Jump to content
874604650

Vortex Cloud Simulation

Recommended Posts

I solved the problem with divergence~~~but any better solution to do vortec cloud?? thank you

Share this post


Link to post
Share on other sites

This is likely a result of linear/tangential velocity increasing while the centripetal force remains the same.

The equation F=mv2/R, where F is centripetal force, m is mass, v is linear/tangential velocity, and R is the radius, shows that if F and m remain constant and v increases then the radius must also increase.

Linear/tangential velocity increases because the force(s) acting on the smoke cause an acceleration, which is why it starts moving in the first place.

I haven't tested this, but if you decrease the force(s) causing it to spin it will take longer to get up to the speed you want, but then I think it will settle at a smaller radius.

  • Like 1

Share this post


Link to post
Share on other sites

Whether to reduce the radius to extend the life? 

Share this post


Link to post
Share on other sites
On 2020/7/21 at 12:41 AM, eimk said:

This is likely a result of linear/tangential velocity increasing while the centripetal force remains the same.

The equation F=mv2/R, where F is centripetal force, m is mass, v is linear/tangential velocity, and R is the radius, shows that if F and m remain constant and v increases then the radius must also increase.

Linear/tangential velocity increases because the force(s) acting on the smoke cause an acceleration, which is why it starts moving in the first place.

I haven't tested this, but if you decrease the force(s) causing it to spin it will take longer to get up to the speed you want, but then I think it will settle at a smaller radius.

Wow!thank you,I think I should increase the centripetal force as much as the rotational force increases

Share this post


Link to post
Share on other sites

I don't know what your setup is, but if you keep the forces constant eventually they will balance out with air resistance and the velocity will become constant too. If the forces keep increasing the sim could get chaotic and difficult to manage.

Share this post


Link to post
Share on other sites
7 hours ago, eimk said:

I don't know what your setup is, but if you keep the forces constant eventually they will balance out with air resistance and the velocity will become constant too. If the forces keep increasing the sim could get chaotic and difficult to manage.

here is my file and cache thank you. 

odforce.rar

Share this post


Link to post
Share on other sites

My computer doesn't have enough RAM to run your sim without Houdini crashing, but my best guess for what could help would be decreasing the strength of your velocity field and/or adding a drag force. Alternatively you could look into the vortex force node, which might be easier to work with than your current setup.

https://www.sidefx.com/docs/houdini/nodes/dop/vortexforce
https://www.sidefx.com/docs/houdini/nodes/sop/vortexforceattribs.html

Share this post


Link to post
Share on other sites

You are running a pyro sim, which by default aims to make the velocity field divergent free. The velocity field that you have set up is clearly not non-divergent. You are trying to push all the smoke toward the center (i.e. the field's divergence is strongly negative in the middle). So when the pyro sim tries to make the velocity field non-divergent, it has to modify the velocity field near the middle to push the smoke out and away from the center. What you did by specifying the target divergence field is correct. You are telling the pyro sim to make the velocity field's divergence negative in the middle, rather than zero everywhere, which will give you the effect of pushing the smoke toward the middle.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×