Grain Properties
Use the Grain Properties node to specify the grain material properties and grain size.
Granular Material Properties
You can either type values or expressions 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 Granular material list is None. If you want 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).
For the Density ρg (SI unit: kg/m3), by default this is taken From material. If User defined is selected, the default is 2200 kg/m3.
When a Hertz–MD or Hertz–MD with adhesion model is selected in the Contact force model list in the physics interface Force section, the Specify list appears with the options
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 Young’s modulus and Poisson’s Ratio (the default)
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 Young’s modulus and shear modulus
When Young’s modulus and Poisson’s ratio is selected, Young’s modulus and Poisson’s ratio fields appear; and when Young’s modulus and shear modulus is selected, Young’s modulus and Shear modulus fields appear. These properties can be assigned to grains as follows:
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 Young’s modulus Eg (SI unit: Pa). By default this is taken From material. If User defined is selected, the default is 100 GPa.
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 Shear modulus Gg (SI unit: Pa). By default this is taken From material. If User defined is selected, the default is 45.45 GPa.
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 Poisson’s ratio νg. By default this is taken From material. If User defined is selected, the default is 0.1.
The other material properties that can be assigned to grains are as follows:
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Specific heat capacity Cp,g (SI unit: J/(kg.K)). By default this is taken From material. If User defined is selected, the default is 2000 J/(kg.K). This field is only available when Compute grain temperature checkbox is selected in the Grain Temperature section in the physics interface.
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Thermal conductivity kg (SI unit: W/(m.K)). By default this is taken From material. If User defined is selected, the default is 0.2 W/(m.K). This field is only available when the Compute conductive heat transfer checkbox is selected in the Grain Temperature section in the physics interface.
Size
Enter value or expression for the Grain diameter dg (SI unit: m). The default value is 1 mm.
Enter value or expression for the Contact search expansion ratio β. β is defined as the ratio of the contact search diameter to the grain diameter. The default value is 1 which means the contact search diameter equals the grain diameter. This value must always be greater than or equal to 1 and can be used to extend the search radius used during contact detection. Typical use cases include enlarging the search radius to account for noncontact forces in force models such as Hertz–MD with adhesion or van der Waals.
Adhesion Properties
Enter value or expression for the Surface energy density γ (SI unit: J/m2). The default value is 0.05. This field is only available when the Compute van der Waals force checkbox is selected and/or when the Hertz–MD with adhesion is selected in the Contact force model list in the physics interface Force section.
The Grain Properties node is a default feature and cannot be deleted or disabled, and it is not possible to paste or duplicate this node in the model builder.
However, it is possible to add more than one instance of this Grain Properties node to the same model. When you do so, each instance corresponds to a different species of grain. Unlike the default Grain Properties node, these nondefault nodes can be deleted, disabled, duplicated, or pasted in the Model Builder.