scholarly journals SECONDARY WAVES IN COASTAL ZONE: PHYSICAL MECHANISMS OF FORMATION AND POSSIBLE APPLICATION FOR COASTAL PROTECTION

2012 ◽  
Vol 1 (33) ◽  
pp. 12 ◽  
Author(s):  
Sergey Kuznetsov ◽  
Yana Saprykina
Keyword(s):  
Coastal Zone ◽  
Wave Transformation ◽  
Secondary Wave ◽  
Coastal Protection ◽  
Weakly Nonlinear ◽  
Physical Mechanisms ◽  
Advantages And Disadvantages ◽  
Floating Breakwater ◽  
Mechanisms Of Formation ◽  
Underwater Structures

The formation of secondary wave in a coastal zone was investigated on the base of field, laboratory and numerical experiments. It was found that formation of secondary waves is essentially part of weakly nonlinear-dispersive wave transformation and determined by a periodic exchange of energy between the first and second harmonics. The formation of secondary waves depends on a stage of wave transformation and defined by amplitude of secondary harmonic and by phase shift between first and second harmonics. On the base of numerical modeling and laboratory experiments an idea of combination of underwater structures with floating breakwater is investigated. Waves propagating above submerged bar generate secondary waves that decrease the mean period of waves. Each additional bar reinforces and stabilizes this effect. Behind the bars the floating breakwater can be applied, because it suppresses successfully only short waves. Advantages and disadvantages of this idea are discussed.

MODELING AND MONITORING OF THE PROCESSES IN THE COASTAL ZONE OF IMERETINKA LOWLAND, BLACK SEA, SOCHI

2017 ◽  
Author(s):  
Izmail Kantarzhi ◽  
Izmail Kantarzhi ◽  
Mark Zheleznyak ◽  
Mark Zheleznyak ◽  
Igor Leont’yev ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Coastal Zone ◽  
Black Sea ◽  
Transport Model ◽  
Circulation Model ◽  
Wave Transformation ◽  
The Black Sea ◽  
Coastal Processes ◽  
Coastal Protection ◽  
Nearshore Zone

The interest to study the processes in the Imeretinka lowland increases in the last years due the few reasons. The main structures of so-called “coastal cluster” of Olympic Games 2014 built in this area. Some of planned structures effected significantly the coastal processes; they are the seaport near the river Mzimta mouth and coastal protection. The natural coastal processes in the area complicated by the effects of the underwater canyons. The natural-technogenic system requires the study with using the methods of modeling and monitoring. Wave climate of Imeretinka lowland coast estimated based on long-term data of meteorological fields above Black Sea with modeling of wave transformation in nearshore zone by the gentle slope equations. Such approach provides possibilities to assess the effect of the designed coastal protection structures on the changes of the wave parameters in nearshore zone. Numerical modeling of currents in the Black Sea using 3D circulation model with refinement in the region of canyons of the Imeretinka coast obtained. To estimate the sediment transport, 3D Lagrangian multifraction sediment transport model LagrSed is used. 2D flow fields, free-surface level and wave characteristics calculated, using 2D hydrodynamic model of the coastal zone. It has presented the few years story of modeling and monitoring of the coastal processes with the important lessons.

MODELING AND MONITORING OF THE PROCESSES IN THE COASTAL ZONE OF IMERETINKA LOWLAND, BLACK SEA, SOCHI

2017 ◽  
Author(s):  
Izmail Kantarzhi ◽  
Izmail Kantarzhi ◽  
Mark Zheleznyak ◽  
Mark Zheleznyak ◽  
Igor Leont’yev ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Coastal Zone ◽  
Black Sea ◽  
Transport Model ◽  
Circulation Model ◽  
Wave Transformation ◽  
The Black Sea ◽  
Coastal Processes ◽  
Coastal Protection ◽  
Nearshore Zone

The interest to study the processes in the Imeretinka lowland increases in the last years due the few reasons. The main structures of so-called “coastal cluster” of Olympic Games 2014 built in this area. Some of planned structures effected significantly the coastal processes; they are the seaport near the river Mzimta mouth and coastal protection. The natural coastal processes in the area complicated by the effects of the underwater canyons. The natural-technogenic system requires the study with using the methods of modeling and monitoring. Wave climate of Imeretinka lowland coast estimated based on long-term data of meteorological fields above Black Sea with modeling of wave transformation in nearshore zone by the gentle slope equations. Such approach provides possibilities to assess the effect of the designed coastal protection structures on the changes of the wave parameters in nearshore zone. Numerical modeling of currents in the Black Sea using 3D circulation model with refinement in the region of canyons of the Imeretinka coast obtained. To estimate the sediment transport, 3D Lagrangian multifraction sediment transport model LagrSed is used. 2D flow fields, free-surface level and wave characteristics calculated, using 2D hydrodynamic model of the coastal zone. It has presented the few years story of modeling and monitoring of the coastal processes with the important lessons.

