In the NTGK/DCIR and the ECM models, details of lithium ion transport are not resolved. Instead, the battery's electric behavior is modeled by an electric circuit, and SOC is used to track the battery's charging status. In the empirical swelling model, the swelling strain is assumed to be a linear function of the battery's SOC level:

(19–63)

where is the swelling coefficient that describes how fast the battery swells as its charging status changes, is the battery's current SOC level, and is the reference SOC level of the battery at the swell-neutral state.

You can customize the swelling strain formulation using a user-defined function (UDF) provided by Ansys Fluent. See DEFINE_BATTERY_SWELL_STRAIN in the Fluent Customization Manual for details.