共查询到19条相似文献，搜索用时 125 毫秒
1.
内孤立波波致流场数值模拟研究 总被引：1，自引：1，他引：0
基于KdV、mKdV理论,利用Fluent计算软件,采用"平板拍击"造波方法,进行内孤立波数值模拟,并与物理实验结果进行对比验证。利用数值模拟结果,分析内孤立波波致流场变化,结果表明:上下层流体中波致水平流速方向相反,均呈现先增加后减小的变化趋势,且波谷经过时刻流速最大;在波谷经过断面处,波致水平流速在上层流体中沿垂向分布无明显变化,在波面以下的下层流体中有衰减趋势,但衰减很小;两层流体界面与波谷之间存在过渡水深范围,水平流速在该水深范围内沿垂向衰减明显,且随内孤立波振幅的增大,过渡水深范围有所增大。 相似文献
2.
将置于大尺度密度分层水槽上下层流体中的两块垂直板反方向平推,以基于MCC理论解的内孤立波诱导上下层流体中的层平均水平速度作为其运动速度,发展了一种振幅可控的双推板内孤立波实验室造波方法,并对内孤立波作用下浮式生产储油系统(FPSO)的载荷特性开展了系列实验。结果表明,无因次内孤立波水平力和力矩幅值均与先导内孤立子无因次振幅之间呈线性关系,其斜率与上下层流体深度比有关;在各种上下层流体深度比下,无因次内孤立波垂向力幅值与先导内孤立子振幅之间近似呈幂函数关系。 相似文献
3.
基于MCC理论的内孤立波数值模拟 总被引：3，自引：0，他引：3
基于MCC(Miyata-Choi-Camassa)理论,将内孤立波诱导上下层深度平均水平速度为入口条件,结合理想流体完全非线性欧拉方程,建立了两层流体中内孤立波生成与传播的CFD(Computational Fluid Dynamics)数值水槽方法。在系列数值模拟基础上,获得了内孤立波设计振幅与数值模拟振幅之间的相关关系,实现了在振幅可控条件下的内孤立波数值模拟。结果表明,在极限振幅范围内,数值模拟所得内孤立波波形均与MCC理论解吻合良好,而KdV(Korteweg-de Vries)和mKdV(modi-fied KdV)理论解只适用于小振幅的情况。同时,利用CFD数值模拟结果,对内孤立波诱导流速场特性进行了分析,结果表明内孤立波诱导水平速度在上层及波面下方流体层中垂向衰减很小,但在内界面与波面之间流体层中垂向衰减明显。 相似文献
4.
内孤立波具有较大的振幅与较强的垂向剪切,能对海洋工程设施产生极大的破坏作用。本文设计实验研究了内孤立波与直立小直径桩柱的相互作用,采用粒子图像速度测量法(PIV)测量内孤立波的流速场,并采用自行设计的测力天平测量桩柱受力,测量分析了内孤立波对小直径直立桩柱产生作用力的实验值,与Morison公式计算的理论值比较。实验结果表明,第一模态内孤立波的流速方向以及作用力在桩柱的上下部分方向相反,产生很强的速度切变和扭力,对小直径直立桩柱造成破坏。通过与Morison公式计算的理论值比较,发现实验值与理论值的大小以及分布规律基本相同。 相似文献
5.
为定量分析内孤立波破碎的混合过程,本文在二维内波水槽中进行了两层流体第一模态内孤立波在斜坡上破碎的实验,运用粒子图像测速技术(PIV)测量内孤立波传播、破碎、反射过程的流场,计算涡度、湍动能和湍耗散率。结果表明不同振幅内波在不同角度斜坡上破碎时各个量的分布特征十分相似,各组实验各要素时间序列中均有两个峰值,分别发生于非线性增强和破碎时刻。得到破碎时湍耗散率与内孤立波振幅的关系为:较小振幅内波的湍耗散率与振幅呈2次关系,无因次振幅增大到0.9湍耗散率趋于不变;与斜坡角度的关系为:对于小振幅内波斜坡角度增大,破碎程度降低,耗散率减小;振幅较大时,存在一个角度使破碎程度最大。破碎引起的湍耗散率的量级在10–7到10–4m2/s3之间,比实测海洋中内孤立波传播界面和内潮遇地形破碎的湍耗散大1个量级。 相似文献
6.
