scholarly journals DYNAMIC WAVE SETUP

1988 ◽  
Vol 1 (21) ◽  
pp. 74 ◽  
Author(s):  
Jen-Men Lo
Keyword(s):  
Wave Spectrum ◽  
Low Frequency ◽  
Storm Surges ◽  
Coastal Engineering ◽  
Radiation Stress ◽  
Steady Wave ◽  
Wave Setup ◽  
Engineering Problems ◽  
Stress Term ◽  
Dynamic Wave

The wave setup for a given wave spectrum was re-evaluated with the radiation stress term including the low-frequency terms. This setup which is referred to here as "dynamic wave setup", was compared with the steady setup, which is generated by including only the non-periodic radiation stress terms. The results of the study showed that the dynamic wave setup is greater than the steady wave setup, sometimes almost double its value. Therefore, the dynamic wave setup is important for engineering applications, particularly in the study of storm surges and coastal engineering problems.

scholarly journals CURRENTS IN TIDAL FLATS DURING STORM SURGES

1976 ◽  
Vol 1 (15) ◽  
pp. 56
Author(s):  
Harald Gohren
Keyword(s):  
Tidal Flat ◽  
High Tide ◽  
Storm Surges ◽  
Water Layer ◽  
Tidal Flats ◽  
Coastal Engineering ◽  
Sand Transport ◽  
Engineering Problems ◽  
Aerial View ◽  
Strong Winds

Wind action in the viewpoint of coastal engineering is mainly a topic for discussions or investigations of waves, breakers, storm surges, sand transport on beaches and so on. Offshore currents, generated by wind shear stress concern more the scientific field of oceanographers. But in shallow coastal water wind induced drift currents indeed may be important for coastal engineering problems, as sediment transport, sewage spreading, salinity and so on. For example, along the German North Sea Coast (Fig. 1) we have a rim of extended tidal flats, built up by sand and mud and covered only by a water layer of 1 to 2 m at high tide. At low tide sands and mud flats fall dry. Fig. 2, an aerial view, gives an impression of a typical tidal flat, the "Neuwerker Watt" at the south side of the Elbe Estuary. The distance between main land and the sea side border of the flat is here about 20 km. A lot of investigations have been carried out here - initiated by a harbour planning task - giving some interesting results about currents in the tidal flat area during strong winds and storm surges. For the current measurements a recording current meter (Fig. 3) has been used, fixed at a tripod aluminum frame in 40 cm above bottom. The propeller meter starts at velocities of 5 cm/s. Tests in a flume proved that orbital currents give no disturbance if unidirectional currents of a certain magnitude are superimposed.

scholarly journals An Analytical Method for Dynamic Wave-Related Errors of Interferometric SAR Ocean Altimetry under Multiple Sea States

2021 ◽  
Vol 13 (5) ◽  
pp. 986
Author(s):  
Yao Chen ◽  
Mo Huang ◽  
Yuanyuan Zhang ◽  
Changyuan Wang ◽  
Tao Duan
Keyword(s):  
Electromagnetic Scattering ◽  
Analytical Method ◽  
Wave Spectrum ◽  
High Accuracy ◽  
Sea State ◽  
Error Budget ◽  
Ocean Topography ◽  
Mean Square Errors ◽  
Dynamic Wave ◽  
Wide Swath

The spaceborne interferometric synthetic aperture radar (InSAR) is expected to measure the sea surface height (SSH) with high accuracy over a wide swath. Since centimeter-level accuracy is required to monitor the ocean sub-mesoscale dynamics, the high accuracy implies that the altimetric errors should be totally understood and strictly controlled. However, for the dynamic waves, they move randomly all the time, and this will lead to significant altimetric errors. This study proposes an analytical method for the dynamic wave-related errors of InSAR SSH measurement based on the wave spectrum and electromagnetic scattering model. Additionally, the mechanisms of the dynamic wave-related errors of InSAR altimetry are analyzed, and the detailed numerical model is derived. The proposed analytical method is validated with NASA’s Surface Water and Ocean Topography (SWOT) project error budget, and the Root-Mean-Square Errors (RMSEs) are in good agreement (0.2486 and 0.2470 cm on a 0.5 km2 grid, respectively). Instead of analysis for a typical project, the proposed method can be applied to different radar parameters under multiple sea states. The RMSEs of Ka-band under low sea state, moderate sea state, and high sea state are 0.2670, 1.3154, and 6.6361 cm, respectively. Moreover, the RMSEs of X-band and Ku-band are also simulated and presented. The experimental results demonstrate that the dynamic wave-related errors of InSAR altimetry are not sensitive to the frequencies but are sensitive to the sea states. The error compensation method is necessary for moderate and higher sea states for centimetric accuracy requirements. This can provide feasible suggestions on system design and error budget for the future interferometric wide-swath altimeter.

