Natural and human-induced changes may exert considerable impacts on the seasonal and nodal dynamics of M2 and K1 tidal constituents.Therefore,quantifying the influences of these factors on tidal regime changes is esse...Natural and human-induced changes may exert considerable impacts on the seasonal and nodal dynamics of M2 and K1 tidal constituents.Therefore,quantifying the influences of these factors on tidal regime changes is essential for sustainable water resources management in coastal environments.In this study,the enhanced harmonic analysis was applied to extract the seasonal variability of the M2 and K1 tidal amplitudes and phases at three gauging stations along Lingdingyang Bay of the Zhujiang River Delta.The seasonal dynamics in terms of tidal wave celerity and amplification/damping rate were used to quantify the impacts of human-induced estuarine morphological alterations on M2 and K1 tidal hydrodynamics in inner and outer Lingdingyang Bay.The results show that both tidal amplification/damping rate and wave celerity were considerably increased from the pre-anthropogenic activity period(Pre-AAP)to the post-anthropogenic activity period(Post-AAP)excepting the tidal amplification/damping rate in outer Lingdingyang Bay,and the variations in outer Lingdingyang Bay was larger than those in inner Lingdingyang Bay.The alterations in these two parameters were more significant in flood season than in dry season in both inner and outer Lingdingyang Bay.The seasonal variability of M2 and K1 tidal amplitudes were further quantified using a regression model accounting for the 18.61-year lunar nodal modulation,where this study observes a considerable alteration in M2 constituent owing to human interventions.During the Post-AAP,the M2 amplitudes at the downstream station were larger than those that would have occurred in the absence of strong human interventions,whereas the opposite was true for the upstream station,leading to a substantial decrease in tidal amplification in outer Lingdingyang Bay.However,it is opposite in inner Lingdingyang Bay.The underlying mechanism can be primarily attributed to channel deepening and narrowing caused by human interventions,that resulted in substantial enlargement of the bay volume and reduced the effective bottom friction,leading to faster wave celerity and stronger amplified waves.展开更多
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
In this research the bed friction effect is estimated of a river estuary by use of hydrodynamic analysis. The on-site sampled data of the Wu River estuary is applied to the analysis. There are many dynamic factors tha...In this research the bed friction effect is estimated of a river estuary by use of hydrodynamic analysis. The on-site sampled data of the Wu River estuary is applied to the analysis. There are many dynamic factors that affect the flow characteristics in the estuary. The effect of tide on the generation of tidal current, bottom friction and geometry effect is the focus of this paper. The Wu River estuary is about 15 hn in length, with a small bottom slope and no physical obstruction; thus the incident wave at the estuary is considered a progressive wave with damping effect. The amplitude reduction and phase shift of the incident wave are analyzed. By the analysis of celerity reduction factor of the estuary, the estimated value of mean resistance coefficient M（μ ,κ）, damping modulus μ, and wave number κ for the sections at observation stations can be determined. Furthermore, data gathered from on-site observations are applied for validation. Finally, Manning＇ s coefficient for each section of the observation stations can be determined. It is found that the value of Manning＇ s coefficient is small downstream and increases towards upstream, and that the bed friction effect of an estuary varies largely. The estimated results of the paper are compared with the empirical formulas and the modified solution for practical application is discussed.展开更多
For a century, hypothesis of a variable time is laid down by the Relativity Theory. This hypothesis can explain many Nature observations, experiments and formulas, for example the Lorentz factor demonstration. Because...For a century, hypothesis of a variable time is laid down by the Relativity Theory. This hypothesis can explain many Nature observations, experiments and formulas, for example the Lorentz factor demonstration. Because of such good explanations, the hypothesis of a variable time has been validated. Nevertheless, it remains some paradoxes and some predictions which are difficult to measure, as a reversible time or the time variation itself. The purpose of this article is to study another hypothesis. If it gives interesting results, it would mean that this alternative hypothesis can also be validated. The idea in this paper is to replace the variable time by a variable inertial mass. To the difference with the Theory of Relativity (where the inertial mass and the gravitational mass are equal and variable), the gravitational mass is here supposed to be constant. So, starting from the definition of the kinetic energy, it is introduced the Lorentz factor. And then it is demonstrated the value of the Lorentz factor thanks to a variable inertial mass. This variable inertial mass can also explain experiments, like Bertozzi experiment. If this alternative demonstration was validated, it could help to open doors, other physical effects could be explained like the addition of velocities.展开更多