内孤立波具有振幅尺度大、能量集中的特点,其引起流场和密度场的迅速变化可能对海洋工程结构物以及水下潜体造成严重威胁。因此研究不同造波条件下生成的内孤立波运动的流场特征具有重要的学术意义和实际应用价值。采用直接数值模拟方法和给定的初始密度场密度跃迁函数,对重力塌陷激发内孤立波的运动过程进行研究,探讨了不同造波条件下,激发产生的内孤立波波型、涡度、振幅和水平速度等流场特征。结果表明:(1)直接模拟数值方法能够模拟内孤立波传播过程中的密度界面波型反转现象;(2)从定性和定量的角度,证实了不稳定内孤立波传播过程中存在能量的向后传递;(3)对于相同的台阶深度(水闸两侧初始密度界面的高度差),初始涡流保持相同,但是随着上下层水深比的减小,其强度下降显著;(4)台阶深度对初始涡流的垂直结构的影响要大于上下层水深比,且台阶深度对内孤立波的振幅、水平速度的影响显著。 相似文献
7.
为研究内孤立波质量源数值造波方法,本文采用两个点源形式的质量源,分别放置于两层流体的上下层中作为内孤立波激发源。推导源项表达式,从不可压缩流体的Navier-Stokes方程出发,结合内孤立波Kd V、e Kd V理论,基于商业软件FLUENT发展了一种内孤立波质量源数值造波方法。通过数值模拟,分析了质量源造波过程中内孤立波的生成过程,并将数值模拟结果同理论及实验作对比。结果表明:基于此方法生成的内孤立波波形、波高及波致水平速度与理论及实验吻合度较好,该方法是可行的,并且耗时短、效率高。 相似文献
8.
本文通过实验室水槽实验,讨论内孤立波经过凹陷地形的演化过程。实验在两层流体中进行,上下水层的厚度和密度被定量地控制,改变凹陷地形的宽度,并对每种地形分别进行了不同分层结构下具有不同初始振幅的内孤立波对照实验,研究内孤立波与凹陷地形的作用过程。研究发现,本文实验环境下凹型内孤立波实验波形与mKdV(Korteweg-deVries)理论波形更符合;而上凸型内孤立波实验,当非线性参数ε≤0.22时,KdV理论波形与实验波形符合较好,当非线性参数ε≥0.27时.mKdV理论与实验波形符合较好。下凹型内孤立波经凹陷地形过程中波形变化轻微,主波振幅有先减小后增大的趋势,且障碍比越大,变化趋势越明显。本实验结果可作为研究海洋中内孤立波与海底凹陷地形作用情况的参考。 相似文献
9.
根据南海北部陆坡海域潜标观测数据,对该海域第二模态内孤立波统计特征进行分析。观测期间共发现72个第二模态内孤立波,包含101 个第二模态内孤立波孤立子。该海域第二模态内孤立波以凸型为主,且最大振幅多为下凹振幅,占79.2%。KdV 方程波速计算结果表明,波速可用三角函数描述,整体表现为夏季大、冬季小,且第二模态内孤立波流速呈明显的三层结构。最大流速深度及人工判别得到的上下层转向深度的统计结果表明:上层内波流流速转向平均深度约为97.7m,中层内波流最大流速深度约为134.6m,下层内波流转向平均深度约为204.2m,内波流最大流速多发生在中层,流向主要为西北向,流速主要分布于0.2~0.8 m·s-1 区间范围内,占82.2%;上层流向主要为东南向,流速主要分布于0~0.6m·s-1区间范围内,占98.0%;中层流向主要为西北向,流
速主要分布于0.2~0.8m·s-1区间范围内,占93.1%;下层流向主要为东南向,流速主要分布于0~0.4m·s-1区间范围内,占94.1%。本文系统性地给出了南海北部陆坡海域第二模态内孤立波统计特征,可为相关研究、水下航行及工程应用提供重要的资料和参考。 相似文献
10.
