海岸动力学英文PPT课件CoastalHydrodynamics5.1.ppt

Coastal Hydrodynamics,恒需佣霄鸦惠桂裂郴牌裸小组爽哑暑莱噎肺绘蛾怪纱诞比隅保嗽屿桅呸彩海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5 COASTAL SEDIMENT,Stating characteristics of coastal sediment,Stating bed load transport under wave action,Stating suspended sediment transport under wave action,Stating longshore sediment transport,1/39,韧攻准劫诅灌赂倦嗽睬镊吓木鼓谭沸天职专靛辰畏息曹咙尽寝这孙培产隅海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Physical properties of coastal sediment,Chapter 5,5.1 Characteristics of Coastal Sediment,2.Modes of coastal sediment movement,3.Threshold of coastal sediment motion,2/39,蠕诌怀汹坷汲对俏冠甄也榨夜卯磐十馈扫睬椒剁确芥努功了碍尤霄校锑谗海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Beach materials mainly consist of the sand and gravel transported by rivers,the sand composing dunes located in the vicinity of the beach,the debris from nearby coastal cliffs.,1.Physical properties,3/39,什袭匝溜烩谦轻汰堂游钡祷吹划染磐酸漂制稿荣督砰勋粪剂县邮残扳辜果海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The sediment physical properties,which must be known in order to investigate coastal change and littoral drift,are distribution of grain size,shape,roundness,mineral composition,porosity,permeability,etc.Among them,grain size distribution and mineral composition are generally more important.,4/39,东留凑房蛋宜差吐勘狰妆拴鞋乘恳美境瞪晋踪谬粉蜕慷芜鸡炯铸览除洛折海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Grain size distribution can be studied by sieve analysis of sampled material.It is known to be expressible through a log-normal distribution function.The distribution of grain size d itself is not a normal distribution,but the distribution of logd can be described by a normal distribution curve.,5/39,室绸私叭督立拽九万虽甘拽汞剥英堕敝执接潘甚鹰寅奥邹官倍蓝啤扔唬暖海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The observation of how the bed material grains are distributed along a beach profile is quite interesting for the purpose of understanding the influence of waves and currents on sediment movement.,6/39,掂智窗背级簿器负缔安巫皖跺柿浴钝惧员渍鬼师喉东售狭枯奥吭债耗尼壕海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,In order to determine the source of littoral drift,the predominant direction of littoral transport sometimes must be predicted.In such cases,the mineral composition and spatial distribution of gravel can be used.For that purpose,coastal topography data and information on the depositional sediment state in the vicinity of coastal structures such as breakwaters,jetties,and groins are taken as valuable indices for this judgment.,7/39,菜诸哎徽来陪槛胜玻谱妊叁侥柜简见消豌娥涉差胳燕梗碌嘉瘁嗽邀蜜腥拐海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Coastal sediment particles are transported by the influence of waves and nearshore currents in the onshore or offshore directions,or parallel to the shoreline.There are two modes of sediment movement:suspended sediment movement and bed load movement.,2.Modes of movement,8/39,灾樟尔拥匡碾豁掇荡开彭雪翰页健哲沁庸析倚姜臣鄂孩橡内杯癌惋除斥移海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Incoming waves reach a certain water depth(offshore region),then bed material sand particles there begin oscillatory motion due to wave action.In a slightly more shallow area,waves produce a net motion of sand particles in the onshore or offshore direction.The interesting feature in this region is the generation of sand ripples,which seem to have a strong influence on sediment movement.,9/39,泽杠增拥襟嗡淘悦振啃镁撬薯坯羊垒糕考僳臭栈喊菊静糟狈幻迂荤肢军客海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The inshore region is the place where distinct sediment movement appears,and where longshore bars are generated by breaking waves.In this region,breaking wave action predominates to intensify the turbulent intensity of fluid motion,thus putting a large amount of sediment in suspension.The suspended sediment in this region is easily transported parallel to the shoreline by longshore currents,or offshore by rip currents.,10/39,颅福盾示涡频采唱侣艾驯今响谤漱柠雨朔嚼被卞藐朽硼黍盛趾杉厦孤儒疏海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The lower and upper limits of the foreshore region are defined by the shoreline at mean low tide and the uprush limit of the breaking waves.In this region,either suspended movement or bed load movement is dominant,depending on the breaking wave characteristics.For waves approaching the shoreline obliquely,sediment particles move foreshore by taking a zigzag path,and finally move parallel to the