Is it possible to demonstrate the velocity addition without using a variable time (as it is done in theory of relativity)? The topic of this paper is to propose and demonstrate an alternative expres-sion based on the ...Is it possible to demonstrate the velocity addition without using a variable time (as it is done in theory of relativity)? The topic of this paper is to propose and demonstrate an alternative expres-sion based on the conservation of linear momenta. The method proposed here is to start from a physical object (and not from a mathematical point), i.e. from an object with a mass. And the hy-pothesis is inertial mass to be different from gravitational mass. Then, when impulses are added, we get an expression of the velocity addition itself. When numerical predictions are compared with experimental results, the differences are lower than the measures uncertainty. And these numerical results are much close to those predicts by the theory of relativity, nevertheless with a little difference at high velocities. If this demonstration and this expression were validated, it would allow giving an alternative explanation to some experiments and nature observations as Doppler Effect on light celerity. But first, it would be necessary to get from laboratories more precise experimental results, in order to validate or not this hypothesis of the sum of linear momenta with a Variable Inertial Mass.展开更多
The speed away of stars and galaxies is traditionally calculated from the relativistic formula according to the measurement of the redshift. It is demonstrated here another formula for this speed away of stars and gal...The speed away of stars and galaxies is traditionally calculated from the relativistic formula according to the measurement of the redshift. It is demonstrated here another formula for this speed away of stars and galaxies, from this same redshift <em>z</em>. After having exposed critiques on the demonstration and the relativistic use which require the assumption of an expanding universe by itself, it is proposed within the framework of neo-Newtonian mechanics the formula <img src="Edit_5abcd41b-f0f0-4fdd-8d05-07b43d1fa78c.png" alt="" /> where <em>V</em> is the speed from the source. This formula has the double characteristic of being equivalent to relativistic predictions for low redshifts, but of deviating from them by up to 17% for high redshifts. It is consistent with the observation of the anisotropy of the Universe and the Cosmic Microwave Background. It helps to explain Pioneer anomalies. It is compatible with the constancy in the majority of cases of interference phenomena. Finally, it provides a new analysis grid for the observation of supernovae, galaxies and distant pulsars, thus opening up new fields of research on the increase in distances attributed to dark energy and also in other areas of the cosmology.展开更多
Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental under...Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental understanding of geomorphic processes. In the Yalu River-Wangtian＇e volcanic region of northeastern China, broadly distributed fiat lava terrain provides an ideal site to study the recession of fluvial knickpoints because knickpoints and waterfalls are well preserved here. Here we describe the distribution of knickpoints in the Yalu River-Wangtian＇e volcanic region by combining DEM analysis and numerical modeling Furthermore, we present a knickpoint celerity model, derived from stream-power incision model, to relate knickpoint recession rate to drainage area. We calibrate important empirical coefficients with our knickpoint celerity model; the best fit erosion coefficient （K） is 1.32×10^-8, and the best fit drainage area exponent （m） is 0.69. Error analysis indicates a close correspondence between synthetic and real knickpoints. Finally, we show that knickpoint recession rates in the Yalu River-Wangtian＇e volcanic region are -1-10 mm/a during the early stages of transient incision, and that the present rates are -1-6 mm/a. Our recession rate results are in good agreement with previous findings from the Aso Volcano and volcanoes near Boso Peninsula （Japan）, which have a similar geologic history to the Yalu River-Wangtian＇e volcanic region. Our present effort provides new insight into landscape evolution in the Yalu River-Wangtian＇e volcanic region in northeastern China.展开更多
One important kinematic propertie of breaking waves is the wave celerity. Constant wave celerity has been used for the wave breaking criterion by many researchers. However, this approach does not consider the variatio...One important kinematic propertie of breaking waves is the wave celerity. Constant wave celerity has been used for the wave breaking criterion by many researchers. However, this approach does not consider the variation of wave celerity at different phases before breaking. Hence, this article examines the aspects of the wave breaking criterion and dynamics of wave celerity before wave breaking. Breaking waves were generated using the JONSWAP focused spectrum and a semi-empirical formula for the wave celerity estimation was established.展开更多
