Modeling of the propagation of transient waves of moderate steepness

A theoretical approach is applied to predict the propagation and transformation of nonlinear water waves. A semi-analytical solution was derived by applying an eigenfunction expansion method. The solution is applied to analyze the effect of wave frequencies and wave steepness on the propagation of nonlinear waves. The main attention is paid to the wave profile, the wave energy spectrum, and the changes of wave profile and energy spectrum due to the interaction of wave components in a wave train. The results show that for waves of low steepness the nonlinear wave effects and effects associated with the interaction of water waves in a wave train are of secondary importance. For waves of moderate steepness and steep waves the effects associated with the interactions between waves in a wave train are becoming significant and a train of initially sinusoidal waves may drastically change its form within a short distance from its original position. The evolution of wave components has substantial effects on the wave spectrum. A train of initially very narrow-banded waves changes its one-peak spectrum to a multi-peak one in a fairly short period of time. Laboratory experiments were conducted in a wave flume to verify theoretical approaches. The free-surface elevation recorded by a system of wave gauges was compared with the results provided by the semi-analytical solution. Theoretical results are in a fairly good agreement with experimental data. A reasonable agreement between theoretical results and experimental data is observed often even for relatively steep waves.     

Laboratory investigation of damping of gravity-capillary waves on the surface of turbulized liquid

Investigation of damping of gravity-capillary waves (GCWs) in the presence of turbulence is a classical hydrodynamic problem which has important geophysical applications, one of which is related with the problem of forming a radar and optical image of a ship wake on wavy water surface. In this work a new method for the laboratory study of surface wave damping in turbulized liquid is described and the results are presented. The damping of standing GCWs by turbulence on the water surface in a tank mounted on a vibration table is studied. GCWs and turbulence are excited using a two-frequency mode of vibration table oscillations. A high-frequency small amplitude signal is used for parametric GCW excitation; a low-frequency large amplitude signal is used for generating turbulence due to water flowing through a fixed perforated grid submerged into the tank. The coefficient of GCW damping is determined by measured threshold of parametric excitation of the waves; turbulence characteristics are determined by the PIV and PTV techniques. Dependences of GCW damping coefficients on their frequency at different turbulence intensities are obtained, estimates for turbulent viscosity are presented, and a comparison with empirical models proposed earlier is performed.     

Solution of the problem of propagation of water waves over a pair of asymmetrical rectangular trenches

The problem of propagation of obliquely incident surface water waves over a pair of asymmetrical rectangular trenches in a channel of finite depth is examined for its solution. The mathematical problem is handled for its numerical solution with the aid of a system of singular integral equations of first kind. The resulting integral equations are solved numerically by using suitably designed polynomial approximations of the unknown functions. System of linear algebraic equations is obtained by utilizing the zeros of Chebyshev polynomial of first kind as collocation points and hence the occurrence of ill-conditioned matrix is avoided. The effectiveness of the pair of trenches is studied by analyzing the physical quantities namely the reflection and transmission coefficients. As a special limiting case, the results for a single trench problem are derived and are found to be in excellent agreement with the results available in the literature. The effect of various parameters are analyzed through different graphs for a pair of asymmetrical trenches. The energy balance relation is derived and used to check the accuracy of numerical results.     

Statistical analysis of series of dendrochronological indices

We analyze series of tree-ring indices to understand whether they can be indicators of long-term climate changes. We calculated the synchronous cross-correlation coefficients (CCs) for all possible pairs composed of nine series, of which only one CC (for a pair of the longest series) proved to be sufficiently high (0.72). We revealed a time interval for which this CC is equal to 0.88. We failed to locate sufficiently larger time intervals with a higher CC for other pairs of series. Similar calculations for a series using a low-frequency filter (with allowance for periods of 100 or more years) led to a noticeable decrease in almost all CCs. This confirms the statements circulating in the literature that tree-ring chronologies include climate signals with characteristic times of several decades and that the secular and supersecular oscillations are significantly distorted as a result of standardization and cross-linking. The results presented in this paper show that the complex of series being considered cannot be used as a climate-change indicator without an additional analysis. Here, we describe a possible procedure for such analysis. As a result, we found that only two time series at some time subinterval can provide useful information about climate changes.     