The Study of the Impact for Coastal Engineering on High Water Level Induced by Storm Surges in Bohai Bay

2011 ◽  
Vol 94-96 ◽  
pp. 810-814
Author(s):  
Jin Shan Zhang ◽  
Wei Sheng Zhang ◽  
Chen Cheng ◽  
Lin Yun Sun
Keyword(s):  
Water Level ◽  
Storm Surge ◽  
Large Scale ◽  
Storm Surges ◽  
High Water ◽  
Coastal Engineering ◽  
Cold Wave ◽  
Bohai Bay ◽  
Ocean Engineering ◽  
The Impact

Bohai Bay is an semi-closed bay, the storm surge disaster is very serious in past. Now more and more large ocean engineering are built here, To study changes of storm surge induced by the construction of large-scale coastal engineering in Bohai Bay in present, 2D numerical storm surge model is established with large - medium - small model nested approach. The three most typical storms surges: 9216, 9711 and by cold wave in October 2003 are simulated in the condition of before and after implementation of planning projects in Bohai Bay. Changes of storm surge water level due to implementation of artificial projects are analysis in this paper.

scholarly journals Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation

2020 ◽  
Vol 8 (2) ◽  
pp. 63
Author(s):  
Nils B. Kerpen ◽  
Karl-Friedrich Daemrich ◽  
Oliver Lojek ◽  
Torsten Schlurmann
Keyword(s):  
Water Level ◽  
Wave Spectrum ◽  
Water Environment ◽  
Physical Modelling ◽  
Storm Surges ◽  
Water Levels ◽  
Coastal Protection ◽  
Wave Steepness ◽  
Wave Overtopping

The wave overtopping discharge at coastal defense structures is directly linked to the freeboard height. By means of physical modelling, experiments on wave overtopping volumes at sloped coastal structures are customarily determined for constant water levels and static wave steepness conditions (e.g., specific wave spectrum). These experiments are the basis for the formulation of empirically derived and widely acknowledged wave overtopping estimations for practical design purposes. By analysis and laboratory reproduction of typical features from exemplarily regarded real storm surge time series in German coastal waters, the role of non-stationary water level and wave steepness were analyzed and adjusted in experiments. The robustness of wave overtopping estimation formulae (i.e., the capabilities and limitations of such a static projection of dynamic boundary conditions) are outlined. Therefore, the classic static approach is contrasted with data stemming from tests in which both water level and wave steepness were dynamically altered in representative arrangements. The analysis reveals that mean overtopping discharges for simple sloping structures in an almost deep water environment could be robustly estimated for dynamic water level changes by means of the present design formulae. In contrast, the role of dynamic changes of the wave steepness led to a substantial discrepancy of overtopping volumes by a factor of two. This finding opens new discussion on methodology and criteria design of coastal protection infrastructure under dynamic exposure to storm surges and in lieu of alterations stemming from projected sea level rise.

scholarly journals On the non-linear energy transfer in a gravity-wave spectrum. Part 3. Evaluation of the energy flux and swell-sea interaction for a Neumann spectrum

1963 ◽  
Vol 15 (3) ◽  
pp. 385-398 ◽  
Author(s):  
K. Hasselmann
Keyword(s):  
Energy Transfer ◽  
Gravity Wave ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Low Frequencies ◽  
Frequency Peak ◽  
Non Linear ◽  
Gain Energy ◽  
Rate Of Decay ◽  
Linear Interactions

The energy transfer due to non-linear interactions between the components of a gravity-wave spectrum discussed in Parts 1 and 2 of this paper is evaluated for a fully and partially developed Neumann spectrum with various spreading factors. The characteristic time scales of the energy transfer are found to be typically of the order of a few hours. In all cases the high frequencies and the low-frequency peak are found to gain energy from an intermediate range of frequencies. The transfer of energy to very low frequencies and to waves travelling at large angles to the main propagation direction of the spectrum is negligible. Computations are presented also for the rate of decay of swell interacting with local wind-generated seas (represented by a Neumann spectrum). An appreciable decay is found only for swell frequencies in the same range as those of the local sea.

Low Frequency Wave Forces and Wave Induced Motions of a FPSO in Shallow Water

2007 ◽  
Author(s):  
Longfei Xiao ◽  
Jianmin Yang ◽  
Zhiqiang Hu
Keyword(s):  
Shallow Water ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Wave Force ◽  
Wave Forces ◽  
Frequency Wave ◽  
Wave Basin ◽  
The Difference ◽  
The One ◽  
Wave Induced

The low frequency (LF) response of a soft yoke moored 160kDWT FPSO in shallow water is investigated by conducting frequency domain computations and wave basin model tests. An incident wave with Hs = 4.1m and Tp = 8.9s is applied. An obvious LF part appears in the measured wave spectrum at water depth of 16.7m. As a result, the 1st order LF wave force exists and is much larger than the 2nd one. The difference of the spectrums is about one hundred times. The LF wave drift force increases enormously. Consequently, much larger resonant surge response is induced. The LF surge amplitude at h = 16.7m is about 7 times the one at h = 29.0m and 9 times the one in deep water, although the 2nd order response changes a little. Therefore, in very shallow water, LF part of incident waves should be taken into account carefully and LF wave forces and wave induced motions will be very serious.

Smoothed Particle Hydrodynamics for coastal engineering problems

2013 ◽  
Vol 120 ◽  
pp. 96-106 ◽  
Author(s):  
A. Barreiro ◽  
A.J.C. Crespo ◽  
J.M. Domínguez ◽  
M. Gómez-Gesteira
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Coastal Engineering ◽  
Engineering Problems ◽  
Particle Hydrodynamics ◽  
Smoothed Particle
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