THE ROLE OF REMOTE SENSING DATA FOR COASTAL ZONE MONITIORING AND MANAGEMENT (CASE STUDY FOR THE EAST PART OF GULF OF FINLAND)

2017 ◽  
Author(s):  
Nikifor Ostanin ◽  
Nikifor Ostanin
Keyword(s):  
Remote Sensing ◽  
Coastal Zone ◽  
Environmental Changes ◽  
Rapid Development ◽  
Water Environment ◽  
Remote Sensing Data ◽  
Remotely Sensed ◽  
Gulf Of Finland ◽  
Coastal Protection ◽  
Remotely Sensed Data

Coastal zone of the Eastern Gulf of Finland is subjected to essential natural and anthropogenic impact. The processes of abrasion and accumulation are predominant. While some coastal protection structures are old and ruined the problem of monitoring and coastal management is actual. Remotely sensed data is important component of geospatial information for coastal environment research. Rapid development of modern satellite remote sensing techniques and data processing algorithms made this data essential for monitoring and management. Multispectral imagers of modern high resolution satellites make it possible to produce advanced image processing, such as relative water depths estimation, sea-bottom classification and detection of changes in shallow water environment. In the framework of the project of development of new coast protection plan for the Kurortny District of St.-Petersburg a series of archival and modern satellite images were collected and analyzed. As a result several schemes of underwater parts of coastal zone and schemes of relative bathymetry for the key areas were produced. The comparative analysis of multi-temporal images allow us to reveal trends of environmental changes in the study areas. This information, compared with field observations, shows that remotely sensed data is useful and efficient for geospatial planning and development of new coast protection scheme.

scholarly journals PARAMETERIZATION OF EVOLUTION OF BIPHASE DURING NONLINEAR TRANSFORMATION OF WAVES IN COASTAL ZONE

2017 ◽  
pp. 3
Author(s):  
Yana Saprykina ◽  
Sergey Kuznetsov ◽  
Margarita Shtremel
Keyword(s):  
Experimental Data ◽  
Phase Shift ◽  
Coastal Zone ◽  
Energy Exchange ◽  
Wave Motion ◽  
Empirical Relation ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Nonlinear Harmonics ◽  
Sloping Bottom

Based on experimental data, the problem of parametrization of spatial variation of the phase shift (biphase) between the first and second nonlinear harmonics of wave motion during wave transformation over sloping bottom in the coastal zone is discussed. It is revealed that the biphase values vary in the range [–π/2, π/2]. Biphase variations rigorously follow fluctuations in amplitudes of the first and second harmonics and the periodicity of energy exchange between them. The empirical relation applied in modern practice to calculate the biphase, which depends on the Ursell number, is incorrect for calculating the biphase for wave evolution in the coastal zone, because it does not take into account periodic energy exchange between the nonlinear harmonics. The new approximations of the biphase values for typical scenarios of wave transformations are suggested. It was demonstrated that the biphase of breaking waves defines breaking index and breaking type.

scholarly journals Assessment of shoreline positional uncertainty using remote sensing and GIS techniques: A case study from the east coast of India

2021 ◽  
Vol 71 (3) ◽  
pp. 249-263
Author(s):  
Kongeswaran Thangaraj ◽  
Sivakumar Karthikeyan
Keyword(s):  
Linear Regression ◽  
Coastal Zone ◽  
East Coast ◽  
Coastal Zone Management ◽  
Storm Surges ◽  
Shoreline Change ◽  
Coastal Protection ◽  
East Coast Of India ◽  
Zone Management ◽  
2004 Tsunami

The focus of this research was to assess the shoreline changes by comparing the satellite data from 1980 to 2020. The study area falls in the region between Kodiakarai and Nagapattinam of the east coast of India, which has frequently been distressed by storm surges and cyclones in the Bay of Bengal. The Digital Shoreline Analysis System (DSAS) detects and measures the erosional and accretional shoreline positions through the statistics of the Shoreline Change Envelope, Net Shoreline Movement, End Point Rate, Linear Regression Rate, and Weighted Linear Regression. The results show that the shoreline from Kodiakkarai to Nagapattinam suffered severe erosion of 17.7% in total with an average annual erosion rate of 3.4 m/year from 1980 to 2020 and the rate of erosion ranged between 0.1 m/year to 19.8 m/year. About 90.5% of the total shoreline was faced high erosion during the period between 2000 and 2010. The maximum erosion was about 1061 m from 2000 to 2010, the maximum accretion was found to be 1002 m in transects at Kodiakkarai during 2010 to 2020. After the effect of 2004 tsunami, the corresponding changes in littoral currents caused the drastic erosion and accretion in this shoreline. The DSAS prediction model shows that 19.3% of the current shoreline will erode in 2030. The maximum predicted erosion is 406 m at Kodiakkarai and the maximum predicted accretion is 148 m at Nagapattinam region. The coastal zone from Kodiakkarai to Nagapattinam needs special attention to prevent the erosion and it is recommended to build suitable coastal protection structures along the coast for sustainable development and to execute the coastal zone management for this region.

