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Chen, J.; Yang, J.; Yu, Z., and Tao, R., 2020. Inversion and experimental verification of internal wave parameters. In: Yang, D.F. and Wang, H. (eds.), Recent Advances in Marine Geology and Environmental Oceanography. Journal of Coastal Research, Special Issue No. 108, pp. 200–205. Coconut Creek (Florida), ISSN 0749-0208.It is very important to invert the parameters such as wavelength, amplitude, phase velocity, and group velocity of internal waves to understand their characteristics law of transmission. In this paper, using synthetic aperture radar (SAR) images, the parameters of internal wavelength and direction were inverted based on the normalized Radon transform in the elliptical domain. The parameters of amplitude, phase velocity, and group velocity of internal waves in the Yellow Sea were inverted based on CTD data. Using the measured temperature chain data in the near-sea area, the internal wave group velocity was compared, which verified the accuracy of the inversion algorithm for internal wave parameters in this paper.

Ma, W.; Wang, Y.; Yang, S.; Wang, S., and Xue, Z., 2018. Observation of internal solitary waves using an underwater glider in the northern South China Sea. Internal solitary waves (ISWs) are frequently observed in the ocean, in particular in the South China Sea. Petrel-II, the autonomous underwater glider developed by Tianjin University, conducted ISW observations in the northern South China Sea in August 2017. With the payload conductivity, temperature, and depth, Petrel-II can obtain the repeating thermohaline profiles from the surface to nearly 1500-m depth. Combined with the analysis of a moderate-resolution imaging spectroradiometer true-color image, it is verified that the thermohaline fluctuation is caused by the ISWs. The features of the ISW are estimated by calculation of vertical velocity using a glider flight model. The ISW captured by Profile-46 of the glider was a depression wave, with a period of about 24 minutes and an amplitude of about 127 m. The application of underwater gliders...

Min, E.-H. and Koo, W., 2018. Numerical simulation of wave propagation over structures on a porous seabed. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 966–970. Coconut Creek (Florida), ISSN 0749-0208. A wave-body interaction with semi-circular rigid structures placed on a porous seabed was simulated. Owing to the rigid structures installed at regular intervals, spatial modulation of the wave propagation due to a Bragg reflection was examined. The computational domain consisted of a potential-flow water domain and porous domain with Darcy's law interface boundary condition. Using the numerical wave tank technique, the two-domain boundary element method was developed to simulate wave propagation over seafloor structures on the porous boundary in the time domain. For various permeability constants and incident wave frequencies, wave amplitude was var...

Wang, H.; Zhai, Q.; Hou, J., and Xia, L., 2018. Numerical investigation on the vortex-induced vibration of a flexible plate behind a circular cylinder. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1326–1330. Coconut Creek (Florida), ISSN 0749-0208.Vortex-induced vibration (VIV) of piezoelectric cantilever plate can convert the kinetic energy of flow into electricity effectively, and this technique has become a new research focus in the field of ocean energy harvesting and utilization over the past few years. It is known that the lock-in effect existing in VIV phenomenon can significantly broaden the structural resonance region, and improve the flow energy harvesting efficiency. The present study aims to investigate the VIV responses of a flexible plate located in the wake of a circular cylinder using a strongly coupled finite element model. Numerical simulations are conducted for two typical plate lengths (L/D = 2.0, 4.0; D is the cylinder diameter) within a wide range of gap spacings 0.5 ≤ S/D ≤ 4.0. Generally, the results show that with the increase of gap spacing, the gap flow pattern changes from vortex suppression state to vortex shedding state. For L/D = 2.0, “soft” lock-in occurs all through the examined gap spacing range, among which the plate vibrates with significant amplitude. For L/D = 4.0, the lock-in region is found to be S/D ≤ 2.0, characterized by large-amplitude resonance and vortex suppression in the gap; however, with the appearance of the gap vortex shedding, the vibration becomes negligible at S/D ≥ 2.5. The pressure distribution of fluid along the upper and lower sides of the plate is analyzed to reveal the dynamic coupling mechanism between the flow and plate. This study will provide useful theoretical reference for optimum design of the VIV energy harvesting device.