基金The National Key R&D Program of China under contract No.2016YFC0402600the National Natural Science Foundation of China under contract No.51979296the Guangzhou Science and Technology Program of China under contract No.202002030452。
文摘Natural and human-induced changes may exert considerable impacts on the seasonal and nodal dynamics of M2 and K1 tidal constituents.Therefore,quantifying the influences of these factors on tidal regime changes is essential for sustainable water resources management in coastal environments.In this study,the enhanced harmonic analysis was applied to extract the seasonal variability of the M2 and K1 tidal amplitudes and phases at three gauging stations along Lingdingyang Bay of the Zhujiang River Delta.The seasonal dynamics in terms of tidal wave celerity and amplification/damping rate were used to quantify the impacts of human-induced estuarine morphological alterations on M2 and K1 tidal hydrodynamics in inner and outer Lingdingyang Bay.The results show that both tidal amplification/damping rate and wave celerity were considerably increased from the pre-anthropogenic activity period(Pre-AAP)to the post-anthropogenic activity period(Post-AAP)excepting the tidal amplification/damping rate in outer Lingdingyang Bay,and the variations in outer Lingdingyang Bay was larger than those in inner Lingdingyang Bay.The alterations in these two parameters were more significant in flood season than in dry season in both inner and outer Lingdingyang Bay.The seasonal variability of M2 and K1 tidal amplitudes were further quantified using a regression model accounting for the 18.61-year lunar nodal modulation,where this study observes a considerable alteration in M2 constituent owing to human interventions.During the Post-AAP,the M2 amplitudes at the downstream station were larger than those that would have occurred in the absence of strong human interventions,whereas the opposite was true for the upstream station,leading to a substantial decrease in tidal amplification in outer Lingdingyang Bay.However,it is opposite in inner Lingdingyang Bay.The underlying mechanism can be primarily attributed to channel deepening and narrowing caused by human interventions,that resulted in substantial enlargement of the bay volume and reduced the effective bottom friction,leading to faster wave celerity and stronger amplified waves.
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.
文摘In this research the bed friction effect is estimated of a river estuary by use of hydrodynamic analysis. The on-site sampled data of the Wu River estuary is applied to the analysis. There are many dynamic factors that affect the flow characteristics in the estuary. The effect of tide on the generation of tidal current, bottom friction and geometry effect is the focus of this paper. The Wu River estuary is about 15 hn in length, with a small bottom slope and no physical obstruction; thus the incident wave at the estuary is considered a progressive wave with damping effect. The amplitude reduction and phase shift of the incident wave are analyzed. By the analysis of celerity reduction factor of the estuary, the estimated value of mean resistance coefficient M（μ ,κ）, damping modulus μ, and wave number κ for the sections at observation stations can be determined. Furthermore, data gathered from on-site observations are applied for validation. Finally, Manning＇ s coefficient for each section of the observation stations can be determined. It is found that the value of Manning＇ s coefficient is small downstream and increases towards upstream, and that the bed friction effect of an estuary varies largely. The estimated results of the paper are compared with the empirical formulas and the modified solution for practical application is discussed.
文摘For a century, hypothesis of a variable time is laid down by the Relativity Theory. This hypothesis can explain many Nature observations, experiments and formulas, for example the Lorentz factor demonstration. Because of such good explanations, the hypothesis of a variable time has been validated. Nevertheless, it remains some paradoxes and some predictions which are difficult to measure, as a reversible time or the time variation itself. The purpose of this article is to study another hypothesis. If it gives interesting results, it would mean that this alternative hypothesis can also be validated. The idea in this paper is to replace the variable time by a variable inertial mass. To the difference with the Theory of Relativity (where the inertial mass and the gravitational mass are equal and variable), the gravitational mass is here supposed to be constant. So, starting from the definition of the kinetic energy, it is introduced the Lorentz factor. And then it is demonstrated the value of the Lorentz factor thanks to a variable inertial mass. This variable inertial mass can also explain experiments, like Bertozzi experiment. If this alternative demonstration was validated, it could help to open doors, other physical effects could be explained like the addition of velocities.
