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365 results on '"Cai, Shuqun"'

13. Study on the internal waves induced by a submerged body moving in a continuously stratified fluid.

Author

Chen, Xuebin, Du, Hui, Xu, Jiexin, and Cai, Shuqun

Subjects
COMPUTATIONAL fluid dynamics, FROUDE number, WAVENUMBER, PLANE wavefronts, INTERNAL waves, COMPUTER simulation
Abstract

This paper studies the characteristics of internal waves induced by the motion of a submerged body through a combination of experimental and numerical methods. First, by deploying an array of conductivity probes in an experiment, the temporal evolution of the internal wave at the plane of the conductivity probe array is obtained and compared with numerical simulation results based on the Navier–Stokes equations, thereby validating the accuracy of the Computational Fluid Dynamics (CFD) model. Subsequently, utilizing CFD calculations, further exploration is conducted on the spatiotemporal distribution characteristics of the internal wave, encompassing its generation and evolution, velocity field distribution, wake angle, and wave profile features. Finally, the variation of the internal wave with the Froude number (Fr) is investigated, revealing that it varies apparently with Fr, including the wave component, wave mode, wake length, wake angle, wave amplitude, and so on. It is found that when Fr is large, the internal wave converges toward the centerline behind the body, until forming a line. The wave magnitude changes with Fr in four stages, i.e., increasing with Fr from zero in the first stage, reaching a peak and decreasing thereafter in the second stage, then changing little in the third stage, and finally increasing approximately linearly in the fourth stage. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Discrimination of Internal Solitary Waves from Coarse Time Resolution Field Observational Data by Using Wavelet Analysis.

Author

Xu, Jiexin, Chen, Shaomin, Gong, Yankun, Chen, Zhiwu, Cai, Shuqun, and Li, Daning

Subjects
INTERNAL waves, WAVELETS (Mathematics), OCEAN engineering, SIGNAL processing, SINGULAR value decomposition
Abstract

Internal solitary waves (ISWs) are large-amplitude internal waves which would destroy underwater engineering. Finding an easy way to discriminate ISWs from field observational data is crucial. Two time--series datasets, one contained ISWs and another only containing internal tides, were obtained from filed observations. Based on single-layer velocity data, wavelet spectrum shows significant high value in short time-scale domain when ISWs pass, whilst having no signal in that domain when only internal tides exist, indicating the capability of wavelet analysis on ISWs detection. Wavelet variances of the dataset with ISWs has a bimodal distribution versus periods with two peaks around 40 min and 110 min, which can also be reproduced by a numerical model, indicating that the energy within period band of 10–120 min is caused by ISWs. By using the conceived signal processing techne, data reconstruction can precisely obtain the arrival time of ISWs and retain about 91.4% of the original signal. It is found that, based on a field observational dataset with even a coarse sampling interval for up to 20 min, the existence of ISWs can be easily discriminated by using wavelet analysis, which provides us an economic method for the early warning of ISWs in ocean engineering. [ABSTRACT FROM AUTHOR]

Published
2024
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41. Common occurrences of subsurface heatwaves and cold spells in ocean eddies

Author

He, Qingyou, Zhan, Weikang, Feng, Ming, Gong, Yankun, Cai, Shuqun, and Zhan, Haigang

Abstract

Extreme ocean temperature events are becoming increasingly common due to global warming, causing catastrophic ecological and socioeconomic impacts1–5. Despite extensive research on surface marine heatwaves (MHWs) and marine cold spells (MCSs) based on satellite observations6,7, our knowledge of these extreme events and their drivers in the subsurface ocean—home to the majority of marine organisms—is very limited8,9. Here we present global observational evidence for the important role of mesoscale eddies in the occurrence and intensification of subsurface MHWs and MCSs. We found that 80% of measured MHWs and MCSs below a depth of 100 m do not concur with surface events. In contrast to the weak link between surface MHWs (MCSs) and ocean eddies, nearly one-third of subsurface MHWs (MCSs) in the global ocean, and more than half of such events in subtropical gyres and mid-latitude main current systems, occur within anticyclonic (cyclonic) eddies. These eddy-associated temperature extremes have intensified at rates greater than background level in past decades, suggesting a growing impact of ocean eddies on subsurface MHWs and MCSs with ongoing global warming.

Published
2024
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