KHRT Droplet Breakup Model Reference

The KHRT Breakup model combines two submodels, one based on Kelvin-Helmholtz (KH) theory and one based on Rayleigh-Taylor (RT) theory.

Both breakup submodels consider the growth of instabilities on a droplet and provide expressions for their wavelength and frequency. Kelvin-Helmholtz instabilities are due to the slip velocity of the droplet, which eventually shears small child droplets off the parent [688], corresponding to the stripping regime. Rayleigh-Taylor instabilities are due to the acceleration of the droplet and tend to shatter the droplet completely [683], corresponding to the catastrophic regime. The KH and RT submodels compete: instabilities due to both can grow simultaneously; if they grow for long enough, breakup occurs due to the RT instabilities. Otherwise KH breakup occurs.


Theory	See KHRT Breakup Model.
Provided By	Lagrangian Multiphase > Lagrangian Phases > [phase] > Models > Secondary Breakup
Example Node Path	Lagrangian Multiphase > Lagrangian Phases > [phase] > Models > KHRT Breakup
Requires	Material: one of Gas, Liquid, Multiphase, Multi-Component Gas, Multi-Component Liquid (For Multiphase, Multi-Component Gas or Multi-Component Liquid, further models are required to expose the Flow models.) Flow: Coupled or Segregated Under the Lagrangian Multiphase model: Particle Type: Material Particles Material: Liquid or Multicomponent Liquid Particle Shape: Spherical Particles
Properties	Key properties are: Child Parcels. See KHRT Breakup Properties.
Activates	Materials	See KHRT Breakup Material Properties.
	Field Functions	Droplet Dynamic Viscosity, Droplet Surface Tension, Droplet Weber Number. See KHRT Breakup Field Functions.

KHRT Breakup Properties

Child Parcels: Number of child parcels to create during a breakup event.
Normal Velocity Coefficient: Normal velocity coefficient for child parcels, $A_{1}$ in Eqn. (3101)
B0: KH length coefficient, Eqn. (3099)
B1: KH time coefficient, Eqn. (3098)
C3: RT length coefficient, Eqn. (3104)
Ctau: RT time coefficient, Eqn. (3103)
Maximum fractional shed mass: Maximum fraction of the parcel mass that is shed before the child parcels are created.

KHRT Breakup Material Properties

Dynamic Viscosity

The dynamic viscosity

μ

of the droplet.


Method	Corresponding Method Node
Mass-Weighted Mixture	Mass-Weighted Mixture Available when the Multicomponent Liquid model is selected. The viscosity is determined by the composition of the droplet. See Eqn. (137).

Surface Tension

The droplet surface tension

σ


Method	Corresponding Method Node
Mixture	Mixture Available when the Multicomponent Liquid model is selected. The droplet surface tension is determined by the composition of the droplet according to Eqn. (143). Exponent The exponent $r$ in Eqn. (143). The default is 1.

KHRT Breakup Field Functions

Droplet Dynamic Viscosity: The dynamic viscosity of the droplet $μ_{l}$ .
Droplet Surface Tension: The surface tension of the droplet $σ$ .
Droplet Weber Number: The droplet Weber number $W e$ in Eqn. (3093).