Logarithmic Profile Acoustic Surface for Flow Resonance Reduction
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Solution Overview
Problem
Acoustic measurements in grazing flows are polluted by turbulent boundary layers and resonance phenomena in existing acoustic measuring devices, which are not fully satisfactory for accurate data collection across a wide range of frequencies.
Innovation Solution
An acoustic measuring device with an acoustic sensor positioned in a cavity on a surface, featuring a logarithmic profile acoustic surface that reduces measurement pollution by minimizing resonance effects and flow interference, utilizing an acoustically transparent wall and a recess to house the sensor, with a recess diameter adjusted to fit the sensor for minimal play and a peripheral zone forming a ring around the cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cavity with flat bottom and cylindrical lateral wall is used to reduce flow pollution, then measurement accuracy is improved, but resonance phenomenon appears in the cavity polluting acoustic measurements
Solution Approach 1:
The patent applies curvature by replacing the flat bottom and cylindrical walls with a spherical cavity geometry. The spherical shape eliminates resonance phenomena while maintaining flow pollution reduction, as the curved surfaces prevent standing wave formation that occurs in flat-walled cavities.
Solution Approach 2:
The patent changes the geometric parameters of the cavity from a standard cylindrical shape with flat bottom to a spherical shape with specific diameter-to-depth ratio. This parameter change transforms the acoustic characteristics of the cavity, eliminating resonance while preserving the ability to shield the sensor from flow turbulence.
2Device complexity
If the acoustic sensor is positioned flush with the surface, then device complexity is reduced, but turbulent boundary layer pollution affects measurements over wide frequency range
Solution Approach 1:
The patent extracts the acoustic sensor from direct contact with the grazing flow by positioning it inside a cavity that emerges from the surface. The cavity acts as a protective enclosure that shields the sensor from turbulent boundary layers while allowing acoustic signals to reach the sensor through the acoustically transparent wall.
Solution Approach 2:
The cavity with acoustically transparent wall serves as an intermediary structure between the grazing flow and the acoustic sensor. It mediates the interaction by blocking direct flow contact while transmitting acoustic signals, thus protecting the sensor from flow pollution without isolating it from acoustic measurements.
3Measurement precision
If the recess diameter is adjusted to fit the acoustic sensor for minimal play, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating a recess with dimensions specifically tailored to the acoustic sensor, with a small clearance (less than 1mm) between the sensor and recess walls. This localized precision fitting ensures optimal sensor positioning and acoustic coupling while concentrating manufacturing precision requirements only in the recess area rather than the entire device.
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 device provides accurate, resonance-free acoustic measurements by reducing flow pollution and achieving a flat angular response, minimizing measurement errors to within ±2 dB.
Implementation Method 1
a resonance phenomenon can appear in the cavity and pollute the acoustic measurements
Implementation Method 2
an acoustically transparent wall which closes the cavity flush with the surface
Implementation Method 3
the turbulent boundary layer of the flow which forms on the surface pollutes the acoustic measurements over a wide range of frequencies
Data Source
AI summary
An acoustic measuring device suitable for performing measurements on a surface in contact with a flow. This acoustic measuring device comprises an acoustic surface delimiting a cavity, which has an axis of revolution, which comprises a recess centered with respect to the axis of revolution, configured to house an acoustic sensor and which, in a longitudinal plane passing through the axis of revolution, follows a logarithmic profile which extends from a first edge separating the recess and the acoustic surface.