利用垂向连续分层变系数EKdV模型,模拟了南海北部海域大振幅内孤立波的传播和裂变过程,并与观测数据进行比较。结果表明:连续分层变系数EKdV模型能够较好地反映振幅小于100m的内孤立波的振幅和波宽,对于更大振幅的强非线性内波,该模型模拟的振幅和波宽均较实测较小;非线性模态函数能够较准确地反映温度振荡的垂直结构,而水平流速的大小和垂直结构则与线性模态较符合。研究结果表明,变系数EKdV模型能够为研究和理解大振幅内孤立波的传播和裂变过程提供较好的理论支持。 相似文献
11.
An internal gravity wave model was employed to simulate the generation of internal solitary waves(ISWs) over a sill by tidal flows. A westward shoaling pycnocline parameterization scheme derived from a three-parameter model was adopted, and then 14 numerical experiments were designed to investigate the influence of the pycnocline thickness, density difference across the pycnocline, westward shoaling isopycnal slope angle and pycnocline depth on the ISWs. When the pycnocline thickness on both sides of the sill increases, the total barotropic kinetic energy, total baroclinic energy and ratio of baroclinic kinetic energy(KE) to available potential energy(APE) decrease, whilst the depth of isopycnal undergoing maximum displacement and ratio of baroclinic energy to barotropic energy increase. When the density difference on both sides of the sill decreases synchronously, the total barotropic kinetic energy, ratio of baroclinic energy to barotropic energy and total baroclinic energy decrease, whilst the depth of isopycnal undergoing maximum displacement increases. When the westward shoaling isopycnal slope angle increases, the total baroclinic energy increases whilst the depth of turning point almost remains unchanged. When the depth of westward shoaling pycnocline on both sides of the sill reduces, the ratio of baroclinic energy to barotropic energy and total baroclinic energy decrease, whilst the total barotropic kinetic energy and ratio of KE to APE increase. When one of the above four different influencing factors was increased by 10% while the other factors keep unchanged, the amplitude of the leading soliton in ISW Packet A was decreased by 2.80%, 7.47%, 3.21% and 6.42% respectively. The density difference across the pycnocline and the pycnocline depth are the two most important factors in affecting the characteristics and energetics of ISWs. 相似文献
12.
Laboratory experiments are performed in a large stratified fluid flume to examine the characteristics of the load on a submerged slender body that is exerted by a nonstationary internal solitary wave (ISW) from its interaction with a gentle slope. The nonstationary ISW over the slope and its load on the body are measured by using multi-channel conductivity-probe arrays and a specially designed force measurement device, respectively, and the body’s vertical and horizontal positions on the load are determined by analyzing the effects of the incident ISW’s amplitude. The experimental results show that the load on the slender body increases as the incident ISW’s amplitude increases; additionally, the effect of oscillations is enhanced because of the ISW’s distortion, breaking and fission. The oscillating action from fission waves becomes dominant as the amplitude reaches a certain value. Additionally, the load is correlated with body’s vertical position relative to the pycnocline. The magnitudes of the vertical and horizontal forces reach a maximum and minimum in the pycnocline, respectively, and the horizontal force in this direction is the opposite above and below the pycnocline. Compared to a case without a slope, the load on the slender body increases because of the nonstationary ISW, and its effect on the maximum force is transferred to the pycnocline. When the body’s horizontal position is located close to the top of the slope, the direction of the horizontal and vertical forces remains consistent, but its acting time becomes longer. In addition, high-frequency actions on the slender body are impacted by nonstationary ISWs near the slope’s top. 相似文献
13.
