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Dynamics - Fluid / Gaseous

Updated: Mar 28, 2022

Gaseous simulations are much like liquid simulations that they generally work with plugins such as FumeFX, Turbulence FD, X-Particles.

Gas simulations can interact with particles as well, and are basically created on fixed static 3d pixels called voxels that receives and transmits values.

Basically a cubic container is created - in which all the simulation takes place. The container itself is divided into virtual voxels.

For example, if we set voxel size as 1cm for a container of 100cmx100cmx100cm in size, that means we have 1.000.000 voxels in this container.


Every single voxel receives the values like Fuel, Burn, Temperature, Velocity etc. and transmits those values to the neighboring voxels.


Main difference from the other simulations is that what emerges is not a solid mesh/body, but a volumetric, renderable entity called you guess it, volume/volumetric.

Let's take a look at some of the main parameters.


Container/Sim. Area :

From here we can set the basic container size settings. Width, height, depth, voxel size/spacing, adaptive etc.

Voxel Size is the same as Spacing. The lower the value, the higher the resolution/quality, the slower the calculation.

Adaptive creates a dynamic container that encapsulates the voxels that take values ​​from the simulation, so that only the relevant sections are calculated instead of calculating the whole static container.

 

Since the titles can be very different and irrelevant according to the plugin, from this point on, let's proceed without a main title, parameter-based for a while for sake of not to mislead. When you see it, jump on it :


Combustion, in its simplest form, is the chemical reaction of burner and combustible materials at the ignition temperature . From the simulation side, some variable base values ​​or combinations may be required to reveal fire, smoke, etc., depending on the plugin like Fuel+Heat, Burn+Heat etc. Ultimately, simulation does not occur without heat in all add-ons. Although many use heat-temperature as substitutes, they are essentially different things.


Ignition Temp. : Sets the minimum temperature at which the fuel should ignite.


Buoyancy : Energy that rises fluid upwards. The higher the value, the faster the smoke or flame can travel up. Negative values ​​have the opposite effect. If there is a direction parameter, it determines the direction.

Vorticity : It adds a swirl-type motion pools to the fluid. The Radius value, if any, determines the radius of the vortex. It is necessary to lower the Voxel Size to get the detailed vorticity.


Diffusion : This parameter softens the heterogeneity or variability of parameters such as Temperature, Fuel, Smoke by scattering/blurring. Values ​​become more homogeneous, stable, and with less variation in value, a smoother curvature-free, turbulent-free rise simulation occurs.




No Diffusion


With Diffusion




Dissipation : Loss of energy. Fire, smoke, etc. will fade earlier.

Advection : In gaseous simulation, it prevents natural blurring in simulation and makes curls sharper. In particle simulation, its used for calculating and transfering gaseous values to the particles so they move more organically and interact with each other.


Propagation : Controls the expansion of the simulation. Explosions can be created and controlled by animating this value.


Shading : The shading of gas simulations is created by assigning the calculated channels (burn, velocity, temperature, density, etc.) to the Fire, Smoke parameters and adding ramps to these channels. It's usually built into the plugin. For example, if we ramp up the Density channel from yellow to red for fire, the places where the density is high (source point of the simulation) will be yellow, and places where it is low (points far from the source) will be red.

You can visually examine the liquid and gas simulation parameters in more detail from the youtube channel below.


Stay safe.





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