Underwater Vibration Research Articles

Acoustic impact studies and assessments by Bureau of Ocean Energy Management on offshore wind development

The U.S. Bureau of Ocean Energy Management (BOEM) manages the exploration and development of offshore energy resources, including offshore wind development, on the U.S. Outer Continental Shelf. Construction, operation, and decommissioning of offshore wind facilities generate intense or long-lasting underwater sounds and vibrations that may be detrimental to marine life. This presentation will provide an overview of the activities that BOEM is in engaging in to address these impacts. BOEM’s Environmental Studies Program (ESP) has been developing funding and managing numerous studies to understand sound field characteristics and sound propagation from pile driving and geophysical surveys related to offshore wind development, as well as marine species responses to these activities. In addition, BOEM established the Center for Marine Acoustics (CMA) to strengthen its role as a driving force within the regulatory community on sound in the marine environment and provides acoustical expertise within the environmental permitting process. The CMA continues to provide guidance on the development of best practices for the use of acoustics in the evaluating the effects of offshore wind on marine fauna. This presentation will highlight the relevant acoustic studies and explain how BOEM is using the science to better manage noise impacts on the ocean environment.

Numerical and experimental investigation of vibro-acoustic characteristics of a submerged stiffened cylindrical shell excited by a mechanical force

In this paper, the direct testing method is adopted to measure the underwater vibration and sound radiation of a typical stiffened cylindrical shell structure under broadband excitation. The accuracy of the test result is verified by comparing with those obtained by numerical finite element (FE)/boundary element (BE) coupling method. In addition, the free vibration, forced vibration and sound radiation characteristics of stiffened submerged cylindrical shell are presented. The testing procedures and operation steps are established to provide support for the control of the vibration and sound radiation for underwater vehicle in this study. The results show that the trend of test result curve is in good agreement with FE/BE coupling method result, however, the acceleration and sound pressure is slightly different at the resonance peak value between experimental and numerical result in 500–2500 Hz band. In addition, the high frequency vibration and sound radiation response of the structure are mainly caused by a mechanical force.

BEM-FEM coupling for the hydroelastic analysis of propeller-shafting systems in non-uniform flows

The understanding of the fluid-propeller-shafting system's hydroelastic behavior is critical for underwater vehicle vibration and noise reduction. A three-dimensional panel method coupled with a three-dimensional finite element method for analyzing the hydroelastic dynamics of fully coupled propeller and shafting systems in the non-uniform flows is developed. The fully coupled fluid-propeller-shafting model is utilized to assess the applicability of the traditional uncoupled fluid-propeller (elastic vibration)/fluid-propeller (six degrees rigid body oscillation)-shafting models, which consider the elasticities of the blades and shaft separately. It is found that the designers need to consider the elastic coupling effect between the shaft and the propeller, especially in the case of high skew propellers. In addition, the uncoupled model underestimates the fluid-induced damping.

Bioinspired Adaptive, Elastic, and Conductive Graphene Structured Thin-Films Achieving High-Efficiency Underwater Detection and Vibration Perception

HighlightsThe lateral-line-like underwater mechanical sensor (LUMS) realizes the imitation of the structure and function of the lateral line.The detection range of water depth can be controlled by adjusting the size of the graphene/Ecoflex Janus film on LUMS. The maximum measured depth is 1.8 m.Similar to the fish, the mechanical stimuli from land and water can be sensitively captured by LUMS in real time.