Satellite Radiothermovision Analysis of the Evolution of a System of Interacting Typhoons

In this paper we develop further the satellite radiothermovision methods for analyzing the evolution of tropical cyclones. The complicated case of Goni and Atsani interacting typhoons is considered. It has been shown that, although their interaction does not explicitly influence the features of the typhoon trajectories, indications of the formation of complex advective fluxes in the lower troposphere can be revealed from both a qualitative analysis of miscellaneous satellite data and a quantitative estimation of latent heat advection. At the same time, in contrast to the previous works, we had to introduce the integration contours of a complex form (differing from a circular one) into the analysis, so that the energy balance of the typhoon system is correctly described. In a general way, defining such contours is a separate problem whose solution is probably related to the invocation of a large volume of additional satellite information. Due to the peculiarity of the considered case of Goni and Atsani twin typhoons, we demonstrated the effectiveness of a simplified approach that uses a composite contour formed by overlapping two circular ones. Generally, as in the cases previously considered, we found the interrelation between the intensification and dissipation of typhoons (tropical cyclones) and the modes of convergent and divergent advection of latent heat with amplitudes sufficient to support the total power of the system.     

Generation of geostrophic vortices caused by displacements of a part of the bottom of a basin

Within the framework of the general linear statement of the problem, we determine the conditions of generation of a geostrophic current in a layer of uniform rotating fluid for small displacements of the bottom of a basin. We deduce an equation relating the equilibrium shape of the surface of the fluid with residual deformations of the bottom and find its general solution. It is shown that the geostrophic current is generated only in the presence of residual deformations. We present numerical estimates of the intensity of the generated geostrophic formation for a model of motion of the bottom. The investigated mechanism of generation of geostrophic vortex fields is especially efficient in the shelf zone of the ocean. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

全站仪内供电系统的保养

全站仪是由电子经纬仪与光电测距仪组合的仪器,是集自动测距、测角、计算、数据存储及数据传输于一体的自动化、数字化及智能化的三维坐标测量与定位系统,是一种当今广泛应用于大地测量、工程测量、数字化测图的电子测量仪器,是现代测绘行业最主要、最普通的测绘仪器,仪器的维护和供电系统的保养,已经成为测绘生产单位的一项工作。     

Frequency of maxima of non-narrow banded stochastic processes

In many engineering problems one deals with quantities that must be considered to be of a stochastic or random nature. This is true for the natural environment such as wind, waves, and earthquakes, which are the driving mechanism behind the loadings on a wide variety of land-based and offshore structures. From a design perspective it is important to determine the expected highest value of a stochastic process, and structural fatigue life. The relevant procedures are reasonably well established for processes that have narrow band spectra, but it is much less clear how to deal with non-narrow band cases. In this paper it is shown that the extremes of a Gaussian, non-narrow band process are asymptotically equal to the extremes calculated according to the narrow band formula. Also demonstrated is that fatigue estimates may, with good accuracy, be based on the narrow band formula unless the bandwidth becomes extremely large. These statements are illustrated by examples of a process with (1) a low pass box spectrum, and (2) a Pierson–Moskowitz wave amplitude spectrum. It is also shown that the bandwidth parameter may in some cases be counter-intuitive, as the Pierson–Moskowitz spectrum has a larger bandwidth parameter than the box spectrum, even when both cover the same frequency range.     

Long-term variability of the Kuroshio path south of Japan

This study investigates the long-term variability of the Kuroshio path south of Japan. Sensitivity experiments using a data-assimilative model suggest that the duration of the large meander (LM) strongly depends on the Kuroshio transport; specifically, low transport leads to a long duration of the LM. Actually, we find a good correlation between the duration of the past LMs and the Sverdrup transport estimated by a wind-driven linear baroclinic vorticity model. Then we explore favorable conditions for the LM and find a close relationship between the Kuroshio Extension (KE) state and the LM. That is, a precondition for the LM that the Kuroshio path on the Izu Ridge is fixed at a deep channel located around 34°N is achieved during a stable KE state. In addition, westward propagating signals with negative anomalies in the Kuroshio region and high sea-surface height (SSH) state east of Taiwan are key for generation of a small meander southeast of Kyushu that triggers a subsequent LM. The signals related to the above conditions change the upstream Kuroshio transport and velocity, which are consistent with features indicated by the former observational studies. Using reanalysis data, we construct long-time series of indices for the three conditions, which explain well the past LMs. The indices suggest that long-term non-LM states around 1970 and in the 1990s were attributed to a low-SSH state east of Taiwan and an unstable KE state, respectively.     

