Aeroacoustics

Simulating aeroacoustics is a tedious task that blends the complexities of fluid dynamics with the nuances of acoustic phenomena.

This dual-domain challenge is marked by numerous technical obstacles, ranging from the wide range of scales involved to the subtler distinctions of acoustic signals amidst turbulent flows. To navigate these technical difficulties and advance our understanding of aeroacoustic behaviors, engineers and researchers must employ sophisticated tools like the Cadence Fidelity LES.
This blog post explores the multifaceted challenges of aeroacoustic simulations and showcases case studies where Fidelity LES has proven helpful in solving these intricate problems.

Challenges Simulating Aeroacoustics

Simulating aeroacoustics presents significant challenges. Below is a list of some of these shortcomings:

• Wide Range of Scales: aeroacoustic phenomena cover extensive spatial and temporal scales. Capturing every scale demands fine grid resolutions and long simulation times.
• Acoustic Wave Amplitudes: aeroacoustic signals are often subtler than turbulent flow pressure fluctuations, making it tough to distinguish them from dominant flow structures.
• Far-Field Propagation: sound generated by local aerodynamic sources can propagate over large distances, making full-domain simulations computationally prohibitive.
• Complex Geometries: real-world problems often involve intricate geometries, such as aircraft engines or vehicle exteriors, which complicate fluid flow and sound propagation modeling.
• Boundary Conditions: Choosing and implementing appropriate boundary conditions is critical to avoid spurious reflections or non-physical behaviors.
• Transient Nature: Many problems are unsteady and require transient simulations, increasing computational effort and complicating statistical analysis.
• Nonlinear Interactions: High sound levels can involve nonlinear aerodynamic and acoustic interactions, requiring additional computational resources.
• Multiphysics Interactions: Some simulations need to account for other physical effects, like heat transfer or combustion, complicating the setup.
• Numerical Dissipation: Numerical methods can introduce artificial dissipation, dampening or suppressing acoustic signals of interest.

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Choosing the right simulation software is crucial for tackling real-world engineering challenges and fundamental research in aeroacoustics. Fidelity LES is a premier tool for high-fidelity flow analyses, including aeroacoustics. This software leverages large eddy simulation (LES) by integrating advanced numerical techniques and models to simulate unsteady flows with reduced dissipation and dispersion. Employing various solver formulations based on the finite volume method, Fidelity LES effectively captures different flow conditions, including low-speed, high-speed, and reacting flows.

Aeroacoustics of an eVTOL aircraft: pressure field and wall shear‑stress under cruise conditions.
Image © Honda Motor Co. (ref. AIAA 2023-3938).

Fidelity LES excels across varying grid resolutions thanks to advanced sub-grid and wall modeling. It accurately captures flow phenomena even on coarse grids, demonstrating impressive efficiency and scalability on both CPUs and GPUs. Notably, one V100 GPU matches the processing power of nearly 400 Intel Skylake 2018 CPUs for its implicit low-Mach solver. Engineers can seamlessly manage their entire simulation workflow with Fidelity LES, a user-friendly application that covers everything from preparing geometries to analyzing results.

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