The Fate and Impact of Internal Waves in Nearshore Ecosystems.

PubMed

Woodson, C B

2018-01-03

Internal waves are widespread features of global oceans that play critical roles in mixing and thermohaline circulation. Similarly to surface waves, internal waves can travel long distances, ultimately breaking along continental margins. These breaking waves can transport deep ocean water and associated constituents (nutrients, larvae, and acidic low-oxygen waters) onto the shelf and locally enhance turbulence and mixing, with important effects on nearshore ecosystems. We are only beginning to understand the role internal waves play in shaping nearshore ecosystems. Here, I review the physics of internal waves in shallow waters and identify two commonalities among internal waves in the nearshore: exposure to deep offshore waters and enhanced turbulence and mixing. I relate these phenomena to important ecosystem processes ranging from extreme events to fertilization success to draw general conclusions about the influence of internal waves on ecosystems and the effects of internal waves in a changing climate.

Effect of transient wave forcing on the behavior of arsenic in a sandy nearshore aquifer

NASA Astrophysics Data System (ADS)

Rakhimbekova, S.; O'Carroll, D. M.; Robinson, C. E.

2016-12-01

Waves cause large quantities of coastal water to recirculate across the groundwater-coastal water interface in addition to inducing complex groundwater flows in the nearshore aquifer. Due to the distinct chemical composition of recirculating coastal water compared with discharging terrestrial groundwater, wave-induced recirculations and flows can alter geochemical gradients in the nearshore aquifer which may subsequently affect the mobilization and transport of reactive pollutants (e.g., arsenic). The impact of seasonal geochemical and hydrological variability on the occurrence and mobility of arsenic near the groundwater-surface water interface has been shown previously in riverine settings, however, the impact of high frequency geochemical variations (e.g., varying wave conditions) on arsenic mobility in groundwater-surface water environments is unclear. The objective of the study was to assess the impact of intensified wave conditions on the behavior of arsenic in a nearshore aquifer to determine the factors regulating its mobility and transport to receiving coastal waters. Field investigations were conducted at a permeable beach on the Great Lakes during a period of intensified wave conditions (wave event). High spatial resolution pore water sampling captured the geochemical conditions in the nearshore aquifer prior to the wave event, immediately after the wave event and over a recovery period of 3 weeks following the wave event. Shifts in pH and redox potential (ORP) gradients in response to varying wave conditions caused shifts in the iron and arsenic distributions in the aquifer. Sediment analysis was combined with the pore water distributions to assess the release of sediment-bound arsenic in response to the varying wave conditions. Insight into the effect of transient forcing on arsenic mobility and transport in groundwater-surface water environments is important for evaluating the potential risks associated with this toxic metalloid. The findings of this study also have significant implications for the fate of other reactive constituents (heavy metals, nutrients) discharging through nearshore aquifers to coastal waters.

The nonlinear Schrödinger equation and the propagation of weakly nonlinear waves in optical fibers and on the water surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chabchoub, A., E-mail: achabchoub@swin.edu.au; Kibler, B.; Finot, C.

2015-10-15

The dynamics of waves in weakly nonlinear dispersive media can be described by the nonlinear Schrödinger equation (NLSE). An important feature of the equation is that it can be derived in a number of different physical contexts; therefore, analogies between different fields, such as for example fiber optics, water waves, plasma waves and Bose–Einstein condensates, can be established. Here, we investigate the similarities between wave propagation in optical Kerr media and water waves. In particular, we discuss the modulation instability (MI) in both media. In analogy to the water wave problem, we derive for Kerr-media the Benjamin–Feir index, i.e. amore » nondimensional parameter related to the probability of formation of rogue waves in incoherent wave trains.« less

Generalized analytical model for benthic water flux forced by surface gravity waves

USGS Publications Warehouse

King, J.N.; Mehta, A.J.; Dean, R.G.

2009-01-01

A generalized analytical model for benthic water flux forced by linear surface gravity waves over a series of layered hydrogeologic units is developed by adapting a previous solution for a hydrogeologic unit with an infinite thickness (Case I) to a unit with a finite thickness (Case II) and to a dual-unit system (Case III). The model compares favorably with laboratory observations. The amplitude of wave-forced benthic water flux is shown to be directly proportional to the amplitude of the wave, the permeability of the hydrogeologic unit, and the wave number and inversely proportional to the kinematic viscosity of water. A dimensionless amplitude parameter is introduced and shown to reach a maximum where the product of water depth and the wave number is 1.2. Submarine groundwater discharge (SGD) is a benthic water discharge flux to a marine water body. The Case I model estimates an 11.5-cm/d SGD forced by a wave with a 1 s period and 5-cm amplitude in water that is 0.5-m deep. As this wave propagates into a region with a 0.3-m-thick hydrogeologic unit, with a no-flow bottom boundary, the Case II model estimates a 9.7-cm/d wave-forced SGD. As this wave propagates into a region with a 0.2-m-thick hydrogeologic unit over an infinitely thick, more permeable unit, the Case III quasi-confined model estimates a 15.7-cm/d wave-forced SGD. The quasi-confined model has benthic constituent flux implications in coral reef, karst, and clastic regions. Waves may undermine tracer and seepage meter estimates of SGD at some locations. Copyright 2009 by the American Geophysical Union.

Measurement and imaging of infragravity waves in sea ice using InSAR

NASA Astrophysics Data System (ADS)

Mahoney, Andrew R.; Dammann, Dyre O.; Johnson, Mark A.; Eicken, Hajo; Meyer, Franz J.

2016-06-01

Using short-temporal baseline interferometric synthetic aperture radar, we capture instantaneous images of a persistent field of infragravity waves propagating through sea ice near Barrow, Alaska, during January 2015. We estimate wave amplitudes to be between 1.2 and 1.8 mm. Curvature of wavefronts is consistent with refraction of waves entering shallow water from a source region north of Barrow. A shallow water wave model indicates that the geometry of the wavefronts is relatively insensitive to the source location, but other evidence suggests the waves may have originated in the North Atlantic, making this perhaps the longest observed propagation path for waves through ice. We also note that steepening of the waves entering shallow water can increase the peak strain by an order of magnitude, suggesting that infragravity waves may play a role in determining the location of the landfast ice edge with respect to water depth.

Capturing the flow beneath water waves.

PubMed

Nachbin, A; Ribeiro-Junior, R

2018-01-28

Recently, the authors presented two numerical studies for capturing the flow structure beneath water waves (Nachbin and Ribeiro-Junior 2014 Disc. Cont. Dyn. Syst. A 34 , 3135-3153 (doi:10.3934/dcds.2014.34.3135); Ribeiro-Junior et al. 2017 J. Fluid Mech. 812 , 792-814 (doi:10.1017/jfm.2016.820)). Closed orbits for irrotational waves with an opposing current and stagnation points for rotational waves were some of the issues addressed. This paper summarizes the numerical strategies adopted for capturing the flow beneath irrotational and rotational water waves. It also presents new preliminary results for particle trajectories, due to irrotational waves, in the presence of a bottom topography.This article is part of the theme issue 'Nonlinear water waves'. © 2017 The Author(s).

Effect of current on spectrum of breaking waves in water of finite depth

NASA Technical Reports Server (NTRS)

Tung, C. C.; Huang, N. E.

1987-01-01

This paper presents an approximate method to compute the mean value, the mean square value and the spectrum of waves in water of finite depth taking into account the effect of wave breaking with or without the presence of current. It is assumed that there exists a linear and Gaussian ideal wave train whose spectrum is first obtained using the wave energy flux balance equation without considering wave breaking. The Miche wave breaking criterion for waves in finite water depth is used to limit the wave elevation and establish an expression for the breaking wave elevation in terms of the elevation and its second time derivative of the ideal waves. Simple expressions for the mean value, the mean square value and the spectrum are obtained. These results are applied to the case in which a deep water unidirectional wave train, propagating normally towards a straight shoreline over gently varying sea bottom of parallel and straight contours, encounters an adverse steady current whose velocity is assumed to be uniformly distributed with depth. Numerical results are obtained and presented in graphical form.

Local amplification of seismic waves from the Denali earthquake and damaging seiches in Lake Union, Seattle, Washington

USGS Publications Warehouse

Barberopoulou, A.; Qamar, A.; Pratt, T.L.; Creager, K.C.; Steele, W.P.

2004-01-01

The Mw7.9 Denali, Alaska earthquake of 3 November, 2002, caused minor damage to at least 20 houseboats in Seattle, Washington by initiating water waves in Lake Union. These water waves were likely initiated during the large amplitude seismic surface waves from this earthquake. Maps of spectral amplification recorded during the Denali earthquake on the Pacific Northwest Seismic Network (PNSN) strong-motion instruments show substantially increased shear and surface wave amplitudes coincident with the Seattle sedimentary basin. Because Lake Union is situated on the Seattle basin, the size of the water waves may have been increased by local amplification of the seismic waves by the basin. Complete hazard assessments require understanding the causes of these water waves during future earthquakes. Copyright 2004 by the American Geophysical Union.

BAROMETRIC AND WATER-SURFACE WAVES PRODUCED BY MIKE SHOT

DTIC Science & Technology

Barometric and water -surface waves generated by Mike shot were studied by means of 25 instruments in 19 locations in the Pacific Basin ranging from...on the tops of two mounts. The first water waves arriving at Eniwetok Island apparently traveled along paths outside the lagoon. At several of the...stations there were two distinct arrivals of water waves, the first apparently being driven by the propagated rise in atmospheric pressure caused by the

Parameter Governing of Wave Resonance in Water Chamber and Its Application

NASA Astrophysics Data System (ADS)

Husain, F.; Alie, M. Z. M.; Rahman, T.

2018-04-01

It has become known that the oscillating water column (OWC) device is very popular as one of wave energy extraction facilities installed in coastal and ocean structures. However, it has not been clarified sufficiently how to obtain an effective cross section design of the structure until now. This paper describes theoretical procedure to yield effective cross section of water chamber type of sea wall, which is similar to the OWC type structure in relation to wave period or wave length. The water chamber type sea wall has a water chamber partitioned by a curtain wall installed in front of part of the structure. This type of sea wall also can be applied to extract wave power same as of OWC function. When the wave conditions on site are known, the dimensions especially the breadth of water chamber type sea wall can be determined.

Numerical Simulations of Laminar Air-Water Flow of a Non-linear Progressive Wave at Low Wind Speed

NASA Astrophysics Data System (ADS)

Wen, X.; Mobbs, S.

2014-03-01

A numerical simulation for two-dimensional laminar air-water flow of a non-linear progressive water wave with large steepness is performed when the background wind speed varies from zero to the wave phase speed. It is revealed that in the water the difference between the analytical solution of potential flow and numerical solution of viscous flow is very small, indicating that both solutions of the potential flow and viscous flow describe the water wave very accurately. In the air the solutions of potential and viscous flows are very different due to the effects of viscosity. The velocity distribution in the airflow is strongly influenced by the background wind speed and it is found that three wind speeds, , (the maximum orbital velocity of a water wave), and (the wave phase speed), are important in distinguishing different features of the flow patterns.

Explicit use of the Biot coefficient in predicting shear-wave velocity of water-saturated sediments

USGS Publications Warehouse

Lee, M.W.

2006-01-01

Predicting the shear-wave (S-wave) velocity is important in seismic modelling, amplitude analysis with offset, and other exploration and engineering applications. Under the low-frequency approximation, the classical Biot-Gassmann theory relates the Biot coefficient to the bulk modulus of water-saturated sediments. If the Biot coefficient under in situ conditions can be estimated, the shear modulus or the S-wave velocity can be calculated. The Biot coefficient derived from the compressional-wave (P-wave) velocity of water-saturated sediments often differs from and is less than that estimated from the S-wave velocity, owing to the interactions between the pore fluid and the grain contacts. By correcting the Biot coefficients derived from P-wave velocities of water-saturated sediments measured at various differential pressures, an accurate method of predicting S-wave velocities is proposed. Numerical results indicate that the predicted S-wave velocities for consolidated and unconsolidated sediments agreewell with measured velocities. ?? 2006 European Association of Geoscientists & Engineers.

An Experimental Study on the Impact of Different-frequency Elastic Waves on Water Retention Curve

NASA Astrophysics Data System (ADS)

Deng, J. H.; Dai, J. Y.; Lee, J. W.; Lo, W. C.

2017-12-01

ABSTEACTOver the past few decades, theoretical and experimental studies on the connection between elastic wave attributes and the physical properties of a fluid-bearing porous medium have attracted the attention of many scholars in fields of porous medium flow and hydrogeology. It has been previously determined that the transmission of elastic waves in a porous medium containing two immiscible fluids will have an effect on the water retention curve, but it has not been found that the water retention curve will be affected by the frequency of elastic vibration waves or whether the effect on the soil is temporary or permanent. This research is based on a sand box test in which the soil is divided into three layers (a lower, middle, and upper layer). In this case, we discuss different impacts on the water retention curve during the drying process under sound waves (elastic waves) subject to three frequencies (150Hz, 300Hz, and 450Hz), respectively. The change in the water retention curve before and after the effect is then discussed. In addition, how sound waves affect the water retention curve at different depths is also observed. According to the experimental results, we discover that sound waves can cause soil either to expand or to contract. When the soil is induced to expand due to sound waves, it can contract naturally and return to the condition it was in before the influence of the sound waves. On the contrary, when the soil is induced to contract, it is unable to return to its initial condition. Due to the results discussed above, it is suggested that sound waves causing soil to expand have a temporary impact while those causing soil to contract have a permanent impact. In addition, our experimental results show how sound waves affect the water retention curve at different depths. The degree of soil expansion and contraction caused by the sound waves will differ at various soil depths. Nevertheless, the expanding or contracting of soil is only subject to the frequency of sound waves. Key words: Elastic waves, Water retention curve, Sand box test.

Guided wave propagation in metallic and resin plates loaded with water on single surface

NASA Astrophysics Data System (ADS)

Hayashi, Takahiro; Inoue, Daisuke

2016-02-01

Our previous papers reported dispersion curves for leaky Lamb waves in a water-loaded plate and wave structures for several typical modes including quasi-Scholte waves [1,2]. The calculations were carried out with a semi-analytical finite element (SAFE) method developed for leaky Lamb waves. This study presents SAFE calculations for transient guided waves including time-domain waveforms and animations of wave propagation in metallic and resin water-loaded plates. The results show that non-dispersive and non-attenuated waves propagating along the interface between the fluid and the plate are expected for effective non-destructive evaluation of such fluid-loaded plates as storage tanks and transportation pipes. We calculated transient waves in both steel and polyvinyl chloride (PVC) plates loaded with water on a single side and input dynamic loading from a point source on the other water-free surface as typical examples of metallic and resin plates. For a steel plate, there exists a non-dispersive and non-attenuated mode, called the quasi-Scholte wave, having an almost identical phase velocity to that of water. The quasi-Scholte wave has superior generation efficiency in the low frequency range due to its broad energy distribution across the plate, whereas it is localized near the plate-water interface at higher frequencies. This means that it has superior detectability of inner defects. For a PVC plate, plural non-attenuated modes exist. One of the non-attenuated modes similar to the A0 mode of the Lamb wave in the form of a group velocity dispersion curve is promising for the non-destructive evaluation of the PVC plate because it provides prominent characteristics of generation efficiency and low dispersion.

Turbulence and wave breaking effects on air-water gas exchange

PubMed

Boettcher; Fineberg; Lathrop

2000-08-28

We present an experimental characterization of the effects of turbulence and breaking gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration rates: turbulent transport when no wave breaking occurs and bubble dominated transport when wave breaking occurs. In both regimes, we correlate the qualitative changes in the aeration rate with corresponding changes in the wave dynamics. In the latter regime, the strongly enhanced aeration rate is correlated with measured acoustic emissions, indicating that bubble creation and dynamics dominate air-water exchange.

Laboratory study of spectral waves over a muddy bottom

NASA Astrophysics Data System (ADS)

Maxeiner, E.; Dalrymple, R. A.

2010-12-01

The attenuation of water waves propagating over a muddy ocean floor has been studied extensively both analytically and experimentally over the past 30 years. Possible mechanisms for this include surface wave interactions with the bottom, surface wave interactions with waves formed at the water/mud interface (lutocline) and shear instability at the water/mud interface. Typically these studies have focused on monochromatic waves. Observations of wave attenuation in the field, however, are subject to a spectrum of wave frequencies and sizes. A few field studies (Sheremet and Stone, 2003; Elgar and Raubenheimer, 2008) have explored the possible effects that a wide spectrum of wave frequencies may have on wave damping mechanisms. In this study, the wave attenuation exhibited by a sea spectrum over a muddy bottom is studied experimentally in a laboratory for the first time. Using an 18 m-long wave tank at the Coastal Engineering Laboratory at Johns Hopkins University, a piston-style wave maker is used to create both monochromatic and spectral waves. A 10 m-long section of the tank floor incorporates a recessed layer of kaolinite clay which subsequently mixes with the overlying water in the presence of waves. Testing consists of three phases. First, a series of monochromatic wave trains are produced over a range of wave frequencies and in a range of water depths to assess the damping behavior with respect to a variety of parameters such as wave frequency, wave height and water depth. Damping is assessed by comparing wave height at various longitudinal locations in the tank. Second, “wave beats” are created by superimposing waves of two frequencies to create a longer envelope. Third, the wave maker is used to generate a representative random sea condition, based on the Pierson-Moskowitz sea spectrum. For this type of testing, damping is assessed by measuring wave energy flux over a period of time at various longitudinal locations in the tank. Spectral analysis is also performed at these locations to track changing spectral energy, as previous studies have hypothesized mechanisms of energy transfer between waves of different frequencies. This study is part of a Multidisciplinary University Research Initiative (MURI), which includes on computational, laboratory and field studies of wave damping in nearshore areas of the Gulf of Mexico along the coast of Louisiana.

Development of an Extratropical Storm Wind, Wave, and Water Level Climatology for the Offshore Mid-Atlantic

DTIC Science & Technology

2015-08-01

ER D C/ CH L TR -1 5- 11 Development of an Extratropical Storm Wind, Wave, and Water Level Climatology for the Offshore Mid-Atlantic...Development of an Extratropical Storm Wind, Wave, and Water Level Climatology for the Offshore Mid-Atlantic Michael F. Forte Field Research Facility...standards for offshore wind farm design and to establish a 100-year (yr) extratropical wind speed, wave height, and water level climatology for the

Liquid-surface entrainment induced by shocked air stream

NASA Astrophysics Data System (ADS)

Rodriguez, V.; Jourdan, G.; Marty, A.; Allou, A.; Parisse, J.-D.

2018-02-01

Recently, we experimentally studied, in a shock tube environment, shock waves propagating over horizontal free water layers having depths of 10, 20, and 30 mm for shock wave Mach numbers M_is equal to 1.1 and 1.4. The qualitative interaction process was observed by means of high-speed visualizations, and the pressures arising in the air and in the water layer were measured and interpreted in terms of the various incident and refracted shock waves in air and water; in particular, it was concluded that the compression wave in the water is driven by the planar shock wave in the air. Additional experiments have been conducted and the novel contributions of the present technical note are quantitative results regarding the liquid-surface entrainment. At low Mach number (M_is=1.1 ), we show that the velocity of the droplets ejected into the air is independent of the water depth, unlike the wavelength of initial ripples and the angle of ejection. When the shock wave strength increases (M_is=1.4 ), the dispersion of a very thin droplet mist and a single large wave take place. We show that the thickening of the water mist and the velocity of the subsequent large wave decreases with the water-layer depth.

Resonant generation of internal waves on the soft sea bed by a surface water wave

NASA Astrophysics Data System (ADS)

Wen, Feng

1995-08-01

The nonlinear response of an initially flat sea bed to a monochromatic surface progressive wave was studied using the multiple scale perturbation method. Two opposite-traveling subliminal internal ``mud'' waves are selectively excited and form a resonant triad with the surface wave. The amplitudes of the internal waves grow on a time scale much longer than the period of the surface wave. It was found that the sea bed response is critically dependent on the density ratio of water and soil, depth of water, and depth and viscosity of the saturated soil. The result of instability analysis is in qualitative agreement with the result of a wave flume experiment.

Novel two-way artificial boundary condition for 2D vertical water wave propagation modelled with Radial-Basis-Function Collocation Method

NASA Astrophysics Data System (ADS)

Mueller, A.

2018-04-01

A new transparent artificial boundary condition for the two-dimensional (vertical) (2DV) free surface water wave propagation modelled using the meshless Radial-Basis-Function Collocation Method (RBFCM) as boundary-only solution is derived. The two-way artificial boundary condition (2wABC) works as pure incidence, pure radiation and as combined incidence/radiation BC. In this work the 2wABC is applied to harmonic linear water waves; its performance is tested against the analytical solution for wave propagation over horizontal sea bottom, standing and partially standing wave as well as wave interference of waves with different periods.

Effects of sea water on elongated duration of ground motion as well as variation in its amplitude for offshore earthquakes

NASA Astrophysics Data System (ADS)

Todoriki, Masaru; Furumura, Takashi; Maeda, Takuto

2017-01-01

We investigated the effects of sea water on the propagation of seismic waves using a 3-D finite-difference-method simulation of seismic wave propagation following offshore earthquakes. When using a 1-D layered structure, the simulation results showed strong S- to P-wave conversion at the sea bottom; accordingly, S-wave energy was dramatically decreased by the sea water layer. This sea water de-amplification effect had strong frequency dependence, therefore resembling a low-pass filter in which the cut-off frequency and damping coefficients were defined by the thickness of the sea water layer. The sea water also acted to elongate the duration of Rayleigh wave packet. The importance of the sea water layer in modelling offshore earthquakes was further demonstrated by a simulation using a realistic 3-D velocity structure model with and without sea water for a shallow (h = 14 km) outer-rise Nankai Trough event, the 2004 SE Off Kii Peninsula earthquake (Mw = 7.2). Synthetic seismograms generated by the model when sea water was included were in accordance with observed seismograms for long-term longer period motions, particularly those in the shape of Rayleigh waves.

Run-up parameterization and beach vulnerability assessment on a barrier island: a downscaling approach

NASA Astrophysics Data System (ADS)

Medellín, G.; Brinkkemper, J. A.; Torres-Freyermuth, A.; Appendini, C. M.; Mendoza, E. T.; Salles, P.

2016-01-01

We present a downscaling approach for the study of wave-induced extreme water levels at a location on a barrier island in Yucatán (Mexico). Wave information from a 30-year wave hindcast is validated with in situ measurements at 8 m water depth. The maximum dissimilarity algorithm is employed for the selection of 600 representative cases, encompassing different combinations of wave characteristics and tidal level. The selected cases are propagated from 8 m water depth to the shore using the coupling of a third-generation wave model and a phase-resolving non-hydrostatic nonlinear shallow-water equation model. Extreme wave run-up, R2%, is estimated for the simulated cases and can be further employed to reconstruct the 30-year time series using an interpolation algorithm. Downscaling results show run-up saturation during more energetic wave conditions and modulation owing to tides. The latter suggests that the R2% can be parameterized using a hyperbolic-like formulation with dependency on both wave height and tidal level. The new parametric formulation is in agreement with the downscaling results (r2 = 0.78), allowing a fast calculation of wave-induced extreme water levels at this location. Finally, an assessment of beach vulnerability to wave-induced extreme water levels is conducted at the study area by employing the two approaches (reconstruction/parameterization) and a storm impact scale. The 30-year extreme water level hindcast allows the calculation of beach vulnerability as a function of return periods. It is shown that the downscaling-derived parameterization provides reasonable results as compared with the numerical approach. This methodology can be extended to other locations and can be further improved by incorporating the storm surge contributions to the extreme water level.

AN EXPERIMENTAL STUDY OF SHOCK WAVES RESULTING FROM THE IMPACT OF HIGH VELOCITY MISSILES ON ANIMAL TISSUES

PubMed Central

Harvey, E. Newton; McMillen, J. Howard

1947-01-01

The spark shadowgram method of studying shock waves is described. It has been used to investigate the properties of such waves produced by the impact of a high velocity missile on the surface of water. The method can be adapted for study of behavior of shock waves in tissue by placing the tissue on a water surface or immersing it in water. Spark shadowgrams then reveal waves passing from tissue to water or reflected from tissue surfaces. Reflection and transmission of shock waves from muscle, liver, stomach, and intestinal wall are compared with reflection from non-living surfaces such as gelatin gel, steel, plexiglas, cork, and air. Because of its heterogeneous structure, waves transmitted by tissue are dispersed and appear as a series of wavelets. When the accoustical impedance (density x wave velocity) of a medium is less than that in which the wave is moving, reflection will occur with inversion of the wave; i.e., a high pressure wave will become a low pressure wave. This inversion occurs at an air surface and is illustrated by shadowgrams of reflection from stomach wall, from a segment of colon filled with gas, and from air-filled rubber balloons. Bone (human skull and beef ribs) shows good reflection and some transmission of shock waves. When steel is directly hit by a missile, clearly visible elastic waves pass from metal to water, but a similar direct hit on bone does not result in elastic waves strong enough to be detected by a spark shadowgram. PMID:19871617

Mountain waves modulate the water vapor distribution in the UTLS

NASA Astrophysics Data System (ADS)

Heller, Romy; Voigt, Christiane; Beaton, Stuart; Dörnbrack, Andreas; Giez, Andreas; Kaufmann, Stefan; Mallaun, Christian; Schlager, Hans; Wagner, Johannes; Young, Kate; Rapp, Markus

2017-12-01

The water vapor distribution in the upper troposphere-lower stratosphere (UTLS) region has a strong impact on the atmospheric radiation budget. Transport and mixing processes on different scales mainly determine the water vapor concentration in the UTLS. Here, we investigate the effect of mountain waves on the vertical transport and mixing of water vapor. For this purpose we analyze measurements of water vapor and meteorological parameters recorded by the DLR Falcon and NSF/NCAR Gulfstream V research aircraft taken during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) in New Zealand. By combining different methods, we develop a new approach to quantify location, direction and irreversibility of the water vapor transport during a strong mountain wave event on 4 July 2014. A large positive vertical water vapor flux is detected above the Southern Alps extending from the troposphere to the stratosphere in the altitude range between 7.7 and 13.0 km. Wavelet analysis for the 8.9 km altitude level shows that the enhanced upward water vapor transport above the mountains is caused by mountain waves with horizontal wavelengths between 22 and 60 km. A downward transport of water vapor with 22 km wavelength is observed in the lee-side of the mountain ridge. While it is a priori not clear whether the observed fluxes are irreversible, low Richardson numbers derived from dropsonde data indicate enhanced turbulence in the tropopause region related to the mountain wave event. Together with the analysis of the water vapor to ozone correlation, we find indications for vertical transport followed by irreversible mixing of water vapor. For our case study, we further estimate greater than 1 W m-2 radiative forcing by the increased water vapor concentrations in the UTLS above the Southern Alps of New Zealand, resulting from mountain waves relative to unperturbed conditions. Hence, mountain waves have a great potential to affect the water vapor distribution in the UTLS. Our regional study may motivate further investigations of the global effects of mountain waves on the UTLS water vapor distributions and its radiative effects.

Silicone-Based Triboelectric Nanogenerator for Water Wave Energy Harvesting.

PubMed

Xiao, Tian Xiao; Jiang, Tao; Zhu, Jian Xiong; Liang, Xi; Xu, Liang; Shao, Jia Jia; Zhang, Chun Lei; Wang, Jie; Wang, Zhong Lin

2018-01-31

Triboelectric nanogenerator (TENG) has been proven to be efficient for harvesting water wave energy, which is one of the most promising renewable energy sources. In this work, a TENG with a silicone rubber/carbon black composite electrode was designed for converting the water wave energy into electricity. The silicone-based electrode with a soft texture provides a better contact with the dielectric film. Furthermore, a spring structure is introduced to transform low-frequency water wave motions into high-frequency vibrations. They together improve the output performance and efficiency of TENG. The output performances of TENGs are further enhanced by optimizing the triboelectric material pair and tribo-surface area. A spring-assisted TENG device with the segmented silicone rubber-based electrode structure was sealed into a waterproof box, which delivers a maximum power density of 2.40 W m -3 , as triggered by the water waves. The present work provides a new strategy for fabricating high-performance TENG devices by coupling flexible electrodes and spring structure for harvesting water wave energy.

Singularities in water waves and Rayleigh-Taylor instability

NASA Technical Reports Server (NTRS)

Tanveer, S.

1991-01-01

Singularities in inviscid two-dimensional finite-amplitude water waves and inviscid Rayleigh-Taylor instability are discussed. For the deep water gravity waves of permanent form, through a combination of analytical and numerical methods, results describing the precise form, number, and location of singularities in the unphysical domain as the wave height is increased are presented. It is shown how the information on the singularity in the unphysical region has the same form as for deep water waves. However, associated with such a singularity is a series of image singularities at increasing distances from the physical plane with possibly different behavior. Furthermore, for the Rayleigh-Taylor problem of motion of fluid over a vacuum and for the unsteady water wave problem, integro-differential equations valid in the unphysical region are derived, and how these equations can give information on the nature of singularities for arbitrary initial conditions is shown.

Strait of Gibraltar as seen from STS-58

NASA Image and Video Library

1993-10-20

STS058-73-009 (18 Oct-1 Nov 1993) --- Atlantic water flowing with the tide through the Strait of Gibraltar into the Mediterranean generates internal waves as depicted in this photo. The incoming cool, less dense Atlantic water flows over the warm, more saline Mediterranean water. As the tide moves into the Strait of Gibraltar it encounters the Camarinal Sill, which is like a cliff under water, south of Camarinal Point, Spain. Internal waves are generated at the Sill and travel along the density boundary between the Atlantic water and the Mediterranean water. Internal waves have very little effect on the sea surface, except for gentle slopes and slight differences in roughness. We can see them in the Space Shuttle photos because of sunglint which reflects off the water. Internal waves smooth out some of the capillary waves at the surface in bands. The sun reflects more brightly from these smooth areas showing us the pattern of the underwater waves. The Bay of Cadiz on the southwest coast of Spain, the Rock of Gibraltar, and the Moroccan coast are also visible in this photo.

WAVECALC: an Excel-VBA spreadsheet to model the characteristics of fully developed waves and their influence on bottom sediments in different water depths

NASA Astrophysics Data System (ADS)

Le Roux, Jacobus P.; Demirbilek, Zeki; Brodalka, Marysia; Flemming, Burghard W.

2010-10-01

The generation and growth of waves in deep water is controlled by winds blowing over the sea surface. In fully developed sea states, where winds and waves are in equilibrium, wave parameters may be calculated directly from the wind velocity. We provide an Excel spreadsheet to compute the wave period, length, height and celerity, as well as horizontal and vertical particle velocities for any water depth, bottom slope, and distance below the reference water level. The wave profile and propagation can also be visualized for any water depth, modeling the sea surface change from sinusoidal to trochoidal and finally cnoidal profiles into shallow water. Bedload entrainment is estimated under both the wave crest and the trough, using the horizontal water particle velocity at the top of the boundary layer. The calculations are programmed in an Excel file called WAVECALC, which is available online to authorized users. Although many of the recently published formulas are based on theoretical arguments, the values agree well with several existing theories and limited field and laboratory observations. WAVECALC is a user-friendly program intended for sedimentologists, coastal engineers and oceanographers, as well as marine ecologists and biologists. It provides a rapid means to calculate many wave characteristics required in coastal and shallow marine studies, and can also serve as an educational tool.

Tsunamis generated by subaerial mass flows

USGS Publications Warehouse

Walder, S.J.; Watts, P.; Sorensen, O.E.; Janssen, K.

2003-01-01

Tsunamis generated in lakes and reservoirs by subaerial mass flows pose distinctive problems for hazards assessment because the domain of interest is commonly the "near field," beyond the zone of complex splashing but close enough to the source that wave propagation effects are not predominant. Scaling analysis of the equations governing water wave propagation shows that near-field wave amplitude and wavelength should depend on certain measures of mass flow dynamics and volume. The scaling analysis motivates a successful collapse (in dimensionless space) of data from two distinct sets of experiments with solid block "wave makers." To first order, wave amplitude/water depth is a simple function of the ratio of dimensionless wave maker travel time to dimensionless wave maker volume per unit width. Wave amplitude data from previous laboratory investigations with both rigid and deformable wave makers follow the same trend in dimensionless parameter space as our own data. The characteristic wavelength/water depth for all our experiments is simply proportional to dimensionless wave maker travel time, which is itself given approximately by a simple function of wave maker length/water depth. Wave maker shape and rigidity do not otherwise influence wave features. Application of the amplitude scaling relation to several historical events yields "predicted" near-field wave amplitudes in reasonable agreement with measurements and observations. Together, the scaling relations for near-field amplitude, wavelength, and submerged travel time provide key inputs necessary for computational wave propagation and hazards assessment.

Novel wave generator adaptable to indoor surfboarding

NASA Technical Reports Server (NTRS)

Heidmann, M. F.; Phillips, B. R.

1970-01-01

Method is devised for generating strong acoustic waves in confined body of water. Strong travelling acoustic waves or modes are created by rotation of radial jet of gas at center of short cylindrical chamber. Method and wave structure suggest novel facility for water sports.

Modeling Water Waves with Smoothed Particle Hydrodynamics

DTIC Science & Technology

2013-09-30

SPH Model for Water Waves and Other Free Surface Flows ...Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes...proving to be a competent modeling scheme for free surface flows in three dimensions including the complex flows of the surf zone. As the GPU

Development of wave and surge atlases for the design and protection of coastal bridges in South Louisiana.

DOT National Transportation Integrated Search

2011-05-01

The objectives of this proposed research are to: 1. Develop a 100-year design. a. maximum water surface elevation and associated wave height, b. maximum wave height and associated water elevation atlases for South Louisiana coastal waters. 2. Obtain ...

Highly Adaptive Solid-Liquid Interfacing Triboelectric Nanogenerator for Harvesting Diverse Water Wave Energy.

PubMed

Zhao, Xue Jiao; Kuang, Shuang Yang; Wang, Zhong Lin; Zhu, Guang

2018-05-22

Harvesting water wave energy presents a significantly practical route to energy supply for self-powered wireless sensing networks. Here we report a networked integrated triboelectric nanogenerator (NI-TENG) as a highly adaptive means of harvesting energy from interfacing interactions with various types of water waves. Having an arrayed networking structure, the NI-TENG can accommodate diverse water wave motions and generate stable electric output regardless of how random the water wave is. Nanoscaled surface morphology consisting of dense nanowire arrays is the key for obtaining high electric output. A NI-TENG having an area of 100 × 70 mm 2 can produce a stable short-circuit current of 13.5 μA and corresponding electric power of 1.03 mW at a water wave height of 12 cm. This merit promises practical applications of the NI-TENG in real circumstances, where water waves are highly variable and unpredictable. After energy storage, the generated electric energy can drive wireless sensing by autonomously transmitting data at a period less than 1 min. This work proposes a viable solution for powering individual standalone nodes in a wireless sensor network. Potential applications include but are not limited to long-term environment monitoring, marine surveillance, and off-shore navigation.

Effect of higher order nonlinearity, directionality and finite water depth on wave statistics: Comparison of field data and numerical simulations

NASA Astrophysics Data System (ADS)

Fernández, Leandro; Monbaliu, Jaak; Onorato, Miguel; Toffoli, Alessandro

2014-05-01

This research is focused on the study of nonlinear evolution of irregular wave fields in water of arbitrary depth by comparing field measurements and numerical simulations.It is now well accepted that modulational instability, known as one of the main mechanisms for the formation of rogue waves, induces strong departures from Gaussian statistics. However, whereas non-Gaussian properties are remarkable when wave fields follow one direction of propagation over an infinite water depth, wave statistics only weakly deviate from Gaussianity when waves spread over a range of different directions. Over finite water depth, furthermore, wave instability attenuates overall and eventually vanishes for relative water depths as low as kh=1.36 (where k is the wavenumber of the dominant waves and h the water depth). Recent experimental results, nonetheless, seem to indicate that oblique perturbations are capable of triggering and sustaining modulational instability even if kh<1.36. In this regard, the aim of this research is to understand whether the combined effect of directionality and finite water depth has a significant effect on wave statistics and particularly on the occurrence of extremes. For this purpose, numerical experiments have been performed solving the Euler equation of motion with the Higher Order Spectral Method (HOSM) and compared with data of short crested wave fields for different sea states observed at the Lake George (Australia). A comparative analysis of the statistical properties (i.e. density function of the surface elevation and its statistical moments skewness and kurtosis) between simulations and in-situ data provides a confrontation between the numerical developments and real observations in field conditions.

Topological helical edge states in water waves over a topographical bottom

NASA Astrophysics Data System (ADS)

Wu, Shiqiao; Wu, Ying; Mei, Jun

2018-02-01

We present the discovery of topologically protected helical edge states in water wave systems, which are realized in water wave propagating over a topographical bottom whose height is modulated periodically in a two-dimensional triangular pattern. We develop an effective Hamiltonian to characterize the dispersion relation and use spin Chern numbers to classify the topology. Through full-wave simulations we unambiguously demonstrate the robustness of the helical edge states which are immune to defects and disorders so that the backscattering loss is significantly reduced. A spin splitter is designed for water wave systems, where helical edge states with different spin orientations are spatially separated with each other, and potential applications are discussed.

Experimental Investigation of the Properties of an Acoustic Wave Induced by Laser Ablation of a Solid Target in Water-Confined Plasma Propulsion

NASA Astrophysics Data System (ADS)

Zheng, Zhiyuan; Gao, Hua; Gao, Lu; Xing, Jie

2014-11-01

Acoustic waves generated in nanosecond pulsed-laser ablation of a solid target in both air and water-confined environments were measured experimentally. It was found that the amplitude of the acoustic wave tended to decrease with an increase in water thickness. The waves were analyzed by means of fast Fourier transform. It was shown that there are several frequency components in the acoustic waves with the dominant frequency shifting from high frequency to low frequency as the thickness of the water layer increases. Furthermore, strong acoustic pressure led to enhancement of the coupling of the laser energy to the target in laser plasma propulsion.

Influences on water-hammer wave shape: an experimental study

NASA Astrophysics Data System (ADS)

Traudt, T.; Bombardieri, C.; Manfletti, C.

2016-09-01

Water-hammer phenomena are of strong interest in a number of different industrial fields, amongst which the space industry. Here the priming of feedlines during start-up of an engine as well as the rapid closing of valves upon shutdown may lead to pressure peaks symptomatic of a water-hammer wave. Test benches used to conduct tests on future as well as current engines are also sensitive to water-hammer waves traveling along their feedlines. To enhance the understanding of water-hammer, we investigated different configurations and their influence on the wave shape in the frequency domain. The configurations feature a coiled pipe setup with a support structure and without a support structure. Two other phenomena will be presented. We found a beat phenomenon which is likely to be the so called Poisson-coupling beat. Finally we will show that the second water-hammer peak can reach pressures a lot higher than the first peak by additive interference of the primary and secondary water-hammer wave.

Theoretical monochromatic-wave-induced currents in intermediate water with viscosity and nonzero mass transport

NASA Technical Reports Server (NTRS)

Talay, T. A.

1975-01-01

Wave-induced mass-transport current theories with both zero and nonzero net mass (or volume) transport of the water column are reviewed. A relationship based on the Longuet-Higgens theory is derived for wave-induced, nonzero mass-transport currents in intermediate water depths for a viscous fluid. The relationship is in a form useful for experimental applications; therefore, some design criteria for experimental wave-tank tests are also presented. Sample parametric cases for typical wave-tank conditions and a typical ocean swell were assessed by using the relation in conjunction with an equation developed by Unluata and Mei for the maximum wave-induced volume transport. Calculations indicate that substantial changes in the wave-induced mass-transport current profiles may exist dependent upon the assumed net volume transport. A maximum volume transport, corresponding to an infinite channel or idealized ocean condition, produces the largest wave-induced mass-transport currents. These calculations suggest that wave-induced mass-transport currents may have considerable effects on pollution and suspended-sediments transport as well as buoy drift, the surface and midlayer water-column currents caused by waves increasing with increasing net volume transports. Some of these effects are discussed.

Numerical simulation of multi-directional random wave transformation in a yacht port

NASA Astrophysics Data System (ADS)

Ji, Qiaoling; Dong, Sheng; Zhao, Xizeng; Zhang, Guowei

2012-09-01

This paper extends a prediction model for multi-directional random wave transformation based on an energy balance equation by Mase with the consideration of wave shoaling, refraction, diffraction, reflection and breaking. This numerical model is improved by 1) introducing Wen's frequency spectrum and Mitsuyasu's directional function, which are more suitable to the coastal area of China; 2) considering energy dissipation caused by bottom friction, which ensures more accurate results for large-scale and shallow water areas; 3) taking into account a non-linear dispersion relation. Predictions using the extended wave model are carried out to study the feasibility of constructing the Ai Hua yacht port in Qingdao, China, with a comparison between two port layouts in design. Wave fields inside the port for different incident wave directions, water levels and return periods are simulated, and then two kinds of parameters are calculated to evaluate the wave conditions for the two layouts. Analyses show that Layout I is better than Layout II. Calculation results also show that the harbor will be calm for different wave directions under the design water level. On the contrary, the wave conditions do not wholly meet the requirements of a yacht port for ship berthing under the extreme water level. For safety consideration, the elevation of the breakwater might need to be properly increased to prevent wave overtopping under such water level. The extended numerical simulation model may provide an effective approach to computing wave heights in a harbor.

Assessing the performance of wave breaking parameterizations in shallow waters in spectral wave models

NASA Astrophysics Data System (ADS)

Lin, Shangfei; Sheng, Jinyu

2017-12-01

Depth-induced wave breaking is the primary dissipation mechanism for ocean surface waves in shallow waters. Different parametrizations were developed for parameterizing depth-induced wave breaking process in ocean surface wave models. The performance of six commonly-used parameterizations in simulating significant wave heights (SWHs) is assessed in this study. The main differences between these six parameterizations are representations of the breaker index and the fraction of breaking waves. Laboratory and field observations consisting of 882 cases from 14 sources of published observational data are used in the assessment. We demonstrate that the six parameterizations have reasonable performance in parameterizing depth-induced wave breaking in shallow waters, but with their own limitations and drawbacks. The widely-used parameterization suggested by Battjes and Janssen (1978, BJ78) has a drawback of underpredicting the SWHs in the locally-generated wave conditions and overpredicting in the remotely-generated wave conditions over flat bottoms. The drawback of BJ78 was addressed by a parameterization suggested by Salmon et al. (2015, SA15). But SA15 had relatively larger errors in SWHs over sloping bottoms than BJ78. We follow SA15 and propose a new parameterization with a dependence of the breaker index on the normalized water depth in deep waters similar to SA15. In shallow waters, the breaker index of the new parameterization has a nonlinear dependence on the local bottom slope rather than the linear dependence used in SA15. Overall, this new parameterization has the best performance with an average scatter index of ∼8.2% in comparison with the three best performing existing parameterizations with the average scatter index between 9.2% and 13.6%.

Linear shoaling of free-surface waves in multi-layer non-hydrostatic models

NASA Astrophysics Data System (ADS)

Bai, Yefei; Cheung, Kwok Fai

2018-01-01

The capability to describe shoaling over sloping bottom is fundamental to modeling of coastal wave transformation. The linear shoaling gradient provides a metric to measure this property in non-hydrostatic models with layer-integrated formulations. The governing equations in Boussinesq form facilitate derivation of the linear shoaling gradient, which is in the form of a [ 2 P + 2 , 2 P ] expansion of the water depth parameter kd with P equal to 1 for a one-layer model and (4 N - 4) for an N-layer model. The expansion reproduces the analytical solution from Airy wave theory at the shallow water limit and maintains a reasonable approximation up to kd = 1.2 and 2 for the one and two-layer models. Additional layers provide rapid and monotonic convergence of the shoaling gradient into deep water. Numerical experiments of wave propagation over a plane slope illustrate manifestation of the shoaling errors through the transformation processes from deep to shallow water. Even though outside the zone of active wave transformation, shoaling errors from deep to intermediate water are cumulative to produce appreciable impact to the wave amplitude in shallow water.

Charging System Optimization of Triboelectric Nanogenerator for Water Wave Energy Harvesting and Storage.

