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Nondestructive Testing
Published in Dale Ensminger, Leonard J. Bond, Ultrasonics, 2011
Dale Ensminger, Leonard J. Bond
Similar principles may be applied in industry, but here the received signal must be processed in such a manner that identification of an anomaly may be made on the basis of a visual rather than an aural data presentation, if necessary. Any moving system generates a sound. If the system is operating in a normal manner, the signal emitted may be called the “acoustic signature” of that system. The acoustic signature, therefore, identifies the normal condition. Any abnormality will affect the character of the emitted sound. For instance, a mechanic can readily distinguish between the pounding of a broken connecting rod in an internal combustion engine and the sound of a properly functioning engine.
Hydro-acoustic and noise analysis of DTMB4119 marine propeller at different advance coefficients using DES turbulence model
Published in Journal of Marine Engineering & Technology, 2023
Ehsan Yari, Mohammad Reza Nateghi
Propellers vary in various aspects, such as the number of blades, operating conditions, blade shape, section, etc. However, generally, their noise production process is qualitatively the same. The main components of noise in propellers are thickness noise (due to volume displacement of the blade), steady-loading noise (due to stable force on the blades), unsteady-loading noise (due to non-uniform circular loading), nonlinear or quadrupole noise, and the wide band noise. Although the importance of each of these sources depends on the performance and design conditions, their correct recognition plays a vital role in defining the acoustic signature of the propeller. Of course, the numerical modelling is somewhat different from the actual results because, in any case, applying real operating conditions, such as turbulent and non-uniform flow, is effective on the noise results (Carlton 2018).
A partitioned solution approach for the simulation of the dynamic behaviour of flexible marine propellers
Published in Ship Technology Research, 2020
L. Radtke, T. Lampe, M. Abdel-Maksoud, A. Düster
First results show that the applied BEM is capable of predicting the hydrodynamics around the propeller with an accuracy that is comparable to RANSE methods. The consideration of structural deformations yields physically consistent results. A validation of the partitioned solution approach is planned in the near future. The approach shall then be used in order to asses the acoustic characteristic of marine propellers. The noise in the far-field will be simulated based on the Ffowcs Williams-Hawking equation. For a realistic assessment of the propeller's acoustic signature, cavitation must be accounted for. Thanks to the partitioned solution approach, we can draw on established modelling approaches that have successfully been used in simulations of rigid propellers before.
Numerical investigation of hydrodynamic and hydro-acoustic performance of underwater propeller operating in off-design flow conditions
Published in Journal of Marine Engineering & Technology, 2020
Muhammad Rehan Naseer, Emad Uddin, Aamir Mubashar, Muhmmad Sajid, Zaib Ali, Khalid Akhtar
Based on the results of current study, the following conclusions have been drawn. An excellent agreement has been observed in comparison between numerically computed and η and experimental values, which testify our adopted numerical methodology.During azimuthing operating conditions, 15% enhancement in demand is noted, and the other observation is that the angle of incidence does not affect every set of loading condition (advance coefficient J) equally. In fact, the effect of the angle of incidence becomes more significant as advance coefficient approaches to the higher values.By changing the angle of incidence, it imparts significant effect onto the first harmonic frequency of acoustic pressure as the decrement in frequency is observed from 120 Hz (θ = 0°) to 34 Hz (θ = 20°).Effect of advance ratio in the case of oblique and straight flow conditions is noted in such a way that on average, intensity level increases by 24% as the advance ratio decreases from 0.9 to 0.7 for the oblique flow condition. While in the case of straight flow, it is 48% (almost double the value of former).Attenuation of intensity happened in the case of straight and oblique flows that can be illustrated as 75% reduction in peak amplitude value for oblique flow and 96% for straight flow, from receiver location X/R = 2 to X/R = 4.The in-depth analysis of the hydro-acoustic signature of the underwater propeller shows the effect of the acoustic noise for different sailing conditions as well as this effect is different in different directions by using the preliminary directivity analysis, which influences the marine aquatic environment. Future work on the directivity analysis can be carried out in detail to reveal the effect along different axis.