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1.
《中国海洋湖沼学报》2019,(6)
In this study, typhoon waves generated during three typhoons(Damrey(1210), Fung-wong(1416), and Chan-hom(1509)) in the Yellow Sea and East China Sea were simulated in a simulating waves nearshore(SWAN) model, and the wind forcing was constructed by combining reanalyzed wind data with a Holland typhoon wind model. Various parameters, such as the Holland fitting parameter(B) and the maximum wind radius(R), were investigated in sensitivity experiments in the Holland model that affect the wind field construction. Six different formulations were considered and the parameters determined by comparing the simulated wind results with in-situ wind measurements. The key factors affecting wave growth and dissipation processes from deep to shallow waters were studied, including wind input, whitecapping, and bottom friction. Comparison with in-situ wave measurements suggested that the KOMEN scheme(wind input exponential growth and whitecapping energy dissipation) and the JONSWAP scheme(dissipation of bottom friction) resulted in good reproduction of the significant wave height of typhoon waves. A preliminary analysis of the wave characteristics in terms of wind-sea and swell wave revealed that swell waves dominated with the distance of R to the eye of the typhoon, while wind-sea prevailed in the outer region up to six to eight times the R values despite a clear misalignment between wind and waves. The results support the hypothesis that nonlinear wave-wave interactions may play a key role in the formation of wave characteristics. 相似文献
2.
Based on the ultra-shallow water storm surge theory proposed by Qin and Feng[1] (1975), an ultra-shallow water storm surge model, taking into consideration the effect of the earth's rotation and the quadratically
depth-varying eddy viscosity, is developed. Using the model wind stress fields as a guide for representing the effect of wind
stress forcing in our model, a numerical investigation of the Bohai Sea wind surge is made. As a better means for solving
the mathematical model, the Galerkin finite element technique is employed in numerical solutions. Under the control of the
main weather situation, namely, the cold wave combined with the extratropical cyclone, two storm surge processes experienced
on the Bohai Sea are simulated numerically. It is found that the experimental results, in the main, are in agreement with
the observations. 相似文献
3.
A laboratory experiment was conducted inside a wind wave tank to investigate the wave induced turbulence. In this experiment, the wave surface elevation and velocity beneath the water surface were measured simultaneously to investigate the relation between the wave status and wave induced turbulence. The profile of the turbulent dissipation rate and Reynolds stress were calculated using experimental data. The effect of the wave status on turbulence is investigated with regard to the wind wave, swell, and mixed wave conditions. It was depicted that the turbulence decreased with increasing depth from the water surface and that the turbulence that was induced by a wave with larger wavelength and wave height is much stronger for the same wave status. Finally, we observed that the wind wave is more effective in activating the wave induced turbulence. 相似文献
4.
Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works. 相似文献
5.
《山地科学学报》2021,(8)
The quadratic rheology model considers the yield stress, viscous stress, turbulent stress and disperse stress, so it is used in this study to derive the velocity profile of debris flows. The quadratic model with the parabolic eddy viscosity was numerically solved, and an analytical solution was derived for the quadratic model with a constant eddy viscosity. These two solutions were compared with the Arai-Takahashi model that excluded the viscous stress and the yield stress. The three models were tested by using 17 experiment cases of debris flows over rigid beds. The results prove that the quadratic model with parabolic and constant eddy viscosities is applicable to muddy and granular flows, whereas the Arai-Takahashi model tends to overestimate the flow velocity near the water surface if a plug-like layer exists. In addition, the von Karman constant and the zero-velocity elevation in the three models are related to sediment concentration. The von Karman constant decreases first and then increases as the sediment concentration increases. The zero-velocity elevation is below the bed surface, likely due to the invalidity of the non-slip boundary condition for the debris flows over fixed beds. 相似文献
6.
Role of Ekman transport versus Ekman pumping in driving summer upwelling in the South China Sea 总被引：3，自引：0，他引：3
Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea (SCS) are examined using QuikSCAT scatterometer wind data. The major upwelling regions in the SCS are the coastal regions east and southeast of Vietnam (UESEV), east and southeast of Hainan Island (UESEH), and southeast of Guangdong province (USEG). It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems. In UESEV, Ekman pumping and Ekman transport are equally important in generating upwelling. The Ekman transport increases linearly from 0.49 Sv in May to 1.23 Sv in August, while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period. In UESEH, the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv, respectively, indicating that 33% of the total wind-driven upwelling is due to Ekman pumping. In USEG, the mean Ekman transport is 0.041 Sv with the peak occurring in July, while Ekman pumping is much smaller (0.003 on average), indicating that the upwelling in this area is primarily driven by Ekman transport. In the summers of 2003 and 2007 following El Niño-Southern Oscillation (ENSO) events, both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon. During the same events, however, Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG. 相似文献
7.