PubMed

Yao, Yanyan; Jiang, Tao; Zhang, Limin; Chen, Xiangyu; Gao, Zhenliang; Wang, Zhong Lin

2016-08-24

Ocean waves are one of the most promising renewable energy sources for large-scope applications due to the abundant water resources on the earth. Triboelectric nanogenerator (TENG) technology could provide a new strategy for water wave energy harvesting. In this work, we investigated the charging characteristics of utilizing a wavy-structured TENG to charge a capacitor under direct water wave impact and under enclosed ball collision, by combination of theoretical calculations and experimental studies. The analytical equations of the charging characteristics were theoretically derived for the two cases, and they were calculated for various load capacitances, cycle numbers, and structural parameters such as compression deformation depth and ball size or mass. Under the direct water wave impact, the stored energy and maximum energy storage efficiency were found to be controlled by deformation depth, while the stored energy and maximum efficiency can be optimized by the ball size under the enclosed ball collision. Finally, the theoretical results were well verified by the experimental tests. The present work could provide strategies for improving the charging performance of TENGs toward effective water wave energy harvesting and storage.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, Jesse D.; Chang, Grace; Jones, Craig

The numerical model, SWAN (Simulating WAves Nearshore) , was used to simulate wave conditions in Kaneohe Bay, HI in order to determine the effects of wave energy converter ( WEC ) devices on the propagation of waves into shore. A nested SWAN model was validated then used to evaluate a range of initial wave conditions: significant wave heights (H s ) , peak periods (T p ) , and mean wave directions ( MWD) . Differences between wave height s in the presence and absence of WEC device s were assessed at locations in shore of the WEC array. Themore » maximum decrease in wave height due to the WEC s was predicted to be approximately 6% at 5 m and 10 m water depths. Th is occurred for model initiation parameters of H s = 3 m (for 5 m water depth) or 4 m (10 m water depth) , T p = 10 s, and MWD = 330deg . Subsequently, bottom orbital velocities were found to decrease by about 6%.« less

Flume experiments on wind induced flow in static water bodies in the presence of protruding vegetation

NASA Astrophysics Data System (ADS)

Banerjee, Tirtha; Muste, Marian; Katul, Gabriel

2015-02-01

The problem of wind-induced flow in inland waters is drawing significant research attention given its relevance to a plethora of applications in wetlands including treatment designs, pollution reduction, and biogeochemical cycling. The present work addresses the role of wind induced turbulence and waves within an otherwise static water body in the presence of rigid and flexible emergent vegetation through flume experimentation and time series analysis. Because no prior example of Particle Imaging Velocimetry (PIV) experiments involving air-water and flexible oscillating components have been found in the literature, a spectral analysis framework is needed and proposed here to guide the analysis involving noise, wave and turbulence separation. The experiments reveal that wave and turbulence effects are simultaneously produced at the air-water interface and the nature of their coexistence is found to vary with different flow parameters including water level, mean wind speed, vegetation density and its flexibility. For deep water levels, signature of fine-scaled inertial turbulence is found at deeper layers of the water system. The wave action appears stronger close to the air-water interface and damped by the turbulence deeper inside the water system. As expected, wave action is found to be dominated in a certain frequency range driven by the wind forcing, while it is also diffused to lower frequencies by means of (wind-induced) oscillations in vegetation. Regarding the mean water velocity, existence of a counter-current flow and its switching to fully forward flow in the direction of the wind under certain combinations of flow parameters were studied. The relative importance of wave and turbulence to the overall energy, degree of anisotropy in the turbulent energy components, and turbulent momentum transport at different depths from the air-water interface and flow combinations were then quantified. The flume experiments reported here differ from previous laboratory studies in the related literature involving vegetation in the sense that the wave forcing is only present on the water surface contrary to a full-body excitation by tidal wave simulators and thus important in advancing the knowledge regarding a wider range of water resource problems.

Waves and Water Beetles

ERIC Educational Resources Information Center

Tucker, Vance A.

1971-01-01

Capillary and gravity water waves are related to the position, wavelength, and velocity of an object in flowing water. Water patterns are presented for ships and the whirling beetle with an explanation of how the design affects the objects velocity and the observed water wavelengths. (DS)

Micro-tidal coastal reed beds: Hydro-morphological insights and observations on wave transformation from the southern Baltic Sea

NASA Astrophysics Data System (ADS)

I.; | J., Möller; | T., Mantilla-Contreras; | A., Spencer; Hayes

2011-05-01

This paper investigates the hydro-morphological controls on incident wind-generated waves at, and the transformation of such waves within, two Phragmites australis reed beds in the southern Baltic Sea. Meteorological conditions in combination with geomorphological controls result, over short (<2 km) distances, in significant differences in water level and wave climate to which fringing reed beds are exposed. Significant wave height attenuation reached a maximum of 2.6% m -1 and 11.8% m -1 at the transition from open water into the reed vegetation at the sheltered and exposed sites respectively. Wave attenuation through the emergent reed vegetation was significantly lower in greater water depths, suggesting (1) a reduced influence of bed friction by small shoots/roots and/or (2) drag reduction due to flexing of plants when the wave motion is impacting stems at a greater height above the bed. For a given water depth, wave dissipation increased with increasing incident wave height, however, suggesting that, despite their ability to flex, reed stems may be rigid enough to cause increased drag under greater wave forcing. The higher frequency part of the wave spectrum (>0.5 Hz) was preferentially reduced at the reed margin, confirming the theoretical wave frequency dependence of bottom friction. The possibility of physiological adaptation (differences in reed stem diameter) to water depth and wave exposure differences is discussed. The results have implications for the possible impact of environmental changes, both acute (e.g. storm surges) or chronic (e.g. sea level rise) in character, and for the appropriate management of reed bed sites and delivery of ecological goods and services.

Surfing surface gravity waves

NASA Astrophysics Data System (ADS)

Pizzo, Nick

2017-11-01

A simple criterion for water particles to surf an underlying surface gravity wave is presented. It is found that particles travelling near the phase speed of the wave, in a geometrically confined region on the forward face of the crest, increase in speed. The criterion is derived using the equation of John (Commun. Pure Appl. Maths, vol. 6, 1953, pp. 497-503) for the motion of a zero-stress free surface under the action of gravity. As an example, a breaking water wave is theoretically and numerically examined. Implications for upper-ocean processes, for both shallow- and deep-water waves, are discussed.

Consistent nonlinear deterministic and stochastic evolution equations for deep to shallow water wave shoaling

NASA Astrophysics Data System (ADS)

Vrecica, Teodor; Toledo, Yaron

2015-04-01

One-dimensional deterministic and stochastic evolution equations are derived for the dispersive nonlinear waves while taking dissipation of energy into account. The deterministic nonlinear evolution equations are formulated using operational calculus by following the approach of Bredmose et al. (2005). Their formulation is extended to include the linear and nonlinear effects of wave dissipation due to friction and breaking. The resulting equation set describes the linear evolution of the velocity potential for each wave harmonic coupled by quadratic nonlinear terms. These terms describe the nonlinear interactions between triads of waves, which represent the leading-order nonlinear effects in the near-shore region. The equations are translated to the amplitudes of the surface elevation by using the approach of Agnon and Sheremet (1997) with the correction of Eldeberky and Madsen (1999). The only current possibility for calculating the surface gravity wave field over large domains is by using stochastic wave evolution models. Hence, the above deterministic model is formulated as a stochastic one using the method of Agnon and Sheremet (1997) with two types of stochastic closure relations (Benney and Saffman's, 1966, and Hollway's, 1980). These formulations cannot be applied to the common wave forecasting models without further manipulation, as they include a non-local wave shoaling coefficients (i.e., ones that require integration along the wave rays). Therefore, a localization method was applied (see Stiassnie and Drimer, 2006, and Toledo and Agnon, 2012). This process essentially extracts the local terms that constitute the mean nonlinear energy transfer while discarding the remaining oscillatory terms, which transfer energy back and forth. One of the main findings of this work is the understanding that the approximated non-local coefficients behave in two essentially different manners. In intermediate water depths these coefficients indeed consist of rapidly oscillating terms, but as the water depth becomes shallow they change to an exponential growth (or decay) behavior. Hence, the formerly used localization technique cannot be justified for the shallow water region. A new formulation is devised for the localization in shallow water, it approximates the nonlinear non-local shoaling coefficient in shallow water and matches it to the one fitting to the intermediate water region. This allows the model behavior to be consistent from deep water to intermediate depths and up to the shallow water regime. Various simulations of the model were performed for the cases of intermediate, and shallow water, overall the model was found to give good results in both shallow and intermediate water depths. The essential difference between the shallow and intermediate nonlinear shoaling physics is explained via the dominating class III Bragg resonances phenomenon. By inspecting the resonance conditions and the nature of the dispersion relation, it is shown that unlike in the intermediate water regime, in shallow water depths the formation of resonant interactions is possible without taking into account bottom components. References Agnon, Y. & Sheremet, A. 1997 Stochastic nonlinear shoaling of directional spectra. J. Fluid Mech. 345, 79-99. Benney, D. J. & Saffman, P. G. 1966 Nonlinear interactions of random waves. Proc. R. Soc. Lond. A 289, 301-321. Bredmose, H., Agnon, Y., Madsen, P.A. & Schaffer, H.A. 2005 Wave transformation models with exact second-order transfer. European J. of Mech. - B/Fluids 24 (6), 659-682. Eldeberky, Y. & Madsen, P. A. 1999 Deterministic and stochastic evolution equations for fully dispersive and weakly nonlinear waves. Coastal Engineering 38, 1-24. Kaihatu, J. M. & Kirby, J. T. 1995 Nonlinear transformation of waves in infinite water depth. Phys. Fluids 8, 175-188. Holloway, G. 1980 Oceanic internal waves are not weak waves. J. Phys. Oceanogr. 10, 906-914. Stiassnie, M. & Drimer, N. 2006 Prediction of long forcing waves for harbor agitation studies. J. of waterways, port, coastal and ocean engineering 132(3), 166-171. Toledo, Y. & Agnon, Y. 2012 Stochastic evolution equations with localized nonlinear shoaling coefficients. European J. of Mech. - B/Fluids 34, 13-18.

Experimental investigation of the Peregrine Breather of gravity waves on finite water depth

NASA Astrophysics Data System (ADS)

Dong, G.; Liao, B.; Ma, Y.; Perlin, M.

2018-06-01

A series of laboratory experiments were performed to study the Peregrine Breather (PB) evolution in a wave flume of finite depth and deep water. Experimental cases were selected with water depths k0h (k0 is the wave number and h is the water depth) varying from 3.11 to 8.17 and initial steepness k0a0 (a0 is the background wave amplitude) in the range 0.06 to 0.12, and the corresponding initial Ursell number in the range 0.03 to 0.061. Experimental results indicate that the water depth plays an important role in the formation of the extreme waves in finite depth; the maximum wave amplification of the PB packets is also strongly dependent on the initial Ursell number. For experimental cases with the initial Ursell number larger than 0.05, the maximum crest amplification can exceed three. If the initial Ursell number is nearly 0.05, a shorter propagation distance is needed for maximum amplification of the height in deeper water. A time-frequency analysis using the wavelet transform reveals that the energy of the higher harmonics is almost in-phase with the carrier wave. The contribution of the higher harmonics to the extreme wave is significant for the cases with initial Ursell number larger than 0.05 in water depth k0h < 5.0. Additionally, the experimental results are compared with computations based on both the nonlinear Schrödinger (NLS) equation and the Dysthe equation, both with a dissipation term. It is found that both models with a dissipation term can predict the maximum amplitude amplification of the primary waves. However, the Dysthe equation also can predict the group horizontal asymmetry.

Linear and nonlinear propagation of water wave groups

NASA Technical Reports Server (NTRS)

Pierson, W. J., Jr.; Donelan, M. A.; Hui, W. H.

1992-01-01

Results are presented from a study of the evolution of waveforms with known analytical group shapes, in the form of both transient wave groups and the cloidal (cn) and dnoidal (dn) wave trains as derived from the nonlinear Schroedinger equation. The waveforms were generated in a long wind-wave tank of the Canada Centre for Inland Waters. It was found that the low-amplitude transients behaved as predicted by the linear theory and that the cn and dn wave trains of moderate steepness behaved almost as predicted by the nonlinear Schroedinger equation. Some of the results did not fit into any of the available theories for waves on water, but they provide important insight on how actual groups of waves propagate and on higher-order effects for a transient waveform.

Scaling Observations of Surface Waves in the Beaufort Sea

DTIC Science & Technology

2016-04-14

the treatment of wind input can be improved in partial ice cover using the ice concentration, where wave energy is a function of open water distance...drifting buoys during the 2014 open water season, are interpreted using open water distances determined from satellite ice products and wind forcing time...series measured in situ with the buoys. A significant portion of the wave observations were found to be limited by open water distance (fetch) when

Development of an Integrated Modeling Framework for Simulations of Coastal Processes in Deltaic Environments Using High-Performance Computing

DTIC Science & Technology

2009-01-01

attenuation and mass transport of a water -mud system due to a solitary wave on the free surface has been modeled by using the Chebyshev-Chebyshev...in Lagrangian coordinates and perturbation equations for shallow water waves were 3 derived. An iteration-by-subdomain technique was introduced to...found. Although the model is focused on solitary waves and Newtonian fluid-mud, the methodology can be extended to oscillatory, nonlinear water waves

Analysis of a Wave-Powered, Reverse-Osmosis System and its Economic Availability in the United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Yi-Hsiang; Jenne, Dale S

A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to permeate saltwater through the reverse-osmosis membrane to generate clean water. In this study, a wave-to-water numerical model was developed to investigate the potential use of a wave-powered desalination system (WPDS) for water production in the United States. The model was developed by coupling a time-domain radiation-and-diffraction-method-based numerical tool (WEC-Sim) for predicting the hydrodynamic performance of WECs with a solution-diffusion model that was used to simulate the reverse-osmosis process. To evaluate the feasibilitymore » of the WPDS, the wave-to-water numerical model was applied to simulate a desalination system that used an oscillating surge WEC device to pump seawater through the system. The annual water production was estimated based on the wave resource at a reference site on the coast of northern California to investigate the potential cost of water in that area, where the cost of water and electricity is high compared to other regions. In the scenario evaluated, for a 100-unit utility-scale array, the estimated levelized cost of energy for these WECs is about 3-6 times the U.S.'s current, unsubsidized electricity rates. However, with clean water as an end product and by directly producing pressurized water with WECs, rather than electricity as an intermediary, it is presently only 12% greater than typical water cost in California. This study suggests that a WEC array that produces water may be a viable, near-term solution to the nation's water supply, and the niche application of the WPDS may also provide developers with new opportunities to further develop technologies that benefit both the electric and drinking water markets.« less

Analysis of a Wave-Powered, Reverse-Osmosis System and Its Economic Availability in the United States: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Yi-Hsiang; Jenne, Dale S

A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to permeate saltwater through the reverse-osmosis membrane to generate clean water. In this study, a wave-to-water numerical model was developed to investigate the potential use of a wave-powered desalination system (WPDS) for water production in the United States. The model was developed by coupling a time-domain radiation-and-diffraction-method-based numerical tool (WEC-Sim) for predicting the hydrodynamic performance of WECs with a solution-diffusion model that was used to simulate the reverse-osmosis process. To evaluate the feasibilitymore » of the WPDS, the wave-to-water numerical model was applied to simulate a desalination system that used an oscillating surge WEC device to pump seawater through the system. The annual water production was estimated based on the wave resource at a reference site on the coast of northern California to investigate the potential cost of water in that area, where the cost of water and electricity is high compared to other regions. In the scenario evaluated, for a 100-unit utility-scale electricity-producing array, the estimated levelized cost of energy for these WECs is about 3-6 times the U.S.'s current, unsubsidized electricity rates. However, with clean water as an end product and by directly producing pressurized water with WECs, rather than electricity as an intermediary, it is presently only 12 percent greater than typical water cost in California. This study suggests that a WEC array that produces water may be a viable, near-term solution to the nation's water supply, and the niche application of the WPDS may also provide developers with new opportunities to further develop technologies that benefit both the electric and drinking water markets.« less

Effects of wave-current interaction on storm surge in the Taiwan Strait: Insights from Typhoon Morakot

NASA Astrophysics Data System (ADS)

Yu, Xiaolong; Pan, Weiran; Zheng, Xiangjing; Zhou, Shenjie; Tao, Xiaoqin

2017-08-01

The effects of wave-current interaction on storm surge are investigated by a two-dimensional wave-current coupling model through simulations of Typhoon Morakot in the Taiwan Strait. The results show that wind wave and slope of sea floor govern wave setup modulations within the nearshore surf zone. Wave setup during Morakot can contribute up to 24% of the total storm surge with a maximum value of 0.28 m. The large wave setup commonly coincides with enhanced radiation stress gradient, which is itself associated with transfer of wave momentum flux. Water levels are to leading order in modulating significant wave height inside the estuary. High water levels due to tidal change and storm surge stabilize the wind wave and decay wave breaking. Outside of the estuary, waves are mainly affected by the current-induced modification of wind energy input to the wave generation. By comparing the observed significant wave height and water level with the results from uncoupled and coupled simulations, the latter shows a better agreement with the observations. It suggests that wave-current interaction plays an important role in determining the extreme storm surge and wave height in the study area and should not be neglected in a typhoon forecast.

Rogue waves in shallow water

NASA Astrophysics Data System (ADS)

Soomere, T.

2010-07-01

Most of the processes resulting in the formation of unexpectedly high surface waves in deep water (such as dispersive and geometrical focusing, interactions with currents and internal waves, reflection from caustic areas, etc.) are active also in shallow areas. Only the mechanism of modulational instability is not active in finite depth conditions. Instead, wave amplification along certain coastal profiles and the drastic dependence of the run-up height on the incident wave shape may substantially contribute to the formation of rogue waves in the nearshore. A unique source of long-living rogue waves (that has no analogues in the deep ocean) is the nonlinear interaction of obliquely propagating solitary shallow-water waves and an equivalent mechanism of Mach reflection of waves from the coast. The characteristic features of these processes are (i) extreme amplification of the steepness of the wave fronts, (ii) change in the orientation of the largest wave crests compared with that of the counterparts and (iii) rapid displacement of the location of the extreme wave humps along the crests of the interacting waves. The presence of coasts raises a number of related questions such as the possibility of conversion of rogue waves into sneaker waves with extremely high run-up. Also, the reaction of bottom sediments and the entire coastal zone to the rogue waves may be drastic.

Effects of Internal Waves on Sound Propagation in the Shallow Waters of the Continental Shelves

DTIC Science & Technology

2016-09-01

experiment area were largely generated by tidal forcing. Compared to simulations without internal waves , simulations accounting for the effects of...internal waves in the experiment area were largely generated by tidal forcing. Compared to simulations without internal waves , simulations accounting for...IN THE SHALLOW WATERS OF THE CONTINENTAL SHELVES ..................................4  1.  Internal Tides—Internal Waves Generated by Tidal Forcing

Gravity-Capillary Lumps

NASA Astrophysics Data System (ADS)

Akylas, Triantaphyllos R.; Kim, Boguk

2004-11-01

In dispersive wave systems, it is known that 1-D plane solitary waves can bifurcate from linear sinusoidal wavetrains at particular wave numbers k = k0 where the phase speed c(k) happens to be an extremum (dc/dk| _0=0) and equals the group speed c_g(k_0). Two distinct possibilities thus arise: either the extremum occurs in the long-wave limit (k_0=0) and, as in shallow water, the bifurcating solitary waves are of the KdV type; or k0 ne 0 and the solitary waves are in the form of packets, described by the NLS equation to leading order, as for gravity-capillary waves in deep water. Here it is pointed out that an entirely analogous scenario is valid for the genesis of 2-D solitary waves or `lumps'. Lumps also may bifurcate at extrema of the phase speed and do so when 1-D solitary waves happen to be unstable to transverse perturbations; moreover, they have algebraically decaying tails and are either of the KPI type (e.g. in shallow water in the presence of strong surface tension) or of the wave packet type (e.g. in deep water) and are described by an elliptic-elliptic Davey-Stewartson equation system to leading order. Examples of steady lump profiles are presented and their dynamics is discussed.

Surface wave effects on water temperature in the Baltic Sea: simulations with the coupled NEMO-WAM model

NASA Astrophysics Data System (ADS)

Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter

2016-08-01

Coupled circulation (NEMO) and wave model (WAM) system was used to study the effects of surface ocean waves on water temperature distribution and heat exchange at regional scale (the Baltic Sea). Four scenarios—including Stokes-Coriolis force, sea-state dependent energy flux (additional turbulent kinetic energy due to breaking waves), sea-state dependent momentum flux and the combination these forcings—were simulated to test the impact of different terms on simulated temperature distribution. The scenario simulations were compared to a control simulation, which included a constant wave-breaking coefficient, but otherwise was without any wave effects. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwelling's. Overall, when all three wave effects were accounted for, did the estimates of temperature improve compared to control simulation. During the summer, the wave-induced water temperature changes were up to 1 °C. In northern parts of the Baltic Sea, a warming of the surface layer occurs in the wave included simulations in summer months. This in turn reduces the cold bias between simulated and measured data, e.g. the control simulation was too cold compared to measurements. The warming is related to sea-state dependent energy flux. This implies that a spatio-temporally varying wave-breaking coefficient is necessary, because it depends on actual sea state. Wave-induced cooling is mostly observed in near-coastal areas and is the result of intensified upwelling in the scenario, when Stokes-Coriolis forcing is accounted for. Accounting for sea-state dependent momentum flux results in modified heat exchange at the water-air boundary which consequently leads to warming of surface water compared to control simulation.

7 CFR 1945.6 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., tornado, storm, flood, high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic eruption... hurricane, tornado, storm, flood, high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic..., earthquake, hurricane or tornado. (B) A single storm, or series of storms, accompanied by severe hail...

7 CFR 1945.6 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

..., tornado, storm, flood, high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic eruption... hurricane, tornado, storm, flood, high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic..., earthquake, hurricane or tornado. (B) A single storm, or series of storms, accompanied by severe hail...

7 CFR 1945.6 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

..., tornado, storm, flood, high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic eruption... hurricane, tornado, storm, flood, high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic..., earthquake, hurricane or tornado. (B) A single storm, or series of storms, accompanied by severe hail...

Multi-Periodic Waves in Shallow Water

DTIC Science & Technology

1992-09-01

models-the Kadomtsev - Petviashvili (KP) equation . The KP equation describes the evolu- tion of weakly nonlinear, weakly two-dimensional waves on water of...experimentally. The analytical model is a family of periodic solutions of the Kadomtsev -Petviashuili equation . The experiments demonstrate the accuracy... Petviashvili Equation (with Norman Schef- fner & Harvey Segur). Proceedings, Nonlinear Water Waves Workshop, University of Bristol. England, 1991. Resonant

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets

PubMed Central

Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, YoungPak

2015-01-01

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet–height and diameter– and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials. PMID:26354891

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets

NASA Astrophysics Data System (ADS)

Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, Youngpak

2015-09-01

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet-height and diameter- and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets.

PubMed

Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, YoungPak

2015-09-10

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet-height and diameter- and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.

Effect of water depth on wind-wave frequency spectrum I. Spectral form

NASA Astrophysics Data System (ADS)

Wen, Sheng-Chang; Guan, Chang-Long; Sun, Shi-Cai; Wu, Ke-Jian; Zhang, Da-Cuo

1996-06-01

Wen et al's method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the zeroth moment m 0 and peak frequency {ie97-1}, contains in addition to the peakness factor {ie97-2} a depth parameter η=(2π m o)1/2/ d ( d being water depth), so the spectrum behavior can be studied for different wave growth stages and water depths.

A unified spectral,parameterization for wave breaking: from the deep ocean to the surf zone

NASA Astrophysics Data System (ADS)

Filipot, J.

2010-12-01

A new wave-breaking dissipation parameterization designed for spectral wave models is presented. It combines wave breaking basic physical quantities, namely, the breaking probability and the dissipation rate per unit area. The energy lost by waves is fi[|#12#|]rst calculated in the physical space before being distributed over the relevant spectral components. This parameterization allows a seamless numerical model from the deep ocean into the surf zone. This transition from deep to shallow water is made possible by a dissipation rate per unit area of breaking waves that varies with the wave height, wavelength and water depth.The parameterization is further tested in the WAVEWATCH III TM code, from the global ocean to the beach scale. Model errors are smaller than with most specialized deep or shallow water parameterizations.

PHYSICS OF OUR DAYS: Nonlinear long waves on water and solitons

NASA Astrophysics Data System (ADS)

Zeytounian, R. Kh

1995-12-01

The water wave problem has been pivotal in the history of nonlinear wave theory. This problem is one of the most interesting and successful applications of nonlinear hydrodynamics. Waves on the free surface of a body of water (perfect liquid) have always been a fascinating subject, for they represent a familiar yet complex phenomenon, easy to observe but very difficult to describe! The archetypical model equations of Kordeweg and de Vries and of Boussinesq, for example, were originally derived as approximations for water waves, and research into the problem has been sustained vigorously up to the present day. In the present paper, the derivation of the model equations is given in depth and rational use is made of asymptotic methods. Indeed, it is important to understand that in some cases the derivation of these approximate equations is intuitive and heuristic. In fact, it is not clear how to insert the model equation under consideration into a hierarchy of rational approximations, which in turn result from the exact formulation of the selected water wave problem.

Generation of multivariate near shore extreme wave conditions based on an extreme value copula for offshore boundary conditions.

NASA Astrophysics Data System (ADS)

Leyssen, Gert; Mercelis, Peter; De Schoesitter, Philippe; Blanckaert, Joris

2013-04-01

Near shore extreme wave conditions, used as input for numerical wave agitation simulations and for the dimensioning of coastal defense structures, need to be determined at a harbour entrance situated at the French North Sea coast. To obtain significant wave heights, the numerical wave model SWAN has been used. A multivariate approach was used to account for the joint probabilities. Considered variables are: wind velocity and direction, water level and significant offshore wave height and wave period. In a first step a univariate extreme value distribution has been determined for the main variables. By means of a technique based on the mean excess function, an appropriate member of the GPD is selected. An optimal threshold for peak over threshold selection is determined by maximum likelihood optimization. Next, the joint dependency structure for the primary random variables is modeled by an extreme value copula. Eventually the multivariate domain of variables was stratified in different classes, each of which representing a combination of variable quantiles with a joint probability, which are used for model simulation. The main variable is the wind velocity, as in the area of concern extreme wave conditions are wind driven. The analysis is repeated for 9 different wind directions. The secondary variable is water level. In shallow waters extreme waves will be directly affected by water depth. Hence the joint probability of occurrence for water level and wave height is of major importance for design of coastal defense structures. Wind velocity and water levels are only dependent for some wind directions (wind induced setup). Dependent directions are detected using a Kendall and Spearman test and appeared to be those with the longest fetch. For these directions, wind velocity and water level extreme value distributions are multivariately linked through a Gumbel Copula. These distributions are stratified into classes of which the frequency of occurrence can be calculated. For the remaining directions the univariate extreme wind velocity distribution is stratified, each class combined with 5 high water levels. The wave height at the model boundaries was taken into account by a regression with the extreme wind velocity at the offshore location. The regression line and the 95% confidence limits where combined with each class. Eventually the wave period is computed by a new regression with the significant wave height. This way 1103 synthetic events were selected and simulated with the SWAN wave model, each of which a frequency of occurrence is calculated for. Hence near shore significant wave heights are obtained with corresponding frequencies. The statistical distribution of the near shore wave heights is determined by sorting the model results in a descending order and accumulating the corresponding frequencies. This approach allows determination of conditional return periods. For example, for the imposed univariate design return periods of 100 years for significant wave height and 30 years for water level, the joint return period for a simultaneous exceedance of both conditions can be computed as 4000 years. Hence, this methodology allows for a probabilistic design of coastal defense structures.

Low-grazing angle laser scans of foreshore topography, swash and inner surf-zone wave heights, and mean water level: validation and storm response

NASA Astrophysics Data System (ADS)

Brodie, K. L.; McNinch, J. E.; Forte, M.; Slocum, R.

2010-12-01

Accurately predicting beach evolution during storms requires models that correctly parameterize wave runup and inner surf-zone processes, the principle drivers of sediment exchange between the beach and surf-zone. Previous studies that aimed at measuring wave runup and swash zone water levels have been restricted to analyzing water-elevation time series of (1) the shoreward-most swash excursion using video imaging or near-bed resistance wires, or (2) the free water surface at a particular location on the foreshore using pressure sensors. These data are often compared with wave forcing parameters in deeper water as well as with beach topography observed at finite intervals throughout the time series to identify links between foreshore evolution, wave spectra, and water level variations. These approaches have lead to numerous parameterizations and empirical equations for wave runup but have difficulty providing adequate data to quantify and understand short-term spatial and temporal variations in foreshore evolution. As a result, modeling shoreline response and changes in sub-aerial beach volume during storms remains a substantial challenge. Here, we demonstrate a novel technique in which a terrestrial laser scanner is used to continuously measure beach and foreshore topography as well as water elevation (and wave height) in the swash and inner surf-zone during storms. The terrestrial laser scanner is mounted 2-m above the dune crest at the Field Research Facility in Duck, NC in line with cross-shore wave gauges located at 2-m, 3-m, 5-m, 6-m, and 8-m of water depth. The laser is automated to collect hourly, two-dimensional, 20-minute time series of data along a narrow swath in addition to an hourly three-dimensional laser scan of beach and dune topography +/- 250m alongshore from the laser. Low grazing-angle laser scans are found to reflect off of the surface of the water, providing spatially (e.g. dx <= 0.1 m) and temporally (e.g. dt = 3Hz) dense elevation data of the foreshore, swash, and inner-surf zone bore heights. Foreshore elevation precision is observed to be < 0.01m. Sea surface elevation data is confined to the breaking region and is more extensive in rough, fully-dissipative surf zones, with the fronts of breaking waves and dissipated bores resolved most clearly. Time series of swash front (runup) data will be compared with simultaneously collected video-imaged swash timestacks, and wave height data of the inner surf zone will be compared with wave data from an aquadopp in 2m of water depth. In addition, analysis of the water level time series data at 10 cm intervals across the profile enables reconstruction of the shoreline setup profile as well as cross-shore variations in 1D wave spectra. Foreshore beach morphology evolution is analyzed using both the 2D cross-shore profile data, as well as the 3D topographic data during multiple storm events. Potential sources of error in the measurements, such as shadowing of the wave troughs or reflectance off of wave spray is identified and quantified.

Characterization of the Deep Water Surface Wave Variability in the California Current Region

NASA Astrophysics Data System (ADS)

Villas Bôas, Ana B.; Gille, Sarah T.; Mazloff, Matthew R.; Cornuelle, Bruce D.

2017-11-01

Surface waves are crucial for the dynamics of the upper ocean not only because they mediate exchanges of momentum, heat, energy, and gases between the ocean and the atmosphere, but also because they determine the sea state. The surface wave field in a given region is set by the combination of local and remote forcing. The present work characterizes the seasonal variability of the deep water surface wave field in the California Current region, as retrieved from over two decades of satellite altimetry data combined with wave buoys and wave model hindcast (WaveWatch III). In particular, the extent to which the local wind modulates the variability of the significant wave height, peak period, and peak direction is assessed. During spring/summer, regional-scale wind events of up to 10 m/s are the dominant forcing for waves off the California coast, leading to relatively short-period waves (8-10 s) that come predominantly from the north-northwest. The wave climatology throughout the California Current region shows average significant wave heights exceeding 2 m during most of the year, which may have implications for the planning and retrieval methods of the Surface Water and Ocean Topography (SWOT) satellite mission.

HF Radar Sea-echo from Shallow Water.

PubMed

Lipa, Belinda; Nyden, Bruce; Barrick, Don; Kohut, Josh

2008-08-06

HF radar systems are widely and routinely used for the measurement of ocean surface currents and waves. Analysis methods presently in use are based on the assumption of infinite water depth, and may therefore be inadequate close to shore where the radar echo is strongest. In this paper, we treat the situation when the radar echo is returned from ocean waves that interact with the ocean floor. Simulations are described which demonstrate the effect of shallow water on radar sea-echo. These are used to investigate limits on the existing theory and to define water depths at which shallow-water effects become significant. The second-order spectral energy increases relative to the first-order as the water depth decreases, resulting in spectral saturation when the waveheight exceeds a limit defined by the radar transmit frequency. This effect is particularly marked for lower radar transmit frequencies. The saturation limit on waveheight is less for shallow water. Shallow water affects second-order spectra (which gives wave information) far more than first-order (which gives information on current velocities), the latter being significantly affected only for the lowest radar transmit frequencies for extremely shallow water. We describe analysis of radar echo from shallow water measured by a Rutgers University HF radar system to give ocean wave spectral estimates. Radar-derived wave height, period and direction are compared with simultaneous shallow-water in-situ measurements.

HF Radar Sea-echo from Shallow Water

PubMed Central

Lipa, Belinda; Nyden, Bruce; Barrick, Don; Kohut, Josh

2008-01-01

HF radar systems are widely and routinely used for the measurement of ocean surface currents and waves. Analysis methods presently in use are based on the assumption of infinite water depth, and may therefore be inadequate close to shore where the radar echo is strongest. In this paper, we treat the situation when the radar echo is returned from ocean waves that interact with the ocean floor. Simulations are described which demonstrate the effect of shallow water on radar sea-echo. These are used to investigate limits on the existing theory and to define water depths at which shallow-water effects become significant. The second-order spectral energy increases relative to the first-order as the water depth decreases, resulting in spectral saturation when the waveheight exceeds a limit defined by the radar transmit frequency. This effect is particularly marked for lower radar transmit frequencies. The saturation limit on waveheight is less for shallow water. Shallow water affects second-order spectra (which gives wave information) far more than first-order (which gives information on current velocities), the latter being significantly affected only for the lowest radar transmit frequencies for extremely shallow water. We describe analysis of radar echo from shallow water measured by a Rutgers University HF radar system to give ocean wave spectral estimates. Radar-derived wave height, period and direction are compared with simultaneous shallow-water in-situ measurements. PMID:27873776

A metasurface carpet cloak for electromagnetic, acoustic and water waves.

PubMed

Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

2016-01-29

We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak.

Impact of plunging breaking waves on a partially submerged cube

NASA Astrophysics Data System (ADS)

Wang, A.; Ikeda, C.; Duncan, J. H.

2013-11-01

The impact of a deep-water plunging breaking wave on a partially submerged cube is studied experimentally in a tank that is 14.8 m long and 1.2 m wide with a water depth of 0.91 m. The breakers are created from dispersively focused wave packets generated by a programmable wave maker. The water surface profile in the vertical center plane of the cube is measured using a cinematic laser-induced fluorescence technique with movie frame rates ranging from 300 to 4,500 Hz. The pressure distribution on the front face of the cube is measured with 24 fast-response sensors simultaneously with the wave profile measurements. The cube is positioned vertically at three heights relative to the mean water level and horizontally at a distance from the wave maker where a strong vertical water jet is formed. The portion of the water surface between the contact point on the front face of the cube and the wave crest is fitted with a circular arc and the radius and vertical position of the fitted circle is tracked during the impact. The vertical acceleration of the contact point reaches more than 50 times the acceleration of gravity and the pressure distribution just below the free surface shows a localized high-pressure region with a very high vertical pressure gradient. This work is supported by the Office of Naval Research under grant N000141110095.

Development, Test, and Evaluation of Microwave Radar Water Level (MWWL) Sensors' Wave Measurement Capability

NASA Astrophysics Data System (ADS)

Iyer, S. K.; Heitsenrether, R.

2015-12-01

Waves can have a significant impact on many coastal operations including navigational safety, recreation, and even the economy. Despite this, as of 2009, there were only 181 in situ real-time wave observation networks nationwide (IOOS 2009). There has recently been interest in adding real-time wave measurement systems to already existing NOAA Center for Operational Oceanographic Products and Services (CO-OPS) stations. Several steps have already been taken in order to achieve this, such as integrating information from existing wave measurement buoys and initial testing of multiple different wave measurement systems (Heitsenrether et al. 2012). Since wave observations can be derived from high frequency water level changes, we will investigate water level sensors' capability to measure waves. Recently, CO-OPS has been transitioning to new microwave radar water level (MWWL) sensors which have higher resolution and theoretically a greater potential wave measurement capability than the acoustic sensors in stilling wells. In this study, we analyze the wave measurement capability of MWWL sensors at two high energy wave environments, Duck, NC and La Jolla, CA, and compare results to two "reference" sensors (A Nortek acoustic waves and currents profiler (AWAC) at Duck and a single point pressure sensor at La Jolla). A summary of results from the two field test sites will be presented, including comparisons of wave energy spectra, significant wave height, and peak period measured by the test MWWL sensors and both reference AWAC and pressure sensors. In addition, relationships between MWWL versus reference wave sensor differences and specific wave conditions will be discussed. Initial results from spectral analysis and the calculation of bulk wave parameters indicate that MWWL sensors set to the "NoFilter" processing setting can produce wave measurements capability that compare well to the two reference sensors. These results support continued development to enable the installation of MWWL sensors at CO-OPS locations as a method of measuring waves.

Evolution of wave and tide over vegetation region in nearshore waters

NASA Astrophysics Data System (ADS)

Zhang, Mingliang; Zhang, Hongxing; Zhao, Kaibin; Tang, Jun; Qin, Huifa

2017-08-01

Coastal wetlands are an important ecosystem in nearshore regions, where complex flow characteristics occur because of the interactions among tides, waves, and plants, especially in the discontinuous flow of the intertidal zone. In order to simulate the wave and wave-induced current in coastal waters, in this study, an explicit depth-averaged hydrodynamic (HD) model has been dynamically coupled with a wave spectral model (CMS-Wave) by sharing the tide and wave data. The hydrodynamic model is based on the finite volume method; the intercell flux is computed using the Harten-Lax-van Leer (HLL) approximate Riemann solver for computing the dry-to-wet interface; the drag force of vegetation is modeled as the sink terms in the momentum equations. An empirical wave energy dissipation term with plant effect has been derived from the wave action balance equation to account for the resistance induced by aquatic vegetation in the CMS-Wave model. The results of the coupling model have been verified using the measured data for the case with wave-tide-vegetation interactions. The results show that the wave height decreases significantly along the wave propagation direction in the presence of vegetation. In the rip channel system, the oblique waves drive a meandering longshore current; it moves from left to right past the cusps with oscillations. In the vegetated region, the wave height is greatly attenuated due to the presence of vegetation, and the radiation stresses are noticeably changed as compared to the region without vegetation. Further, vegetation can affect the spatial distribution of mean velocity in a rip channel system. In the co-exiting environment of tides, waves, and vegetation, the locations of wave breaking and wave-induced radiation stress also vary with the water level of flooding or ebb tide in wetland water, which can also affect the development and evolution of wave-induced current.

7 CFR 1806.23 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels, or abnormally high tidal water or rising coastal waters resulting from severe storms, hurricanes, or tidal waves resulting from volcano eruptions or earthquakes. (g) Mudslide or...

7 CFR 1806.23 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels, or abnormally high tidal water or rising coastal waters resulting from severe storms, hurricanes, or tidal waves resulting from volcano eruptions or earthquakes. (g) Mudslide or...

7 CFR 1806.23 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels, or abnormally high tidal water or rising coastal waters resulting from severe storms, hurricanes, or tidal waves resulting from volcano eruptions or earthquakes. (g) Mudslide or...

7 CFR 1806.23 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels, or abnormally high tidal water or rising coastal waters resulting from severe storms, hurricanes, or tidal waves resulting from volcano eruptions or earthquakes. (g) Mudslide or...

7 CFR 1806.23 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels, or abnormally high tidal water or rising coastal waters resulting from severe storms, hurricanes, or tidal waves resulting from volcano eruptions or earthquakes. (g) Mudslide or...

On Periodic Water Waves with Coriolis Effects and Isobaric Streamlines

NASA Astrophysics Data System (ADS)

Matioc, Anca-Voichita; Matioc, Bogdan-Vasile

2012-10-01

In this paper we prove that solutions of the f-plane approximation for equatorial geophysical deep water waves, which have the property that the pressure is constant along the streamlines and do not possess stagnation points, are Gerstner-type waves. Furthermore, for waves traveling over a flat bed, we prove that there are only laminar flow solutions with these properties.

From the paddle to the beach - A Boussinesq shallow water numerical wave tank based on Madsen and Sørensen's equations

NASA Astrophysics Data System (ADS)

Orszaghova, Jana; Borthwick, Alistair G. L.; Taylor, Paul H.

2012-01-01

This article describes a one-dimensional numerical model of a shallow-water flume with an in-built piston paddle moving boundary wavemaker. The model is based on a set of enhanced Boussinesq equations and the nonlinear shallow water equations. Wave breaking is described approximately, by locally switching to the nonlinear shallow water equations when a critical wave steepness is reached. The moving shoreline is calculated as part of the solution. The piston paddle wavemaker operates on a movable grid, which is Lagrangian on the paddle face and Eulerian away from the paddle. The governing equations are, however, evolved on a fixed mapped grid, and the newly calculated solution is transformed back onto the moving grid via a domain mapping technique. Validation test results are compared against analytical solutions, confirming correct discretisation of the governing equations, wave generation via the numerical paddle, and movement of the wet/dry front. Simulations are presented that reproduce laboratory experiments of wave runup on a plane beach and wave overtopping of a laboratory seawall, involving solitary waves and compact wave groups. In practice, the numerical model is suitable for simulating the propagation of weakly dispersive waves and can additionally model any associated inundation, overtopping or inland flooding within the same simulation.

Water level effects on breaking wave setup for Pacific Island fringing reefs

NASA Astrophysics Data System (ADS)

Becker, J. M.; Merrifield, M. A.; Ford, M.

2014-02-01

The effects of water level variations on breaking wave setup over fringing reefs are assessed using field measurements obtained at three study sites in the Republic of the Marshall Islands and the Mariana Islands in the western tropical Pacific Ocean. At each site, reef flat setup varies over the tidal range with weaker setup at high tide and stronger setup at low tide for a given incident wave height. The observed water level dependence is interpreted in the context of radiation stress gradients specified by an idealized point break model generalized for nonnormally incident waves. The tidally varying setup is due in part to depth-limited wave heights on the reef flat, as anticipated from previous reef studies, but also to tidally dependent breaking on the reef face. The tidal dependence of the breaking is interpreted in the context of the point break model in terms of a tidally varying wave height to water depth ratio at breaking. Implications for predictions of wave-driven setup at reef-fringed island shorelines are discussed.

Wind wave prediction in shallow water: Theory and applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavaleri, L.; Rizzoli, P.M.

1981-11-20

A wind wave forecasting model is described, based upon the ray technique, which is specifically designed for shallow water areas. The model explicitly includes wave generation, refraction, and shoaling, while nonlinear dissipative processes (breaking and bottom fricton) are introduced through a suitable parametrization. The forecast is provided at a specified time and target position, in terms of a directional spectrum, from which the one-dimensional spectrum and the significant wave height are derived. The model has been used to hindcast storms both in shallow water (Northern Adriatic Sea) and in deep water conditions (Tyrrhenian Sea). The results have been compared withmore » local measurements, and the rms error for the significant wave height is between 10 and 20%. A major problems has been found in the correct evaluation of the wind field.« less

The Harp probe - An in situ Bragg scattering sensor

NASA Technical Reports Server (NTRS)

Mollo-Christensen, E.; Huang, N. E.; Long, S. R.; Bliven, L. F.

1984-01-01

A wave sensor, consisting of parallel, evenly spaced capacitance wires, whose output is the sum of the water surface deflections at the wires, has been built and tested in a wave tank. The probe output simulates Bragg scattering of electromagnetic waves from a water surface with waves; it can be used to simulate electromagnetic probing of the sea surface by radar. The study establishes that the wave probe, called the 'Harp' for short, will simulate Bragg scattering and that it can also be used to study nonlinear wave processes.

On the stability of lumps and wave collapse in water waves.

PubMed

Akylas, T R; Cho, Yeunwoo

2008-08-13

In the classical water-wave problem, fully localized nonlinear waves of permanent form, commonly referred to as lumps, are possible only if both gravity and surface tension are present. While much attention has been paid to shallow-water lumps, which are generalizations of Korteweg-de Vries solitary waves, the present study is concerned with a distinct class of gravity-capillary lumps recently found on water of finite or infinite depth. In the near linear limit, these lumps resemble locally confined wave packets with envelope and wave crests moving at the same speed, and they can be approximated in terms of a particular steady solution (ground state) of an elliptic equation system of the Benney-Roskes-Davey-Stewartson (BRDS) type, which governs the coupled evolution of the envelope along with the induced mean flow. According to the BRDS equations, however, initial conditions above a certain threshold develop a singularity in finite time, known as wave collapse, due to nonlinear focusing; the ground state, in fact, being exactly at the threshold for collapse suggests that the newly discovered lumps are unstable. In an effort to understand the role of this singularity in the dynamics of lumps, here we consider the fifth-order Kadomtsev-Petviashvili equation, a model for weakly nonlinear gravity-capillary waves on water of finite depth when the Bond number is close to one-third, which also admits lumps of the wave packet type. It is found that an exchange of stability occurs at a certain finite wave steepness, lumps being unstable below but stable above this critical value. As a result, a small-amplitude lump, which is linearly unstable and according to the BRDS equations would be prone to wave collapse, depending on the perturbation, either decays into dispersive waves or evolves into an oscillatory state near a finite-amplitude stable lump.