用直接法分析超大型浮体的水弹性响应

探讨了浮舟桥型超大型浮体结构的水弹性响应分析问题。将超大型浮体结构简化成弹性平板模型,用压力分布法计算流体压力,用直接法计算流体-结构系统,给出了它们的数学计算模型。计算表明本计算方法和程序是正确的,并能保证充分的精度,进而计算了更大尺度的超大型浮体,分析了波长、波向等对响应振幅的影响。     

Introduction of accumulation-dispersal coefficient of marine organisms

Avoiding the subject for fish accumulation, the traditional view in fish population dynamics has ascribed immigration and emigration of fish to dispersal of fish. The main purpose of this paper is to find a quantity that represents the time rate of accumulation-dispersal of marine organisms, and also has some relation to the horizontal convergence of current velocity of the surrounding water. For this, the accumulation-dispersal coefficient is introduced not in the form of diffusion, but in the same form as the convergence. Since the accumulation-dispersal of organisms is a factor that changes its distribution density, all factors causing the change are first classified to locate the position occupied by the accumulation dispersal. Each factor corresponds to each coefficient appearing in a linearized equation describing the rate of change in the density, averaged over a region or a group. The immigration-emigration coefficient is divided into three coefficients of passage, accumulation dispersal and diffusion velocity. For the organisms ranging in a nearly horizontal layer, the accumulation-dispersal coefficient is shown to equal the area-averaged horizontal convergence of organismal velocity relative to land, which is the sum of the area-averaged horizontal convergences of swimming velocity relative to water and of current velocity. However, the area-averaged convergence of current velocity associated with the accumulation-dispersal coefficient for a region is shown to be somewhat different from the usual one.     

1984～2012年海州湾海岸线时空演变研究

以Landsat影像为数据源, 通过改进归一化水体指数、二值化、潮位校正模型提取海岸线, 使用数字海岸线分析系统(Digital Shoreline Analysis System, DSAS), 对1984～2012年海州湾海岸线的时空演变进行了研究。结果表明, 1984～2012年间海州湾海岸线整体以4.29 m/a向海洋推进, 其中, 48%的海岸出现侵蚀, 侵蚀速率为22.83 m/a, 侵蚀现象主要出现在大堤修建前的部分粉砂淤泥质海岸。52%的海岸出现淤积, 淤积速率为25.90 m/a, 淤积现象主要出现在人工海岸、河口海岸和受大堤影响的粉砂淤泥质海岸。海岸线时空演变研究有利于科学地规划、开发和管理海洋及其沿岸空间资源, 并保证其环境及经济的可持续发展。     

Analysis of the variability of hydrological characteristics of the north subpolar front using the model of frontal-trapped baroclinic Rossby waves

Solutions, termed frontal-trapped Rossby waves, have been found for the long-wave equation in a model of a two-layer fluid with the frontal boundary given in the form of an exponential function. Data from a hydrological survey of a subpolar hydrological front in the vicinity of Newfoundland are analysed. A frontal-trapped wave model is shown to describe about 40% of the dispersion of the initial seawater density field. Translated by V. Puchkin.     

A method of estimation of the results of reconstruction of the trajectories of drifting buoys

A method for the estimation of the results of reconstruction of the trajectories of drifting buoys is proposed. It is based on the comparison of the estimates of power spectral densities for the components of current velocity computed according to three data sets: the data set of the coordinates of a drifting buoy with a built-in GPS receiver, the data set of coordinates formed on the basis of the first set but with data missing and observational errors corresponding to the actual trajectory measurements by the Argos satellite location and data collection system by the Doppler method, and the data set of coordinates obtained as a result of interpolation of the second set. As an example, we consider the procedure of realization of the proposed method and demonstrate the efficiency of its application for the improvement of the reliability of reconstruction of the trajectories of drifting buoys.     

Process-based modeling of the overflow-induced growth of erosional channels

A new process-based approach is introduced for a more efficient computation of the overflow-induced growth of an erosional channel in a non-cohesive homogeneous narrow landmass such as the breach growth in a sand-dike. The approach is easy to incorporate in a 1D/2DV morphodynamic model to compute the channel growth both vertically and laterally.     