内孤立波浅化破碎过程斜坡沉积物孔压响应特征实验分析 总被引：2，自引：2，他引：0
观测资料显示内孤立波沿斜坡浅化过程对海底沉积物的作用犹如一台水中吸尘器，在破碎转换阶段达到最强，甚至会触发一系列地质活动，引发地质灾害。为界定此过程中沉积物的动力响应特征和影响因素，在大型重力式分层流水槽中模拟不同振幅内孤立波和不同类型沉积物斜坡连续作用过程，利用孔隙水压力采集系统实时记录孔隙水压力变化，对比分析不同水动力、坡度、沉积物类型情况下沉积物中超孔压变化特征。分析结果表明，内孤立波破碎过程，破波位置海床表层波压力和不同深度超孔隙水压力都存在相似的"U"型负压力变化过程；破碎波经过位置沉积物表现为和表面波压力正相关的孔压响应特征。破碎点沉积物中超孔压幅值随深度减小，约在6%波长深度位置减少到坡面压力的50%。超孔压幅值和内孤立波振幅、沉积物类型和斜坡度密切相关，坡度由0.071变化到0.160时，波压力幅值可增大至1.6倍。内孤立波振幅变化不影响不同类型海床土动力响应规律，只与超孔隙水压力值大小有关，内孤立波对海床的动力作用可认为弹性作用。 相似文献
14.
Chen Liang Xiong Xuejun Zheng Quanan Yuan Yeli Yu Long Guo Yanliang Yang Guangbing Ju Xi Sun Ji Hui Zhenli 《海洋学报(英文版)》2020,39(11):44-51
The mode-2 internal solitary waves (ISWs) generated by mode-2 internal tide (IT) are identified by mooring observations in the northern South China Sea (SCS) from 2016 to 2017. Two mode-2 ISWs with a re-appearance period of 24.9 h observed on 29 and 30 July 2016 are characterized by type-b ISWs. They occurred when the isotherms compressed obviously in the vertical direction. Modal decomposition of IT horizontal currents shows that the vertical compression of the isotherms is mainly caused by diurnal mode-2 IT. The analysis of the role of the density stratification reveals that a deeper and thinner pycnocline is favorable for generation of mode-2 ISWs rather than pycnocline intensity. By comparing the mode-2 nonlinear, dispersion coefficients and the Ursell numbers calculated based on the stratification associated with different kinds of ITs with the observation results, it is shown that the diurnal mode-2 IT plays a crucial role in the generation of the mode-2 ISWs. When the diurnal mode-2 IT interacts with the semidiurnal IT and causes a deeper and thinner pycnocline, the mode-2 ISWs are easily excited. 相似文献
15.
为研究孤立波作用下结构物周围流场特征,基于无网格SPH方法,建立孤立波与海洋结构物相互作用模型,对不同波幅孤立波作用下部分淹没矩形结构物周围波面、流速、涡量及结构受力特征进行计算分析,探索了相对波高对非淹没结构物周围流场的影响规律。结果表明:流场特征与相对波高密切相关,相对波高较小时,波面、流速、涡量及结构荷载均较为光滑,相对波高在0.2以上时,波峰爬升至结构物顶部并在越过结构物后与水槽内水体碰撞造成流场波动,波面、流速、涡量及结构荷载的波动幅度随着相对波高增大而增大,流场更加复杂,结构物水平和垂向负压也越大,且结构物周围涡分布逐渐向深度方向和下游方向发展。 相似文献
16.
内波破碎引起的能量耗散和混合是海洋内部的重要物理过程。通过在二维内波水槽进行实验室实验,分析内波与地形的作用,探究内孤立波与平顶海山地形作用时波要素、能量以及湍耗散率的时空变化。本实验利用重力塌陷法在两层流体中制造第一模态内孤立波,通过粒子图像测速技术(particle image velocimetry, PIV)获得内孤立波与地形作用时的流场结构,定量分析整个作用过程。结果表明,地形会改变波形甚至引起破碎,内波与地形作用时,振幅和能量密度会在内孤立波爬坡时迅速增大,在地形前缘产生强烈能量耗散。入射波的能量与塌陷高度呈二次函数关系,透射波能量随地形升高减小,反射波能量随地形升高增大。地形前缘局地湍耗散率极值时间序列在部分实验中呈双峰结构,对应内孤立波界面处剪切加强引起湍流耗散和波后缘翻转破碎。破碎引起的地形前缘区域平均湍耗散率量级在10~(-5)m~2/s~3,局地湍耗散率极值与入射波振幅呈指数关系,所有实验中局地湍耗散率的最大值接近10~(-3) m~2/s~3量级。 相似文献
17.
