Hydrodynamic Noise Reduction

Loud hydrodynamic noise is not only potentially harmful to the health of organisms in the ocean, but it is also a threat to the survival of underwater vehicles. Different from the general noise reduction technologies at present, a new idea for a flow-induced noise reduction design with spanwise microgrooved surfaces inspired by sharkskin is introduced in this paper. Large eddy simulations (LES) combined with the Ffowcs Williams and Hawkings (FW-H) equation are adopted to simulate the hydrodynamic noise of the three-dimensional (3D) hydrofoil. The accuracy of the numerical predictions is checked against existing experimental data, achieving good agreement. With the increase of observing distance, the noise reduction effect at the trailing edge direction is gradually apparent, and a maximum noise reduction of up to 7.28 dB can be observed. It is seen from the noise spectra of the biomimetic hydrofoil that the main peaks are eliminated, and the noise level at high frequency is also decreased. The cause of noise reduction lies in the secondary vortex generated in the microgrooves, which hinder the process of turbulence, consume the energy of the flow, and weaken the intensity of turbulent burst. The results of this study provide a new way to design low-noise underwater structures with hydrofoils.

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The Hydrodynamic Noise Suppression of a Scaled Submarine Model by Leading-Edge Serrations

Journal of Marine Science and Engineering ◽

10.3390/jmse7030068 ◽

2019 ◽

Vol 7 (3) ◽

pp. 68 ◽

Cited By ~ 1

Author(s):

Yongwei Liu ◽

Yalin Li ◽

Dejiang Shang

Keyword(s):

Noise Reduction ◽

Experimental Test ◽

Noise Suppression ◽

Leading Edge ◽

Adverse Pressure Gradient ◽

Horseshoe Vortex ◽

Underwater Vehicles ◽

Counter Rotation ◽

Hydrodynamic Noise ◽

High Reynolds

High hydrodynamic noise is a threat to the survival of underwater vehicles. We investigated a noise suppression mechanism by putting leading-edge serrations on the sail hull of a scaled SUBOFF model, through numerical calculation and an experimental test. We found that the cone shape of leading-edge serrations can decrease the intensity of the adverse pressure gradient and produce counter-rotation vortices, which destroy the formation of the horseshoe vortex and delay the tail vortex. To achieve the optimum hydrodynamic noise reduction, we summarized the parameters of leading-edge serrations. Then, two steel models were built, according to the simulation. We measured the hydrodynamic noise based on the reverberation method in a gravity water tunnel. The numerically calculated results were validated by the experimental test. The results show that leading-edge serrations with amplitudes of 0.025c and wavelengths of 0.05h can obtain hydrodynamic noise reduction of at least 6 dB, from 10 Hz to 2 kHz, where c is the chord length and h is the height of the sail hull. The results in our study suggest a new way to design underwater vehicles with low hydrodynamic noise at a high Reynolds number.

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Suppression of the Hydrodynamic Noise Induced by the Horseshoe Vortex through Mechanical Vortex Generators

Applied Sciences ◽

10.3390/app9040737 ◽

2019 ◽

Vol 9 (4) ◽

pp. 737 ◽

Cited By ~ 1

Author(s):

Yongwei Liu ◽

Hongxu Jiang ◽

Yalin Li ◽

Dejiang Shang

Keyword(s):

Noise Reduction ◽

Noise Suppression ◽

Flow Direction ◽

Low Frequency ◽

Sound Field ◽

Leading Edge ◽

Horseshoe Vortex ◽

Vortex Generators ◽

Counter Rotation ◽

Hydrodynamic Noise

The hydrodynamic noise from the horseshoe vortex can greatly destroy the acoustic stealth of underwater vehicles at low frequency. We investigated the flow-induced noise suppression mechanism by mechanical vortex generators (VGs) on a SUBOFF model. Based on the numerical simulation, we calculated the flow field and the sound field of the three shapes of mechanical VGs: triangular, semi-circular, and trapezoidal. The triangular VGs with an angle of 30° to the flow direction achieved a better noise reduction. The optimum noise suppression is 8.93 dB, when the distance from the triangular VGs to the sail hull’s leading edge is 0.1c, where c is the chord length. The noise reduction mechanism is such that the mechanical VGs can destroy the formation of the horseshoe vortex at the origin and produce counter-rotation vortices to weaken its intensity. We created two steel models according to the simulation, and the experimental measurement was carried out in a gravity water tunnel. The measured results showed that the formation of the horseshoe vortex could be effectively inhibited by the triangular VGs. The results in our study can provide a new method for hydrodynamic noise suppression by flow control.

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Satisfaction With Noise Reduction Circuits

American Journal of Audiology ◽

10.1044/1059-0889.0201.51 ◽

1993 ◽

Vol 2 (1) ◽

pp. 51-53 ◽

Cited By ~ 2

Author(s):

Ruth A. Bentler

Keyword(s):

Noise Reduction

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Nonlinear temporal filter for television picture noise reduction

IEE Proceedings G (Electronic Circuits and Systems) ◽

10.1049/ip-g-1.1980.0009 ◽

1980 ◽

Vol 127 (2) ◽

pp. 52 ◽

Cited By ~ 4

Author(s):

T.J. Dennis

Keyword(s):

Noise Reduction ◽

Temporal Filter

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КОНЦЕПЦІЯ СТВОРЕННЯ СИЛОВОЇ УСТАНОВКИ СІМЕЙСТВА РЕГІОНАЛЬНИХ ПАСАЖИРСЬКИХ ЛІТАКІВ АН-148/АН-158

