The fiber model makes use of correlations to compute transfer of momentum, heat, and mass to the fibers. The fibers are subject to several physical effects that can be considered based on experimental correlations. Some of these effects may be lateral or longitudinal oscillations due to the applied take-up system, or to gas flow turbulence in the spinning chamber caused by the gas supply system of the spinning chamber. You can choose to specify a constant for the drag, heat transfer or mass transfer coefficients or use one of the Fluent-provided methods (for example, kase-matsuo) to compute the coefficients. These methods are described below. Alternatively, you can specify a custom drag, heat transfer, or mass transfer coefficient using a user-defined function (UDF). See User-Defined Functions (UDFs) for the Continuous Fiber Model for details on how to define and use UDFs in the fiber model.