Domain - Fluid Dynamics

Here you will find parameters to configure the fluid's physical properties.

Viscosity

Here you can enter the desired value to create different substances. You can find detailed information about this feature here; the table under "HyFLIP - Viscosity Values" provides several viscosity values for various fluids.

Density

If you want to simulate highly viscous substances like chocolate or honey you can also enter the fluid's appropriate density value to get a complete material definition. Please bear in mind that it is currently not possible in Hybrido to simulate fluids with different “Density” values, for example oil and water. In most cases, this parameter can be left untouched.

Conserve volume

A common problem with FLIP solvers is a loss of volume, caused by large time steps, which are used to decrease simulation time. One side effect of these large time steps are precision errors in the solver's advection step. Another issue can be observed in combination with fast moving objects: in this case, such an object is not able to displace the fluid, because it simply goes through the fluid without interaction and literally “eats up” the fluid's volume.

With “Conserve Volume” set to “Yes”, the solver will try to conserve the volume. Please bear in mind that this method has its limit and when the loss of volume is considerable (approx. 50% or more) then it is very difficult to recover the original volume. On the other hand, you might notice an increase of volume in some situations. As a rule of thumb, we can say that “Conserve Volume” works best when the loss of volume is not higher than 10-20% per second. In cases where the loss is higher it is likely that you will see artefacts. This problem can be addressed with a more restricted time step (= higher “MIN substeps” value of the “Hybrido Main Solver”).

You can read more about the influence of time steps and the interaction between objects and fluids here.

Vorticity boost

To get a more turbulent fluid, it is possible to increase the particles' spin with this factor. Please try to avoid very high values (unless necessary), because they can completely distort the fluid. "Vorticity boost" is an implementation of the better-known "Vorticity Confinement" technique which can often be found in smoke simulation tools. This value accepts floats and is dimensionless. In many cases, values between 0.0 and 2.0 produce satisfying results. Please bear in mind that "Vorticity boost" is very sensitive.

Track lonely particles

Hybrido fluid particles can leave the main fluid body. These isolated particles can cause a huge deformation when they hit the grid fluid's surface. To avoid this unwanted behaviour, it is possible to tag the isolated particles as “lonely”. Then, the particles merge again with the remaining fluid, but do not cause any visible interaction. This is the default mode and uses the lifetime parameters below.

@ min lifetime/@ max lifetime

Both describe the isolated particles’ lifespan. When you use different values (“@ min lifetime” must be smaller than “@ max lifetime”), the actual lifespan lies somewhere between both values. This can help to achieve more random behavior. The lifetime parameters accept floats given in seconds [s].