A note on the effect of wind waves on vertical mixing in Franks Tract, Sacramento-San Joaquin Delta, California, USA

USGS Publications Warehouse

Thompson, Janet K.; Jones, Nicole L.; Stephen G. Monismith,

2008-01-01

A one-dimensional numerical model that simulates the effects of whitecapping waves was used to investigate the importance of whitecapping waves to vertical mixing at a 3-meter-deep site in Franks Tract in the Sacramento-San Joaquin Delta over an 11-day period. Locally-generated waves of mean period approximately 2 s were generated under strong wind conditions; significant wave heights ranged from 0 to 0.3 m. A surface turbulent kinetic energy flux was used to model whitecapping waves during periods when wind speeds > 5 m s-1 (62% of observations). The surface was modeled as a wind stress log-layer for the remaining 38% of the observations. The model results demonstrated that under moderate wind conditions (5–8 m s-1 at 10 m above water level), and hence moderate wave heights, whitecapping waves provided the dominant source of turbulent kinetic energy to only the top 10% of the water column. Under stronger wind (> 8 m s-1), and hence larger wave conditions, whitecapping waves provided the dominant source of turbulent kinetic energy over a larger portion of the water column; however, this region extended to the bottom half of the water column for only 7% of the observation period. The model results indicated that phytoplankton concentrations close to the bed were unlikely to be affected by the whitecapping of waves, and that the formation of concentration boundary layers due to benthic grazing was unlikely to be disrupted by whitecapping waves. Furthermore, vertical mixing of suspended sediment was unlikely to be affected by whitecapping waves under the conditions experienced during the 11-day experiment. Instead, the bed stress provided by tidal currents was the dominant source of turbulent kinetic energy over the bottom half of the water column for the majority of the 11-day period.

Unique determination of stratified steady water waves from pressure

NASA Astrophysics Data System (ADS)

Chen, Robin Ming; Walsh, Samuel

2018-01-01

Consider a two-dimensional stratified solitary wave propagating through a body of water that is bounded below by an impermeable ocean bed. In this work, we study how such a wave can be recovered from data consisting of the wave speed, upstream and downstream density and velocity profile, and the trace of the pressure on the bed. In particular, we prove that this data uniquely determines the wave, both in the (real) analytic and Sobolev regimes.

Acoustic wave propagation and intensity fluctuations in shallow water 2006 experiment

NASA Astrophysics Data System (ADS)

Luo, Jing

Fluctuations of low frequency sound propagation in the presence of nonlinear internal waves during the Shallow Water 2006 experiment are analyzed. Acoustic waves and environmental data including on-board ship radar images were collected simultaneously before, during, and after a strong internal solitary wave packet passed through a source-receiver acoustic track. Analysis of the acoustic wave signals shows temporal intensity fluctuations. These fluctuations are affected by the passing internal wave and agrees well with the theory of the horizontal refraction of acoustic wave propagation in shallow water. The intensity focusing and defocusing that occurs in a fixed source-receiver configuration while internal wave packet approaches and passes the acoustic track is addressed in this thesis. Acoustic ray-mode theory is used to explain the modal evolution of broadband acoustic waves propagating in a shallow water waveguide in the presence of internal waves. Acoustic modal behavior is obtained from the data through modal decomposition algorithms applied to data collected by a vertical line array of hydrophones. Strong interference patterns are observed in the acoustic data, whose main cause is identified as the horizontal refraction referred to as the horizontal Lloyd mirror effect. To analyze this interference pattern, combined Parabolic Equation model and Vertical-mode horizontal-ray model are utilized. A semi-analytic formula for estimating the horizontal Lloyd mirror effect is developed.

Rogue waves in a water tank: Experiments and modeling

NASA Astrophysics Data System (ADS)

Lechuga, Antonio

2013-04-01

Recently many rogue waves have been reported as the main cause of ship incidents on the sea. One of the main characteristics of rogue waves is its elusiveness: they present unexpectedly and disappear in the same wave. Some authors (Zakharov and al.2010) are attempting to find the probability of their appearances apart from studyingthe mechanism of the formation. As an effort on this topic we tried the generation of rogue waves in a water wave tank using a symmetric spectrum(Akhmediev et al. 2011) as input on the wave maker. The produced waves were clearly rogue waves with a rate (maximum wave height/ Significant wave height) of 2.33 and a kurtosis of 4.77 (Janssen 2003, Onorato 2006). These results were already presented (Lechuga 2012). Similar waves (in pattern aspect, but without being extreme waves) were described as crossing waves in a water tank(Shemer and Lichter1988). To go on further the next step has been to apply a theoretical model to the envelope of these waves. After some considerations the best model has been an analogue of the Ginzburg-Landau equation. This apparently amazing result is easily explained: We know that the Ginzburg-Landau model is related to some regular structures on the surface of a liquid and also in plasmas, electric and magnetic fields and other media. Another important characteristic of the model is that their solutions are invariants with respectto the translation group. The main aim of this presentation is to extract conclusions of the model and the comparison with the measured waves in the water tank.The nonlinear structure of waves and their regularity make suitable the use of the Ginzburg-Landau model to the envelope of generated waves in the tank,so giving us a powerful tool to cope with the results of our experiment.

Laser probe for measuring 2-D wave slope spectra of ocean capillary waves

NASA Technical Reports Server (NTRS)

Palm, C. S.; Anderson, R. C.; Reece, A. M.

1977-01-01

A laser-optical instrument for use in determining the two-dimensional wave-slope spectrum of ocean capillary waves is described. The instrument measures up to a 35-deg tip angle of the surface normal by measuring the position of a refracted laser beam directed vertically upward through a water surface. A telescope, a continuous two-dimensional Schottky barrier photodiode, and a pair of analog dividers render the signals independent of water height and insensitive to laser-beam intensity fluctuations. Calibration is performed entirely in the laboratory before field use. Sample records and wave-slope spectra are shown for one-dimensional wave-tank tests and for two-dimensional ocean tests. These are presented along with comparison spectra for calm and choppy water conditions. A mechanical wave follower was used to adjust the instrument position in the presence of large ocean swell and tides.

Linear Water Waves

NASA Astrophysics Data System (ADS)

Kuznetsov, N.; Maz'ya, V.; Vainberg, B.

2002-08-01

This book gives a self-contained and up-to-date account of mathematical results in the linear theory of water waves. The study of waves has many applications, including the prediction of behavior of floating bodies (ships, submarines, tension-leg platforms etc.), the calculation of wave-making resistance in naval architecture, and the description of wave patterns over bottom topography in geophysical hydrodynamics. The first section deals with time-harmonic waves. Three linear boundary value problems serve as the approximate mathematical models for these types of water waves. The next section uses a plethora of mathematical techniques in the investigation of these three problems. The techniques used in the book include integral equations based on Green's functions, various inequalities between the kinetic and potential energy and integral identities which are indispensable for proving the uniqueness theorems. The so-called inverse procedure is applied to constructing examples of non-uniqueness, usually referred to as 'trapped nodes.'

The calming effect of oil on water

NASA Astrophysics Data System (ADS)

Behroozi, Peter; Cordray, Kimberly; Griffin, William; Behroozi, Feredoon

2007-05-01

The calming effect of oil on water has been known since ancient times. Benjamin Franklin was the first to investigate the effect, but the underlying mechanism for this striking phenomenon remains elusive. We used a miniature laser interferometer to measure the amplitude of surface waves to a resolution of ±5nm, making it possible to determine the effect of an oil monolayer on the attenuation of capillary waves and the surface dilational modulus of the monolayer. We present attenuation data on pure water, water covered by olive oil, water covered by a fatty acid, and a water-acetone mixture for comparison. From the attenuation data at frequencies between 251 and 551Hz, we conclude that the calming effect of oil on surface waves is principally due to the dissipation of wave energy caused by the Gibbs surface elasticity of the monolayer, with only a secondary contribution from the reduction in surface tension. Our data also indicate that the surface-dilational viscosity of the oil monolayer is negligible and plays an insignificant role in calming the waves.

Internal Waves, Western Indian Ocean

NASA Image and Video Library

1991-12-01

STS044-79-077 (24 Nov.-1 Dec. 1991) --- This photograph, captured from the Earth-orbiting Space Shuttle Atlantis, shows sunglint pattern in the western tropical Indian Ocean. Several large internal waves reflect around a shallow area on the sea floor. NASA scientists studying the STS-44 photography believe the shallow area to be a sediment (a submerged mountain) on top of the Mascarene Plateau, located northeast of Madagascar at approximately 5.6 degrees south latitude and 55.7 degrees east longitude. Internal waves are similar to surface ocean waves, except that they travel inside the water column along the boundary between water layers of different density. At the surface, their passage is marked on the sea surface by bands of smooth and rough water. These bands appear in the sunglint pattern as areas of brighter or darker water. NASA scientists point out that, when the waves encounter an obstacle, such as a near-surface seamount, they bend or refract around the obstacle in the same manner as surface waves bend around an island or headland.

Fourier Transform Ultrasound Spectroscopy for the determination of wave propagation parameters.

PubMed

Pal, Barnana

2017-01-01

The reported results for ultrasonic wave attenuation constant (α) in pure water show noticeable inconsistency in magnitude. A "Propagating-Wave" model analysis of the most popular pulse-echo technique indicates that this is a consequence of the inherent wave propagation characteristics in a bounded medium. In the present work Fourier Transform Ultrasound Spectroscopy (FTUS) is adopted to determine ultrasonic wave propagation parameters, the wave number (k) and attenuation constant (α) at 1MHz frequency in tri-distilled water at room temperature (25°C). Pulse-echo signals obtained under same experimental conditions regarding the exciting input signal and reflecting boundary wall of the water container for various lengths of water columns are captured. The Fast Fourier Transform (FFT) components of the echo signals are taken to compute k, α and r, the reflection constant at the boundary, using Oak Ridge and Oxford method. The results are compared with existing literature values. Copyright © 2016 Elsevier B.V. All rights reserved.

Wave energy level and geographic setting correlate with Florida beach water quality.

PubMed

Feng, Zhixuan; Reniers, Ad; Haus, Brian K; Solo-Gabriele, Helena M; Kelly, Elizabeth A

2016-03-15

Many recreational beaches suffer from elevated levels of microorganisms, resulting in beach advisories and closures due to lack of compliance with Environmental Protection Agency guidelines. We conducted the first statewide beach water quality assessment by analyzing decadal records of fecal indicator bacteria (enterococci and fecal coliform) levels at 262 Florida beaches. The objectives were to depict synoptic patterns of beach water quality exceedance along the entire Florida shoreline and to evaluate their relationships with wave condition and geographic location. Percent exceedances based on enterococci and fecal coliform were negatively correlated with both long-term mean wave energy and beach slope. Also, Gulf of Mexico beaches exceeded the thresholds significantly more than Atlantic Ocean ones, perhaps partially due to the lower wave energy. A possible linkage between wave energy level and water quality is beach sand, a pervasive nonpoint source that tends to harbor more bacteria in the low-wave-energy environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Travelling-wave solutions of a weakly nonlinear two-dimensional higher-order Kadomtsev-Petviashvili dynamical equation for dispersive shallow-water waves

NASA Astrophysics Data System (ADS)

Seadawy, Aly R.

2017-01-01

The propagation of three-dimensional nonlinear irrotational flow of an inviscid and incompressible fluid of the long waves in dispersive shallow-water approximation is analyzed. The problem formulation of the long waves in dispersive shallow-water approximation lead to fifth-order Kadomtsev-Petviashvili (KP) dynamical equation by applying the reductive perturbation theory. By using an extended auxiliary equation method, the solitary travelling-wave solutions of the two-dimensional nonlinear fifth-order KP dynamical equation are derived. An analytical as well as a numerical solution of the two-dimensional nonlinear KP equation are obtained and analyzed with the effects of external pressure flow.

Water accounting and vulnerability evaluation (WAVE): considering atmospheric evaporation recycling and the risk of freshwater depletion in water footprinting.

PubMed

Berger, Markus; van der Ent, Ruud; Eisner, Stephanie; Bach, Vanessa; Finkbeiner, Matthias

2014-04-15

Aiming to enhance the analysis of water consumption and resulting consequences along the supply chain of products, the water accounting and vulnerability evaluation (WAVE) model is introduced. On the accounting level, atmospheric evaporation recycling within drainage basins is considered for the first time, which can reduce water consumption volumes by up to 32%. Rather than predicting impacts, WAVE analyzes the vulnerability of basins to freshwater depletion. Based on local blue water scarcity, the water depletion index (WDI) denotes the risk that water consumption can lead to depletion of freshwater resources. Water scarcity is determined by relating annual water consumption to availability in more than 11,000 basins. Additionally, WDI accounts for the presence of lakes and aquifers which have been neglected in water scarcity assessments so far. By setting WDI to the highest value in (semi)arid basins, absolute freshwater shortage is taken into account in addition to relative scarcity. This avoids mathematical artifacts of previous indicators which turn zero in deserts if consumption is zero. As illustrated in a case study of biofuels, WAVE can help to interpret volumetric water footprint figures and, thus, promotes a sustainable use of global freshwater resources.

Evolution of Nonlinear Internal Waves in China Seas

NASA Technical Reports Server (NTRS)

Liu, Antony K.; Hsu, Ming-K.; Liang, Nai K.

1997-01-01

Synthetic Aperture Radar (SAR) images from ERS-I have been used to study the characteristics of internal waves of Taiwan in the East China Sea, and east of Hainan Island in the South China Sea. Rank-ordered packets of internal solitons propagating shoreward from the edge of the continental shelf were observed in the SAR images. Based on the assumption of a semidiurnal tidal origin, the wave speed can be estimated and is consistent with the internal wave theory. By using the SAR images and hydrographic data, internal waves of elevation have been identified in shallow water due to a thicker mixed layer as compared with the bottom layer on the continental shelf. The generation mechanism includes the influences of the tide and the Kuroshio intrusion across the continental shelf for the formations of elevation internal waves. The effects of water depth on the evolution of solitons and wave packets are modeled by nonlinear Kortweg-deVries (KdV) type equation and linked to satellite image observations. The numerical calculations of internal wave evolution on the continental shelf have been performed and compared with the SAR observations. For a case of depression waves in deep water, the solitons first disintegrate into dispersive wave trains and then evolve to a packet of elevation waves in the shallow water area after they pass through a turning point of approximately equal layer depths has been observed in the SAR image and simulated by numerical model.

WAVE-E: The WAter Vapour European-Explorer Mission

NASA Astrophysics Data System (ADS)

Jimenez-LLuva, David; Deiml, Michael; Pavesi, Sara

2017-04-01

In the last decade, stratosphere-troposphere coupling processes in the Upper Troposphere Lower Stratosphere (UTLS) have been increasingly recognized to severely impact surface climate and high-impact weather phenomena. Weakened stratospheric circumpolar jets have been linked to worldwide extreme temperature and high-precipitation events, while anomalously strong stratospheric jets can lead to an increase in surface winds and tropical cyclone intensity. Moreover, stratospheric water vapor has been identified as an important forcing for global decadal surface climate change. In the past years, operational weather forecast and climate models have adapted a high vertical resolution in the UTLS region in order to capture the dynamical processes occurring in this highly stratified region. However, there is an evident lack of available measurements in the UTLS region to consistently support these models and further improve process understanding. Consequently, both the IPCC fifth assessment report and the ESA-GEWEX report 'Earth Observation and Water Cycle Science Priorities' have identified an urgent need for long-term observations and improved process understanding in the UTLS region. To close this gap, the authors propose the 'WAter Vapour European - Explorer' (WAVE-E) space mission, whose primary goal is to monitor water vapor in the UTLS at 1 km vertical, 25 km horizontal and sub-daily temporal resolution. WAVE-E consists of three quasi-identical small ( 500 kg) satellites (WAVE-E 1-3) in a constellation of Sun-Synchronous Low Earth Orbits, each carrying a limb sounding and cross-track scanning mid-infrared passive spectrometer (824 cm-1 to 829 cm-1). The core of the instruments builds a monolithic, field-widened type of Michelson interferometer without any moving parts, rendering it rigid and fault tolerant. Synergistic use of WAVE-E and MetOp-NG operational satellites is identified, such that a data fusion algorithm could provide water vapour profiles from the surface to the lower stratosphere. The mission strategy involves a pioneering launch of WAVE-E 1 followed by a joint launch of WAVE-E 2 and 3, minimizing both costs and risks as well as naturally offering a descoping option only affecting the temporal resolution of the mission. Assuming a nominal lifetime of five years for each satellite, the rough order of costs estimate amounts to 600M€ for the overall mission, while numerous cost reduction potentials remain open due to the early stage of instrument and mission design. The space mission concept 'WAVE-E' was developed by a team of 15 students with the support of two tutors at the Alpbach Summer School 2016, a ten-day design challenge organised by FFG and ESA and devoted to 'Satellite Observations of the Global Water Cycle'. The concept won the 'best science case' and 'best presentation' awards.

A unified spectral parameterization for wave breaking: From the deep ocean to the surf zone

NASA Astrophysics Data System (ADS)

Filipot, J.-F.; Ardhuin, F.

2012-11-01

A new wave-breaking dissipation parameterization designed for phase-averaged spectral wave models is presented. It combines wave breaking basic physical quantities, namely, the breaking probability and the dissipation rate per unit area. The energy lost by waves is first explicitly calculated in physical space before being distributed over the relevant spectral components. The transition from deep to shallow water is made possible by using a dissipation rate per unit area of breaking waves that varies with the wave height, wavelength and water depth. This parameterization is implemented in the WAVEWATCH III modeling framework, which is applied to a wide range of conditions and scales, from the global ocean to the beach scale. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Model errors are comparable to those of other specialized deep or shallow water parameterizations. This work shows that it is possible to have a seamless parameterization from the deep ocean to the surf zone.

Splash singularity for water waves.

PubMed

Castro, Angel; Córdoba, Diego; Fefferman, Charles L; Gancedo, Francisco; Gómez-Serrano, Javier

2012-01-17

We exhibit smooth initial data for the two-dimensional (2D) water-wave equation for which we prove that smoothness of the interface breaks down in finite time. Moreover, we show a stability result together with numerical evidence that there exist solutions of the 2D water-wave equation that start from a graph, turn over, and collapse in a splash singularity (self-intersecting curve in one point) in finite time.

Splash singularity for water waves

PubMed Central

Castro, Angel; Córdoba, Diego; Fefferman, Charles L.; Gancedo, Francisco; Gómez-Serrano, Javier

2012-01-01

We exhibit smooth initial data for the two-dimensional (2D) water-wave equation for which we prove that smoothness of the interface breaks down in finite time. Moreover, we show a stability result together with numerical evidence that there exist solutions of the 2D water-wave equation that start from a graph, turn over, and collapse in a splash singularity (self-intersecting curve in one point) in finite time. PMID:22219372

Imaging across the interface of small-scale breaking waves

NASA Astrophysics Data System (ADS)

Techet, Alexandra H.; Belden, Jesse L.

2007-11-01

Flow characteristics on both the air and water side of small scale spilling and plunging waves are investigated using fully time-resolved particle image velocimetry (PIV). PIV at 1000 frames per second (fps) is used to capture the flow field in both the air and water for waves generated by shoaling. Reynolds number of the waves is on the order of Re = 9x10^4 to 2x10^6, where Re = ρ√g 3̂μ, ρ is fluid density, μ is fluid dynamic viscosity, g is gravity, and λ is the characteristic wavelength of the breaking wave before breaking. Isopropyl alcohol is mixed with the distilled water in the tank to reduce surface tension and thus achieve plunging breakers on this scale. Flow in the water is seeded using conventional silver-coated hollow glass spheres, whereas the quiescent air side (i.e. no wind) is seeded using micro-air balloons with high stokes drag and thus long settling times. Imaging of both the air and water are performed simultaneously and advanced image processing is performed to determine the water surface location and to avoid surface tracking during PIV processing. Repeatable, coherent vortical structures are revealed on the air-side of the waves and are considered mechanisms for energy transfer across the interface.

The effect of ultrasonic waves on the nucleation of pure water and degassed water.

PubMed

Yu, Deyang; Liu, Baolin; Wang, Bochun

2012-05-01

In order to clarify the mechanism of nucleation of ice induced by ultrasound, ultrasonic waves have been applied to supercooled pure water and degassed water, respectively. For each experiment, water sample is cooled at a constant cooling rate of 0.15 °C/min and the ultrasonic waves are applied from the water temperature of 0 °C until the water in a sample vessel nucleates. This nucleation temperature is measured. The use of ultrasound increased the nucleation temperature of both degassed water and pure water. However, the undercooling temperature for pure water to nucleate is less than that of degassed water. It is concluded that cavitation and fluctuations of density, energy and temperature induced by ultrasound are factors that affect the nucleation of water. Cavitation is a major factor for sonocrystallisation of ice. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Wave power potential in Malaysian territorial waters

NASA Astrophysics Data System (ADS)

Asmida Mohd Nasir, Nor; Maulud, Khairul Nizam Abdul

2016-06-01

Up until today, Malaysia has used renewable energy technology such as biomass, solar and hydro energy for power generation and co-generation in palm oil industries and also for the generation of electricity, yet, we are still far behind other countries which have started to optimize waves for similar production. Wave power is a renewable energy (RE) transported by ocean waves. It is very eco-friendly and is easily reachable. This paper presents an assessment of wave power potential in Malaysian territorial waters including waters of Sabah and Sarawak. In this research, data from Malaysia Meteorology Department (MetMalaysia) is used and is supported by a satellite imaginary obtained from National Aeronautics and Space Administration (NASA) and Malaysia Remote Sensing Agency (ARSM) within the time range of the year 1992 until 2007. There were two types of analyses conducted which were mask analysis and comparative analysis. Mask analysis of a research area is the analysis conducted to filter restricted and sensitive areas. Meanwhile, comparative analysis is an analysis conducted to determine the most potential area for wave power generation. Four comparative analyses which have been carried out were wave power analysis, comparative analysis of wave energy power with the sea topography, hot-spot area analysis and comparative analysis of wave energy with the wind speed. These four analyses underwent clipping processes using Geographic Information System (GIS) to obtain the final result. At the end of this research, the most suitable area to develop a wave energy converter was found, which is in the waters of Terengganu and Sarawak. Besides that, it was concluded that the average potential energy that can be generated in Malaysian territorial waters is between 2.8kW/m to 8.6kW/m.

Do Heat Waves have an Impact on Terrestrial Water Storage?

NASA Astrophysics Data System (ADS)

Brena-Naranjo, A.; Teuling, R.; Pedrozo-Acuña, A.

2014-12-01

Recent works have investigated the impact of heat waves on the surface energy and carbon balance. However, less attention has been given to the impacts on terrestrial hydrology. During the summer of 2010, the occurrence of an exceptional heat wave affected severely the Northern Hemisphere. The extension (more than 2 million km2) and severity of this extreme event caused substantial ecosystem damage (more than 1 million ha of forest fires), economic and human losses (~500 billion USD and more than 17 million of indirect deaths, respectively). This work investigates for the first time the impacts of the 2010 summer heat wave on terrestrial water storage. Our study area comprises three different regions where air temperature records were established or almost established during the summer: Western Russia, the Middle East and Eastern Sahel. Anomalies of terrestrial water storage derived from the Gravity Recovery and Climate Experiment (GRACE) were used to infer water storage deficits during the 2003-2013 period. Our analysis shows that Russia experienced the most severe water storage decline, followed by the Middle East, whereas Eastern Sahel was not significantly affected. The impact of the heat wave was spatially uniform in Russia but highly variable in the Middle East, with the Northern part substantially more affected than the Southern region. Lag times between maxima air temperatures and lower water storage deficits for Russia and the Middle East were approximately two and seven months, respectively. The results suggest that the response of terrestrial water storage to heat waves is stronger in energy-limited environments than in water-limited regions. Such differences in the magnitude and timing between meteorological and hydrological extremes can be explained by the propagation time between atmospheric water demand and natural or anthropogenic sources of water storage.

2D instabilities of surface gravity waves on a linear shear current

NASA Astrophysics Data System (ADS)

Francius, Marc; Kharif, Christian

2016-04-01

Periodic 2D surface water waves propagating steadily on a rotational current have been studied by many authors (see [1] and references therein). Although the recent important theoretical developments have confirmed that periodic waves can exist over flows with arbitrary vorticity, their stability and their nonlinear evolution have not been much studied extensively so far. In fact, even in the rather simple case of uniform vorticity (linear shear), few papers have been published on the effect of a vertical shear current on the side-band instability of a uniform wave train over finite depth. In most of these studies [2-5], asymptotic expansions and multiple scales method have been used to obtain envelope evolution equations, which allow eventually to formulate a condition of (linear) instability to long modulational perturbations. It is noted here that this instability is often referred in the literature as the Benjamin-Feir or modulational instability. In the present study, we consider the linear stability of finite amplitude two-dimensional, periodic water waves propagating steadily on the free surface of a fluid with constant vorticity and finite depth. First, the steadily propagating surface waves are computed with steepness up to very close to the highest, using a Fourier series expansions and a collocation method, which constitutes a simple extension of Fenton's method [6] to the cases with a linear shear current. Then, the linear stability of these permanent waves to infinitesimal 2D perturbations is developed from the fully nonlinear equations in the framework of normal modes analysis. This linear stability analysis is an extension of [7] to the case of waves in the presence of a linear shear current and permits the determination of the dominant instability as a function of depth and vorticity for a given steepness. The numerical results are used to assess the accuracy of the vor-NLS equation derived in [5] for the characteristics of modulational instabilities due to resonant four-wave interactions, as well as to study the influence of vorticity and nonlinearity on the characteristics of linear instabilities due to resonant five-wave and six-wave interactions. Depending on the dimensionless depth, superharmonic instabilities due to five-wave interactions can become dominant with increasing positive vorticiy. Acknowledgments: This work was supported by the Direction Générale de l'Armement and funded by the ANR project n°. ANR-13-ASTR-0007. References [1] A. Constantin, Two-dimensionality of gravity water flows of constant non-zero vorticity beneath a surface wave train, Eur. J. Mech. B/Fluids, 2011, 30, 12-16. [2] R. S. Johnson, On the modulation of water waves on shear flows, Proc. Royal Soc. Lond. A., 1976, 347, 537-546. [3] M. Oikawa, K. Chow, D. J. Benney, The propagation of nonlinear wave packets in a shear flow with a free surface, Stud. Appl. Math., 1987, 76, 69-92. [4] A. I Baumstein, Modulation of gravity waves with shear in water, Stud. Appl. Math., 1998, 100, 365-90. [5] R. Thomas, C. Kharif, M. Manna, A nonlinear Schrödinger equation for water waves on finite depth with constant vorticity, Phys. Fluids, 2012, 24, 127102. [6] M. M Rienecker, J. D Fenton, A Fourier approximation method for steady water waves , J. Fluid Mech., 1981, 104, 119-137 [7] M. Francius, C. Kharif, Three-dimensional instabilities of periodic gravity waves in shallow water, J. Fluid Mech., 2006, 561, 417-437

Wave Transformation over a Fringing Coral Reef and the Importance of Low-Frequency Waves and Offshore Water Levels to Runup and Island Overtopping

NASA Astrophysics Data System (ADS)

Cheriton, O. M.; Storlazzi, C. D.; Rosenberger, K. J.

2016-02-01

Low-lying, reef-fringed islands are susceptible to sea-level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, wave gauges and a current meter were deployed for 5 months across two shore-normal transects on Roi-Namur, an atoll island in the Republic of the Marshall Islands. These observations captured two large wave events that had maximum wave heights greater than 6 m and peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly-skewed infragravity (0.04-0.004 Hz) and very low frequency (0.004-0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, exceeded 3.7 m at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3-hr time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along atoll and fringing reef-lined shorelines, such as island overwash. These observations lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of both extreme shoreline runup and island overwash, threatening the sustainability of these islands.

Observations of wave transformation over a fringing coral reef and the importance of low-frequency waves and offshore water levels to runup, overwash, and coastal flooding

NASA Astrophysics Data System (ADS)

Cheriton, Olivia M.; Storlazzi, Curt D.; Rosenberger, Kurt J.

2016-05-01

Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04-0.004 Hz) and very low frequency (0.004-0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.

Observations of wave transformation over a fringing coral reef and the importance of low-frequency waves and offshore water levels to runup, overwash, and coastal flooding

USGS Publications Warehouse

Cheriton, Olivia; Storlazzi, Curt; Rosenberger, Kurt

2016-01-01

Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04–0.004 Hz) and very low frequency (0.004–0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.

Evaluating tsunami hazards from debris flows

USGS Publications Warehouse

Watts, P.; Walder, J.S.; ,

2003-01-01

Debris flows that enter water bodies may have significant kinetic energy, some of which is transferred to water motion or waves that can impact shorelines and structures. The associated hazards depend on the location of the affected area relative to the point at which the debris flow enters the water. Three distinct regions (splash zone, near field, and far field) may be identified. Experiments demonstrate that characteristics of the near field water wave, which is the only coherent wave to emerge from the splash zone, depend primarily on debris flow volume, debris flow submerged time of motion, and water depth at the point where debris flow motion stops. Near field wave characteristics commonly may be used as & proxy source for computational tsunami propagation. This result is used to assess hazards associated with potential debris flows entering a reservoir in the northwestern USA. ?? 2003 Millpress,.

WaveAR: A software tool for calculating parameters for water waves with incident and reflected components

NASA Astrophysics Data System (ADS)

Landry, Blake J.; Hancock, Matthew J.; Mei, Chiang C.; García, Marcelo H.

2012-09-01

The ability to determine wave heights and phases along a spatial domain is vital to understanding a wide range of littoral processes. The software tool presented here employs established Stokes wave theory and sampling methods to calculate parameters for the incident and reflected components of a field of weakly nonlinear waves, monochromatic at first order in wave slope and propagating in one horizontal dimension. The software calculates wave parameters over an entire wave tank and accounts for reflection, weak nonlinearity, and a free second harmonic. Currently, no publicly available program has such functionality. The included MATLAB®-based open source code has also been compiled for Windows®, Mac® and Linux® operating systems. An additional companion program, VirtualWave, is included to generate virtual wave fields for WaveAR. Together, the programs serve as ideal analysis and teaching tools for laboratory water wave systems.

The laboratory investigation of surface envelope solitons: reflection from a vertical wall and collisions of solitons

NASA Astrophysics Data System (ADS)

Slunyaev, Alexey; Klein, Marco; Clauss, Günther F.

2016-04-01

Envelope soliton solutions are key elements governing the nonlinear wave dynamics within a simplified theory for unidirectional weakly modulated weakly nonlinear wave groups on the water surface. Within integrable models the solitons preserve their structure in collisions with other waves; they do not disperse and can carry energy infinitively long. Steep and short soliton-like wave groups have been shown to exist in laboratory tests [1] and, even earlier, in numerical simulations [2, 3]. Thus, long-living wave groups may play important role in the dynamics of intense sea waves and wave-structure interactions. The solitary wave groups may change the wave statistics and can be taken into account when developing approaches for the deterministic forecasting of dangerous waves, including so-called rogue waves. An experimental campaign has been conducted in the wave basin of the Technical University of Berlin on simulations of intense solitary wave groups. The first successful experimental observation of intense envelope solitons took place in this facility [1]. The new experiments aimed at following main goals: 1) to reproduce intense envelope solitons with different carrier wave lengths; 2) to estimate the rate of envelope soliton dissipation; 3) to consider the reflection of envelope solitons on a vertical wall; 4) to consider head-on collisions of envelope solitons, and 5) to consider overtaking interactions of envelope solitons. Up to 9 wave gauges were used in each experimental run, which enabled registration of the surface movement at different distances from the wavemaker, at different locations across the wave flume and near the wall. Besides surface displacements, the group envelope shapes were directly recorded, with use of phase shifts applied to the modulated waves generated by the wavemaker. [1] A. Slunyaev, G.F. Clauss, M. Klein, M. Onorato, Simulations and experiments of short intense envelope solitons of surface water waves. Phys. Fluids 25, 067105 (2013). [2] A.I. Dyachenko, V.E. Zakharov, On the formation of freak waves on the surface of deep water. JETP Lett. 88, 307 (2008). [3] A.V. Slunyaev, Numerical simulation of "limiting" envelope solitons of gravity waves on deep water. JETP 109, 676 (2009).

Revisiting the anisotropy of metamaterials for water waves

NASA Astrophysics Data System (ADS)

Maurel, A.; Marigo, J.-J.; Cobelli, P.; Petitjeans, P.; Pagneux, V.

2017-10-01

We establish, both theoretically and experimentally, that metamaterials for water waves reach a much higher degree of anisotropy than the one predicted using the analogy between water waves and their electromagnetic or acoustic counterparts. This is due to the fact that this analogy, based on the two-dimensional shallow water approximation, is unable to account for the three-dimensional near field effects in the water depth. To properly capture these effects, we homogenize the fully three-dimensional problem and show that a subwavelength layered structuration of the bathymetry produces significant anisotropic parameters in the shallow water regime. Furthermore, we extend the validity of the homogenized prediction by proposing an empirical anisotropic version of the dispersion relation.

Shallow-water seismoacoustic noise generated by tropical storms Ernesto and Florence.

PubMed

Traer, James; Gerstoft, Peter; Bromirski, Peter D; Hodgkiss, William S; Brooks, Laura A

2008-09-01

Land-based seismic observations of double frequency (DF) microseisms generated during tropical storms Ernesto and Florence are dominated by signals in the 0.15-0.5 Hz band. In contrast, data from sea floor hydrophones in shallow water (70 m depth, 130 km off the New Jersey coast) show dominant signals in the ocean gravity-wave frequency band, 0.02-0.18 Hz, and low amplitudes from 0.18 to 0.3 Hz, suggesting significant opposing wave components necessary for DF microseism generation were negligible at the site. Florence produced large waves over deep water while Ernesto only generated waves in coastal regions, yet both storms produced similar spectra. This suggests near-coastal shallow water as the dominant region for observed microseism generation.

The characteristics and dynamics of wave-driven flow across a platform coral reef in the Red Sea

NASA Astrophysics Data System (ADS)

Lentz, S. J.; Churchill, J. H.; Davis, K. A.; Farrar, J. T.; Pineda, J.; Starczak, V.

2016-02-01

Current dynamics across a platform reef in the Red Sea near Jeddah, Saudi Arabia, are examined using 18 months of current profile, pressure, surface wave, and wind observations. The platform reef is 700 m long, 200 m across with spatial and temporal variations in water depth over the reef ranging from 0.6 to 1.6 m. Surface waves breaking at the seaward edge of the reef cause a 2-10 cm setup of sea level that drives cross-reef currents of 5-20 cm s-1. Bottom stress is a significant component of the wave setup balance in the surf zone. Over the reef flat, where waves are not breaking, the cross-reef pressure gradient associated with wave setup is balanced by bottom stress. The quadratic drag coefficient for the depth-average flow decreases with increasing water depth from Cda = 0.17 in 0.4 m of water to Cda = 0.03 in 1.2 m of water. The observed dependence of the drag coefficient on water depth is consistent with open-channel flow theory and a hydrodynamic roughness of zo = 0.06 m. A simple one-dimensional model driven by incident surface waves and wind stress accurately reproduces the observed depth-averaged cross-reef currents and a portion of the weaker along-reef currents over the focus reef and two other Red Sea platform reefs. The model indicates the cross-reef current is wave forced and the along-reef current is partially wind forced.

Acceleration Measurements During Landings of a 1/5.5-Size Dynamic Model of the Columbia XJL-1 Amphibian in Smooth Water and in Waves: Langley Tank Model 208M, TED No. NACA 2336

NASA Technical Reports Server (NTRS)

Clement, Eugene P.; Havens, Robert F.

1947-01-01

A 1/5.5-size powered dynamic model of the Columbia XJL-1 amphibian was landed in Langley tank no. 1 in smooth water and in oncoming waves of heights from 2.1 feet to 6.4 feet (full-size) and lengths from 50 feet to 264 feet (full-size). The motions and the vertical accelerations of the model were continuously recorded. The greatest vertical acceleration measured during the smooth-water landings was 3.1g. During landings in rough water the greatest vertical acceleration measured was 15.4g, for a landing in 6.4-foot by 165-foot waves. The impact accelerations increased with increase in wave height and, in general, decreased with increase in wave length. During the landings in waves the model bounced into the air at stalled attitudes at speeds below flying speed. The model trimmed up to the mechanical trim stop (20 deg) during landings in waves of heights greater than 2.0 feet. Solid water came over the bow and damaged the propeller during one landing in 6.4-foot waves. The vertical acceleration coefficients at first impact from the tank tests of a 1/5.5-size model were in fair agreement with data obtained at the Langley impact basin during tests of a 1/2-size model of the hull.

Wave-formed structures and paleoenvironmental reconstruction

USGS Publications Warehouse

Clifton, H.E.; Dingler, J.R.

1984-01-01

Wave-formed sedimentary structures can be powerful interpretive tools because they reflect not only the velocity and direction of the oscillatory currents, but also the length of the horizontal component of orbital motion and the presence of velocity asymmetry within the flow. Several of these aspects can be related through standard wave theories to combinations of wave dimensions and water depth that have definable natural limits. For a particular grain size, threshold of particle movement and that of conversion from a rippled to flat bed indicate flow-velocity limits. The ratio of ripple spacing to grain size provides an estimate of the length of the near-bottom orbital motion. The degree of velocity asymmetry is related to the asymmetry of the bedforms, though it presently cannot be estimated with confidence. A plot of water depth versus wave height (h-H diagram) provides a convenient approach for showing the combination of wave parameters and water depths capable of generating any particular structure in sand of a given grain size. Natural limits on wave height and inferences or assumptions regarding either water depth or wave period based on geologic evidence allow refinement of the paleoenvironmental reconstruction. The assumptions and the degree of approximation involved in the different techniques impose significant constraints. Inferences based on wave-formed structures are most reliable when they are drawn in the context of other evidence such as the association of sedimentary features or progradational sequences. ?? 1984.

Experimental study on the evolution of Peregrine breather with uniform-depth adverse currents

NASA Astrophysics Data System (ADS)

Liao, B.; Ma, Y.; Ma, X.; Dong, G.

2018-05-01

A series of laboratory experiments were performed to study the evolution of Peregrine breather (PB) in a wave flume in finite depth, and wave trains were initially generated in a region of quiescent water and then propagated into an adverse current region for which the current velocity strength gradually increased from zero to an approximately stable value. The PB is often considered as a prototype of oceanic freak waves that can focus wave energy into a single wave packet. In the experiment, the cases were selected with the relative water depths k0h (k0 is the wave number in quiescent water and h is the water depth) varying from 3.11 through 8.17, and the initial wave steepness k0a0 (a0 is the background wave amplitude) ranges between 0.065 and 0.120. The experimental results show the persistence of the breather evolution dynamics even in the presence of strong opposing currents. We have shown that the characteristic spectrum of the PB persists even on strong currents, thus making it a viable characteristic for prediction of freak waves. It was also found that the adverse currents tend to shift the focusing point upstream compared to the cases without currents. Furthermore, it was found that uniform-depth adverse currents can reduce the breather extension in time domain.

Wind Wave Behavior in Fetch and Depth Limited Estuaries

NASA Astrophysics Data System (ADS)

Karimpour, Arash; Chen, Qin; Twilley, Robert R.

2017-01-01

Wetland dominated estuaries serve as one of the most productive natural ecosystems through their ecological, economic and cultural services, such as nursery grounds for fisheries, nutrient sequestration, and ecotourism. The ongoing deterioration of wetland ecosystems in many shallow estuaries raises concerns about the contributing erosive processes and their roles in restraining coastal restoration efforts. Given the combination of wetlands and shallow bays as landscape components that determine the function of estuaries, successful restoration strategies require knowledge of wind wave behavior in fetch and depth limited water as a critical design feature. We experimentally evaluate physics of wind wave growth in fetch and depth limited estuaries. We demonstrate that wave growth rate in shallow estuaries is a function of wind fetch to water depth ratio, which helps to develop a new set of parametric wave growth equations. We find that the final stage of wave growth in shallow estuaries can be presented by a product of water depth and wave number, whereby their product approaches 1.363 as either depth or wave energy increases. Suggested wave growth equations and their asymptotic constraints establish the magnitude of wave forces acting on wetland erosion that must be included in ecosystem restoration design.

An Experiment on Two-Dimensional Interaction of Solitary Waves in Shallow Water System

NASA Astrophysics Data System (ADS)

Tsuji, Hidekazu; Yufu, Kei; Marubayashi, Kenji

2012-11-01

The dynamics of solitary waves in horizontally two-dimensional region is not yet well understood. Recently two-dimensional soliton interaction of Kadmotsetv-Petviashvili (KP) equation which describes the weakly nonlinear long wave in shallow water system has been theoretically studied (e.g. Kodama (2010)). It is clarified that the ``resonant'' interaction which forms Y-shaped triad can be described by exact solution. Li et al. (2011) experimentally studied the reflection of solitary wave at the wall and verified the theory of KP equation. To investigate more general interaction process, an experiment in wave tank using two wave makers which are controlled independently is carried out. The wave tank is 4 m in length and 3.6 m in width. The depth of the water is about 8cm. The wavemakers, which are piston-type and have board about 1.5 m in length, can produce orderly solitary wave which amplitude is 1.0-3.5 cm. We observe newly generated solitary wave due to interaction of original solitary waves which have different amplitude and/or propagation direction. The results are compared with the aforementioned theory of KP equation.

Wind Wave Behavior in Fetch and Depth Limited Estuaries

PubMed Central

Karimpour, Arash; Chen, Qin; Twilley, Robert R.

2017-01-01

Wetland dominated estuaries serve as one of the most productive natural ecosystems through their ecological, economic and cultural services, such as nursery grounds for fisheries, nutrient sequestration, and ecotourism. The ongoing deterioration of wetland ecosystems in many shallow estuaries raises concerns about the contributing erosive processes and their roles in restraining coastal restoration efforts. Given the combination of wetlands and shallow bays as landscape components that determine the function of estuaries, successful restoration strategies require knowledge of wind wave behavior in fetch and depth limited water as a critical design feature. We experimentally evaluate physics of wind wave growth in fetch and depth limited estuaries. We demonstrate that wave growth rate in shallow estuaries is a function of wind fetch to water depth ratio, which helps to develop a new set of parametric wave growth equations. We find that the final stage of wave growth in shallow estuaries can be presented by a product of water depth and wave number, whereby their product approaches 1.363 as either depth or wave energy increases. Suggested wave growth equations and their asymptotic constraints establish the magnitude of wave forces acting on wetland erosion that must be included in ecosystem restoration design. PMID:28098236

Wind Wave Behavior in Fetch and Depth Limited Estuaries.

PubMed

Karimpour, Arash; Chen, Qin; Twilley, Robert R

2017-01-18

Wetland dominated estuaries serve as one of the most productive natural ecosystems through their ecological, economic and cultural services, such as nursery grounds for fisheries, nutrient sequestration, and ecotourism. The ongoing deterioration of wetland ecosystems in many shallow estuaries raises concerns about the contributing erosive processes and their roles in restraining coastal restoration efforts. Given the combination of wetlands and shallow bays as landscape components that determine the function of estuaries, successful restoration strategies require knowledge of wind wave behavior in fetch and depth limited water as a critical design feature. We experimentally evaluate physics of wind wave growth in fetch and depth limited estuaries. We demonstrate that wave growth rate in shallow estuaries is a function of wind fetch to water depth ratio, which helps to develop a new set of parametric wave growth equations. We find that the final stage of wave growth in shallow estuaries can be presented by a product of water depth and wave number, whereby their product approaches 1.363 as either depth or wave energy increases. Suggested wave growth equations and their asymptotic constraints establish the magnitude of wave forces acting on wetland erosion that must be included in ecosystem restoration design.

