Search

This paper addresses the current existence of attribute reduction algorithms for incomplete hybrid decision-making systems, including low attribute reduction efficiency, low classification accuracy and lack of consideration of unlabeled data types. To address these issues, this paper first redefines the weakly labeled relative neighborhood discernibility degree and develops a non-dynamic attribute reduction algorithm. In addition, this paper proposes an incremental update mechanism for weakly tagged relative neighborhood discernibility degree and introduces a new dynamic attribute reduction algorithm for increasing the set of objects based on it. Meanwhile, this paper also compares and analyses the improved algorithm proposed in this study with two existing attribute reduction algorithms using 8 data sets in the UCI database. The results show that the dynamic attribute reduction algorithm proposed in this paper achieves higher attribute reduction efficiency and classification accuracy, which further validates the effectiveness of the algorithm proposed in this paper. [ABSTRACT FROM AUTHOR]

Abstract During Hurricane Sandy, wave overtopping occurred along the barrier beach in front of the Rehoboth Bay, one of the Delaware Inland Bays, as indicated by field observations and the morphological profile model CSHORE. CSHORE estimated a total overtopping volume of about 9.7 × 10 7 m 3 which is close to the storm surge-induced water volume entering the bays through the inlet (about 1.3 × 10 8 m 3 ). In this study, we incorporated the wave overtopping result from CSHORE into the nearshore community model, NearCoM-TVD, to investigate the wave overtopping-induced excessive surge (OIS) in the Delaware Inland Bays. With the wave overtopping applied in the flux boundary condition, the model successfully reproduced the high water level measured at the station located in the Rehoboth Bay. Additional numerical experiments for the separate effects of wave forcing and local winds are also carried out. The results show that wave forcing has a minimal effect on the water level inside the bays. The adjustment of local wind forcing does not qualitatively improve the agreement between the model and data. The model with included wave overtopping predicted an excessive surge of about 20 cm in the Rehoboth Bay, agreeing better with the measured data. Finally, the responses of OIS to different overtopping conditions were performed using an idealized model setup. A strong asymmetry, represented by a much longer draining period versus a shorter period of overtopping increase to the OIS peak, was found in the OIS process for a given temporally symmetric time series of overtopping flux. The asymmetric feature is caused by the imbalance between the overtopping flux and the discharge through the inter-connecting channel inside the Inland Bays. Nonlinearity plays an important role in the process of OIS as demonstrated in modeling OIS-tide-surge interaction. Highlights • Modeling of excessive surge induced by wave overtopping in an inlet-bay system. • The wave overtopping-induced water volume is close to the storm surge-induced volume entering the bays through the inlet. • Wave overtopping has a significant influence on storm surge inside the bays. • Nonlinearity plays an important role in the interaction between overtopping-induced surge and tide. [ABSTRACT FROM AUTHOR]

In this paper, a numerical wave flume with full functions of wave generation and absorption is proposed under the framework of Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH). In contrast to the conventional SPH numerical wave flumes using wave paddles and sponge layers, the wave generation and absorption in this paper are implemented using non-reflective open boundary conditions, which are capable of generating multiple types of waves, including solitary waves, linear and second-order regular waves. Passive and active wave absorption are available for transmitting incident waves and preventing secondary reflections. Steady or unsteady flows can also be defined during wave generation and absorption to set up numerical wave-flow flumes. The results on a series of validation cases indicate that this SPH numerical wave flume not only performs satisfactorily in conventional wave generation and absorption and nonlinear wave-structure interaction simulations but also has the following three advantages: 1) It avoids using the sponge layers to shorten the flumes, which improves the efficiency; 2) it keeps the mean water level steady and prevents water level shifting; and 3) it implements steady/unsteady flow and wave-flow interactions to model a wider range of hydrodynamic problems. [ABSTRACT FROM AUTHOR]

Based on the linear shallow water approximation, longitudinal and transverse oscillations in a rectangular harbor with a parabolic bottom are analyzed. The longitudinal ones are combinations of the Legendre functions of the first and second kinds and the transverse ones are expressed with modified Bessel equations. Analytic results for longitudinal oscillations show that the augmentation of rapidity of variation of the water depth shifts the resonant wave frequencies to larger values and slightly changes the positions of the nodes for the resonant modes. For the transverse oscillations trapped within the harbor which are typically standing edge waves, the dispersion relationship is derived and the spatial structures of the first four modes are presented. The solutions illustrate that all the trapped modes are affected by the varying water depth parameters, especially for the higher modes whose profiles extend farther and the distribution of the energy of transverse oscillations is influenced by the rapidity of variation of the bottom within the harbor. [ABSTRACT FROM AUTHOR]