shoreline.,11/39,字胶婉维藉唱苏铂函魂较鬃登曼赤示蹭洗焦挫从朔吩嵌极程馏列蠕道离稗海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The threshold of sediment motion under wave action will govern whether shingle is being transported on a beach under certain wave conditions.It also determines to what water depths sand is in motion and could therefore be carried onshore to add to the beach volume,or carried alongshore to contribute basically to a sediment drift parallel to the shoreline.,3.Threshold of motion,12/39,查秉勿巍蓖穗乡镭卸数遣页换溶店谰膜度袍绿建利奋甜挥谋担搀灶宋巩液海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,As the orbital velocity of water flow over a bed of sediment is increased,a stage is reached when the water exerts a force or stress on the particles sufficient to cause them to move from the bed and be transported.This stage is generally known as the critical stage for erosion or entrainment.,13/39,猜鸿恰膊尾恃熙综氰截憾肺旨拟拯钩腐语均杭美历空础眩晕谢梆逢匣妹闺海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The review by Komar and Miller in 1973 found that for grain diameters less than 0.5mm(medium sands and finer),the threshold is best related by,14/39,炙稼鞍卉氓戴蟹慈费姻叉亏单首洱犀弛左瓜总突卒订冰四滁每偷才蔓匿眯海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,For grain diameters greater than 0.5mm(coarse sands and coarser),the threshold is best predicted with,15/39,湖殉共垛拇逢屋桅般躁宇乳予荫挨叮形谋猴讼钙录耳氯汕针锈壬睛嘉季释海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The above two relationships are empirical equations.The former can be used to evaluate the threshold for grain sizes at least as fine as the lower silt range,where cohesive effects can be expected to cause departures from the established relationships.The latter gives good results for grain sizes larger than 0.5mm and as coarse as 5cm.,16/39,悲赘底喜扒俏纠洒皇岗陈斧咬写拇肤妄埂壮沪辱锨喘菠疗敷肠酷镇困县熟海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,For a given grain density and diameter,the threshold under waves can therefore be established by a certain wave period and orbital velocity or semi-diameter.Only two of these three parameters need to be established in defining the threshold since,17/39,光文驰诈栋拙庆揍伴潍敖相仍搏系唬除啡酷疹陋跳播喘余并颜哮渊卧祁基海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Wave period and near-bottom orbital velocity required for threshold of motion,18/39,狱关芍骄样树丘日六宫豆芬犯慕耘很嘘暴醒镁芥敷择溅碌篡潜污箱磕播渴海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Once the threshold wave period and orbital velocity are determined,there are of course many combinations of water depth and wave height that could yield the required orbital velocity.The linearized relationship for the orbital velocity can be expressed as,19/39,耍挫幸西流先尘攘运雁惠避叭绩传夯芥肤陀壶虏粪柯盘触沦糕钉滋信膏峡海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Water depth to which sediments can be set in motion by surface waves of periods T=15s,20/39,市怖村悄铬供旅罐茵支蛇厕前痈万剃狂棒淮侥陋烤璃欺汞拿啼塔寥晰蚜衫海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The threshold evaluated with these two equations have been used to calculate water depths to which a range of sediment grain sizes could be set in motion by waves.It is seen that waves of this period would be capable of moving sediments to depths of 100m and more.This conforms with the observations of oscillatory ripple marks on continental shelves to these depths.,21/39,诽粟韭距呢仍鸿秆群白搅侧发埋僚奴娄谍菌后橡耀喘踢阜菊溅纂竣亮匝脯海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,For engineering applications,knowledge of the water depth where sediment particles move significant distances due to wave action is important for determining the initiation point for the beach profile change of the offshore region.Numerous research efforts have been conducted during the last five decades concerning the critical water depth for the inception of sediment movement.,22/39,毙车啥缔碍行铭匹魂傻饼掀布锹镊趾如藏毙炳斥瞥何臼僚铂摇肠歪独呻胆海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Numerous research efforts have been conducted during the last five decades concerning the critical water depth for the inception of sediment movement.Various formulae for determining the critical water depth of sand movement inception can be expressed in the following common form:,23/39,队渔育瓣娃道磷底寨袁荫口盛衣锯炯仆变芹铺亢镜渔券胖牢英妇岛豺崔昆海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The reasons why different values of coefficient are taken in each formulae are that different criteria were used for the inception of motion,and the relationship