On the parameters influencing air-water gas exchange

NASA Astrophysics Data System (ADS)

JäHne, Bernd; Münnich, Karl Otto; BöSinger, Rainer; Dutzi, Alfred; Huber, Werner; Libner, Peter

1987-02-01

Detailed gas exchange measurements from two circular and one linear wind/wave tunnels are presented. Heat, He, CH4, CO2, Kr, and Xe have been used as tracers. The experiments show the central importance of waves for the water-side transfer process. With the onset of waves the Schmidt number dependence of the transfer velocity k changes from k ∝ Sc-⅔ to k ∝ Sc-½indicating a change in the boundary conditions at the surface. Moreover, energy put into the wave field by wind is transferred to near-surface turbulence enhancing gas transfer. The data show that the mean square slope of the waves is the best parameter to characterize the free wavy surface with respect to water-side transfer processes.

Winds, waves and shorelines from ancient martian seas

NASA Astrophysics Data System (ADS)

Banfield, Don; Donelan, Mark; Cavaleri, Luigi

2015-04-01

We consider under what environmental conditions water waves (and thus eventually shorelines) should be expected to be produced on hypothetical ancient martian seas and lakes. For winds and atmospheric pressures that are too small, no waves should be expected, and thus no shorelines. If the winds and atmospheric pressure are above some threshold, then waves can be formed, and shorelines are possible. We establish these criteria separating conditions under which waves will or will not form on an ancient martian open body of water. We consider not only atmospheric pressure and wind, but also temperature and salinity, but find these latter effects to be secondary. The normal criterion for the onset of water waves under terrestrial conditions is extended to recognize the greater atmospheric viscous boundary layer depth for low atmospheric pressures. We used terrestrial wave models to predict the wave environment expected for reasonable ranges of atmospheric pressure and wind for end-member cases of ocean salinity. These models were modified only to reflect the different fluids considered at Mars, the different martian surface gravity, and the varying atmospheric pressure, wind and fetch. The models were favorably validated against one another, and also against experiments conducted in a wave tank in a pressure controlled wind tunnel (NASA Ames MARSWIT). We conclude that if wave-cut shorelines can be confirmed on Mars, this can constrain the range of possible atmospheric pressures and wind speeds that could have existed when the open water was present on Mars.

Influence of water conductivity on shock waves generated by underwater electrical wire explosion

NASA Astrophysics Data System (ADS)

Liu, Ben; Wang, Deguo; Guo, Yanbao

2018-01-01

The new application of electrical explosion of wire (EEW) used in petroleum industry is to enhance oil recovery (EOR). Because of the complex environment underground, the effect of underground water conductivity on EEW should be considered. This work describes the effect of water conductivities on discharge current, voltage and shock waves. It was found that the effect of water conductivity contains two parts. One is the shunt effect of saline water, which can be considered as a parallel load with the copper wire between the electrodes connected to the discharge circuit. The peak pressure of shock waves are gradually decrease with the increase of water conductivity. The other is the current loss through saline water directly to the ground ends without flowing through the electrodes. The shunt effect is the main factor affecting the wire discharge process. As the charging voltage increased, the energy loss caused by these two parts are all reduced. These indicate that increasing the charging voltage to a certain value will increase the energy efficiency to generate a more powerful shock waves in conductive water.

Influence of wave action on the partitioning and transport of unattached and floc-associated bacteria in fresh water.

PubMed

Sousa, Andrew J; Droppo, Ian G; Liss, Steven N; Warren, Lesley; Wolfaardt, Gideon

2015-08-01

The dynamic interaction of bacteria within bed sediment and suspended sediment (i.e., floc) in a wave-dominated beach environment was assessed using a laboratory wave flume. The influence of shear stress (wave energy) on bacterial concentrations and on the partitioning and transport of unattached and floc-associated bacteria was investigated. The study showed that increasing wave energy (0.60 and 5.35 N/s) resulted in a 0.5 to 1.5 log increase in unattached cells of the test bacterium Pseudomonas sp. strain CTO7::gfp-2 in the water column. There was a positive correlation between the bacterial concentrations in water and the total suspended solids, with the latter increasing from values of near 0 to up to 200 mg/L over the same wave energy increase. The median equivalent spherical diameter of flocs in suspension also increased by an order of magnitude in all experimental trials. Under both low (0.60 N/s) and high (5.35 N/s) energy regime, bacteria were shown to preferentially associate with flocs upon cessation of wave activity. The results suggest that collecting water samples during periods of low wave action for the purpose of monitoring the microbiological quality of water may underestimate bacterial concentrations partly because of an inability to account for the effect of shear stress on the erosion and mobilization of bacteria from bed sediment to the water column. This highlights the need to develop a more comprehensive beach analysis strategy that not only addresses presently uncharacterized shores and sediments but also recognizes the importance of eroded flocs as a vector for the transport of bacteria in aquatic environments.

A Powerful Method of Measuring Sea Wave Spectra and their Direction

NASA Astrophysics Data System (ADS)

Blasi, Christoph; Mai, Stephan; Wilhelmi, Jens; Zenz, Theodor; Barjenbruch, Ulrich

2014-05-01

Besides the need of precise measurements of water levels of the sea, there is an increasing demand for assessing waves in height and direction for different purposes like sea-wave modelling and coastal engineering. The design of coastal structures such as piles, breakwaters, and offshore structures like wind farms must take account of the direction of the impacting waves. To date, records of wave directions are scarce. The reason for this might be the high costs of purchasing and operating such measuring devices. These are usually buoys, which require regular maintenance. Against this background, the German Federal Institute of Hydrology (BfG) developed a low-cost directional sea-wave monitoring system that is based on commercially available liquid-level radar sensors. These sensors have the advantage that they have no contact to the fluid, i.e. the corrosive sea water. The newly developed device was tested on two sites. One is the tide gauge 'Borkum Südstrand' that is located in the southern North Sea off the island of Borkum. The other one is the 'Research Platform FINO1' approximately 45 km north of the island of Borkum. The main focus of these tests is the comparison of the data measured by the radar-based system with those of a conventional Directional Wave Rider Buoy. The general conditions at the testing sites are good for the tests. At the tide gauge 'Borkum Südstrand' waves propagate in different directions, strongly influenced by the morphological conditions like shallow waters of the Wadden Seas and the coast of the island of Borkum. Whereas on the open sea, at the site FINO1, the full physical conditions of the sea state, like heavy storms etc. play an important role. To determine and measure the direction of waves, the device has to be able to assess the wave movements in two dimensions. Therefore, an array of several radar sensors is required. Radar sensors are widely used and well established in measuring water levels, e.g. in tanks and basins. They operate by emitting a chain of electromagnetic pulses at a frequency of 26 GHz twice per second and, in turn, detect the backscatter information from the water surface. As the travelling time of each pulse is proportional to the distance between water surface and sensor, the height of the water surface can be easily calculated. To obtain the directional information of the sea state, all four radar sensors in the array have to collect simultaneously the wave profiles at fixed points. The Wave Rider Buoy works in a completely different way. Here, the wave height is calculated by the double integration of the measured vertical acceleration. By correlating the three-dimensional motion data, which are gained from gravity-stabilized vertical and horizontal accelerometers, the directional wave spectrum can be derived. Data of both devices were collected and analysed. During the hurricane Xaver, extreme water levels and heavy sea hit the North Sea coast on 5 and 6 December 2013. The radar array at the testing site FINO1 measured wave heights in the order of 15.5 meters. Furthermore, it was possible to detect significant wave heights, the mean wave direction, and the spread of the sea state. For the first time the accuracy of the wave height distribution could be determined as well.

Identification and classification of very low frequency waves on a coral reef flat

USGS Publications Warehouse

Gawehn, Matthijs; van Dongeran, Ap; van Rooijen, Arnold; Storlazzi, Curt; Cheriton, Olivia; Reniers, Ad

2016-01-01

Very low frequency (VLF, 0.001–0.005 Hz) waves are important drivers of flooding of low-lying coral reef-islands. In particular, VLF wave resonance is known to drive large wave runup and subsequent overwash. Using a 5 month data set of water levels and waves collected along a cross-reef transect on Roi-Namur Island in the Republic of the Marshall Islands, the observed VLF motions were categorized into four different classes: (1) resonant, (2) (nonresonant) standing, (3) progressive-growing, and (4) progressive-dissipative waves. Each VLF class is set by the reef flat water depth and, in the case of resonance, the incident-band offshore wave period. Using an improved method to identify VLF wave resonance, we find that VLF wave resonance caused prolonged (∼0.5–6.0 h), large-amplitude water surface oscillations at the inner reef flat ranging in wave height from 0.14 to 0.83 m. It was induced by relatively long-period, grouped, incident-band waves, and occurred under both storm and nonstorm conditions. Moreover, observed resonant VLF waves had nonlinear, bore-like wave shapes, which likely have a larger impact on the shoreline than regular, sinusoidal waveforms. As an alternative technique to the commonly used Fast Fourier Transformation, we propose the Hilbert-Huang Transformation that is more computationally expensive but can capture the wave shape more accurately. This research demonstrates that understanding VLF waves on reef flats is important for evaluating coastal flooding hazards.

Identification and classification of very low frequency waves on a coral reef flat

NASA Astrophysics Data System (ADS)

Gawehn, Matthijs; van Dongeren, Ap; van Rooijen, Arnold; Storlazzi, Curt D.; Cheriton, Olivia M.; Reniers, Ad

2016-10-01

Very low frequency (VLF, 0.001-0.005 Hz) waves are important drivers of flooding of low-lying coral reef-islands. In particular, VLF wave resonance is known to drive large wave runup and subsequent overwash. Using a 5 month data set of water levels and waves collected along a cross-reef transect on Roi-Namur Island in the Republic of the Marshall Islands, the observed VLF motions were categorized into four different classes: (1) resonant, (2) (nonresonant) standing, (3) progressive-growing, and (4) progressive-dissipative waves. Each VLF class is set by the reef flat water depth and, in the case of resonance, the incident-band offshore wave period. Using an improved method to identify VLF wave resonance, we find that VLF wave resonance caused prolonged (˜0.5-6.0 h), large-amplitude water surface oscillations at the inner reef flat ranging in wave height from 0.14 to 0.83 m. It was induced by relatively long-period, grouped, incident-band waves, and occurred under both storm and nonstorm conditions. Moreover, observed resonant VLF waves had nonlinear, bore-like wave shapes, which likely have a larger impact on the shoreline than regular, sinusoidal waveforms. As an alternative technique to the commonly used Fast Fourier Transformation, we propose the Hilbert-Huang Transformation that is more computationally expensive but can capture the wave shape more accurately. This research demonstrates that understanding VLF waves on reef flats is important for evaluating coastal flooding hazards.

Observations of Surfzone Albedo

NASA Astrophysics Data System (ADS)

Sinnett, G.; Feddersen, F.

2014-12-01

The surfzone environment (where waves break) contains several unique and previously unconsidered processes that affect the heat budget. Entering short-wave radiation is a dominant term in both shelf and surfzone heat budgets. In contrast to the shelf, however, depth limited wave breaking in the surfzone generates spray, whitewater and suspended sediments, elevating the surface albedo (ratio of reflected to incident short-wave radiation). Elevated albedo reduces the level of solar short-wave radiation entering the water, potentially resulting in less heating. Additionally, surfzone water quality is often impacted by fecal bacteria contamination. As bacteria mortality is related to short-wave solar radiation, elevated surfzone albedo could reduce pathogen mortality, impacting human health. Albedo in the open ocean has been frequently studied and parameterizations often consider solar zenith angle, wind speed and ocean chlorophyll concentration, producing albedo values typically near 0.06. However, surfzone albedo observations have been extremely sparse, yet show depth limited wave breaking may increase the albedo by nearly a factor of 10 up to 0.5. Here, we present findings from a field study at the Scripps Institution of Oceanography pier to observe the affect of waves on surfzone albedo. Concurrent measurements were taken with a four-way radiometer (to measure both downwelling and upwelling short-wave and long wave radiation) mounted above the surfzone. A co-located GoPro camera was used to relate visual aspects of the surfzone to measured reflectance, and wave height and period were observed with a bottom mounted pressure sensor in 5 m water depth just outside the surfzone. Wind speed and direction were observed on the pier 10 m above the water surface. Here, we will examine the surfzone albedo dependence on surfzone parameters, such as wave height.

Tsunamis generated by long and thin granular landslides in a large flume

NASA Astrophysics Data System (ADS)

Miller, Garrett S.; Andy Take, W.; Mulligan, Ryan P.; McDougall, Scott

2017-01-01

In this experimental study, granular material is released down slope to investigate landslide-generated waves. Starting with a known volume and initial position of the landslide source, detailed data are obtained on the velocity and thickness of the granular flow, the shape and location of the submarine landslide deposit, the amplitude and shape of the near-field wave, the far-field wave evolution, and the wave runup elevation on a smooth impermeable slope. The experiments are performed on a 6.7 m long 30° slope on which gravity accelerates the landslides into a 2.1 m wide and 33.0 m long wave flume that terminates with a 27° runup ramp. For a fixed landslide volume of 0.34 m3, tests are conducted in a range of still water depths from 0.05 to 0.50 m. Observations from high-speed cameras and measurements from wave probes indicate that the granular landslide moves as a long and thin train of material, and that only a portion of the landslide (termed the "effective mass") is engaged in activating the leading wave. The wave behavior is highly dependent on the water depth relative to the size of the landslide. In deeper water, the near-field wave behaves as a stable solitary-like wave, while in shallower water, the wave behaves as a breaking dissipative bore. Overall, the physical model observations are in good agreement with the results of existing empirical equations when the effective mass is used to predict the maximum near-field wave amplitude, the far-field amplitude, and the runup of tsunamis generated by granular landslides.

Lidar Observations of Wave Shape

NASA Astrophysics Data System (ADS)

Brodie, K. L.; Raubenheimer, B.; Spore, N.; Gorrell, L.; Slocum, R. K.; Elgar, S.

2016-02-01

As waves propagate across the inner-surf zone, through a shorebreak, to the swash, their shapes can evolve rapidly, particularly if there are large changes in water depth over a wavelength. As wave shapes evolve, the time history of near-bed wave-orbital velocities also changes. Asymmetrical near-bed velocities result in preferential directions for sediment transport, and spatial variations in asymmetries can lead to morphological evolution. Thus, understanding and predicting wave shapes in the inner-surf and swash zones is important to improving sediment transport predictions. Here, rapid changes in wave shape, quantified by 3rd moments (skewness and asymmetry) of the sea-surface elevation time series, were observed on a sandy Atlantic Ocean beach near Duck, NC using terrestrial lidar scanners that measure the elevation of the water surface along a narrow cross-shore transect with high spatial [O(1 cm)] and temporal [O(0.5 s)] resolution. The terrestrial lidar scanners were mounted on a tower on the beach dune (about 8 m above the water surface) and on an 8-m tall amphibious tripod [the Coastal Research Amphibious Buggy (CRAB)]. Observations with the dune lidar are used to investigate how bulk wave shape parameters such as wave skewness and asymmetry, and the ratio of wave height to water depth (gamma) vary with beach slope, tide level, and offshore wave conditions. Observations with the lidar mounted on the CRAB are used to investigate the evolution of individual waves propagating across the surf zone and shorebreak to the swash. For example, preliminary observations from the CRAB include a wave that appeared to shoal and then "pitch" backwards immediately prior to breaking and running up the beach. Funded by the USACE Coastal Field Data Collection Program, ASD(R&E), and ONR.

Equatorial Magnetohydrodynamic Shallow Water Waves in the Solar Tachocline

NASA Astrophysics Data System (ADS)

Zaqarashvili, Teimuraz

2018-03-01

The influence of a toroidal magnetic field on the dynamics of shallow water waves in the solar tachocline is studied. A sub-adiabatic temperature gradient in the upper overshoot layer of the tachocline causes significant reduction of surface gravity speed, which leads to trapping of the waves near the equator and to an increase of the Rossby wave period up to the timescale of solar cycles. Dispersion relations of all equatorial magnetohydrodynamic (MHD) shallow water waves are obtained in the upper tachocline conditions and solved analytically and numerically. It is found that the toroidal magnetic field splits equatorial Rossby and Rossby-gravity waves into fast and slow modes. For a reasonable value of reduced gravity, global equatorial fast magneto-Rossby waves (with the spatial scale of equatorial extent) have a periodicity of 11 years, matching the timescale of activity cycles. The solutions are confined around the equator between latitudes ±20°–40°, coinciding with sunspot activity belts. Equatorial slow magneto-Rossby waves have a periodicity of 90–100 yr, resembling the observed long-term modulation of cycle strength, i.e., the Gleissberg cycle. Equatorial magneto-Kelvin and slow magneto-Rossby-gravity waves have the periodicity of 1–2 years and may correspond to observed annual and quasi-biennial oscillations. Equatorial fast magneto-Rossby-gravity and magneto-inertia-gravity waves have periods of hundreds of days and might be responsible for observed Rieger-type periodicity. Consequently, the equatorial MHD shallow water waves in the upper overshoot tachocline may capture all timescales of observed variations in solar activity, but detailed analytical and numerical studies are necessary to make a firm conclusion toward the connection of the waves to the solar dynamo.

Modeling of wave-coherent pressures in the turbulent boundary layer above water waves

NASA Technical Reports Server (NTRS)

Papadimitrakis, Yiannis ALEX.

1988-01-01

The behavior of air pressure fluctuations induced by progressive water waves generated mechanically in a laboratory tank was simulated by solving a modified Orr-Sommerfeld equation in a transformed Eulerian wave-following frame of reference. Solution is obtained by modeling the mean and wave-coherent turbulent Reynolds stresses, the behavior of which in the turbulent boundary layer above the waves was simulated using a turbulent kinetic energy-dissipation model, properly modified to account for free-surface proximity and favorable pressure gradient effects. The distribution of both the wave-coherent turbulent Reynolds stress and pressure amplitudes and their corresponding phase lags was found to agree reasonably well with available laboratory data.

Spatial Statistics of Deep-Water Ambient Noise; Dispersion Relations for Sound Waves and Shear Waves

DTIC Science & Technology

2015-09-30

propagation in very fine-grained sediments (silt and clay ). OBJECTIVES 1) The scientific objective of the deep-water ambient noise research is to...forces in silts and clays and the role they play in controlling wave speeds and attenuations. On a 2 quantum mechanical level, these forces are... clays . APPROACH 1) Deep-water ambient noise Three deep-diving, autonomous instrument platforms, known as Deep Sound I, II, & III, have been

Cross-Shore Exchange on Natural Beaches

DTIC Science & Technology

2014-09-01

87   Figure 2.   Wave conditions measured by the ADCP in 13 m water depth of (a) root- mean-square wave height Hrms...horizontal velocity, Umean, measured in the reference level, ∑Tsig,pulse T3−hour ∑Tsig,pulse T3−hour xi (e) local water depth, h, and (f) local root...mean-square wave height normalized by the local water depth, Hrms/h, measured by ADCPin (blue) and ADCPout (red) during the 3HRLTs. Colored lines

Laboratory Characterization of Talley Brick

DTIC Science & Technology

2011-08-01

specimen’s wet, bulk, or “as-tested” density. Results from these determinations are provided in Table 1. Measurements of posttest water content1...ASTM 2005d). Based on the appropriate values of posttest water content, wet density, and an assumed grain density of 2.89 Mg/m3, values of dry... Posttest Axial P Radial P Axial S Radial S Wet Water Dry Degree of ’Wave ’Wave ’Wave \\Vave Test Density Conte-nt, Density, Porosity, Saturation

Observation of skull-guided acoustic waves in a water-immersed murine skull using optoacoustic excitation

NASA Astrophysics Data System (ADS)

Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

2017-02-01

The skull bone, a curved solid multilayered plate protecting the brain, constitutes a big challenge for the use of ultrasound-mediated techniques in neuroscience. Ultrasound waves incident from water or soft biological tissue are mostly reflected when impinging on the skull. To this end, skull properties have been characterized for both high-intensity focused ultrasound (HIFU) operating in the narrowband far-field regime and optoacoustic imaging applications. Yet, no study has been conducted to characterize the near-field of water immersed skulls. We used the thermoelastic effect with a 532 nm pulsed laser to trigger a wide range of broad-band ultrasound modes in a mouse skull. In order to capture the waves propagating in the near-field, a thin hydrophone was scanned in close proximity to the skull's surface. While Leaky pseudo-Lamb waves and grazing-angle bulk water waves are clearly visible in the spatio-temporal data, we were only able to identify skull-guided acoustic waves after dispersion analysis in the wavenumber-frequency space. The experimental data was found to be in a reasonable agreement with a flat multilayered plate model.

Observation of Mountain Lee Waves with MODIS NIR Column Water Vapor

NASA Technical Reports Server (NTRS)

Lyapustin, A.; Alexander, M. J.; Ott, L.; Molod, A.; Holben, B.; Susskind, J.; Wang, Y.

2014-01-01

Mountain lee waves have been previously observed in data from the Moderate Resolution Imaging Spectroradiometer (MODIS) "water vapor" 6.7 micrometers channel which has a typical peak sensitivity at 550 hPa in the free troposphere. This paper reports the first observation of mountain waves generated by the Appalachian Mountains in the MODIS total column water vapor (CWV) product derived from near-infrared (NIR) (0.94 micrometers) measurements, which indicate perturbations very close to the surface. The CWV waves are usually observed during spring and late fall or some summer days with low to moderate CWV (below is approx. 2 cm). The observed lee waves display wavelengths from3-4 to 15kmwith an amplitude of variation often comparable to is approx. 50-70% of the total CWV. Since the bulk of atmospheric water vapor is confined to the boundary layer, this indicates that the impact of thesewaves extends deep into the boundary layer, and these may be the lowest level signatures of mountain lee waves presently detected by remote sensing over the land.

Numerical study of wind over breaking waves and generation of spume droplets

NASA Astrophysics Data System (ADS)

Yang, Zixuan; Tang, Shuai; Dong, Yu-Hong; Shen, Lian

2017-11-01

We present direct numerical simulation (DNS) results on wind over breaking waves. The air and water are simulated as a coherent system. The air-water interface is captured using a coupled level-set and volume-of-fluid method. The initial condition for the simulation is fully-developed wind turbulence over strongly-forced steep waves. Because wave breaking is an unsteady process, we use ensemble averaging of a large number of runs to obtain turbulence statistics. The generation and transport of spume droplets during wave breaking is also simulated. The trajectories of sea spray droplets are tracked using a Lagrangian particle tracking method. The generation of droplets is captured using a kinematic criterion based on the relative velocity of fluid particles of water with respect to the wave phase speed. From the simulation, we observe that the wave plunging generates a large vortex in air, which makes an important contribution to the suspension of sea spray droplets.

Generation, propagation and run-up of tsunamis due to the Chicxulub impact event

NASA Astrophysics Data System (ADS)

Weisz, R.; Wuennenmann, K.; Bahlburg, H.

2003-04-01

The Chicxulub impact event can be investigated in (1) local, (2) regional and in (3) global scales. Our investigations focus on the regional scale, especially on the influence of tsunami waves on the coast around the Gulf of Mexico caused by the impact. During an impact two types of tsunamis are generated. The first wave is known as the "rim wave" and is generated in front of the ejecta curtain. The second one is linked to the late modification stage of the impact and results from the collapsing cavity of water. We designate this wave as "collapse wave". The "rim wave" and "collapse wave" are able to propagate over long distances, without a significant loss of wave amplitude. Corresponding to the amplitudes, the waves have a potentially large influence on the coastal areas. Run-up distance and run-up height can be used as parameters for describing this influence. We are utilizing a multimaterial hydrocode (SALE) to simulate the generation of tsunami waves. The propagation of the waves is based on the non-linear shallow water theory, because tsunami waves are defined to be long waves. The position of the coast line varies according to the tsunami run-up and is implemented with open boundary conditions. We show with our investigations (1) the generation of tsunami waves due to shallow water impacts, (2) wave damping during propagation, and (3) the influence of the "rim wave" and the "collapse wave" on the coastal areas. Here, we present our first results from numerical modeling of tsunami waves owing to a Chicxulub sized impactor. The characteristics of the “rim wave” depend on the size of the bolide and the water depth. However, the amplitude and velocity of the “collapse wave” is only determined by the water depth in the impact area. The numerical modeling of the tsunami propagation and run-up is calculated along a section from the impact point towards to the west and gives the moderate damping of both waves and the run-up on the coastal area. As a first approximation, the bathymetric data, used in the wave propagation and run-up, correspond to a linearized bathymetry of the Recent Gulf of Mexico. The linearized bathymetry allows to study the influence of the bathymetry on wave propagation and run-up. Additionally, we give preliminary results of the implementation of the two-dimensional propagation and run-up model for arbitrary bathymetries. The two-dimensional wave propagation model will enable us to more realistically asses the influence of the impact-related tsunamis on the coasts around the Gulf of Mexico due to the Chicxulub impact event.

Solitary wave solutions and their interactions for fully nonlinear water waves with surface tension in the generalized Serre equations

NASA Astrophysics Data System (ADS)

Dutykh, Denys; Hoefer, Mark; Mitsotakis, Dimitrios

2018-04-01

Some effects of surface tension on fully nonlinear, long, surface water waves are studied by numerical means. The differences between various solitary waves and their interactions in subcritical and supercritical surface tension regimes are presented. Analytical expressions for new peaked traveling wave solutions are presented in the dispersionless case of critical surface tension. Numerical experiments are performed using a high-accurate finite element method based on smooth cubic splines and the four-stage, classical, explicit Runge-Kutta method of order 4.

Modeling of Mud-Wave Interaction: Mud-Induced Wave Transport & Wave-Induced Mud Transport

DTIC Science & Technology

2007-11-01

seabed. This can be a fairly rapid process (i.e. of the order of tens of seconds, up to a few minutes at most, e.g. Foda and Zhang (1994); Lindenberg... analysis to shallow water waves and he assumes that the upper layer is non-viscous, and that the waves are sinusoidal and small compared to the water...the pressure and n = the normal vector to the interface, which is correct for ,, << 2,. Extending Gade’s analysis 𔃻 , assuming that superposition

Acoustic-gravity waves, theory and application

NASA Astrophysics Data System (ADS)

Kadri, Usama; Farrell, William E.; Munk, Walter

2015-04-01

Acoustic-gravity waves (AGW) propagate in the ocean under the influence of both the compressibility of sea water and the restoring force of gravity. The gravity dependence vanishes if the wave vector is normal to the ocean surface, but becomes increasingly important as the wave vector acquires a horizontal tilt. They are excited by many sources, including non-linear surface wave interactions, disturbances of the ocean bottom (submarine earthquakes and landslides) and underwater explosions. In this introductory lecture on acoustic-gravity waves, we describe their properties, and their relation to organ pipe modes, to microseisms, and to deep ocean signatures by short surface waves. We discuss the generation of AGW by underwater earthquakes; knowledge of their behaviour with water depth can be applied for the early detection of tsunamis. We also discuss their generation by the non-linear interaction of surface gravity waves, which explains the major role they play in transforming energy from the ocean surface to the crust, as part of the microseisms phenomenon. Finally, they contribute to horizontal water transport at depth, which might affect benthic life.

Excitation of surface waves on one-dimensional solid–fluid phononic crystals and the beam displacement effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moiseyenko, Rayisa P.; Georgia Institute of Technology, UMI Georgia Tech – CNRS, George W. Woodruff School of Mechanical Engineering, Georgia Tech Lorraine, 2 rue Marconi, 57070 Metz-Technopole; Liu, Jingfei

The possibility of surface wave generation by diffraction of pressure waves on deeply corrugated one-dimensional phononic crystal gratings is studied both theoretically and experimentally. Generation of leaky surface waves, indeed, is generally invoked in the explanation of the beam displacement effect that can be observed upon reflection on a shallow grating of an acoustic beam of finite width. True surface waves of the grating, however, have a dispersion that lies below the sound cone in water. They thus cannot satisfy the phase-matching condition for diffraction from plane waves of infinite extent incident from water. Diffraction measurements indicate that deeply corrugatedmore » one-dimensional phononic crystal gratings defined in a silicon wafer are very efficient diffraction gratings. They also confirm that all propagating waves detected in water follow the grating law. Numerical simulations however reveal that in the sub-diffraction regime, acoustic energy of a beam of finite extent can be transferred to elastic waves guided at the surface of the grating. Their leakage to the specular direction along the grating surface explains the apparent beam displacement effect.« less

Developing a framework for integrating turbulence measurements and modeling of ecosystem-atmosphere interactions

NASA Astrophysics Data System (ADS)

Markfort, C. D.

2017-12-01

Aquatic ecosystems are integrators of nutrient and carbon from their watersheds. The effects of climate change in many cases will enhance the rate of these inputs and change the thermodynamics within aquatic environments. It is unclear the extent these changes will have on water quality and carbon assimilation, but the drivers of these processes will be determined by the complex interactions at the land-water and air-water interfaces. For example, flow over and beneath wind-driven surface waves generate turbulence that plays an important role in aquatic ecology and biogeochemistry, exchange of gases such as oxygen and carbon dioxide, and it is important for the transfer of energy and controlling evaporation. Energy transferred from the atmosphere promotes the generation and maintenance of waves. A fraction of the energy is transferred to the surface mixed layer through the generation of turbulence. Energy is also transferred back to the atmosphere by waves. There is a need to quantify the details of the coupled boundary layers of the air-water system to better understand how turbulence plays a role in the interactions. We have developed capabilities to conduct field and laboratory experiments using eddy covariance on tall-towers and rafts, UAS platforms integrated with remote sensing, and detailed wind-wave measurements with time-resolved PIV in a new boundary layer wind-wave tunnel. We will show measurements of the detailed structure of the air and water boundary layers under varying wind and wave conditions in the newly developed IIHR Boundary-Layer Wind-Wave Tunnel. The facility combines a 30-m long recirculating water channel with an open-return boundary layer wind tunnel. A thick turbulent boundary layer is developed in the 1 m high air channel, over the water surface, allowing for the study of boundary layer turbulence interacting with a wind-driven wave field. Results will help interpret remote sensing, energy budget measurements, and turbulence transport models for sheltered lakes influenced by terrain and tall trees.

Comparison of femtosecond laser ablation of aluminum in water and in air by time-resolved optical diagnosis.

PubMed

Hu, Haofeng; Liu, Tiegen; Zhai, Hongchen

2015-01-26

The dynamic process of material ejection and shock wave evolution during one single femtosecond laser pulse ablation of aluminum target in water and air is experimentally investigated by employing pump-probe technique. Shadowgraphs and digital holograms with high temporal resolution are recorded, which intuitively reveal the characteristics of femtosecond laser ablation in the water-confined environment. The experimental result indicates that the liquid significantly restrict the diffusion of the ejected material, and it has a considerable effect on the attenuation of the shock wave. In addition, the expansion Mach wave generated by the ultrasonic expansion of the shock wave is observed.

Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses.

PubMed

Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

2016-06-01

Acoustic signals generated by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum.

Numerical Simulation of Floating Bodies in Extreme Free Surface Waves

NASA Astrophysics Data System (ADS)

Hu, Zheng Zheng; Causon, Derek; Mingham, Clive; Qiang, Ling

2010-05-01

A task of the EPSRC funded research project 'Extreme Wave loading on Offshore Wave Energy Devices: a Hierarchical Team Approach' is to investigate the survivability of two wave energy converter (WEC) devices Pelamis and the Manchester Bobber using different CFD approaches. Both devices float on the water surface, generating the electricity from the motion of the waves. In this paper, we describe developments of the AMAZON-SC 3D numerical wave tank (NWT) to study extreme wave loading of a fixed or floating (in Heave motion) structure. The extreme wave formulation as an inlet condition is due to Dalzell (1999) and Ning et. al. (2009) in which a first or second-order Stokes focused wave can be prescribed. The AMAZON-SC 3D code (see e.g. Hu et al. (2009)) uses a cell centred finite volume method of the Godunov-type for the space discretization of the Euler and Navier Stokes equations. The computational domain includes both air and water regions with the air/water boundary captured as a discontinuity in the density field thereby admitting the break up and recombination of the free surface. Temporal discretisation uses the artificial compressibility method and a dual time stepping strategy to maintain a divergence free velocity field. Cartesian cut cells are used to provide a fully boundary-fitted gridding capability on an regular background Cartesian grid. Solid objects are cut out of the background mesh leaving a set of irregularly shaped cells fitted to the boundary. The advantages of the cut cell approach have been outlined previously by Causon et al. (2000, 2001) including its flexibility for dealing with complex geometries whether stationary or in relative motion. The field grid does not need to be recomputed globally or even locally for moving body cases; all that is necessary is to update the local cut cell data at the body contour for as long as the motion continues. The handing of numerical wave paddles and device motion in a NWT is therefore straightforward and efficient. Firstly, extreme design wave conditions are generated in an empty NWT and compared with physical experiments as a precursor to calculations to investigate the survivability of the Bobber device operating in a challenging wave climate. Secondly, we consider a bench-mark test case involving in a first order regular wave maker acting on a fixed cylinder and Pelamis. Finally, a floating Bobber has been simulated under extreme wave conditions. These results will be reported at the meeting. Causon D.M., Ingram D.M., Mingham C.G., Yang G. Pearson R.V. (2000). Calculation of shallow water flows using a Cartesian cut cell approach. Advances in Water resources, 23: 545-562. Causon D.M., Ingram D.M., Mingham C.G. (2000). A Cartesian cut cell method for shallow water flows with moving boundaries. Advances in Water resources, 24: 899-911. Dalzell J.F. 1999 A note on finite depth second-order wave-wave interactions. Appl. Ocean Res. 21, 105-111. Ning D.Z., Zang J., Liu S.X. Eatock Taylor R. Teng B. & Taylor P.H. 2009 Free surface and wave kinematics for nonlinear focused wave groups. J. Ocean Engineering. Accepted. Hu Z.Z., Causon D.M., Mingham C.M. and Qian L.(2009). Numerical wave tank study of a wave energy converter in heave. Proceedlings 19th ISOPE conference, Osaka, Japan Qian L., Causon D.M. & Mingham C.G., Ingram D.M. 2006 A free-surface capturing method for two fluid flows with moving bodies. Proc. Roy. Soc. London, Vol. A 462 21-42.

Design of a New Water Load for S-band 750 kW Continuous Wave High Power Klystron Used in EAST Tokamak

NASA Astrophysics Data System (ADS)

Liu, Liang; Liu, Fukun; Shan, Jiafang; Kuang, Guangli

2007-04-01

In order to test the klystrons operated at a frequency of 3.7 GHz in a continuous wave (CW) mode, a type of water load to absorb its power up to 750 kW is presented. The distilled water sealed with an RF ceramic window is used as the absorbent. At a frequency range of 70 MHz, the VSWR (Voltage Standing Wave Ratio) is below 1.2, and the rise in temperature of water is about 30 oC at the highest power level.

Observation of sand waves in the Taiwan Banks using HJ-1A/1B sun glitter imagery

NASA Astrophysics Data System (ADS)

Zhang, Hua-guo; Lou, Xiu-lin; Shi, Ai-qin; He, Xie-kai; Guan, Wei-bing; Li, Dong-ling

2014-01-01

This study focuses on the large sand waves in the Taiwan Banks. Our goals are to observe the sand waves as completely as possible, to obtain their direction, wavelength, density, and ridge length, to analyze their spatial distributions, and to understand the effects of the current field and water depth on the sand waves. This study demonstrates the possibility of using HJ-1A/1B sun glitter imagery with a large swath width and rapid coverage in studying sand waves. Six cloud-free HJ-1A/1B optical images with sun glitter signals received during 2009 to 2011 were processed. The sand waves were mapped based on their features in the images; their direction, wavelength, density, and ridge length were measured and analyzed. We identified 4604 sand waves distributed in an area of 16,400 km2. The distributions of sand waves and their characteristics were analyzed, and the differences of sand waves between the northwestern subregion and the southeastern subregion are reported. Further analysis and discussion of the relationships between spatial distribution of the sand waves and both the tidal current field from a numerical simulation and water depth led to some interesting conclusions. The current field determines the orientation of the sand wave, while the hydrodynamic conditions and water depth influence the shape, size, and density of sand waves to a certain degree.

Modeling and Simulation of Hydropower Station Diversion System's characteristic line method by introducing water head to flow feedback

NASA Astrophysics Data System (ADS)

Guangwen, Xu; Xi, Li; Ze, Yao

2018-06-01

To solve the damping problem of water hammer wave in the modeling method of water diversion system of hydropower station, this paper introduces the feedback regulation technology from head to flow, that is: A fixed water head is taken out for flow feedback, and the following conclusions are obtained through modeling and simulation. Adjusting the feedback coefficient F of the water head to the flow rate can change the damping characteristic of the system, which can simulate the attenuation process of the water shock wave in the true water diversion pipeline. Even if a small feedback coefficient is introduced, the damping effect of the system is very obvious, but it has little effect on the amplitude of the first water shock wave after the transition process. Therefore, it is feasible and reasonable to introduce water head to flow rate feedback coefficient F in hydraulic turbine diversion system.

Numerical and experimental results on the spectral wave transfer in finite depth

NASA Astrophysics Data System (ADS)

Benassai, Guido

2016-04-01

Determination of the form of the one-dimensional surface gravity wave spectrum in water of finite depth is important for many scientific and engineering applications. Spectral parameters of deep water and intermediate depth waves serve as input data for the design of all coastal structures and for the description of many coastal processes. Moreover, the wave spectra are given as an input for the response and seakeeping calculations of high speed vessels in extreme sea conditions and for reliable calculations of the amount of energy to be extracted by wave energy converters (WEC). Available data on finite depth spectral form is generally extrapolated from parametric forms applicable in deep water (e.g., JONSWAP) [Hasselmann et al., 1973; Mitsuyasu et al., 1980; Kahma, 1981; Donelan et al., 1992; Zakharov, 2005). The present paper gives a contribution in this field through the validation of the offshore energy spectra transfer from given spectral forms through the measurement of inshore wave heights and spectra. The wave spectra on deep water were recorded offshore Ponza by the Wave Measurement Network (Piscopia et al.,2002). The field regressions between the spectral parameters, fp and the nondimensional energy with the fetch length were evaluated for fetch-limited sea conditions. These regressions gave the values of the spectral parameters for the site of interest. The offshore wave spectra were transfered from the measurement station offshore Ponza to a site located offshore the Gulf of Salerno. The offshore local wave spectra so obtained were transfered on the coastline with the TMA model (Bouws et al., 1985). Finally the numerical results, in terms of significant wave heights, were compared with the wave data recorded by a meteo-oceanographic station owned by Naples Hydrographic Office on the coastline of Salerno in 9m depth. Some considerations about the wave energy to be potentially extracted by Wave Energy Converters were done and the results were discussed.

Monitoring leaf water content with THz and sub-THz waves.

PubMed

Gente, Ralf; Koch, Martin

2015-01-01

Terahertz technology is still an evolving research field that attracts scientists with very different backgrounds working on a wide range of subjects. In the past two decades, it has been demonstrated that terahertz technology can provide a non-invasive tool for measuring and monitoring the water content of leaves and plants. In this paper we intend to review the different possibilities to perform in-vivo water status measurements on plants with the help of THz and sub-THz waves. The common basis of the different methods is the strong absorption of THz and sub-THz waves by liquid water. In contrast to simpler, yet destructive, methods THz and sub-THz waves allow for the continuous monitoring of plant water status over several days on the same sample. The technologies, which we take into focus, are THz time domain spectroscopy, THz continuous wave setups, THz quasi time domain spectroscopy and sub-THz continuous wave setups. These methods differ with respect to the generation and detection schemes, the covered frequency range, the processing and evaluation of the experimental data, and the mechanical handling of the measurements. Consequently, we explain which method fits best in which situation. Finally, we discuss recent and future technological developments towards more compact and budget-priced measurement systems for use in the field.

Forecasting the impact of storm waves and sea-level rise on Midway Atoll and Laysan Island within the Papahānaumokuākea Marine National Monument—a comparison of passive versus dynamic inundation models

USGS Publications Warehouse

Storlazzi, Curt D.; Berkowitz, Paul; Reynolds, Michelle H.; Logan, Joshua B.

2013-01-01

Two inundation events in 2011 underscored the potential for elevated water levels to damage infrastructure and affect terrestrial ecosystems on the low-lying Northwestern Hawaiian Islands in the Papahānaumokuākea Marine National Monument. The goal of this study was to compare passive "bathtub" inundation models based on geographic information systems (GIS) to those that include dynamic water levels caused by wave-induced set-up and run-up for two end-member island morphologies: Midway, a classic atoll with islands on the shallow (2-8 m) atoll rim and a deep, central lagoon; and Laysan, which is characterized by a deep (20-30 m) atoll rim and an island at the center of the atoll. Vulnerability to elevated water levels was assessed using hindcast wind and wave data to drive coupled physics-based numerical wave, current, and water-level models for the atolls. The resulting model data were then used to compute run-up elevations using a parametric run-up equation under both present conditions and future sea-level-rise scenarios. In both geomorphologies, wave heights and wavelengths adjacent to the island shorelines increased more than three times and four times, respectively, with increasing values of sea-level rise, as more deep-water wave energy could propagate over the atoll rim and larger wind-driven waves could develop on the atoll. Although these increases in water depth resulted in decreased set-up along the islands’ shorelines, the larger wave heights and longer wavelengths due to sea-level rise increased the resulting wave-induced run-up. Run-up values were spatially heterogeneous and dependent on the direction of incident wave direction, bathymetry, and island configuration. Island inundation was modeled to increase substantially when wave-driven effects were included, suggesting that inundation and impacts to infrastructure and terrestrial habitats will occur at lower values of predicted sea-level rise, and thus sooner in the 21st century, than suggested by passive GIS-based "bathtub" inundation models. Lastly, observations and the modeling results suggest that classic atolls with islands on a shallow atoll rim are more susceptible to the combined effects of sea-level rise and wave-driven inundation than atolls characterized by a deep atoll rim.

On Hokusai's Great wave off Kanagawa: localization, linearity and a rogue wave in sub-Antarctic waters.

PubMed

Dudley, J M; Sarano, V; Dias, F

2013-06-20

The Hokusai woodcut entitled The great wave off Kanagawa has been interpreted as an unusually large storm wave, likely to be classed as a rogue wave, and possibly generated from nonlinear wave dynamics (J. H. E. Cartwright and H. Nakamura, Notes Rec. R. Soc. 63 , 119-135 (2009)). In this paper, we present a complementary discussion of this hypothesis, discussing in particular how linear and nonlinear mechanisms can both contribute to the emergence of rogue wave events. By making reference to the Great wave 's simultaneous transverse and longitudinal localization, we show that the purely linear mechanism of directional focusing also predicts characteristics consistent with those of the Great wave . In addition, we discuss the properties of a particular rogue wave photographed on the open ocean in sub-Antarctic waters, which shows two-dimensional localization and breaking dynamics remarkably similar to Hokusai's depiction in the woodcut.

On Hokusai's Great wave off Kanagawa: localization, linearity and a rogue wave in sub-Antarctic waters

PubMed Central

Dudley, J. M.; Sarano, V.; Dias, F.