Cao, H.; Feng, W., and Chen, Y., 2016. Numerical modeling of wave transformation and runup reduction by the coastal vegetation of the South China Sea. Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 830-835. Coconut Creek (Florida), ISSN 0749-0208. The aim of this study is to examine wave transformation and runup using a numerical model of coastal conditions including vegetation. Based on the previous field study, the drag coefficient was estimated using an analytical model. After that, numerical modeling of wave dissipation in SWASH (Simulating WAves until SHore) was conducted and validated with the observed data. Furthermore, calibrated SWASH was used to inspect the wave runup under vegetated and non-vegetated cases. For the flexibility of numerical modeling, We also used the numerical model to assess various vegetation parameters and beach slopes to inform the characteristics of wave runup reduction. The results of the model indicate that SWASH with proper parameters accurately simulated wave dissipation. Wave runup and setup were significantly reduced by the coastal vegetation. The numerical results suggest that vegetation parameters and beach slope are important factors when analyzing the wave runup reduction rate. [ABSTRACT FROM AUTHOR]

This paper presents an incorporation of vegetation-induced wave dissipation in a planar numerical wave propagation model based on the extended mild-slope equation (EMSE). The implementation was incorporated in a purely mathematical method in the light of current theoretical studies. To examine the performance of the phase-resolving model, a comprehensive comparison with phase-averaged SWAN is made to test and validate the implementation. Moreover, new in-situ measurements in a mangrove forest are presented aiming to test the wave energy damping by vegetation using the observed wave spectra. From our validation results it can be concluded that wave dissipation due to vegetation is equally well reproduced in this model. It is found that the wave parameters (wave height and period) and vegetation parameters (plant width, height and density) are all influencing factors. An interesting finding is that relatively high-frequency waves are more dissipated than low frequency waves, especially for larger wave heights. In this study, we found that diffraction is of great significance in wave propagation over inhomogeneously distributed vegetation. Theoretically, the phase resolving EMSE represents the physical process of diffraction better than the phase-averaged model SWAN. [ABSTRACT FROM AUTHOR]

In this paper, a novel method to construct non-intrusive reduced order model (ROM) is proposed. The method is based on proper orthogonal decomposition and transformer neural network. Proper orthogonal decomposition is used to generate the basis functions of the low-dimensional flow field, and the coefficients are taken as low-dimensional flow field features. Transformer network is used to extract temporal feature relationships from low-dimensional features. Compared with recurrent neural network and convolutional neural network, transformer network can better capture flow dynamics. At online stage, the input temporal flow sequences are calculated in parallel and can effectively reduce online calculation time. The model proposed in this paper has been verified in two scenarios: two-dimensional flow past a cylinder and two-dimensional flow past a building group. Experimental results show that our model can better capture the flowing change details and has higher accuracy. Compared with the ROM based on long short-term memory and temporal convolutional network, the prediction error is reduced by 35% and 60%, and the time cost is reduced by 65% and 60%. Finally, we apply the ROMs to a practical three-dimensional complicated scenario, flow past London South Bank University, and discuss future development of ROMs. [ABSTRACT FROM AUTHOR]

Balancing the trade-off between the simulation detail and the computational efficiency in a hydrodynamic numerical model is generally difficult, e.g., one can hardly find a single set of governing equations that is capable of efficiently describing the wave propagation processes from offshore to nearshore and accurately presenting the details of wave breaking and interacting with coastal structures simultaneously. To address this predicament, open boundary coupling schemes are proposed in this paper to hybridize a SWE (shallow water equations)-based SPH (Smoothed Particle Hydrodynamics) model with a NS (Navier-Stokes) equations-based SPH model. The NS-SPH model is used to present the nonlinear hydrodynamic features in the main study domains, while the remaining domains are simulated with the SWE-SPH model, which calculates much faster than the NS-SPH model. The hybrid SPH models are applied to simulate solitary wave propagation, steady flows over a bump, dam breaking waves and standing waves. The hybridization performance on the information transmitting, mass and energy conservation, simulation detail, computational accuracy, computational efficiency and computational convergence speed is fully validated and evaluated. The results indicate that the proposed open boundary coupling schemes are capable of improving the computational efficiency on the premise of computational accuracy and simulation detail. • A two-way open boundary coupling scheme is proposed for the hybridization of SPH models. • The one-way coupling scheme is modified with a nonreflective open boundary condition. • The coupling schemes improve computational efficiency on the premise of accuracy. [ABSTRACT FROM AUTHOR]

