Laboratory experiments on low-crested breakwaters

New unique laboratory experiments on low-crested structures (LCSs) have been performed within the DELOS project. The experiments were carried out in three European laboratories aiming at extending and completing existing available information with respect to a wide range of engineering design properties such as structural stability, wave and current flows and wave transmission. 3D wave basin tests were performed to provide information especially about the wave obliquity, where almost no research has been done before. Flow velocities inside and close to the surface of structures were studied in a wave channel at small scale, and scale effects regarding wave transmission and reflection were studied in a wave channel at a large scale facility. The paper describes the experiments and associated databank with respect to objectives, test program, set-ups and measurements. Results, guidelines and recommendations elaborated from the tests are included in the other companion papers of the Coastal Engineering Special Issue on DELOS.     

Model experiments on moored ships

At present the position keeping of ocean going vessels, offshore service vessels, etc., is performed by mooring systems to resist external forces under severe environments consisting of wave, current and wind. A variety of mooring systems are employed depending on the shape, principal dimensions, etc., of the vessels in addition to the surrounding conditions of the water areas. Ocean going ships are moored to the shore structures through a multiple system of moorings. The determination of the forces in the cables is essential for the design of moorings and the berthing structures. However, the ships engaged for offshore operations are moored by the mooring cables, spread around the ships with the other ends of the moorings anchored to the sea bed. In these cases, the required number and length of cables can be arrived for a given ship of known dimensions and environmental conditions. With the increased overall dimensions of the vessels, it is necessary to conduct a study on enhancing the accuracy in estimating the mooring system performance. Hence, the present work is mainly intended to carry out model tests to investigate the behaviour of moored ships that are subjected to wave and current loadings. These model experiments were conducted in a 30 m × 2 m × 1 m wave-current flume at the Ocean Engineering Centre, Indian Institute of Technology, Madras.     

微型浮游动物摄食实验——稀释法中浮游植物负生长的可能原因分析

稀释法(dilution technique)是研究微型浮游动物摄食和浮游植物生长的常用方法之一,负值浮游植物生长率是稀释实验中常见的现象。分析了造成负值生长率出现的因素,以及这些因素对实验结果的影响,并提出了防止不利影响产生的措施。负值生长率的出现不能简单地视为实验失败的标志,培养光照和温度条件、取样误差、无颗粒水污染、营养盐污染和限制等都可能造成负生长率的出现,且对实验结果的影响不同。同时,根据实验结果,演示浮游植物光适应、取样误差、无颗粒水污染和加富营养盐对稀释实验的影响。结果显示,光照条件可以改变细胞色素含量,且不同浮游植物类群对光照条件的响应不同,从而导致基于色素分析的稀释实验结果出现误差;取样混合不均,可造成取值偏低,导致浮游植物生长率估值偏低,甚至为负值,但可能不影响对摄食率的估算。另外,实验污染(无颗粒水和加富营养盐污染)往往会抑制浮游植物生长,甚至造成浮游植物死亡。因此,培养条件模拟和人为干扰控制是稀释实验成功的关键。     

Numerical experiments of internal tides in Suruga Bay

Numerical experiments were performed to explain the observed results of the internal tides in Uchiura Bay. The experiments for the generation of the internal tides in Suruga Bay indicate that the internal tides, generated at the slopes in the bay, are not as large an amplitude as those observed in Uchiura Bay. However, when the semidiurnal internal tides incident through the mouth of Suruga Bay are considered, they are amplified. The amplitude at the head of Uchiura Bay is 6–12 times larger than that at the mouth of Suruga Bay under the summer density structure. Under the fall density structure, the amplitude ratio is approximately 4–6. The amplification of the semidiurnal internal tides in Uchiura Bay is considered to be due to resonance of the longitudinal internal seiche of Uchiura Bay. On the other hand, the calculated diurnal internal tides are not as large as those observed. Therefore, the diurnal internal tides are thought to already have these large amplitudes at the mouth of Suruga Bay. Therefore, from the observations and numerical experiments, it is concluded that the internal tides observed in Uchiura Bay are mostly the internal tides originating from the outer region of Suruga Bay, and the semidiurnal tides are the internal seiche which is resonantly amplified.     