Peng, W.; Fan, Y., and Zhang, J., 2018. Numerical study on optimization of the float in a shoreline wave energy converter.. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1296–1300. Coconut Creek (Florida), ISSN 0749-0208.In this paper, the hydrodynamic performance of the float in a shoreline wave energy converter is investigated under regular waves. A numerical model is built based on the Navier-Stokes solver coupled with immersed boundary method, volume of fluid method and the mechanics model of float. Making use of the laboratory measurements, the numerical model has been proved to be a reliable tool in reproducing wave deformations and the dynamics of the float. Then, the model is employed to test the sensibility of float performance to changes in some variables under various waves: spacing between breakwater and float, length of float. From numerical estimations, it can be concluded that the nondimensional motion amplitude of float will decrease with the increasing float length or spacing between breakwater and float. With different loads, the dynamic of float shows different variation trend against the length of float, which implies further investigations may be needed in the future on the effect of power take-off damping load. Last but not the least, the interactions between water waves and two types of floats (rectangle and convex) are simulated and discussed. With the help of snapshots of water particle velocity field and the water surface profile from numerical calculation, the flow pattern and external forces from the fluid field acting on the float can be estimated. Then, the motion amplitudes of floats are computed and compared, and the convex floats are proved to capture more power than the rectangular ones.

He, X.; Tang, Y.G.; Liu L.Q., and Zhang, R.Y., 2018. Design of the Mooring System for a Floating Wave Energy Converter. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1351–1355. Coconut Creek (Florida), ISSN 0749-0208.The mooring system is important for a floating wave energy converter since it provides a positioning function and significantly affects the motion characteristics of the wave energy converter. In the present study, a novelty mooring system, which works as a single point mooring assisted with a yaw-restrain system, is proposed. Based on a potential flow theory, a numerical study is carried out. The response amplitudes induced by the wave under different incident angles are presented. The numerical study shows that the incident angle is a key factor of the motion amplitude, and that for each special wavelength, there is an optimal incident angle. A coupled analysis is carried out for the wave energy converter with its mooring system. A controlling method is presented for a given incident angle.

Li, Y. F.; Zhang, H.; Tang, C.; Zou, T., and Jiang, D. J., 2016. Influence of rising sea level on tidal dynamics in the Bohai Sea. Recent studies highlight that tidal propagation in shallow waters tends to be modified with mean sea level rise, intensifying coastal threats. This study aims to obtain a comprehensive insight into the changes in tidal regimes in the Bohai Sea of China in response to local mean sea level rise. To achieve this goal the hydrodynamic model ROMS, previously calibrated and validated for Bohai Sea, was applied, considering local sea level rise scenario of 0.5 m, 1 m, 2 m and 3 m in the future, respectively. The model results show that under sea level rise conditions the amplitude of the main semidiurnal (M2) constituent decreases in most areas except two areas where are around two amphidromic points, and changes in amplitude are not proportional to the level of sea level rise. However, compared results implied that it is necessary to consider the spatial-distribution of sea...

Liang, X. and Ji, H., 2020. Research on friction and impact load response of ship shafting. In: Gong, D.; Zhang, M., and Liu, R. (eds.), Advances in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 106, pp. 514–517. Coconut Creek (Florida), ISSN 0749-0208.With the increase of rotating speed, the vibration speed of impact load increases. The slower, the slower and the faster, the vibration maintenance time is also different. This shows that when the rotation speed of the shaft changes, the oil-film lubrication characteristics of the bearing change, and the oil-film stiffness and oil-film damping of the bearing change, thus showing the support of the sliding bearing. Different from the fixed elastic damping bearing, which is not affected by rotating speed, the oil film dynamically changes its support stiffness and variable damping characteristics. Therefore, when the rotating speed is in the self-excited vibration region of the sliding bearing, the impact time is long, and the amplitude attenuation is slow. When the rotating speed is not in the self-excited vibration region of the bearing, it is in good agreement with the theoretical calculation results.