2013-01-01

The Hokusai woodcut entitled The great wave off Kanagawa has been interpreted as an unusually large storm wave, likely to be classed as a rogue wave, and possibly generated from nonlinear wave dynamics (J. H. E. Cartwright and H. Nakamura, Notes Rec. R. Soc. 63, 119–135 (2009)). In this paper, we present a complementary discussion of this hypothesis, discussing in particular how linear and nonlinear mechanisms can both contribute to the emergence of rogue wave events. By making reference to the Great wave's simultaneous transverse and longitudinal localization, we show that the purely linear mechanism of directional focusing also predicts characteristics consistent with those of the Great wave. In addition, we discuss the properties of a particular rogue wave photographed on the open ocean in sub-Antarctic waters, which shows two-dimensional localization and breaking dynamics remarkably similar to Hokusai's depiction in the woodcut. PMID:24687148

Transversally periodic solitary gravity–capillary waves

PubMed Central

Milewski, Paul A.; Wang, Zhan

2014-01-01

When both gravity and surface tension effects are present, surface solitary water waves are known to exist in both two- and three-dimensional infinitely deep fluids. We describe here solutions bridging these two cases: travelling waves which are localized in the propagation direction and periodic in the transverse direction. These transversally periodic gravity–capillary solitary waves are found to be of either elevation or depression type, tend to plane waves below a critical transverse period and tend to solitary lumps as the transverse period tends to infinity. The waves are found numerically in a Hamiltonian system for water waves simplified by a cubic truncation of the Dirichlet-to-Neumann operator. This approximation has been proved to be very accurate for both two- and three-dimensional computations of fully localized gravity–capillary solitary waves. The stability properties of these waves are then investigated via the time evolution of perturbed wave profiles. PMID:24399922

A study of electric field components in shallow water and water half-space models in seabed logging

NASA Astrophysics Data System (ADS)

Rostami, Amir; Soleimani, Hassan; Yahya, Noorhana; Nyamasvisva, Tadiwa Elisha; Rauf, Muhammad

2016-11-01

Seabed logging (SBL) is an electromagnetic (EM) method to detect hydrocarbon (HC) laid beneath the seafloor, which is a development of marine controlled source electromagnetic (CSEM) method. CSEM is a method to show resistivity log of geological layers, transmitting ultra-low frequency EM wave. In SBL a net of receivers, placed on the seafloor, detect reflected and refracted EM wave by layers with different resistivity. Contrast of electrical resistivity of layers impacts on amplitude and phase of the EM wave response. The most indispensable concern in SBL is to detect guided wave via high resistive layer under the seafloor that can be an HC reservoir. Guided wave by HC creates a remarkable difference in received signal when HC reservoir does not exist. While the major contribution of received EM wave in large offset, especially in shallow water environment, is airwave, which is refracted by sea surface due to extremely high resistivity of atmosphere, airwave can affect received guided wave, dramatically. Our objective for this work is to compare HC delineation of tangential and normal components of electric field in shallow water area, using finite element method simulation. Will be reported that, in shallow water environment, minor contribution of air wave in normal component of E field (Ey) versus its major contribution in the tangential component (Ex), causes a considerable contrast on HC delineation of Ey for deeply buried reservoirs (more than 3000 m), while Ex is unable to show different contrasts of received data for with and without HC media at the same condition.

High frequency poroelastic waves in hydrogels.

PubMed

Chiarelli, Piero; Lanatà, Antonio; Carbone, Marina; Domenici, Claudio

2010-03-01

In this work a continuum model for high frequency poroelastic longitudinal waves in hydrogels is presented. A viscoelastic force describing the interaction between the polymer network and the bounded water present in such materials is introduced. The model is tested by means of ultrasound wave speed and attenuation measurements in polyvinylalcohol hydrogel samples. The theory and experiments show that ultrasound attenuation decreases linearly with the increase in the water volume fraction beta of the hydrogel. The introduction of the viscoelastic force between the bounded water and the polymer network leads to a bi-phasic theory, showing an ultrasonic fast wave attenuation that can vary as a function of the frequency with a non-integer exponent in agreement with the experimental data in literature. When beta tends to 1 (100% of interstitial water) due to the presence of bounded water in the hydrogel, the ultrasound phase velocity acquires higher value than that of pure water. The ultrasound speed gap at beta=1 is confirmed by the experimental results, showing that it increases in less cross-linked gel samples which own a higher concentration of bounded water.

Emerging Trends in the Sea State of the Beaufort and Chukchi Seas

DTIC Science & Technology

2016-07-06

Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in...the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing...In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally

Analytical approximation and numerical simulations for periodic travelling water waves

NASA Astrophysics Data System (ADS)

Kalimeris, Konstantinos

2017-12-01

We present recent analytical and numerical results for two-dimensional periodic travelling water waves with constant vorticity. The analytical approach is based on novel asymptotic expansions. We obtain numerical results in two different ways: the first is based on the solution of a constrained optimization problem, and the second is realized as a numerical continuation algorithm. Both methods are applied on some examples of non-constant vorticity. This article is part of the theme issue 'Nonlinear water waves'.

The family of anisotropically scaled equatorial waves

NASA Astrophysics Data System (ADS)

RamíRez GutiéRrez, Enver; da Silva Dias, Pedro Leite; Raupp, Carlos; Bonatti, Jose Paulo

2011-04-01

In the present work we introduce the family of anisotropic equatorial waves. This family corresponds to equatorial waves at intermediate states between the shallow water and the long wave approximation model. The new family is obtained by using anisotropic time/space scalings on the linearized, unforced and inviscid shallow water model. It is shown that the anisotropic equatorial waves tend to the solutions of the long wave model in one extreme and to the shallow water model solutions in the other extreme of the parameter dependency. Thus, the problem associated with the completeness of the long wave model solutions can be asymptotically addressed. The anisotropic dispersion relation is computed and, in addition to the typical dependency on the equivalent depth, meridional quantum number and zonal wavenumber, it also depends on the anisotropy between both zonal to meridional space and velocity scales as well as the fast to slow time scales ratio. For magnitudes of the scales compatible with those of the tropical region, both mixed Rossby-gravity and inertio-gravity waves are shifted to a moderately higher frequency and, consequently, not filtered out. This draws attention to the fact that, for completeness of the long wave like solutions, it is necessary to include both the anisotropic mixed Rossby-gravity and inertio-gravity waves. Furthermore, the connection of slow and fast manifolds (distinguishing feature of equatorial dynamics) is preserved, though modified for the equatorial anisotropy parameters used δ ∈ < 1]. New possibilities of horizontal and vertical scale nonlinear interactions are allowed. Thus, the anisotropic shallow water model is of fundamental importance for understanding multiscale atmosphere and ocean dynamics in the tropics.

SH-wave refraction/reflection and site characterization

USGS Publications Warehouse

Wang, Z.; Street, R.L.; Woolery, E.W.; Madin, I.P.

2000-01-01

Traditionally, nonintrusive techniques used to characterize soils have been based on P-wave refraction/reflection methods. However, near-surface unconsolidated soils are oftentimes water-saturated, and when groundwater is present at a site, the velocity of the P-waves is more related to the compressibility of the pore water than to the matrix of the unconsolidated soils. Conversely, SH-waves are directly relatable to the soil matrix. This makes SH-wave refraction/reflection methods effective in site characterizations where groundwater is present. SH-wave methods have been used extensively in site characterization and subsurface imaging for earthquake hazard assessments in the central United States and western Oregon. Comparison of SH-wave investigations with geotechnical investigations shows that SH-wave refraction/reflection techniques are viable and cost-effective for engineering site characterization.

Lump waves and breather waves for a (3+1)-dimensional generalized Kadomtsev-Petviashvili Benjamin-Bona-Mahony equation for an offshore structure

NASA Astrophysics Data System (ADS)

Yin, Ying; Tian, Bo; Wu, Xiao-Yu; Yin, Hui-Min; Zhang, Chen-Rong

2018-04-01

In this paper, we investigate a (3+1)-dimensional generalized Kadomtsev-Petviashvili Benjamin-Bona-Mahony equation, which describes the fluid flow in the case of an offshore structure. By virtue of the Hirota method and symbolic computation, bilinear forms, the lump-wave and breather-wave solutions are derived. Propagation characteristics and interaction of lump waves and breather waves are graphically discussed. Amplitudes and locations of the lump waves, amplitudes and periods of the breather waves all vary with the wavelengths in the three spatial directions, ratio of the wave amplitude to the depth of water, or product of the depth of water and the relative wavelength along the main direction of propagation. Of the interactions between the lump waves and solitons, there exist two different cases: (i) the energy is transferred from the lump wave to the soliton; (ii) the energy is transferred from the soliton to the lump wave.

A (2+1)-dimensional Korteweg-de Vries type equation in water waves: Lie symmetry analysis; multiple exp-function method; conservation laws

NASA Astrophysics Data System (ADS)

Adem, Abdullahi Rashid

2016-05-01

We consider a (2+1)-dimensional Korteweg-de Vries type equation which models the shallow-water waves, surface and internal waves. In the analysis, we use the Lie symmetry method and the multiple exp-function method. Furthermore, conservation laws are computed using the multiplier method.

Reflected GPS Power for the Detection of Surface Roughness Patterns in Coastal Water

NASA Technical Reports Server (NTRS)

Oertel, George, F.; Allen, Thomas R.

2000-01-01

Coastal bays formed by the barrier islands of Delaware, Maryland and Virginia are parts of a coastal region known as a "Coastal Compartment". The coastal compartment between the Chesapeake and Delaware Bays is actually the mosaic of landscapes on the headland of the interfluve that separates these large drainage basins. The coastal compartments form a variety of different-shaped waterways landward of the coastline. Shape differences along the boundaries produce differences in exposure to wind and waves. Different shoreface topographies seaward of the coastline also influence surface roughness by changing wave-refraction patterns. Surface-water roughness (caused by waves) is controlled by a number of parameters, including fetch, shielding, exposure corridors, water-mass boundary conditions, wetland vegetation and water depth in coastal bays. In the coastal ocean, surface roughness patterns are controlled by shoreface shoaling and inlet refraction patterns in the coastal ocean. Knowledge of wave phenomena in the nearshore and backbarrier areas is needed to understand how wave climate influences important ecosystems in estuaries and bays.

The polarization patterns of skylight reflected off wave water surface.

PubMed

Zhou, Guanhua; Xu, Wujian; Niu, Chunyue; Zhao, Huijie

2013-12-30

In this paper we propose a model to understand the polarization patterns of skylight when reflected off the surface of waves. The semi-empirical Rayleigh model is used to analyze the polarization of scattered skylight; the Harrison and Coombes model is used to analyze light radiance distribution; and the Cox-Munk model and Mueller matrix are used to analyze reflections from wave surface. First, we calculate the polarization patterns and intensity distribution of light reflected off wave surface. Then we investigate their relationship with incident radiation, solar zenith angle, wind speed and wind direction. Our results show that the polarization patterns of reflected skylight from waves and flat water are different, while skylight reflected on both kinds of water is generally highly polarized at the Brewster angle and the polarization direction is approximately parallel to the water's surface. The backward-reflecting Brewster zone has a relatively low reflectance and a high DOP in all observing directions. This can be used to optimally diminish the reflected skylight and avoid sunglint in ocean optics measurements.

Influence of natural surfactants on short wind waves in the coastal Peruvian waters

NASA Astrophysics Data System (ADS)

Kiefhaber, D.; Zappa, C. J.; Jähne, B.

2015-07-01

Results from measurements of wave slope statistics during the R/V Meteor M91 cruise in the coastal upwelling regions off the coast of Peru are reported. Wave slope probability distributions were measured with an instrument based on the reflection of light at the water surface and a method very similar to the Cox and Munk (1954b) sun glitter technique. During the cruise, the mean square slope (mss) of the waves was found to be very variable, despite the limited range of encountered wind speeds. The Cox and Munk (1954b) parameterization for clean water is found to overestimate mss, but most measurements fall in the range spanned by their clean water and slick parameterizations. The observed variability of mss is attributed to the wave damping effect of surface films, generated by increased biological production in the upwelling zones. The small footprint and high temporal resolution of the measurement allows for tracking abrupt changes in conditions caused by the often patchy structure of the surface films.

Modifiying shallow-water equations as a model for wave-vortex turbulence

NASA Astrophysics Data System (ADS)

Mohanan, A. V.; Augier, P.; Lindborg, E.

2017-12-01

The one-layer shallow-water equations is a simple two-dimensional model to study the complex dynamics of the oceans and the atmosphere. We carry out forced-dissipative numerical simulations, either by forcing medium-scale wave modes, or by injecting available potential energy (APE). With pure wave forcing in non-rotating cases, a statistically stationary regime is obtained for a range of forcing Froude numbers Ff = ɛ /(kf c), where ɛ is the energy dissipation rate, kf the forcing wavenumber and c the wave speed. Interestingly, the spectra scale as k-2 and third and higher order structure functions scale as r. Such statistics is a manifestation of shock turbulence or Burgulence, which dominate the flow. Rotating cases exhibit some inverse energy cascade, along with a stronger forward energy cascade, dominated by wave-wave interactions. We also propose two modifications to the classical shallow-water equations to construct a toy model. The properties of the model are explored by forcing in APE at a small and a medium wavenumber. The toy model simulations are then compared with results from shallow-water equations and a full General Circulation Model (GCM) simulation. The most distinctive feature of this model is that, unlike shallow-water equations, it avoids shocks and conserves quadratic energy. In Fig. 1, for the shallow-water equations, shocks appear as thin dark lines in the divergence (∇ .{u}) field, and as discontinuities in potential temperature (θ ) field; whereas only waves appear in the corresponding fields from toy model simulation. Forward energy cascade results in a wave field with k-5/3 spectrum, along with equipartition of KE and APE at small scales. The vortical field develops into a k-3 spectrum. With medium forcing wavenumber, at large scales, energy converted from APE to KE undergoes inverse cascade as a result of nonlinear fluxes composed of vortical modes alone. Gradually, coherent vortices emerge with a strong preference for anticyclonic motion. The model can serve as a closer representation of real geophysical turbulence than the classical shallow-water equations. Fig 1. Divergence and potential temperature fields of shallow-water (top row) and toy model (bottom row) simulations.

Strait of Gibraltar as seen from STS-60

NASA Image and Video Library

1994-02-09

STS060-88-070 (3-11 Feb 1994) --- This view shows sunglint in the Strait of Gibralter. In this photograph a high pressure atmospheric system over the Iberian Peninsula has set the conditions for seeing a plankton bloom along the Moroccan coast in the Alboran Sea (Western Mediterranean) coastal counter current as well as illumining the influence of winds in the sunglint pattern near the Strait of Gibraltar. Where the water is ruffled from a wind gust, such as off Cadiz, Spain, the surface is less reflective and thus appears dark. A combination of the effects of the tide and the surface winds through the Strait of Gibraltar have created a unique sunglint pattern at the entrance of the Mediterranean. The Atlantic Ocean waters are flowing with the tide through the Strait of Gibraltar into the Mediterranean Sea and are probably smoothing out some of the smaller waves at the surface. The incoming tide generates internal waves as can be faintly seen in this photograph. The incoming relatively cooler, less dense Atlantic water flows over the warm, more saline Mediterranean water. As the tide moves into the Strait of Gibraltar it encounters the Camarinal Sill, which is like a cliff under the water, south of Camarinal Point, Spain. Internal waves are generated at this sill and they travel along the density boundary between the Atlantic water and the Mediterranean water masses. There is little evidence of the internal waves at the surface of the ocean. We can see them in spacecraft photography because of the sunglint which reflects off the different water layers in differential patterns. The internal waves also smooth out some of the bands of capillary waves at the surface. That is, the sun reflects more brightly from these smooth areas, showing the pattern of the underwater waves more prominently than do the surface waves. The Bay of Cadiz on the southwest coast of Spain, the Rock of Gibraltar, and the Moroccan coast are also beautifully illustrated in this photography. The focus for scientists, however, remains the high clarity and spatial resolution given by sunglint studies to physical phenomena in the ocean.

Experimentally Modeling Black and White Hole Event Horizons via Fluid Flow

NASA Astrophysics Data System (ADS)

Manheim, Marc E.; Lindner, John F.; Manz, Niklas

We will present a scaled down experiment that hydrodynamically models the interaction between electromagnetic waves and black/white holes. It has been mathematically proven that gravity waves in water can behave analogously to electromagnetic waves traveling through spacetime. In this experiment, gravity waves will be generated in a water tank and propagate in a direction opposed to a flow of varying rate. We observe a noticeable change in the wave's spreading behavior as it travels through the simulated horizon with decreased wave speeds up to standing waves, depending on the opposite flow rate. Such an experiment has already been performed in a 97.2 cubic meter tank. We reduced the size significantly to be able to perform the experiment under normal lab conditions.

Wave-induced mass transport affects daily Escherichia coli fluctuations in nearshore water.

PubMed

Ge, Zhongfu; Whitman, Richard L; Nevers, Meredith B; Phanikumar, Mantha S

2012-02-21

Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s(-1)). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731-6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.

Wave-induced mass transport affects daily Escherichia coli fluctuations in nearshore water

USGS Publications Warehouse

Ge, Zhongfu; Whitman, Richard L.; Nevers, Meredith B.; Phanikumar, Mantha S.

2012-01-01

Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s–1). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731–6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.

Fate of internal waves on a shallow shelf

NASA Astrophysics Data System (ADS)

Davis, Kristen; Arthur, Robert; Reid, Emma; Decarlo, Thomas; Cohen, Anne

2017-11-01

Internal waves strongly influence the physical and chemical environment of coastal ecosystems worldwide. We report novel observations from a distributed temperature sensing (DTS) system that tracked the transformation of internal waves from the shelf break to the surf zone over a shelf-slope region of a coral atoll in the South China Sea. The spatially-continuous view of the near-bottom temperature field provided by the DTS offers a perspective of physical processes previously available only in laboratory settings or numerical models. These processes include internal wave reflection off a natural slope, shoreward transport of dense fluid within trapped cores, internal ``tide pools'' (dense water left behind after the retreat of an internal wave), and internal run-down (near-bottom, offshore-directed jets of water preceding a breaking internal wave). Analysis shows that the fate of internal waves on this shelf - whether they are transmitted into shallow waters or reflected back offshore - is mediated by local water column density and shear structure, with important implications for nearshore distributions of energy, heat, and nutrients. We acknowledge the US Army Research Laboratory DoD Supercomputing Resource Center for computer time on Excalibur, which was used for the numerical simulations in this work. Funding for field work supported by Academia Sinica and for K.D. and E.R. from NSF.

Water Power News | Water Power | NREL

Science.gov Websites

the National Renewable Energy Laboratory. February 8, 2018 New Wave Energy Converter Design Inspired new wave energy converter design. January 3, 2018 Student-Designed Flume Arrives at NWTC An NREL collaboration with the Colorado School of Mines stimulated an innovative water flume design. Archives 2018

Predicting location-specific extreme coastal floods in the future climate by introducing a probabilistic method to calculate maximum elevation of the continuous water mass caused by a combination of water level variations and wind waves

NASA Astrophysics Data System (ADS)

Leijala, Ulpu; Björkqvist, Jan-Victor; Johansson, Milla M.; Pellikka, Havu

2017-04-01

Future coastal management continuously strives for more location-exact and precise methods to investigate possible extreme sea level events and to face flooding hazards in the most appropriate way. Evaluating future flooding risks by understanding the behaviour of the joint effect of sea level variations and wind waves is one of the means to make more comprehensive flooding hazard analysis, and may at first seem like a straightforward task to solve. Nevertheless, challenges and limitations such as availability of time series of the sea level and wave height components, the quality of data, significant locational variability of coastal wave height, as well as assumptions to be made depending on the study location, make the task more complicated. In this study, we present a statistical method for combining location-specific probability distributions of water level variations (including local sea level observations and global mean sea level rise) and wave run-up (based on wave buoy measurements). The goal of our method is to obtain a more accurate way to account for the waves when making flooding hazard analysis on the coast compared to the approach of adding a separate fixed wave action height on top of sea level -based flood risk estimates. As a result of our new method, we gain maximum elevation heights with different return periods of the continuous water mass caused by a combination of both phenomena, "the green water". We also introduce a sensitivity analysis to evaluate the properties and functioning of our method. The sensitivity test is based on using theoretical wave distributions representing different alternatives of wave behaviour in relation to sea level variations. As these wave distributions are merged with the sea level distribution, we get information on how the different wave height conditions and shape of the wave height distribution influence the joint results. Our method presented here can be used as an advanced tool to minimize over- and underestimation of the combined effect of sea level variations and wind waves, and to help coastal infrastructure planning and support smooth and safe operation of coastal cities in a changing climate.

Bedforms induced by solitary waves: laboratory studies on generation and migration rate

NASA Astrophysics Data System (ADS)

la Forgia, Giovanni; Adduce, Claudia; Falcini, Federico; Paola, Chris

2017-04-01

This study presents experiments on the formation of sandy bedforms, produced by surface solitary waves (SSWs) in shallow water conditions. The experiments were carried out in a 12.0 m long, 0.15 m wide and 0.5 m high flume, at Saint Anthony Falls Laboratory in Minneapolis. The tank is filled by fresh water and a removable gate, placed at the left hand-side of the tank, divides the flume in two regions: the lock region and the ambient fluid region. The standard lock-release method generates SSWs by producing a displacement between the free surfaces that are divided by the gate. Wave amplitude, wavelength, and celerity depend on the lock length and on the water level difference between the two regions. Natural sand particles (D50=0.64) are arranged on the bottom in order to form a horizontal flat layer with a thickness of 2 cm. A digital pressure gauge and a high-resolution acoustic velocimeter allowed us to measure, locally, both pressure and 3D water velocity induced on the bottom by each wave. Image analysis technique is then used to obtain the main wave features: amplitude, wavelength, and celerity. Dye is finally used as vertical tracer to mark the horizontal speed induced by the wave. For each experiment we generated 400 waves, having the same features and we analyzed their action on sand particles placed on the bottom. The stroke, induced by each wave, entails a shear stress on the sand particles, causing sediment transport in the direction of wave propagation. Immediately after the wave passage, a back flow occurs near the bottom. The horizontal pressure gradient and the velocity field induced by the wave cause the boundary layer separation and the consequent reverse flow. Depending on the wave features and on the water depth, the boundary shear stress induced by the reverse flow can exceed the critical value inducing the back motion of the sand particles. The experiments show that the particle back motion is localized at particular cross sections along the tank, where the wave steepening occur. For this reason, the pressure and velocity measures were collected in several cross sections along the tank. The propagation of consecutive waves with the same features induces the generation of erosion and accumulation zones, which slowly evolve in isometric bedforms.

On the use of wave parameterizations and a storm impact scaling model in National Weather Service Coastal Flood and decision support operations

USGS Publications Warehouse

Mignone, Anthony; Stockdon, H.; Willis, M.; Cannon, J.W.; Thompson, R.

2012-01-01

National Weather Service (NWS) Weather Forecast Offices (WFO) are responsible for issuing coastal flood watches, warnings, advisories, and local statements to alert decision makers and the general public when rising water levels may lead to coastal impacts such as inundation, erosion, and wave battery. Both extratropical and tropical cyclones can generate the prerequisite rise in water level to set the stage for a coastal impact event. Forecasters use a variety of tools including computer model guidance and local studies to help predict the potential severity of coastal flooding. However, a key missing component has been the incorporation of the effects of waves in the prediction of total water level and the associated coastal impacts. Several recent studies have demonstrated the importance of incorporating wave action into the NWS coastal flood program. To follow up on these studies, this paper looks at the potential of applying recently developed empirical parameterizations of wave setup, swash, and runup to the NWS forecast process. Additionally, the wave parameterizations are incorporated into a storm impact scaling model that compares extreme water levels to beach elevation data to determine the mode of coastal change at predetermined “hotspots” of interest. Specifically, the storm impact model compares the approximate storm-induced still water level, which includes contributions from tides, storm surge, and wave setup, to dune crest elevation to determine inundation potential. The model also compares the combined effects of tides, storm surge, and the 2 % exceedance level for vertical wave runup (including both wave setup and swash) to dune toe and crest elevations to determine if erosion and/or ocean overwash may occur. The wave parameterizations and storm impact model are applied to two cases in 2009 that led to significant coastal impacts and unique forecast challenges in North Carolina: the extratropical “Nor'Ida” event during 11-14 November and the large swell event from distant Hurricane Bill on 22 August. The coastal impacts associated with Nor'Ida were due to the combined effects of surge, tide, and wave processes and led to an estimated 5.8 million dollars in damage. While the impacts from Hurricane Bill were not as severe as Nor'Ida, they were mainly associated with wave processes. Thus, this event exemplifies the importance of incorporating waves into the total water level and coastal impact prediction process. These examples set the stage for potential future applications including adaption to the more complex topography along the New England coast.

On periodic geophysical water flows with discontinuous vorticity in the equatorial f-plane approximation

NASA Astrophysics Data System (ADS)

Martin, Calin Iulian

2017-12-01

We are concerned here with geophysical water waves arising as the free surface of water flows governed by the f-plane approximation. Allowing for an arbitrary bounded discontinuous vorticity, we prove the existence of steady periodic two-dimensional waves of small amplitude. We illustrate the local bifurcation result by means of an analysis of the dispersion relation for a two-layered fluid consisting of a layer of constant non-zero vorticity γ1 adjacent to the surface situated above another layer of constant non-zero vorticity γ2≠γ1 adjacent to the bed. For certain vorticities γ1,γ2, we also provide estimates for the wave speed c in terms of the speed at the surface of the bifurcation inducing laminar flows. This article is part of the theme issue 'Nonlinear water waves'.

Nonlinear and linear bottom interaction effects in shallow water

NASA Technical Reports Server (NTRS)

Shemdin, O.; Hsiao, S. V.; Hasselmann, K.; Herterich, K.

1978-01-01

The paper examines wave-energy dissipation rates in shallow water calculated from measured wave spectra at different distances from the shore. Different linear and nonlinear transfer and dissipation mechanisms are discussed. The various data sets are interpreted in terms of prevailing mechanisms at the respective sites. The incorporation of different processes in a predictive shallow-water model is outlined. The analysis suggests that bottom motion is primarily responsible for wave-energy dissipation in the Delta Region of the Gulf of Mexico, that friction is mainly responsible for wave-energy dissipation in Marineland, Panama City and Melkbosstrand, and that percolation is probably the dominant mechanism in the JONSWAP area of the North Sea.

Hydroelectric power from ocean waves

NASA Astrophysics Data System (ADS)

Raghavendran, K.

1981-02-01

This paper describes a system which converts the variable energy of ocean waves into a steady supply of energy in a conventional form. The system consists of a set of floats and Persian wheels located off-shore and a storage reservoir on the shore. The floats oscillate vertically as the waves pass below them and turn their respective Persian wheels which lift sea water to a height and deliver to the reservoir through an interconnecting pipeline. The head of water in the reservoir operates a hydraulic turbine which in turn works a generator to supply electricity. Due to the recurrent wave action, water is maintained at the optimum level in the reservoir to ensure continuous power supply.

Effects of wind-wave disturbances on adsorption and desorption of tetracycline and sulfadimidine in water-sediment systems.

PubMed

Liao, Qianjiahua; Huang, Zheng; Li, Shu; Wang, Yi; Liu, Yuqing; Luo, Ran; Shang, Jingge

2018-05-28

Wind-wave disturbances frequently disperse sediment particles into overlying water, which facilitates the adsorption and desorption of contaminants in aquatic ecosystems. Tetracycline (TC) and sulfadimidine (SM2) are common antibiotics that are frequently found in aquatic environments. This study utilized microcosms, comprising sediment and water from Lake Taihu, China, to examine the adsorption and desorption of TC and SM2 under different wind-wave disturbances in a shallow lake environment. The adsorption experiments were conducted with three different concentrations (1, 5, 10 mg/L) of TC and SM2 in the overlying water, and two different (background and strong) wind-wave conditions for 72 h. Subsequently, four microcosms were employed in a 12-h desorption study. Analysis of adsorption progress showed that TC concentration in the overlying water decreased quickly, while SM2 remained almost constant. In the desorption experiments, SM2 released to the overlying water was an order of magnitude greater than TC. These results indicate that sediment particles strongly adsorb TC but weakly adsorb SM2. Compared to background conditions, the strong wind-wave conditions resulted in higher concentrations of TC and SM2 in sediment and facilitated their migration to deeper sediment during adsorption, correspondingly promoting greater release of TC and SM2 from sediment particles into the overlying water during desorption.

Applied Analytical Methods for Solving Some Problems of Wave Propagation in the Coastal Areas

NASA Astrophysics Data System (ADS)

Gagoshidze, Shalva; Kodua, Manoni

2016-04-01

Analytical methods, easy for application, are proposed for the solution of the following four classical problems of coastline hydro mechanics: 1. Refraction of waves on coast slopes of arbitrary steepness; 2. Wave propagation in tapering water areas; 3. Longitudinal waves in open channels; 4. Long waves on uniform and non-uniform flows of water. The first three of these problems are solved by the direct Galerkin-Kantorovich method with a choice , of basic functions which completely satisfy all boundary conditions. This approach leads to obtaining new evolutionary equations which can be asymptotically solved by the WKB method. The WKB solution of the first problem enables us to easily determine the three-dimensional field of velocities and to construct the refraction picture of the wave surface near the coast having an arbitrary angle of slope to the horizon varying from 0° to 180°. This solution, in particular for a vertical cliff, fully agrees with Stoker's particular but difficult solution. Moreover, it is shown for the first time that our Schrödinger type evolutionary equation leads to the formation of the so-called "potential wells" if the angle of coast slope to the horizon exceeds 45°, while the angle given at infinity (i.e. at a large distance from the shore) between the wave crests and the coastline exceeds 75°. This theoretical result expressed in terms of elementary functions is well consistent with the experimental observations and with lot of aerial photographs of waves in the coastal zones of the oceans [1,2]. For the second problem we introduce the notions of "wide" and "narrow" water areas. It is shown that Green's law on the wave height growth holds only for the narrow part of the water area, whereas in the wide part the tapering of the water area leads to an insignificant decrease of the wave height. For the third problem, the bank slopes of trapezoidal channels are assumed to have an arbitrary angle of steepness. So far we have known the practically applicable solutions (obtained by MacDonald and Kelland) only for triangular channels whose lateral slopes to the horizon are 30°and 45°. For the fourth problem, a number of unique results are obtained by the correct linearization of shallow water equations. These results include in particular the following: the wave propagation against the flow is blocked by a stream with a Froude number Fr >2/3, but not with Fr > 1, as thought previously. New relations are derived for the conjugate depths of all types of hydraulic jumps and discontinuous roll-waves. References: 1.Stoker,J.J.1957 Water waves.The mathematical theory with application. New York: Interscience Publ., 567 p., (Figures 5.6.2, 5.6.3 and 5.6.5). 2.Hodgins,D.O., Le Blond, P.H. and Huntley, D.A., 1985, Shallow-water wave calculations. Canadian Contractor Report of Hydrography and Ocean Sciences, 10,75 p.,(Figure 3.5). The work supported by Grant Do/77/3-109/14 of the Georgian National Science Foundation

Effects of obliquely opposing and following currents on wave propagation in a new 3D wave-current basin

NASA Astrophysics Data System (ADS)

Lieske, Mike; Schlurmann, Torsten

2016-04-01

INTRODUCTION & MOTIVATION The design of structures in coastal and offshore areas and their maintenance are key components of coastal protection. Usually, assessments of processes and loads on coastal structures are derived from experiments with flow and wave parameters in separate physical models. However, Peregrin (1976) already points out that processes in natural shallow coastal waters flow and sea state processes do not occur separately, but influence each other nonlinearly. Kemp & Simons (1982) perform 2D laboratory tests and study the interactions between a turbulent flow and following waves. They highlight the significance of wave-induced changes in the current properties, especially in the mean flow profiles, and draw attention to turbulent fluctuations and bottom shear stresses. Kemp & Simons (1983) also study these processes and features with opposing waves. Studies on the wave-current interaction in three-dimensional space for a certain wave height, wave period and water depth were conducted by MacIver et al. (2006). The research focus is set on the investigation of long-crested waves on obliquely opposing and following currents in the new 3D wave-current basin. METHODOLOGY In a first step the flow analysis without waves is carried out and includes measurements of flow profiles in the sweet spot of the basin at predefined measurement positions. Five measuring points in the water column have been delineated in different water depths in order to obtain vertical flow profiles. For the characterization of the undisturbed flow properties in the basin, an uniformly distributed flow was generated in the wave basin. In the second step wave analysis without current, the unidirectional wave propagation and wave height were investigated for long-crested waves in intermediate wave conditions. In the sweet spot of the wave basin waves with three different wave directions, three wave periods and uniform wave steepness were examined. For evaluation, we applied a common 3D wave analysis method, the Bayesian Directional Spectrum method (BDM). BDM was presented by Hashimoto et al. (1988). Lastly, identification of the wave-current interaction, the results from experiment with simultaneous waves and currents are compared with results for only-currents and only-waves in order to identify and exemplify the significance of nonlinear interaction processes. RESULTS The first results of the wave-current interaction show, as expected, a reduction in the wave height in the direction of flow and an increase in wave heights against the flow with unidirectional monochromatic waves. The superposition of current and orbital velocities cannot be conducted linearly. Furthermore, the results show a current domination for low wave periods and wave domination for larger wave periods. The criterion of a current or wave domination will be presented in the presentation. ACKNOWLEDGEMENT The support of the KFKI research project "Seegangsbelastungen (Seele)" (Contract No. 03KIS107) by the German "Federal Ministry of Education and Research (BMBF)" is gratefully acknowledged.

Wave propagation against current : a study of the effects of vertical shears of the mean current on the geometrical focusing of water waves

NASA Astrophysics Data System (ADS)

Charland, Jenna; Touboul, Julien; Rey, Vincent

2013-04-01

Wave propagation against current : a study of the effects of vertical shears of the mean current on the geometrical focusing of water waves J. Charland * **, J. Touboul **, V. Rey ** jenna.charland@univ-tln.fr * Direction Générale de l'Armement, CNRS Délégation Normandie ** Université de Toulon, 83957 La Garde, France Mediterranean Institute of Oceanography (MIO) Aix Marseille Université, 13288 Marseille, France CNRS/INSU, IRD, MIO, UM 110 In the nearshore area, both wave propagation and currents are influenced by the bathymetry. For a better understanding of wave - current interactions in the presence of a 3D bathymetry, a large scale experiment was carried out in the Ocean Basin FIRST, Toulon, France. The 3D bathymetry consisted of two symmetric underwater mounds on both sides in the mean wave direction. The water depth at the top the mounds was hm=1,5m, the slopes of the mounds were of about 1:3, the water depth was h=3 m elsewhere. For opposite current conditions (U of order 0.30m/s), a huge focusing of the wave up to twice its incident amplitude was observed in the central part of the basin for T=1.4s. Since deep water conditions are verified, the wave amplification is ascribed to the current field. The mean velocity fields at a water depth hC=0.25m was measured by the use of an electromagnetic current meter. The results have been published in Rey et al [4]. The elliptic form of the "mild slope" equation including a uniform current on the water column (Chen et al [1]) was then used for the calculations. The calculated wave amplification of factor 1.2 is significantly smaller than observed experimentally (factor 2). So, the purpose of this study is to understand the physical processes which explain this gap. As demonstrated by Kharif & Pelinovsky [2], geometrical focusing of waves is able to modify significantly the local wave amplitude. We consider this process here. Since vertical velocity profiles measured at some locations have shown significant vertical shears, further theoretical expansions have considered this shearing following the hypothesis proposed by Kirby [3]. A numerical solver for this new equation is being developed. Results obtained with this new equation will be compared to a new set of experiments. This comparison will allow us to quantify the role of a sheared current in the geometrical focusing of the wave. References : [1] W. Chen, V. Panchang, and Z. Demirbilek. On the modeling of wave-current interaction using the elliptic mild-slope wave equation. Ocean Engineering, 32 :2135-2164, 2005. [2] C. Kharif and E. Pelinovsky. Physical mechanisms of the rogue wave phenomenon. European Journal of Mechanics B/Fluids, 22 : 603-634, 2003 [3] J. T. Kirby. A note on linear surface wave-current interaction over slowly varying topography. Journal of Geophysical Research, 89(C1) : 745-747, January 20 1984. [4] V. Rey, F. Guinot, and J. Touboul. Large scale experimental study of wave current interactions in presence of a 3d bathymetry. Genoa : s.n., 2011. International Maritime Association of the Mediterranean.

Wave height estimates from pressure and velocity data at an intermediate depth in the presence of uniform currents

NASA Astrophysics Data System (ADS)

Basu, Biswajit

2017-12-01

Bounds on estimates of wave heights (valid for large amplitudes) from pressure and flow measurements at an arbitrary intermediate depth have been provided. Two-dimensional irrotational steady water waves over a flat bed with a finite depth in the presence of underlying uniform currents have been considered in the analysis. Five different upper bounds based on a combination of pressure and velocity field measurements have been derived, though there is only one available lower bound on the wave height in the case of the speed of current greater than or less than the wave speed. This article is part of the theme issue 'Nonlinear water waves'.

In-situ and Land-Based Remote Sensing of River Inlets and Their Interaction with Coastal Waters

DTIC Science & Technology

2013-09-30

CDIP buoy 190 was reporting the impending waves having a 1 meter significant wave height, 7.7s peak period, from 129 degrees. Using the X-Band...spectral energy along a shifted dispersion relationship curve. In deep water, the waves reported by CDIP buoy 190 would have a wavenumber of 0.068 rad/m

Surface Gravity Waves: Resonance in a Fish Tank

ERIC Educational Resources Information Center

Sinick, Scott J.; Lynch, John J.

2010-01-01

In this work, an inexpensive 10-gallon glass aquarium was used to study wave motion in water. The waves travel at speeds comparable to a person walking ([approximately]1 m/s). The scale of the motion allows for distances to be measured with a meterstick and for times to be measured with a stopwatch. For a wide range of water depths, standing waves…

Wave energy and swimming performance shape coral reef fish assemblages

PubMed Central

Fulton, C.J; Bellwood, D.R; Wainwright, P.C

2005-01-01

Physical factors often have an overriding influence on the distribution patterns of organisms, and can ultimately shape the long-term structure of communities. Although distribution patterns in sessile marine organisms have frequently been attributed to functional characteristics interacting with wave-induced water motion, similar evidence for mobile organisms is lacking. Links between fin morphology and swimming performance were examined in three diverse coral reef fish families from two major evolutionary lineages. Among-habitat variation in morphology and performance was directly compared with quantitative values of wave-induced water motion from seven coral reef habitats of different depth and wave exposure on the Great Barrier Reef. Fin morphology was strongly correlated with both field and experimental swimming speeds in all three families. The range of observed swimming speeds coincided closely with the magnitude of water velocities commonly found on coral reefs. Distribution patterns in all three families displayed highly congruent relationships between fin morphology and wave-induced water motion. Our findings indicate a general functional relationship between fin morphology and swimming performance in labriform-swimming fishes, and provide quantitative evidence that wave energy may directly influence the assemblage structure of coral reef fishes through interactions with morphology and swimming performance. PMID:15888415

Sedimentary structures formed under water surface waves: examples from a sediment-laden flash flood observed by remote camer

NASA Astrophysics Data System (ADS)

Froude, Melanie; Alexander, Jan; Cole, Paul; Barclay, Jenni

2014-05-01

On 13-14 October 2012, Tropical Storm Rafael triggered sediment-laden flash floods in the Belham Valley on Montserrat, West Indies. Rainfall was continuous for ~38 hours and intensity peaked at 48 mm/hr. Flow was strongly unsteady, turbulent with sediment concentrations varying up to hyperconcentrated. Time-lapse images captured at >1 frame per second by remote camera overlooking a surveyed valley section show the development of trains of water surface waves at multiple channel locations during different flow stages. Waves grew and diminished in height and remained stationary or migrated upstream. Trains of waves persisted for <5 minutes, until a single wave broke, sometimes initiating the breaking of adjacent waves within the train. Channel-wide surges (bores) propagating downstream with distinct turbulent flow fronts, were observed at irregular intervals during and up to 7 hours after peak stage. These bores are mechanically similar to breaking front tidal bores and arid flood bores, and resulted in a sudden increase in flow depth and velocity. When a bore front came into close proximity (within ~10 m) upstream of a train of water surface waves, the waves appeared to break simultaneously generating a localised surge of water upstream, that was covered by the bore travelling downstream. Those trains in which waves did not break during the passage of a bore temporarily reduced in height. In both cases, water surface waves reformed immediately after the surge in the same location. Deposits from the event, were examined in <4 m deep trenches ~0.5 km downstream of the remote camera. These contained laterally extensive lenticular and sheet-like units comprised of varying admixtures of sand and gravel that are attributed to antidunes, and associated transitions from upper-stage-plane-beds. Some of the structures are organised within concave upward sequences which contain downflow shifts between foreset and backset laminae; interpreted as trough fills from chute-and-pools or water surface wave breaking. At least 90% of the deposit is interpreted upper flow regime origin. The sequence, geometry and lamina-scale texture of the sedimentary structures will be discussed with reference to remote camera images of rapidly varying, unsteady and pulsatory flow behaviour.

Emerging trends in the sea state of the Beaufort and Chukchi seas

NASA Astrophysics Data System (ADS)

Thomson, Jim; Fan, Yalin; Stammerjohn, Sharon; Stopa, Justin; Rogers, W. Erick; Girard-Ardhuin, Fanny; Ardhuin, Fabrice; Shen, Hayley; Perrie, Will; Shen, Hui; Ackley, Steve; Babanin, Alex; Liu, Qingxiang; Guest, Peter; Maksym, Ted; Wadhams, Peter; Fairall, Chris; Persson, Ola; Doble, Martin; Graber, Hans; Lund, Bjoern; Squire, Vernon; Gemmrich, Johannes; Lehner, Susanne; Holt, Benjamin; Meylan, Mike; Brozena, John; Bidlot, Jean-Raymond

2016-09-01

The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing, independent of changes in the wind forcing. Wave model hindcasts from four selected years spanning recent conditions are consistent with this expectation. In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally longer. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance. However, trends in the amount of wave energy impinging on the ice-edge are inconclusive, and the associated processes, especially in the autumn period of new ice formation, have yet to be well-described by in situ observations. There is an implicit trend and evidence for increasing wave energy along the coast of northern Alaska, and this coastal signal is corroborated by satellite altimeter estimates of wave energy.

Response of water temperature to surface wave effects in the Baltic Sea: simulations with the coupled NEMO-WAM model

NASA Astrophysics Data System (ADS)

Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter

2016-04-01

The effects of wind waves on the Baltic Sea water temperature has been studied by coupling the hydrodynamical model NEMO with the wave model WAM. The wave forcing terms that have been taken into consideration are: Stokes-Coriolis force, seastate dependent energy flux and sea-state dependent momentum flux. The combined role of these processes as well as their individual contributions on simulated temperature is analysed. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwellinǵs. In northern parts of the Baltic Sea a warming of the surface layer occurs in the wave included simulations. This in turn reduces the cold bias between simulated and measured data. The warming is primarily caused by sea-state dependent energy flux. Wave induced cooling is mostly observed in near coastal areas and is mainly due to Stokes-Coriolis forcing. The latter triggers effect of intensifying upwellings near the coasts, depending on the direction of the wind. The effect of sea-state dependent momentum flux is predominantly to warm the surface layer. During the summer the wave induced water temperature changes were up to 1 °C.

Imaging of underground karst water channels using an improved multichannel transient Rayleigh wave detecting method

PubMed Central

Zheng, Xuhui; Liu, Lei; Li, Gao; Zhou, Fubiao; Xu, Jiemin

2018-01-01

Geological and hydrogeological conditions in karst areas are complicated from the viewpoint of engineering. The construction of underground structures in these areas is often disturbed by the gushing of karst water, which may delay the construction schedule, result in economic losses, and even cause heavy casualties. In this paper, an innovative method of multichannel transient Rayleigh wave detecting is proposed by introducing the concept of arrival time difference phase between channels (TDP). Overcoming the restriction of the space-sampling law, the proposed method can extract the phase velocities of different frequency components from only two channels of transient Rayleigh wave recorded on two adjacent detecting points. This feature greatly improves the work efficiency and lateral resolution of transient Rayleigh wave detecting. The improved multichannel transient Rayleigh wave detecting method is applied to the detection of karst caves and fractures in rock mass of the foundation pit of Yan’an Road Station of Guiyang Metro. The imaging of the detecting results clearly reveals the distribution of karst water inflow channels, which provided significant guidance for water plugging and enabled good control over karst water gushing in the foundation pit. PMID:29883492

Imaging of underground karst water channels using an improved multichannel transient Rayleigh wave detecting method.

PubMed

Zheng, Xuhui; Liu, Lei; Sun, Jinzhong; Li, Gao; Zhou, Fubiao; Xu, Jiemin

2018-01-01

Geological and hydrogeological conditions in karst areas are complicated from the viewpoint of engineering. The construction of underground structures in these areas is often disturbed by the gushing of karst water, which may delay the construction schedule, result in economic losses, and even cause heavy casualties. In this paper, an innovative method of multichannel transient Rayleigh wave detecting is proposed by introducing the concept of arrival time difference phase between channels (TDP). Overcoming the restriction of the space-sampling law, the proposed method can extract the phase velocities of different frequency components from only two channels of transient Rayleigh wave recorded on two adjacent detecting points. This feature greatly improves the work efficiency and lateral resolution of transient Rayleigh wave detecting. The improved multichannel transient Rayleigh wave detecting method is applied to the detection of karst caves and fractures in rock mass of the foundation pit of Yan'an Road Station of Guiyang Metro. The imaging of the detecting results clearly reveals the distribution of karst water inflow channels, which provided significant guidance for water plugging and enabled good control over karst water gushing in the foundation pit.