Changes in average and extreme precipitation in two regional climate model experiments

Two regional climate model experiments for northern and central Europe are studied focussing on greenhouse gas‐induced changes in heavy precipitation. The average yearly maximum one‐day precipitation P _max shows a general increase in the whole model domain in both experiments, although the mean precipitation P _mean decreases in the southern part of the area, especially in one of the experiments. The average yearly maximum six‐hour precipitation increases even more than the one‐day P _max, suggesting a decrease in the timescale of heavy precipitation. The contrast between the P _mean and P _max changes in the southern part of the domain and the lack of such a contrast further north are affected by changes in wet‐day frequency that stem, at least in part, from changes in atmospheric circulation. However, the yearly extremes of precipitation exhibit a larger percentage increase than the average wet‐day precipitation. The signal‐to‐noise aspects of the model results are also studied in some detail. The 44 km grid‐box‐scale changes in P _max are very heavily affected by inter‐annual variability, with an estimated standard error of about 20% for the 10‐year mean changes. However, the noise in P _max decreases sharply toward larger horizontal scales, and large‐area mean changes in P _max can be estimated with similar accuracy to those in P _mean. Although a horizontal averaging of model results smooths out the small‐scale details in the true climate change signal as well, this disadvantage is, in the case of P _max changes, much smaller than the advantage of reduced noise.     

一次温带气旋的同化试验

温带气旋在浙江海域入海发展形成的瞬时大风和大浪常常会造成船只倾覆、人员伤亡等灾情。本文采用WRF中尺度数值模式对一次入海温带气旋过程进行3个试验分析,包括试验一(不同化任何资料)、试验二(将未经质量控制的云迹风资料全部放入模式同化)和试验三(将经质量控制以后的云迹风资料放入模式同化)。通过对高度场和风场等的模拟,并与实况对比,表明将经质量控制的云迹风资料放入模式可以较大程度改进温带气旋的模拟结果,为提高影响浙江海域的温带气旋预报的准确率提供一定参考。     

Interlaboratory calibration experiments using the polychaetous annelid Capitella capitata

An interlaboratory calibration experiment was conducted at three laboratories to test two sources of variation associated with bioassay experiments, variation due to the experimenter and to the natural seawater. Twenty-eight day static (with frequent media renewal) bioassays exposing the polychaete Capitella capitata to cadmium were conducted with synthetic and natural seawaters. Test results varied between the three laboratories; however, the variations are most probably explained by the shipment of the experimental animals to the participating laboratories.     

In-situ experiments reveal mineralization details of porphyry copper deposits

In-situ hydrothermal experiments using diamond-anvil cell show that sulfate and sulfide are the dominant sulfur species under P-T conditions similar to those of...     

Three-dimensional experiments on landslide generated waves at a sloping coast

This paper describes new three dimensional experiments on water waves generated by landslides. The landslide is reproduced by a rigid elliptical body, sliding along an inclined plane (slope of 1/3, 1 vertical, 3 horizontal). The generated water waves are free to propagate both offshore and alongshore, since the plan dimensions of the used wave tank are of at least one order of magnitude larger than the width of the landslide, which can be considered to be a scale of the wave length. The experimental study has been carried out reproducing both subaerial and partially submerged landslides. The wave generation process is studied by means of video records of the near field flow and measurement of the landslide movement; the properties of the waves propagating along the coast are described on the basis of runup gauges. The waves observed during the experiments always present first a crest and then a trough; as the first wave propagates away from the generation area the crest tends to become smaller than the trough and the maximum runup along the coast is given by the second or by the third wave. An important feature is that the observed runup along the coast firstly grows with the distance from the generation area, it reaches a maximum value at about two times the width of the landslide, and then decreases. An estimate of the celerity at which the waves propagate along the coast is given on the basis of gauge measurements; it results that the crests propagate faster than the troughs, and the wave period increases.     

An implosive seismoacoustic source for seismic experiments on the ocean floor

Bottom shots have been used for a number of years in seismic studies on the ocean floor. Most experiments utilized explosives as the energy source, though researchers have recognized the usefulness of collapsing water voids to produce seismoacoustic signals. Implosive sources, however, suffered generally from a lack of control of source depth. We present a new experimental tool, called SEEBOSEIS, to carry out seismic experiments on the seafloor utilizing hollow glass spheres as controlled implosive sources. The source is a 10-inch BENTHOS float with penetrator. Inside the sphere we place a small explosive charge (two detonators) to destabilize the glass wall. The time of detonation is controlled by an external shooting device. Test measurements on the Ninetyeast Ridge, Indian Ocean, show that the implosive sources can be used in seismic refraction experiments to image the subbottom P-wave velocity structure in detail beyond that possible with traditional marine seismic techniques. Additionally, the implosions permit the efficient generation of dispersed Scholte waves, revealing upper crustal S-wave velocities. The frequency band of seismic energy ranges from less than 1 Hz for Scholte modes up to 1000 Hz for diving P-waves. Therefore, broadband recording units with sampling rates >2000 Hz are recommended to sample the entire wave field radiated by implosive sources.     