Analysis of Viscoelastic Damping Effect on the Underwater Acoustic Radiation of a Ring-Stiffened Conical Shell

Hydroacoustic radiation from submarine power compartments has been the focus of research for many years. In this work, a ring-stiffened conical shell with bases is employed as the target model. The self-factors of viscoelastic damping, such as the damping thickness and damping location, are selected to study their effect on the underwater acoustic radiation, which will give a better understanding of the optimal scheme for applying damping. Firstly, based on a combination of finite element method (FEM) and boundary element method (BEM), the underwater vibration and acoustic radiation of the whole structure are analyzed. Secondly, taking a clamped-free sandwich beam as an example, through comparison with the published numerical data, the present damping application method and mesh density are verified. Finally, the influence of viscoelastic damping parameters on acoustic radiation is studied. The results show that the viscoelastic damping thickness has a significant influence on the amplitude of radiated noise but does not change the distribution of the acoustic field. Furthermore, the damping on the web may achieve the best vibration damping effect in this work.

Structural design optimization of vibration lures based on CAE

Lure fishing, a sports-like game using artificial lures as baits, has been popular around the world. In the present work, to enhance the underwater vibration behavior of vibration lures, we carry out structural design optimization of vibration lures based on computer aided engineering (CAE). At first, we create the finite element model of a vibration lure by a 3D scanner and perform weak coupled fluid-structure interaction (FSI) analysis of the vibration lure using finite element method. Then, according to the simulation results, we optimize the eye position (i.e., the knot position between fishing line and lure) and the positions of the weight placed in the lower part of the lure to obtain its largest fluid induced frequency.

High precision underwater 3D imaging of non-cooperative target with frequency comb

High-precision underwater imaging technology has an important role in underwater navigation and identification, underwater pipeline inspection, sinker docking, and underwater vibration measurement. Due to the different mechanisms of underwater measurement sources, such as 3D gated imaging and streak tube imaging, the accuracy of underwater target imaging can reach the millimeter level. In this paper, we propose a high-precision underwater imaging method based on frequency combs. When measuring the non-cooperative target underwater, the spectrogram is modulated due to the strong dispersion property of water. After that, for the gained spectrogram, we use two algorithms, i.e., center offset frequency and phase slope, to obtain the distance and imaging, respectively. By comparing with reference values, the underwater experimental results combining two algorithms show an agreement within 8 μm in the range of 2.5 m, corresponding to 3.2 × 10−6 relative precision. This work can provide a strong guarantee and support for high-precision underwater applications.

Review of the marine environmental impact assessment reports regarding offshore wind farm

The energy production of offshore wind farms plays an important role in expanding renewable energy. However, the development of offshore wind farms faces many challenges due to its incompatibility with marine environments and its social acceptability among the local community. In this study, we reviewed the marine environmental impact assessment status of offshore wind farm development projects for 2012–2019 in South Korea. A total of nine projects were selected for this study, all of which experienced considerable conflict with local fisheries resources. To appropriately respond to the underlying challenges faced by offshore wind farm development and in order to better support decision-making for future impact assessment, our findings identified: i) a need for adequate preliminary investigation and technical examination of fisheries resources; ii) a need to assess and estimate the impact of underwater noise, vibration, and electromagnetic waves on fisheries resources during wind farm construction and operation; and iii) a need for a bottom-up approach that allows for communication with local stakeholders and policy-makers to guarantee the local acceptability of the development.

Fiber Bragg Grating Sensors for Underwater Vibration Measurement: Potential Hydropower Applications.

The present paper assesses the performance and characteristics of fiber Bragg grating sensors, with a special interest in their applications in hydraulic machinery and systems. The hydropower industry is turning to this technology with high expectations of obtaining high quality data to validate and calibrate numerical models that could be used as digital twins of key assets, further strengthening the sector’s relevant position within industry 4.0. Prior to any validation, fiber Bragg grating sensors’ ability to perform well underwater for long periods of time with minimal degradation, and their ease of scalability, drew the authors´ attention. A simplified modal analysis of a partially submerged beam is proposed here as a first step to validate the potential of this type of technology for hydropower applications. Fiber Bragg grating sensors are used to obtain the beam’s natural frequencies and to damp vibrations under different conditions. The results are compared with more established waterproof electric strain gauges and a laser vibrometer with good agreement. The presence of several sensors in a single fiber ensures high spatial resolution, fundamental to precisely determine vibration patterns, which is a main concern in this industry. In this work, the beam’s vibration patterns have been successfully captured under different excitations and conditions.

