Source Macro: Momentum Source Term

Description

This module uses ANSYS Fluent with a custom User-Defined Function (UDF) to simulate water flow through a porous medium channel, applying the DEFINE_SOURCE macro to implement a custom momentum source term. Rather than relying on Fluent's built-in porous media options, this project demonstrates how a UDF can directly modify the z-direction momentum equation to capture porous medium effects, offering greater flexibility and control over the modeled behavior.

Methodology

The 3D channel geometry is built in DesignModeler and meshed in ANSYS Meshing using a structured grid of 256,000 cells. The custom source term is formulated as a function of velocity and position, implemented via the DEFINE_SOURCE macro, with a source term derivative included for solver stability. The UDF is compiled and loaded into ANSYS Fluent, then integrated into the flow model to replace standard porous media treatment.

Conclusion

Results include 2D and 3D pressure contours, pressure gradient visualizations, and longitudinal pressure change plots, demonstrating the custom UDF's ability to capture porous media effects on the flow. This approach extends to applications such as groundwater flow and industrial filtration, and provides a foundation for more advanced UDF-based work involving multiphase flow through heterogeneous porous media, coupled heat transfer and reactions, or adaptive source terms for dynamic porous media behavior.