Tidal bore is a special and intensive form of flow movement induced by tidal effect in estuary areas, which has complex characteristics of profile, propagation and flow velocity. Although it has been widely studied fo...Tidal bore is a special and intensive form of flow movement induced by tidal effect in estuary areas, which has complex characteristics of profile, propagation and flow velocity. Although it has been widely studied for the generation mechanism, propagation features and influencing factors, the curved channel will complicate the characteristics of tidal bore propagation, which need further investigation compared with straight channel. In this study, the flume experiments for both undular and breaking bores’ propagation in curved channel are performed to measure the freesurface elevation and flow velocity by ultrasonic sensors and ADV respectively. The propagation characteristics,including tidal bore height, cross-section surface gradient, tidal bore propagation celerity, and flow velocity are obtained for both sides of the curved channel. And three bore intensities are set for each type of tidal bores. The freesurface gradients are consistently enlarged in high-curvature section for undular and breaking bores, but have distinct behaviors in low-curvature section. The spatial distributions of tidal bore propagation celerity and flow velocity are compared between concave and convex banks. This work will provide experimental reference for engineering design of beach and seawall protection, erosion reduction and siltation promotion in estuary areas with the existence of tidal bores.展开更多
With the development of large liquid cargo ships,liquid tank sloshing has gradually become a hot research topic in the area of shipping and ocean Engineering.Liquid tank sloshing,characterized by strong nonlinearity a...With the development of large liquid cargo ships,liquid tank sloshing has gradually become a hot research topic in the area of shipping and ocean Engineering.Liquid tank sloshing,characterized by strong nonlinearity and randomness,not only affects the stability of the ship but also generates a huge impact force on the wall of the tank.To further investigate liquid tank sloshing,a comprehensive review is given on the research process of the most focused subjects of liquid sloshing.Summarizing the existing research will help to identify issues in the current field and provide useful references.The methods for investigating sloshing,the research progress and the situations worldwide are discussed.The advantages and defects of experiments and numerical simulations are also explored.The problems which need to be explored in the future are subsequently proposed.展开更多
Wave energy has drawn much attention as an achievable way to exploit the renewable energy. At present, in order to enhance the wave energy extraction, most efforts have been concentrated on optimizing the wave energy ...Wave energy has drawn much attention as an achievable way to exploit the renewable energy. At present, in order to enhance the wave energy extraction, most efforts have been concentrated on optimizing the wave energy convertor and the power take-off system mechanically and electrically. However, focusing the wave power in specific wave field could also be an alternative to improve the wave energy extraction. In this experimental study, the Bragg resonance effect is applied to focus the wave energy. Because the Bragg resonance effect of the rippled bottom largely amplifies the wave reflection, leading to a significant increase of wave focusing. Achieved with an energy conversion system consisting of a point absorber and a permanent magnet single phase linear motor, the wave energy extracted in the wave flume with and without Bragg resonance effect was measured and compared quantitatively in experiment. It shows that energy extraction by a point absorber from a standing wave field resulted from Bragg resonance effect can be remarkably increased compared with that from a propagating wave field （without Bragg resonance effect）.展开更多
For surface gravity waves propagating over a horizontal bottom that consists of a patch of sinusoidal ripples,strong wave reflection occurs under the Bragg resonance condition.The critical wave frequency,at which the ...For surface gravity waves propagating over a horizontal bottom that consists of a patch of sinusoidal ripples,strong wave reflection occurs under the Bragg resonance condition.The critical wave frequency,at which the peak reflection coefficient is obtained,has been observed in both physical experiments and direct numerical simulations to be downshifted from the well-known theoretical prediction.It has long been speculated that the downshift may be attributed to higher-order rippled bottom and free-surface boundary effects,but the intrinsic mechanism remains unclear.By a regular perturbation analysis,we derive the theoretical solution of frequency downshift due to third-order nonlinear effects of both bottom and free-surface boundaries.It is found that the bottom nonlinearity plays the dominant role in frequency downshift while the free-surface nonlinearity actually causes frequency upshift.The frequency downshift/upshift has a quadratic dependence in the bottom/free-surface steepness.Polychromatic bottom leads to a larger frequency downshift relative to the monochromatic bottom.In addition,direct numerical simulations based on the high-order spectral method are conducted to validate the present theory.The theoretical solution of frequency downshift compares well with the numerical simulations and available experimental data.展开更多
