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1.
近岸浅海潮流数值模型及其应用 总被引：2，自引：0，他引：2
在Ｃａｓｕｌｌｉ提出的半隐式有限差分方法的基础上,通过改进底摩擦力公式以避免在超浅水域底摩擦项过大的缺点,对底摩擦项进行线性化处理以获得隐式效果,对平流项采用适当的差分格式以减小假扩散及对活动边界误差的传播,采用高效的迭代格式提高运算速度,建立适合于近岸浅海的潮流数值模型。该模型有良好的稳定性,计算时间步长不受ＣＦＬ条件的限制,在防城港的潮流模拟中,模型的验证结果良好。 相似文献
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具有潮滩移动边界的浅海环流有限元模型 总被引：3，自引：3，他引：3
本文基于二维化浅水动力学方程组,运用伽辽金加权余量法导出计算浅水环流的有限元公式.对计算区域采用三角单元剖分,用线性插值函数逼近流速及水位,使用集中质量法以代替求解大型代数方程组的过程.通过建立陆水边界位置与瞬时水位的相关关系,解决了陆水边界线移动的数学处理问题.对于运动方程中的底摩擦项和科氏力项采用隐式格式,从而改善了模型的数值稳定性.对皮口沿岸潮流场的数值分析,较好地再现了该海区的实际流况,从而证明了本文所建立的环流模型具有良好的重现性.皮口港扩建工程流场预测应用实例说明了本模型可以用来解决小尺度潮滩海区的流场预测问题,在海洋开发活动中具有广泛的应用前景. 相似文献
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显式完全平方守恒差分格式在近岸海流数值模拟中的应用 总被引：2，自引：0，他引：2
用显式完全平方守恒差分格式及其改进分解算法对南海月平均流和海面起伏进行了数值模拟，与隐式完全平方守恒差分格式相比，计算时间可省３－５倍，具有良好的时间效益，而且，其计算效果不比稳式完全平方守恒差分格式差。因此，显式完全平方守恒差分格式及其改进分解算法具有良好的实用价值。 相似文献
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基于POM模式,以西北太平洋海域为试验海区,针对Nudging松弛项的差分方案及Nudging松弛系数进行了数值试验。结果表明,通过引入Nudging松弛项的潮波模拟结果明显优于未加Nudging松弛项的模拟结果;在松弛系数取值相等情况下,Nudging松弛项采用隐式差分方案的结果要优于采用显式差分方案的结果;Nudging松弛项差分方案不论是显式还是隐式,模拟结果的偏差都随着松弛系数的增加而逐渐减小,当松弛系数增加到最优值后,模拟结果的偏差将随着松弛系数的增加而加大;Nudging松弛项差分方案为显式时,松弛系数太大将导致模式溢出;而Nudging松弛项差分方案为隐式时,能够有效增大松弛系数的阈值。文中还给出了最优Nudging同化方案下西北太平洋海域M2分潮的同潮图。 相似文献
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通过三维模式导出二维数值模式,采用守恒型空间差分格式对渤海风暴潮进行数值模拟。同时采用由三维模式导出的任意形式的底摩擦表达式,找出适用于渤海风暴潮的底摩擦参数。对曾经发生在渤海的四次较严重的风暴潮进行数值后报并与实测资料相比较,证实预报模式的可行性。 相似文献
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分别采用模式气压场及模式台风场计算气压分布及风速分布,采用地形拟合的sigma坐标水动力方程组及紊流方程建立了潮流、风暴潮耦合模型。三维水动力方程组通过分裂算子法与Casulli半隐式差分格式直接求解。在珠江口的极值流速计算中,先进行了南海北部的潮流、风暴潮耦合模拟,模拟水位与实测值符合较好。以六区域模拟结果为边界,采用嵌套网格方法,在珠江口进行了高分辨率的潮流、风暴潮耦合模拟。选用1968～1999年共65个影响工程区域的台风过程,计算出珠江口的海域年极值流速序列,分析了该海域多年一遇的极值流速分布。 相似文献
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利用实测资料分析重构了大亚湾和大鹏湾潮汐水位“双峰”现象,确定了浅水分潮的异常增长是潮位“双峰”现象的主要成因,其中四分之一日分潮和六分之一日分潮起着至关重要的作用。通过SCHISM模型构建大亚湾和大鹏湾附近海域高分辨率水动力模型,模拟结果表明近岸海域,在大亚湾以东,潮汐类型为不规则全日潮,以西为不规则半日潮,在两个海湾内均为不规则半日潮;研究海域的潮流均表现为不规则半日潮流。四分之一日分潮和六分之一日分潮在大亚湾和大鹏湾的不同变形过程是造成两个相邻海湾水文差异的直接原因。通过构建不同底摩擦强度、消除水底地形以及改变海湾水深的数值实验研究表明,分潮传播方向与水深变浅方向是否一致,是导致两个海湾潮波浅水变形不同的根本原因。 相似文献
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Parabolic Approximation of the Weakly Nonlinear Mild Slope Equation with Bottom Friction 总被引：2，自引：0，他引：2
This paper presents a refined parabolic approximation model of the mild slope equation to simu-late the combination of water wave refraction and diffraction in the large coastal region.The bottom frictionand weakly nonlinear term are included in the model.The difference equation is established with the Crank-Nicolson scheme.The numerical test shows that some numerical prediction results will be inaccurate in com-plicated topography without considering weak nonlinearity;the bottom friction will make wave height damp-ing and it can not be neglected for calculation of wave field in large areas. 相似文献
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Young Ho Seung 《Journal of Oceanography》2003,59(1):113-118
A simple analytical model is considered for the dynamics of volume transport of the Tsushima Current. This model is basically
baroclinic but allows bottom friction over the shallow regions connecting the Pacific Ocean to the Japan Sea basin, and is
thus different from previous models which are either purely barotropic with bottom friction predominating over the whole domain,
or purely baroclinic with bottom friction completely ignored. Compared to the previous barotropic model, this model is not
only more realistic but also gives much simpler results. It gives the observed downstream sea level slope, which is not seen