文摘Is it possible to demonstrate the velocity addition without using a variable time (as it is done in theory of relativity)? The topic of this paper is to propose and demonstrate an alternative expres-sion based on the conservation of linear momenta. The method proposed here is to start from a physical object (and not from a mathematical point), i.e. from an object with a mass. And the hy-pothesis is inertial mass to be different from gravitational mass. Then, when impulses are added, we get an expression of the velocity addition itself. When numerical predictions are compared with experimental results, the differences are lower than the measures uncertainty. And these numerical results are much close to those predicts by the theory of relativity, nevertheless with a little difference at high velocities. If this demonstration and this expression were validated, it would allow giving an alternative explanation to some experiments and nature observations as Doppler Effect on light celerity. But first, it would be necessary to get from laboratories more precise experimental results, in order to validate or not this hypothesis of the sum of linear momenta with a Variable Inertial Mass.
文摘The speed away of stars and galaxies is traditionally calculated from the relativistic formula according to the measurement of the redshift. It is demonstrated here another formula for this speed away of stars and galaxies, from this same redshift <em>z</em>. After having exposed critiques on the demonstration and the relativistic use which require the assumption of an expanding universe by itself, it is proposed within the framework of neo-Newtonian mechanics the formula <img src="Edit_5abcd41b-f0f0-4fdd-8d05-07b43d1fa78c.png" alt="" /> where <em>V</em> is the speed from the source. This formula has the double characteristic of being equivalent to relativistic predictions for low redshifts, but of deviating from them by up to 17% for high redshifts. It is consistent with the observation of the anisotropy of the Universe and the Cosmic Microwave Background. It helps to explain Pioneer anomalies. It is compatible with the constancy in the majority of cases of interference phenomena. Finally, it provides a new analysis grid for the observation of supernovae, galaxies and distant pulsars, thus opening up new fields of research on the increase in distances attributed to dark energy and also in other areas of the cosmology.
基金supported jointly by National Science Foundation of China (Grant Nos. 40702028, 41030317)State Key Laboratory of Earthquake Dynamics (Grant Nos. LED2009A06,LED2008A02)Zhang Huiping was also supported as a visiting professor to CU by China Scholarship Council (Grant No. 2007106279)
文摘Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental understanding of geomorphic processes. In the Yalu River-Wangtian＇e volcanic region of northeastern China, broadly distributed fiat lava terrain provides an ideal site to study the recession of fluvial knickpoints because knickpoints and waterfalls are well preserved here. Here we describe the distribution of knickpoints in the Yalu River-Wangtian＇e volcanic region by combining DEM analysis and numerical modeling Furthermore, we present a knickpoint celerity model, derived from stream-power incision model, to relate knickpoint recession rate to drainage area. We calibrate important empirical coefficients with our knickpoint celerity model; the best fit erosion coefficient （K） is 1.32×10^-8, and the best fit drainage area exponent （m） is 0.69. Error analysis indicates a close correspondence between synthetic and real knickpoints. Finally, we show that knickpoint recession rates in the Yalu River-Wangtian＇e volcanic region are -1-10 mm/a during the early stages of transient incision, and that the present rates are -1-6 mm/a. Our recession rate results are in good agreement with previous findings from the Aso Volcano and volcanoes near Boso Peninsula （Japan）, which have a similar geologic history to the Yalu River-Wangtian＇e volcanic region. Our present effort provides new insight into landscape evolution in the Yalu River-Wangtian＇e volcanic region in northeastern China.
基金Singapore Economic Development Board(EDB)Lloyd’s Register Singapore Pte Ltd for funding this project work
文摘One important kinematic propertie of breaking waves is the wave celerity. Constant wave celerity has been used for the wave breaking criterion by many researchers. However, this approach does not consider the variation of wave celerity at different phases before breaking. Hence, this article examines the aspects of the wave breaking criterion and dynamics of wave celerity before wave breaking. Breaking waves were generated using the JONSWAP focused spectrum and a semi-empirical formula for the wave celerity estimation was established.
