Investigation of higher spanwise Helmholtz resonance modes in slender covered cavities

Investigation of higher spanwise Helmholtz resonance modes in slender covered cavities

De Jong, A.T.
Bijl, H.

Aerospace Engineering

Aerodynamics & Wind Energy

2010-10-01

Cavity aeroacoustic noise is relevant for aerospace and automotive industries and widely investigated since the 1950s. Most investigations so far consider cavities where opening length and width are of similar scale. The present investigation focuses on a less investigated setup, namely cavities that resemble the door gaps of automobiles. These cavities are both slender (width much greater than length or depth) and partially covered. Furthermore they are under influence of a low Mach number flow with a relatively thick boundary layer. Under certain conditions, these gaps can produce tonal noise. The present investigation attempts to reveal the aeroacoustic mechanism of this tonal noise for higher resonance modes. Experiments have been conducted on a simplified geometry, where unsteady internal pressures have been measured at different spanwise locations. With increasing velocity, several resonance modes occur. In order to obtain higher mode shapes, the cavity acoustic response is simulated and compared with experiment. Using the frequency-filtered simulation pressure field, the higher modes shapes are retrieved. The mode shapes can be interpreted as the slender cavity self-organizing into separate Helmholtz resonators that interact with each other. Based on this, an analytical model is derived that shows good agreement with the simulations and experimental results.

acoustic noise
acoustic resonance
aeroacoustics
aerospace industry
automobile industry

http://resolver.tudelft.nl/uuid:b12833bc-1f47-4ef8-a198-a87d35a81d6a

doi:10.1121/1.347369

Acoustical Society of America

0001-4966

Journal of the Acoustical Society of America, 128 (4), 2010

Institutional Repository

journal article

(c) 2010 De Jong, A.T.
Bijl, H.
Acoustical Society of America