Theoretical and experimental investigation into structural and fluid motions at low frequencies in water distribution pipes

NASA Astrophysics Data System (ADS)

Gao, Yan; Liu, Yuyou

2017-06-01

Vibrational energy is transmitted in buried fluid-filled pipes in a variety of wave types. Axisymmetric (n = 0) waves are of practical interest in the application of acoustic techniques for the detection of leaks in underground pipelines. At low frequencies n = 0 waves propagate longitudinally as fluid-dominated (s = 1) and shell-dominated (s = 2) waves. Whilst sensors such as hydrophones and accelerometers are commonly used to detect leaks in water distribution pipes, the mechanism governing the structural and fluid motions is not well documented. In this paper, the low-frequency behaviour of the pipe wall and the contained fluid is investigated. For most practical pipework systems, these two waves are strongly coupled; in this circumstance the ratios of the radial pipe wall displacements along with the internal pressures associated with these two wave types are obtained. Numerical examples show the relative insensitivity of the structural and fluid motions to the s = 2 wave for both metallic and plastic pipes buried in two typical soils. It is also demonstrated that although both acoustic and vibration sensors at the same location provide the identical phase information of the transmitted signals, pressure responses have significantly higher levels than acceleration responses, and thus hydrophones are better suited in a low signal-to-noise ratio (SNR) environment. This is supported by experimental work carried out at a leak detection facility. Additional pressure measurements involved excitation of the fluid and the pipe fitting (hydrant) on a dedicated water pipe. This work demonstrates that the s = 1 wave is mainly responsible for the structural and fluid motions at low frequencies in water distribution pipes as a result of water leakage and direct pipe excitation.

Landslide-Generated Waves in a Dam Reservoir: The Effects of Landslide Rheology and Initial Submergence

NASA Astrophysics Data System (ADS)

Yavari Ramsheh, S.; Ataie-Ashtiani, B.

2017-12-01

Recent studies revealed that landslide-generated waves (LGWs) impose the largest tsunami hazard to our shorelines although earthquake-generated waves (EGWs) occur more often. Also, EGWs are commonly followed by a large number of landslide hazards. Dam reservoirs are more vulnerable to landslide events due to being located in mountainous areas. Accurate estimation of such hazards and their destructive consequences help authorities to reduce their risks by constructive measures. In this regard, a two-layer two-phase Coulomb mixture flow (2LCMFlow) model is applied to investigate the effects of landslide characteristics on LGWs for a real-sized simplification of the Maku dam reservoir, located in the North of Iran. A sensitivity analysis is performed on the role of landslide rheological and constitutive parameters and its initial submergence in LGW characteristics and formation patterns. The numerical results show that for a subaerial (SAL), a semi-submerged (SSL), and a submarine landslide (SML) with the same initial geometry, the SSLs can create the largest wave crest, up to 60% larger than SALs, for dense material. However, SMLs generally create the largest wave troughs and SALs travel the maximum runout distances beneath the water. Regarding the two-phase (solid-liquid) nature of the landslide, when interestial water is isolated from the water layer along the water/landslide interface, a LGW with up to 30% higher wave crest can be created. In this condition, increasing the pore water pressure within the granular layer results in up to 35% higher wave trough and 40% lower wave crest at the same time. These results signify the importance of appropriate description of two-phase nature and rheological behavior of landslides in accurate estimation of LGWs which demands further numerical, physical, and field studies about such phenomena.

Variability in Benthic Exchange Rate, Depth, and Residence Time Beneath a Shallow Coastal Estuary

NASA Astrophysics Data System (ADS)

Russoniello, Christopher J.; Heiss, James W.; Michael, Holly A.

2018-03-01

Hydrodynamically driven benthic exchange of water between the water column and shallow seabed aquifer is a significant and dynamic component of coastal and estuarine fluid budgets. Associated exchange of solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times constrains coastal chemical cycling estimates. We present the first combined field, numerical, and analytical modeling investigation of wave-induced exchange. Temporal variability of exchange was calculated with data collected by instruments deployed in a shallow estuary for 11 days. Differential pressure sensors recorded pressure gradients across the seabed, and up- and down-looking ADCPs recorded currents and pressures to determine wave parameters, surface-water currents, and water depth. Wave-induced exchange was calculated (1) directly from differential pressure measurements, and indirectly with an analytical model based on wave parameters from (2) ADCP and (3) wind data. Wave-induced exchange from pressure measurements and ADCP-measured wave parameters matched well, but both exceeded wind-based values. Exchange induced by tidal pumping and current-bed form interaction—the other primary drivers in shallow coastal waters were calculated from tidal stage variation and ADCP-measured currents. Exchange from waves (mean = 20.0 cm/d; range = 1.75-92.3 cm/d) greatly exceeded exchange due to tides (mean = 3.7 cm/d) and current-bed form interaction (mean = 6.5 × 10-2 cm/d). Groundwater flow models showed aquifer properties affect wave-driven benthic exchange: residence time and depth increased and exchange rates decreased with increasing hydraulic diffusivity (ratio of aquifer permeability to compressibility). This new understanding of benthic exchange will help managers assess its control over chemical fluxes to marine systems.

Ice shelf structure derived from dispersion curve analysis of ambient seismic noise, Ross Ice Shelf, Antarctica

NASA Astrophysics Data System (ADS)

Diez, A.; Bromirski, P. D.; Gerstoft, P.; Stephen, R. A.; Anthony, R. E.; Aster, R. C.; Cai, C.; Nyblade, A.; Wiens, D. A.

2016-05-01

An L-configured, three-component short period seismic array was deployed on the Ross Ice Shelf, Antarctica during November 2014. Polarization analysis of ambient noise data from these stations shows linearly polarized waves for frequency bands between 0.2 and 2 Hz. A spectral peak at about 1.6 Hz is interpreted as the resonance frequency of the water column and is used to estimate the water layer thickness below the ice shelf. The frequency band from 4 to 18 Hz is dominated by Rayleigh and Love waves propagating from the north that, based on daily temporal variations, we conclude were generated by field camp activity. Frequency-slowness plots were calculated using beamforming. Resulting Love and Rayleigh wave dispersion curves were inverted for the shear wave velocity profile within the firn and ice to ˜150 m depth. The derived density profile allows estimation of the pore close-off depth and the firn-air content thickness. Separate inversions of Rayleigh and Love wave dispersion curves give different shear wave velocity profiles within the firn. We attribute this difference to an effective anisotropy due to fine layering. The layered structure of firn, ice, water and the seafloor results in a characteristic dispersion curve below 7 Hz. Forward modelling the observed Rayleigh wave dispersion curves using representative firn, ice, water and sediment structures indicates that Rayleigh waves are observed when wavelengths are long enough to span the distance from the ice shelf surface to the seafloor. The forward modelling shows that analysis of seismic data from an ice shelf provides the possibility of resolving ice shelf thickness, water column thickness and the physical properties of the ice shelf and underlying seafloor using passive-source seismic data.

Shock wave-droplet interaction

NASA Astrophysics Data System (ADS)

Habibi Khoshmehr, Hamed; Krechetnikov, Rouslan

2016-11-01

Disintegration of a liquid droplet under the action of a shock wave is experimentally investigated. The shock wave-pulse is electromagnetically generated by discharging a high voltage capacitor into a flat spiral coil, above which an isolated circular metal membrane is placed in a close proximity. The Lorentz force arising due to the eddy current induced in the membrane abruptly accelerates it away from the spiral coil thus generating a shock wave. The liquid droplet placed at the center of the membrane, where the maximum deflection occurs, is disintegrated in the process of interaction with the shock wave. The effects of droplet viscosity and surface tension on the droplet destruction are studied with high-speed photography. Water-glycerol solution at different concentrations is used for investigating the effect of viscosity and various concentrations of water-sugar and water-ethanol solution are used for studying the effect of surface tension. Here we report on how the metamorphoses, which a liquid drop undergoes in the process of interaction with a shock wave, are affected by varied viscosity and surface tension.

Shock wave attenuation by water droplets

NASA Astrophysics Data System (ADS)

Eliasson, Veronica; Wan, Qian; Deiterding, Ralf

2017-11-01

The ongoing research on shock wave attenuation is fueled by the desire to predict and avoid damage caused by shock and blast waves. For example, during an explosion in an underground mine or subway tunnel, the shock front is forced to propagate in the direction of the channel. In this work, numerical simulations using water droplets in a 2D channel are conducted to study shock wave attenuation. Four different droplet configurations (1x1, 2x2, 3x3, and 4x4) are considered, where the total volume of water is kept constant throughout all the cases. Meanwhile, the incident shock Mach number was varied from 1.1 to 1.4 with increments of 0.1. The physical motion of the water droplets, such as the center-of-mass drift and velocity, and the energy exchange between air and water are quantitatively studied. Results for center-of-mass velocity, maximum peak pressure and impulse will be presented for all different cases that were studied. NSF CBET-1437412.

Laboratory Studies of Sea-Ice-Wave Interactions

NASA Astrophysics Data System (ADS)

Monty, J.; Meylan, M. H.; Babanin, A. V.; Toffoli, A.; Bennetts, L.

2016-12-01

A world-first facility for studying the Marginal Ice Zone has been constructed in the Michell Hydrodynamics Laboratory at the University of Melbourne. A 14m long wave tank (0.75m wide, 0.6m deep) resides in a freezer, where air temperature can be controlled down to -15C. This permits the freezing of the water surface. Large stainless steel ice-making trays (up to 4 m long) are also available to create ice of desired thickness and microstructure, which can be lowered onto the water surface. A computer controlled wave generator is capable of creating waves of any desired form. The temperature of the water in the tank can also be controlled between 2 and 30C. The tank frame is constructed of marine-treated wood and the entire tank is glass and acrylic, permitting the use of corrosive fluids, such as salt water. Here we present the first laboratory experiments of break-up of a controlled thickness, fresh water ice sheet impacted by regular and JONSWAP spectrum surface waves. The geometry of the resultant ice-floes is measured with high-resolution, time-resolved imaging, providing the crucial data of floe size distribution. Initial observations show that, in the case of high steepness waves, the primary mechanisms of ice break-up at the ice edge are overwash and rafting, both of which put weight on the ice interior to the ice-water interface. This additional weight (and impact in the case of rafting) breaks more ice, which allows overwash and rafting deeper into the ice sheet, breaking more ice and so on. For lower steepness waves, overwash and rafting are still present but far less significant. Finally, results of vertical ice movement using laser height gauges will be presented showing the attenuation of waves into an ice sheet and through a pack of ice floes. These results are compared with field data and theory available (e.g. Squire & Moore, Nature, 1980 and Kohout et al., Nature, 2014).

Networks of triboelectric nanogenerators for harvesting water wave energy: a potential approach toward blue energy.

PubMed

Chen, Jun; Yang, Jin; Li, Zhaoling; Fan, Xing; Zi, Yunlong; Jing, Qingshen; Guo, Hengyu; Wen, Zhen; Pradel, Ken C; Niu, Simiao; Wang, Zhong Lin

2015-03-24

With 70% of the earth's surface covered with water, wave energy is abundant and has the potential to be one of the most environmentally benign forms of electric energy. However, owing to lack of effective technology, water wave energy harvesting is almost unexplored as an energy source. Here, we report a network design made of triboelectric nanogenerators (TENGs) for large-scale harvesting of kinetic water energy. Relying on surface charging effect between the conventional polymers and very thin layer of metal as electrodes for each TENG, the TENG networks (TENG-NW) that naturally float on the water surface convert the slow, random, and high-force oscillatory wave energy into electricity. On the basis of the measured output of a single TENG, the TENG-NW is expected to give an average power output of 1.15 MW from 1 km(2) surface area. Given the compelling features, such as being lightweight, extremely cost-effective, environmentally friendly, easily implemented, and capable of floating on the water surface, the TENG-NW renders an innovative and effective approach toward large-scale blue energy harvesting from the ocean.

Water pulsejet research. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Payne, P.R.; Brown, R.G.; Brown, J.P.

1979-04-01

The steam water pulsejet (SWPJ) - a modern derivative of the Piot-McHugh putt-putt toy boat - is discussed. Studies have revealed that, like its air-breathing relatives, one type of SWPJ is a type of wave engine. This report first reviews the background literature and then summarizes recent improvements in our understanding of the engine's operation. An appendix attempts to show the various physical processes of the wave engine version in a quantifiable way. At low temperatures, the ideal cycle efficiency of this version is almost identical with the Carnot limit, diverging above a ..delta..T approx. = 150/sup 0/F. Maximum idealmore » cycle efficiency occurs in the 500/sup 0/-600/sup 0/F range, and is 30%-40%. In addition to the two wave engines (simple wave engine, and a wave engine with a water trap), the boundary layer boiler was developed which may but need not involve wave effects and the Piot-cycle. In the latter engine, some water is flashed rapidly to steam in a separate (but connected) compartment and reaches high pressure before the water column (because of its inertia) has moved appreciably. Ideal efficiencies for this cycle can be of the order of 10%-20%. Although a great deal of knowledge was gained, the present program was unsuccessful in applying the newly discovered cycles to build reliable and efficient solar powered pumps.« less

Investigation of the relationship between hurricane waves and extreme runup

NASA Astrophysics Data System (ADS)

Thompson, D. M.; Stockdon, H. F.

2006-12-01

In addition to storm surge, the elevation of wave-induced runup plays a significant role in forcing geomorphic change during extreme storms. Empirical formulations for extreme runup, defined as the 2% exceedence level, are dependent on some measure of significant offshore wave height. Accurate prediction of extreme runup, particularly during hurricanes when wave heights are large, depends on selecting the most appropriate measure of wave height that provides energy to the nearshore system. Using measurements from deep-water wave buoys results in an overprediction of runup elevation. Under storm forcing these large waves dissipate across the shelf through friction, whitecapping and depth-limited breaking before reaching the beach and forcing swash processes. The use of a local, shallow water wave height has been shown to provide a more accurate estimate of extreme runup elevation (Stockdon, et. al. 2006); however, a specific definition of this local wave height has yet to be defined. Using observations of nearshore waves from the U.S. Army Corps of Engineers' Field Research Facility (FRF) in Duck, NC during Hurricane Isabel, the most relevant measure of wave height for use in empirical runup parameterizations was examined. Spatial and temporal variability of the hurricane wave field, which made landfall on September 18, 2003, were modeled using SWAN. Comparisons with wave data from FRF gages and deep-water buoys operated by NOAA's National Data Buoy Center were used for model calibration. Various measures of local wave height (breaking, dissipation-based, etc.) were extracted from the model domain and used as input to the runup parameterizations. Video based observations of runup collected at the FRF during the storm were used to ground truth modeled values. Assessment of the most appropriate measure of wave height can be extended over a large area through comparisons to observations of storm- induced geomorphic change.

Computational methods and traveling wave solutions for the fourth-order nonlinear Ablowitz-Kaup-Newell-Segur water wave dynamical equation via two methods and its applications

NASA Astrophysics Data System (ADS)

Ali, Asghar; Seadawy, Aly R.; Lu, Dianchen

2018-05-01

The aim of this article is to construct some new traveling wave solutions and investigate localized structures for fourth-order nonlinear Ablowitz-Kaup-Newell-Segur (AKNS) water wave dynamical equation. The simple equation method (SEM) and the modified simple equation method (MSEM) are applied in this paper to construct the analytical traveling wave solutions of AKNS equation. The different waves solutions are derived by assigning special values to the parameters. The obtained results have their importance in the field of physics and other areas of applied sciences. All the solutions are also graphically represented. The constructed results are often helpful for studying several new localized structures and the waves interaction in the high-dimensional models.

Effect exerted by a radio wave electromagnetic field on the rheological properties of water and portland-cement systems

NASA Astrophysics Data System (ADS)

Azharonok, V. V.; Belous, N. Kh.; Rodtsevich, S. P.; Koshevar, V. D.; Shkadretsova, V. G.; Goncharik, S. V.; Chubrik, N. I.; Orlovich, A. I.

2013-09-01

We have studied the effect of the regimes of high-frequency (radio wave) electromagnetic treatment of gauging water on the process of structurization and on the technological characteristics of portland-cement systems. It has been established that the radio wave electromagnetic activation of water leads to a reduction in its surface tension, dynamic viscosity, and shear stress, as well as intensifies the formation of coagulation structures in a portlandcement slurry and aids in increasing the mobility of cement-sand mixtures.

The Effect of Vegetation on Sea-Swell Waves, Infragravity Waves and Wave-Induced Setup

NASA Astrophysics Data System (ADS)

Roelvink, J. A.; van Rooijen, A.; McCall, R. T.; Van Dongeren, A.; Reniers, A.; van Thiel de Vries, J.

2016-02-01

Aquatic vegetation in the coastal zone (e.g. mangrove trees) attenuates wave energy and thereby reduces flood risk along many shorelines worldwide. However, in addition to the attenuation of incident-band (sea-swell) waves, vegetation may also affect infragravity-band (IG) waves and the wave-induced water level setup (in short: wave setup). Currently, knowledge on the effect of vegetation on IG waves and wave setup is lacking, while they are they are key parameters for coastal risk assessment. In this study, the process-based storm impact model XBeach was extended with formulations for attenuation of sea-swell and IG waves as well as the effect on the wave setup, in two modes: the sea-swell wave phase-resolving (non-hydrostatic) and the phase-averaged (surfbeat) mode. In surfbeat mode a wave shape model was implemented to estimate the wave phase and to capture the intra-wave scale effect of emergent vegetation and nonlinear waves on the wave setup. Both modeling modes were validated using data from two flume experiments and show good skill in computing the attenuation of both sea-swell and IG waves as well as the effect on the wave-induced water level setup. In surfbeat mode, the prediction of nearshore mean water levels greatly improved when using the wave shape model, while in non-hydrostatic mode this effect is directly accounted for. Subsequently, the model was used to study the influence of the bottom profile slope and the location of the vegetation field on the computed wave setup with and without vegetation. It was found that the reduction is wave setup is strongly related to the location of vegetation relative to the wave breaking point, and that the wave setup is lower for milder slopes. The extended version of XBeach developed within this study can be used to study the nearshore hydrodynamics on coasts fronted by vegetation such as mangroves. It can also serve as tool for storm impact studies on coasts with aquatic vegetation, and can help to quantify the coastal protection function of vegetation.

Wind wave analysis in depth limited water using OCEANLYZ, A MATLAB toolbox

NASA Astrophysics Data System (ADS)

Karimpour, Arash; Chen, Qin

2017-09-01

There are a number of well established methods in the literature describing how to assess and analyze measured wind wave data. However, obtaining reliable results from these methods requires adequate knowledge on their behavior, strengths and weaknesses. A proper implementation of these methods requires a series of procedures including a pretreatment of the raw measurements, and adjustment and refinement of the processed data to provide quality assurance of the outcomes, otherwise it can lead to untrustworthy results. This paper discusses potential issues in these procedures, explains what parameters are influential for the outcomes and suggests practical solutions to avoid and minimize the errors in the wave results. The procedure of converting the water pressure data into the water surface elevation data, treating the high frequency data with a low signal-to-noise ratio, partitioning swell energy from wind sea, and estimating the peak wave frequency from the weighted integral of the wave power spectrum are described. Conversion and recovery of the data acquired by a pressure transducer, particularly in depth-limited water like estuaries and lakes, are explained in detail. To provide researchers with tools for a reliable estimation of wind wave parameters, the Ocean Wave Analyzing toolbox, OCEANLYZ, is introduced. The toolbox contains a number of MATLAB functions for estimation of the wave properties in time and frequency domains. The toolbox has been developed and examined during a number of the field study projects in Louisiana's estuaries.

Observation of wave celerity evolution in the nearshore using digital video imagery

NASA Astrophysics Data System (ADS)

Yoo, J.; Fritz, H. M.; Haas, K. A.; Work, P. A.; Barnes, C. F.; Cho, Y.

2008-12-01

Celerity of incident waves in the nearshore is observed from oblique video imagery collected at Myrtle Beach, S.C.. The video camera covers the field view of length scales O(100) m. Celerity of waves propagating in shallow water including the surf zone is estimated by applying advanced image processing and analysis methods to the individual video images sampled at 3 Hz. Original image sequences are processed through video image frame differencing, directional low-pass image filtering to reduce the noise arising from foam in the surf zone. The breaking wave celerity is computed along a cross-shore transect from the wave crest tracks extracted by a Radon transform-based line detection method. The observed celerity from the nearshore video imagery is larger than the linear wave celerity computed from the measured water depths over the entire surf zone. Compared to the nonlinear shallow water wave equation (NSWE)-based celerity computed using the measured depths and wave heights, in general, the video-based celerity shows good agreements over the surf zone except the regions across the incipient wave breaking locations. In the regions across the breaker points, the observed wave celerity is even larger than the NSWE-based celerity due to the transition of wave crest shapes. The observed celerity using the video imagery can be used to monitor the nearshore geometry through depth inversion based on the nonlinear wave celerity theories. For this purpose, the exceeding celerity across the breaker points needs to be corrected accordingly compared to a nonlinear wave celerity theory applied.

Surface-wave-sustained plasma torch for water treatment

NASA Astrophysics Data System (ADS)

Marinova, P.; Benova, E.; Todorova, Y.; Topalova, Y.; Yotinov, I.; Atanasova, M.; Krcma, F.

2018-02-01

In this study the effects of water treatment by surface-wave-sustained plasma torch at 2.45 GHz are studied. Changes in two directions are obtained: (i) changes of the plasma characteristics during the interaction with the water; (ii) water physical and chemical characteristics modification as a result of the plasma treatment. In addition, deactivation of Gram positive and Gram negative bacteria in suspension are registered. A number of charged and excited particles from the plasma interact with the water. As a result the water chemical and physical characteristics such as the water conductivity, pH, H2O2 concentration are modified. It is observed that the effect depends on the treatment time, wave power, and volume of the treated liquid. At specific discharge conditions determined by the wave power, gas flow, discharge tube radius, thickness and permittivity, the surface-wave-sustained discharge (SWD) operating at atmospheric pressure in argon is strongly non-equilibrium with electron temperature T e much higher than the temperature of the heavy particles (gas temperature T g). It has been observed that SWD argon plasma with T g close to the room temperature is able to produce H2O2 in the water with high efficiency at short exposure times (less than 60 sec). The H2O2 decomposition is strongly dependant on the temperature thus the low operating gas temperature is crucial for the H2O2 production efficiency. After scaling up the device, the observed effects can be applied for the waste water treatment in different facilities. The innovation will be useful especially for the treatment of waters and materials for medical application.

Physical and Biological Controls on the Carbonate Chemistry of Coral Reef Waters: Effects of Metabolism, Wave Forcing, Sea Level, and Geomorphology

PubMed Central

Falter, James L.; Lowe, Ryan J.; Zhang, Zhenlin; McCulloch, Malcolm

2013-01-01

We present a three-dimensional hydrodynamic-biogeochemical model of a wave-driven coral-reef lagoon system using the circulation model ROMS (Regional Ocean Modeling System) coupled with the wave transformation model SWAN (Simulating WAves Nearshore). Simulations were used to explore the sensitivity of water column carbonate chemistry across the reef system to variations in benthic reef metabolism, wave forcing, sea level, and system geomorphology. Our results show that changes in reef-water carbonate chemistry depend primarily on the ratio of benthic metabolism to the square root of the onshore wave energy flux as well as on the length and depth of the reef flat; however, they are only weakly dependent on channel geometry and the total frictional resistance of the reef system. Diurnal variations in pCO2, pH, and aragonite saturation state (Ωar) are primarily dependent on changes in net production and are relatively insensitive to changes in net calcification; however, net changes in pCO2, pH, and Ωar are more strongly influenced by net calcification when averaged over 24 hours. We also demonstrate that a relatively simple one-dimensional analytical model can provide a good description of the functional dependence of reef-water carbonate chemistry on benthic metabolism, wave forcing, sea level, reef flat morphology, and total system frictional resistance. Importantly, our results indicate that any long-term (weeks to months) net offsets in reef-water pCO2 relative to offshore values should be modest for reef systems with narrow and/or deep lagoons. Thus, the long-term evolution of water column pCO2 in many reef environments remains intimately connected to the regional-scale oceanography of offshore waters and hence directly influenced by rapid anthropogenically driven increases in pCO2. PMID:23326411

Physical and biological controls on the carbonate chemistry of coral reef waters: effects of metabolism, wave forcing, sea level, and geomorphology.

PubMed

Falter, James L; Lowe, Ryan J; Zhang, Zhenlin; McCulloch, Malcolm

2013-01-01

We present a three-dimensional hydrodynamic-biogeochemical model of a wave-driven coral-reef lagoon system using the circulation model ROMS (Regional Ocean Modeling System) coupled with the wave transformation model SWAN (Simulating WAves Nearshore). Simulations were used to explore the sensitivity of water column carbonate chemistry across the reef system to variations in benthic reef metabolism, wave forcing, sea level, and system geomorphology. Our results show that changes in reef-water carbonate chemistry depend primarily on the ratio of benthic metabolism to the square root of the onshore wave energy flux as well as on the length and depth of the reef flat; however, they are only weakly dependent on channel geometry and the total frictional resistance of the reef system. Diurnal variations in pCO(2), pH, and aragonite saturation state (Ω(ar)) are primarily dependent on changes in net production and are relatively insensitive to changes in net calcification; however, net changes in pCO(2), pH, and Ω(ar) are more strongly influenced by net calcification when averaged over 24 hours. We also demonstrate that a relatively simple one-dimensional analytical model can provide a good description of the functional dependence of reef-water carbonate chemistry on benthic metabolism, wave forcing, sea level, reef flat morphology, and total system frictional resistance. Importantly, our results indicate that any long-term (weeks to months) net offsets in reef-water pCO(2) relative to offshore values should be modest for reef systems with narrow and/or deep lagoons. Thus, the long-term evolution of water column pCO(2) in many reef environments remains intimately connected to the regional-scale oceanography of offshore waters and hence directly influenced by rapid anthropogenically driven increases in pCO(2).

Operational wave now- and forecast in the German Bight as a basis for the assessment of wave-induced hydrodynamic loads on coastal dikes

NASA Astrophysics Data System (ADS)

Dreier, Norman; Fröhle, Peter

2017-12-01

The knowledge of the wave-induced hydrodynamic loads on coastal dikes including their temporal and spatial resolution on the dike in combination with actual water levels is of crucial importance of any risk-based early warning system. As a basis for the assessment of the wave-induced hydrodynamic loads, an operational wave now- and forecast system is set up that consists of i) available field measurements from the federal and local authorities and ii) data from numerical simulation of waves in the German Bight using the SWAN wave model. In this study, results of the hindcast of deep water wave conditions during the winter storm on 5-6 December, 2013 (German name `Xaver') are shown and compared with available measurements. Moreover field measurements of wave run-up from the local authorities at a sea dike on the German North Sea Island of Pellworm are presented and compared against calculated wave run-up using the EurOtop (2016) approach.

Predicting Waves in the Pacific Northwest of the US

NASA Astrophysics Data System (ADS)

Ozkan-Haller, H. T.; Oskamp, J. A.; Garcia, G.; Kassem, S.; McNutt, J.

2010-12-01

The Pacific Northwest region of the US is characterized by an energetic deep water wave climate with large swell and sea waves that can approach from multiple directions. As these waves propagate from the open ocean over the continental shelf towards shore, they are affected by the underwater topography (or bathymetry) of the shelf. The US West Coast shelf is characterized by complicated bathymetry with numerous canyons and large banks. Such features can at places focus wave energy and at others divert waves away. As a result the wave field near the coast (in 10-50m water depth) varies significantly along the coast. Although a comprehensive prediction and validation effort for waves exists for the California shoreline, it is currently lacking for the Pacific Northwest shorelines. Herein, we present comprehensive long-term wave model simulations for several regions within the Oregon coastline, show validation of the results with existing nearshore observations, and discuss the dominant dynamics responsible for the observed wave transformation.

Reduced-order prediction of rogue waves in two-dimensional deep-water waves

NASA Astrophysics Data System (ADS)

Farazmand, Mohammad; Sapsis, Themistoklis P.

2017-07-01

We consider the problem of large wave prediction in two-dimensional water waves. Such waves form due to the synergistic effect of dispersive mixing of smaller wave groups and the action of localized nonlinear wave interactions that leads to focusing. Instead of a direct simulation approach, we rely on the decomposition of the wave field into a discrete set of localized wave groups with optimal length scales and amplitudes. Due to the short-term character of the prediction, these wave groups do not interact and therefore their dynamics can be characterized individually. Using direct numerical simulations of the governing envelope equations we precompute the expected maximum elevation for each of those wave groups. The combination of the wave field decomposition algorithm, which provides information about the statistics of the system, and the precomputed map for the expected wave group elevation, which encodes dynamical information, allows (i) for understanding of how the probability of occurrence of rogue waves changes as the spectrum parameters vary, (ii) the computation of a critical length scale characterizing wave groups with high probability of evolving to rogue waves, and (iii) the formulation of a robust and parsimonious reduced-order prediction scheme for large waves. We assess the validity of this scheme in several cases of ocean wave spectra.

Surface Wave Velocity of Crosslinked Polyacrylate Gels

NASA Astrophysics Data System (ADS)

Matsuoka, Tatsuro; Kinouchi, Wataru; ShinobuKoda, ShinobuKoda; Nomura, Hiroyasu

1999-05-01

Surface wave velocities of crosslinked polyacrylate hydrogelswere measured as a function of water content with differentcompositions of sodium polyacrylate (NaPA) and polyacrylic acid (PAA).The water content and composition dependencies of the surface wavevelocity were discussed.

"Slowing" Mechanical Waves with a Consumer-Type High-Speed Digital Camera

ERIC Educational Resources Information Center

Ng, Pun-hon; Chan, Kin-lok

2015-01-01

In most secondary physics textbooks, waves are first introduced with examples of mechanical waves because they can be illustrated by drawings and photographs. However, these illustrations are static and cannot reflect the dynamic nature of waves. Although many mechanical waves (e.g. water waves and vibrating strings) can be easily shown using…

Solvability of the Initial Value Problem to the Isobe-Kakinuma Model for Water Waves

NASA Astrophysics Data System (ADS)

Nemoto, Ryo; Iguchi, Tatsuo

2017-09-01

We consider the initial value problem to the Isobe-Kakinuma model for water waves and the structure of the model. The Isobe-Kakinuma model is the Euler-Lagrange equations for an approximate Lagrangian which is derived from Luke's Lagrangian for water waves by approximating the velocity potential in the Lagrangian. The Isobe-Kakinuma model is a system of second order partial differential equations and is classified into a system of nonlinear dispersive equations. Since the hypersurface t=0 is characteristic for the Isobe-Kakinuma model, the initial data have to be restricted in an infinite dimensional manifold for the existence of the solution. Under this necessary condition and a sign condition, which corresponds to a generalized Rayleigh-Taylor sign condition for water waves, on the initial data, we show that the initial value problem is solvable locally in time in Sobolev spaces. We also discuss the linear dispersion relation to the model.

On periodic geophysical water flows with discontinuous vorticity in the equatorial f-plane approximation.

PubMed

Martin, Calin Iulian

2018-01-28

We are concerned here with geophysical water waves arising as the free surface of water flows governed by the f -plane approximation. Allowing for an arbitrary bounded discontinuous vorticity, we prove the existence of steady periodic two-dimensional waves of small amplitude. We illustrate the local bifurcation result by means of an analysis of the dispersion relation for a two-layered fluid consisting of a layer of constant non-zero vorticity γ 1 adjacent to the surface situated above another layer of constant non-zero vorticity γ 2 ≠ γ 1 adjacent to the bed. For certain vorticities γ 1 , γ 2 , we also provide estimates for the wave speed c in terms of the speed at the surface of the bifurcation inducing laminar flows.This article is part of the theme issue 'Nonlinear water waves'. © 2017 The Author(s).

Military Training: Observations on Efforts to Prepare Personnel to Survive Helicopter Crashes into Water

DTIC Science & Technology

2014-07-14

Air Force Environmental conditions simulation equipment Equipment that simulates conditions such as waves, wind, rain, thunder , lightning , and...Environmental conditions simulation equipment Equipment that simulates conditions such as waves, wind, rain, thunder , lightning , and combat sounds...items such as wave generators, heavy-duty fans to simulate high winds, strobe lights to simulate lightning , water spray and injection systems to

Wave friction factor rediscovered

NASA Astrophysics Data System (ADS)

Le Roux, J. P.

2012-02-01

The wave friction factor is commonly expressed as a function of the horizontal water particle semi-excursion ( A wb) at the top of the boundary layer. A wb, in turn, is normally derived from linear wave theory by {{U_{{wb}}/T_{{w}}}}{{2π }} , where U wb is the maximum water particle velocity measured at the top of the boundary layer and T w is the wave period. However, it is shown here that A wb determined in this way deviates drastically from its real value under both linear and non-linear waves. Three equations for smooth, transitional and rough boundary conditions, respectively, are proposed to solve this problem, all three being a function of U wb, T w, and δ, the thickness of the boundary layer. Because these variables can be determined theoretically for any bottom slope and water depth using the deepwater wave conditions, there is no need to physically measure them. Although differing substantially from many modern attempts to define the wave friction factor, the results coincide with equations proposed in the 1960s for either smooth or rough boundary conditions. The findings also confirm that the long-held notion of circular water particle motion down to the bottom in deepwater conditions is erroneous, the motion in fact being circular at the surface and elliptical at depth in both deep and shallow water conditions, with only horizontal motion at the top of the boundary layer. The new equations are incorporated in an updated version (WAVECALC II) of the Excel program published earlier in this journal by Le Roux et al. Geo-Mar Lett 30(5): 549-560, (2010).

Application of oil-water discrimination technology in fractured reservoirs using the differences between fast and slow shear-waves

NASA Astrophysics Data System (ADS)

Luo, Cong; Li, Xiangyang; Huang, Guangtan

2017-08-01

Oil-water discrimination is of great significance in the design and adjustment of development projects in oil fields. For fractured reservoirs, based on anisotropic S-wave splitting information, it becomes possible to effectively solve such problems which are difficult to deal with in traditional longitudinal wave exploration, due to the similar bulk modulus and density of these two fluids. In this paper, by analyzing the anisotropic character of the Chapman model (2009 Geophysics 74 97-103), the velocity and reflection coefficient differences between the fast and slow S-wave caused by fluid substitution have been verified. Then, through a wave field response analysis of the theoretical model, we found that water saturation causes a longer time delay, a larger time delay gradient and a lower amplitude difference between the fast and slow S-wave, while the oil case corresponds to a lower time delay, a lower gradient and a higher amplitude difference. Therefore, a new class attribute has been proposed regarding the amplitude energy of the fast and slow shear wave, used for oil-water distinction. This new attribute, as well as that of the time delay gradient, were both applied to the 3D3C seismic data of carbonate fractured reservoirs in the Luojia area of the Shengli oil field in China. The results show that the predictions of the energy attributes are more consistent with the well information than the time delay gradient attribute, hence demonstrating the great advantages and potential of this new attribute in oil-water recognition.

Theoretical and experimental evidence of non-symmetric doubly localized rogue waves.

PubMed

He, Jingsong; Guo, Lijuan; Zhang, Yongshuai; Chabchoub, Amin

2014-11-08

We present determinant expressions for vector rogue wave (RW) solutions of the Manakov system, a two-component coupled nonlinear Schrödinger (NLS) equation. As a special case, we generate a family of exact and non-symmetric RW solutions of the NLS equation up to third order, localized in both space and time. The derived non-symmetric doubly localized second-order solution is generated experimentally in a water wave flume for deep-water conditions. Experimental results, confirming the characteristic non-symmetric pattern of the solution, are in very good agreement with theory as well as with numerical simulations, based on the modified NLS equation, known to model accurately the dynamics of weakly nonlinear wave packets in deep water.

Theoretical and experimental evidence of non-symmetric doubly localized rogue waves

PubMed Central

He, Jingsong; Guo, Lijuan; Zhang, Yongshuai; Chabchoub, Amin

2014-01-01

We present determinant expressions for vector rogue wave (RW) solutions of the Manakov system, a two-component coupled nonlinear Schrödinger (NLS) equation. As a special case, we generate a family of exact and non-symmetric RW solutions of the NLS equation up to third order, localized in both space and time. The derived non-symmetric doubly localized second-order solution is generated experimentally in a water wave flume for deep-water conditions. Experimental results, confirming the characteristic non-symmetric pattern of the solution, are in very good agreement with theory as well as with numerical simulations, based on the modified NLS equation, known to model accurately the dynamics of weakly nonlinear wave packets in deep water. PMID:25383023

Wind-forced modulations in crossing sea states over infinite depth water

NASA Astrophysics Data System (ADS)

Debsarma, Suma; Senapati, Sudipta; Das, K. P.

2014-09-01

The present work is motivated by the work of Leblanc ["Amplification of nonlinear surface waves by wind," Phys. Fluids 19, 101705 (2007)] which showed that Stokes waves grow super exponentially under fair wind as a result of modulational instability. Here, we have studied the effect of wind in a situation of crossing sea states characterized by two obliquely propagating wave systems in deep water. It is found that the wind-forced uniform wave solution in crossing seas grows explosively with a super-exponential growth rate even under a steady horizontal wind flow. This is an important piece of information in the context of the formation of freak waves.

Internal solitary waves on the Saya de Malha bank of the Mascarene Plateau: SAR observations and interpretation

NASA Astrophysics Data System (ADS)

New, A. L.; Magalhaes, J. M.; da Silva, J. C. B.

2013-09-01

Energetic Internal Solitary Waves (ISWs) were recently discovered radiating from the central region of the Mascarene Plateau in the south-western Indian Ocean (da Silva et al., 2011). SAR imagery revealed the two-dimensional structure of the waves which propagated for several hundred kilometres in deep water both to the east and west of a sill, located near 12.5°S, 61°E between the Saya de Malha and Nazareth banks. These waves were presumed to originate from the disintegration of a large lee wave formed on the western side of the sill at the time of maximum barotropic flow to the west. In the present paper we focus instead on ISWs propagating in the shallow water above the Saya da Malha (SM) bank (to the north of the sill), rather than on those propagating in deep water (here denominated as type-I or -II waves if propagating to the west or east respectively). Analysis of an extended SAR image dataset reveals strong sea surface signatures of complex patterns of ISWs propagating over the SM bank arising from different sources. We identify three distinct types of waves, and propose suitable generation mechanisms for them using synergy from different remotely sensed datasets, together with analyses of linear phase speeds (resulting from local stratification and bathymetry). In particular, we find a family of ISWs (termed here A-type waves) which results from the disintegration of a lee wave which forms on the western slopes of SM. We also identify two further wave trains (B- and C-type waves) which we suggest result from refraction of the deep water type-I and -II waves onto the SM bank. Therefore, both B- and C-type waves can be considered to result from the same generation source as the type-I and -II waves. Finally, we consider the implications of the ISWs for mixing and biological production over the SM bank, and provide direct evidence, from ocean colour satellite images, of enhanced surface chlorophyll over a shallow topographic feature on the bank, which is consistent with the breaking of the ISWs.

Mechanisms of wave‐driven water level variability on reef‐fringed coastlines

USGS Publications Warehouse

Buckley, Mark L.; Lowe, Ryan J.; Hansen, Jeff E; van Dongeren, Ap R.; Storlazzi, Curt

2018-01-01

Wave‐driven water level variability (and runup at the shoreline) is a significant cause of coastal flooding induced by storms. Wave runup is challenging to predict, particularly along tropical coral reef‐fringed coastlines due to the steep bathymetric profiles and large bottom roughness generated by reef organisms, which can violate assumptions in conventional models applied to open sandy coastlines. To investigate the mechanisms of wave‐driven water level variability on a reef‐fringed coastline, we performed a set of laboratory flume experiments on an along‐shore uniform bathymetric profile with and without bottom roughness. Wave setup and waves at frequencies lower than the incident sea‐swell forcing (infragravity waves) were found to be the dominant components of runup. These infragravity waves were positively correlated with offshore wave groups, signifying they were generated in the surf zone by the oscillation of the breakpoint. On the reef flat and at the shoreline, the low‐frequency waves formed a standing wave pattern with energy concentrated at the natural frequencies of the reef flat, indicating resonant amplification. Roughness elements used in the flume to mimic large reef bottom roughness reduced low frequency motions on the reef flat and reduced wave run up by 30% on average, compared to the runs over a smooth bed. These results provide insight into sea‐swell and infragravity wave transformation and wave setup dynamics on steep‐sloped coastlines, and the effect that future losses of reef bottom roughness may have on coastal flooding along reef‐fringed coasts.

Particle motions beneath irrotational water waves

NASA Astrophysics Data System (ADS)

Bakhoday-Paskyabi, Mostafa

2015-08-01

Neutral and buoyant particle motions in an irrotational flow are investigated under the passage of linear, nonlinear gravity, and weakly nonlinear solitary waves at a constant water depth. The developed numerical models for the particle trajectories in a non-turbulent flow incorporate particle momentum, size, and mass (i.e., inertial particles) under the influence of various surface waves such as Korteweg-de Vries waves which admit a three parameter family of periodic cnoidal wave solutions. We then formulate expressions of mass-transport velocities for the neutral and buoyant particles. A series of test cases suggests that the inertial particles possess a combined horizontal and vertical drifts from the locations of their release, with a fall velocity as a function of particle material properties, ambient flow, and wave parameters. The estimated solutions exhibit good agreement with previously explained particle behavior beneath progressive surface gravity waves. We further investigate the response of a neutrally buoyant water parcel trajectories in a rotating fluid when subjected to a series of wind and wave events. The results confirm the importance of the wave-induced Coriolis-Stokes force effect in both amplifying (destroying) the pre-existing inertial oscillations and in modulating the direction of the flow particles. Although this work has mainly focused on wave-current-particle interaction in the absence of turbulence stochastic forcing effects, the exercise of the suggested numerical models provides additional insights into the mechanisms of wave effects on the passive trajectories for both living and nonliving particles such as swimming trajectories of plankton in non-turbulent flows.

Investigation of Seepage Meter Measurements in Steady Flow and Wave Conditions.

PubMed

Russoniello, Christopher J; Michael, Holly A

2015-01-01

Water exchange between surface water and groundwater can modulate or generate ecologically important fluxes of solutes across the sediment-water interface. Seepage meters can directly measure fluid flux, but mechanical resistance and surface water dynamics may lead to inaccurate measurements. Tank experiments were conducted to determine effects of mechanical resistance on measurement efficiency and occurrence of directional asymmetry that could lead to erroneous net flux measurements. Seepage meter efficiency was high (average of 93%) and consistent for inflow and outflow under steady flow conditions. Wave effects on seepage meter measurements were investigated in a wave flume. Seepage meter net flux measurements averaged 0.08 cm/h-greater than the expected net-zero flux, but significantly less than theoretical wave-driven unidirectional discharge or recharge. Calculations of unidirectional flux from pressure measurements (Darcy flux) and theory matched well for a ratio of wave length to water depth less than 5, but not when this ratio was greater. Both were higher than seepage meter measurements of unidirectional flux made with one-way valves. Discharge averaged 23% greater than recharge in both seepage meter measurements and Darcy calculations of unidirectional flux. Removal of the collection bag reduced this net discharge. The presence of a seepage meter reduced the amplitude of pressure signals at the bed and resulted in a nearly uniform pressure distribution beneath the seepage meter. These results show that seepage meters may provide accurate measurements of both discharge and recharge under steady flow conditions and illustrate the potential measurement errors associated with dynamic wave environments. © 2014, National Ground Water Association.