Experimental and mixed analytical–numerical studies for free and forced vibrations of Z-reinforced sandwich plates stiffened by steel ribs

Free and forced vibrations of Z-reinforced sandwich plates stiffened by steel ribs are researched by experimental and mixed analytical–numerical techniques. A test sample of the plate is firstly manufactured and an underwater vibration test is conducted with a random white-noise force. Meanwhile, a mixed analytical–numerical method (MA-NM) is proposed, which uses an analytical homogenization for the Z-reinforced core and coupling finite element and boundary element (FE/BE) analyses for the plate. Natural frequencies given by the MA-NM are compared with ones from the detailed FE model. Forced vibration responses from the MA-NM are validated against the experimental data. Good agreements are obtained and the high accuracy of the MA-NM is demonstrated. Parameters influences are then analyzed through the MA-NM. The core material shows a larger effect on natural frequencies than the reinforcement material. Ribs at the orthotropic midlines greatly enhance the bend stiffness of the whole structure, and ribs at the surrounding sides mainly influence boundary conditions. When in-plane coordinates of the external force near the plate center, vibration responses have fewer resonance peaks and lower amplitudes, while the influence of the thickness direction coordinate could be ignored. The fluid loading reduces both natural frequencies and vibration responses.

Anthropogenic underwater vibrations are sensed and stressful for the shore crab Carcinus maenas

Acoustic pollution in aquatic environments has increased with adverse effects on many aquatic organisms. However, little work has been done considering the effects of the vibratory component of acoustic stimuli, which can be transmitted in the substrate and propagated into the aquatic medium. Benthic marine organisms, including many invertebrates, are capable of sensing seabed vibration, yet the responses they trigger on organism have received little attention. This study investigates the impact of underwater vibration on the physiology and behaviour of a ubiquitous inhabitant of coastal areas of the northern hemisphere, the shore crab Carcinus maenas. We developed a novel vibratory apparatus with geophones supported on a softly sprung frame to induce a seabed vibration of 20 Hz frequency, as observed during dredging, piling and other anthropogenic activities. The geophone internal mass caused the frame to vibrate in a controlled manner. Our results show that transition from ambient to anthropogenic vibrations induced an increase in activity and antennae beats in shore crabs, indicating perception of the vibratory stimulus and a higher stress level. There was also a trend on sex-specific responses to anthropogenic vibration, with males showing a higher activity level than females. However, no effect of anthropogenic vibrations was found upon oxygen consumption. These results show that anthropogenic underwater vibration induces behavioural responses in Carcinus maenas. This highlights the importance of evaluating man-made vibratory activities on coastal invertebrates and the necessity of evaluating anthropogenic effects on both sexes.

Bioinspired, Superhydrophobic, and Paper-Based Strain Sensors for Wearable and Underwater Applications.

There is currently a growing demand for flexible strain sensors with high performance and water repellency for various applications such as human motion monitoring, sweat or humidity detection, and certain underwater tests. Among these strain sensors, paper-based ones have attracted increasing attention because they coincide with the future development trend of environment-friendly electronic products. However, paper-based electronics are easy to fail when they encounter water and are thus unable to be applied to humid or underwater circumstances. Herein, based on a strategy of coupling bionics inspired by lotus leaf and scorpion, which exhibit superhydrophobic characteristics and ultrasensitive vibration-sensing capacity, respectively, a paper-based strain sensor with high sensitivity and water repellency is successfully fabricated. As a result, the strain sensor exhibits a gauge factor of 263.34, a high strain resolution (0.098%), a fast response time (78 ms), excellent stability over 12,000 cycles, and a water contact angle of 164°. Owing to the bioinspired structures and function mechanisms, the paper-based strain sensor is suitable to not only serve as regular wearable electronics to monitor human motions in real-time but also to detect subtle underwater vibrations, demonstrating its great potential for numerous applications like wearable electronics, water environmental protection, and underwater robots.

