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Author Topic: Collision fragment ejection discrepancy  (Read 3443 times)

Prometech

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Collision fragment ejection discrepancy
« on: September 19, 2015, 12:36:10 AM »
I have no Idea what is happening with the trajectory of fragments in collisions, but there are these huge gaps that are quite evident where no fragments are ejected along a vertical line that is perpendicular to the direction of the bodies velocity which impacted.

EDIT: The images attached is of an impact with 15000 particles and 300 attracting bodies run at 3.5 Seconds per second.
« Last Edit: September 19, 2015, 12:59:19 AM by Prometech »

Arian

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Re: Collision fragment ejection discrepancy
« Reply #1 on: September 19, 2015, 01:28:14 AM »
Hmm, the gap in itself is actually not the strange thing. What seems wrong is the "butterfly" shape of the fragment ejection.
Depending on the impact angle you would expect a more or less round/oval shape with no (or very few) fragments going directly opposite to the projectile's velocity, which would make the gap. Those pictures show something I would expect from a head to head collision of a projectile hitting the brim of a disk that's thinner than the projectile's diameter with the disk "cutting" through the projectile.

Prometech

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Re: Collision fragment ejection discrepancy
« Reply #2 on: September 19, 2015, 02:55:26 AM »
I'll get some more images of this

C7

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Re: Collision fragment ejection discrepancy
« Reply #3 on: September 20, 2015, 10:11:53 AM »
Interesting, I'll forward this over to Thomas so he can take a look at it.

Greenleaf

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Re: Collision fragment ejection discrepancy
« Reply #4 on: September 23, 2015, 12:19:03 AM »
I have tried to recreate this error, but have not had any success.


Could you elaborate on the collision a bit? Is this a predefined simulation, or did you shoot something yourself? Which body impacted? Was it a grazing collision?
Anything else you can tell me?

Prometech

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Re: Collision fragment ejection discrepancy
« Reply #5 on: September 23, 2015, 11:16:51 PM »
Collision is at roughly 45 Degrees to the equator, the object colliding was ceres, moving at 20 KmH
I will recreate and save the simulation as well as take more screenshots for your use.
« Last Edit: September 23, 2015, 11:27:22 PM by Prometech »

Prometech

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Re: Collision fragment ejection discrepancy
« Reply #6 on: September 23, 2015, 11:28:38 PM »
Simulation is attached.
It was run at 1 Second per second with 16,000 non attracting bodies and 300 attracting bodies.

Greenleaf

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Re: Collision fragment ejection discrepancy
« Reply #7 on: September 24, 2015, 02:14:30 AM »
Thanks for the save. That made things much easier.
The issue here is the way fragments get pushed forward by the shallow impact angle while also getting ejected from the back part of the cratering. Essentially, material is pushed forward and material is ejected from the back, but nothing is ejected upwards, where the impactor itself is blocking. Apparently nothing is really ejected out to the sides, though, which is the real problem.


With a high fragment count, as you used, this doesn't look right, so I will need to see if I can tune it a little better.


Thanks for pointing it out

Prometech

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Re: Collision fragment ejection discrepancy
« Reply #8 on: November 17, 2015, 07:16:39 AM »
Has this been fixed?

Plutonium

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Re: Collision fragment ejection discrepancy
« Reply #9 on: November 18, 2015, 11:01:16 AM »