How They Work

Our products are made with porous materials that interact with the wind to manage both velocity and turbulence.  Porous materials have benefits for airflow control by introducing a fluid permeable medium that modifies boundary layer, shear layer, and wake characteristics.  Incoming turbulence is absorbed by the material and there is a designed amount of air flow-through.  In addition, surface interaction with the soft fibers reduces velocity / rotational intensity.

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Our products reduce wind velocity and turbulence intensity.

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And move the modified / weaker flow away from the outer ear.

Academic Analogies

Academic research supports utilizing porous pile materials to reduce wind turbulence and aerodynamic noise.  As shown in the graphic below (5 m/s wind speed):  "It is remarkable that the near-wall flow is very calm for the case of pile-fabric.  We see that the separated shear layer is thicker and weaker for the pile-fabric compared with the smooth case.  In fact, the streamwise position where the shear fluctuations become maximum is located at about x/d=2.5 for the pile-fabric while it is about x/d=0.4 for the smooth surface." - a)

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Flow visualization at 20 mph to verify the above turbulence distribution.

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As demonstrated above, pile material significantly modifies downstream flow.

Loudness / Annoyance

In addition to masking surrounding sounds, wind noise can be annoying.  While loudness can be the primary driver for annoyance, noise level variation / fluctuations and other spectral characteristics can also play a role.  Accordingly, we incorporate additional tools, like spectrograms, when we evaluate performance from an end user perspective.  

Related Research / References

  • (a- Kudo, T., Nishimura, M., Nishioka, M., Aerodynamic Noise Reducing Techniques by Using Pile-Fabrics., 5th AIAA/CEAS Aeroaoustics Conference., AIAA-Paper. (1999)

  • (a- Nishioka, M., Vorticity Manipulation as an Effective Means for Aerodynamic Noise Reduction., The Eighth Asian Congress for Fluid Mechanics., Shenzhen, China. (1999)

  • Nishioka, M., Aerodynamic Noise Suppression Technique Using Fur., Japan Society of Aeroacoustics and Astronautics, Osaka Prefecture University, Faculty of Engineering Dept. (2000)

  • Nishimura, M., Goto, T., Kobayashi, K., Effect of Several Kinds of Pile-Fabrics on Reducing Aerodynamic Noise., Aeroacoustics Conference Presentation., Monterrey, California. (2005)

  • Massaharu, N., Nishimura, M., Goto, T., Aerodynamic Noise Reduction by Pile Fabrics., Fluid Dynamics Research., Department of Mechanical / Aerospace Engineering, Tottori U.,  Japan. (2010)

Aeroacoustic engineering helps us develop the most effective products.