Rational design of fast recoverable shape-memory photoelectric spring in response to tiny deformation for monitoring underwater microvibration

Underwater vibration detectors have aroused intensive attention due to the promising applications in personal security, environmental protection and military defense. However, how to enable an underwater detector with combined feature of excellent structural flexibility and robustness as well as high detection sensitivity and stability, still remains a significant challenge. Herein, we successfully designed and developed a pitch-modulated spring with photoelectric response to its tiny deformation, via intercalating hydrogenated TiO2 (H–TiO2) nanoparticles between mutual contacting graphene sheets as the skeleton. Thanks to the intercalated spring architecture, the as-fabricated H–TiO2/graphene spring achieved good visible light absorption, fast shape recovery (<1 s), excellent shape-memory repeatability (>1000 cycles) at 30% stretching, as well as high structural and electrical stability even in saline solution over 10 days. Importantly, resulted from the variation of effective illumination area under stretching and compressing, the spring featured a significant fluctuation of photocurrent. Thus, the spring detector delivered high sensitivity and stability in monitoring underwater microvibration induced by bubble rising, and the underwater microvibration amplitude could be detected by the output photocurrent signal. This work has shed light on new strategies for designing and fabricating robust underwater microvibration detectors with high sensing performance toward future uses.

Investigation of underwater environmental effects in rotating propeller blade tracking laser vibrometric measurement

Analyzing the vibration characteristics of an underwater rotating propeller is crucial for predicting the structural damage of the propeller and preventing the failure of an entire propulsion system. The laser Doppler vibrometer (LDV) measurement technology is a good alternative to conventional contact sensors for the analysis of underwater structures. In this paper, a tracking LDV technique for the vibration measurement of propeller blades that rotate underwater is presented. The underwater vibration measurement of a rotating propeller is affected by the environmental conditions of the water, cavitation, and turbidity. The purpose of this study is to investigate the effects of underwater environmental conditions on the vibration measurement of a rotating propeller with the tracking LDV measurement technique. The vibration response measurements were performed in a water environment, and cavitation bubble and turbidity effects were simulated. To improve the quality of the measurement signal, the PCA-based feature extraction technique was used to remove abnormal signals including noise and irrelevant components and determine the natural frequency of the marine propeller. The final results show that the tracking LDV method with PCA-based feature extraction is suitable for in-situ health monitoring of rotating objects in real underwater environments.

Underwater vibration analysis method for rotating propeller blades using laser Doppler vibrometer

Vibration analysis for rotating propeller blades under water is obviously challenging. This study proposes stationary and tracking laser Doppler vibrometer (LDV) based measurement techniques for vibration analysis of the rotating propeller. The vibration measurement setup consists of an LDV, a DAQ and control system, and the rotating propeller that contains five blades mounted to the shaft through a rotor. To confirm the reliability of the proposed stationary and tacking LDV measurement results, the hammer impact tests are performed using a contact PZT accelerometer to obtain the velocity vibration results in time and frequency domain. These results are compared with LDV measurements for both in air and underwater cases. Both LDV and contact PZT measurements were taken simultaneously. The compared results show that the time-velocity signals and the corresponding frequency components obtained using hammer impact tests are very similar to the proposed LDV based measurement techniques. In addition, a numerical simulation is performed using COMSOL Multiphysics software to obtain natural frequencies of the system in air and underwater cases. These numerical simulation results are compared with bolt impact measurements taken on rotating propeller blade using LDV. Comparison of stationary and tracking LDV measurement results with the numerical analysis for in air and underwater cases showed matching results. From these results, it is concluded that the proposed techniques can be effectively used for underwater vibration measurement of the blades of rotating propeller.