ABSTRACT Ni X.; Huang S.; Feng W., and Yao W., 2018. Numerical simulation of tidal bores using SPH method. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 951–956. Coconut Creek (Florida), ISSN 0749-0208. A tidal bore is a natural hydraulic phenomenon normally formed in funnel-shaped estuaries with large tidal ranges. Water levels and flow velocities change rapidly in both magnitude and direction when a tidal bore arrives. These strongly nonlinear water body movements have significant influences on scouring and deposition processes along the riverbed and produce hydrodynamic impacts on piers and dikes. In this paper, a mesh-free numerical method known as the smoothed particle hydrodynamics (SPH) method is used to implement a numerical model capable of handling complex free-surface flows and solve the Navier-Stokes equations with a large-eddy simulation. A tidal bore generation scheme suited for a mesh-free numerical method is also proposed based on the SPH open boundary technique. Various types of tidal bores, including undular bores, weakly breaking bores and breaking bores, are simulated and validated with measured data. The numerical results represent the evolutionary processes and hydrodynamic characteristics of tidal bores ranging from weak to strong intensities. The generation and evolution of dipole substructures in breaking tidal bores are also discussed. By studying the bed shear stresses and depth-averaged vorticities of the tidal bores, it can be concluded that the sediment incipience intensity grows nonlinearly in the second order with an increase in the tidal bore intensity, while the sediment transportation intensity grows linearly. [ABSTRACT FROM AUTHOR]

Ni X.; Huang S.; Feng W., and Yao W., 2018. Numerical simulation of tidal bores using SPH method. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 951–956. Coconut Creek (Florida), ISSN 0749-0208. A tidal bore is a natural hydraulic phenomenon normally formed in funnel-shaped estuaries with large tidal ranges. Water levels and flow velocities change rapidly in both magnitude and direction when a tidal bore arrives. These strongly nonlinear water body movements have significant influences on scouring and deposition processes along the riverbed and produce hydrodynamic impacts on piers and dikes. In this paper, a mesh-free numerical method known as the smoothed particle hydrodynamics (SPH) method is used to implement a numerical model capable of handling complex free-surface flows and solve the Navier-Stokes equations with a large-eddy simulation. A tidal bore generation scheme suited for a mesh-free numerical method is also proposed based on the SPH open boundary technique. Various types of tidal bores, including undular bores, weakly breaking bores and breaking bores, are simulated and validated with measured data. The numerical results represent the evolutionary processes and hydrodynamic characteristics of tidal bores ranging from weak to strong intensities. The generation and evolution of dipole substructures in breaking tidal bores are also discussed. By studying the bed shear stresses and depth-averaged vorticities of the tidal bores, it can be concluded that the sediment incipience intensity grows nonlinearly in the second order with an increase in the tidal bore intensity, while the sediment transportation intensity grows linearly. [ABSTRACT FROM AUTHOR]

Analytical and numerical investigations are carried out for harbor oscillations on a piecewise bottom of two different slopes. With the shallow water approximation, the longitudinal and transverse oscillations are analyzed by coupling the solutions on each segment of the bottom with the coupling conditions at the point of inflection in ignoring the nonlinear interactions between them. The longitudinal ones are the combinations of the Bessel functions of the first and second kinds, and the transverse ones are expressed with Kummer's equations. As the transverse oscillations trapped within the harbor are typically standing edge waves, their dispersion relationship is also derived for the two-slope-piecewise bottom. With the analytical predictions of the oscillation behaviors and based on Boussinesq equations, a range of numerical tests are made for the oscillations induced by seafloor motions on this type of piecewise bottom. Different combinations of the two slopes of the bottom are firstly tested and the numerical eigenfrequencies and wave profiles are compared with analytical ones. The transverse oscillations are revealed to be sensitive to the positions of the seafloor movements, and the importance of the position of the seafloor motions is manifested in their relative positions against the nodal lines and anti-nodal lines of the transverse modes. Although the longitudinal oscillations generated by seafloor motions of harbor width may not reach a steady state without forcing terms at the entrance, some patterns of several low-mode ones occur and are also sensitive to the position of the moveable seafloor. Wavelet spectra are used to analyze their evolutions and comparisons are made with theoretical predictions for the three principle longitudinal modes. [ABSTRACT FROM AUTHOR]