Qi, X.; Zhang, D.; Guo, H., and Chen, Y., 2020. The fairing arrangement for vortex induced vibration suppression effect in soliton current. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 293–298. Coconut Creek (Florida), ISSN 0749-0208.For oil and gas industry, the riser is an important device connecting the subsea wellhead platform and the production system. Due to its slender nature, it is easily affected by the vortex-induced vibration of the ocean current, which poses a potential danger to the safety of the entire system. Soliton current is a special environmental factor to be considered during riser operation. A faring system have been development and do some test to verify its performance in the previous literature. In this paper, based on the obvious effect for the fairing system to reduce the vortex induced vibration, it has been simulated for the different arrangement for a riser that running under the soliton current. Then it is indicated that cover 57% of the whole length of riser is a cost-effective arrangement suggestion. This arrangement could reduce the transverse Vortex-induced vibration (VIV) response obviously. The maximum ratios of RMS Amplitude divided by External Diameter (A/D) and stress was reduced to 20% compared to the bare one.

Zhou, J.; Wang, H., and Jiang, Z., 2020. Motion and whiplash effect of a floating crane model under wave load: Experiment. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 346–357. Coconut Creek (Florida), ISSN 0749-0208.The top parts of tall terrestrial buildings are sometimes damaged or even destroyed during strong earthquakes because of the whiplash effect. Similarly, the marine floating high-rise multibody structure with a floating base may experience the whiplash effect even more easily, which means that marked motion of the upper part of the structure will occur accompanying minor motion of the floating base under the action of an external load induced by a wave or seismic load. The whiplash effect would threaten the operation and the survival of these offshore high-rise platform structures.In this paper, a physical experiment involving a floating crane without a mooring system under wave loads was set up. The data and results were analyzed and discussed mainly in terms of the motion and the whiplash effect of the floating crane. The whiplash coefficient is defined to estimate the magnitude of the whiplash effect. Some factors, including wave amplitude, wave length, boom angle and boom length, are investigated to determine how they affect the motion and the whiplash effect of the floating crane. Some suggestions are given to control the whiplash effect, and those are useful for the operation of offshore floating platform structures, such as the oil-drill platform, the floating wind farm, the floating crane and some other high-rise marine floating structures.

Huang, J.; Xu, J.; Gao, S.; Lian, X., and Li, J., 2015. Analysis of influence on the Bohai Sea tidal system induced by coastline modification. Four identical hydrodynamic simulation experiments for the Bohai Sea have been implemented respectively with MIKE31 model based on four different coastlines of 2000, 2008, 2010, and 2012, when the intensive usage of the Bohai Sea was carried on. The comparison of these four experiments is used to present the influence on the Bohai Sea tidal system caused by coastline modification. The analysis shows that the semi-diurnal amphidromic point near the Yellow River estuary moves towards south-east gradually as the coastline changes, which makes the semi-diurnal amplitude in Bohai Bay increase and the phase rotate anticlockwise. Meanwhile, the semi-diurnal amplitude in Laizhou Bay becomes smaller and the phase rotates clockwise. Besides, the semi-diurnal amphidromic point near Qinhuang Island moves gradually to southwest. The location of diurnal amphidromic poin...

Zhao, S.; Zhang, J.; Wang, Z.; Huang, H.; Hu, J., and Guo, C., 2020. Improving Scholte-wave vibration signal recognition based on polarization characteristics in coastal waters. Journal of Coastal Research, 36(2), 382–392. Coconut Creek (Florida), ISSN 0749-0208.Scholte waves on the underwater interface provide a lot of information, which can be employed to identify the target in coastal water and speculate the coastal underwater medium. However, as the practical acquired signals are the superposition of multiple wave fields, it is necessary to separate the Scholte wave and to improve its signal-to-noise ratio. The LS-DYNA software was used to simulate the underwater acoustic field to analyze the excitation mechanism and particle trajectory law of Scholte waves and to obtain the propagation characteristic of Scholte waves. The results showed that Scholte waves attenuate according to r–0.5 on the underwater interface and according to exponent in the depth direction. The amplitude of Scholte waves mainly concentrates below 25 Hz, and the corresponding particle trajectory makes a counterclockwise elliptical shape by filtering the acquired signals of particle vibration velocity below 25 Hz on and below the underwater interface. This method was applied to separate Scholte waves from the acquired complex signals of the wave field in the lake experiment to obtain the pure signals of the Scholte wave. This research can provide significant knowledge to better take advantage of resourceful information provided by Scholte waves in the coastal environment.

