Cavitation Model Reference

When cavitation bubbles collapse, they release large amounts of energy into relatively small volumes. The collapsing bubbles create spots of high temperature and emit shock waves which are sources of noise. The collapsing bubbles can produce extensive erosion of the solid surfaces which are in contact with the cavitating regions.

Cavitation is a complex process that is influenced by many factors such as fluid static pressure, saturation temperature and pressure, surface tension, viscosity, density, thermal conductivity, fluid velocity, and distribution of cavitation seeds.

Cavitating flows are typically considered to be isothermal. However, if heat transfer becomes important, cavitation can be considered to behave in a manner similar to boiling. To model this scenario, specify the latent heat that is released or consumed to support the cavitation correctly.

Table 1. Cavitation Model Family Reference
Model Names	Full Rayleigh-Plesset
	Multi-component Full Rayleigh-Plesset
	Schnerr-Sauer
	Multi-component Schnerr-Sauer
Theory	See Cavitation and Gas Dissolution.
Provided By	[phase interaction] > Models > Cavitation Models
Example Node Path	Continua > Physics 1 > Models > Multiphase Interaction > Phase Interactions > [phase interaction] > Models > Full Rayleigh-Plesset
Requires	A VOF Multiphase simulation with the appropriate liquid phase and corresponding vapor phase defined. The liquid and vapor phases must be both single-component materials or both multi-component materials. A VOF-VOF Phase Interaction with the primary phase set to the liquid phase and the secondary phase set to the vapor phase. In the Phase Interaction Model Selection dialog: For single-component phases: Cavitation Models: Full Rayleigh-Plesset or Schnerr-Sauer For multi-component phases: Cavitation Models: Multi-component Full Rayleigh-Plesset or Multi-component Schnerr-Sauer
Properties	Connectivity Bubble Radius Velocity URF See Cavitation Model Family Properties.
Activates	Model Controls (child nodes)	Equilibrium Coefficient ScalingFac+ ScalingFac- See Cavitation Model Child Nodes.
	Materials	Phase Interaction Material Properties: Seed Density Seed Diameter Surface Tension Phase Material Properties: Saturation Pressure (applies to liquid phases only) See Cavitation Model Material Properties.
	Field Functions	Cavitation Rate of <phase interaction> See Field Functions.

Cavitation Model Family Properties

Connectivity

Maps the components in the liquid phase to their corresponding components in the gas phase. For multi-component phases, you select the gas component that corresponds to each liquid component. For cavitation models, you can ignore the dissolved gas components of the liquid mixture.

Applies to multi-component phases only.

Bubble Radius Velocity URF

The under-relaxation factor for the bubble radius velocity updates.

Applies to the Full Rayleigh-Plesset model and Multi-component Full Rayleigh-Plesset model only.

Cavitation Model Child Nodes

Equilibrium Coefficient: Specifies the method by which the equilibrium coefficient is found for each pair of liquid-gas components. By default, Raoult’s Law is used, as this option applies when the component is a significant fraction of the liquid mixture.
Applies to multi-component phases only.
ScalingFac+: Scales the positive bubble growth rate (see Eqn. (2692)). Specify the scaling value as a constant or a field function.
Applies to the Schnerr-Sauer model and the Multi-component Schnerr-Sauer model only.
ScalingFac-: Scales the negative bubble growth rate (see Eqn. (2692)). Specify the scaling value as a constant or a field function.
Applies to the Schnerr-Sauer model and the Multi-component Schnerr-Sauer model only.

Cavitation Model Material Properties

Phase Interaction Material Properties:

Seed Density: The seed density ( $n_{0}$ in Eqn. (2691)) is a liquid-dependent constant and is defined as the number of bubble seeds per unit volume of liquid.
Seed Diameter: The average seed diameter (2 $R_{0}$ ) is used to approximate the spectral seed distribution in a liquid (see Eqn. (2690)).
Surface Tension: Each phase interaction is assigned its own surface tension coefficient ( $σ$ in Eqn. (2695)). This coefficient is used to calculate the surface tension force between each of the defined phases in the phase interaction.
This property applies to the Full Rayleigh-Plesset model and Multi-component Full Rayleigh-Plesset model only. Surface tension effects are neglected in the Schnerr-Sauer model.

Phase Material Properties:

Set under [Phase] > Models > [Material (for example, Multi-Component Liquid) or Component (for example, Liquid Components > H2O)] > Material Properties when a cavitation model is activated.

Saturation Pressure

The pressure of each vapor component when in equilibrium with the corresponding liquid component. This value is required for each liquid component.

The saturation pressure $p_{s a t}$ is a key material property and is required by the Rayleigh-Plesset model (see Eqn. (2695) and Eqn. (2697)).

Field Functions

The following field function is available when the Temporary Storage Retained flag is set on the Segregated Volume Fraction solver.

Cavitation Rate of [phase interaction]: The volumetric rate of evaporation: the amount of vapor (in cubic meters) that is created per cubic meter per second.