scholarly journals System Noise Assessment and the Potential for Low Noise Hybrid Wing Body Aircraft with Open Rotor Propulsion

2014 ◽  
Author(s):  
Russell H. Thomas ◽  
Casey L. Burley ◽  
Leonard V. Lopes ◽  
Christopher J. Bahr ◽  
Frank H. Gern ◽  
...  
Keyword(s):  
Low Noise ◽  
System Noise ◽  
Open Rotor ◽  
Noise Assessment

System Noise Assessment of Hybrid Wing–Body Aircraft with Open-Rotor Propulsion

2015 ◽  
Vol 52 (6) ◽  
pp. 1767-1779 ◽  
Author(s):  
Yueping Guo ◽  
Russell H. Thomas
Keyword(s):  
System Noise ◽  
Open Rotor ◽  
Noise Assessment

Development and Application of a Multi-Disciplinary Multi-Regime Design Methodology of a Low-Noise Contra-Rotating Open-Rotor

2015 ◽  
Author(s):  
Michaël Leborgne ◽  
Timothée Lonfils ◽  
Ingrid Lepot
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Design Methodology ◽  
Design Procedure ◽  
Low Noise ◽  
Design Parameters ◽  
Mechanical Constraints ◽  
Open Rotor ◽  
Mechanical Optimization ◽  
Lifting Line

This paper focuses on the development and exploitation of a multi-disciplinary, optimization-assisted, design methodology for contra-rotating open-rotors. The design procedure relies on a two-step approach. An aero-mechanical optimization is first performed to generate a geometry with good performances over several high-speed points representative of a mission. This geometry is subsequently used as the baseline of an aero-mechanical-acoustic optimization focusing on interaction noise reduction at Cutback and Sideline low-speed points. In terms of design parameters, both rotors are modified for the first phase but only the upper part of the front rotor is altered for the noise minimization. A fully-automatic high-fidelity aero-mechanical-acoustic computational chain with fluid-structure coupling is exploited in combination with evolutionary algorithms assisted by surrogate models for the constrained-optimization process. The acoustic footprint is estimated by a simplified but fast and relevant formulation combining an unsteady lifting-line and an acoustic propagation method. The best geometry of the first design gains 1.2pt in weighted efficiency while respecting all the aero-mechanical constraints. The acoustic optimization shows that noise reduction at Sideline and Cutback points is strongly antagonistic. However, significant Sideline noise reduction from 3.5 to 5.5dB depending on the harmonics is achieved while maintaining Cutback noise and without major degradation of high-speed efficiency.

Frequency limits for seismometers as determined from signal-to-noise ratios. Part 1. The electromagnetic seismometer

1992 ◽  
Vol 82 (2) ◽  
pp. 1071-1098 ◽  
Author(s):  
Peter W. Rodgers
Keyword(s):  
Operational Amplifier ◽  
Seismic Noise ◽  
Low Noise ◽  
Noise Model ◽  
Noise Voltage ◽  
Signal To Noise ◽  
Noise Current ◽  
System Noise ◽  
Large Gain ◽  
Total Noise

