搜索到87篇“ PYCNOCLINE“的相关文章
跃层厚度对内孤立波能量耗散的影响
2024年
内孤立波破碎混合是陆架地形上海洋混合过程重要的能量汇,为了探究内孤立波在连续跃层密度分层中能量变化及能量耗散规律,本文使用OpenFOAM建立数值水槽,基于双曲正切曲线设置连续跃层密度分层开展了一系列工况的模拟,针对跃层厚度对内孤立波能量传递及其耗散进行了详细分析。结果表明跃层厚度与跃层处流速剪切存在着负相关关系,随着跃层厚度的增加能量耗散先减小后增大。跃层厚度较小时,跃层处流速剪切强,理查德森数小,易产生开尔文-亥姆霍兹(Kelvin–Helmholtz)不稳定现象;随着跃层厚度的增大,流速剪切减小,理查德森数增大,开尔文-亥姆霍兹不稳定消失;跃层厚度达到临界值后,层结稳定性减小,理查德森数减小,流场的翻转混合过程加强,能量耗散也明显增强。
张群星徐昱刘娟孟静王桂霞陈旭
关键词:内孤立波OPENFOAM能量耗散
连续密度跃层中第二模态内孤立波及其波致流场实验研究
2024年
该文在大型分层流水槽中开展了连续密度跃层中第二模态内孤立波及其波致流场的实验研究。利用分层流体重力塌陷原理,该文实验模拟了连续密度跃层中“上凸下凹”型的第二模态内孤立波,利用电导率探头阵列和粒子图像测速技术测量第二模态内孤立波及其波致流场,获得了连续密度跃层中充分发展第二模态内孤立波的几何与波-流场非均匀结构,以及波幅变化对第二模态内孤立波的波要素关系和波致流场特征的影响。研究结果表明:连续密度跃层中,第二模态内孤立波波形几何特征表现为上凸下凹的卵形波包状,波形非均匀垂向结构特征表现为波幅和波长随深度的非均匀变化;第二模态内孤立波波包上凸与下凹域分别形成逆时针和顺时针环流,两者组合为一对上下反对称的环流并共同向前传播;第二模态内孤立波波速随波幅的增大而增大,波长则随波幅的增大而减小;水平和垂向流速强度与特征波幅呈正相关关系,且水平流速强度大于垂向流速强度。该文提升了对实际海洋层化条件下第二模态内孤立波及其波致流场的认识。
王少东杜辉彭湃宣谱王观景陆哲宇魏岗
引入强分层近似对含密度跃层情况下的大幅内孤立波计算误差研究被引量:3
2023年
At present,studies on large-amplitude internal solitary waves mostly adopt strong stratification models,such as the twoand three-layer Miyata–Choi–Camassa(MCC)internal wave models,which omit the pycnocline or treat it as another fluid layer with a constant density.Because the pycnocline exists in real oceans and cannot be omitted sometimes,the computational error of a large-amplitude internal solitary wave within the pycnocline introduced by the strong stratification approximation is unclear.In this study,the two-and three-layer MCC internal wave models are used to calculate the wave profile and wave speed of large-amplitude internal solitary waves.By comparing these results with the results provided by the Dubreil–Jacotin–Long(DJL)equation,which accurately describes large-amplitude internal solitary waves in a continuous density stratification,the computational errors of large-amplitude internal solitary waves at different pycnocline depths introduced by the strong stratification approximation are assessed.Although the pycnocline thicknesses are relatively large(accounting for 8%–10%of the total water depth),the error is much smaller under the three-layer approximation than under the two-layer approximation.
许存国王战Hayatdavoodi Masoud
关键词:PYCNOCLINE
跃变分层流体中球体内波散度场特征实验研究
2023年
本文对跃变分层流体中匀速拖曳运动球体内波诱导流场PIV试验测量得到的水平速度散度场随时间的演化过程及内波时频、波谱、传播速度等特征进行了研究。球体处于跃层中,测试水平面位于球心下方一倍直径处。分析获得了速度散度场整体特征及其随内傅氏数F_(ri)=U/N_(max)D的变化规律,比较分析了体效应内波(Lee波)和尾流效应内波(WIW波)的时频、波谱、传播速度等波动特征。研究表明:(1)在低F_(ri)时Lee波占优,水平速度散度等值线呈内凹的“>”形,在最大浮力振荡频率f_(max)附近有非常明显的频率主峰,速度散度曲线的波谱主峰也非常明显,内波传播速度与球体运动速度基本一致;(2)在高F_(ri)时WIW波占优,水平速度散度等值线呈“■”形,频谱曲线上明显存在多个峰,且主频接近球体潜深位置当地浮力振荡频率,波谱曲线上也存在多个较明显的峰,对应WIW波波长在2.4D~5.6D之间,传播速度远低于球体运动速度;(3)在高F_(ri)时WIW波分界线的斜率与参数F_(ri)呈指数分布,在低F_(ri)下Lee波包络线的斜率也符合此分布规律。
张军姚志崇高德宝周根水苏博越
关键词:分层流
密度跃层对潜艇操纵运动的影响及应对措施研究被引量:3
2021年
针对海洋密度跃层严重影响潜艇水下变深操纵运动规律,易引发失控、掉深等险情,严重威胁潜艇航行安全,基于中国海密度跃层分布特征统计资料和潜艇空间运动数学模型,采用计算机仿真的方法,分析了正跃层和逆跃层分别对潜艇变深操纵的影响以及逆跃层中潜艇受扰后的自由运动规律,提出了相应的操纵注意事项和应对措施。结果表明,正跃层有利于潜艇保持深度和进行悬停操纵,若需转换深度长时间航行则应及时均衡潜艇;逆跃层对潜艇航行安全威胁最大,指挥员需密切关注海水密度及潜艇深度变化情况,深度发生异常时则应及时增速并均衡潜艇。
张建华黄海峰胡坤刘广旭
关键词:潜艇
Effects of westward shoaling pycnocline on characteristics and energetics of internal solitary wave in the Luzon Strait by numerical simulations
2021年
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.
