Hydroacoustic Field Research Articles

Modeling and simulation analysis of hydroacoustic field under ice

In order to study the effect of polar ice on sound propagation in seawater, the finite element method was used to establish a seawater sound propagation model with and without ice, and the influence of the presence of ice on the seawater sound propagation law was analyzed. The simulation results show that the energy of sound propagation in seawater has a certain loss when there is an ice layer compared with the case of no ice layer. Through frequency domain analysis, the propagation process of sound energy in seawater can be clearly seen. Normally, the sound energy generated by a point source at a suitable location will return to the seawater after passing through the sea surface, while after the addition of the ice layer, part of the sound energy generated by the point source will be lost to the air through the ice layer, resulting in a reduction of the acoustic energy returned to the seawater. As a result, there is less acoustic energy in the seawater than in the ice-free case.

Применение теоремы Гаусса–Маркова для эквализации гидроакустического канала передачи

Researchers in the field of modern hydroacoustics frequently encounter such problems as interference and noise in communication channels. Multipath propagation is an inevitable hydroacoustic communication problem arising in a sound channel due to reflections from the water surface and seabed. In general, this may decrease the overall communication quality. As a rule, noise cannot be completely eliminated, although its influence can be minimized. In this article, we describe a method for equalizing the hydroacoustic transmission channel using the Gauss–Markov theorem. This method can be used for reducing the multipath propagation effect and obtaining an unbiased estimate with minimal variance.

In Memoriam Professor Andrzej Orłowski (1947–2020)

Professor Andrzej Orlowski, a long-time employee of National Marine Fisheries Research Institute, passed away on October 27, 2020. He was an outstanding scientist in the field of hydroacoustics. Inventor of the method of use of multiple echo measurements to assess the type of the seabed. To this day, this method is called the Orlowski Method. Professor Orlowski was a member of the Physics Section of the SCOR, the NMFRI Scientific Council, the Polish Acoustical Society, ICES Fishery Acoustic Science and Technology Group, ICES Fish Technology and Fish Behavior Working Group, ICES SG Acoustic Seabed Classification and ICES SG Fish Avoidance of Research Vessels.

Cooperation Between China and Russia in the Field of Environmental Protection in the Arctic: Current State and Prospects

In the Arctic, social, economic and environmental issues require the region’s countries to work together to preserve the planet and improve the well-being of people living in harsh conditions. The region is warming twice as fast as the global average, ice and snow are melting, ecosystems are transforming, and indigenous and local cultures are struggling to adapt to the new conditions. Thus, the engagement of key international actors such as Russia and China in Arctic sustainable development goals is more than a platform for international partnerships for caring about the planet and humanity. In view of the above situation, the author uses the method of comparative analysis and induction to discuss topical issues of Chinese-Russian cooperation in the field of environmental protection in the Arctic. Particular attention is paid to such areas of cooperation as the development of international environmental law and participation in working groups on various environmental aspects; satellite navigation in the Arctic region, joint research, expeditions and training, as well as exchange of research equipment and data. In addition, emphasis is placed on Russian-Chinese programs in the field of underwater observation and hydroacoustics.

Research on propeller cavitation wake characteristics based on multivariate statistical modeling method

The radiation noise generated by cavitation has been extensively studied for underwater target recognition, but there are few reports on the related mechanism of the cavitation noise of ship propellers that attract attention in the field of hydroacoustics. In this paper, the RANS equations of the underwater propeller wake field are constructed, and numerically solved by combining the cavitation model and the turbulence model. The power spectrum is used to analyze the signal of the numerical calculation results of the propeller wake pressure. The feature estimation and extraction are carried out to obtain the characteristic values of the specific characteristic parameters. These eigenvalues not only reflect the flow field characteristics but also the geometric parameters and working conditions of the propeller. Therefore, two models are established around the relationship between them. Firstly, these eigenvalues are used for regression analysis in multivariate statistics to obtain a statistical model reflecting the characteristics of propeller cavitation wake. Secondly, the relationship between the propeller skew angle and the low frequency linear spectrum amplitude is obtained by using the power spectrum diagram. In this paper, the processing results of the experimental data of the cavitation water tunnel with controllable parameters and the radiation noise data of the actual target are used to verify and supplement each other with the processing results of the feature model.

