This simulation investigates the acoustic behavior in a single automotive HVAC duct system featuring a complex outlet vent geometry. The case incorporates production-specific features such as small gaps and sealed interfaces that emerge where plastic components are joined together.

Isosurfaces of instantaneous velocity. Highest velocities occur around the flap and the vent lamellae. Isosurface values range from 8 m/s to 20 m/s

Simulation Highlights

  • Modeling of structural gaps and assembly joints typically found in production parts
  • Inclusion of these gaps and sealings reveals their function as passive acoustic dampers, extracting sound energy from the duct system
  • Strong agreement between simulated acoustic spectra and experimental measurements when gaps are included
Sound spectra at the microphones, measurement and simulation.

Impact & Engineering Insights

This showcase highlights the critical influence of manufacturing features on the acoustic behavior of HVAC systems. The ability to detect and visualize source regions, sink regions, and energy flow paths equips engineers with a detailed understanding of how sound propagates, transforms, and dissipates within complex duct systems.

Advanced Acoustic Analysis

  • Source & Sink Detection: Acoustic source and sink terms are computed across the flow field and visualized through spatial integration over grid boxes. Each box is represented as a colored sphere, intuitively highlighting areas of generation and absorption.
  • Acoustic Energy Flow Visualization: By integrating acoustic intensity over the surfaces of these grid boxes, we extract directional energy fluxes. These are visualized as cones indicating the direction and strength of acoustic radiation through the system.

Analyzed in the 600Hz band the the source regions coincide with high turbulent activity. The main fraction of produced acoustic energy is not radiated but transferred to the dead and of the duct, where it’s dissipating at the gap. Contrary at 1700Hz there is a compact source region close at the one side of the outlet duct and the acoustic energy is directly radiated outwards.

PSD of acoustic pressure PA, frequency band 600Hz
Integrated sound power production, frequency band 600Hz
Integrated sound power fluxes, frequency band 600Hz
PSD of acoustic pressure PA, frequency band 1700Hz
Integrated sound power production, frequency band 1700Hz
Integrated sound power fluxes, frequency band 1700Hz

For further information about this case refer to:

  • Johannes Kreuzinger, Florian Schwertfirm: Sound Source Identification Based on Balance of Acoustic Energy, Forum Acusticum Euronoise 2025, Malaga