Statistics for long irregular wave run-up on a plane beach from direct numerical simulations

NASA Astrophysics Data System (ADS)

Didenkulova, Ira; Senichev, Dmitry; Dutykh, Denys

2017-04-01

Very often for global and transoceanic events, due to the initial wave transformation, refraction, diffraction and multiple reflections from coastal topography and underwater bathymetry, the tsunami approaches the beach as a very long wave train, which can be considered as an irregular wave field. The prediction of possible flooding and properties of the water flow on the coast in this case should be done statistically taking into account the formation of extreme (rogue) tsunami wave on a beach. When it comes to tsunami run-up on a beach, the most used mathematical model is the nonlinear shallow water model. For a beach of constant slope, the nonlinear shallow water equations have rigorous analytical solution, which substantially simplifies the mathematical formulation. In (Didenkulova et al. 2011) we used this solution to study statistical characteristics of the vertical displacement of the moving shoreline and its horizontal velocity. The influence of the wave nonlinearity was approached by considering modifications of probability distribution of the moving shoreline and its horizontal velocity for waves of different amplitudes. It was shown that wave nonlinearity did not affect the probability distribution of the velocity of the moving shoreline, while the vertical displacement of the moving shoreline was affected substantially demonstrating the longer duration of coastal floods with an increase in the wave nonlinearity. However, this analysis did not take into account the actual transformation of irregular wave field offshore to oscillations of the moving shoreline on a slopping beach. In this study we would like to cover this gap by means of extensive numerical simulations. The modeling is performed in the framework of nonlinear shallow water equations, which are solved using a modern shock-capturing finite volume method. Although the shallow water model does not pursue the wave breaking and bore formation in a general sense (including the water surface overturning), it allows shock-wave formation and propagation with the speed given by Rankine-Hugoniot jump conditions, which to some extent approximates wave breaking. The scheme is second order accurate thanks to the UNO2 special reconstruction. It was described and validated in (Dutykh et al. 2011a) and has already been successfully used to simulate wave run-up on random beaches (Dutykh et al. 2011b). For simplicity the incident wave field offshore is taken Gaussian in the present study, however, this distribution can be easily changed in the numerical code. Similar to (Didenkulova et al. 2011), in order to study influence of wave nonlinearity during wave propagation to the coast we consider waves of different amplitudes and the corresponding modifications of statistics of the moving shoreline. We also consider wave fields with a different bandwidth, so that we can see the influence of the bandwidth of the incoming wave field on statistics of wave run-up on a beach. In order to validate the numerical results we use the available experimental data of irregular wave run-up on a beach (Denissenko et al. 2011; 2013). For this in our simulations we use the corresponding bathymetry set-up: the flat part of the flume with a water depth of 3.5 m is matched with the beach of constant slope 1:6. The significant wave heights Hs are chosen according to (Denissenko et al. 2013) and are equal to 0.1m, 0.2m, 0.3m, 0.4m and 0.5m, while the bandwidth is selected as 0.1, 0.4 and 0.8, which allows comparison of the behavior of wide-band and narrow-band wave fields on the beach. The characteristic wave period is 20s, as in (Denissenko et al. 2013) that provides long wave condition. All time records contain several weeks of simulations that provides significant amount of data for extreme value statistics. [1] P. Denissenko, I. Didenkulova, E. Pelinovsky, J. Pearson. Influence of the nonlinearity on statistical characteristics of long wave runup. Nonlinear Processes in Geophysics 18, 967-975 (2011). [2] P. Denissenko, I. Didenkulova, A. Rodin, M. Listak, E. Pelinovsky. Experimental statistics of long wave runup on a plane beach. Journal of Coastal Research 65, 195-200 (2013). [3] I. Didenkulova, E. Pelinovsky, A. Sergeeva. Statistical characteristics of long waves nearshore. Coastal Engineering 58, 94-102 (2011). [4] D. Dutykh, T. Katsaounis, D. Mitsotakis. Finite volume schemes for dispersive wave propagation and runup. J. Comput. Phys. 230 (8), 3035-3061 (2011a). [5] D. Dutykh, C. Labart, D. Mitsotakis. Long wave run-up on random beaches. Phys. Rev. Lett. 107, 184504 (2011b).

Light Meets Water in Nonlocal Media: Surface Tension Analogue in Optics

NASA Astrophysics Data System (ADS)

Horikis, Theodoros P.; Frantzeskakis, Dimitrios J.

2017-06-01

Shallow water wave phenomena find their analogue in optics through a nonlocal nonlinear Schrödinger (NLS) model in 2 +1 dimensions. We identify an analogue of surface tension in optics, namely, a single parameter depending on the degree of nonlocality, which changes the sign of dispersion, much like surface tension does in the shallow water wave problem. Using multiscale expansions, we reduce the NLS model to a Kadomtsev-Petviashvili (KP) equation, which is of the KPII (KPI) type, for strong (weak) nonlocality. We demonstrate the emergence of robust optical antidark solitons forming Y -, X -, and H -shaped wave patterns, which are approximated by colliding KPII line solitons, similar to those observed in shallow waters.

Light Meets Water in Nonlocal Media: Surface Tension Analogue in Optics.

PubMed

Horikis, Theodoros P; Frantzeskakis, Dimitrios J

2017-06-16

Shallow water wave phenomena find their analogue in optics through a nonlocal nonlinear Schrödinger (NLS) model in 2+1 dimensions. We identify an analogue of surface tension in optics, namely, a single parameter depending on the degree of nonlocality, which changes the sign of dispersion, much like surface tension does in the shallow water wave problem. Using multiscale expansions, we reduce the NLS model to a Kadomtsev-Petviashvili (KP) equation, which is of the KPII (KPI) type, for strong (weak) nonlocality. We demonstrate the emergence of robust optical antidark solitons forming Y-, X-, and H-shaped wave patterns, which are approximated by colliding KPII line solitons, similar to those observed in shallow waters.

Observations of internal waves in the Gulf of California by SEASAT SAR

NASA Technical Reports Server (NTRS)

Fu, L. L.; Holt, B.

1983-01-01

Internal waves which are among the most commonly observed oceanic phenomena in the SEASAT SAR imagery are discussed. These waves are associated with the vertical displacements of constant water density surfaces in the ocean. Their amplitudes are maximum at depths where the water density changes most rapidly usually at depths from 50 to 100 m, whereas the horizontal currents associated with these waves are maximum at the sea surface where the resulting oscillatory currents modulate the sea surface roughness and produce the signatures detected by SAR.

Observations of internal waves in the Gulf of California by SEASAT SAR

NASA Astrophysics Data System (ADS)

Fu, L. L.; Holt, B.

1983-07-01

Internal waves which are among the most commonly observed oceanic phenomena in the SEASAT SAR imagery are discussed. These waves are associated with the vertical displacements of constant water density surfaces in the ocean. Their amplitudes are maximum at depths where the water density changes most rapidly usually at depths from 50 to 100 m, whereas the horizontal currents associated with these waves are maximum at the sea surface where the resulting oscillatory currents modulate the sea surface roughness and produce the signatures detected by SAR.

Physiological and Biochemical Responses of Saltmarsh Plant Spartina alterniflora to Long-term Wave Exposure

NASA Astrophysics Data System (ADS)

Zhou, W.

2017-12-01

In recent years, ecosystem-based flood defence, i.e., eco-shoreline or living shoreline, that is more sustainable and cost-effective than conventional coastal engineering structures has been brought into large-scale practice. Numerous laboratory experiments have been performed to explore the wave-attenuation effects of saltmarsh plants that are widely used in eco-shoreline, and yet no study has ever been conducted on the physiological and biochemical responses of saltmarsh plants to long-term wave exposure, presumably due to the constraint that traditional wave generator fails to provide long-term stable wave conditions necessary for physiological experiments. In this study, a long-term shallow water wave environment simulator using crank-yoke mechanism was built in the laboratory to address this gap. Experiments using the wave simulator were conducted for 8 weeks in a greenhouse and the temperature was maintained at 24-30°C. 5‰ artificial sea water was filled in the test tank, and the water was changed every week. After being acclimatized, nine S. alterniflora individual plants (initial height 30 cm) were planted in each of the three streamlined cuboid containers (12cm×12cm×20cm), which were partially submerged in a test tank, and undertook horizontal sinusoidal motion imposed by the crank-yoke mechanism to mimic plants exposed to shallow water waves. The substrate filled in the containers were soils collected from the Yellow River Delta, so were the S. alterniflora plants. A realistic stem density of 400 stems/m2 was tested, which corresponded to a grid spacing of 5.0 cm. Shallow water waves with six wave heights (H: 0.041, 0.055, 0.069, 0.033, 0.044 and 0.056m), one plants submerged depth (0.1m) and two wave periods (2s and 3s) were simulated in the experiments. A no wave condition was also tested as control. Key physiological and biochemical parameters, such as stem length, peroxidase activity, catalase, superoxide dismutase, ascorbate peroxidase, etc. were measured on a weekly basis to monitor the plant response. Differences among the various groups were analyzed using repeated measures ANOVA to check for significance (P < 0.05). The results can help inform eco-shoreline projects in terms of plant selection and transplantation timing optimization, etc.

Azimuth cut-off model for significant wave height investigation along coastal water of Kuala Terengganu, Malaysia

NASA Astrophysics Data System (ADS)

Marghany, Maged; Ibrahim, Zelina; Van Genderen, Johan

2002-11-01

The present work is used to operationalize the azimuth cut-off concept in the study of significant wave height. Three ERS-1 images have been used along the coastal waters of Terengganu, Malaysia. The quasi-linear transform was applied to map the SAR wave spectra into real ocean wave spectra. The azimuth cut-off was then used to model the significant wave height. The results show that azimuth cut-off varied with the different period of the ERS-1 images. This is because of the fact that the azimuth cut-off is a function of wind speed and significant wave height. It is of interest to find that the significant wave height modeled from azimuth cut-off is in good relation with ground wave conditions. It can be concluded that ERS-1 can be used as a monitoring tool in detecting the significant wave height variation. The azimuth cut-off can be used to model the significant wave height. This means that the quasi-linear transform could be a good application to significant wave height variation during different seasons.

Assessing the performance of formulations for nonlinear feedback of surface gravity waves on ocean currents over coastal waters

NASA Astrophysics Data System (ADS)

Wang, Pengcheng; Sheng, Jinyu; Hannah, Charles

2017-08-01

This study presents applications of a two-way coupled wave-circulation modelling system over coastal waters, with a special emphasis of performance assessments of two different methods for nonlinear feedback of ocean surface gravity waves on three-dimensional (3D) ocean currents. These two methods are the vortex force (VF) formulation suggested by Bennis et al. (2011) and the latest version of radiation stress (RS) formulation suggested by Mellor (2015). The coupled modelling system is first applied to two idealized test cases of surf-zone scales to validate implementations of these two methods in the coupled wave-circulation system. Model results show that the latest version of RS has difficulties in producing the undertow over the surf zone. The coupled system is then applied to Lunenburg Bay (LB) of Nova Scotia during Hurricane Juan in 2003. The coupled system using both the VF and RS formulations generates much stronger and more realistic 3D circulation in the Bay during Hurricane Juan than the circulation-only model, demonstrating the importance of surface wave forces to the 3D ocean circulation over coastal waters. However, the RS formulation generates some weak unphysical currents outside the wave breaking zone due to a less reasonable representation for the vertical distribution of the RS gradients over a slopping bottom. These weak unphysical currents are significantly magnified in a two-way coupled system when interacting with large surface waves, degrading the model performance in simulating currents at one observation site. Our results demonstrate that the VF formulation with an appropriate parameterization of wave breaking effects is able to produce reasonable results for applications over coastal waters during extreme weather events. The RS formulation requires a complex wave theory rather than the linear wave theory for the approximation of a vertical RS term to improve its performance under both breaking and non-breaking wave conditions.

Experimental Study of the Effect of Water Mist Location On Blast Overpressure Attenuation in A Shock Tube

NASA Astrophysics Data System (ADS)

Mataradze, Edgar; Chikhradze, Nikoloz; Bochorishvili, Nika; Akhvlediani, Irakli; Tatishvili, Dimitri

2017-12-01

Explosion protection technologies are based on the formation of a shock wave mitigation barrier between the protection site and the explosion site. Contemporary protective systems use water mist as an extinguishing barrier. To achieve high effectiveness of the protective system, proper selection of water mist characteristics is important. The main factors defining shock wave attenuation in water mist include droplet size distribution, water concentration in the mist, droplet velocity and geometric properties of mist. This paper examines the process of attenuation of shock waves in mist with droplets ranging from 25 to 400 microns under different conditions of water mist location. Experiments were conducted at the Mining Institute with the use of a shock tube to study the processes of explosion suppression by a water mist barrier. The shock tube consists of a blast chamber, a tube, a system for the dosed supply of water, sensors, data recording equipment, and a process control module. Shock wave overpressure reduction coefficient was studied in the shock tube under two different locations of water mist: a) when water mist is created in direct contact with blast chamber and b) the blast chamber and the mist are separated by air space. It is established that in conditions when the air space distance between the blast chamber and the mist is 1 meter, overpressure reduction coefficient is 1.5-1.6 times higher than in conditions when water mist is created in direct contact with blast chamber.

Co-seismic response of water level in the Jingle well (China) associated with the Gorkha Nepal (Mw 7.8) earthquake

NASA Astrophysics Data System (ADS)

He, Anhua; Fan, Xuefang; Zhao, Gang; Liu, Yang; Singh, Ramesh P.; Hu, Yuliang

2017-09-01

Changes in co-seismic water levels associated with the Gorkha Nepal earthquake (25 April 2015, Mw 7.8) were recorded in the Jingle well in Shanxi Province China (longitude E112.03°, latitude N38.35°, about 2769 km from epicenter). Based on the observed water levels, we clearly identified signals relating to P, S and surface waves. However, the water temperature recorded at a depth of 350 m shows no co-seismic changes. A spectrum analysis of co-seismic variations of water level shows that the oscillation frequency and amplitude of water level in the borehole are determined by the natural frequency of the borehole, which is not associated with the propagation of seismic waves. The borehole-aquifer system shows a large amplification associated with ground vibrations generated by earthquakes. Considering the local hydro-geological map and the temperature gradient of the Jingle well, a large volume ;groundwater reservoir; model can be used to explain these processes. Due to seismic wave propagation, the volume of a well-confined aquifer expands and contracts forming fractures that change the water flow. In the well-confined aquifer, water levels oscillate simultaneously with high amplitude ground shaking during earthquakes. However, the water in the center of the ;underground reservoir; remains relatively stationary, without any changes in the water temperature. In addition, a possible precursor wave is recorded in the water level at the Jingle well prior to the Gorkha earthquake.

[Study on Trace Water Influence on Electrical Properties of Insulating Oil Based on the Mid-Infrared Spectrum Analysis].

PubMed

Chen, Bin; Wu, Hong-yang; Han, Chao; Yan, Huan; Liu, Ge

2015-10-01

Trace water has a significant impact on the electrical performances of the insulating oil, such as the dielectric loss factor, resistivity. So there is an important significance to investigate the influence of insulating oil by trace water, and monitor its operating status with effective measures. First, it is necessary to prepare the insulating oil samples with different water content and treat them 8 hours with ultrasonic oscillator, and observe microscopic images about the water-oil mixtures in order to study their relative uniformity and stable time, in the way it can be concluded that the relative uniformity can be kept favorable during the 25 min stable time for free water and emulsification water in oil; Based on this conclusion, the dielectric loss factor, resistivity were tested and the electrical performances of insulating oil with different water content in oil can obtained by analyzing these data; Then, the absorbance value of the different water content in oil at the spectral wave number of 1 640, 3 400, 3 450, 3 615 cm(-1), with the mid-infrared spectral scanning and analyzing to the different water content in oil, Therefore, combined the water absorbance values by the mid-infrared spectral scanning and analyzing with the experimental data of dielectric loss factor value, resistivity value of oil samples. The results shows that the absorbance value of the different water content in oil has a significant difference at the spectral wave number of 1 640, 3 400, 3450, 3 615 cm(-1), their correlation coefficient are 0.964 1, 0.984 8, 0.984 5, 0.944 0 between the absorbance value and water content at the spectral wave number of 1 640, 3 400, 3 450, 3 615 cm(-1), it can be obtained that the absorbance value of sample of moisture in the corresponding characteristic wave number can better reflect the change trend of water content; there is the highly relative of water absorbance values at the spectral wave number of 3 400 and 3 450 cm(-1) with the trends of oil dielectric loss factor values, their correlation coefficient are 0.860 6, 0.863 6; and relative of water absorbance values at the spectral wave number of 1 640 and 3 615 cm(-1) with the trends of oil resistivity values, their correlation coefficient is -0.931 5 and -0.968 0, this result can be lay the foundation research for monitoring the trace water in oil.

High temperature measurement of water vapor absorption

NASA Technical Reports Server (NTRS)

Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

1985-01-01

An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

Comparison of actinide production in traveling wave and pressurized water reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osborne, A.G.; Smith, T.A.; Deinert, M.R.

The geopolitical problems associated with civilian nuclear energy production arise in part from the accumulation of transuranics in spent nuclear fuel. A traveling wave reactor is a type of breed-burn reactor that could, if feasible, reduce the overall production of transuranics. In one possible configuration, a cylinder of natural or depleted uranium would be subjected to a fast neutron flux at one end. The neutrons would transmute the uranium, producing plutonium and higher actinides. Under the right conditions, the reactor could become critical, at which point a self-stabilizing fission wave would form and propagate down the length of the reactormore » cylinder. The neutrons from the fission wave would burn the fissile nuclides and transmute uranium ahead of the wave to produce additional fuel. Fission waves in uranium are driven largely by the production and fission of {sup 239}Pu. Simulations have shown that the fuel burnup can reach values greater than 400 MWd/kgIHM, before fission products poison the reaction. In this work we compare the production of plutonium and minor actinides produced in a fission wave to that of a UOX fueled light water reactor, both on an energy normalized basis. The nuclide concentrations in the spent traveling wave reactor fuel are computed using a one-group diffusion model and are verified using Monte Carlo simulations. In the case of the pressurized water reactor, a multi-group collision probability model is used to generate the nuclide quantities. We find that the traveling wave reactor produces about 0.187 g/MWd/kgIHM of transuranics compared to 0.413 g/MWd/kgIHM for a pressurized water reactor running fuel enriched to 4.95 % and burned to 50 MWd/kgIHM. (authors)« less

The Effects of Wind and Surfactants on Mechanically Generated Spilling Breakers

NASA Astrophysics Data System (ADS)

Liu, X.; Diorio, J. D.; Duncan, J. H.

2007-11-01

The effects of both wind and surfactants on mechanically generated weakly spilling breakers are explored in a wind wave tank that is 11.8 m long, 1.15 m wide and 1.8 m high (1.0 m of water). A wave maker, which resides at the upwind end of the tank, is used to generate the breakers via a dispersive focusing method with a central wave packet frequency of 1.15 Hz. Low wind speeds (less than 3.0 m/s) are used to minimize the effect of short-wavelength wind-generated waves on the breakers. The profiles of the spilling breakers along the center plane of the tank are measured with an LIF technique that utilizes a high-speed digital movie camera. Measurements are performed with clean water and water mixed with various concentrations of Triton X-100, a soluble surfactant. It is found that the capillary waves/bulge patterns found in the initial stages of spilling breakers are dramatically affected by wind and surfactants. The size of bulge increases with the wind speed while the capillary waves are kept nearly the same. In the presence of surfactants and wind, both the amplitude and number of capillary waves are reduced and the slope of the front face of the wave increases.

Effects of waves on water dispersion in a semi-enclosed estuarine bay

NASA Astrophysics Data System (ADS)

Delpey, M. T.; Ardhuin, F.; Otheguy, P.

2012-04-01

The bay of Saint Jean de Luz - Ciboure is a touristic destination located in the south west of France on the Basque coast. This small bay is 1.5km wide for 1km long. It is semi-enclosed by breakwaters, so that the area is mostly protected from waves except in its eastern part, where wave breaking is regularly observed over a shallow rock shelf. In the rest of the area the currents are generally weak. The bay receives fresh water inflows from two rivers. During intense raining events, the rivers can introduce pollutants in the bay. The input of pollutants combined with the low level dynamic of the area can affect the water quality for several days. To study such a phenomenon, mechanisms of water dispersion in the bay are investigated. The present paper focuses on the effects of waves on bay dynamics. Several field experiments were conducted in the area, combining wave and current measurements from a set of ADCP and ADV, lagrangian difter experiments in the surfzone, salinity and temperature profile measurements. An analysis of this set of various data is provided. It reveals that the bay combines remarkable density stratification due to fresh water inflows and occasionally intense wave-induced currents in the surfzone. These currents have a strong influence on river plume dynamics when the sea state is energetic. Moreover, modifications of hydrodynamics in the bay passes are found to be remarkably correlated with sea state evolutions. This result suggests a significant impact of waves on the bay flushing. To further analyse these phenomena, a three dimensional numerical model of bay hydrodynamics is developed. The model aims at reproducing fresh water inflows combined with wind-, tide- and wave-induced currents and mixing. The model of the bay is implemented using the code MOHID , which has been modified to allow the three dimensional representation of wave-current interactions proposed by Ardhuin et al. [2008b] . The circulation is forced by the wave field modelled with the code WAVEWATCHIII . A first confrontation between model results and in situ observations is provided, showing a reasonable agreement. ----------------------------------------------------------- 1 Braunschweig, F., Chamble, P., Fernandes, L., Pina, P., Neves, R., The object-oriented design of the integrated modelling system MOHID, Computational Methods in Water Resources International Conference (North Carolina, USA: Chapel Hill). 2 Ardhuin, F., Rascle, N., Belibassakis, K. A., 2008b. Explicit wave-averaged primitive equations using a generalized Lagrangian mean. Ocean Modelling 20, 35-60. 3 Tolman, H. L., 2009. User manual and system documentation of WAVEWATCHIIITM version3.14. Tech. Rep. 276, NOAA/NWS/NCEP/MMAB.

The effect of heat waves, elevated [CO2 ] and low soil water availability on northern red oak (Quercus rubra L.) seedlings.

PubMed

Bauweraerts, Ingvar; Wertin, Timothy M; Ameye, Maarten; McGuire, Mary Anne; Teskey, Robert O; Steppe, Kathy

2013-02-01

The frequency and intensity of heat waves are predicted to increase. This study investigates whether heat waves would have the same impact as a constant increase in temperature with the same heat sum, and whether there would be any interactive effects of elevated [CO2 ] and soil moisture content. We grew Quercus rubra seedlings in treatment chambers maintained at either ambient or elevated [CO2 ] (380 or 700 μmol CO2 mol(-1) ) with temperature treatments of ambient, ambient +3 °C, moderate heat wave (+6 °C every other week) or severe heat wave (+12 °C every fourth week) temperatures. Averaged over a 4-week period, and the entire growing season, the three elevated temperature treatments had the same average temperature and heat sum. Half the seedlings were watered to a soil water content near field capacity, half to about 50% of this value. Foliar gas exchange measurements were performed morning and afternoon (9:00 and 15:00 hours) before, during and after an applied heat wave in August 2010. Biomass accumulation was measured after five heat wave cycles. Under ambient [CO2 ] and well-watered conditions, biomass accumulation was highest in the +3 °C treatment, intermediate in the +6 °C heat wave and lowest in the +12 °C heat wave treatment. This response was mitigated by elevated [CO2 ]. Low soil moisture significantly decreased net photosynthesis (Anet ) and biomass in all [CO2 ] and temperature treatments. The +12 °C heat wave reduced afternoon Anet by 23% in ambient [CO2 ]. Although this reduction was relatively greater under elevated [CO2 ], Anet values during this heat wave were still 34% higher than under ambient [CO2 ]. We concluded that heat waves affected biomass growth differently than the same amount of heat applied uniformly over the growing season, and that the plant response to heat waves also depends on [CO2 ] and soil moisture conditions. © 2012 Blackwell Publishing Ltd.

Acoustic Wave Propagation in Snow Based on a Biot-Type Porous Model

NASA Astrophysics Data System (ADS)

Sidler, R.

2014-12-01

Despite the fact that acoustic methods are inexpensive, robust and simple, the application of seismic waves to snow has been sparse. This might be due to the strong attenuation inherent to snow that prevents large scale seismic applications or due to the somewhat counterintuitive acoustic behavior of snow as a porous material. Such materials support a second kind of compressional wave that can be measured in fresh snow and which has a decreasing wave velocity with increasing density of snow. To investigate wave propagation in snow we construct a Biot-type porous model of snow as a function of porosity based on the assumptions that the solid frame is build of ice, the pore space is filled with a mix of air, or air and water, and empirical relationships for the tortuosity, the permeability, the bulk, and the shear modulus.We use this reduced model to investigate compressional and shear wave velocities of snow as a function of porosity and to asses the consequences of liquid water in the snowpack on acoustic wave propagation by solving Biot's differential equations with plain wave solutions. We find that the fast compressional wave velocity increases significantly with increasing density, but also that the fast compressional wave velocity might be even lower than the slow compressional wave velocity for very light snow. By using compressional and shear strength criteria and solving Biot's differential equations with a pseudo-spectral approach we evaluate snow failure due to acoustic waves in a heterogeneous snowpack, which we think is an important mechanism in triggering avalanches by explosives as well as by skiers. Finally, we developed a low cost seismic acquisition device to assess the theoretically obtained wave velocities in the field and to explore the possibility of an inexpensive tool to remotely gather snow water equivalent.

Variability in benthic exchange rate, depth, and residence time beneath a shallow coastal estuary

NASA Astrophysics Data System (ADS)

Russoniello, C. J.; Michael, H. A.; Heiss, J.

2017-12-01

Hydrodynamically-driven exchange of water between the water column and shallow seabed aquifer, benthic exchange, is a significant and dynamic component of coastal and estuarine fluid budgets, but wave-induced benthic exchange has not been measured in the field. Mixing between surface water and groundwater solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times, constrains estimates of coastal chemical cycling. In this study, we present the first field-based direct measurements of wave-induced exchange and compare it to exchange induced by the other primary drivers of exchange - tides, and currents. We deployed instruments in a shallow estuary to measure benthic exchange and temporal variability over an 11-day period. Differential pressure sensors recorded pressure gradients across the seabed, and up-and down-looking ADCPs recorded currents and pressures from which wave parameters, surface-water currents, and water depth were determined. Wave-induced exchange was calculated directly from 1) differential pressure measurements, and indirectly with an analytical solution based on wave parameters from 2) ADCP and 3) weather station data. Groundwater flow models were used to assess the effects of aquifer properties on benthic exchange depth and residence time. Benthic exchange driven by tidal pumping or current-bedform interaction was calculated from tidal stage variation and from ADCP-measured currents at the bed, respectively. Waves were the primary benthic exchange driver (average = 20.0 cm/d, maximum = 92.3 cm/d) during the measurement period. Benthic exchange due to tides (average = 3.7 cm/d) and current-bedform interaction (average = 6.5x10-2 cm/d) was much lower. Wave-induced exchange calculated from pressure measurements and ADCP-measured wave parameters matched well, but wind-based rates underestimated wave energy and exchange. Groundwater models showed that residence time and depth increased in high-permeability, incompressible aquifers, and exchange rates increased in low-permeability, compressible aquifers. These findings support and extend the utility of existing wave-induced exchange solutions and will help managers assess the importance of benthic exchange on coastal chemical cycling.

A semi-analytical method for near-trapped mode and fictitious frequencies of multiple scattering by an array of elliptical cylinders in water waves

NASA Astrophysics Data System (ADS)

Chen, Jeng-Tzong; Lee, Jia-Wei

2013-09-01

In this paper, we focus on the water wave scattering by an array of four elliptical cylinders. The null-field boundary integral equation method (BIEM) is used in conjunction with degenerate kernels and eigenfunctions expansion. The closed-form fundamental solution is expressed in terms of the degenerate kernel containing the Mathieu and the modified Mathieu functions in the elliptical coordinates. Boundary densities are represented by using the eigenfunction expansion. To avoid using the addition theorem to translate the Mathieu functions, the present approach can solve the water wave problem containing multiple elliptical cylinders in a semi-analytical manner by introducing the adaptive observer system. Regarding water wave problems, the phenomena of numerical instability of fictitious frequencies may appear when the BIEM/boundary element method (BEM) is used. Besides, the near-trapped mode for an array of four identical elliptical cylinders is observed in a special layout. Both physical (near-trapped mode) and mathematical (fictitious frequency) resonances simultaneously appear in the present paper for a water wave problem by an array of four identical elliptical cylinders. Two regularization techniques, the combined Helmholtz interior integral equation formulation (CHIEF) method and the Burton and Miller approach, are adopted to alleviate the numerical resonance due to fictitious frequency.

Surface waves generated by shallow underwater explosions

NASA Technical Reports Server (NTRS)

Falade, A.; Holt, M.

1978-01-01

Surface water waves generated by surface and near surface point explosions are calculated. Taking the impulse distribution imparted at the water surface by the explosion as the overriding mechanism for transferring energy of the explosive to surface wave motion, the linearized theory of Kranzer and Keller is used to obtain the wave displacement in the far field. The impulse distribution is obtained by integrating the pressure wave over an appropriate time interval on a horizontal surface just beneath the undisturbed water surface. For surface explosions, a modified form of the similarity method first used by Collins and Holt is used to obtain the flow field. In the case of submerged explosions, the flow field is estimated by making necessary modifications to Sedov's similarity solution to account for the venting that accompanies the interaction of the leading (blast) wave with the ocean surface. Surface waves generated by a charge at six depths of placement (0.15 m, 0.30 m, 0.61 m, 0.91 m, 1.37 m, 3.05 m) are considered in addition to surface explosions. The results seem to support the existence of an upper critical depth phenomenon (of the type already established for chemical explosions) for point (nuclear) explosions.

Distribution of water-group ion cyclotron waves in Saturn's magnetosphere

NASA Astrophysics Data System (ADS)

Chou, Marty; Cheng, Chio Zong

2017-09-01

The water-group ion cyclotron waves (ICWs) in Saturn's magnetosphere were studied using the magnetic field data provided by the MAG magnetometer on board the Cassini satellite. The period from January 2005 to December 2009, when the Cassini radial distance is smaller than 8 R S , was used. ICWs were identified by their left-hand circularly polarized magnetic perturbations and wave frequencies near the water-group ion gyrofrequencies. We obtained the spatial distribution of ICW amplitude and found that the source region of ICWs is mostly located in the low-latitude region, near the equator and inside the 6 R S radial distance. However, it can extend beyond 7 R S in the midnight region. In general, the wave amplitude is peaked slightly away from the equator, for all local time sectors in both the Northern and Southern Hemispheres. By assuming that the water-group ions are composed of pickup ions and background thermal ions, we obtained the local instability condition of the ICWs and estimated their growth rate along the field lines. If the wave amplitude is correlated with the growth rate, the observed latitudinal dependence of the wave amplitude can be well explained by the local stability analysis. Also, latitudinal location of the peak amplitude is found to depend on the local time. This implies a local time dependence for the water-group ion parallel temperature T|, as determined from the theoretical calculations. [Figure not available: see fulltext.

Observation of broadband terahertz wave generation from liquid water

NASA Astrophysics Data System (ADS)

Jin, Qi; E, Yiwen; Williams, Kaia; Dai, Jianming; Zhang, X.-C.

2017-08-01

Bulk liquid water is a strong absorber in the terahertz (THz) frequency range, due to which liquid water has historically been sworn off as a source for THz radiation. Here, we experimentally demonstrate the generation of broadband THz waves from liquid water excited by femtosecond laser pulses. Our measurements reveal the critical dependence of the THz field upon the relative position between the water film and the focal point of the laser beam. The THz radiation from liquid water shows distinct characteristics when compared with the THz radiation from air plasmas with single color optical excitation. First, the THz field is maximized with the laser beam of longer pulse durations. In addition, the p-polarized component of the emitted THz waves will be influenced by the polarization of the optical excitation beam. It is also shown that the energy of the THz radiation is linearly dependent on the excitation pulse energy.

Terahertz Measurement of the Water Content Distribution in Wood Materials

NASA Astrophysics Data System (ADS)

Bensalem, M.; Sommier, A.; Mindeguia, J. C.; Batsale, J. C.; Pradere, C.

2018-02-01

Recently, THz waves have been shown to be an effective technique for investigating the water diffusion within porous media, such as biomaterial or insulation materials. This applicability is due to the sufficient resolution for such applications and the safe levels of radiation. This study aims to achieve contactless absolute water content measurements at a steady state case in semi-transparent solids (wood) using a transmittance THz wave range setup. First, a calibration method is developed to validate an analytical model based on the Beer-Lambert law, linking the absorption coefficient, the density of the solid, and its water content. Then, an estimation of the water content on a local scale in a transient-state case (drying) is performed. This study shows that THz waves are an effective contactless, safe, and low-cost technique for the measurement of water content in a porous medium, such as wood.

Sound radiation from a water-filled pipe, radiation into light fluid.

PubMed

Liu, Bilong; Pan, Jie; Li, Xiaodong; Tian, Jing

2002-12-01

This paper is concerned with the sound radiation from a water-filled exhaust pipe. The pipe opening and a plate attached to it form a vibrating surface for this radiation. Fluid-structural coupling between the pipe and enclosed fluid is included in the system modeling, but light fluid assumption is used for sound radiation into the space above the vibrating surface. In this paper, a numerical study on the n = 0 mode in the pipe shows that the wave types associated with this mode have different characteristics in two regions of the nondimensional frequency omega. In the first region of 0

Nonlinear wave interactions in shallow water magnetohydrodynamics of astrophysical plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klimachkov, D. A., E-mail: klimachkovdmitry@gmail.com; Petrosyan, A. S., E-mail: apetrosy@iki.rssi.ru

2016-05-15

The rotating magnetohydrodynamic flows of a thin layer of astrophysical and space plasmas with a free surface in a vertical external magnetic field are considered in the shallow water approximation. The presence of a vertical external magnetic field changes significantly the dynamics of wave processes in an astrophysical plasma, in contrast to a neutral fluid and a plasma layer in an external toroidal magnetic field. There are three-wave nonlinear interactions in the case under consideration. Using the asymptotic method of multiscale expansions, we have derived nonlinear equations for the interaction of wave packets: three magneto- Poincare waves, three magnetostrophic waves,more » two magneto-Poincare and one magnetostrophic waves, and two magnetostrophic and one magneto-Poincare waves. The existence of decay instabilities and parametric amplification is predicted. We show that a magneto-Poincare wave decays into two magneto-Poincare waves, a magnetostrophic wave decays into two magnetostrophic waves, a magneto-Poincare wave decays into one magneto-Poincare and one magnetostrophic waves, and a magnetostrophic wave decays into one magnetostrophic and one magneto-Poincare waves. There are the following parametric amplification mechanisms: the parametric amplification of magneto-Poincare waves, the parametric amplification of magnetostrophic waves, the amplification of a magneto-Poincare wave in the field of a magnetostrophic wave, and the amplification of a magnetostrophic wave in the field of a magneto-Poincare wave. The instability growth rates and parametric amplification factors have been found for the corresponding processes.« less

Ultrasound shear wave imaging

NASA Astrophysics Data System (ADS)

Ye, Shigong; Wu, Junru

2000-05-01

Shear wave propagation properties including phase velocity and attenuation coefficient are indispensable information in materials characterization and nondestructive evaluation. A computer controlled scanning shear-wave ultrasonic imaging system has been developed. It consists of a pair of focusing broadband pvdf transducers of central frequency of 50 MHz immersed in distilled water. Shear waves in a solid specimen are generated by mode-conversion. When ultrasonic waves generated by one of the pvdf transducers impinge upon a solid specimen from water with angle of incidence of θ that is greater than θcr, the critical angle of the longitudinal wave in the solid, only shear waves can propagate in the solid and longitudinal waves become evanescent waves. The shear waves pass through the specimen and received by the other pvdf transducer. Meanwhile, the specimen was scanned by a stepped motor of a step of 10 μm. The system was used to generated shear waves amplitude and phase velocity images of bone specimen of 1280 μm and they are compared with their longitudinal wave counterparts. The results have shown shear wave images can provide additional shear modulus and shear viscous information that longitudinal waves can't provide. The lateral resolution of 60 μm was achieved using shear wave imaging technique applied in bone sample.

High power water load for microwave and millimeter-wave radio frequency sources

DOEpatents

Ives, R. Lawrence; Mizuhara, Yosuke M.; Schumacher, Richard V.; Pendleton, Rand P.

1999-01-01

A high power water load for microwave and millimeter wave radio frequency sources has a front wall including an input port for the application of RF power, a cylindrical dissipation cavity lined with a dissipating material having a thickness which varies with depth, and a rear wall including a rotating reflector for the reflection of wave energy inside the cylindrical cavity. The dissipation cavity includes a water jacket for removal of heat generated by the absorptive material coating the dissipation cavity, and this absorptive material has a thickness which is greater near the front wall than near the rear wall. Waves entering the cavity reflect from the rotating reflector, impinging and reflecting multiple times on the absorptive coating of the dissipation cavity, dissipating equal amounts of power on each internal reflection.

Measurement of Underwater Operational Noise Emitted by Wave and Tidal Stream Energy Devices.

PubMed

Lepper, Paul A; Robinson, Stephen P

2016-01-01

The increasing international growth in the development of marine and freshwater wave and tidal energy harvesting systems has been followed by a growing requirement to understand any associated underwater impact. Radiated noise generated during operation is dependent on the device's physical properties, the sound-propagation environment, and the device's operational state. Physical properties may include size, distribution in the water column, and mechanics/hydrodynamics. The sound-propagation environment may be influenced by water depth, bathymetry, sediment type, and water column acoustic properties, and operational state may be influenced by tidal cycle and wave height among others This paper discusses some of the challenges for measurement of noise characteristics from these devices as well as a case study of the measurement of radiated noise from a full-scale wave energy converter.

Investigation of Surface Waves in Deep and Shallow Water using Coherent Radars at Grazing Incidence

NASA Astrophysics Data System (ADS)

Buckley, M.; Horstmann, J.; Carrasco, R.; Seemann, J.; Stresser, M.

2016-02-01

Coherent microwave radars operating at X-band near grazing incidence are utilized to measure the backscatter intensity and Doppler velocity from the small-scale surface roughness of the ocean. The radar backscatter is dependent on the wind and strongly modulated by the surface waves and therefore enables to retrieve the surface wind as well as surface waves. The radar measured Doppler velocities are also modulated by contributions from the wind, current and waves and allow getting additional information on these parameters. In addition coherent marine radars allow to observe breaking waves, which lead to a increase in radar backscatter as well as a strong change of the Doppler speed.Within this presentation we will introduce and validate new methods to measure spectral wave properties such as wave directions, periods and significant wave height from coherent marine radars. The methods have been applied in deep and shallow water and validated to measurements of directional wave riders as well as an Acoustic Wave and Current Profiler. These comparisons show an overall excellent performance of coherent radars for the retrieval of spectral wave properties (e.g. Hs rms of 0.2 m). Furthermore, new methodologies will be presented that enable to observe and quantify wave breaking in deep water as well as in the littoral zone. The above mentioned methods have been applied to investigate the influence of Offshore Wind Farms (OWF) on the wave field with respect to the spectral properties as well as the amount of wave breaking. We will present the results obtained during a cruise in May 2015 within and around the OWF Dantysk in the German Bight of the North Sea, which consist of eighty 3.5 MW wind turbines. In addition we will present our initial results on the investigation of wave dissipation in the littoral zone at the coast of the island Sylt using marine radars, pressure gauges as well as directional wave riders.

A depth-averaged 2-D shallow water model for breaking and non-breaking long waves affected by rigid vegetation

USDA-ARS?s Scientific Manuscript database

This paper presents a depth-averaged two-dimensional shallow water model for simulating long waves in vegetated water bodies under breaking and non-breaking conditions. The effects of rigid vegetation are modelled in the form of drag and inertia forces as sink terms in the momentum equations. The dr...

Surfing with capillary waves: a survival strategy for trapped bees

NASA Astrophysics Data System (ADS)

Roh, Chris; Gharib, Morteza

2017-11-01

Honeybees are able to propel themselves at the water surface. A rapid vibration (30-220 Hz) of wings at the air-water interface results in a locomotion speed of 3-4 cm/s. A mechanism for generating thrust required for achieving and maintaining such speed must be different from their mechanism of flight inasmuch as they are in a different fluid environment. In this study, we present the thrust generating mechanism of the honeybee at the air-water interface. A close observation of the wing's interaction with the water surface showed that the wing does not penetrate nor detach from the water surface. Moreover, the stroke speed of the wing exceeds the minimum capillary wave speed, which signifies that the wing constantly generates the capillary wave by pulling on the surface with its wetted underside. Observation of such interaction suggests that honeybee's locomotion at the water surface resembles surfing on the self-generated capillary wave. A further evidence of described mechanism is explored by constructing a similarly sized mechanical model. This material is based upon work supported by the National Science Foundation under Grant No. CBET-1511414; additional support by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469.

Shock-wave propagation and cavitation bubble oscillation by Nd:YAG laser ablation of a metal in water.

PubMed

Chen, Xiao; Xu, Rong-Qing; Chen, Jian-Ping; Shen, Zhong-Hua; Jian, Lu; Ni, Xiao-Wu

2004-06-01

A highly sensitive fiber-optic sensor based on optical beam deflection is applied for investigating the propagation of a laser-induced plasma shock wave, the oscillation of a cavitation bubble diameter, and the development of a bubble-collapse-induced shock wave when a Nd:YAG laser pulse is focused upon an aluminum surface in water. By the sequence of experimental waveforms detected at different distances, the attenuation properties of the plasma shock wave and of the bubble-collapse-induced shock wave are obtained. Besides, based on characteristic signals, both the maximum and the minimum bubble radii at each oscillation cycle are determined, as are the corresponding oscillating periods.

Numerical studies of the KP line-solitons

NASA Astrophysics Data System (ADS)

Chakravarty, S.; McDowell, T.; Osborne, M.

2017-03-01

The Kadomtsev-Petviashvili (KP) equation admits a class of solitary wave solutions localized along distinct rays in the xy-plane, called the line-solitons, which describe the interaction of shallow water waves on a flat surface. These wave interactions have been observed on long, flat beaches, as well as have been recreated in laboratory experiments. In this paper, the line-solitons are investigated via direct numerical simulations of the KP equation, and the interactions of the evolved solitary wave patterns are studied. The objective is to obtain greater insight into solitary wave interactions in shallow water and to determine the extent the KP equation is a good model in describing these nonlinear interactions.

Role of S waves and Love waves in coseismic permeability enhancement

NASA Astrophysics Data System (ADS)

Wang, Chi-yuen; Chia, Yeeping; Wang, Pei-ling; Dreger, Douglas

2009-05-01

The 2008 M7.9 Wenchuan earthquake in Sichuan, China, caused water level to oscillate and undergo sustained changes in Taiwan, ˜2000 km away from the epicenter. Here we use the responses in three wells recorded at high sampling rate (1 Hz) and the broadband seismograms from a nearby station to document, for the first time, that the major water-level responses associated with Rayleigh waves were preceded by small oscillations that occurred concurrently with S waves and Love waves. We also show that the groundwater flow associated with these small oscillations may be strong enough to remove blockades from sediment pores to enhance aquifer permeability and to facilitate the later major responses.

The influence of surface waves on water circulation in a mid-Atlantic continental shelf region

NASA Technical Reports Server (NTRS)

Whitlock, C. H.; Talay, T. A.

1974-01-01

The importance of wave-induced currents in different weather conditions and water depths (18.3 m and 36.6 m) is assessed in a mid-Atlantic continental-shelf region. A review of general circulation conditions is conducted. Factors which perturb the general circulation are examined using analytic techniques and limited experimental data. Actual wind and wave statistics for the region are examined. Relative magnitudes of the various currents are compared on a frequency of annual occurrence basis. Results indicated that wave-induced currents are often the same order of magnitude as other currents in the region and become more important at higher wind and wave conditions. Wind-wave and ocean-swell characteristics are among those parameters which must be monitored for the analytical computation of continental-shelf circulation.

Phase Domain Walls in Weakly Nonlinear Deep Water Surface Gravity Waves.

PubMed

Tsitoura, F; Gietz, U; Chabchoub, A; Hoffmann, N

2018-06-01

We report a theoretical derivation, an experimental observation and a numerical validation of nonlinear phase domain walls in weakly nonlinear deep water surface gravity waves. The domain walls presented are connecting homogeneous zones of weakly nonlinear plane Stokes waves of identical amplitude and wave vector but differences in phase. By exploiting symmetry transformations within the framework of the nonlinear Schrödinger equation we demonstrate the existence of exact analytical solutions representing such domain walls in the weakly nonlinear limit. The walls are in general oblique to the direction of the wave vector and stationary in moving reference frames. Experimental and numerical studies confirm and visualize the findings. Our present results demonstrate that nonlinear domain walls do exist in the weakly nonlinear regime of general systems exhibiting dispersive waves.

Phase Domain Walls in Weakly Nonlinear Deep Water Surface Gravity Waves

NASA Astrophysics Data System (ADS)

Tsitoura, F.; Gietz, U.; Chabchoub, A.; Hoffmann, N.