Validation of Packaged Clad-Etched Fiber Bragg Grating as Underwater Acoustic Sensor

The low intrinsic pressure sensitivity of fiber Bragg grating (FBG) sensors impede their potential applications in the field of hydro-acoustics. This article demonstrates a simple, yet effective way of improving the aggregate hydro-acoustic sensitivity of a bare FBG sensor through clad-etching of the fiber sensor followed by a side-hole polymer packaging. The proposed underwater acoustic sensor system is characterized and validated with a standard lead zirconate titanate (PZT)-based hydrophone under various experimental conditions. This is the first time, to the best of our knowledge, such a high acoustic pressure sensitivity enhancement of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 50$ </tex-math></inline-formula> dB, in comparison with a bare FBG sensor, is reported using a conventional and highly operationally stable wavelength interrogation technique. The minimum detectable acoustic pressure is calculated to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 1$ </tex-math></inline-formula> Pa/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(\text {Hz})^{1/2}$ </tex-math></inline-formula> with a maximum responsivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 100$ </tex-math></inline-formula> nm/MPa in the investigated frequency range, with excellent performances in terms of linear response and repeatability. The dynamic range, in the present scenario, is only limited by the range of the interrogation system. The proposed underwater acoustic sensor along with the interrogation technique is a highly compact and cost-effective method for underwater acoustic sensing. Thus, the obtained results can be used for developing and producing long, narrow hydro-acoustic quasi-distributed sensor arrays for marine explorations and other applications.

Structure of the knowledge base for modeling hydroacoustic fields based on ray theory

The proposed research suggests improving the design and documentation of the implementation of modeling through the use of ontology. The ontology model allows you to structure information and also increases search efficiency. The study describes the development of an ontological model of engineering knowledge for modeling the hydroacoustic fields of the marine water area. The use of the ontology model for the development of the engineering knowledge portal allows you to systematize data and knowledge, organize search and navigation, and describe information and computing resources in accordance with metaconcept standards. The description of the subject area of the modeling system is based on the ontology, which allows you to assess the completeness of the proposed model and provide extended detailed documentation of the system.

Design of a hydro sound intensity probe for quantification and localization of acoustic sources — Applied to a hubless marine rim drive

The reduction of hydro noise emission by ship propulsion systems is of importance since background noise levels in the oceans have increased by 21 dB in the past decades. Thus, the acoustical improvement of ship propulsion systems is a necessary and challenging task. It involves not only the ship propeller but also the components of the entire drive train like diesel or electrical engines, electrical inverters as well as gearboxes. Acoustical measurement systems for the quantification and localization of noise sources are essential for any kind of optimization and are state of the art in the airborne noise field. This is not the case in the hydro acoustic field and measurements are mostly limited to the recording of the hydro sound pressure using single hydrophones. The objective of this paper is the presentation of a new three dimensional hydro sound intensity probe capable of acoustical sound power quantification and noise source localization. The probe can be used for the determination of the hydro sound pressure, the 3D sound intensity vector and the sound power. Furthermore, the probe can be utilized for hydro sound source localization purposes using beamforming methods based on virtual acoustical arrays. The developed probe was used for hydro acoustic investigations of a full scale marine rim drive during a measurement campaign in the river Warnow in Rostock, Germany. The results indicate the different hydro sound generating mechanism of the rim drive.

О ПРИМЕНИМОСТИ МЕТОДА БЫСТРОГО ЦИФРОВОГО ФОРМИРОВАНИЯ ХАРАКТЕРИСТИК НАПРАВЛЕННОСТИ В СИСТЕМАХ ЛОКАЦИИ СО СЛОЖНЫМИ СИГНАЛАМИ

This work belongs to the field of hydroacoustics, namely to the problem of digitalbeamforming based on spatial fast Fourier transform (FFT) in a multibeam echo sounder(MLS) with baseband digital signal processing. The applicability of FFT-based beamformingwhen using relatively broadband signals is considered. The main attention is paid to the MLSwith a static beam pattern, at the same time, obtained results are also applicable to rangingsystems that provide dynamic beam control. The aim of the study is to establish the relatio nshipbetween the relative width of the signal spectrum and signal level in the spatial channelof the MLS with a given maximum beam steering. A qualitative condition for the applicabilityof FFT-based spatial beamforming for a probing signal with a given relative bandwidth isdetermined. An analytical expression linking the signal attenuation coefficient in the spatialchannel with the following signal and receiver characteristics was obtained: the number ofelements of the linear equidistant antenna array, the distance between array elements, beamsteering, the correlation function of the complex envelope of the signal, the window functionfor weighting the matched filter response in spectral domain. Presented results can be usefulin designing multibeam echo sounders, providing high resolution both in range and in angularcoordinates.

