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Collision dynamics

1) Binary collision model

The available binary collision models are:

• NoBinaryCollision
• VariableHardSphere
• VariableSoftSphere

The selected model is defined for the entry BinaryCollisionModel. Here is an example for the VariableHardSphere model where the reference temperature \(T_{ref}\) is set to 273 K by default

// Binary Collision Model
// ~~~~~~~~~~~~~~~~~~~~~~

BinaryCollisionModel        VariableHardSphere;

2) Collision partner selection

The No-Time-Counter of Bird is the only recommended collision partner selection model (others haven’t been throughly tested). It is implemented as follows in constant/pdProperties

// Collision Partner Selection Model
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

collisionPartnerSelectionModel        noTimeCounter;

In this model, each cell have 8 subcells (2 in each direction) to reduce the mean collision separation.