Undulating Cavity Spoiler for Acoustic Tone Suppression
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Solution Overview
Problem
Existing palliatives for reducing acoustic noise in cavities moving through fluid, such as aircraft bays, are inadequate in effectively suppressing acoustic tones and resonance, as they fail to disrupt the formation of large-scale vortices that generate noise.
Innovation Solution
A spoiler system with an undulating edge is positioned near the leading edge of the cavity, creating increased turbulence and a thicker shear layer by introducing multiple small vortices, disrupting the formation of large-scale vortices through varied vortex shedding times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional spoiler arrangements are used to divert airflow, then acoustic noise is reduced to some extent, but the suppression of acoustic tones and resonance is inadequate
Solution Approach 1:
The spoiler is segmented into multiple plates arranged in a zigzag pattern, creating multiple undulating edges that independently generate turbulence. This segmentation allows each plate to contribute to vortex disruption, providing more comprehensive coverage and better suppression effectiveness compared to a single conventional spoiler.
Solution Approach 2:
The spoiler plates are arranged at asymmetric angles relative to the flow direction, with each plate oriented to maximize its interaction with the shear layer. This asymmetric arrangement creates varied vortex shedding patterns that more effectively disrupt the temporal coherence of large-scale vortices.
2Object-affected harmful factors
If the shear layer is thickened to reduce large-scale vortex formation, then acoustic tones are suppressed, but the mechanism complexity increases
Solution Approach 1:
The spoiler plates feature undulating edges with curved surfaces instead of straight edges. This curvature creates continuous variations in flow separation points, generating enhanced turbulence and thickening the shear layer. The curved geometry naturally promotes small-scale vortex formation without requiring complex mechanical adjustments.
Solution Approach 2:
The spoiler arrangement extends the noise suppression mechanism into the transverse dimension by using multiple plates arranged in a zigzag pattern across the cavity opening. This multi-dimensional arrangement creates turbulence sources at different locations and orientations, effectively thickening the shear layer through spatial distribution rather than requiring a single complex structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The spoiler system significantly reduces acoustic noise by enhancing turbulence and disrupting the temporal coherence of vortices, thereby minimizing the generation of unwanted acoustic tones.
Implementation Method 1
creating increased turbulence and a thicker shear layer by introducing multiple small vortices
Implementation Method 2
A vortex is shed from the cavity leading edge and grows as it travels down the shear layer
Implementation Method 3
a shear layer is formed between the moving ambient air and the static air in the cavity
Implementation Method 4
increased disruption of the temporal coherence of the small vortices tends to be increased
Data Source
AI summary
A cavity system (300-600) is provided. The cavity system comprises a cavity (2) and a spoiler (304-604). The spoiler (304-604) comprises at least one plate (4) having a front surface and a rear surface, and an undulating edge. The spoiler (304-604) is positioned in the proximity of a leading edge (14) of the cavity (2), the leading edge (14) being relative to an actual or intended flow direction (3) of a fluid over the cavity (2), and the spoiler (304-604) is arranged with its longitudinal axis (1) perpendicular to or at an oblique angle to the actual or intended flow direction (3) such that the front surface faces towards the flow direction (3).