MIKE 21 SW谱波浪模型介绍.pptx

1、MIKE 21 Spectral Wave Model FMMIKE 21 谱波浪模型Theoretical Background理论背景Ole Svenstrup PetersenHead of Innovations Coastal&Estuarine Engineering E-mail:Coastal Processes With focus on waves海岸过程 重点关注波浪Outline:大纲：Wave generatoin波浪生长Waves The Basics波浪 基本要素Wave Behavior/Processes波浪现象/过程Inside a wave波浪内部Coas

2、tal Processes Waves海岸过程 波浪Lifecycle of a wave波浪的生命周期Wind interacts with the water surface and begins to create a disturbance waves are generated.风与水体表面相互作用而产生扰动波浪开始产生。The Waves grow as the wind continues its forcing.波浪随着风的持续作用而生长The Waves propagate(with or without wind).波浪传播（伴随风或无风）They dissipate br

3、eak on a shore.波浪耗散 在岸上破碎Wave Growth波浪生长Wind speed风速Fetch or fetch length风区或风区长度Duration持续时间Normally not constant values 通常不是常量Wave Growth 3 basic components:波浪成长 3个基本要素:Range of wave heights and periods and directions:波高，波周期和波向的范围：Irregular waves with directional spreading.不规则波伴随方向扩散.Longshore curr

4、ent沿岸流Surf zone破碎带Set-up and uprush增水Coast 海岸B r e a k w a t e r防波堤Breaker line 破波线R e f l e c t i o n 反射Refraction 折射Wave front 波前Bottomfriction底摩阻S h oa l i n g浅水变形D e f o r m a t i o n变形Diffraction 绕射Refraction 折射Wavelength波长Waveorthogonal波向正交线Wind generation风生长White caps 白帽cAfter Svenden and Jon

5、sson:Hydrodynamics of Coastal RegionsWave Transformation Overview波浪变形 概述Deep waterOverview概述Complex Bathymetry=complex waves复杂地形=复杂波浪!?!?Wave focusing at shallow areas在浅水区域发生波浪的辐聚Burrow area开挖区域Navigation Channels航道Dont underestimate the effect on the waves!(and current)不要低估对波浪的作用！-（以及水流）So if we ch

6、ange the depths we change the waves!如果我们改变水深，则我们改变了波浪！Concentration集聚Concentration集聚Deeper=Faster越深=越快Reduction耗散Refraction at the sides在两边发生折射MIKE 21 Spectral Waves FM MIKE 21 谱波浪模型Walk-through of the MIKE 21 SW editor浏览MIKE 21 SW 编辑器-with special emphasis on discretization in geographical/spectral

7、space,best practice and model limitations.-重点强调在地理/谱空间上的离散、最优方法和模型的局限性。Discretization in geographical space地理空间的离散What is a“good”mesh?什么是“好”的网格？-resolve whats needed;-)解决所需要的-compromise between accuracy and CPU/RAM在精确度和CPU/RAM之间做折中处理-avoid“odd”elements and abrupt transitions避免“怪异”网格和突然转变-FS or DS?FS

8、 CPU/RAM demanding!FS还是DS？FS对CPU/RAM 有要求！Recommendations/Experience 建议/经验-spend time on the mesh!网格上的时间花费-smooth transitions!平滑处理！-5-20m in surf areas在破碎区域网格尺寸为5-20m-start simple add complexity!开始简单-增加复杂性MIKE 21 Spectral Waves FM MIKE 21 谱波浪模型Mesh samples网格示例Mesh samples with smooth transitions网格示例和

9、光滑处理Mesh samples网格示例Mesh samples网格示例Basic Equation Dialog基本方程对话框Spectral Formulation全谱公式Which model formulation to use?该使用何种模拟公式？The fully spectral formulation(FS)can in principle be used in wave studies involving wave growth,decay and transformation of wind-generated waves and swell in offshore and