In this study, a 3D idealized model of tidal flow, in which the tidal elevation and velocities are solved analytically, is developed. The horizontal eddy viscosity is neglected, and the vertical eddy viscosity used in the study is assumed to be independent of time and only varies as a parabolic function in the vertical direction. The analytical solution is obtained in a narrow rectangular bay, with the topography varying only across the bay. The model results are compared with the field observations in the Xiangshan Bay. The results show that the influence of varying vertical eddy viscosity mainly has two aspects. On one hand, it amplifies the magnitude of the tidal elevation, particularly the amplitude near the head of the bay. On the other hand, it adjusts the axial velocity profile, resulting in an obvious frictional effect. Furthermore, the tidal elevation and velocities are more sensitive to the magnitude of the eddy viscosity near the bottom than the structure in the upper water layer. 相似文献
8.
A VOF-based numerical model for breaking waves in surf zone 总被引：2，自引：0，他引：2
This paper introduces a numerical model for studying the evolution of a periodic wave train, shoaling, and breaking in surf zone. The model can solve the Reynolds averaged Navier-Stokes (RANS) equations for a mean flow, and (he k-s equations for turbulence kinetic energy k and turbulence dissipation rate e. To track a free surface, the volume of fluid (VOF) function, satisfying the advection equation was introduced. In the numerical treatment, third-order upwind difference scheme was applied to the convection terms of the RANS equations in order to reduce the effect of numerical viscosity. The shoaling and breaking processes of a periodic wave train on gently sloping beaches were modeled. The computed wave heights of a sloping beach and the distribution of breaking wave pressure on a vertical wall were compared with laboratory data. 相似文献
9.
This study investigates the wind energy input, an important source of mechanical energy, in the coastal seas east of China. Using the wind field from the high-resolution sea surface meteorology dataset in the Bohai Sea, Yellow Sea, and East China Sea, we studied the wind energy input through surface ageostrophic currents and surface waves. Using a simple analytical formula for the Ekman Spiral with timedependent wind, the wind energy input through ageostrophic currents was estimated at ～22 GW averaged from 1960 to 2007, and through use of an empirical formula, the wind energy input through surface waves was estimated at ～169 GW. We also examined the seasonal variation and long-term tendency of mechanical energy from wind stress, and found that the wind energy input to the East China Sea decreased before the 1980s, and then subsequently increased, which is contrary to what has been found for the Bohai Sea and Yellow Sea. More complicated physical processes and varying diffusivity need to be taken into account in future studies. 相似文献
10.
We investigated the Stokes drift-driven ocean currents and Stokes drift-induced wind energy input into the upper ocean using a two-way coupled wave-current modeling system that consists of the Princeton Ocean Model generalized coordinate system (POMgcs), Simulating WAves Nearshore (SWAN) wave model, and the Model Coupling Toolkit (MCT). The Coriolis-Stokes forcing (CSF) computed using the wave parameters from SWAN was incorporated with the momentum equation of POMgcs as the core coupling process. Experimental results in an idealized setting show that under the steady state, the scale of the speed of CSF-driven current was 0.001 m/s and the maximum reached 0.02 m/s. The Stokes drift-induced energy rate input into the model ocean was estimated to be 28.5 GW, taking 14% of the direct wind energy rate input. Considering the Stokes drift effects, the total mechanical energy rate input was increased by approximately 14%, which highlights the importance of CSF in modulating the upper ocean circulation. The actual run conducted in Taiwan Adjacent Sea (TAS) shows that: 1) CSF-based wave-current coupling has an impact on ocean surface currents, which is related to the activities of monsoon winds; 2) wave-current coupling plays a significant role in a place where strong eddies present and tends to intensify the eddy’s vorticity; 3) wave-current coupling affects the volume transport of the Taiwan Strait (TS) throughflow in a nontrivial degree, 3.75% on average. 相似文献
11.