Haibin LliYujun LiuXiaokang ChenGuozhen ZhaShuqun Cai
关键词:PYCNOCLINE
人工形成海水密度跃变区的过程及方法
2021年
海水密度的人工跃变技术是通过人工方法形成足够规模海水密度跃变区,继而影响潜艇正常航行。技术应首先研究规模适度、气泡密度合理的跃变区形成方法。立足现有工业技术条件,完成了对基于气体射流法的跃变区生成设备的总体设计。详细对关键射流部件压力容器和气泡发生器作出设计说明:一是设定压力容器的结构和型式,考虑到球壳强度、射流结构、形成连续分布的跃变区,对其两相邻开孔所夹的最大球心角作出规定。二是选用喷嘴型微型气泡发生器,应设定其结构尺寸和容器开孔。最后气体射流成泡和设备拉伸运动两部分同时进行,形成海水跃变区。研究成果对于技术的工程应用提供重要的理论指导。
张志友何升阳蒋永馨郑振宇
关键词:气体射流压力容器气泡发生器
Methane increase over the Barents and Kara seas after the autumn pycnocline breakdown: satellite observations
2019年
Seven operative thermal infrared(TIR)spectrometers launched at sun-synchronous polar orbits supply huge amounts of information about Arctic methane(CH4)year-round,day and night.TIR data are unique for estimating CH4 emissions from a warming Arctic,both terrestrial and marine.This report is based on publicly available CH4 concentrations retrieved by NOAA and NASA from spectra of TIR radiation delivered by EU IASI and US AIRS sounders.Data were filtered for high thermal contrast in the troposphere.Validation versus aircraft measurements at three US continental sites reveal a reduced,but still significant sensitivity to CH4 anomalies in the troposphere below 4 km of altitude.The focus area is the Barents and Kara seas(BKS).BKS is impacted with warm Atlantic water and mostly free of sea ice.It is a shelf area with vast deposits of oil and natural gas(~90%CH4),as well as methane hydrates and submarine permafrost.Although in summer AIRS and IASI observe no significant difference in CH4 between BKS and N.Atlantic,a strong,monthly positive CH4 spatial anomaly of up to 30 ppb occurs during late autumn–winter.One of explanations of this increase is a fall/winter pycnocline breakdown after a period of blocked mixing caused by a stable density seawater stratification in summer:enhanced mixing lets CH4 to reach the sea surface and atmosphere.
Leonid YURGANOVFrank MULLER-KARGERIra LEIFER
关键词:ARCTIC
密度跃层中潜航体激发内波的数字纹影实验研究
2019年
为了找到利用海洋内波场探潜的方法,研究了在三分层流环境中,运用数字纹影技术垂向观测潜航体在密度跃层航行所激发的内波场。实验中,弗劳德数Fr∈(0. 6,4. 0),观测到潜航体激发的内波场呈">"型类凯尔文波,开口方向与航行方向相反,波峰线略呈弧形,张角逐渐增大。实验结果表明:偏移航行线距离相同时,相邻波峰线之间的间隔,即拖曳方向波长λx与Fr呈正比;偏移航行线距离不同时,λx没有明显差异。为定量刻画">"型内波场波峰线的弧形特征,着重在实验图像中央与边缘区域测量了波峰线的切线与航行线的航切角,测量结果表明:张角随着偏移航行线距离增大而增大;偏移航行线距离一定时,">"型内波波峰线的张角随Fr增大而减小,顺下游方向张角随流向距离增大而减小。研究结果表明:数字纹影技术垂向观测是测量潜航体激发三维内波场目标特征的一种高效率和无干扰全场测量技术。
尹政蒋小勤
关键词:内波密度跃层
海水密度的人工跃变技术研究被引量:3
2017年
提出一种海水密度的人工跃变技术,其核心思想是利用专门的材料和设备,通过特定机理在设定海域产生大量均匀分布的气泡,以形成足够规模的低密度海水区域,从而影响潜艇正常航行。通过验证性实验,分析不同大小及数密度的人工气泡制造海水跃变的实施效果和影响规律。实验结果表明:在静水中,气泡越小对潜艇航行"掉深"影响越大;在一定范围内,适当增加气泡的数密度能明显加大"掉深"深度。研究结论证明海水密度人工跃变思想的可行性与有效性,为潜艇军事打击手段的进一步完善以及装置的研制提供必要的基础和依据。
何升阳金良安张志友胡广友
关键词:舰船海水密度军事应用