Oscillations within a rectangular harbor of constant slope induced by submerged sliding masses are investigated numerically based on Boussinesq-type equations and results are used to reveal the characteristics of the generated oscillations. The numerical result of each transverse eigenfrequency is very close to the theoretical prediction and the spatial structure of each mode of the oscillations may also be well captured by the existing analytical solutions based on shallow water equations. The investigation shows that relatively small-scale sliding masses whose width is small compared with the harbor width may induce obvious transverse oscillations. The predominant transverse components are those with small mode numbers when the solid slides start moving from the backwall. In comparing the oscillations induced by the slides of constant velocity and those accelerated by gravity force with bottom friction, it is observed that the movements accelerated by gravity force may facilitate the development of very low transverse oscillation modes while those with constant velocity may also be in favor of the higher ones. The augmentation of the sliding velocity along the constant slope may shift the amplitudes of the oscillation components to smaller values, which corresponds to the physical understandings of the waves generated by underwater sliding masses or landslides. While the sliding masses may not act on an isolated point of the bottom but follow a certain trajectory along the harbor, the transverse oscillations induced by them are sensitive to their position of departure in both the cross-harbor direction and the offshore direction. Longitudinal oscillations may be induced by relatively large sliding masses of harbor width on a constant slope within the harbor. Although the longitudinal oscillations may not reach a steady state without forcing terms at the entrance of the harbor, some patterns of several low-mode ones occur and wavelet spectra are used to analyze their evolutions and comparisons are made with theoretical predictions. It is revealed that the longitudinal oscillations are also sensitive to the moving velocity and initial location of the sliding masses. [ABSTRACT FROM AUTHOR]

The smoothed particle hydrodynamics (SPH) technique is a mesh-free numerical method that has great potential to be used in the development of the next generation of numerical ocean models. The implementation of open and solid boundary conditions in the SPH method, however, is not as straightforward as the mesh-based numerical methods. Two types of open boundary conditions are considered in this study: the adaptive open boundary condition (AOBC) and Flather's open boundary condition (FOBC). These two open boundary conditions are implemented in the SPH-based shallow-water equation (SWE) circulation model for simulating sea surface elevations and depth-mean currents over a limited area with open boundaries. The performance of these two open boundaries is assessed in four numerical test cases. In comparison with the conventional characteristic open boundary condition, both the AOBC and the FOBC allow perturbations to propagate out more effectively and are easy to implement with the specification of external flow conditions at the model open boundaries. The model results also demonstrate that the AOBC requires an accurate estimation of the phase speed of perturbations and could lead to a small drift in the mean water level. By comparison, the FOBC is computationally more efficient without any model drift. The SPH-based SWE circulation model is also used in simulating the laboratory observations of the 1993 Okushiri Tsunami. The numerical results in this case demonstrate the feasibility and capability of the SPH-based SWE model for simulating free-surface flows in regions with complicated bathymetry and irregular coastline. [ABSTRACT FROM AUTHOR]

Oscillations within a rectangular harbor of parabolic bottom induced by water surface disturbances are investigated numerically based on Boussinesq equations and results are used to reveal the characteristics of the oscillations generated by disturbances of this type. The similarities and differences compared with those generated by a movable seafloor are also discussed. Relatively local and small-scale water surface disturbances may induce obvious transverse oscillations with little trace of longitudinal ones. The predominant transverse components are those with small alongshore mode number m and no node in the offshore direction. The augmentation of the rapidity of depth variation of the parabolic bottom may shift the resonant frequencies to larger values. These transverse modes are sensitive to the initial position of water surface disturbances. The spatial structure of each mode is well captured by the existing analytical solution based on shallow water equations. Although longitudinal oscillations may not be steadily generated with water surface disturbances, some patterns of several low-mode ones occur and are also sensitive to the position of the disturbances. Wavelet spectra are used to analyze their evolutions and comparisons are made with theoretical predictions for the three principle longitudinal modes. [ABSTRACT FROM AUTHOR]

