Thermophoretic Force
The Thermophoretic Force node is only available when Newtonian or Newtonian, first order is selected as the Formulation on the Settings window for The Particle Tracing for Fluid Flow Interface.
Use the Thermophoretic Force node to exert the thermophoretic force on particles. The phenomenon called thermophoresis causes particles to migrate in a fluid with a nonuniform temperature field.
Thermophoretic Force
If the Include rarefaction effects check box is selected in the physics interface Particle Release and Propagation section, select a Thermophoretic force model: Epstein, Waldmann, Talbot (the default), or Linearized BGK. Use these settings to improve the accuracy of the thermophoretic force calculation in fluids with high Knudsen numbers. This is important when the fluid is a rarefied gas or the particles are extremely small. When the Include rarefaction effects check box is cleared, the fluid is treated as a continuum and only the Epstein model is used.
Enter a value or expression for the Temperature T (SI unit: K), or if the temperature is computed by another physics it can be selected from the list. The default is 293.15 K.
The following fluid parameters all take default values From material or can be computed from another physics interface. Or select User defined to enter a value or expression for the:
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Dynamic viscosity μ (SI unit: Pa·s). The default is 0.02 mPa·s.
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Density ρ (SI unit: kg/m3). The default is 1 kg/m3.
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Thermal Conductivity k (SI unit: W/(m·K)). For User defined select Isotropic, Diagonal, Symmetric, or Full and then enter values in the field or matrix.
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Heat capacity at constant pressure Cp (SI unit: J/(kg·K)).
The default is 1 kJ/(kg·K).
If the Waldmann, Talbot, or Linearized BGK model is used, also enter the Background gas molar mass Mg (SI unit: kg/mol). The default is 0.04 kg/mol.
If the Waldmann, Talbot, or Linearized BGK model is used, select an option from the Mean free path calculation list: Ideal gas, hard sphere collisions or User-defined correction. For User-defined correction enter a Mean free path correction λ'/λ by which the mean free path differs from the value for hard spheres in an ideal gas.
If the Linearized BGK model is used, enter an Energy accommodation coefficient αE (dimensionless) and a Momentum accommodation coefficient αM (dimensionless). The default values are 1.
Particle Properties
Enter a value or expression for the:
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Particle thermal conductivity kp (SI unit: W/(m·K)). The default is 1 W/(m·K).
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Thermophoretic correction factor Cs (dimensionless). The default is 1.17.
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If the Talbot model is used, enter two additional dimensionless thermophoretic correction factors Cm and Ct. The default values are 1.146 and 2.2, respectively.
Advanced Settings
Select the Use piecewise polynomial recovery on field check box to smooth the temperature using piecewise polynomial recovery. This can give a much more accurate representation of the temperature as it uses information on adjacent mesh elements to reconstruct the field. If a coarse mesh is used to compute the field then this option can be especially useful.
Use the Particles to affect list to apply the force to specific particles. The available settings are the same as for the Force node.
Thermophoretic Force in the theory section.