Wave height

About: Wave height is a research topic. Over the lifetime, 5920 publications have been published within this topic receiving 100257 citations.

Physical processes and sediment flux through reef-lagoon systems

Abstract: Studies of physical processes in reef-lagoon systems continue to emphasize the importance of waves and wave-induced currents at the reef crest as agents of sediment transport to backreef environments. These across-the-reef currents are also largely responsible for driving backreef lagoon circulation. Rapid energy transformations associated with the process of wave breaking at the reef crest are responsible for strong reef-normal surge currents. Estimates of energy loss, as determined by wave height changes caused by wave breaking, can be as high as 70-80%' for discontinuous reefs and >90% for continuous examples. The amount of energy loss is related to depth of water over the reef crest, a function of reef topography and tidal regime. Low-tide conditions promote the greatest incident wave modification and attenuation as a result of increased breaking-wave intensity. Under trade-wind conditions found in the Caribbean, surge currents of 50-80 cm/sec for durations of 2-6 sec are common in a low to moderate wave-energy setting (4-6 sec input waves, 40- 50 cm average heights). Sediments through the sand sizes up to pebbles are easily transported lagoonward by these periodic bursts of energy. Flow in shallow backreef lagoons (generally <3 km wide) is driven largely by across-the-reef currents resulting from breaking waves. Long, unbroken reefs tend to induce axial currents in the backreef lagoon which flow roughly parallel to the reef trend. Side-scan sonographs indicate that large bedforms define a region of bottom sediment migration related to strong currents down the lagoon axis, presumably activated during periods of abnormal wave activity on the reef.

Surge and Wave Modeling for the Louisiana 2012 Coastal Master Plan

Abstract: Cobell, Z.; Zhao, H.; Roberts, H.J.; Clark, F.R., and Zou, S., 2013. Surge and wave modeling for the Louisiana 2012 Coastal Master Plan. The goal of the study was to evaluate various coastal restoration and protection projects and the associated benefits for reductions in storm surge and wave height. Efforts in numerical modeling have been made to create a database of storm surge and wave responses to a set of hypothetical storms under current and various future conditions. The ADvanced CIRCulation (ADCIRC) and the Unstructured Simulating WAves Nearshore (UnSWAN) models were selected for this study. A coarser version of the state-of-the-art, southern Louisiana, unstructured mesh was developed to reduce computational overhead while maintaining critical hydraulic features. Model outputs were reviewed and analyzed from coastwide and onshore-transect points of view. The potential benefits of restoration and protection projects proposed in the Master Plan were examined by comparing Future without Acti...

Remote sensing of wave roller lengths in the laboratory

Abstract: [1] The optical intensity signals from surf zone waves in a laboratory flume are analyzed using several different phase-averaging techniques, and a methodology is developed for estimating wave roller lengths and local wave dissipation The intensity signals (ie, phase-averaged intensity profiles) of individual breaking waves are compared with the wave profiles measured by in situ wave gauges, and the optical signal of the wave roller is shown to ramp up from the toe of the wave roller on the front face of the wave to a maximum intensity at the wave crest The remote sensing observations capture the growth, equilibrium, and decay phases of the roller as it propagates over a fixed bed arranged in a bar/trough morphology Next, for the regular wave conditions considered here, the local maxima of the phase-averaged intensities are shown to better indicate the initial onset of wave breaking and the occurrence of wave breaking in the bar trough, as compared to the more commonly used time-averaged mean intensity In addition, the phase-averaged profiles are used to measure the size of the roller, and these measurements are compared to previous observations of smaller-scale rollers in equilibrium The observed roller lengths are shown to agree with predictions from a wave roller model and to provide a new physical link between the remotely sensed signal and roller dissipation Finally, as an example application of these new data, a simple wave height inversion model is presented that allows an estimation of surf zone wave heights from the remotely sensed roller lengths

Extreme wave events in the central Mediterranean: Geomorphic evidence of tsunami on the Maltese Islands

Abstract: Field evidence from the Maltese Islands is presented of extreme wave activity in the central Mediterranean Sea. An extensive range of extreme wave signatures, both erosional and depositional, is here presented for the first time and indicates a wave attack from the NE. Existing models of runup and boulder detachment imply that the extreme wave signatures lie beyond the capabilities of storm waves. These considerations, taken together with the range of evidence available, point toward tsunami as the agency responsible, which is consistent with the evidence from Mediterranean marginal coasts opposed to the Maltese Islands. Evidence from existing boulder detachment, tsunami runup and wave velocity models suggests that tsunami with shoreline wave height of up to ∼4 m, and with local velocities of >10 ms–1 would have been required in order to form the signatures observed.

Study of an Electromagnetic Ocean Wave Energy Harvester Driven by an Efficient Swing Body Toward the Self-Powered Ocean Buoy Application

Abstract: Ocean wave is one of the promising renewable energy sources all around the world. In this paper, an electromagnetic ocean wave energy harvester (OWEH) based on efficient swing body mechanism is presented. A swing body senses the ultra-low frequency wave motion and drive the rotor of an electromagnetic power module (EPM) rotating at high speed through transmission gears. A series of electromagnetic and dynamic simulations were carried out to optimize the power generation capability of the OWEH. Additionally, the power management circuit is specially designed such that the generated power is able to charge a lithium battery and discharge an external load automatically. The OWEH is installed inside an ocean buoy and tested in the Yellow China Sea. When the peak wave height is greater than 0.6 m, the maximum peak-to-peak output voltage is 15.9 V. The corresponding output power is as high as 0.13 W and the maximum power density is 0.21 mW/cm 3 , where the internal resistance of the OWEH is 122 Ω. Due to the high performance and adaptability, the OWEH can potentially power many low power components, which opens a promising way for improving the life of ocean buoys. Considering the small dimension of 10 × 10 × 6.3 cm 3 , this OWEH can be mounted inside most buoys easily and realize the self-powered ocean buoys in the near future.