Underwater target passive acoustic localization method based on Hanbury Brown–Twiss interference

PurposeAcoustic signals of the underwater targets are susceptible to noise, reverberation, submarine topography and biology, therefore it is difficult to precisely locate underwater targets. This paper proposes a new underwater Hanbury Brown-Twiss (HBT) interference passive localization method. This study aims to achieve precise location of the underwater acoustic targets.Design/methodology/approachThe principle of HBT interference with ultrasensitive detection characteristics in optical measurements was introduced in the field of hydroacoustics. The coherence of the underwater target signal was analyzed using the HBT interference measurement principle, and the corresponding relationship between the signal coherence and target position was obtained. Consequently, an HBT interference localization model was established, and its validity was verified through simulations and experiments.FindingsThe effects of different array structures on the localization performance were obtained by simulation analysis, and the simulations confirmed that the HBT method exhibited a higher positioning accuracy than conventional beamforming. In addition, the experimental analysis demonstrated the excellent positioning performance of the HBT method, which verified the feasibility of the proposed method.Originality/valueThis study provides a new method for the passive localization of underwater targets, which may be widely used in the field of oceanic explorations.

A Generalized Approach to Interference Invariant of the Hydroacoustic Field in Deep and Shallow Seas

A Generalized Approach to Interference Invariant of the Hydroacoustic Field in Deep and Shallow Seas

Computational hydroacoustic analysis of the BB2 submarine using the advective Ffowcs Williams and Hawkings equation with Wall-Modeled LES

In the present work we perform the numerical characterization of the hydrodynamic and the hydroacoustic field of a notional submarine geometry (the BB2 submarine). Starting from a model-scale CFD simulation, the full scale acoustic signature of the submarine is derived. We use large eddy simulation with a wall-layer model and perform laboratory-scale numerical experiments at a value of Reynolds number equal to 1.2×106. The conditions are those of a wind-tunnel test. The study is carried out focusing on the submarine in its own basic configuration without propeller to highlight the acoustic properties of the hull by itself and to replicate the silent advancing running (where all the non-essential source of noise are shut down and the speed is minimum to minimize the propeller noise). In this configuration, the wake is the main source of noise. The computational hydroacoustic analysis is based on the Ffowcs-Williams and Hawkings equation, here considered in advective form, which is the most suitable form for wind-tunnel-like problems. The results show that the acoustic spectrum is broadband in the far field and the SPL evaluated in the near field contains the signature of coherent structures associated to the presence of the sail and appendages.

A workflow for hydroacoustic source analyses based on a scale-resolving flow simulation of a hubless propeller

The steady increasing noise level in the oceans caused by shipping traffic and the resulting disturbance of marine mammals enhances the need for environmentally sustainable quiet ship propulsion systems. Acoustic optimizations as well as alternative propulsion concepts are able to reduce the noise emissions of ships. In terms of alternative propeller concepts, hubless propellers are a particularly interesting object of research due to their modified blade geometry and compact design.This work builds on a workflow that allows to calculate and analyze the hydroacoustic pressure field of a marine propeller. The transient pressure and velocity fields from a stress blended eddy simulation (SBES) of the hubless propeller was used for the calculation of the resulting hydroacoustic field using the expansion about incompressible Flow (EIF) approach. The calculation of the acoustic field is performed in a second step after the calculation of the flow field, which avoids the problem of the large disparity of time and length scales between the hydrodynamic and the acoustic field quantities.In addition, coherent flow structures were filtered using the proper orthogonal decomposition (POD) method for specific analysis of the hubless propeller hydrodynamic and hydroacoustic. The acoustic source term ∂p/∂t was furthermore calculated from the POD modes and time coefficients and used for the hydroacoustic analysis in order to identify dominant source regions of individual tonalities. Thus, this research aims to provide a workflow for hydroacoustic calculation and analysis as well as an approach for optimizations of marine propellers.

Flow-induced noise sources and reduction methods in centrifugal pumps: A literature review

This Review describes the research work conducted by many researchers in the field of hydro-acoustics of centrifugal pumps. This study aims to understand the flow induced noise mechanism, factors affecting it, and available methods to attenuate the same in centrifugal pumps. In general, the noise generated by a pump is interpreted in terms of pressure pulsations and can be represented in the frequency domain as a combination of discrete components and broadband components. In the discrete frequency noise component, the major emphasis is given on blade pass frequency noise and its relation to the rotor–stator interaction in pumps. The intensified rotor–stator interaction results in high pressure pulsations, thus strong flow induced noise. The effect of various geometrical parameters on the rotor–stator interaction and available methods to mitigate it to reduce noise are discussed in detail. Apart from the rotor–stator interaction, the importance of energy loss mechanisms, such as flow recirculation, flow-separation, and jet-wakes occurrence in pumps, which affect the blade pass frequency component, are also discussed. One of the other discrete noise components, the rotating stall mechanism with its physical mechanism, was also explored in detail. Subsequently, two major phenomena of broadband noise components, turbulence and cavitation, are explained. For cavitation, the phenomenon is elaborated in detail as well as various methods explored by the researchers to predict the existence of the cavitation phenomenon using the acoustic spectrum. Conclusions are also drawn for each source by describing the major events. In the end, the possible future scope of work that can be explored is given.

