This Application Best Practice (ABP) summarizes the development of two demonstration problems to illustrate the use of Ansys Fluent® fluid simulation software’s impedance Boundary Condition (BC) for simulating acoustic absorption at a wall with a prescribed impedance behavior. This is often referred to as a “soft wall” boundary, contrasting with a “hard wall” which is acoustically reflecting.

Learning Outcomes:

Following completion of this Application Best Practice (ABP), you will be able to:

• Differentiate between "soft wall" (acoustically absorbing) and "hard wall" (acoustically reflecting) boundaries.
• Apply impedance boundary conditions (BC) in Ansys Fluent software for simulating acoustic absorption.
• Setup and configure 2D and 3D models for acoustic simulations.
• Use Transparent Flow Forcing (TFF) to introduce acoustic signals at the inlet.
• Define specific geometry and flow conditions for 2D and 3D models.
• Generate meshes and set up solvers in Ansys Fluent software.
• Configure impedance BC using absorption coefficient data.
• Implement velocity inlet with zero velocity for soft wall modeling.
• Monitor and interpret pressure history and velocity magnitude.
• Compare acoustic signal attenuation between hard wall and soft wall models.
• Demonstrate acoustic damping using impedance BC in both 2D and 3D models.
• Assess the impact of steady throughflow on pressure wave propagation in 3D models.
• Simulate real-world scenarios involving acoustic absorption using Ansys Fluent software.

Prerequisites:

• Basic knowledge of Ansys Fluent software, especially unsteady flow modeling.

Please note: Application Best Practices (ABPs) outline engineering design goals for specific applications and provide guidance for how to achieve those goals using Ansys simulation software. It is important to note that a Geometry File or other Input Files are not always available. ABPs, as opposed to the official training-material workshops/tutorials, are not meant to be a step-by-step instruction document. ABPs are a link between product-based training courses and application specific tutorials, educating on the "how" and "why" of the best modeling approach, highlighting best practices and workflows for a particular application.

These training materials were developed and tested in the 2025R1 release.