in the previous baroclinic model. As a result, the estimated transport of the Tsushima Current is closer to the observational
data than those of previous models. This model indicates that the localized bottom friction acting over the shallow regions
not only controls the transport of the Tsushima Current but also moves the stagnation point of the western boundary current
northward.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
We investigated the sea level response of the Japan Sea to changes in atmospheric pressure using barotropic shallow water
models driven by idealized synoptic pressure forcing. The regional response lags behind the synoptic pressure forcing because
the adjustment is slowly established by water exchange through narrow, shallow straits. The sea level response of the realistic
Japan Sea to the idealized forcing varies with geographical location and shows zonally asymmetric variations in amplitude
and phase. The simulated response is in good agreement with the observed response of sea level recorded at Japanese coastal
tide gauges. The results of a simple one-dimensional model indicate that the zonally asymmetric pattern, with an eastward-propagating
pressure system, is essentially caused by bottom friction in shallow straits. This asymmetry arises if the typical wavelength
of the synoptic pressure system is slightly larger than the spatial scale of the Japan Sea. 相似文献
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铁山港海湾是一个遭受风暴潮灾害影响较为严重的半封闭型海湾,基于有限元海洋数学模型ADCIRC (Advanced Circulation Model)研究了1409号"威马逊"台风期间铁山港海湾的风暴潮特征及非线性作用。结果表明:当考虑天文潮与风暴潮之间的相互作用时,风暴潮水位的计算结果更加准确,只考虑纯台风影响时,计算结果会低估风暴潮增水值,高估减水值,对预报结果造成较大的误差。海湾内部的增水要远大于湾外,但是减水值则相差不大。通过对天文潮和风暴潮非线性作用的影响因子进行分析,风应力的浅水效应可以忽略,但底摩擦项和对流项影响较大。在海湾内部对流项占主导地位,与天文潮的耦合作用也较强;而在湾外,底摩擦项占优势,耦合作用在海湾内外都较强。天文潮与风暴潮相互作用产生的非线性水位在湾顶处最大可达0.94 m,出现在风暴潮最大减水时刻,风暴潮增水发生后有所减弱,非线性水位表现出从湾外向湾内递增的规律。 相似文献
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This study investigates the effectiveness of a revised whitecapping source term in the spectral wind wave model SWAN (Simulating WAves Nearshore) that is local in frequency space, nonlinear with respect to the variance density and weakly dependent on the wave age. It is investigated whether this alternative whitecapping expression is able to correct the tendency towards underprediction of period measures that has been identified in the default SWAN model. This whitecapping expression is combined with an alternative wind input source term that is more accurate for young waves than the default expression. The shallow water source terms of bottom friction, depth-induced breaking and triad interaction are left unaltered. It is demonstrated that this alternative source term combination yields improved agreement with fetch- and depth-limited growth curves. Moreover, it is shown, by means of a field case over a shelf sea, that the investigated model corrects the erroneous overprediction of wind-sea energy displayed by the default model under combined swell-sea conditions. For a selection of field cases recorded at two shallow lakes, the investigated model generally improves the agreement with observed spectra and integral parameters. The improvement is most notable in the prediction of period measures. 相似文献
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海洋飞沫方案改进对台风“威马逊”强度预报的影响 总被引：1，自引：0，他引：1
本文采用分粒径段组合方式改进海气耦合模式海洋飞沫方案,并利用耦合模式对1409号台风"威马逊"进行数值模拟,分析了海洋飞沫方案改进对台风结构、强度以及海气动量通量、热量通量模拟结果的影响。结果显示,耦合模式中海洋飞沫方案可通过改变海表面粗糙度影响海气动量与热量通量;海洋飞沫还可以通过沫滴向大气输送感热和水汽而直接影响海气热通量,进一步影响台风的强度。模拟结果显示改进后海洋飞沫方案的台风强度更接近观测。改进海洋飞沫方案后粗糙度的计算结果小于原始方案,相应地海气热通量以及下垫面耗散作用也弱于后者,海表面风场是海气热交换与下垫面耗散共同作用的结果。 相似文献