《Coastal Engineering》2001,44(2):65-77
Understanding of fluid flows and sediment transport in the foreshore has been severely hampered by the difficulty of obtaining swash flow velocity measurements in this dynamic and extremely shallow region. We present a digital imaging method, known as particle image velocimetry (PIV), to quantify the horizontal flow structure of swash. This technique exploits similar patterns of image intensity in multiple images sampled sequentially to identify spatial offsets corresponding with maximum correlations between image subregions. These offsets are used in conjunction with the sampling interval to derive velocity vectors describing the horizontal flow structure. Pre-processing methods to geo-rectify oblique imagery to a planar surface and post-processing methods of correcting spurious vectors are described. The PIV method overcomes many of the limitations of in situ sampling of swash flows and is shown consistent with results from a previously tested remote sensing technique for measuring swash edge velocities. In general, this technique provides a unique capability for spatially extensive and well-resolved quantification of swash flows. 相似文献
18.
内孤立波是发生在密度稳定层化海水中的一种特殊的海洋内波。预测内孤立波传播难度较大。本文提出了一种方法,利用美国麻省理工学院大气环流模型（MITgcm）的内孤立波模型计算了大量模拟数据,建立数据库。采用机器学习的方法,建立一个基于支持向量机（support vector machine,SVM）的安达曼海南部内孤立波传播预测模型。最后运用安达曼海南部的Sentinel-1A合成孔径雷达（SAR）图像对内孤立波传播预测模型结果进行检验。结果表明：基于SVM的内孤立波传播时间预测模型预测的时间平均绝对百分比误差为8.43%,平均绝对误差为1.00 h。基于SVM的内孤立波到达位置预测模型预测的位置平均绝对百分比误差为0.071%,平均绝对误差为0.069°。基于SVM的内孤立波振幅预测模型预测的振幅范围为23.80~84.98 m。 相似文献
19.
In this paper, by non-dimensional analysis, it is found that finite-depth theory is more appropriate to the study of internal solitary waves (ISWs) in the South China Sea (SCS) than shallow-water theory. The 1-degree grid data of monthly mean temperature and salinity data at standard levels in the SCS are used to solve the linearized vertical eigenvalue problem. The nonlinear parameter and the wave phase speed are computed, then the nonlinear phase speed and the characteristic half-width of ISWs are calculated respectively by two different theories to investigate the difference between these two parameters in the SCS. The nonlinearity is the strongest near the continental slope of the SCS or islands where the bottom topography changes sharply, it is stronger in summer than that in winter; it increases (decreases) as pycnocline depth deepens (shallows), stratification strengthens (weakens) and pycnocline thickness thins (thickens). The nonlinear wave phase speed and the characteristic half-width are the largest in deep sea area, they then reduce peripherally in shallower water. The nonlinear wave phase speed in the SCS changes slightly with time, but the characteristic half-width changes somewhat larger with time. In most of the SCS basin, the nonlinear wave phase speed derived from shallow-water theory is very close to that derived from finite-depth theory, but the characteristic half-width derived from shallow-water theory is about 0.2–0.6 times larger than that derived from finite-depth theory. The ISW induced horizontal current velocity derived from shallow-water theory is larger than that derived from finite-depth theory. Some observed and numerical modeled ISW characteristic half-widths are compared with those derived from shallow-water and finite-depth theories, respectively. It is shown that, the characteristic half-widths derived from finite-depth theory agree better with observational and numerical modeled results than those derived from shallow-water theory in most cases, finite-depth theory is more applicable to the estimation of ISW characteristic half-widths in the northern SCS. It is also suggested that, to derive the precise ISW parameters in further study, the physical non-dimensional ratios which are related with ISW characteristic half-width, amplitude, thermocline and water depths should be calculated, so that an appropriate theory can be chosen for estimation. 相似文献