Silencing the Roads and Skies with Fidelity LES

31 Mar 2025 • 6 minute read

Noise pollution has emerged as a significant challenge in our increasingly urbanized world. For automotive and aerospace engineers, the implications of this problem extend far beyond mere annoyance; it poses serious concerns for performance and compliance. Excessive noise levels can adversely affect aerodynamic performance, fuel efficiency, and adherence to regulatory standards.

Typically, passenger vehicles generate noise levels ranging from 70 to 80 decibels (dB) during operation. In contrast, heavy trucks can produce noise levels that surpass 80 dB, comparable to the experience of being near a rock concert. To tackle this pressing issue, high-fidelity noise prediction tools based on computational fluid dynamics (CFD) have become essential. These tools enable engineers to design quieter vehicles while maintaining optimal performance, ultimately aiding in the reduction of noise pollution in our urban environments.

This blog post examines how high-fidelity noise prediction significantly changes automotive and aerospace design through the use of the Cadence Fidelity LES Solver. We'll also present its impressive capabilities and showcase successful applications featured in the Cadence whitepaper on High-Fidelity Noise Prediction.

What Is High-Fidelity Noise Prediction?

High-fidelity noise prediction refers to highly accurate modeling of sound generated by turbulent aerodynamic forces in fluid flows. By using tools like Fidelity LES, engineers can:

Simulate complex aeroacoustic phenomena.
Identify sound sources such as vortex shedding or pressure fluctuations.
Optimize designs to reduce noise while maintaining performance.

The method combines computational accuracy with practical efficiency, replacing costly and time-consuming wind tunnel tests.

Why Is Noise Prediction Essential Across Industries?

Automotive

Vehicle noise is a consideration factor in consumer preference, legal compliance, and driving comfort. Whether it’s the hiss of airflow around the A-pillar or the pressure fluctuations on side mirrors, noise can dramatically alter the perception of a car’s quality. Engineers need tools to design quieter vehicles without sacrificing efficiency.

Aerospace

Urban Air Mobility (UAM) systems, like electric vertical take-off and landing (eVTOL) vehicles, demand quiet operation to avoid urban disruption. Traditional propeller-driven aircraft, jet engines, and even next-gen rotorcraft rely on precise aeroacoustic modeling to meet increasingly strict noise regulations.

With global cities becoming more congested, regulations governing acceptable noise levels grow tighter. Engineering quieter solutions gives companies the competitive edge they need, particularly in the automotive and aerospace industries.

Fidelity LES: A High-Fidelity Noise Prediction Tool

For engineers tackling the complex task of noise prediction, Fidelity LES stands as a best-in-class solution. Tailored for high-fidelity simulations, it enables the analysis and optimization of everything from automotive aerodynamics to supersonic jet acoustics.

Key Features of Fidelity LES

Predictive accuracy - Fidelity LES achieves unparalleled accuracy by resolving turbulent flow structures while modeling sub-grid details.
Efficient solver - Optimized for cutting-edge GPU architectures, it reduces time-to-solution compared to traditional CPU platforms.
High-quality mesh generation - Voronoi meshing ensures optimal computational efficiency and accuracy for aeroacoustic applications.
Scalability - Built for parallelization, it accommodates hardware ranging from local workstations to supercomputers.
Versatility - Handles low-speed flows typical of VTOL rotors and high-speed jet acoustics alike.

Innovations in Fidelity LES

What sets Fidelity LES apart is its Wall-Modeled LES (WMLES) approach. It balances computational resource demands by simulating turbulent flow structures far from walls while modeling smaller near-wall structures. Additionally, the tool integrates advanced skew-symmetric operators for higher-order accuracy, ensuring precision.

Real-World Case Studies of High-Fidelity Noise Prediction

1. Car Noise Simulation with Honda R&D

Honda leveraged Fidelity LES to study the aeroacoustic behavior of a sedan at 120 kph. Two surface resolutions were examined:

1 mm resolution (refined): Captured intricate turbulent structures around the A-pillar, revealing significant vortex shedding.
2 mm resolution (coarse): Provided a broader approximation.

Mesh visualization for the baseline setup with 2 mm surface resolution and 118M control volumes (Brès et al., 2023b)

Analysis showed the 1 mm surface resolution's higher precision, closely matching experimental wind-tunnel data. Fidelity LES also demonstrated impressive computational efficiency, running GPU-accelerated simulations 4X faster than traditional CPU setups.

Why It Matters:

Honda could validate aerodynamic enhancements that reduce cabin noise, improving comfort while meeting stringent noise regulations.

2. Aeroacoustic Analysis of VTOL Rotors

Researchers at Honda tested different rotor configurations (2 to 5 blades) using Fidelity LES. The software modeled low-speed turbulent flows crucial for rotorcraft by employing an advanced finite-volume LES code combined with 3D Voronoi meshes.