An ocean-bottom hydrophone recorder for seismic refraction experiments

A new and inexpensive pop-up ocean-bottom hydrophone recorder has been developed for use in seismic refraction experiments. It is capable of operating in water depths of up to 4000 m and in very rugged topography, and uses an acoustic command system built by the U.K. Institute of Oceanographic Sciences for recovery. The instrument is mounted in an inexpensive cylindrical pressure case based on commercially available extruded aluminium alloy tubing, and uses glass spheres and syntactic foam for buoyancy. Hydrophone and clock signals are frequency modulated and recorded on tape cassettes, with a recording duration of three hours allowing up to 18 programmed shot windows. The prototype has made seven free descents on the Mid-Atlantic ridge and in the Gulf of Oman, and successfully recorded shots under operational conditions for the first time in September 1979. The total component cost of the prototype was £2740 (1979 prices).(Department of Earth Sciences, University of Cambridge Contribution No. ES135).     

历次核试验进入海洋的~(137)Cs对中国近海影响的模拟研究

1945年以来,世界各主要核国家进行了数千次核试验,这些核试验产生的绝大部分放射性物质通过多种途径进入海洋,对海洋环境造成放射性污染。本文建立了一个准全球海洋的放射性物质输运和扩散数值模式,通过数值模拟手段评估了历史核试验释放的放射性物质137 Cs对中国近海海洋环境的影响。本文借助前人工作评估了核试验释放137Cs进入海洋的途径和总量;通过比较模拟结果与观测资料,表明本文建立的放射性物质模式能够较好地模拟出137Cs在中国近海及其邻近海域的分布情况和随时间演变特征;模拟结果表明中国近海里的137Cs浓度在20世纪50年代中期达到最大,其中吕宋海峡海域137Cs浓度最高,达80.99Bq/m3;进一步分析了2011年3月份日本福岛核事故前中国近海137Cs浓度分布状况,2011年整个中国近海137Cs浓度介于1.0~1.6Bq/m3间,且其浓度垂向分布较均匀,相对封闭的南海浓度略高于其他海域。     

Development and experiments of the Sea-Wing underwater glider

Underwater gliders,which glide through water columns by use of a pair of wings,are efficient long-distance,long-duration marine environment observatory platforms.The Sea-Wing underwater glider,developed by the Shenyang Institute of Automation,CAS,is designed for the application of deep-sea environment variables observation.The system components,the mechanical design,and the control system design of the Sea-Wing underwater glider are described in this paper.The pitch and roll adjusting models are derived based on the mechanical design,and the adjusting capabilities for the pitch and roll are analyzed according to the models.Field experiments have been carried out for validating the gliding motion and the ability of measuring ocean environment variables.Experimental results of the motion performances of the glider are presented.     

Numerical experiments of HAB inducement in Qingdao adjacent coastal area

A three-dimension ecological dynamic model was established to numerically study the relationship of HAB and environmental conditions.The numerical experiments showed that the growth of diatom,the dominant HAB specie,was mainly restricted by phosphate and silicate.If the concentrations of phosphate and silicate reach 17-25 μg/L and 300-375 μg/L respectively,the water is in a state of eutrophication.When phosphate and silicate up to 26-32 μg/L and 350-500 μg/L respectively,HAB could be induced.The major regions of HAB occurrence are Jiaozhou Bay mouth,coastal bays,and coastal area from Maidao to Shilaoren.To avoid HAB occurrence,concentration of phosphate and silicate should not exceed 17-20 μg/L and 300 μg/L as a whole.Reasonable control of pollutant discharge is a key point to prevent water eutrophication and HAB occurrence.     

Kinematics of breaking tsunami wavefronts: A data set from large scale laboratory experiments

This paper provides an overview of a new large scale laboratory data set on the kinematics of breaking tsunami wavefronts. The aim of the experiments was to provide an open access data set for model testing, calibration and verification, with particular emphasis on fluid kinematics in the wave breaking and run-up (swash) zones. The experiments were performed over a composite slope in the tsunami wave basin at the O. H. Hinsdale Wave Research Laboratory at Oregon State University. Data for ten different wave conditions were collected, including non-breaking and breaking waves, and both shore breaks and fully developed long bores.Surface elevation and fluid kinematics were measured with a closely spaced array of surface piercing wave gauges, non-contact ultrasonic wave gauges and four 3-D side-looking Acoustic Doppler Velocimeters. The array was traversed from the nearshore (depth = 0.2 m) to the middle and upper run-up zone, providing kinematic data at 30 cross-shore locations. Video was also recorded from 4 cameras covering the propagation, breaking and run-up zones. Surface elevation, flow velocities and the wave maker displacement were also recorded to provide offshore boundary conditions.The experiments include conditions with wave heights up to 0.55 m, notional wave periods up to 20 s and run-up lengths of up to 15.2 m on a 1/30 slope. In terms of the slope in the shoaling and breaker zones, the data correspond to Iribarren numbers in the range of 0.26–5.6. Raw, calibrated and processed data are stored with open access within the OSU Tsunami Wave Basin Experiment Notebook, which provides full access to all the wave maker control signals, data, instrument coordinates, and processing and plotting software. This paper serves as an introduction to the data set, demonstrates data quality and provides an initial analysis of some key parameters that govern the impact of tsunami events, including run-up versus offshore wave conditions and nearshore bore height, the maximum inundation depths at the original shoreline position, and the time to maximum inundation depth and flow reversal. Examples of temporal and convective accelerations and turbulent flow components are also presented to illustrate further details of the kinematics.     