Open Information and Computer Integrated Technologies ◽

10.32620/oikit.2019.84.02 ◽

2019 ◽

pp. 50-63

Author(s):

О. Д. Донець ◽

В. П. Іщук

Keyword(s):

Power Plant ◽

Noise Reduction ◽

Fuel Consumption ◽

Electronic System ◽

Electronic Control ◽

Level Of Automation ◽

Auxiliary Power ◽

Power Plant Control ◽

Technical Status ◽

Air Intake

The basic results of calculation and research works carried out in the process of creation of power unit of regional passenger airplanes’ family are given. The design features of the propulsion engines and engine of the auxiliary power plant are described. The aforementioned propulsion system includes propulsion engines D-436-148 and engine AI-450-MS of auxiliary power plant. In order to comply with the requirements of Section 4 of the ICAO standard (noise reduction of the aircraft in site), in part of ensuring the noise reduction of engines, when creating the power plant of the An-148/An-158 aircraft family, a single- and double-layer acoustic filler was used in the structure of the engine nacelle and air intake. The use of electronic system for automatic control of propulsion engines such as FADEC and its integration into the digital airborne aircraft complex ensured the operation of engines, included in the power plant provided with high specific fuel consumption, as well as increased the level of automation of the power plant control and monitoring, and ensured aircraft automation landing in ICAO category 3A. In addition, the use of the aforementioned electronic system, allowed to operate the power plant of the aircraft in accordance with technical status. The use of the AI-450-MS auxiliary power plant with an electronic control system such as FADEC, and the drive of the service compressor from a free turbine, eliminated the effect of changes in power and air takeoff, on the deviation of the engine from optimal mode, which also minimized the fuel consumption. The use of fuel metering system TIS-158, allowed to ensure control of its condition and assemblies, without the use of auxiliary devices, built-in control means. In the fire protection system, the use of the electronic control and monitor unit, as well as the use of digital serial code for the exchange of information between the elements of the system and the aircraft systems, has reduced the number of connections, which increased the reliability of the system and reduced its weight characteristics.

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Design of Noise Reduction Output Filter for Induction Motor Using H-Bridge Inverter

The Journal of Next-generation Convergence Technology Association ◽

10.33097/jncta.2020.04.06.595 ◽

2020 ◽

Vol 4 (6) ◽

pp. 595-600

Author(s):

Hyun-Seob Cho ◽

Keyword(s):

Noise Reduction ◽

Induction Motor ◽

Output Filter

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AN IMPROVED ARMORED VEHICLE KRAZ “FIONA” NOISE SILENCER

Avtoshliakhovyk Ukrayiny ◽

10.33868/0365-8392-2019-1-257-21-26 ◽

2019 ◽

pp. 21-26

Author(s):

Volodymyr Fedorov ◽

Vasyl’ Yanovsky ◽

Dmytro Kovalshuk

Keyword(s):

Noise Reduction ◽

Speed Of Sound ◽

Acoustic Waves ◽

Noise Level ◽

Combustion Engine ◽

Environmental Aspect ◽

Exhaust Gases ◽

Ecological Requirements ◽

On The Road ◽

Armored Vehicle

Ecological requirements for cars grow from year to year, both in the world as a whole, and in Ukraine in particular. This is especially true of noise pollution. Additionally, noise reduction becomes relevant, taking into account the conduct of military operations during the last 5 years on the territory of Ukraine. The war has caused a special need for military vehicles for which masking properties are vital. Noise is a serious disincentive factor. Therefore, its reduction for a military vehicle, apart from the environmental aspect, is of a purely military nature, that is, it is extremely important. The car has many sources of noise there are many ways to deal with them. One of the most powerful source of noise is the sleeping bag. This kind of noise is reduced by means of silencers of noise. The vast majority of silencer data in the basis of its design has a reactive (or resonant) muffler. To calculate the jet silencer you must know the speed of sound in the sleeping bags. In order to increase the acoustic efficiency of reactive and resonant mufflers of exhaust gases noise of the ICE of cars, an experimental method was proposed for determining the speed of sound in the sleighs. Implementation of the method is carried out by measuring the attenuation of acoustic waves. The noise level of the bedrooms is measured without silencer and silencer. Based on the data obtained, the noise reduction performance of the residual is established. From the well-known formula, based on the calculation of the efficiency of the silencing of a jet muffler, a formula is obtained for calculating the speed of sound in the sleeping quays. In this formula, all parameters are known: the level of silencer efficiency, the noise level of the sleeping, the ratio of areas of cross sections of the muffler and the inlet pipe and the length of the muffler. The sound speed thus established can continue to be used not only for engines of the type for which measurements and calculations were made, but also with a certain approximation for some other types of engines. This method provides high accuracy for determining the required parameter. In the given work on the example of the armored car KrAZ “Fiona” the calculation of efficiency increase of the reactive silencer is made due to the above-mentioned method. Also, the projected decrease in the external noise level of the KrAZ Armored Vehicle “Fiona” is considered by determining the speed of sound in the recesses on the trunk cycle on the road with acceleration up to speed of 50 km/h (75 km/h) and the movement with this speed, as well as when driving at a speed of 45 km/h. Keywords: transport, armored car, internal combustion engine, exhaust, exhaust gases, noise, source, acoustic efficiency, acoustic efficiency, speed of sound, jet muffler.

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