In this paper, a novel reduced order model based on a convolutional auto-encoder with self-attention (SACAE ROM) is proposed. The proposed model is a non-intrusive reduced order model, which uses a convolutional neural network and a long short-term memory network to extract temporal feature relationships from high-fidelity numerical solutions. The self-attention is introduced into the convolutional neural network to enhance the non-local information perception ability of the convolutional neural network and improve the feature extraction ability of the network. The model adopts a joint construction method, which overcomes the problem of propagating error in each process of the model. The model proposed in this paper has been verified on the problem of the flow around a cylinder. The experimental results indicate that the SACAE ROM has higher robustness and accuracy. Compared with the ROM based on a convolutional auto-encoder, the prediction error of the SACAE ROM is reduced by 42.9%. As with other ROMs based on deep neural networks, the SACAE ROM takes a long time to train. To solve this problem, the transfer and generalization ability of the model is studied in this paper. In the experiment, the flow velocity and spoiler of the flow around the cylinder were changed, and the training time of the transfer model was reduced by about 50% to 60%. This result demonstrates that the problem of too long training time can be solved by transfer learning. [ABSTRACT FROM AUTHOR]

Cao, H.; Chen, Y.; Tian, Y., and Feng, W., 2016. Field investigation into wave attenuation in the mangrove environment of the South China Sea coast. Coastal mangroves form the land-sea interface and face an increasingly aggressive threat from ocean waves as a result of sea-level rise. This study investigates the buffering effect of mangroves on the coast of Leizhou Bay in the South China Sea under two different climates (normal windy weather and storm). By doing this, we aim to establish the exact wave damping rate due to the presence of mangroves and to study the wave and spectral characteristics of wave energy in the vegetated area. Wave gauges are mounted along a cross-shore transect to monitor the wave conditions during particular time periods. From the data analysis, we found that the recorded maximum significant wave height is 22.3 cm at the outermost station and remarkable wave damping was experienced within the mangrove troops of 100 meters. To evaluate the wave dissipation on the mudflat, an empirical expression is proposed on the basis of the field data. In this way, the net vegetation-induced wave dissipation is quantified separately. The spectral analysis of wave energy shows the modalities of frequency-dependent wave energy dissipation under different weather conditions. From the results, we conclude that the wave height was strictly subjected to the concurrent water depth even under the storm condition. The relative water depth (to the wave height) determined wave generation or dissipation on the mudflat. Despite the existence of dissipation by the mudflat, wave energy was majorly attenuated by the mangrove system. The wind growth of wave energy is of great significance when studying the spectral characteristics of wave energy during storm conditions. [ABSTRACT FROM AUTHOR]

Vertical breakwaters are commonly built on the shore, and their existence must influence the character of nearshore dynamics. Analytical solutions based on linear-shallow water equation are derived for edge waves on a convex exponential profile which may be used to idealize the actual bottom profile with a vertical breakwater at the shoreline. The free surface elevation of the edge waves is described using the first kind of the Bessel functions of order ν. The amplitude profiles are similar to those of edge waves on a sloping beach but confined to a narrower offshore domain near the vertical breakwater. The dispersion relationship is derived from the no-flux boundary condition at the vertical breakwater. The wave number is not only related to the frequency but also the water depth at the vertical breakwater and the profile parameter. The group velocity increases rapidly to the maximum value with the increase of frequency, then decreases slowly and finally approaches the classic shallow water wave celerity of the depth at the vertical breakwater. The possible reason for this distinct behavior may be because dynamic characteristics of edge waves are highly dependent on the profile. Moreover, an extensively validated Boussinesq wave model is used to conduct numerical experiments for edge waves induced by surface bumps. The numerical results are consistent with the proposed solutions, confirming the validity of the new analytical solutions. • Analytical solutions of edge waves on a convex exponential profile are derived. • The amplitude profiles are similar to those of edge waves on a sloping beach but confined to a narrower offshore domain. • The group velocity increases rapidly to the maximum and then decreases slowly with the increase of frequency. • Numerical experiments are conducted to validate the proposed analytical solutions. • The study is hoped to improve the understanding of edge waves on a convex exponential profile. [ABSTRACT FROM AUTHOR]

