User-defined functions can be used to customize the discrete phase model to include additional body forces, modify interphase exchange terms (sources), calculate or integrate scalar values along the particle trajectory, and incorporate nonstandard erosion rate definitions. See the separate UDF Manual for information about user-defined functions.
In the Discrete Phase Model panel, under User-Defined Functions in the UDF tab, there are drop-down lists labeled Body Force, Scalar Update, Source, Spray Collide Function, and DPM Time Step (Figure 22.11.5). If Erosion/Accretion is enabled under the Physical Models tab, there will be an additional drop-down list labeled Erosion/Accretion. These lists will show available user-defined functions that can be selected to customize the discrete phase model.
In addition, you can specify a Number of Scalars which are allocated to each particle and can be used to store information when implementing your own particle models.