Design and Attenuation Properties of Periodic Checkerboard Liners

Nark

2011 IEEE SENSORS Proceedings

2011

Abstract-Emergent behavior, a subject of much research in biology, sociology, and economics, is a foundational element of Complex Systems Science and is apropos in the design of sensor network systems. To demonstrate engineering for emergent behavior, a novel approach in the design of a sensor/actuator network is presented maintaining optimal noise attenuation as an adaptation to changing acoustic conditions. Rather than use the conventional approach where sensors are managed by a central controller, this new paradigm uses a biomimetic model where sensor/actuators cooperate as a community of autonomous organisms, sharing with neighbors to control impedance based on local information. From the combination of all individual actions, an optimal attenuation emerges for the global system.

Section: A Communal System For Noise Reductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Communal sensor network for adaptive noise reduction in aircraft engine nacelles

Nark

2011 IEEE SENSORS Proceedings

2011

“…Although current implementations have uniform liners, research has shown that noise attenuation can be increased by liners in which the resonators are divided into segments of differing impedance: a segmented liner. Mani [6] and Watson [7] proved segmented liners can be designed to significantly outperform the best uniform liner for a given acoustic source.…”

Section: Background On Noise Reduction In Aircraft Engine Nacellesmentioning

confidence: 99%

Emergent adaptive noise reduction from communal cooperation of sensor grid

2010 13th International Conference on Information Fusion

Nark

et al. 2010

-In the last decade, the realization of small, inexpensive, and powerful devices with sensors, computers, and wireless communication has promised the development of massive sized sensor networks with dense deployments over large areas capable of high fidelity situational assessments. However, most management models have been based on centralized control and research has concentrated on methods for passing data from sensor devices to the central controller. Most implementations have been small but, as it is not scalable, this methodology is insufficient for massive deployments. Here, a specific application of a large sensor network for adaptive noise reduction demonstrates a new paradigm where communities of sensor/computer devices assess local conditions and make local decisions from which emerges a global behaviour. This approach obviates many of the problems of centralized control as it is not prone to single point of failure and is more scalable, efficient, robust, and fault tolerant.

11th AIAA/CEAS Aeroacoustics Conference

“…During the design optimization and assessment studies of Watson et al, [3][4][5] they observed that the checkerboard liner appeared significantly more sensitive to variations in the impedance values than did the uniform. This trend was also observed in the initial studies involving axially segmented, circumferentially segmented, and checkerboard liners.…”

Section: Introductionmentioning

confidence: 99%

“…It was concluded that the genetic algorithm was the most reliable of the optimization techniques due to its ability to handle multiple local optima generated by the checkerboard liner. In a subsequent study, Watson et al 4 combined the genetic algorithm with a numerical solution to the Helmholtz equation to demonstrate that an optimized 8-segment checkerboard liner gives considerably more attenuation than an optimum uniform or 4-segmented checkerboard liner. However, central processor unit (CPU) time and memory constraints and the occurrence of multiple local optima limited these results to a single frequency.…”

Section: Introductionmentioning

confidence: 99%

Performance of a Checkerboard Liner with Uncertain Impedances

Robinson

Watson

2005

Self Cite

The current fleet of large commercial aircraft has successfully achieved FAA noise certifications because of, in part, the successful application of uniform passive duct liner treatments to control engine system noise. One goal of NASA's engine system noise reduction program is to develop technologies to improve the sound absorbing properties of duct liner treatments so that they remain effective in modern turbo fan engines. One such technology being studied is checkerboard or periodic axially and circumferentially segmented liners. A preliminary assessment of the potential of this technology was conducted by applying uncertainties associated with manufacturing, installation, source structure, and tonal frequency to a liner developed using deterministic design methods and generating a measure of improvement with respect to a uniform liner subjected to the same uncertainties. Deterministic design and analysis of the candidate checkerboard liner showed that it obtains a 1.5 dB per duct aspect ratio improvement in liner attenuation over a similarly designed uniform liner. When uncertainties in liner impedances, source structure, and frequency are considered, the performance of the checkerboard liner drops off dramatically. The final results of this paper show that the candidate checkerboard liner has a less than 25 percent chance of outperforming the uniform liner when moderate levels of uncertainty are considered. It is important to note that this study did not include the effects of mean flow on liner performance and, more important to note, that as a gradient based optimization process was used to design the checkerboard liner, it is almost certain that a global optimal design was not found for the candidate checkerboard liner. Had it been possible to find a better deterministically performing checkerboard liner, the probability that this candidate liner would outperform the uniform liner would certainly have been higher. Subscripts: exit = exit plane u, c = uniform and checkerboard liner quantity I = the Ith impedance segment n, m = mode order in cross duct directions s = source plane