《中国海洋大学学报(英文版)》2019,(6)
An improved method for computing the three-dimensional(3 D) first-order Lagrangian residual velocity(uL) is estab-lished. The method computes tidal body force using the harmonic constants of the zeroth-order tidal current. Compared with using the tidal-averaging method to compute the tidal body force, the proposed method filters out the clutter other than the single-frequency tidal input from the open boundary and obtains uL that is more consistent with the analytic solution. Based on the new method, uL is calculated for a wide bay with a longitudinal topography. The strength and pattern of uL are mostly determined by the parts of the tidal body force related to the vertical mixing of the Stokes' drift and the Coriolis effect, with a minor contribution from the advection effect. The geometrical shape of the bay can influence uL through the topographic gradient. The magnitude of uL increases with the increases in tidal energy input and vertical eddy viscosity and decreases in terms of the bottom friction coefficient. 相似文献
12.
《中国海洋湖沼学报》2019,(6)
The effect of the drag coefficient on a typhoon wave model is investigated. Drag coefficients for Pingtan Island are derived from the progress of nine typhoons using COARE 3.0 software. The wind parameters are obtained using the Weather Research and Forecasting model. The simulation of wind agrees well with observations. Typhoon wave fields are then simulated using the third-generation wave model SWAN. The wave model includes exponential and linear growths of the wind input, which determine the wave-growth mode. A triple triangular mesh is adopted with spatial resolution as fine as 100 m nearshore. The SWAN model performs better when using the new drag coefficient rather than the original coefficient. 相似文献
13.
In order to compare and evaluate the performances of the Laplacian viscosity closure, the biharmonic viscosity closure, and the Leith closure momentum schemes in the MPAS-Ocean model, a variety of physical quantities, such as the relative reference potential energy(RPE) change, the RPE time change rate(RPETCR), the grid Reynolds number, the root mean square(RMS) of kinetic energy, and the spectra of kinetic energy and enstrophy, are calculated on the basis of results of a 3D baroclinic periodic channel. Results indicate that: 1) The RPETCR demonstrates a saturation phenomenon in baroclinic eddy tests. The critical grid Reynolds number corresponding to RPETCR saturation differs between the three closures: the largest value is in the biharmonic viscosity closure, followed by that in the Laplacian viscosity closure, and that in the Leith closure is the smallest. 2) All three closures can effectively suppress spurious dianeutral mixing by reducing the grid Reynolds number under sub-saturation conditions of the RPETCR, but they can also damage certain physical processes. Generally, the damage to the rotation process is greater than that to the advection process. 3) The dissipation in the biharmonic viscosity closure is strongly dependent on scales. Most dissipation concentrates on small scales, and the energy of small-scale eddies is often transferred to large-scale kinetic energy. The viscous dissipation in the Laplacian viscosity closure is the strongest on various scales, followed by that in the Leith closure. Note that part of the small-scale kinetic energy is also transferred to large-scale kinetic energy in the Leith closure. 4) The characteristic length scale L and the dimensionless parameter Г in the Leith closure are inherently coupled. The RPETCR is inversely proportional to the product of Г and L. When the product of Г and L is constant, both the simulated RPETCR and the inhibition of spurious dianeutral mixing are the same in all tests using the Leith closure. The dissipative scale in the Leith closure depends on the parameter L, and the dissipative intensity depends on the parameter Г. 5) Although optimal results may not be achieved by using the optimal parameters obtained from the 2D barotropic model in the 3D baroclinic simulation, the total energies are dissipative in all three closures. Dissipation is the strongest in the biharmonic viscosity closure, followed by that in the Leith closure, and that in the Laplacian viscosity closure is the weakest. Mesoscale eddies develop the fastest in the biharmonic viscosity closure after the baroclinic adjustment process finishes, and the kinetic energy reaches its maximum, which is attributed to the smallest dissipation of enstrophy in the biharmonic viscosity closure. Mesoscale eddies develop the slowest, and the kinetic energy peak value is the smallest in the Laplacian viscosity closure. Results in the Leith closure are between that in the biharmonic viscosity closure and the Laplacian viscosity closure. 相似文献
14.
A non-hydrostatic, Boussinesq, and three-dimensional large eddy simulation(LES) model was used to study the impact of the Earth's rotation on turbulence and the redistribution of energy in turbulence kinetic energy(TKE) budget. A set of numerical simulations was conducted,(1) with and without rotation,(2) at different latitudes(10°N, 30°N, 45°N, 60°N, and 80°N),(3) with wave breaking and with Langmuir circulation, and(4) under different wind speeds(5, 10, 20, and 30 m/s). The results show that eddy viscosity decreases when rotation is included, indicating that rotation weakens the turbulence strength. The TKE budget become tight with rotation and the effects of rotation grow with latitude. However, rotation become less important under Langmuir circulation since the transport term is strong in the vertical direction. Finally, simulations were conducted based on field data from the Boundary Layer and Air-Sea Transfer Low Wind(CBLAST-Low) experiment. The results, although more complex, are consistent with the results obtained from earlier simulations using ideal numerical conditions. 相似文献
15.
