Obi Official Forum

Hello,

     I had a quick question regarding the 'atmospheric drag' parameter in the emitter blueprints. Since this is just one editable parameter, what exactly does the variable represent? Is it the drag coefficient? Density? Surface area? Or does it represent the actual drag force – and if so, is it dependent on velocity squared? I would like to create a relatively accurate simulation through the air, and drag is a rather large factor in that.

Thanks in advance!

F17

(28-04-2022, 07:40 PM)Freebird17 Wrote: [ -> ]Hello,

     I had a quick question regarding the 'atmospheric drag' parameter in the emitter blueprints. Since this is just one editable parameter, what exactly does the variable represent? Is it the drag coefficient? Density? Surface area? Or does it represent the actual drag force – and if so, is it dependent on velocity squared? I would like to create a relatively accurate simulation through the air, and drag is a rather large factor in that.

Thanks in advance!

F17

Hi there!

Athmospherig drag is a unitless drag coefficient, opposing the particle's velocity, and only applied to particles near the surface of the fluid. The implementation is done following this article:
http://gamma.cs.unc.edu/SPH_GAS/sph_gas.pdf

You can find the equation for the atmospheric drag force in page 4 (eq 14).
It's implemented in line 356 of the BurstDensityConstraints.cs file.

kind regards,

(29-04-2022, 09:51 AM)josemendez Wrote: [ -> ]Hi there!

Athmospherig drag is a unitless drag coefficient, opposing the particle's velocity, and only applied to particles near the surface of the fluid. The implementation is done following this article:
http://gamma.cs.unc.edu/SPH_GAS/sph_gas.pdf

You can find the equation for the atmospheric drag force in page 4 (eq 14).
It's implemented in line 356 of the BurstDensityConstraints.cs file.

kind regards,

Great, thank you so much!