Noise reduction with adaptive filtering scheme on interferometric fiber optic hydrophone

Fiber optic hydrophones have been widely used in underwater sounding, vibration detection and marine geological exploration due to their high sensitivity, wide frequency response range and strong anti-electromagnetic interference capability. In this paper, an adaptive filtering scheme based on Least Mean Square algorithm (LMS) is proposed to improve the detection sensitivity of hydrophones. Aiming to eliminate noise interference, a reference interferometer with the same parameters as the signal interferometer is added to the optical structure. Then, two 3 × 3 couplers are placed to demodulate the sensing signal and the noise signal respectively. Finally the adaptive filtering process is adopted to eliminate the noise effectively. The experimental results show that the proposed scheme can reduce the harmonic distortion signal and the noise signal. The suppression capability of the harmonic distortion signals at 1000 Hz is about 19 dB, and the signal-to-noise ratio is improved by about 23 dB.

A hybrid algorithm of underwater structure vibration and acoustic radiation-propagation in ocean acoustic channel

In ocean environment, the sound speed gradient of seawater has an important influence on far field sound propagation. The FEM/BEM is used to decouple the vibroacoustic radiation of the spherical shell, and the Green function of the virtual source chain is adopted for decoupling. For far field radiated Sound Pressure Level (SPL), the Beam Displacement Ray normal Mode (BDRM) is employed. The vibration and near-/far-field radiated SPL of spherical shell is analyzed in shallow sea uniform layer, negative/positive gradient, negative thermocline environment, and deep-sea sound channel. Results show that the vibroacoustic radiation of spherical shell acted at 300Hz can be analogous to dipole. When the radiated field of the spherical shell is dominated by large-grazing-angle waves, it can be analogous to vertically distributed dipole, and the far field radiated SPL is lower; while similar to horizontally distributed dipole if dominated by small-grazing-angle waves, and the far field SPL is high.

Acoustic characteristics near the living pool of captive belugas whale

Belugas are widely known for their diverse and frequent calls and have been given the nickname, “sea canaries.” As the number of belugas has been living in aquariums and ocean parks, it is very important for us to provide a comfortable environment for these creatures. That means we should understand how sounds made by belugas vocalization and environmental noise related to belugas habitats, therefore designing the most suitable artificial pool for these creatures. This study is on sound acquisition and acoustic estimation near the living pool of captive belugas whales in a new Ocean Park. Besides different hydrophones using for passive acoustic recording, accelerometer sensors and sound meters are deployed to obtain structural vibrations and airborne noises, respectively. Acoustic signals in different sites and pools were recorded, and their characteristics are analyzed and compared to mainly understand the relationship between underwater acoustics and structural vibrations. In the future, more detail tests will design to find out what is the main noise source which may be influencing belugas’ living. This study is also helpful to apply appropriate and reasonable methods for noise reduction. [Work supported by National Natural Science Foundation of China (Grant No. 41374147).]

Study on Vibration and Acoustic Radiation Characteristics of Composite Material Superstructures of Underwater Vehicles

Composite materials have been widely used in underwater ships for advantages of high specific strength, excellent acoustic performance and well designability. As an important indicator to measure combat effectiveness and vitality of underwater ships, structural radiation noise is the main target of acoustic detection weapons and the main factor that interferes with sonars. Underwater vibration and acoustic radiation characteristics of superstructure using composite sandwich panels directly affects the acoustic performance of underwater vehicles and the comfort and safety of personnel, therefore, research on vibration and acoustic radiation characteristics of underwater vehicle superstructure with composite material has important theoretical value and engineering prospect.

Functional Nanomaterials: 3D Porous Superhydrophobic CNT/EVA Composites for Recoverable Shape Reconfiguration and Underwater Vibration Detection (Adv. Funct. Mater. 24/2019)

Functional Nanomaterials: 3D Porous Superhydrophobic CNT/EVA Composites for Recoverable Shape Reconfiguration and Underwater Vibration Detection (Adv. Funct. Mater. 24/2019)