10、 coastal areas.完全型谱公式(FS)一般用于模拟波浪生长、衰减、风生浪以及近海和海岸区的涌浪。However,the computationally less demanding directionally decoupled parametric formulation(DS)is sufficient in a number of situations.然而，在一些情况下用计算时间要求较低的参数化解耦公式(DS)就已足够:Examples of such cases are:这类情况如下：small scale wave transformation applications

11、(spatial scale is less than 10-50 km)小区域的波浪传播（空间范围小于10-15km）applications where fully developed seas are dominating完全成长的波浪为主要组成部分applications combined sea/swell is not important混和浪或涌浪为次要考虑因素Note,that forcing due to the wind can not be included using the in-stationary directionally decoupled parametri

12、c formulation.注意，在DS公式中非定常解法不能考虑风的作用。Time Formulation时间公式Which time formulation to use?该使用何种时间公式？The quasi stationary formulation is sufficient in a number of situations and is in general less computationally demanding thanthe instationary formulation.在很多情况下用准定常公式已经足够，且比非定常公式需要的时间少.Examples are:合适的例

13、子有：when the forcing(eg.wind/currents/boundary conditions)is slowing varying in space and time(small domains)当各种力（如风/水流/边界条件）随空间和时间缓慢变化时（小区域）fetch limited wind-wave growth有限风区的风生波when individual wave events can be considered as independent(wave statistic transformation)波浪事件可被认为是独立的（波浪统计变形）Quasi Stati

14、onary Formulation准定常公式Quasi stationary formulation准定常公式Wave field resolved at discretestationary intervals波浪场离散为一系列定常状态进行计算Quasi Stationary Formulation准定常公式“Problems”with the stationary assumption关于定常的假定Assumes physical instantaneous travel times across model grid;假定物理过程瞬时穿过模型的网格；2)Assumes waves res

15、pond instantaneously to changes in the wind.假定波浪随风瞬时改变.Usually OK in coastal studies;通常应用于海岸地区研究For open ocean:Use instationary solver对于开敞海域:用非定常的解法.Important:Check convergence!注意:校核收敛区域!FS/DSInstationary 非定常Quasi-stationary 准定常Fully spectral formulation(FS)全谱公式(FS)Instationary 非定常Quasi-stationary 准

16、定常Directionally decoupled parametric formulation(DS)方向参数化解耦公式(DS)Spectral discretization谱的离散Discretization in spectral space谱空间的离散-What is a good discretization?什么是好的离散？-resolve whats needed;-)解决所需要的Recommendations/experiences建议/经验-22.5 deg.works fine in regional/global app.在区域/全球范围应用中可采用22.5度-use a

17、 high-resolution in D-space for coastal applications(FS and DS)O(5 deg.)在海岸应用中，方向空间采用高分辨率(FS和DS)-O(5)-make sure all frequencies are resolved(FS)确保所有的频率都得到求解（FS）-also for weak winds/short fetches!(lake)同样适用于弱风/短风区!（湖）Check log-file检查log文件Spectral discretization谱的离散Separation of Wind-sea and Swell风浪和涌

18、浪分离The source term due towhite capping is as standard applied overthe entire spectrum and the integral wave parameters used in the formulation is calculated based on the whole energy spectrum.白帽相关的源项公式适用于整个波谱，用于计算的波浪参数积分应用于整个能量谱。For wave conditions with a combination of wind-sea and swell this may r

19、esult in too strong decay of energy on the swell components.在风浪和涌浪结合的情况下，波浪在涌浪部分的能量往往有着有很大的衰减Introducing a separation ofwind-sea and swell,the predictions for these cases can be improved by excluding the dissipation on the swell part of the spectrum and by calculating the wave parameters,used in the

20、 formulation of white capping,from the wind-sea part of the spectrum.可以通过采用风浪涌浪分离的方式，忽略谱中涌浪部分能量的耗散而仅对风浪部分的波浪参数（白帽公式中用到的）进行计算，以此提高模拟结果的准确性。Wind forcing风场Wind forcing风场Type of air-sea interaction two formulations(FS)空气和海水的作用类型 两种方法（FS）A coupled formulation means the momentum transfer from the wind to

