GfsRemoveDroplets

From Gerris

GfsRemoveDroplets replaces "droplets" (i.e. connected volumes containing the fluid with volume fraction unity) with the background fluid (characterized by a zero volume fraction).

The syntax in parameter files is as follows:

[ GfsEvent ] T MAX ( [ GfsFunction ] ) ( VAL )

where T is a variable defining the volume fraction and MAX is an integer which defines the maximum size of the droplets to be removed. If MAX is positive, all the droplets defined by less than MAX cells will be removed. If MAX is negative, all the droplets but the -MAX largest ones will be removed.

The last GfsFunction parameter is optional and can be used to define an alternative volume fraction field to use for the analysis. For example

RemoveDroplets { istep = 1 } T -1 (x > 0 && y > 0 ? T : 0)

will remove all the droplets but the largest one only in the top-right corner of the unit box.

The optional value VAL can be used to set which value to use to "erase" droplets (default is zero). This can be used for example in combination with the optional GfsFunction to remove "bubbles" rather than droplets

RemoveDroplets { istep = 1 } T -1 (1 - T) 1

Examples

• Collapse of a column of grains

    RemoveDroplets { istep = 1 } T -1

• Savart--Plateau--Rayleigh instability of a water column

    RemoveDroplets { istep = 10 } T -2