Cavity Flow Noise Control via Receptive Channels and Plasma Actuators

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Solution Overview

Problem

Fluidic flow over an open cavity generates impinging shear layers, leading to pressure oscillations and instability due to high pressure differentials, which can cause damage to objects within or near the cavity.

Innovation Solution

Forming channels between the cavity wall and an exterior surface to reduce pressure differentials, and using plasma actuators to actively manage fluid flow and attenuate pressure oscillations by adjusting the electrohydrodynamic body force based on measured pressure differentials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If channels are formed between cavity wall and exterior surface, then pressure differential is reduced, but device complexity increases

Engineering Contradiction:

Improvepressure differentialVSAvoiddevice complexity

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The cavity wall is segmented by forming channels between the cavity wall and exterior surface, dividing the pressure field into separate regions. This segmentation allows pressure differentials to be reduced by providing alternative flow paths while maintaining the structural integrity of the overall cavity system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The channels act as intermediary structures that mediate between the high-pressure cavity interior and the lower-pressure exterior environment. By introducing these intermediate flow paths, the pressure differential across the cavity wall is reduced without requiring complete structural redesign.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If plasma actuators are used to actively manage fluid flow, then pressure oscillations are attenuated, but device complexity and energy consumption increase

Engineering Contradiction:

Improvefluid flow stabilityVSAvoiddevice complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Pressure sensors detect pressure differentials across the cavity wall and provide feedback signals to the controller. The controller processes these signals and activates plasma actuators to generate electrohydrodynamic body forces that counteract the pressure oscillations, creating a closed-loop feedback control system that stabilizes fluid flow.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Traditional mechanical actuators (such as moving flaps or valves) are replaced with plasma actuators that use electrohydrodynamic effects to manipulate fluid flow. This substitution eliminates moving parts and mechanical wear while achieving the same flow control objectives through electromagnetic fields.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If plasma actuators are used to actively manage fluid flow, then pressure oscillations are attenuated, but energy consumption increases

Engineering Contradiction:

Improvefluid flow stabilityVSAvoidenergy consumption

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The plasma actuators are activated in a periodic or pulsed manner rather than continuously, based on the oscillatory nature of the pressure fluctuations. This periodic activation reduces energy consumption while maintaining effectiveness in attenuating pressure oscillations, as the actuators are only engaged when needed to counteract the oscillations.

Inventive Principle:

Principle #19Periodic action

4Stress or pressure

If channels are formed in the cavity wall, then pressure differential is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improvepressure differentialVSAvoidease of manufacture

Core Design Contradiction:

Stress or pressureVSEase of manufacture

Solution Approach 1:

The channels are designed to utilize fluid flow dynamics to reduce pressure differentials. By shaping the channels to follow streamline flow patterns and utilizing pressure gradient-driven flow, the manufacturing complexity is minimized while achieving the desired pressure reduction effect through fluid mechanical principles rather than complex mechanical structures.

Inventive Principle:

Principle #29Pneumatics and hydraulics

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 solution effectively reduces the amplitude of pressure oscillations and sound pressure levels, minimizing damage and instability caused by fluid flow over the cavity.

Implementation Method 1

adjusting the electrohydrodynamic body force based on measured pressure differentials

Methodology Applied

Scientific EffectElectrohydrodynamic body force: Electrohydrodynamics

Implementation Method 2

fluid flows through the channel so that the pressure differential is reduced

Methodology Applied

Scientific EffectPressure gradient driven flow: Pressure Gradient

Data Source

PatentUS9746010B2Noise control of cavity flows using active and/or passive receptive channels

Publication Date: 2017.08.29 UNIV OF FLORIDA RESEARCH FOUNDATION INC

AI summary

An apparatus comprises a surface that is configured to be exposed to a fluid stream and a cavity wall that forms at least a portion of a cavity. A first channel opening is formed in the surface, and a second channel opening is formed in the cavity wall. A channel extends from the first channel opening in the cavity wall to the second channel opening in the surface.