The characteristics of swells within the East China Sea have been reported by Tao et al.(2017),while the question of where the swells come from remains unanswered.By using the wave model WAVEWATCH III and the swell tr...The characteristics of swells within the East China Sea have been reported by Tao et al.(2017),while the question of where the swells come from remains unanswered.By using the wave model WAVEWATCH III and the swell tracking method proposed by Hanson(2001),the spatial sources of the swells are investigated during four typical typhoon scenarios,which usually affect the wave environment in the East China Sea,including the Recurving type,the Northward type,the Westward type(striking the East China Sea)and the Westward type(over the South China Sea).The numerical results show that parts of the swells are from the North West Pacific with a long-distance travelling.The moving paths of the swells are affected by the typhoon tracks,which result in various fetches.The Westward type(over the South China Sea)makes one peak in the evolution process.The landing process of the Westward type(striking the East China Sea)could result in swells with low energy.The swell energy depends on swell propagation distance,existence time and wind intensity of generation fetch.The consistent fetch and forceful wind intensity make swell carry more energy.展开更多
In the original publication of the article(Peng et al.2022),under the section‘Comparisons with experiments and direct numerical simulations’,Fig.4 was not included.The figure is given below:Reference Peng,J.,Tao.,A....In the original publication of the article(Peng et al.2022),under the section‘Comparisons with experiments and direct numerical simulations’,Fig.4 was not included.The figure is given below:Reference Peng,J.,Tao.,A.F.,Fan,J.,Zheng,J.H.and Liu,Y.M.,2022.On the downshift of wave frequency for Bragg resonance,China Ocean Engineering,36(1),76-85.展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2022YFE0104500)the National Natural Science Foundation of China (Grant No. 52271271)+2 种基金the National Natural Science Foundation of China (Grant No. 41906183)the National Natural Science Foundation of China (Grant No.52101308)the Fundamental Research Funds for the Central Universities (Grant No.B220202080)。
文摘Tidal bore is a special and intensive form of flow movement induced by tidal effect in estuary areas, which has complex characteristics of profile, propagation and flow velocity. Although it has been widely studied for the generation mechanism, propagation features and influencing factors, the curved channel will complicate the characteristics of tidal bore propagation, which need further investigation compared with straight channel. In this study, the flume experiments for both undular and breaking bores’ propagation in curved channel are performed to measure the freesurface elevation and flow velocity by ultrasonic sensors and ADV respectively. The propagation characteristics,including tidal bore height, cross-section surface gradient, tidal bore propagation celerity, and flow velocity are obtained for both sides of the curved channel. And three bore intensities are set for each type of tidal bores. The freesurface gradients are consistently enlarged in high-curvature section for undular and breaking bores, but have distinct behaviors in low-curvature section. The spatial distributions of tidal bore propagation celerity and flow velocity are compared between concave and convex banks. This work will provide experimental reference for engineering design of beach and seawall protection, erosion reduction and siltation promotion in estuary areas with the existence of tidal bores.
基金financially supported by the National Natural Science Foundation of China(Grant No.52271271)the National Key Research and Development Program of China(Grant No.2022YFE0104500)+1 种基金“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province(Grant No.2022C03023)Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ17E090003)。
文摘With the development of large liquid cargo ships,liquid tank sloshing has gradually become a hot research topic in the area of shipping and ocean Engineering.Liquid tank sloshing,characterized by strong nonlinearity and randomness,not only affects the stability of the ship but also generates a huge impact force on the wall of the tank.To further investigate liquid tank sloshing,a comprehensive review is given on the research process of the most focused subjects of liquid sloshing.Summarizing the existing research will help to identify issues in the current field and provide useful references.The methods for investigating sloshing,the research progress and the situations worldwide are discussed.The advantages and defects of experiments and numerical simulations are also explored.The problems which need to be explored in the future are subsequently proposed.