Nonlinear compressible magnetoconvection. Part 3. Travelling waves in a horizontal field

1995 ◽  
Vol 300 ◽  
pp. 287-309 ◽  
Author(s):  
D. P. Brownjohn ◽  
N. E. Hurlburt ◽  
M. R. E. Proctor ◽  
N. O. Weiss
Keyword(s):  
Magnetic Field ◽  
Numerical Experiments ◽  
Strong Field ◽  
Travelling Waves ◽  
Standing Waves ◽  
Weak Field ◽  
Horizontal Magnetic Field ◽  
Weakly Nonlinear ◽  
Physical Mechanisms ◽  
The Magnetic Field

We present results of numerical experiments on two-dimensional compressible convection in a polytropic layer with an imposed horizontal magnetic field. Our aim is to determine how far this geometry favours the occurrence of travelling waves. We therefore delineate the region of parameter space where travelling waves are stable, explore the ways in which they lose stability and investigate the physical mechanisms that are involved. In the magnetically dominated regime (with the plasma beta, $\hat{\beta}$ = 8), convection sets in at an oscillatory bifurcation and travelling waves are preferred to standing waves. Standing waves are stable in the strong-field regime ($\hat{\beta}$ = 32) but travelling waves are again preferred in the intermediate region ($\hat{\beta}$ = 128), as suggested by weakly nonlinear Boussinesq results. In the weak-field regime ($\hat{\beta}$ ≥ 512) the steady nonlinear solution undergoes symmetry-breaking bifurcations that lead to travelling waves and to pulsating waves as the Rayleigh number, $\circ{R}$, is increased. The numerical experiments are interpreted by reference to the bifurcation structure in the ($\hat{\beta}$, $\circ{R}$)-plane, which is dominated by the presence of two multiple (Takens-Bogdanov) bifurcations. Physically, the travelling waves correspond to slow magnetoacoustic modes, which travel along the magnetic field and are convectively excited. We conclude that they are indeed more prevalent when the field is horizontal than when it is vertical.

scholarly journals USING A DYNAMIC APPROACH FOR ZONING THE COAST OF THE SEA OF AZOV

2020 ◽  
Vol 1 (5) ◽  
pp. 207-213
Author(s):  
A.E. Tsygankova ◽  
◽  
L.A. Bespalova ◽  
O.V. Ivlieva ◽  
A.A. Magaeva ◽  
...  
Keyword(s):  
Coastal Zone ◽  
River Flow ◽  
Geological Structure ◽  
Anthropogenic Factors ◽  
Coastal Processes ◽  
Coastal Protection ◽  
Sea Of Azov ◽  
Dynamic Approach ◽  
The Sea Of Azov ◽  
Geological Conditions

The purpose of this work is to comprehensively study the ecological and geological conditions and results of monitoring studies of the coastal territories of the Bay of Taganrog and the Sea of Azov to identify indicators for assessing natural risks. The object of research is a complex system of the coastal zone, consisting of subsystems of land, sea and coast. The subject of the study is the assessment of the risk of loss of territory as a result of various natural factors, both constant over time (geological structure, height of the coastal cliff) and changing (dynamics of the level, waves, wind conditions). Within this framework, we show the use of a dynamic approach for zoning the shores of the Sea of Azov, performed based on a comprehensive analysis of natural and anthropogenic factors that determine the development of dangerous coastal processes (DCP). All factors divided into two groups: those that increase the intensity of coastal processes and those that contribute to reducing their manifestations. It established that hydrodynamic factors in the development of DCP are the determining factors. Anthropogenic impact can be associated with both global and regional impacts, through ecosystem changes, regulation of river flow, environmental pollution, and local – irrational coastal protection, industrial and agricultural activities in the coastal zone, unauthorized removal of beach material, etc.