Detection of cosmogeophysical periodicities by the statistical analysis of intervals between the dates of birth of genetic relatives

A statistical analysis of time intervals between the dates of birth of genetic relatives has been carried out on the basis of 33 family trees. Using the Monte Carlo method, a significant departure of the distribution of birthdays from random results is detected relative to two long-period solar harmonics known from the theory of the Earth tides, i.e., a solar elliptical wave (S _a ) with a period of an anomalistic year (365.259640 days) and a solar declinational wave (S _sa ) with a period of half of the tropical year (182.621095 days). Further research requires larger statistical samples and involves clarifying the effect of long-period lunar harmonics, i.e., an lunar elliptical wave (M _m ) with a period of an anomalistic month (27.554551 days) and a lunar declinational wave (M _f ) with a period of half of a tropical month (13.660791 day), as well as the impact of important lunar and solar tides of time intervals with periods of half (14.765294 days, the interval between syzygial tides at new and full moon) and a whole (29.530588 days) synodic month. It is known that the periodic compression and stretching of the Earth’s crust at the time of the tides by means of the piezoelectric effect lead to the generation of long-period electric oscillations with periods corresponding to the harmonics of the theory of the Earth tides. The detection of these harmonics in connection with biological processes will make it possible to determine the impact of regular cosmogeophysical fluctuations (tidal waves) on the processes in the biosphere.     

Mechanisms of the southward translation of meddies

Meddies are warm and saline anticyclonic eddies found at the mid-depth of the Mediterranean Outflow in the Eastern North Atlantic. They are observed to move almost southward at average speeds as high as 1.3±0.2 cm s⁻¹. This paper examines a mechanism which accelerates this curious translation to a reasonable speed when combined with nonlinearity and a suitable vertical eddy structure. This mechanism is thepseudo-topographic β effect due to the westward decrease in the thickness of the mid-layer induced by the surface southward mean current. The linear dispersion relation including this effect is shown to account for a quarter of the surface southward mean current or a fifth of the observed southward translation of meddies. Three-layer quasi-geostrophic experiments reveal that the surface southward mean current certainly enhances the southward translation velocity of meddies to a speed in agreement with observation, if the meddy has a current structure of plausible intensity and vertical coherence. In the light of the current-induced pseudo-topographic β effect, previous hypotheses are also re-examined through dynamic arguments together with numerical experiments; they are suggested to have some difficulty either in dynamics or in correspondence with observation. Thus the nonlinear effect due to secondary eddies combined with thecurrent-induced pseudo-topographic β effect is the most likely mechanism responsible for the rapid southward translation of meddies among those examined in the paper.     

Numerical Simulation of Dynamic Response of Supple Nets

1 .Introduction Owing to the decline of capture fisheries andsaturation of traditional inshorefarms ,sea cage cul-ture as a newtype of aquaculture is developingrapidlyin China .However ,cage culture is a highriskoperation.The practice is vulnerable to natural hazards ,such as strong tides ,storms and typhoons .So,it is necessaryto assess the behavior of a sea cage exposedto waves and current before the designandinstallation of the structure . Computer simulation,due to its many advantages ,ha…     

Design of mooring system of vessels inside breakwater

A method of simulation calculation for a mooring system of vessels inside a breakwater is illustrated. Using a simulation program based on the above method, a test design for a mooring system for oil-storage vessels of total 5.6 million kiloliters was conducted.In order to obtain data for the simulation program, various experiments, such as wind tunnel tests to test wind resistance, and wave tank tests to test the waves transmitted through or over the breakwater, and the motions of vessels inside the breakwater due to waves, were conducted.Some proposals concerning design criteria and safety factors are presented.Finally, the results of the test design under estimated sea and weather conditions are shown, and the design is concluded to be both technically and economically feasible.     

The effects of reflection coefficient of the harbour sidewall on the performance of floating breakwaters

This paper studies the interaction of linear water waves with a moored floating breakwater with a leeward boundary composed from a vertical wall. This describes a real modelling for the case of ports in contrary to the problems of unbounded domains. It involves the application of a partial reflection boundary condition for this sidewall. In fact, the partial reflection problem in practical application is of great importance in the design of a harbour or breakwater and mainly for short waves. The reflection coefficient of the harbour boundary (sidewall) plays an important role in modifying the performance of the floating breakwater. Moreover, it reduces the resonant peaks appearing inside the ports due to the energy accumulation in an enclosed domain. The effects of the variation of structural parameters of the breakwater on the transmitted wave height are discussed in details for various values of partial reflection.