It is necessary to optimize the design of the missile aerodynamic shape for better performance while meeting tactical specifications. However, current design methods for aerodynamic shape are based on manual design and physical model simulations, which are very time-consuming. Therefore, we propose an optimization framework based on conditional Wasserstein Gan-GP (CWGAN-GP), convolutional neural network (CNN), multi-task learning with multi-gate mixture-of-Experts-3D (MMoE-3D) and differential evolution (DE). This method consists of four stages. In the first step, CWGAN-GP can learn the relationship between existing missile shape designs and shape conditions, generating diverse missile shapes as required. In the second step, CNN is used for feature extraction of missile design drawing, and the missile shape generated by CWGAN-GP is transformed into missile shape parameters. In the third step, the MMoE-3D model is trained in the subsonic and supersonic ranges to efficiently generate aerodynamic data corresponding to the missile shape. In the fourth step, DE is used to select the optimal missile shape by adjusting the potential variables of CWGAN-GP. The efficiency of the proposed optimization framework is verified by optimizing the rate of change of the center of pressure and the lift-to-drag ratio, with the neural network-based optimization framework achieving almost the same optimization results in a shorter time compared to conventional optimization with DATCOM. [ABSTRACT FROM AUTHOR]

Numerical simulation in Computational Fluid Dynamics mainly relies on discretizing the governing equations in time or space to obtain numerical solutions, which is expensive and time-consuming. Deep learning significantly reduces the computational cost due to its great nonlinear curve fitting capability, however, the data-driven models is agnostic to latent relationships between input and output. In this paper, a novel deep learning named Navier–Stokes Generative Adversarial Network integrated with physical information is proposed. The Navier–Stokes Equation is added to the loss function of the generator in the form of residuals, which means physics loss in this paper. Then, the proposed model is trained in the framework of generative adversarial network. Experimental results show that proposed model significantly outperform similar models, mean absolute error are decreased by 62.29, 78.42 and 78.61% on pressure and velocity components. What’s more, effectiveness of introducing physics loss is also verified. [ABSTRACT FROM AUTHOR]

A deterministic Extreme Value Analysis method is of particular importance in an engineering-oriented context. In this paper, three extreme value analysis (EVA) methods, in which annual maxima, monthly maxima or the Peaks-Over-Threshold are fitted into Generalized Extreme Value distribution (GEV) function or Generalized Pareto distribution (GP) function, are used to estimate return values of significant wave height. Sensitivity of return levels on water depth and sampling length is vigorously investigated, based on a 40-year long and high-resolution wave hindcast for the South Yellow Sea (SYS). A spatially-and-temporally varied POT sampling method combined with GP function produces most conservative and confident estimates of return levels for a large return period, but produces wider confidence level than the other two EVA approaches based on GEV function for short return period. In the SYS, the return level estimates are significantly reduced with a longer sample length. However, we find that the reduction is closely related to the long-term trend in extreme wave heights, rather than due to the sampling effect. From deep to shallow waters, spatial inhomogeneity of return levels increases, which should be considered in the engineering practice. • A sophisticated investigation was conducted on the dependence of the return level of extreme wave heights in the SYS to the epistemic and intrinsic factors. • GEV distribution model is more confident in short-term return level estimates, whilst GP distribution model is more confident for long-term return level estimates. • The inter-tidal region although is least sensitive to sampling length for the return level estunates, whilst contains the largest spatial inhomogeneity of extreme wave heights. • A temporal negative long-term trend was found in the return levels of extreme wave height in the SYS. [ABSTRACT FROM AUTHOR]

Feng, X.; Dong, B.X.; Ma, G.F., and Feng, W.B., 2020. Topographic and hydrodynamic influence on rip currents and alongshore currents on headland beaches in China. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 468–473. Coconut Creek (Florida), ISSN 0749-0208. Headland beaches are one of the most typical beaches in southern China. Meanwhile, southern China seas experienced severe rip current hazards. In this paper, numerical simulations were carried out by utilizing Delft 3D Flow-Wave coupling model. Ideal topography of different headland beaches was established and the variabilities in the rip currents' forms and the hydrodynamics from the major headland beach patterns were discussed, including the relative headland length (α= Lhead/Lbeach), the curvature of shoreline (k = Ls/Lc), the wave direction (θ) and the wave height (hs). Results revealed that four factors, including α, k, θ and hs, all have some influences on the nearshore circulation. The shape of the coastline influenced the position of alongshore current and the appearance of headland rip. The length of headland and the wave height influenced the intensity and the spatial distribution of nearshore circulation mainly. Besides, wave direction was the most important factor for channel rip. Because it played a decisive role in the generation of channel rip. [ABSTRACT FROM AUTHOR]