A Physical Model of Wind Waves in the Coastal Zone

2008 ◽  
Author(s):  
Yana Saprykina ◽  
Natalia Andreeva ◽  
Sergey Kuznetsov ◽  
Zhivelina Cherneva ◽  
C. Guedes Soares
Keyword(s):  
Time Series ◽  
Coastal Zone ◽  
Wind Waves ◽  
Irregular Waves ◽  
Wave Transformation ◽  
Free Surface Elevation ◽  
Space And Time ◽  
Initial Stage ◽  
Instantaneous Values ◽  
The Waves

The variability of the amplitude-frequency structure of wind waves in space and time during their transformation in the coastal zone are considered. Wave time series, measured synchronously in 15 points along the wave propagation, obtained at field and laboratory experiments, were used for the analysis. Free surface elevation time series were represented as a sum of first and second harmonics with amplitudes slowly varying in time (or envelopes of the waves of corresponding frequency bands). Relative changes of these amplitudes in space and time were studied also. It was revealed, that at the initial stage of the wave transformation, the changes of amplitudes of the first and the second harmonics are similar and amplitudes of the second harmonics are proportional to the squared amplitudes of the first harmonics. At this stage the variability of parameters of individual irregular waves can be explained by Stokes theory. Nearer to the coast the instantaneous values of the amplitudes of the first and the second harmonics varies in time chaotically and is not possible to construct a simple model of the variability of the parameters of individual irregular waves. The main reason for this effect is the backward energy transfer from the second to the first harmonics of the waves during nearly resonant non-linear triad interactions.

scholarly journals Coastal protection of the Romanian nearshore throughout hybrid wave and offshore wind farms

2018 ◽  
Vol 51 ◽  
pp. 01004
Author(s):  
Alina Raileanu ◽  
Florin Onea ◽  
Liliana Rusu
Keyword(s):  
Wind Farm ◽  
Wind Farms ◽  
Wave Model ◽  
Reference Points ◽  
Offshore Wind ◽  
Wave Transformation ◽  
The Black Sea ◽  
Coastal Protection ◽  
Offshore Wind Farms ◽  
The Impact

The objective of the present work is to estimate the influence of several hybrid wind and wave farm configurations on the wave conditions reported in the vicinity of the Saint George coastal area, in the Romanian nearshore of the Black Sea. Based on the wave data coming from a climatological database (ERA20C) and also on in situ measurements, it was possible to identify the most relevant wave patterns, which will be further considered for assessment. The numerical simulations were carried out with the SWAN (Simulating Waves Nearshore) wave model, which may provide a comprehensive picture of the wave transformation in the presence of the marine farms. Although the impact of the wind farm is not visible from the spatial maps, from the analysis of the values corresponding to the reference points, it was noticed that a maximum variation of 2% may occur for several wave parameters.

Experimental Identification of the Nonlinear Parameters of an Industrial Translational Guide

2006 ◽  
Author(s):  
Jaspreet Dhupia ◽  
Bartosz Powalka ◽  
A. Galip Ulsoy ◽  
Reuven Katz
Keyword(s):  
Relative Velocity ◽  
Relative Displacement ◽  
Force Function ◽  
Hertzian Contact ◽  
Design Stage ◽  
Restoring Force ◽  
Weakly Nonlinear ◽  
Advantages And Disadvantages ◽  
Nonlinear Restoring Force ◽  
Receptance Coupling

Prediction of machine dynamics at the design stage is a challenge due to lack of adequate methods for identifying and handling the nonlinearities in the machine joints, which appear as the nonlinear restoring force function of relative displacement and relative velocity across the joint. This paper discusses identification of such a nonlinear restoring force function for an industrial translational guide for use with the Nonlinear Receptance Coupling Approach (NLRCA) for evaluating machine dynamic characteristics. Translational guides are among the most commonly used joints in machine tools. Both a parametric and nonparametric technique has been employed to identify the nonlinearities. A novel parametric model based on Hertzian contact mechanics has been derived for the translational guide. This model includes the effect of joint geometry, material properties and preload. A nonparametric method based on two-dimensional Chebyshev polynomials is also used. The models derived from the two techniques, i.e., parametric and nonparametric, are fitted to the experimental data derived from static and dynamic tests to get the restoring force as a function of relative displacement and relative velocity across the joint. The resulting joint model exhibits a weakly nonlinear stiffness term and a viscous damping term. The results from both techniques are compared in the frequency domain. The advantages and disadvantages of parametric and nonparametric techniques are also discussed. The design of experiments for evaluating the nonlinearities in such industrial machine tool joints is a challenge, requiring careful alignment and calibration, because they are typically very stiff. This constrains the dynamic experiments to be carried out at high frequencies (e.g. 2000-7000Hz) where the experimental readings are very sensitive to errors in geometry and calibration.

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