Particle Properties
Use the Particle Properties node to specify the particle size, density, charge number, and particle velocity based on whether a Newtonian formulation or massless formulation is selected.
Particle Properties
This section is shown for the following choices in the physics interface Formulation list:
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Newtonian,
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Newtonian, first order, and
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Newtonian, ignore inertial terms.
Using Material Data
Usually it is necessary to specify the particle density. Depending on what additional forces or other physics features are added to the model, you might need to provide additional material properties, such as specific heat (if you selected the Compute particle temperature check box). You may either type values or expressions for these particle material properties directly, or take them from a Material node, which could either be a user-defined Blank Material or a material from one of the Material Libraries.
The default value in the Particle material properties list is None. If you wish to use data from a Blank Material or from the Material Libraries, first add the material to the model (right-click Materials either under the model component or under Global Definitions) and then select it from the list.
Choosing Which Particle Size Parameters to Specify
If Uniform size is selected from the Particle size distribution list in the physics interface Additional Variables section, select an option from the Particle property specification list:
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Specify particle density and diameter (the default),
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Specify particle mass and density, or
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Specify particle mass and diameter.
Then enter the applicable values or expressions for the following:
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Particle density ρp (SI unit: kg/m3). By default this is taken From material. If User defined is selected, the default value is 2200 kg/m3.
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Particle diameter dp (SI unit: m). The default is 1 μm.
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Particle mass mp (SI unit kg). The default is 1 mg.
If Specify particle diameter or Specify particle mass is selected from the Particle size distribution list, just enter a value or expression for the Particle density. Then the initial particle mass or diameter is controlled by the release features.
Select an option from the Particle type list: Solid particles (the default) or Liquid droplets/bubbles. If Liquid droplets/bubbles is selected, enter a value or expression for the Particle surface tension σp (SI unit: N/m). The default is 0.0729 N/m.
Liquid droplets/bubbles must be selected for at least one species in the model in order to use the Droplet Breakup and Nozzle features.
Charge Number
Enter a value or expression for the Charge number Z (dimensionless). The default is 0. The particle charge is the product of the charge number with the elementary charge e.
Particle Velocity
This section is shown when Massless is selected as the Formulation for the physics interface. Enter a vector for the Particle velocity v (SI unit: m/s) based on space dimension. The Massless formulation means that the particles follow streamlines of the particle velocity expression.
Thermal Properties
This section is shown when the following conditions are satisfied:
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the Compute particle temperature check box is selected in the physics interface Additional Variables section, and
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Either Specify particle mass or Specify particle diameter is selected from the Particle size distribution list in the physics interface Additional Variables section.
Enter a value or expression for the Particle latent heat hp (SI unit: J/kg). The default value is 42,000 J/kg.
Accretion Rate
This section is shown when Specify particle diameter or Specify particle mass is selected from the Particle size distribution list in the physics interface Additional Variables section. The accretion rate is the rate of increase or decrease in particle mass after the particles have been released; it can be used to model phenomena such as accretion, evaporation, condensation, and sublimation on the model particles.
Specifically, if the particles represent liquid droplets that can evaporate in a surrounding gas, add a Droplet Evaporation node to the model and then select it from the Accretion or evaporation rate specification list. Otherwise, keep the default value, User defined, and enter a value or expression for the Accretion rate R (SI unit: kg/s) directly. The default is 0. If the Accretion rate is positive, particles will grow continuously over time after they are released.