Visualization of the pressure field −400 ≤ P − P0 ≤ 400 Pa in a plane through the axis of rotation for the different rotors. The surface pressure (color contours) is also shown (Brès et al., 2023c)

Key Findings:

Noise increased with additional rotor blades.
Simulations showed strong alignment with wind-tunnel measurements of sound pressure level and broadband noise.
A conceptual model of a full-scale eVTOL was also simulated to assess computational throughput.

Why It Matters:

This study highlights opportunities for designing quieter rotorcraft, which is critical for the future of urban air mobility systems.

3. Fan Noise Diagnostic Test

NASA’s fan noise source diagnostic test (SDT) is a benchmark case in aeroacoustics. Using Fidelity LES, the fan was modeled at reduced rotational speeds with three-outlet guide vane (OGV) types.

Setup of the NASA SDT fan simulation: (a) zoomed-in view of the computational domain with the sponge region (outside of the orange box) and the FW-H surfaces – s1 (blue) and s2 (red); (b) the division of the domain where the green part is in rotation (Brès et al., 2023d)

Key Outcomes:

Low-noise OGV designs reduced sound power by 2 dB compared to traditional configurations.
Simulations achieved validation with less than 0.5% error in aerodynamic performance efficiencies.

Why It Matters:

These findings underline Fidelity LES’s ability to predict quieter, more efficient fan designs that will reshape electric and hybrid commercial aviation.

4. Supersonic Jet Noise Study

The acoustics of supersonic jets were investigated using Fidelity LES. This study leveraged LES to model the noise generated by highly heated, over-expanded supersonic jets with a military-style converging-diverging nozzle. Fidelity LES successfully modeled noise profiles with improved accuracy (reduced error to 1–2 dB).

Instantaneous temperature T/T∞ (top image) from 1 (black) to 5.5 (white) and velocity magnitude |u|/C∞ (bottom image) from 0.1 (blue) to 3.5 (red) for non-uniform inlet conditions (Brès et al., 2023a)

Why It Matters:

By simulating noise-reducing designs, Fidelity LES enables next-gen supersonic jets to meet noise compliance without compromising speed or performance.

Advantages of Fidelity LES Over Traditional CFD Solutions

Although experimental methods like wind tunnel tests remain an integral part of the design process, high-fidelity tools like Fidelity LES provide notable advantages:

Cost-effectiveness: Reduces dependency on expensive prototype testing.
Time efficiency: Faster time to decision compared to physical test with GPU-optimized workflows.
Improved insights: Allows direct access to flow physics and noise behavior, providing insights and enabling better design iterations.

The Future of Noise Prediction

As engineering solutions evolve alongside urban demands, high-fidelity noise prediction will remain a critical domain. Tools like Fidelity LES enable organizations to:

Develop sustainable transportation solutions.
Optimize noise performance across industries.
Maintain compliance with evolving regulations.

By leveraging predictive computational methods, CAD, CAE, and CFD engineers can tackle emerging challenges while staying ahead of the curve.

If you’re an engineer in the automotive or aerospace industry, it’s time to explore high-fidelity tools like Fidelity LES and see the difference they make in real-world applications.

References

Brès, G. A., Towne, A., & Lele, S.K (2019). Investigating the effects of temperature non-uniformity on supersonic jet noise with large-eddy simulation. 25th AIAA/CEAS Aeroacoustics Conference, DOI: 10.2514/6.2019-2730.
Brès, G. A., Ivey, C. B., Philips, D. A., Bose, S., Miyazawa, M., Morishita, K., & Teramura, M. (2023). Aeroacoustic simulations of full-scale sedan vehicle towards interior noise predictions. AIAA AVIATION 2023 Forum, DOI: 10.2514/6.2023-3825.
Brès, G. A., Ivey, C. B., Philips, D. A., Bose, S., Teramura, M., Moriya, T., & Ambo, K. (2023). Large-eddy simulations of multi-bladed VTOL rotors for air vehicle aeroacoustic predictions. AIAA AVIATION 2023 Forum, DOI: 10.2514/6.2023-3938.
Brès, G. A., Wang, K., Emory, M., Ivey, C. B., & Bose, S. (2023). GPU-accelerated large-eddy simulations of the NASA fan noise source diagnostic test benchmark. AIAA AVIATION 2023 Forum, DOI: 10.2514/6.2023-4299.

If you’re an engineer in the automotive or aerospace industry, it’s time to explore high-fidelity tools like Fidelity LES and see the difference they make in real-world applications. Read the white paper on High-Fidelity Noise Prediction to learn more about Fidelity LES for automotive and aerospace aeroacoustics applications.