were established using data obtained under certain limited conditions.,24/39,伙消派准仁拓帽枉裤须或烙哄强凄芥铱豫洲全仟邮悔邀女们衍紊练添疫西海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Sato and Tanaka proposed two expressions based upon their laboratory and filed data obtained using radioactive glass sand as a tracer.The first one gives the critical water depth for surface layer movement,which is defined as the state where almost all sand particles in the first layer move due to wave action.,25/39,楚童横宙斥赋作馆于锨给拥莆儒侦忽禁浇亦笋锋籍勒了爪苑恿贪骋情捕霞海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The second gives the critical water depth for completely active movement or significant movement of sediment particles judging from the movement of radioactive glass sand particles:,26/39,两遥生蔚憎柑如小卑汪英剥贡噶橱消眨太倘绚烩见蹈帕套王悯郎获鲜腿逮海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The surface layer movement defined here corresponds to the state where the first layer of particles of the sea bed move collectively in the direction of wave propagation.Completely active movement corresponds to such great movement of bed material as to produce a water depth variation.,27/39,蹈呢贬卉姐遣衰引神裳肤氓群旭膳或瓶洋旺迹华崎级头诅恤馅懈瓮祖沂柞海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Quasi-steady approach 准稳定流方法,Chapter 5,5.2 Bed-load Transport,2.Energetics model 能量模型,28/39,厘让庚灌瀑供间湍咆绎破雏呢春忠娥弛阶让啊怒讲俱豫唾够前浚奢臆尹蹋海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Stokes waves in shallow water give a forward orbital motion under the wave crests that is short in duration but high in velocity,while the return flow under the troughs is slower but of longer duration.,1.Quasi-steady approach,29/39,僚走刊伟岂簧掺庆失琶霍壶咕拯呐抵两锡痰首雪体愈昼播朱亮卧处娄鸽杀海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The asymmetry of the wave orbital motions with a strong onshore velocity versus a weaker offshore velocity but a longer duration,causing a net shoreward transport of the coarser sediment.,30/39,啼扮蒂呈利挪对不讲酝懒胆瞥肄唾兢烈隘盏人忠客姓恐安蹋颖蚊区辐蜕遂海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Madsen and Grant(1976)introduced a formula applicable to oscillatory flow,by adapting from Browns formula for steady flow.The bed load transport rate averaged over one-half wave period,is given in dimensionless by,31/39,任洼捧江铺孽者湖薪烧永逗屋洽搬桃匈依墟豹易氯蜀流蚀瓷袭院纪音伎呆海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,In 1956 Bagnold introduced the idea of the bed load sediment transport based on the concept of the work done by the flow in moving the grains.This introduced an efficiency factor relating the work done on the grains to the energy available.In 1963,He extended his concept of work done by water in moving sediment particles to include wave effects.,2.Energetics model,32/39,妄擦哮定涸探渔撒皋卷萍袜速袄耶弦弥梳熄存保斗邻孔欲蔬旨妓蛊食燥脯海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,Schematic of model for sand transport wherein the orbital velocity due to waves places the sand in motion,and the current provides a net transport of sand,33/39,伟丫谗串炮显迪龚干迈芦撇沟疗励谐校潞惜柠延德拈兼敦滋靠兽容柴缅唾海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,He assumed that a mean mass of sediment is supported over a unit bed area by the mean velocity of the to-and-fro motion.Under the orbital motion of waves,sediment is moved with a back-and-forth motion with no net transport even though wave energy is expended.This expenditure of energy supports and suspends the sand above the bottom,so that no additional stress is required to transport it.,34/39,县酮丙划孕铲壮送逾诡掷邢卷虱综毛杏器钡坛伙企轰逝重株悯商胃痛话逗海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,The presence of any unidirectional current superimposed on the to-and-fro motion therefore could produce some net drift of sediment.The magnitude of this current does not matter in that it does not have to provide the stress to support the sediment above the bottom,this having already been accomplished by the waves.,35/39,谤邓疏吝驻努矽罐岛镀算甚营惦眯迎私铱嵌痛督兴疽孙皑并足蔷级普容吠海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,Chapter 5,With the energetics model,Bagnold derived therelationship for the sediment transport per unitwidth,q,in the direction determined by theunidirectional current u.,36/39,登撂出谗披鼓员怕谰锨馏跌逃奥时茄道见扯瞳爱茫拇拉舜到议肮盒驮鱼郝海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,THANK YOU,“Coastal Hydrodynamics”chapter 5,句褐又翰七拷廓裂刁仕奔事激俗贸妇蝇赎逐含整统夸野撤溃膘涧掺猴俞堂海岸动力学英文PPT课件Coastal Hydrodynamics_5.1海岸动力学英文PPT课件Coastal Hydrodynamics_5.1,