基金financially supported by the National Natural Science Fundation of China(Grant Nos.51579091,51379071,and 51137002)the Qing Lan Project of Jiangsu Province,the Basic Research Fund from the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University(Grant Nos.20145027512 and 20145028412)+1 种基金the Short-term Research Visits Project supported by Disaster Prevention Research Institute of Kyoto University(Grant No.27S-02)the FundZamental Research Funds for the Central Universities of Hohai University(Grant No.2016B05214)
文摘Wave energy has drawn much attention as an achievable way to exploit the renewable energy. At present, in order to enhance the wave energy extraction, most efforts have been concentrated on optimizing the wave energy convertor and the power take-off system mechanically and electrically. However, focusing the wave power in specific wave field could also be an alternative to improve the wave energy extraction. In this experimental study, the Bragg resonance effect is applied to focus the wave energy. Because the Bragg resonance effect of the rippled bottom largely amplifies the wave reflection, leading to a significant increase of wave focusing. Achieved with an energy conversion system consisting of a point absorber and a permanent magnet single phase linear motor, the wave energy extracted in the wave flume with and without Bragg resonance effect was measured and compared quantitatively in experiment. It shows that energy extraction by a point absorber from a standing wave field resulted from Bragg resonance effect can be remarkably increased compared with that from a propagating wave field （without Bragg resonance effect）.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. U1706230 and51379071)the Key Project of NSFC-Shandong Joint Research Funding POW3C (Grant No. U1906230)the National Science Fund for Distinguished Young Scholars (Grant No. 51425901)
文摘For surface gravity waves propagating over a horizontal bottom that consists of a patch of sinusoidal ripples,strong wave reflection occurs under the Bragg resonance condition.The critical wave frequency,at which the peak reflection coefficient is obtained,has been observed in both physical experiments and direct numerical simulations to be downshifted from the well-known theoretical prediction.It has long been speculated that the downshift may be attributed to higher-order rippled bottom and free-surface boundary effects,but the intrinsic mechanism remains unclear.By a regular perturbation analysis,we derive the theoretical solution of frequency downshift due to third-order nonlinear effects of both bottom and free-surface boundaries.It is found that the bottom nonlinearity plays the dominant role in frequency downshift while the free-surface nonlinearity actually causes frequency upshift.The frequency downshift/upshift has a quadratic dependence in the bottom/free-surface steepness.Polychromatic bottom leads to a larger frequency downshift relative to the monochromatic bottom.In addition,direct numerical simulations based on the high-order spectral method are conducted to validate the present theory.The theoretical solution of frequency downshift compares well with the numerical simulations and available experimental data.
基金the National Natural Science Fundation of China(Grant Nos.51579091 and U1706230)the National Science Fund for Distinguished Young Scholars(Grant No.51425901)+1 种基金the Qing Lan Project of Jiangsu Provincethe Short-term Research Visits Project supported by Disaster Prevention Research Institute of Kyoto University(Grant No.27S-02)
文摘The characteristics of swells within the East China Sea have been reported by Tao et al.(2017),while the question of where the swells come from remains unanswered.By using the wave model WAVEWATCH III and the swell tracking method proposed by Hanson(2001),the spatial sources of the swells are investigated during four typical typhoon scenarios,which usually affect the wave environment in the East China Sea,including the Recurving type,the Northward type,the Westward type(striking the East China Sea)and the Westward type(over the South China Sea).The numerical results show that parts of the swells are from the North West Pacific with a long-distance travelling.The moving paths of the swells are affected by the typhoon tracks,which result in various fetches.The Westward type(over the South China Sea)makes one peak in the evolution process.The landing process of the Westward type(striking the East China Sea)could result in swells with low energy.The swell energy depends on swell propagation distance,existence time and wind intensity of generation fetch.The consistent fetch and forceful wind intensity make swell carry more energy.
文摘In the original publication of the article(Peng et al.2022),under the section‘Comparisons with experiments and direct numerical simulations’,Fig.4 was not included.The figure is given below:Reference Peng,J.,Tao.,A.F.,Fan,J.,Zheng,J.H.and Liu,Y.M.,2022.On the downshift of wave frequency for Bragg resonance,China Ocean Engineering,36(1),76-85.