Jeong, Y.; Kim, D.; Jo, Y.-H.; Kim, D.-W.; Jo, Y.-H., 2019. Interactions of eddies with the Kuroshio Current based on satellite altimeter measurements In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 289-293. Coconut Creek (Florida), ISSN 0749-0208.Ocean eddy is a closed circulation system having a vortex that creates a closed flow. These eddies vary in size from a few centimeters to a few hundreds of kilometers and can lead to changing in sea surface level, sea surface temperature, and nutrient concentration, which can be used to detect eddies using various satellite sensors. Thus, such a vortex plays an important role in the ocean flow in transferring the heat, energy, and the substance inside it. In order to detect eddies objectively in this study, the particle tracking method was used to estimate spatial eddy boundaries using satellite altimeter measurements. This method has an advantage over conventional methods, allowing to detect the eddy's physical boundary changes over the time. Following results were obtained from the understanding the relationship between eddies' evolution and the Kuroshio Current. The cold and warm eddies in two different locations were analyzed to examine the influence of the Western Boundary Current (WBC): Kuroshio Current. Eddies located off the Kuroshio Current revealed that the developmental stages were divided into two stages, and there is a time delay between circular motions and amplitude of eddies. However, eddies located in the Kuroshio Current were divided into three stages of development, and there was a little time delay between circular motions and amplitudes of the eddies. Results of this study suggest that the eddies in the Kuroshio Current were interacted each other through the exchanging the kinetic energy. Although there are some previous researches for analyzing how the ocean current influences to the eddy kinetic energy based on numerical models, there are no investigations based on the actual eddy measurements like this study.

Lu, J. and Zhang, H., 2018. Mechanics analysis of drag reduction in hull motion under wind and waves. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 970–975. Coconut Creek (Florida), ISSN 0749-0208. Taking a large-scale container hull as a numerical simulation object, the computational fluid dynamics (CFD) theory is combined with the super-vacuolar drag reduction technique to reduce the hull boom resistance and total resistance. The hull type line is optimized, the joint drag reduction is carried out to improve the stability of the supercavity, and the SHIPFLOW software is used to simulate the hull resistance. The results show that after the optimization of ship types, because the wave peak change of shipboard is more gentle, viscous resistance is also reduced. Compared with the amplitude of the wave resistance, the change range of the viscous pressure resistance is smaller. The application of supercavita...

Zhang, Y.; Zhang, X.; Yang, L., and Yu, X., 2018. Parameter analysis of dynamic seal of deep-sea motor based on response surface method. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 590–596. Coconut Creek (Florida), ISSN 0749–0208.This paper aims to improve the sealing performance of the dynamic seal used in the deep sea motor via numerical simulations and response surface method (RSM). The contact pressure of the seal for different compression ratio was analyzed, then the pumping effect of Kalsi seal was analyzed, and the leakage rate for the edge region was discussed. On this basis, the relationship between the objective functions and the seal design parameters were established by the second-order polynomial models using 30-group simulation results with four independent seal parameters. The analysis of variance shows that the precision of regression equations of the outer contact pressure and leakage rate is enough. Interaction analysis based on the four parameters and the objective functions also have been discussed. Contrary to the compression ratio and the hardness of the rubber, the amplitude and the number of the wave have minimal effect on contact pressure. However, the leakage rate increases with the increase of the number of wave and the amplitude of the wave, and the effect of the seal compression ratio and the hardness of rubber on the leakage rate is small.

