Friction Force
Use the Friction Force node to model collisions between particles and a background gas as a friction force that is proportional to the relative speed of the particles. Unlike the collision types that are available with the Collisions node, the Friction Force is deterministic and does not cause the particle velocity to change discontinuously over time.
friction force
Choose an option from the Specify force using list: Collision frequency equation or Mason–Schamp equation.
If Collision frequency equation is selected, choose either Cross section and number density or Collision frequency from the list.
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If Cross section and number density is selected, enter the following:
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Collision cross section σ (SI unit: m2). The default is 3 × 10−19 m2.
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Background number density Nd (SI unit: 1/m3). The default is 1020 1/m3.
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If Collision frequency is selected, enter the Collision frequency ν (SI unit: 1/s). The default value is 2 × 106 Hz.
If Mason–Schamp equation is selected, enter the value of Collision cross section σ (SI unit: m2, default 3 × 10−19 m2) and Background number density Nd (SI unit: 1/m3, default 1020 1/m3).
Fluid Properties
Enter coordinates for the Velocity field u (SI unit: m/s) based on space dimension.
To model the case of a stagnant background fluid, leave all the velocity components as zero.
If Mason–Schamp equation is selected, enter the following:
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Temperature T (SI unit: K). The default is 293.15 K.
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Background gas molar mass Mg (SI unit: kg/mol). The default id 0.04 kg/mol.
Affected Particles
Select an option from the Particles to affect list to apply the force to specific particles: All (the default), Single species, or Logical expression. The settings are described for the Force node.
Collisional Force Theory