### 1.4.9. Buoyancy Properties

#### 1.4.9.1. Thermal Expansivity

Thermal Expansivity (or coefficient of thermal expansion), , describes how a fluid expands with temperature. It is used in the Boussinesq approximation for buoyant flow and has dimensions of (where is temperature). For details, see Buoyancy in the CFX-Solver Theory Guide. This parameter will be used by the flow solver only if the fluid has a constant density. Otherwise, the full buoyancy model will be used, for which thermal expansivity is not a required parameter.

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