21、the waves or drag depends not only on the wind butalso on the waves according to the formulation in Komen et al.(1994).“耦合”方式指从风转移到波浪的动量大小不仅取决于风也取决于波浪条件（Komen等，1994）Thus,the coupled formulation is a sea-state dependent roughness similar to the community WAM Cycle 4 wave model,WAMDIG Group(1988).“耦合”

22、方式的海水摩阻类似于WAM Cycle 4波浪模型（WAMDIG，1998）。The default value of the background roughness Charnock parameter is 0.01.It is recommended not to the change this parameter.默认的Charnock参数为0.01，建议不要改变这个参数。Wind forcing风场Type of air-sea interaction two formulations(FS)空气和海水的作用类型 两种方法（FS）An uncoupled formulation m

23、eans the momentum transfer fromthe wind to the waves solely depends on the wind speed,and consists of a sea state independent roughness description.“不耦合”方式是指从风转移到波浪的动量大小只取决于风速，并包含独立的海水摩阻的描述。You can specify either a Charnock constant(version 1)or wind drag coefficient(version 2).用户可指定Charnock常数（方式一）或

24、风阻力系数（方式二）。For open oceans a Charnock parameter of 0.01 is typicallyused while a value of 0.0185 has been suggested for coastal areas.对于开敞海域Chsrnock参数一般取为0.01，海岸地区建议设为0.0185。The default drag law is taken from Smith and Banke(1975).默认阻力定律基用Smith和Banke(1975)。Wind forcing风场Type of air-sea interaction t

25、wo formulations(FS)空气和海水的作用类型 两种方法（FS）Recommendations 建议For large scale applications(say,spatial scale 100 km)it is recommended to use the coupled formulation with default values.对于大尺度应用（空间范围大于100km），推荐采用耦合方式并使用默认值。For small scale(high-resolution)applications(say,spatial scale 10-100 km)the use of t

26、he coupled formulation may result in an overestimation of the sea surface roughness(for strong winds)and thus an overestimationof the significant wave height对于小范围应用（空间范围小于10100km）采用耦合方式会导致海水表面摩阻过高，则导致有效波高过高。Improved model results have been obtained using an uncoupled formulation of the air-sea inter

27、action,eg.the drag law proposed by Smith and Banke(1975).采用不耦合的方式，例如阻力准则使用Smith和Banke(1975)，可以修正模型结果。This is default(drag)in MIKE 21 SW is the coupled formulation.MIKE 21 SW默认采用耦合方式。Going global on a workstation.全球预报模型0.5 spatial resolution requires app.2.7 GB RAM 0.5的空间分辨率要求2.7GB的内存0.25 spatial res

28、olution requires app.6 GB RAM 0.25的空间分辨率要求6GB的内存SampleJanuary storm 2005 in the North Atlantic Very accurate forecast data2005年1月北大西洋的风暴非常精确的预报数据Going global on a workstation.全球预报模型Atlantic model 大西洋模型Number of elements:8334网格数：8334Maximum edge length:1.0 degree0.5 degree最大边长：1.0度Minimum edge length

29、:最小边长：0.5度North Sea-Baltic Sea model北海-波罗地海模型898540 km1.5 kmNumber of elements:网格数：8985Maximum edge length:最大边长：40 kmMinimum edge length:最小边长：1.5 kmLarge scale applications大范围模拟应用In connection with the construction of the resund Link wave measurements at a number of locations exist.在resund Link 工程范围

30、内，一些地点有波浪实测值。Wind and wave model arearesund case resund工程实例OskarsgrundetFlintenDrogdenWindresund case resund工程实例Measured wind实测风速resundresund case resund工程实例-and with 0D(spatial constant wind)wind field海水相关联的表面摩阻方法-采用0D（空间定常风）风场den LighthouseFlinten Directional WRresundresund case resund工程实例Model results-waves模型结果-波浪Sea state dependent surface roughness description模型结果 不耦合Sea state independent surface roughness description-and with 0D and 2D wind field海水独立的表面摩阻方法-采用0D和2D风场en Lighthouseresundresund case resund工程实例Model results-uncoupled