Chen, B. and Li, S.W., 2019. Temporal variation of live-bed pier scour under combined wave-current flow in a large-scale flume. Journal of Coastal Research, 35(2), 348–356. Coconut Creek (Florida), ISSN 0749-0208.Studies on the temporal variation of live-bed scour under waves alone and combined wave-current flow are not as extensive as those under current-alone conditions. Motivated by this, series of experimental tests were carried out in a large-scale flume (5 m wide, 8 m deep, and 450 m long). The scour processes in different locations of the scour hole were monitored simultaneously during the tests. Measured data indicated that the scour depth versus time can be expressed by an exponential equation for both waves-only and combined wave-current conditions. A piecewise equation for predicting the characteristic timescale under combined wave-current flow is proposed based on the data from the literature and the present experiment. In live-bed scour, the effect of wave-generated ripples on scour depth fluctuation could be ignored under waves alone. For the combined wave-current flow, the fluctuation amplitude of scour depth was approximately equal to the height of bed forms under current-dominated conditions and nearly half of the observed height of the bed forms in wave-dominated conditions.

Houston, J.R., and Dean, R.G. 2013. Effects of sea-level decadal variability on acceleration and trend difference. Previous research has shown that sea-level acceleration determined from individual tide gauge records has remarkably large scatter as record lengths decrease due to decadal variations in sea level. We extend previous data sets to the present time and find even greater acceleration scatter. Using analytic solutions, sinusoidal oscillations with amplitudes and periods of typical decadal variations are shown to basically account for the relationship between record length and both acceleration and trend difference. Data show that decadal variations will obscure estimates of underlying accelerations if record lengths of individual gauges are not greater than at least 75 years. Although worldwide data are less affected by decadal variations than individual gauge data, decadal variations still significantly affect estimates of underlying accelerations, in particular for record lengths less ...

White, J.L., 2013. Measuring clast transport signatures at a barrier terminus. At a macrotidal prograding and transgressive, mixed sand and gravel barrier, continuous gravel transport logging provides insights into the relationships between the incident hydrodynamics and the morphodynamics. Two piezoelectric gravel transport sensors (GTS) were aligned in either the cross-shore or the alongshore directions over two low and two moderate energy equinox spring tide events. GTS measure gravel transport as an electronic pulse, where the frequency and amplitude measures clast transport rate and presumably number coincident with the passage of a wave, or per event. Clast transport occurs in bursts characterised by greater than average amplitude peaks, thought to coincide with wave phenomena. Further, these bursts do not appear to progress in a linear relationship with the wave parameters. For example, series of burst can be greater before, or after high tide, and are often polymodal, and low wave energy ...

Lippmann, T. C., J. Irish, and Hunt, J., 2013. Observations of the vertical structure of tidal currents in two inlets. In: Conley, D.C., Masselink, G., Russell, P.E. and O’Hare, T.J. (eds.), Proceedings 12 th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 2029-2034, ISSN 0749-0208. Observations of the vertical structure of broad band tidal currents were obtained at two energetic inlets. Each experiment took place over a 4 week period, the first at Hampton Inlet in southeastern New Hampshire, USA, in the Fall of 2011, and the second at New River Inlet in southern North Carolina, USA, in the spring of 2012. The temporal variation and vertical structure of the currents were observed at each site with 600 kHz and 1200 kHz RDI Acoustic Doppler Current Profilers (ADCP) deployed on low-profile bottom tripods in 7.5 and 12.5 m water depths near the entrance to Hampton Inlet, and in 8 and 9 m water depth within and outside New River Inlet, respectively. In addition, a Nortek Aquapro ADCP was mounted on a jetted pipe in about 2.5 m water depth on the flank of the each inlet channel. Flows within the Hampton/Seabrook Inlet were dominated by semi-diurnal tides ranging 2.5 - 4 m in elevation, with velocities exceeding 2.5 m/s. Flows within New River inlet were also semi-diurnal with tides ranging about 1 – 1.5 m in elevation and with velocities exceeding 1.5 m/s. Vertical variation in the flow structure at the dominant tidal frequency are examined as a function of location within and near the inlet. Outside the inlet, velocities vary strongly over the vertical, with a nearly linear decay from the surface to near the bottom. The coherence between the upper most velocity bin and the successively vertically separated bins drops off quickly with depth, with as much as 50% coherence decay over the water column. The phase relative to the uppermost velocity bin shifts over depth, with as much as 40 deg phase lag over the vertical, with bottom velocities leading the surface. Offshore, rotary coefficients indicate a stable ellipse orientation with rotational directions consistent over the vertical. At Hampton, the shallower ADCP, but still outside the inlet, shows a rotational structure that changes sign in the vertical indicating a sense of rotation at the bottom that is opposite to that at the surface. Within the inlet, the flow is more aligned with the channel, the decay in amplitude over the vertical is diminished, the coherence and phase structure is nearly uniform, and the rotary coefficients indicate no sense of rotation in the flow. The observations are qualitatively consistent with behavior described by Prandle (1982) for shallow water tidal flows.

