Gravity waves in US?

[smjjames]

I've seen this effect when I put a disk around the sun with mercury and have velocity view on, the velocity sort of 'pulses' with mercuries orbit. I didn't think too much of it until I saw what was happening with my most recent experiment with dust and gravity. Watch the lower left leading edge of the dust swath, the time step is actually one day and the film mode took about three minutes, so it's sped up somewhat. As you can see, the velocity pulses and I think it may have been happening to the closer in lobe. When I saw this, I thought of what I observed with mercury.

So, is it gravity waves (although maybe closer to a a ships wake) or some other quirk of US?

I hope you guys don't mind if I have Photobucket host it.


Also, how do I get the movie mode to get the UI to show? Or maybe I'll just use Fraps, now that I have it.

[pyxxel]

Sorry but I'm not sure what I'm looking at here... 

[smjjames]

I'm not exactly sure what I'm observing here either.

[Bogdan45]

I see colors on the edge shifting, is that  what you mean?

[smjjames]

Yes, that's the velocity indicator mode.

Would have been better if I had the save, heh, it failed when I attempted to put a ? in the save name, would have helped if the error string didn't extend off the screen. Still, it's pretty easy to make. I used the solar system with planets and dwarf planets, removed Pluto and Eris, line the planets up (I put a temporary vertical ring around the sun to help line them up), put geosynchrous rings around each planet with an outer diameter of 1 AU. Or possibly just put them around the inner planets, Ceres, Jupiter and maybe Saturn since the ones I put around the three outer gas giants had barely deformed by the time I had recorded this. I had the sim on 1 hour timestep for a while and then put it on 6 hours and later one day timestep.

Anyways, it's possible I'm misunderstanding or misinterpreting some physics mechanics in US as far as what I'm observing.

[vh]

Oh, that happens when the time step is a bit too high iirc.

go to 0:55 of this to see...I did that with a galaxy http://www.youtube.com/watch?v=9CZhMA12rt0#t=0m55s

[smjjames]

Oh I see, so it's just the simulation trying to get the dust to catch up? It's just a quirk of the programming math behind the physics and the usual problems with timestep when you have it set too high.

[vh]

No. Its the dust accelerating and slowing down because the orbits are changing size, which can happen when the time-step is too high, but it could also be caused by elliptical orbits and etc.

[smjjames]

Well, mercury does have a somewhat elliptical orbit (compared to Earths and Venus's orbits) and it is at an angle. I think what I was seeing with mercury could have been when it was diving into the plane of the ring itself, making an effect like that of a boats wake or a pressure wave.