A simple whirlpool

I got this idea from an animation I saw on Youtube a couple days ago. I was curious about what would happen if I made some sort of propeller in the bottom of a pool of fluid. The fluid mesh resolution is at 120.

I have an improved version rendering right now, I should have it up tomorrow afternoon. This one doesn’t actually develop into a whirlpool (the duration is just a hair too short), but you can see the beginnings of one.

I am pretty new around here, so chances are that this has been done before, but I thought it was cool enough to show you guys. Enjoy!


Warning: The better the vortex gets, the more unstable the fluid simulator is.

5 MB .avi

Wow, after seeing your animation, I think I might need to speed up my propeller. Maybe I’ll give her a go again today.

30 frickin’ hour render time FTL.

Well, like I said, the fluid sim becomes very unstable. I wasn’t able to bake that over res 80, and it took FOREVER even though I have plenty of resources. (Close to a day for 100 frames as I recall…)

P4 3.2 Ghz hyper-threading
2 GB DDR2 533 Mhz

My prop is spinning at 3,000 rpm, which is 2 full rotations per frame at 25 fps.

Crap, my new render didn’t finish before I left work. I’ll have it Youtubed 1st thing in the morning. Priorities. . . :wink:

My prop goes 90 degrees every 10 frames, at 25 FPS, so it’s much slower than yours, weighing in at about 37.5 RPM. For the last like 4 seconds of the simulation, I hit the nitrous button and double the rotational speed. I turned the fluid resolution down to like 110, and did a start - end time of 0 and 0.40. We’ll see how it comes out in the morning.

I just started experimenting with an SSE2-optimized build, and it is a motherf%&kin’ GODSEND! I think my render times are down by like 20% using that. Someday when I get a real job I’ll have a super quad-core beast, and get my render times way down.


Ok, my second attempt is up. I am going to try to make a tubular obstacle to contain the water for the next one, I think that the square domain is killing the whirlpool action. You can really see the mega turbo nitrous action at the 10 second mark. Some really scientific stuff happens.

Enjoy! :ba:

4th try, not much improvement. I think I need to try a couple different things like increase the speed of the fluid and increase the fluid resolution.

A differently-shaped propeller might help, too. Here is the video:

I hope this method for making a whirlpool ends up being useful for some really awesome effect someday. . .

nice to look at, but really a strange effect at the end of the vid. :confused:

5th try, and there is definitely a relationship between mesh size, prop speed, and start-end time. In this setup, mesh resolution is 150, prop speed is 75 RPM (90 degrees every 5 frames, 25 FPS), and start-end time is 0.0 - 0.60. Other settings (realworld size, viscosity, compressibility, etc) are still default. Also, I moved the propeller up a little bit. If I go for a 6th try, I will likely keep the prop around 75 RPM instead of varying it since it looked like it was working before it goes balls to the walls and screws everything up.


The video and audio and video are out of sync in the last half, but I might suggest this video tutorial I made to get a better handle on start and end times. Basically right now you’re only simulating .6 seconds of fluid motion.

A vortex vid on Youtube

Really cool effects to look at. If only it was longer… :wink:

Why do you keep abruptly increasing the speed of the “propeller”? It’s disrupting the forming whirlpool. The propeller also needs to be shaped with a little more dynamics in mind. Right now it’s just a block.

Would it be easier to achieve this effect by placing the motivating object at the top of the water? This would simulate a spoon stirring a glass of water and would require much less “energy”.

o ------- O

the little “o” represents the centerpoint of the “O” object that rotates around the within the fluid.

Just some thoughts.