Investigation on the thermohaline structure of the stratified wake generated by a propagating submarine

Chen, Qing; Lin, Qunqing; Xuan, Yimin; Han, Yuge

doi:10.1016/j.ijheatmasstransfer.2020.120808

Cited by 15 publications

(5 citation statements)

References 42 publications

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“…Numerical studies show clear temperature and salinity differences in the wake flow and discrepancies on the order of 0.1 • C and 0.02g/kg that persist well after the object has passed in a stratified fluid. 27 The presence of a large mixed layer does not inhibit signatures from objects travelling at large depths. Deep objects below the mixed layer upwell cooler water which travels freely to the surface and can be detected as a temperature change.…”

Section: Thermal Signaturesmentioning

confidence: 99%

The non-acoustic signatures of underwater vehicles

Slimming,

Beniwal,

Devrelis

et al. 2023

Ocean Sensing and Monitoring XV

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Submersible vehicles, such as Uncrewed Underwater Vehicles (UUVs), can be lost underwater and it is desirable to locate them before they go missing or collide with other vehicles. These objects generate inherent signatures when they move in the ocean. With a better understanding of these signatures, more information regarding the motion of underwater vehicles can be inferred using LiDAR technology. In this paper, the authors review existing literature on various non-acoustic signatures of a submerged body, namely, the electromagnetic, biological and thermal signatures, turbulent wake patterns, internal waves and vortex structures. The authors discuss how these signatures evolve both spatially and temporally. Furthermore, the review investigates how environmental and operational parameters such as the stratification of the medium, vehicle speed, shape and depth affect the non-acoustic signatures. Underwater vehicles operating at low speeds and large depths have bioluminescent, Kelvin wake and Bernoulli hump signatures that are difficult to detect on the surface. Thermal signatures, vortex wakes and far wakes are only likely to be detected at the vehicle’s depth. This is primarily due to the ocean stratification which suppresses the vertical motion of underwater turbulent signatures. Thermal signatures appear to be most likely to be detected. The study concludes that relying on a single signature to detect submersibles is not advisable and future methods for underwater vehicle detection should use multiple sensors to detect complementary signatures.

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Section: Thermal Signaturesmentioning

confidence: 99%

The non-acoustic signatures of underwater vehicles

Slimming,

Beniwal,

Devrelis

et al. 2023

Ocean Sensing and Monitoring XV

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“…Based on the characteristics of the submarine wake vortex, it can be detected. Literature [ 10 ] demonstrates that the in situ thermohaline distribution of submarine wake contains the key information of submarine detection. Using the method of large eddy simulation, a stratified temperature and salt wake model was established to realize submarine detection according to the change of wake temperature and salinity.…”

Section: Related Workmentioning

confidence: 99%

An Improved Wake Vortex‐Based Inversion Method for Submarine Maneuvering State

Kong

Yang

Cai

et al. 2023

Computational Intelligence and Neuroscience

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As the noise reduction performance of submarines continues to improve, it is difficult to detect and track submarines through acoustic detection techniques. Therefore, nonacoustic submarine detection techniques are becoming more and more important. The submarine movement will leave a wake vortex, and the information of the wake vortex can be used to invert the maneuvering state of the submarine. However, the wake vortex is constantly dissipated in the evolution process, and the strength of the wake vortex is constantly reduced, resulting in the gradual weakening of the characteristics of the wake vortex, which makes the inversion of submarine operating state difficult and less accurate. In order to solve the above problems, this paper proposes an improved wake vortex-based inversion method for submarine maneuvering state. Firstly, a random finite set of submarine wake vortex observation features is established to obtain the feature with the highest correlation degree with submarine maneuvering state in the random finite set. Secondly, the multiscale fusion module and attention mechanism are used to re-encode the weak features of the wake vortex image, and the salient features of the wake vortex image are extracted. Finally, the manipulation state of the wake vortex image is retrieved by the extracted salient features. The experimental results show that the average inversion accuracy of the proposed algorithm is improved by 1.27% in terms of manipulating state inversion of weak feature wake vortex images. The algorithm in this paper can realize the inversion of submarine maneuvering state in the case of weak submarine wake vortex image features and incomplete feature information. It provides the basis for the detection technology based on the submarine wake characteristics.

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“…In the field of seawater flow field monitoring, the study of the wave number spectrum of Batchelor turbulence with a refractive index gradient [25] shows that strong refractive index signal variations occur in the high-frequency band within a certain wave number interval, which puts demands on the sampling frequency of the sensor. Simulation studies of submarines [26] have shown that the time grid for simulation calculations needs to be of the order of 0.01 s or even a few milliseconds to obtain converged high-precision simulation results, where the amount of refractive index change in the fine structure is of the order of 10 −8 RIU. Thus, the sensitivity of the refractive index measurement based on the MNFBG meets the technical requirements of marine monitoring, while the sensitivity of the other measurement methods cannot meet the accuracy needed for the measurement of the ocean refractive index.…”

Section: Introductionmentioning

confidence: 99%

High-Sensitivity Seawater Refraction Index Optical Measurement Sensor Based on a Position-Sensitive Detector

Zhou,

Li,

Zhou

et al. 2024

Sensors

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The refractive index of seawater is one of the essential parameters in ocean observation, so it is necessary to achieve high-precision seawater refractive index measurements. In this paper, we propose a method for measuring the refractive index of seawater, based on a position-sensitive detector (PSD). A theoretical model was established to depict the correlation between laser spot displacement and refractive index change, utilizing a combination of a position-sensitive detector and laser beam deflection principles. Based on this optical measurement method, a seawater refractive index measurement system was established. To effectively enhance the sensitivity of refractive index detection, a focusing lens was incorporated into the optical path of the measuring system, and simulations were conducted to investigate the impact of focal length on refractive index sensitivity. The calibration experiment of the measuring system was performed based on the relationship between the refractive index of seawater and underwater pressure (depth). By measuring laser spot displacement at different depths, changes in displacement, with respect to both refractive index and depth, were determined. The experimental results demonstrate that the system exhibits a sensitivity of 9.93×10−9 RIU (refractive index unit), and the refractive index deviation due to stability is calculated as ±7.54×10−9 RIU. Therefore, the feasibility of this highly sensitive measurement of seawater refractive index is verified. Since the sensitivity of the refractive index measurement of this measurement system is higher than the refractive index change caused by the wake of underwater vehicles, it can also be used in various applications for underwater vehicle wake measurement, as well as seawater refractive index measurement, such as the motion state monitoring of underwater navigation targets such as AUVs and ROVs.

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Investigation on the thermohaline structure of the stratified wake generated by a propagating submarine

Cited by 15 publications

References 42 publications

The non-acoustic signatures of underwater vehicles

The non-acoustic signatures of underwater vehicles

An Improved Wake Vortex‐Based Inversion Method for Submarine Maneuvering State

High-Sensitivity Seawater Refraction Index Optical Measurement Sensor Based on a Position-Sensitive Detector

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