fix liquidtransport command

Warning

GPU support for this command has not been tested and may not work as expected.

Syntax

fix ID group-ID liquidtransport keyword arg ...

• ID, group-ID are documented in fix command

• liquidtransport = style name of this fix command

Examples

fix liquidtransport all liquidtransport

Note

The natural-language version of this command is liquidtransport, which corresponds to fix liquidtransport all liquidtransport.

Description

This fix solves for the evolution of liquid for each particle in the fix group. Every time step, the liquid content of each particle is updated based on the sum of liquid fluxes with other particles and additional sources.

This fix internally creates four fix property/atom instances, that store the following variables:

surfaceLiquidContent	liquid content of a particle	volume % of solid (core+pore) volume
liquidFlux	liquid flux of a particle, as computed by a liquid bridge model	volume % of solid (core+pore) volume / time
liquidSource	liquid source via surface films, as computed by a liquid bridge model	volume % of solid (core+pore) volume / time

When this model is used in combination with spray droplets via custom_material_properties, then the transfer of liquid from droplet to particle can be modelled. The keyword ‘variable_properties’, a list of properties that are changed due to spray->particle mass transfer is defined. Available properties are mass and size (e.f. {mass,size}, the default is {}.

The per-particle variable surfaceLiquidContent is defined as the volume of liquid carried by the particle divided by the volume of the solid particle. There is no upper boundary for the liquid content; neither the particle radius nor its thermal capacity change with liquid content.

Liquid transport between particles, denoted by the variable liquidFlux, occurs if a liquid bridge model has been defined, e.g. cohesion easo/capillary_viscous and cohesion washino/capillary_viscous.

In order to use this fix, the initial liquid content of each particle must be defined as follows:

fix id all property/global surfaceLiquidContentInitial scalar value
    (value=value for the initial liquid volume in % of the solid volume)

Please note that when inserting particles with liquid content, the massflow rate of the insertion command only accounts for the mass of the dry material. For inserting the correct amount of material please scale the massflow rate down by the mass of the defined liquid film.

Output info:

This gran model stores a couple of per-particle properties, for access by various output commands.

You can access the property surfaceLiquidContent by f_surfaceLiquidContent (units % of solid particle volume), liquidFlux (units % of solid particle volume/time) by accessing f_liquidFlux and liquidSource (units % of solid particle volume/time) by accessing f_liquidSource. The latter can be used to manually set a surface liquid source via the set command.

Currently, there is a restriction that these properties can only be accessed after a run 0 command.

Restart, fix_modify, run start/stop:

All of the quantities used by this fix are written to binary restart files so simulations can continue properly. None of the fix_modify options are relevant to this fix.

No parameter of this fix can be used with the start/stop keywords of the run command.