far as I know, GGDT actually uses timesteps of 10 us. It just happens that the graph only plots every 25 timesteps, with straight lines between them.

D_Hall will need to confirm either way, but I believe that what you see on the graph is not indicative of the timesteps used in the actual simulation.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: D_Hall » Mon Jan 18, 2010 9:30 pm

Ragnarok wrote:As far as I know, GGDT actually uses timesteps of 10 us. It just happens that the graph only plots every 25 timesteps, with straight lines between them.

D_Hall will need to confirm either way, but I believe that what you see on the graph is not indicative of the timesteps used in the actual simulation.

Correct. Plotting EVERY point results in ridiculous memory requirements so it only plots... yeah, every 25th point.
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1760
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Unread postAuthor: D_Hall » Mon Jan 18, 2010 9:36 pm

ramses wrote:Wow. Mentioned by name... Reading through the list, some stuff seems to be ridiculous... bearings and bearing systems. CNC-adaptable machines.... Bismuth over 99.98%... Vacuum valves... What the heck?

A lot of those kinds of things show up when the ITAR folks look at the shopping list(s) for those building nuclear weapons (that's how LGGs end up on the list).

Also, that is international traffic in arms. I live in the states. Does that change anything?

For a straight up purchase? Sure, it changes everything. But for a government auction, I believe the regs say that anything going out on an auction that shows up on the ITAR list must be damaged beyond repair before it is auctioned.
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1760
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Unread postAuthor: rp181 » Mon Jan 18, 2010 9:57 pm

so how is beyond repair defined? :roll:

So your auctioning...junk/scrap?
  • 0

User avatar
rp181
Brigadier General
Brigadier General
 
Posts: 1090
Joined: Thu Dec 13, 2007 8:47 pm
Reputation: 0

Unread postAuthor: D_Hall » Mon Jan 18, 2010 10:04 pm

rp181 wrote:so how is beyond repair defined? :roll:

Usually it involves cutting torches and components that require precision fit. For example, in a gun, the spec might call for the first 10% of the barrel to be cut longitudinally. Could it be repaired? Sort of.... But anybody who could repair that has demonstrated the tech to build their own.

Radar dishes are required to be smashed so that they can no longer focus a beam. Again, if you have the knowledge/equipment to repair it, you have the knowledge/equipment to build your own.

So your auctioning...junk/scrap?

In general? Yeah, we auction a lot of scrap metal. Last year they took something like 50 tons of it out of my facility alone. In this particular case, however, all you're seeing is the wishful thinking of some members. The project may be scrapped, but the gun won't be (it'll just be put in a warehouse until the next time it's needed....which is were it came from this time).
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1760
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Sponsored

Sponsor
 


Unread postAuthor: ramses » Mon Jan 18, 2010 10:13 pm

Yeah, That was wishful thinking. I need to get a job...
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

Unread postAuthor: Ragnarok » Mon Jan 18, 2010 10:14 pm

D_Hall wrote:Correct. Plotting EVERY point results in ridiculous memory requirements so it only plots... yeah, every 25th point.

You see, unlike some people, I do read and remember what others say on the forums.

I would suggest that you could try fixing it with a "below X timesteps simulated, plot every 10th point" situation, but I'm guessing you simply tell it to put aside the data from every 25th time-step as it's calculated, and you don't know how many timesteps you'll be using in advance to be able to do that kind of thing.

Given that GGDT will run up to 25,000 timesteps before giving up, that's already 1000 datapoints to store, so I don't blame you for only going that far.

That said, what about having some kind of sliding scale? That is, it stores every 10th timestep up to the 200th, then every 20th up to the 1000th, then every 50th up to the 2000th, then every 100th after that.
That would get rid of the "squared" off graphs if you're only plotting a couple of milliseconds worth of data points, but would also dramatically reduce the demands of storing the data from a lengthy simulation.

Whereas you can expect to be storing 800 data points from 20,000 timesteps, changing to a system like the above would cut that dramatically to just 260. (A further cut off to every 250th step after 10000 would make it just 200).

The graphs would look better, and the maximum memory required would be cut - there would be a minor increase in calculation time from the additional sorting out to do, but I think that would be relatively insignificant.

Of course, the uneven steps could make the export files look bloody funny. It's also extra work to fix a relatively minor aesthetics problem. Perhaps not my best idea.

Anyway, I'm rambling again.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: psycix » Tue Jan 19, 2010 7:36 am

Who cares if calculation takes 1 second or 5 seconds. I just want accurate results.
For plotting piston opening, an interesting graph if you ask me, you might want to put out every 5th step.

Computers are getting more powerful by the day, and GGDT tuned to the max will at most take 15 seconds on a crappy PC. On my PC it does it withing one second.
Even if it takes 15 minutes, who cares?

Maybe have an option to switch between "quick" and "accurate". Quick does it in a second like it does now, and accurate will spend a lot more time for optimal quality, plotting every 5th step, making the short timespan graphs surrounding the valve opening more useful.
  • 0

Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
psycix
Donating Member
Donating Member
 
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands
Reputation: 0

Unread postAuthor: jimmy101 » Tue Jan 19, 2010 11:09 am

One solution to the flattened graph problem is to just spline fit (or parabolic fit) the data. I would bet that just about any type of three point fit would make a graph that is within the plot line width of the original data. Easy enough to off load that fitting to the graphing routine. Computationally it would take basically zero time.

It's probably to late and you are committed to .Net, but Java (or JavaScript) is pretty portable across platforms. A GUI is easier to do in Java and graphing is pretty straight forward. It would be a bit slower but personally I don't think speed is an issue with HGDT or GGDT. Heck I run them on a creaky old win98 computer.


Does HGDT use the flame speed formula, IIRC, v=k(P^alpha)(T^beta)? I've been looking at my old models and I am starting to think that the P isn't pressure, it should be density (rho?). It doesn't make a huge difference in the calculation results but ... I suspect that in the original usage it is indeed pressure but because of how the speeds were measured as a function of T and P the term basically ends of being density and not pressure. In a close chamber the "p" term is constant during combustion because it is really the gas density (or related to the gas density).

How about including flame speed (or pseudo flame speed) as an input to HGDT? Be interesting to try to model MAP, hydrogen, acetylene and other fuels with a faster burn rate then propane. I suppose that would mean you would also have to include the heat of combustion and the stoichiometry. So it's probably more trouble than it is really worth. Still, a second tab with all those hidden values for advanced users?
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3130
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Previous

Return to Non-Spudgun Related Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], MCRKilljoy, MSNbot Media, Yahoo [Bot]

Reputation System ©'