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Analysis of a craft with two degrees of freedom (2DOF) consumes time more than simulation of a craft with a fixed trim condition; therefore in most of the previous researches fixed trim condition is taken into account to analyze the flow field around a craft in shallow water and head sea wave conditions. In this paper numerical simulation of Reynolds Average Naiver Stokes (RANS) equations are used to analyze the motion of DTMB 62 model 4667-1 planing vessel in calm water and head sea waves in both deep and shallow water with two degrees of freedom (heave and pitch). For this purpose, a finite volume ANSYS-FLUENT code is used to solve the Navier-Stokes equations for the simulation of the flow field around the vessel. In addition, an explicit VOF scheme and SST k-ω model is used with dynamic mesh scheme to capture the interface of a two-phase flow and to model the turbulence respectively in the 2DOF model.Regarding the results, reducing the wavelength and also the depth of the water can increase the drag force. Also comparing the results of a fixed trim vessel with the results of a free to sink and trim one in calm water shows a difference of approximately 50% in the drag force in shallow water. 相似文献
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A depth-integrated model for weakly dispersive, turbulent, and rotational fluid flows 总被引：2，自引：0，他引：2
A set of weakly dispersive Boussinesq-type equations, derived to include viscosity and vorticity terms in a physically consistent manner, is presented in conservative form. The model includes the approximate effects of bottom-induced turbulence, in a depth-integrated sense, as a second-order correction. Associated with this turbulence, vertical and horizontal rotational effects are captured. While the turbulence and horizontal vorticity models are simplified, a model with known physical limitations has been derived that includes the quadratic bottom friction term commonly added in an ad hoc manner to the inviscid equations. An interesting result of this derivation is that one should take care when adding such ad hoc models; it is clear from this exercise that (1) it is not necessary to do so – the terms can be included through a consistent derivation from the viscous primitive equations – and (2) one cannot properly add the quadratic bottom friction term without also adding a number of additional terms in the integrated governing equations. To solve these equations numerically, a highly accurate and stable model is developed. The numerical method uses a fourth-order MUSCL-TVD scheme to solve the leading order (shallow water) terms. For the dispersive terms, a cell averaged finite volume method is implemented. To verify the derived equations and the numerical model, four cases of verifications are given. First, solitary wave propagation is examined as a basic, yet fundamental, test of the models ability to predict dispersive and nonlinear wave propagation with minimal numerical error. Vertical velocity distributions of spatially uniform flows are compared with existing theory to investigate the effects of the newly included horizontal vorticity terms. Other test cases include comparisons with experiments that generate strong vorticity by the change of bottom bathymetry as well as by tidal jets through inlet structures. Very reasonable agreements are observed for the four cases, and the results provide some information as to the importance of dispersion and horizontal vorticity. 相似文献