Database of full-scale laboratory experiments on wave-driven sand transport processes

A new database of laboratory experiments involving sand transport processes over horizontal, mobile sand beds under full-scale non-breaking wave and non-breaking wave-plus-current conditions is described. The database contains details of the flow and bed conditions, information on which quantities were measured and the value of the measured net sand transport rate for 298 experiments conducted in 7 large-scale laboratory facilities. Analysis of the coverage of the experiments and the measured net sand transport rates identified the following gaps in the range of test conditions and/or the type of measurements: (i) graded sand experiments, (ii) wave-plus-current experiments and (iii) intra-wave velocity and concentration measurements in the ripple regime. Furthermore, it highlights two areas requiring further research: (i) the differences in sand transport processes and sand transport rates between real waves and tunnel flows with nominally similar near-bed oscillatory flow conditions and (ii) the effects of acceleration skewness on transport rates. The database is a useful resource for the development and validation of sand transport models for coastal applications.     

A general purpose autonomous transmitter and receiver system forunderwater acoustic experiments

A versatile multifrequency, multi-purpose acoustic transmitter and receiver system has been developed and used to measure low frequency acoustic backscatter from the ocean surface. The instrumentation is general purpose in that all signal and sample parameters are selected by software and a variety of transmission, scattering and reverberation experiments are possible without hardware modification. The system is battery-powered and self-contained for remote and unattended operation for periods of months, depending upon the experimental parameters that affect power and tape consumption. The main features of the system are: a high-powered broadband set of acoustic sources-with center frequencies of 100, 200, 400, and 800 Hz, programmable output signal types, a 64-element vertical hydrophone array, fifty gigabytes of data storage capacity, dynamically-tuneable band pass filters and variable sampling rates, high power microprocessors for in situ signal processing and independent subsystems for recording mooring depth and inclination. The system has been used in surface backscattering experiments at sea and results that demonstrate the capability of the system are presented and discussed     

渤海M2分潮的伴随模式数值实验

根据渤海海域内M2潮汐调和常数的实测值,采用伴随方法来反演出开边界处的潮汐调和常数.为了取得较好的数值模拟结果,同时对给定的底摩擦系数进行了校正并对水深进行了微调.做了4个实验,并分别计算出调和常数的实测值与模拟值之差的绝对平均值:(1)只用19个验潮站的潮汐调和常数;振幅差为2.4cm,迟角差为5.0°.(2)只用37个观测点的高度计资料;振幅差为4.4cm,迟角差为5.7°.(3)同时利用19个验潮站的潮汐调和常数和37个观测点的高度计资料;振幅差为5.5cm,迟角差为8.5°.(4)同时利用19个验潮站的潮汐调和常数和14个观测点的高度计资料;振幅差为3.3cm,迟角差为5.6°.4个实验结果都较好地体现了渤海M₂潮波的特征.     

Managing coastal area resources by stated choice experiments

In many coastal regions, oil spills can be considered as one of the most important and certainly the most noticeable forms of marine pollution. Efficient contingency management responding to oil spills on waters, which aims at minimizing pollution effects on coastal resources, turns out to be critically important. Such a decision making highly depends on the importance attributed to different coastal economic and ecological resources. Economic uses can, in principal, be addressed by standard measures such as value added. However, there is a missing of market in the real world for natural goods. Coastal resources such as waters and beach cannot be directly measured in money terms, which increases the risk of being neglected in a decision making process. This paper evaluates these natural goods of coastal environment in a hypothetical market by employing stated choice experiments. Oil spill management practice in German North Sea is used as an example. Results from a pilot survey show that during a combat process, beach and eider ducks are of key concerns for households. An environmental friendly combat option has to be a minor cost for households. Moreover, households with less children, higher monthly income and a membership of environmental organization are more likely to state that they are willing to pay for combat option to prevent coastal resources from an oil pollution. Despite that choice experiments require knowledge of designing questionnaire and statistical skills to deal with discrete choices and conducting a survey is time consumed, the results have important implications for oil spill contingency management. Overall, such a stated preference method can offer useful information for decision makers to consider coastal resources into a decision making process and can further contribute to finding a cost-effective oil preventive measure, also has a wide application potential in the field of Integrated Coastal Zone Management (ICZM).