Ransley, E., Hann, M., Greaves, D., Raby, A. and Simmonds, D., 2013. Numerical and physical modelling of extreme waves at Wave Hub With a history of international failures, the survivability of coupled systems of wave energy devices and their moorings, particularly those to be installed at development sites like Wave Hub, is surrounded by uncertainty. Potential design solutions require a better understanding of the hydrodynamics and structural loading experienced during extreme events, like rogue wave impact, in order to mitigate the risk of device and mooring failure. Rogue waves are waves with amplitudes far greater than those expected, given the surrounding sea conditions. Intense study into these events stems from their potential for catastrophic impact on ocean engineering structures. However, little is known about their physical origins and, currently, there is no consensus on their definition or explanation of the mechanism which drives them. This paper concerns the numerical modeling and ...

Kim, M.S. and Woo, S.B., Eom, H.M., 2013. Propagation of abnormal wave on 25 April 2008 at the West Coast of South Korea On 31 March 2007, abnormal waves suddenly hit the West Coast of South Korea, causing heavy casualties and huge economic loss. Since the cause of wave generation is unknown, we aim to study the direction of wave propagation by investigating the abnormal wave signal recorded in the tidal stations. To determine the propagation direction of abnormal waves, we analyzed tidal level observation data at 1-min intervals, provided by the Korea Hydrographic and Oceanographic Administration (KHOA). To remove tidal components, wavelet decomposition, which filters wave periods ranging from 2 to 60 min, was performed. If the daily maximum amplitude exceeding 95% confidence interval of the total daily maximum amplitudes appeared simultaneously at more than three tidal stations, the day was defined as the day when abnormal waves occurred. Because of nonstationarity and localized peak in the tim...

The generation of tidal asymmetries in estuaries is analyzed by examining the differences in celerity at high and low tide. An analytical expression for the difference between ebb and flood durations is introduced and applied to a cross section composed of a channel flanked by tidal flats. The expression depends on the cross-sectional average of the celerity, for which two approximations are proposed and verified with a numerical model. Results confirm that tidal flats enhance ebb dominance, whereas large tidal amplitudes promote flood dominance. Maximum ebb dominance occurs for tidal flats at or above mean water level, depending on tidal amplitude and the extent of the tidal flats. Finally, qualitative arguments indicate that friction also enhances flood dominance.

The effective roughness of ripple beds under a wave regime is investigated. An existing numerical model, KU-2DVW-00, with a mixing length hypothesis is used to simulate the wave boundary layer flow over ripples. The ripple-length-average bed shear stress or form drag friction is obtained from integration of the computed pressure field. The wave friction factor is generally expressed in terms of the ripple profile shape, the ratio between the amplitude of wave orbital velocity, and the representative amplitude of bed shear stress. The effects of three factors, the bed form shape, orbital velocity amplitude over ripple length, ripple steepness on the wave friction factor or form drag are examined. Three bed profiles were tested. Results show that the drag force at the bed for the sharp-crested arc is much larger than for other shapes. The computed bed friction for the sharp-crested shape is about two times larger than that for the sinusoidal shape. Then, the effective roughness for the sharp-crested ripple becomes about 3 times larger than that for the sinusoidal shape. The model results also show that the effective roughness over ripple height is proportional to the ripple steepness up to a limit, and remains almost constant above the limit.