Abstract The range of frequencies that a seismometer can record is nominally set by the corner frequencies of its amplitude frequency response. In recording pre-event noise in very quiet seismic sites, the internally generated self-noise of the seismometer can put further limits on the range of frequencies that can be recorded. Some examples of such low seismic noise sites are Lajitas, Texas; Deep Springs, California; and Karkaralinsk, U.S.S.R. In such sites, the seismometer self-noise can be large enough to degrade the signal-to-noise ratio (SNR) of the recorded pre-event data. The widely used low seismic noise model (LNM) (due to Peterson, 1982; Peterson and Hutt, 1982; Peterson and Tilgner, 1985; Peterson and Hutt, 1989) is used as representative of the input ground motion acceleration power density spectrum (pds) at such very low noise sites. This study determines the range of frequencies for which the SNR of an electromagnetic seismometer exceeds 3 db (a factor of 2 in power and 1.414 in amplitude). In order to do this, an analytic expression is developed for the SNR of a generalized electromagnetic seismometer. The signal pds using Peterson's LNM as an input is developed for an electromagnetic seismometer. Suspension noise is modeled following Usher (1973). In order to determine the electronically caused component of the self-noise, noise properties are compared among three commonly used amplifiers. The advantages and disadvantages of the inverting and noninverting configurations in terms of their SNR are discussed. In most cases, the noninverting configuration is to be preferred as it avoids the use of the large gain setting resistances required in the inverting configuration to avoid loading the seismometer output. A noise model is developed for a typical low noise operational amplifier (Precision Monolithics OP-27). This noise model is used to numerically compute the SNRs for the three electromagnetic seismometers used as examples. The degradation in SNR caused by large gain setting resistances is shown. Numerical examples are given using the Mark Products L-4C and L-22D and the Teledyne Geotech GS-13 electromagnetic seismometers. For each of the example seismometers, the calculated range of frequencies for which their SNR exceeds 3 db is as follows: the GS-13, 0.078 to 56.1 Hz; the L-4C, 0.113 to 7.2 Hz; and the L-22D, 0.175 to 0.6 Hz. For the GS-13, the calculated lower and upper frequencies at which the SNR is 3 db are 0.078 and 56.1 Hz. This compares with the values 0.073 and 59 Hz measured in the noise tests on the vertical GS-13. Expressions for the total noise voltage referred to the input of an operational amplifier are developed in Appendix A. It is shown that in the inverting configuration, although no noise current flows in the input resistor, the noise current appears in the expression for the total noise voltage as if it did. In Appendix B, it is shown that any noise current flowing through an electromagnetic seismometer having a generator greater than several hundred V/m/sec generates a back emf that adds significantly to the noise of the system. This implies that system noise tests that substitute a resistor at the noninverting input of the preamplifier or clamp the seismometer mass will tend to underestimate the system noise.

Open-Rotor Noise Assessment with CFD/CAA Chaining

2015 ◽  
Author(s):  
Alain Chelius ◽  
Thomas Le Garrec ◽  
Daniel-Ciprian Mincu
Keyword(s):  
Rotor Noise ◽  
Open Rotor ◽  
Noise Assessment

scholarly journals Guidelines for the LTO Noise Assessment of Future Civil Supersonic Aircraft in Conceptual Design

Aerospace ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 27
Author(s):  
Grazia Piccirillo ◽  
Nicole Viola ◽  
Roberta Fusaro ◽  
Luigi Federico
Keyword(s):  
Conceptual Design ◽  
Aircraft Design ◽  
Low Noise ◽  
Aircraft Noise ◽  
Noise Model ◽  
Noise Power ◽  
Community Noise ◽  
Prediction Program ◽  
Supersonic Aircraft ◽  
Noise Assessment

One of the most critical regulatory issues related to supersonic flight arises from limitations imposed by community noise acceptability. The most efficient way to ensure that future supersonic aircraft will meet low-noise requirements is the verification of noise emissions from the early stages of the design process. Therefore, this paper suggests guidelines for the Landing and Take-Off (LTO) noise assessment of future civil supersonic aircraft in conceptual design. The supersonic aircraft noise model is based on the semi-empirical equations employed in the early versions of the Aircraft NOise Prediction Program (ANOPP) developed by NASA, whereas sound attenuation due to atmospheric absorption has been considered in accordance with SAE ARP 866 B. The simulation of the trajectory leads to the prediction of the aircraft noise level on ground in terms of several acoustic metrics (LAmax, SEL, PNLTM and EPNL). Therefore, a dedicated validation has been performed, selecting the only available supersonic aircraft of the Aircraft Noise and Performance database (ANP), that is, the Concorde, through the matching with Noise Power Distance (NPD) curves for LAmax and SEL, obtaining a maximum prediction error of ±2.19%. At least, an application to departure and approach procedures is reported to verify the first noise estimations with current noise requirements defined by ICAO at the three certification measurement points (sideline, flyover, approach) and to draw preliminary considerations for future low-noise supersonic aircraft design.

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