Different advection schemes and two-equation turbulence closure models based on eddy viscosity concept are used to compute the drag coefficient around a circular cylinder at high Reynolds number (106).The numerical results from these simulations are compared with each other and with experimental data in order to evaluate the performance of different combinations of advection scheme and two-equation turbulence model.The separate contributions from form drag and friction drag are also ana-lyzed.The computatio... 相似文献
16.
楼菁 《中国海洋湖沼学报》1994,12(4):361-371
A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry,taking into account the combined effects of refraction,diffraction and dissipation due to wavebreaking is presented.Wave breaking is simulated by modifying the wave height probability density func-tion and the wave energy dissipation mechanism is parameterized according to that of the hydraulic jumpformulation.Solutions of the wave height,phase function,and the wave direction at every grid point areobtained by finite difference approximation of the governing equations,using Gauss-Seidel Iterative Method(GSIM)row by row.Its computational convenience allows it to be applied to large coast regions tostudy the wave transformation problem.Several case studies have been made and the results compare verywell with the experiment data and other model solutions.The capability and utility of the model forreal coast areas are illustrated by application to a shallow bay of northeast Australia. 相似文献
17.
Absolute geostrophic currents in the North Pacific Ocean are calculated using the P-vector method and gridded Argo profiling data from January 2004 to December 2012. Three-dimensional structures and seasonal variability of meridional heat transport (MHT) and meridional salt transport (MST) are analyzed. The results show that geostrophic and Ekman components are generally opposite in sign, with the southward geostrophic component dominating in the subtropics and the northward Ekman component dominating in the tropics. In combination with the net surface heat flux and the MST through the Bering Strait, the MHT and MST of the western boundary currents (WBCs) are estimated for the first time. The results suggest that the WBCs are of great importance in maintaining the heat and salt balance of the North Pacific. The total interior MHT and MST in the tropics show nearly the same seasonal variability as that of the Ekman components, consistent with the variability of zonal wind stress. The geostrophic MHT in the tropics is mainly concentrated in the upper layers, while MST with large amplitude and annual variation can extend much deeper. This suggests that shallow processes dominate MHT in the North Pacific, while MST can be affected by deep ocean circulation. In the extratropical ocean, both MHT and MST are weak. However, there is relatively large and irregular seasonal variability of geostrophic MST, suggesting the importance of the geostrophic circulation in the MST of that area. 相似文献
18.
介绍解五维波动问题的微分算子级数法，首先引进数性算子概念及微分算子级数法；其次．推导出了求解公式；最后通过求解公式求解了一些五维波动方程的例题，得出任何维数（n≥5）的波动方程柯西问题都可以用微分算子级数法求其解。 相似文献
19.
NUMERICAL STUDY ON THE TIDAL FRONT IN THE WESTERN YELLOW SEA 总被引：1，自引：0，他引：1
The formation and evolution of the tidal front in the western Yellow Sea are studied by means of a two-dimensional model in which wind and tide mixing, sun radiation and wind stress, and realistic topography are incorporated. In this numerical study, the schemes employed are stable for time step t= 900 s, so the model can be run for 4 months to simulate the front evolution. The authors examined the effects of mixing and atmospheric forcing on the tidal front under conditions of : mixing and solar heating without wind stress on the sea surface; mixing, solar heating and 50 hours of wind stress; mixing, solar heating and long time periodical wind stress, Results show that (1) the tidal front forms at the beginning of May, and strengthens with the increasing of heat input, (2) the temperature structure in the shallow well-mixed water is dominated by mixing, while in the front and deeper stratified regions, it is controlled by the joint effects of (mainly) mixing and advection, 0) the currents and front all 相似文献
20.
介绍解五维波动问题的微分算子级数法,首先引进数性算子概念及微分算子级数法;其次,推导出了求解公式;最后通过求解公式求解了一些五维波动方程的例题,得出任何维数(n≥5)的波动方程柯西问题都可以用微分算子级数法求其解。 相似文献