Vision systems as a type of information and telecommunications in matters of environmental monitoring water environment

To obtain high-quality video images characterizing the ecological condition of the underwater marine environment in real time, it is necessary to create modern automated systems for accumulating and processing video information, which are aggregated from autonomous underwater devices equipped with special technical means of control, in particular, television cameras. Technologies for environmental monitoring using these systems make it possible to study the seabed for the presence of unfavorable environmental factors and foreign objects, to identify them, as well as to map the seabed topography in order to provide the coordination center with a full volume of data on the bottom ecological situation. All this requires high-resolution video transmission from autonomous underwater devices. The traditional hydroacoustic underwater systems for accumulating and processing video information are being replaced by open systems for its optical transmission and reception, based on laser technologies. An obstacle for the wider use of hydroacoustic fields is the low speed of video information transmission to surface objects. The article substantiates the expediency of using open optical communication systems to create high-speed underwater information telecommunications, among which the most preferable are laser systems that have sufficient broadband, which is necessary to ensure a high video stream speed.

Amplitude and Phase Structure of a Low-Frequency Hydroacoustic Field in the Deep Ocean

Amplitude and Phase Structure of a Low-Frequency Hydroacoustic Field in the Deep Ocean

A New Approach to Analysis of the Properties of Disordered Structures in Hydrodynamic Acoustics as Supplement to Technology and Detection Theory

The article presents the results of the analysis of the properties of disordered structures in hydrodynamic acoustics, associated with the process of detecting physical phenomena and marine objects based on the results of their mechanical impact on the marine environment, in which acoustic vibrations propagate. If vortices, attractors, fractals arise as a result of complex interactions of forces of nature (upwellings, seiches, Coriolis forces, currents, convection flows, rotation of the Earth) and are essentially mechanical effects on the environment of formation and propagation of an acoustic field, then mechanical sources of sound introduced into the hydrosphere (water) should repeat fractal iterations on a smaller scale at the sound field level. Recognizing the equations of hydrodynamics (the equation of motion, the equation of continuity, and the equation of state) as the fundamental equations of hydroacoustics, the nonlinearity of these equations is proposed to be considered the theory of the hydroacoustic field as nonlinear, and the linearity of the processes in this study is considered a special case. The principle of superposition also becomes a special case, and the Fourier transform, remaining necessary, loses its sufficiency. Fractal analysis in combination with wavelet analysis should be involved to help him

Equiphase Lines of Sound Pressures in the Frequency-Spatial Domain of a Hydroacoustic Field

Equiphase Lines of Sound Pressures in the Frequency-Spatial Domain of a Hydroacoustic Field

Field-derived relationships between fish habitat distribution and flow-sediment conditions in fluctuating backwater zone of the Three Gorges Reservoir

The habitats of mountain river were excessively disturbed by various anthropogenic stressors with the development of social economy and increasing of population. To improve the geomorphological and ecological conditions of these habitats, restoration measures have been widely taken. Before any river restoration, there must be an understanding of the fish habitat requirement. The aim of this study was to gain an understanding of the relationships between hydraulic characteristics and fish assemblage in fluctuating backwater zone of the Three Gorges Reservoir and provide a scientific basis for protection and restoration of river habitats. To achieve this aim, three steps were taken. Firstly, a description of the characteristics of fish assemblage patterns in space and time was presented based on two hydroacoustic field surveys. Then the hydrodynamic model was used to numerically simulate the hydrodynamic conditions during the investigation period. Finally, evaluation of the hydrodynamic requirements of fish habitat was conducted on the basis of the relationship between the fish assemble and hydrodynamic conditions. The results showed that fish swarm preferred to gather and distribute in the deep pools with a depth of more than 20 m. Taking both hydrodynamic conditions and sediment transport into consideration, the minimum and maximum velocities of fish habitat requirement in the study area was 0.6 m/s and 1.2 m/s, respectively.

Laser adaptive vector-phase hydroacoustic measuring system

We have developed and experimentally implemented an adaptive laser vector-phase hydroacoustic measuring system, which allows one to determine the total acoustic intensity vector. A receiving element of the measuring system comprises six spatially separated fibre-optic coil-type sensors. Signals from the sensors are phase demodulated by using a six-channel adaptive holographic interferometer based on dynamic holograms multiplexed in a photorefractive CdTe crystal. Performance of the developed measuring system has been experimentally tested by determining the bearing and localisation of a source of a weak hydroacoustic field.