Wang, Z.; Tang, Y.; Feng, H.; Zhao, Z., and Liu, H., 2017. Model test for lateral soil resistance of partially embedded subsea pipelines on sand during large-amplitude lateral movement. The lateral soil resistance exerted on partially embedded pipes during large-amplitude lateral movement is the key parameter for the analysis of controlled lateral buckling attributable to axial compressive thermal stress. A series of large-scale model tests were performed to investigate the responses of pipe segment with different initial pipe embedment and different pipe weight during large-amplitude lateral movement. The lateral and vertical displacement and lateral soil resistance were measured during the test. The test results showed that breakout resistance and the trajectories of model pipe depend on initial pipe embedment and pipe weight; however, residual resistance is influenced only by pipe weight. In addition, the lateral soil resistance is idealized to two types of the lateral soil-resistance models o...

Bai, X.; Liu, Z.; Li, X.; Chen, Z.; Hu, J.; Sun, Z.; and Zhu, J., 2013. Observations of high-frequency internal waves in the southern Taiwan Strait. Based on in situ hydrographic measurements at a station at about 60 m depth near the local shelf break in July 2011 and a satellite image of the sea-surface roughness, we present the evidence of existence and characteristics of high-frequency internal waves (HIWs) in the southern Taiwan Strait. Variations of the thermohaline structure at the observational site were revealed by repeating conductivity-temperature-depth (CTD) profiling measurements of every 2 hours, while fluctuations of the isothermals due to the passage of HIWs were recorded by continuous CTD measurements with a probe positioned approximately in the middle of the pycnocline. A fast sampling frequency of 8 Hz allows the structure of the HIWs to be captured in great detail. The waves were depression waves, with a period of about 6.2 min and an amplitude of about 25 m. The propagation sp...

International audience; This study deals with the estimation of subtle ground deformation at millimetric accuracy over the broader area of the Mornos River delta in Central Greece and its spatio-temporal distribution for the period between 1992 and 2009 through Persistent Scatterers Interferometry (PSI). The results showed that the majority of the scatterers, which show subsidence, are located within the delta plain with mean subsidence rates throughout the delta varying between -7.2 and +0.7 mm/y. An attempt is made to highlight the geographic distribution, the amplitude, and the causes of the observed delta plain subsidence. The positive correlation between the thickness of the fine-grained Holocene deltaic deposits and the subsidence rates reveals that the main cause is the natural compaction of sediments. The highest subsidence is observed at Bouka Karahassani village, which corresponds to the area of the most recently abandoned river mouth, which is intensely eroded by marine processes. Apart from the dominance of fine sediments in the study area, subsidence may also be attributed to submarine gravitational mass movements along the steep slopes of the prodelta as well as to the reduction of sediment load after the dam construction in 1979. The NW part of the delta seems to have been affected by aseismic slip along a NE-SW trending normal fault buried beneath the alluvial deposits of the Skala torrent fan.

Suastika, K., 2012. Nonlinear-dispersion effects in modeling of blocking of Stokes waves. Effects of amplitude dispersion are investigated in modeling of blocking of Stokes waves in deep water. Modeling results of the wave-amplitude evolution using, respectively, the linear- and Stokes third-order dispersion relation, are compared with experimental data. Two data sets with relatively small-wave steepness are considered because of model restriction to weakly-nonlinear waves. The wave period in Test 1 is 1.1 s and in Test 2 is 1.2 s. The initial-target wave amplitude in still water in Test 1 is 1.0 cm, which is the same as Test 2. It is found that inclusion of amplitude dispersion in the model results in a larger wave-group velocity, as expected, and gives a better fit to the experimental data as compared to the use of the linear-dispersion relation. More specifically, using the Stokes third-order dispersion relation instead of the linear-dispersion relation in the model, the root-mean-squared erro...