More HGDT crap (HGDT vs. Latke, the rematch)

[D_Hall]

For those who aren't allergic to reading, I would invite ya'll to visit the HGDT site (see link in my sig), go to the "Design Library," and check out what I've got to say about the L1 and L3.

For those who don't like reading, here are the pretty pictures.






Comments?

[biggsauce]

Whats the verdict? Has the "knee" been explained?

[D_Hall]

Jimmy,

In the other thread you pointed out how poorly HGDT was doing against your standard gun. You said your gun chronos at 300-330 fps while HGDT sim'ed you at (IIRC) 240.

Well, I'm still a bit slow, but it's a lot better (and I can get it over 300 if I play around)....

It is rather odd, though. I used the data from your technical gun (closed chamber experiments) to arrive at flame accelerations and such. If there's ANY gun HGDT ought to model well, it'd be your's.

[D_Hall]

Whats the verdict? Has the "knee" been explained?

No, but it does show up in all the Latke data (to varying degrees).

[D_Hall]

It is rather odd, though. I used the data from your technical gun (closed chamber experiments) to arrive at flame accelerations and such. If there's ANY gun HGDT ought to model well, it'd be your's.

Last night while I was laying in bed I think it hit me...


I used the technical gun data to study the static chamber flame accelerations. I did NOT look at those shots with the fan on (d'oh!). OK... Need to go back and re-examine fan-on scenarios.

Note: It is pretty obvious (to me) that it's a flame acceleration issue based on two things.

1) Throw in a multiple igniters and your gun models fine (so I just need to burn the propellant faster!).
2) I'm handling the Latke L1 very well... and while we don't know for sure I suspect it to be a static chamber at the time of firing.

[jimmy101]

D_Hall

You are getting all three of Latke's chamber / ammo combinations essentially perfectly. The small disagreements look to be well within the accuracy (shot to shot variability) of Latke's data.

...and while we don't know for sure I suspect it to be a static chamber at the time of firing.

You mean you believe the fan was off and the gases more or less stationary when the gun was fired?

Let me dust off my "standard gun" and chrony it again. I'll measure the spud masses and try to get a rough measurement of the static and dynamic friction as well.

[D_Hall]

You mean you believe the fan was off and the gases more or less stationary when the gun was fired?

Yes.

Let me dust off my "standard gun" and chrony it again. I'll measure the spud masses and try to get a rough measurement of the static and dynamic friction as well.

That'd be much appreciated.

[SpudFarm]

i will get to you with some results on PM on the GB hybrid when it is done.