【作者】 吴相忠；

【导师】 张庆河；

【作者基本信息】 天津大学 ， 港口、海岸及近海工程， 2010， 博士

【摘要】 在海岸地区,准确预测近岸地区的水流运动对于泥沙输运、海岸演变与环境等问题的研究具有重要意义,而近岸水流的运动受到各种因素的影响,特别是波浪动力较强时,合理预测近岸水流运动必须准确描述波浪的作用。以往研究大多数是在对波浪的影响,例如波浪辐射应力、波浪破碎产生的表面应力和波流共同作用下的底部切应力等做出许多简化假设或者在未能全面考虑这些影响因素的条件下得到的。因此,在合理、全面地考虑波浪影响的基础上建立三维近岸水流模型,并对波浪作用下的近岸流场进行研究,在学术上和工程应用上均有重要意义。本文首先基于二阶斯托克斯波和二阶椭圆余弦波理论推导了非线性波辐射应力垂向分布,并讨论了其分布规律;其次引入ELCIRC三维水流模型和REFDIF波浪模型,将包含非线性波辐射应力垂向分布、波浪破碎水滚应力、波流共同作用下的床面摩阻引入到三维水流模型中,建立了可以描述复杂近岸波生流系统的近岸三维水动力模型,并利用已有波浪增减水、近底回流和沿岸流实验数据对该模型进行了验证。基于上述近岸三维水动力模型,本文分别详细研究了近岸流中的沿岸流与裂流现象。沿岸流现象数值模拟研究结果表明波浪作用下沿岸流的分布受到入射波高、入射角度和岸滩地形坡度的影响并呈现如下分布规律:随着波浪入射波高的增大,沿岸流的速度和影响范围也越大;当波浪入射角度达到45°时,沿岸流的速度达到最大值;缓坡上沿岸流普遍大于陡坡上沿岸流的影响范围,陡坡地形上的沿岸流分布比较集中。裂流现象计算结果表明波浪作用下裂流的分布受到入射波高、入射角度和驼峰高度的影响并呈现如下分布规律:随着入射波高的增大,裂流的存在范围越大,速度也相应增大;在正弦地形上波浪斜向入射时会产生沿岸流和近岸环流。正弦地形的振幅越大,即驼峰高度越大,在裂流沟处产生的裂流速度越大。更多还原

【Abstract】 In coastal area, it is very important to predict nearshore current accurately for investigation of sediment transport, coastal evolution and environmental problems. However, the nearshore current is affected greatly by various factors, e.g., the role of waves must be described reasonablely when the wave is relatively strong. The previous studies on the impact of waves, such as wave radiation stress, the surface stress generated by wave rolling due to wave breaking and the bottom shear stress due to combined waves and current, are mostly obtained by a number of simplifying assumptions or not fully taking into account the avove factors. Thus it is of great significance to develop a three-dimensional nearshore hydrodynamic model on the basis of considering wave impact reasonably and comprehensively, and to investigate the nearshore current field due to waves.Firstly, the expressions for vertical distributions of radiation stresses were dirived based on the second-order Stokes waves and the second-order cnoidal wave theory respectively; and the vertical profiles of radiation stresses are discussed. Secondly, after the introduction of three-dimensional ELCIRC hydrodynamic model and REFDIF wave model, the vertical profile of radiation stresses of non-linear waves, the shear stress of wave roller under wave breaking and the bottom shear stress due to combined waves and current were incoorpated into the ELCIRC model, which leads to a three-dimensional nearshore hydrodynamic model with the function of describing the complex system of wave-induced nearshore current. The newly developd model was verified by the experimental data of wave setup and setdown, undertow and longshore current.Using the three-dimensional nearshore hydrodynamic model metioned above, the longshore current and rip current are studied in detail. The numerical simulation results of longshore current show that the distribution of longshore current is affected by the wave height, wave direction and beach slope. The distribution laws are as follows: the greater the incident wave height is, the greater the longshore current velocity and the influence area are; when the wave incident angle comes to 45 degrees, the longshore current velocity reaches maximum; the influence area of the longshore current on the gentle slope is greater than that on the the steep slope, and the flow distribution is relatively concentrated on the steep terrain. The results of the rip current show that the distribution of rip current flow is affeccted by the incident wave height, incident wave angle and hump height. The distribution laws are as follows: the greater the incident wave height is, the greater of the rip current velocity and the influence range are; On the sinusoidal topography, the oblique incident wave can produce longshore current and nearshore circulation; the greater the amplitude of the sinusoidal topography(hump height) is, the greater the rip current velocity generated at the ditch of the rip current is.更多还原