2018-06-01

We report a theoretical derivation, an experimental observation and a numerical validation of nonlinear phase domain walls in weakly nonlinear deep water surface gravity waves. The domain walls presented are connecting homogeneous zones of weakly nonlinear plane Stokes waves of identical amplitude and wave vector but differences in phase. By exploiting symmetry transformations within the framework of the nonlinear Schrödinger equation we demonstrate the existence of exact analytical solutions representing such domain walls in the weakly nonlinear limit. The walls are in general oblique to the direction of the wave vector and stationary in moving reference frames. Experimental and numerical studies confirm and visualize the findings. Our present results demonstrate that nonlinear domain walls do exist in the weakly nonlinear regime of general systems exhibiting dispersive waves.

Effect of winds and waves on salt intrusion in the Pearl River estuary

NASA Astrophysics Data System (ADS)

Gong, Wenping; Lin, Zhongyuan; Chen, Yunzhen; Chen, Zhaoyun; Zhang, Heng

2018-02-01

Salt intrusion in the Pearl River estuary (PRE) is a dynamic process that is influenced by a range of factors and to date, few studies have examined the effects of winds and waves on salt intrusion in the PRE. We investigate these effects using the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system applied to the PRE. After careful validation, the model is used for a series of diagnostic simulations. It is revealed that the local wind considerably strengthens the salt intrusion by lowering the water level in the eastern part of the estuary and increasing the bottom landward flow. The remote wind increases the water mixing on the continental shelf, elevates the water level on the shelf and in the PRE and pumps saltier shelf water into the estuary by Ekman transport. Enhancement of the salt intrusion is comparable between the remote and local winds. Waves decrease the salt intrusion by increasing the water mixing. Sensitivity analysis shows that the axial down-estuary wind, is most efficient in driving increases in salt intrusion via wind straining effect.

Dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event

NASA Astrophysics Data System (ADS)

Malott, Spencer; O'Carroll, Denis M.; Robinson, Clare E.

2016-07-01

Dynamic coastal forcing influences the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters. In this study, field data are presented that show, for the first time, the influence of a period of intensified wave conditions (wave event) on nearshore groundwater flows and geochemistry in a sandy beach. Field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines (e.g., tides). Pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations. The groundwater flows were simulated in FEFLOW using a phase-averaged wave setup approach to represent waves acting on the sediment-water interface. Comparison of measured and simulated data indicates that consideration of wave setup alone is able to adequately capture wave-induced perturbations in groundwater flows. While prior studies have shown sharp pH and redox spatial zonations in nearshore aquifers, this study reveals rapid temporal variations in conductivity, pH, and redox (ORP) in shallow sediments (up to 0.5 m depth) in response to varying wave conditions. Comparison of head gradients with calculated conductivity and pH mixing ratios indicates the controlling effect of the wave-induced water exchange and flows in driving the observed geochemical dynamics. While we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes, the pH and ORP variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers.

Observation of interaction of shock wave with gas bubble by image converter camera

NASA Astrophysics Data System (ADS)

Yoshii, M.; Tada, M.; Tsuji, T.; Isuzugawa, Kohji

1995-05-01

When a spark discharge occurs at the first focal point of a semiellipsoid or a reflector located in water, a spherical shock wave is produced. A part of the wave spreads without reflecting on the reflector and is called direct wave in this paper. Another part reflects on the semiellipsoid and converges near the second focal point, that is named the focusing wave, and locally produces a high pressure. This phenomenon is applied to disintegrators of kidney stone. But it is concerned that cavitation bubbles induced in the body by the expansion wave following the focusing wave will injure human tissue around kidney stone. In this paper, in order to examine what happens when shock waves strike bubbles on human tissue, the aspect that an air bubble is truck by the spherical shock wave or its behavior is visualized by the schlieren system and its photographs are taken using an image converter camera. Besides,the variation of the pressure amplitude caused by the shock wave and the flow of water around the bubble is measured with a pressure probe.

Bound on the Slope of Steady Water Waves with Favorable Vorticity

NASA Astrophysics Data System (ADS)

Strauss, Walter A.; Wheeler, Miles H.

2016-12-01

We consider the angle {θ} of inclination (with respect to the horizontal) of the profile of a steady two dimensional inviscid symmetric periodic or solitary water wave subject to gravity. Although {θ} may surpass 30° for some irrotational waves close to the extreme wave, Amick (Arch Ration Mech Anal 99(2):91-114, 1987) proved that for any irrotational wave the angle must be less than 31.15°. Is the situation similar for periodic or solitary waves that are not irrotational? The extreme Gerstner wave has infinite depth, adverse vorticity and vertical cusps ( θ = 90°). Moreover, numerical calculations show that even waves of finite depth can overturn if the vorticity is adverse. In this paper, on the other hand, we prove an upper bound of 45° on {θ} for a large class of waves with favorable vorticity and finite depth. In particular, the vorticity can be any constant with the favorable sign. We also prove a series of general inequalities on the pressure within the fluid, including the fact that any overturning wave must have a pressure sink.

The effect of artificial rain on backscattered acoustic signal: first measurements

NASA Astrophysics Data System (ADS)

Titchenko, Yuriy; Karaev, Vladimir; Meshkov, Evgeny; Goldblat, Vladimir

The problem of rain influencing on a characteristics of backscattered ultrasonic and microwave signal by water surface is considered. The rain influence on backscattering process of electromagnetic waves was investigated in laboratory and field experiments, for example [1-3]. Raindrops have a significant impact on backscattering of microwave and influence on wave spectrum measurement accuracy by string wave gauge. This occurs due to presence of raindrops in atmosphere and modification of the water surface. For measurements of water surface characteristics during precipitation we propose to use an acoustic system. This allows us obtaining of the water surface parameters independently on precipitation in atmosphere. The measurements of significant wave height of water surface using underwater acoustical systems are well known [4, 5]. Moreover, the variance of orbital velocity can be measure using these systems. However, these methods cannot be used for measurements of slope variance and the other second statistical moments of water surface that required for analyzing the radar backscatter signal. An original design Doppler underwater acoustic wave gauge allows directly measuring the surface roughness characteristics that affect on electromagnetic waves backscattering of the same wavelength [6]. Acoustic wave gauge is Doppler ultrasonic sonar which is fixed near the bottom on the floating disk. Measurements are carried out at vertically orientation of sonar antennas towards water surface. The first experiments were conducted with the first model of an acoustic wave gauge. The acoustic wave gauge (8 mm wavelength) is equipped with a transceiving antenna with a wide symmetrical antenna pattern. The gauge allows us to measure Doppler spectrum and cross section of backscattered signal. Variance of orbital velocity vertical component can be retrieved from Doppler spectrum with high accuracy. The result of laboratory and field experiments during artificial rain is presented. The estimates of roughness parameters variability during precipitation are obtained. The first measurements of rain influencing on cross section and Doppler spectrum of backscattered acoustic signal was carried out. The obtained results were compared with calculations based on the theoretical model. Acknowledgments. The reported study was supported by RFBR, research project No. 14-05-31517 mol_a. References 1. Bliven Larry, Branger Hubert, Sobieski Piotr, Giovanangeli Jean-Paul, An analysis of scatterometer returns from a water surface agitated by artificial rain : evidence that ring-waves are the mean feature, Intl. Jl. of Remote Sensing, Vol. 14, n 12, 1993, pp. 2315-2329, 1993 2. Sobieski Piotr, Craeye Christophe, Bliven Larry, A Relationship Between Rain Radar Reflectivity and Height Elevation Variance of Ringwaves due to the Impact of Rain on the Sea Surface, Radio Science, AGU, 44, RS3005, 1-20, 2009 3. Weissman, D. E., and M. A. Bourassa, Measurements of the Effect of Rain-induced Sea Surface Roughness on the Satellite Scatterometer Radar Cross Section, IEEE Trans. Geosci. Remote Sens., 46, 2882-2894, 2008 4. B. Brumley, La Jolla, E.Terray, B.String, «System and method for measuring wave directional spectrum and wave height», USA Patent N US 2004/0184350 A1,23 September 2004 5. James H. Churchill, Albert J. Plueddemann, Stephen M. Faluotico, «Extracting Wind Sea and Swell from Directional Wave Spectra derived from a bottom-mounted ADCP», Woods Hole Oceanographic Institution, Technical Report WHOI-2006-13 6. V. Yu. Karaev, M. B. Kanevsky, E. M. Meshkov, Measuring the parameters of sea-surface roughness by underwater acoustic systems: discussion of the device concept, Radiophysics and Quantum Electronics, V. 53, I. 9-10. pp. 569-579, 2011

Numerical simulation of solitary waves on deep water with constant vorticity

NASA Astrophysics Data System (ADS)

Dosaev, A. S.; Shishina, M. I.; Troitskaya, Yu I.

2018-01-01

Characteristics of solitary deep water waves on a flow with constant vorticity are investigated by numerical simulation within the framework of fully nonlinear equations of motion (Euler equations) using the method of surface-tracking conformal coordinates. To ensure that solutions observed are stable, soliton formation as a result of disintegration of an initial pulse-like disturbance is modeled. Evidence is obtained that solitary waves with height above a certain threshold are unstable.

Waves on Seas of Mars and Titan: Wind-Tunnel Experiments on Wind-Wave Generation in Extraterrestrial Atmospheres

NASA Technical Reports Server (NTRS)

Lorenz, R. D.; Kraal, E. R.; Eddlemon, E. E.; Cheney, J.; Greeley, R.

2004-01-01

The generation of waves by winds across Earth's water oceans is a topic of enduring fascination. However, the physics of the problem are rather forbidding and thus the relationships between real-world windspeed and sea state tend to be empirical. Such empirical relations are of limited utility in environments where the physical parameters are different, such as the surfaces of other planets. These environments have only recently come to oceanographers attention, with the discovery of ancient shorelines and lakes on Mars, and the prospects for and recent evidence of lakes and seas of liquid hydrocarbons on Saturn's moon Titan. We are aware of only one other published experimental wind-water tunnel study where the fluid parameters have been varied. This used artificially-generated mm-scale waves at 3.8-7.6 Hz in water, glycerol solutions (higher viscosity) and surfactant solutions (lower surface tension). Lower viscosity solutions had higher wave growth rates: surprisingly, higher surface tension led to more rapid wave growth. The liquid density was not appreciably varied, and 1 bar air was used throughout.We used the MARSWIT (Mars Wind Tunnel) operated by ASU at NASA Ames. A fiberglass tray (5 cm x 120 cm x 75 cm) was installed in the tunnel, with an approx. 1:5 ramp to prevent strong flow separation. The tray was filled to a depth of about 4 cm. Sensors were clamped to the tray itself or held by a steel and aluminium frame just above the water level. A towel was draped on the water surface at the downwind end of the tray to act as a damper to suppress wave reflection. Position-sensitive infrared (IR) reflection sensors (Sharp GP12D02) and ultrasonic rangers (Devantech DF-04) used in mobile robotics were used as water level sensors. The tray was observed with a video camera, whose output could be viewed on a monitor and recorded on VHS tape.

Relationship between wind, waves and radar backscatter

NASA Technical Reports Server (NTRS)

Katsaros, Kristina B.; Ataktuerk, Serhad S.

1991-01-01

The aim of the research was to investigate the relationship between wind, waves, and radar backscatter from water surface. To this end, three field experiments with periods of 2 to 4 weeks were carried out during summer months in 1988, 1989 and 1990. For these periods, the University of Washington group provided (1) environmental parameters such as wind speed, wind stress, and atmospheric stratification through measurements of surface fluxes (of momentum, sensible heat and latent heat) and of air and water temperatures; and (2) wave height spectra including both the dominant waves and the short gravity-capillary waves. Surface flux measurements were performed by using our well tested instruments: a K-Gill twin propeller-vane anemometer and a fast response thermocouple psychrometer. Wave heights were measured by a resistance wire wave gauge. The University of Kansas group was responsible for the operation of the microwave radars.

Extreme Sea Conditions in Shallow Water: Estimation based on in-situ measurements

NASA Astrophysics Data System (ADS)

Le Crom, Izan; Saulnier, Jean-Baptiste

2013-04-01

The design of marine renewable energy devices and components is based, among others, on the assessment of the environmental extreme conditions (winds, currents, waves, and water level) that must be combined together in order to evaluate the maximal loads on a floating/fixed structure, and on the anchoring system over a determined return period. Measuring devices are generally deployed at sea over relatively short durations (a few months to a few years), typically when describing water free surface elevation, and extrapolation methods based on hindcast data (and therefore on wave simulation models) have to be used. How to combine, in a realistic way, the action of the different loads (winds and waves for instance) and which correlation of return periods should be used are highly topical issues. However, the assessment of the extreme condition itself remains a not-fully-solved, crucial, and sensitive task. Above all in shallow water, extreme wave height, Hmax, is the most significant contribution in the dimensioning process of EMR devices. As a case study, existing methodologies for deep water have been applied to SEMREV, the French marine energy test site. The interest of this study, especially at this location, goes beyond the simple application to SEMREV's WEC and floating wind turbines deployment as it could also be extended to the Banc de Guérande offshore wind farm that are planned close by. More generally to pipes and communication cables as it is a redundant problematic. The paper will first present the existing measurements (wave and wind on site), the prediction chain that has been developed via wave models, the extrapolation methods applied to hindcast data, and will try to formulate recommendations for improving this assessment in shallow water.

Aquatic burst locomotion by hydroplaning and paddling in common eiders (Somateria mollissima).

PubMed

Gough, William T; Farina, Stacy C; Fish, Frank E

2015-06-01

Common eiders (Somateria mollissima) are heavy sea-ducks that spend a large portion of their time swimming at the water surface. Surface swimming generates a bow and hull wave that can constructively interfere and produce wave drag. The speed at which the wavelengths of these waves equal the waterline length of the swimming animal is the hull speed. To increase surface swimming speed beyond the hull speed, an animal must overtake the bow wave. This study found two distinct behaviors that eider ducks used to exceed the hull speed: (1) 'steaming', which involved rapid oaring with the wings to propel the duck along the surface of the water, and (2) 'paddle-assisted flying', during which the ducks lifted their bodies out of the water and used their feet to paddle against the surface while flapping their wings in the air. An average hull speed (0.732±0.046 m s(-1)) was calculated for S. mollissima by measuring maximum waterline length from museum specimens. On average, steaming ducks swam 5.5 times faster and paddle-assisted flying ducks moved 6.8 times faster than the hull speed. During steaming, ducks exceeded the hull speed by increasing their body angle and generating dynamic lift to overcome wave drag and hydroplane along the water surface. During paddle-assisted flying, ducks kept their bodies out of the water, thereby avoiding the limitations of wave drag altogether. Both behaviors provided alternatives to flight for these ducks by allowing them to exceed the hull speed while staying at or near the water surface. © 2015. Published by The Company of Biologists Ltd.

Wave Tank Studies of Strong Modulation of Wind Ripples Due To Long Waves

NASA Astrophysics Data System (ADS)

Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

Modulation of wind capillary-gravity ripples due to long waves has been studied in wave tank experiment at low wind speeds using Ka-band radar. The experiments were carried out both for clean water and the water surface covered with surfactant films. It is obtained that the modulation of radar signals is quite strong and can increase with surfactant concentration and fetch. It is shown that the hydrodynamic Modulation Transfer Function (MTF) calculated for free wind ripples and taking into account the kinematic (straining) effect, variations of the wind stress and variations of surfactant concentration strongly underestimates experimental MTF-values. The effect of strong modulation is assumed to be connected with nonlinear harmonics of longer dm-cm- scale waves - bound waves ("parasitic ripples"). The intensity of bound waves depends strongly on the amplitude of decimetre-scale waves, therefore even weak modulation of the dm-scale waves due to long waves results to strong ("cascade") modulation of bound waves. Modulation of the system of "free/bound waves" is estimated using results of wave tank studies of bound waves generation and is shown to be in quali- tative agreement with experiment. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

Stability Design and Response to Waves by Batoids.

PubMed

Fish, Frank E; Hoffman, Jessica L

2015-10-01

Unsteady flows in the marine environment can affect the stability and locomotor costs of animals. For fish swimming at shallow depths, waves represent a form of unsteady flow. Waves consist of cyclic oscillations, during which the water moves in circular or elliptical orbits. Large gravity waves have the potential to displace fish both cyclically and in the direction of wave celerity for animals floating in the water column or holding station on the bottom. Displacement of a fish can exceed its stability control capability when the size of the wave orbit is equivalent to the size of the fish. Previous research into compensatory behaviors of fishes to waves has focused on pelagic osteichthyan fishes with laterally compressed bodies. However, dorsoventrally compressed batoid rays must also contend with waves. Examination of rays subjected to waves showed differing strategies for stability between pelagic and demersal species. Pelagic cownose rays (Rhinoptera bonasus) would glide through or be transported by waves, maintaining a positive dihedral of the wing-like pectoral fins. Demersal Atlantic stingrays (Dasyatis sabina) and freshwater rays (Potamotrygon motoro) maintained contact with the bottom and performed compensatory fin motions and body postures. The ability to limit displacement due to wave action by the demersal rays was also a function of the bottom texture. The ability of rays to maintain stability due to wave action suggests mechanisms to compensate for the velocity flux of the water impinging on the large projected area of the enlarged pectoral fins of rays. © The Author 2015. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Experimental Observation of Dark Solitons on Water Surface

DTIC Science & Technology

2016-06-13

Experimental observation of dark solitons on water surface A. Chabchoub1,∗, O. Kimmoun2, H. Branger3, N. Hoffmann1, D. Proment4, M. Onorato4,5, and N...The shape and width of the soliton depend on the water depth, carrier frequency and the amplitude of the background wave. The experimental data...partic- ular, the governing equation describing the dynamics of weakly nonlinear and quasi -monochromatic waves prop- agating on the surface of water with

Spatio-temporal variability of internal waves in the northern Gulf of Mexico studied with the Navy Coastal Ocean Model, NCOM

NASA Astrophysics Data System (ADS)

Cambazoglu, M. K.; Jacobs, G. A.; Howden, S. D.; Book, J. W.; Arnone, R.; Soto Ramos, I. M.; Vandermeulen, R. A.; Greer, A. T.; Miles, T. N.

2016-02-01

Internal waves enhance mixing in the upper ocean, transport nutrients and plankton over the water column and across the shelf from deeper waters to shallower coastal areas, and could also transport pollutants such as hydrocarbons onshore during an oil spill event. This study aims to characterize internal waves in the northern Gulf of Mexico (nGoM) and investigate the possible generation and dissipation mechanisms using a high-resolution (1-km) application of the Navy Coastal Ocean Model (NCOM). Three dimensional model products are used to detect the propagation patterns of internal waves. The vertical structure of internal waves is studied and the role of stratification is analyzed by looking at the temperature, salinity and velocity variations along the water column. The model predictions suggest the generation of internal waves on the continental shelf, therefore the role of ocean bottom topography interacting with tides and general circulation features such as the Loop Current Eddy front, on the internal wave generation will be discussed. The time periods of internal wave occurrences are identified from model predictions and compared to satellite ocean color imagery. Further data analysis, e.g. Fourier analysis, is implemented to determine internal wavelengths and frequencies and to determine if the response of internal waves are at tidal periods or at different frequencies. The atmospheric forcing provided to NCOM and meteorological data records are analyzed to define the interaction between wind forcing and internal wave generation. Wavelet analysis characterizes the ocean response to atmospheric events with periodic frequencies. Ocean color satellite imagery was used to visualize the location of the Mississippi river plume (and other oceanic features) and compared to the model predictions because the enhanced stratification from freshwater plumes which propagate across the Mississippi Bight can provide favorable conditions in coastal waters for internal wave generation and propagation. The findings of this study will provide insight about the internal wave dynamics in the Gulf of Mexico and their potential impact on the marine ecosystem.

14 CFR 29.563 - Structural ditching provisions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 27.563 - Structural ditching provisions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 27.563 - Structural ditching provisions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 27.563 - Structural ditching provisions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 27.563 - Structural ditching provisions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 29.563 - Structural ditching provisions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 29.563 - Structural ditching provisions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 29.563 - Structural ditching provisions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 29.563 - Structural ditching provisions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

14 CFR 27.563 - Structural ditching provisions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... speed landing conditions. The rotorcraft must initially contact the most critical wave for reasonably... the mean water surface. Rotor lift may be used to act through the center of gravity throughout the..., unsymmetrical rotorcraft loading, water wave action, rotorcraft inertia, and probable structural damage and...

Multiband coherent perfect absorption in a water-based metasurface.

PubMed

Zhu, Weiren; Rukhlenko, Ivan D; Xiao, Fajun; He, Chong; Geng, Junping; Liang, Xianling; Premaratne, Malin; Jin, Ronghong

2017-07-10

We design an ultrathin water-based metasurface capable of coherent perfect absorption (CPA) at radio frequencies. It is demonstrated that such a metasurface can almost completely absorb two symmetrically incident waves within four frequency bands, each having its own modulation depth of metasurface absorptivity. Specifically, the absorptivity at 557.2 MHz can be changed between 0.59% and 99.99% via the adjustment of the phase difference between the waves. The high angular tolerance of our metasurface is shown to enable strong CPA at oblique incidence, with the CPA frequency almost independent of the incident angle for TE waves and varying from 557.2 up to 584.2 MHz for TM waves. One can also reduce this frequency from 712.0 to 493.3 MHz while retaining strong coherent absorption by varying the water layer thickness. It is also show that the coherent absorption performance can be flexibly controlled by adjusting the temperature of water. The proposed metasurface is low-cost, biocompatible, and useful for electromagnetic modulation and switching.

The quality of our drinking water: aluminium determination with an acoustic wave sensor.

PubMed

Veríssimo, Marta I S; Gomes, M Teresa S R

2008-06-09

A new methodology based on an inexpensive aluminium acoustic wave sensor is presented. Although the aluminium sensor has already been reported, and the composition of the selective membrane is known, the low detection limits required for the analysis of drinking water, demanded the inclusion of a preconcentration stage, as well as an optimization of the sensor. The necessary coating amount was established, as well as the best preconcentration protocol, in terms of oxidation of organic matter and aluminium elution from the Chelex-100. The methodology developed with the acoustic wave sensor allowed aluminium quantitation above 0.07 mg L(-1). Several water samples from Portugal were analysed using the acoustic wave sensor, as well as by UV-vis spectrophotometry. Results obtained with both methodologies were not statistically different (alpha=0.05), both in terms of accuracy and precision. This new methodology proved to be adequate for aluminium quantitation in drinking water and showed to be faster and less reagent consuming than the UV spectrophotometric methodology.

The seismic response of an aquifer to the propagation of an impact generated shock wave: A possible trigger of the Martian outflow channels?

NASA Technical Reports Server (NTRS)

Leyva, Ivett A.; Clifford, Stephen M.

1993-01-01

Aquifer dilation from shock waves produced by the 8.4 magnitude Alaskan earthquake of 1964 led to water and sediment ejection from the ground up to 400 km away from the earthquake's epicenter. Groundwater disturbances were observed as far away as Perry, Florida (approximately 5500 km), where well water fluctuations with an amplitude of as much as 2.3 m were reported. The martian cratering record provides evidence that the planet has experienced numerous seismic events of a similar, and often much greater, magnitude. Given this fact, and the photogeologic evidence for abundant water in the early crust, the response of a basalt aquifer to the propagation of compressional waves (P-waves) produced by impacts in the 33-1000 km diameter size range were investigated. The resulting one-dimensional changes in effective stress and pore pressure were calculated - as a function of both distance and time - based on the following assumptions: (1) that all of the seismic energy radiated by an impact is transmitted as a single compressional wave; (2) that both the host rock and groundwater are compressible; and (3) that there is no net flow between the water-filled pores.

Seagrass blade motion under waves and its impact on wave decay

NASA Astrophysics Data System (ADS)

Luhar, M.; Infantes, E.; Nepf, H.

2017-05-01

The hydrodynamic drag generated by seagrass meadows can dissipate wave-energy, causing wave decay. It is well known that this drag depends on the relative motion between the water and the seagrass blades, yet the impact of blade motion on drag and wave-energy dissipation remains to be fully characterized. In this experimental study, we examined the impact of blade motion on wave decay by concurrently recording blade posture during a wave cycle and measuring wave decay over a model seagrass meadow. We also identified a scaling law that predicts wave decay over the model meadow for a range of seagrass blade density, wave period, wave height, and water depth scaled from typical field conditions. Blade flexibility led to significantly lower drag and wave decay relative to theoretical predictions for rigid, upright blades. To quantify the impact of blade motion on wave decay, we employed an effective blade length, le, defined as the rigid blade length that leads to equivalent wave-energy dissipation. We estimated le directly from images of blade motion. Consistent with previous studies, these estimates showed that the effective blade length depends on the dimensionless Cauchy number, which describes the relative magnitude of the wave hydrodynamic drag and the restoring force due to blade rigidity. As the hydrodynamic forcing increases, the blades exhibit greater motion. Greater blade motion leads to smaller relative velocities, reducing drag, and wave-energy dissipation (i.e., smaller le).

Oblique wave trapping by vertical permeable membrane barriers located near a wall

NASA Astrophysics Data System (ADS)

Koley, Santanu; Sahoo, Trilochan

2017-12-01

The effectiveness of a vertical partial flexible porous membrane wave barrier located near a rigid vertical impermeable seawall for trapping obliquely incident surface gravity waves are analyzed in water of uniform depth under the assumption of linear water wave theory and small amplitude membrane barrier response. From the general formulation of the submerged membrane barrier, results for bottom-standing and surface-piercing barriers are computed and analyzed in special cases. Using the eigenfunction expansion method, the boundary-value problems are converted into series relations and then the required unknowns are obtained using the least squares approximation method. Various physical quantities of interests like reflection coefficient, wave energy dissipation, wave forces acting on the membrane barrier and the seawall are computed and analyzed for different values of the wave and structural parameters. The study will be useful in the design of the membrane wave barrier for the creation of tranquility zone in the lee side of the barrier to protect the seawall.

Triad Resonance in the Gravity-Acoustic Family

NASA Astrophysics Data System (ADS)

Kadri, U.

2015-12-01

Resonance interactions of waves play a prominent role in energy share among the different wave types involved. Such interactions may significantly contribute, among others, to the evolution of the ocean energy spectrum by exchanging energy between surface-gravity waves; surface and internal gravity waves; or even surface and compression-type waves, that can transfer energy from the upper ocean through the whole water column reaching down to the seafloor. A resonant triad occurs among a triplet of waves, usually involving interaction of nonlinear terms of second order perturbed equations. Until recently, it has been believed that in a homogeneous fluid a resonant triad is possible only when tension forces are included, or at the limit of a shallow water, and that when the compressibility of water is considered, no resonant triads can occur within the family of gravity-acoustic waves. However, more recently it has been proved that, under some circumstances, resonant triads comprising two opposing surface-gravity waves of similar periods (though not identical) and a much longer acoustic-gravity wave, of almost double the frequency, exist [Kadri and Stiassnie 2013, J. Fluid Mech.735 R6]. Here, I report on a new resonant triad involving a gravity wave and two acoustic waves of almost double the length. Interestingly, the two acoustic waves propagate in the same direction with similar wavelengths, that are almost double of that of the gravity wave. The evolution of the wave triad amplitudes is periodic and it is derived analytically, in terms of Jacobian elliptic functions and elliptic integrals. The physical importance of this type of triad interactions is the modulation of pertinent acoustic signals, leading to inaccurate signal perceptions. Enclosed figure: presents an example spatio-temporal evolution of the wave triad amplitudes. The gravity wave (top) remains almost unaltered, while the envelope slowly displaces to the left. However, the prescribed acoustic envelope (middle) travels relatively fast to the right minimising the interaction time. Consequently, the resultant acoustic wave envelope (bottom) might be significantly smaller. As the two acoustic beams concurrently move away from the gravity wave, with disparate group velocities, the resonant interaction gradually vanishes.

On the Resonant Behavior of a Weakly Compressible Water Layer During Tsunamigenic Earthquakes

NASA Astrophysics Data System (ADS)

Cecioni, Claudia; Bellotti, Giorgio

2018-01-01

Tsunamigenic earthquakes trigger pressure waves in the ocean, given the weak compressibility of the sea water. For particular conditions, a resonant behavior of the water layer can occur, which influences the energy transfer from the sea-bed motion to the ocean. In this paper, the resonance conditions are explained and analyzed, focusing on the hydro-acoustic waves in the proximity of the earthquake area. A preliminary estimation of the generation parameters (sea-bed rising time, velocity) is given, by means of parametric numerical simulations for simplified conditions. The results confirm the importance of measuring, modeling, and interpreting such waves for tsunami early detection and warning.

On the Resonant Behavior of a Weakly Compressible Water Layer During Tsunamigenic Earthquakes

NASA Astrophysics Data System (ADS)

Cecioni, Claudia; Bellotti, Giorgio

2018-04-01

Tsunamigenic earthquakes trigger pressure waves in the ocean, given the weak compressibility of the sea water. For particular conditions, a resonant behavior of the water layer can occur, which influences the energy transfer from the sea-bed motion to the ocean. In this paper, the resonance conditions are explained and analyzed, focusing on the hydro-acoustic waves in the proximity of the earthquake area. A preliminary estimation of the generation parameters (sea-bed rising time, velocity) is given, by means of parametric numerical simulations for simplified conditions. The results confirm the importance of measuring, modeling, and interpreting such waves for tsunami early detection and warning.

Embedded optical fibers for PDV measurements in shock-loaded, light and heavy water

NASA Astrophysics Data System (ADS)

Mercier, Patrick; Benier, Jacky; Frugier, Pierre-Antoine; Debruyne, Michel; Bolis, Cyril

2011-06-01

In order to study the shock-detonation transition, it is necessary to characterize the shock loading of a high explosive plane wave generator into a nitromethane cell. To eliminate the reactive behaviour, we replace the nitromethane by an inert liquid compound. Light water has been first employed; eventually heavy water has been chosen for its better infrared spectral properties. We present the PDV results of different submerged embedded optical fibers which sense the medium with two different approaches: a non-intrusive optical observation of phenomena coming in front of them (interface, shock wave) followed by the mechanical interaction with the shock wave.

A shallow water model for the propagation of tsunami via Lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Zergani, Sara; Aziz, Z. A.; Viswanathan, K. K.

2015-01-01

An efficient implementation of the lattice Boltzmann method (LBM) for the numerical simulation of the propagation of long ocean waves (e.g. tsunami), based on the nonlinear shallow water (NSW) wave equation is presented. The LBM is an alternative numerical procedure for the description of incompressible hydrodynamics and has the potential to serve as an efficient solver for incompressible flows in complex geometries. This work proposes the NSW equations for the irrotational surface waves in the case of complex bottom elevation. In recent time, equation involving shallow water is the current norm in modelling tsunami operations which include the propagation zone estimation. Several test-cases are presented to verify our model. Some implications to tsunami wave modelling are also discussed. Numerical results are found to be in excellent agreement with theory.

Langmuir circulation inhibits near-surface water turbulence

NASA Astrophysics Data System (ADS)

Schultz, Colin

2012-07-01

In the surface ocean, breaking waves are a major source of air bubbles and turbulent kinetic energy. During the presence of a consistent surface wind, these wave-generated bubbles, along with other surface material like seaweed or foam, can be drawn into long rows along the surface. Driving this organization is Langmuir circulation, a phenomenon in which the wind and waves cause surface waters to rotate helically, moving like a wire wrapped around a pole in the windward direction. These spiral currents oscillate between clockwise and counterclockwise rotations, such that in some places the surface waters are pushed together and in others they are pulled apart. Researchers have previously found that at sites of convergence the bubbles produced by breaking waves are pushed to depths of 15 meters or more, with important implications for air-sea gas mixing and other processes.

Variability of bed drag on cohesive beds under wave action

USGS Publications Warehouse

Safak, Ilgar

2016-01-01

Drag force at the bed acting on water flow is a major control on water circulation and sediment transport. Bed drag has been thoroughly studied in sandy waters, but less so in muddy coastal waters. The variation of bed drag on a muddy shelf is investigated here using field observations of currents, waves, and sediment concentration collected during moderate wind and wave events. To estimate bottom shear stress and the bed drag coefficient, an indirect empirical method of logarithmic fitting to current velocity profiles (log-law), a bottom boundary layer model for combined wave-current flow, and a direct method that uses turbulent fluctuations of velocity are used. The overestimation by the log-law is significantly reduced by taking turbulence suppression due to sediment-induced stratification into account. The best agreement between the model and the direct estimates is obtained by using a hydraulic roughness of 10 -4">−4 m in the model. Direct estimate of bed drag on the muddy bed is found to have a decreasing trend with increasing current speed, and is estimated to be around 0.0025 in conditions where wave-induced flow is relatively weak. Bed drag shows an increase (up to fourfold) with increasing wave energy. These findings can be used to test the bed drag parameterizations in hydrodynamic and sediment transport models and the skills of these models in predicting flows in muddy environments.

Nonlocal Reformulations of Water and Internal Waves and Asymptotic Reductions

NASA Astrophysics Data System (ADS)

Ablowitz, Mark J.

2009-09-01

Nonlocal reformulations of the classical equations of water waves and two ideal fluids separated by a free interface, bounded above by either a rigid lid or a free surface, are obtained. The kinematic equations may be written in terms of integral equations with a free parameter. By expressing the pressure, or Bernoulli, equation in terms of the surface/interface variables, a closed system is obtained. An advantage of this formulation, referred to as the nonlocal spectral (NSP) formulation, is that the vertical component is eliminated, thus reducing the dimensionality and fixing the domain in which the equations are posed. The NSP equations and the Dirichlet-Neumann operators associated with the water wave or two-fluid equations can be related to each other and the Dirichlet-Neumann series can be obtained from the NSP equations. Important asymptotic reductions obtained from the two-fluid nonlocal system include the generalizations of the Benney-Luke and Kadomtsev-Petviashvili (KP) equations, referred to as intermediate-long wave (ILW) generalizations. These 2+1 dimensional equations possess lump type solutions. In the water wave problem high-order asymptotic series are obtained for two and three dimensional gravity-capillary solitary waves. In two dimensions, the first term in the asymptotic series is the well-known hyperbolic secant squared solution of the KdV equation; in three dimensions, the first term is the rational lump solution of the KP equation.

Loss of Water from Saturn's E-Ring Through Ion Pick-Up

NASA Technical Reports Server (NTRS)

Leisner, J. S.; Russell, C. T.; Dougherty, M. K.; Blanco-Cano, X.; Smith, E. J.; Tsurutani, B. T.

2005-01-01

One of the possible loss processes for Saturn s E-ring is ionization followed by acceleration by the electric field associated with the corotating magnetized plasma. It is possible to determine if this process is occurring by detecting electromagnetic waves at the gyrofrequency of water group ions. If the energy the particle gains in this pick-up process is sufficiently great, the picked up ions will generate ion cyclotron waves. Pioneer 11 and Voyager 1 both observed intervals of such waves associated with water group ions during their passes through Saturn s E-ring. Presently the magnetometer onboard the Cassini spacecraft is also seeing water group ion cyclotron oscillations. The Cassini data allow the spatial and temporal behavior of the waves to be mapped in ways not possible during the previous flybys. Analyses of these waves allow us to study the rate of mass loading and its latitudinal and local time variation. In conjunction with previous data, we can then determine the variation as the inclination of the ring to the Sun changes, in accordance with Saturn's seasons. These waves may be the clue to how Saturn powers its magnetosphere as the newly born ions could be the driver for the radial motion of the plasma and to how the E-ring may play the equivalent role to that of Io in the jovian magnetosphere.

The influence of pore-fluid in the soil on ground vibrations from a tunnel embedded in a layered half-space

NASA Astrophysics Data System (ADS)

Yuan, Zonghao; Cao, Zhigang; Boström, Anders; Cai, Yuanqiang

2018-04-01

A computationally efficient semi-analytical solution for ground-borne vibrations from underground railways is proposed and used to investigate the influence of hydraulic boundary conditions at the scattering surfaces and the moving ground water table on ground vibrations. The arrangement of a dry soil layer with varying thickness resting on a saturated poroelastic half-space, which includes a circular tunnel subject to a harmonic load at the tunnel invert, creates the scenario of a moving water table for research purposes in this paper. The tunnel is modelled as a hollow cylinder, which is made of viscoelastic material and buried in the half-space below the ground water table. The wave field in the dry soil layer consists of up-going and down-going waves while the wave field in the tunnel wall consists of outgoing and regular cylindrical waves. The complete solution for the saturated half-space with a cylindrical hole is composed of down-going plane waves and outgoing cylindrical waves. By adopting traction-free boundary conditions on the ground surface and continuity conditions at the interfaces of the two soil layers and of the tunnel and the surrounding soil, a set of algebraic equations can be obtained and solved in the transformed domain. Numerical results show that the moving ground water table can cause an uncertainty of up to 20 dB for surface vibrations.

Investigation of Tropical Dynamics and Transport with UARS Data

NASA Technical Reports Server (NTRS)

Jackman, Charles (Technical Monitor); Dunkerton, Timothy J.; Mote, Philip W.

2003-01-01

Our research focused on Kelvin waves in the tropical lower stratosphere, and resulted in three papers published or submitted to the Journal of Geophysical Research. The first of these, published in 2002, used temperature data from the Microwave Limb Sounder to examine the amplitude, frequency, phase, and spatial structure of leading modes of Kelvin waves. The second and third, submitted late in 2002 and currently in revision, described the response to Kelvin waves of various trace constituents measured by MLS and CLAES (methane, nitrous oxide, CFC-12, and ozone in the second paper; water vapor in the third paper). Water vapor is a special case because the vertical structure induced by Kelvin waves is convolved with water vapor's seasonally varying vertical profile induced by seasonal variations in temperature at the tropical tropopause. Forward modeling indicated that the vertical resolution of MLS was indeed adequate to capture this complicated structure, yet it was not visible in the MLS data, though the Kelvin wave signature was clear on certain UARS levels. The effects of Kelvin waves on the tropical tropopause and on stratosphere- troposphere exchange cannot be quantified from UARS data because of poor vertical resolution and sensitivity in that region. It is recommended that this analysis be repeated using data from the new MLS and HIRDLS instruments aboard Aura, and that priority be given to fine-scale retrievals of temperature, water vapor, and ozone in the tropical tropopause region.

Research of large-amplitude waves evolution in the framework of shallow water equations and their implication for people's safety in extreme situations

NASA Astrophysics Data System (ADS)

Pelinovsky, Efim; Chaikovskaia, Natalya; Rodin, Artem

2015-04-01

The paper presents the analysis of the formation and evolution of shock wave in shallow water with no restrictions on its amplitude in the framework of the nonlinear shallow water equations. It is shown that in the case of large-amplitude waves appears a new nonlinear effect of reflection from the shock front of incident wave. These results are important for the assessment of coastal flooding by tsunami waves and storm surges. Very often the largest number of victims was observed on the coastline where the wave moved breaking. Many people, instead of running away, were just looking at the movement of the "raging wall" and lost time. This fact highlights the importance of researching the problem of security and optimal behavior of people in situations with increased risk. Usually there is uncertainty about the exact time, when rogue waves will impact. This fact limits the ability of people to adjust their behavior psychologically to the stressful situations. It concerns specialists, who are busy both in the field of flying activity and marine service as well as adults, young people and children, who live on the coastal zone. The rogue wave research is very important and it demands cooperation of different scientists - mathematicians and physicists, as well as sociologists and psychologists, because the final goal of efforts of all scientists is minimization of the harm, brought by rogue waves to humanity.

Ice shelf structure from dispersion curve analysis of passive-source seismic data, Ross Ice Shelf, Antarctica

NASA Astrophysics Data System (ADS)

Diez, A.; Bromirski, P. D.; Gerstoft, P.; Stephen, R. A.; Anthony, R. E.; Aster, R. C.; Cai, C.; Nyblade, A.; Wiens, D.

2015-12-01

An L-shaped array of three-component short period seismic stations was deployed at the Ross Ice Shelf, Antarctica approximately 100 km south of the ice edge, near 180° longitude, from November 18 through 28, 2014. Polarization analysis of data from these stations clearly shows propagating waves from below the ice shelf for frequencies below 2 Hz. Energy above 2 Hz is dominated by Rayleigh and Love waves propagating from the north. Frequency-slowness plots were calculated using beamforming. Resulting Love and Rayleigh wave dispersion curves were inverted for the shear wave velocity profile, from which we derive a density profile. The derived shear wave velocity profiles differ within the firn for the inversions using Rayleigh and Love wave dispersion curves. This difference is attributed to an effective anisotropy due to fine layering. The layered structure of firn, ice, water, and ocean floor results in a characteristic dispersion curve pattern below 7 Hz. We investigate the observed structures in more detail by forward modeling of Rayleigh wave dispersion curves for representative firn, ice, water, sediment structures. Rayleigh waves are observed when wavelengths are long enough to span the distance from the ice shelf surface to the seafloor. Our results show that the analysis of high frequency Rayleigh waves on an ice shelf has the ability to resolve ice shelf thickness, water column thickness, and the physical properties of the underlying ocean floor using passive-source seismic data.

Comparative study of the expansion dynamics of laser-driven plasma and shock wave in in-air and underwater ablation regimes

NASA Astrophysics Data System (ADS)

Nguyen, Thao T. P.; Tanabe, Rie; Ito, Yoshiro

2018-03-01

We compared the expansion characteristics of the plasma plumes and shock waves generated in laser-induced shock process between the two ablation regimes: in air and under water. The observation was made from the initial moment when the laser pulse hit the target until 1.5 μs. The shock processes were driven by focusing a single laser pulse (1064 nm, FWHM = 13 ns) onto the surface of epoxy-resin blocks using a 40-mm focal length lens. The estimated laser intensity at the target plane is approximate to 9 ×109Wcm-2 . We used the fast-imaging technique to observe the expansion of the plasma plume and a custom-designed time-resolved photoelasticity imaging technique to observe the propagation of shock waves with the time resolution of nanoseconds. We found that at the same intensity of the laser beam, the plasma expansion during the laser pulse follows different mechanisms: the plasma plume that grows in air follows a radiation-wave model while a detonation-wave model can explain the expansion of the plasma plume induced in water. The ideal blast wave theory can be used to predict the decay of the shock wave in air but is not appropriate to describe the decay of the shock wave induced under water.

Frequency Domain Response at Pacific Coast Harbors to Major Tsunamis of 2005-2011

NASA Astrophysics Data System (ADS)

Xing, Xiuying; Kou, Zhiqing; Huang, Ziyi; Lee, Jiin-Jen

2013-06-01

Tsunamis waves caused by submarine earthquake or landslide might contain large wave energy, which could cause significant human loss and property damage locally as well as in distant region. The response of three harbors located at the Pacific coast (i.e. Crescent City Harbor, Los Angeles/Long Beach Port, and San Diego Harbor) to six well-known tsunamis events generated (both near-field and far-field) between 2005 and 2011 are examined and simulated using a hybrid finite element numerical model in frequency domain. The model incorporated the effects of wave refraction, wave diffraction, partial wave reflection from boundaries, entrance and bottom energy dissipation. It can be applied to harbor regions with arbitrary shapes and variable water depth. The computed resonant periods or modes of oscillation for three harbors are in good agreement with the energy spectral analysis of the time series of water surface elevations recorded at tide gauge stations inside three harbors during the six tsunamis events. The computed wave induced currents based on the present model are also in qualitative agreement with some of the reported eye-witness accounts absence of reliable current data. The simulated results show that each harbor responded differently and significantly amplified certain wave period(s) of incident wave trains according to the shape, topography, characteristic dimensions and water depth of the harbor basins.

Breaking Wave Impact on a Partially Submerged Rigid Cube in Deep Water

NASA Astrophysics Data System (ADS)

Ikeda, C. M.; Choquette, M.; Duncan, J. H.

2011-11-01

The impact of a plunging breaking wave on a partially submerged cube is studied experimentally. The experiments are performed in a wave tank that is 14.8 m long, 1.15 m wide and 2.2 m high with a water depth of 0.91 m. A single repeatable plunging breaker is generated from a dispersively focused wave packet (average frequency of 1.4 Hz) that is created with a programmable wave maker. The rigid (L = 30 . 5 cm) cube is centered in the width of the tank and mounted from above with one face oriented normal to the oncoming wave. The position of the center of the front face of the cube is varied from the breaker location (xb ~ 6 . 35 m) to xb + 0 . 05 m in the streamwise direction and from - 0 . 25 L to 0 . 25 L vertically relative to the mean water level. A high-speed digital camera is used to record both white-light and laser-induced fluorescence (LIF) movies of the free surface shape in front of the cube before and after the wave impact. When the wave hits the cube just as the plunging jet is formed, a high-velocity vertical jet is created and the trajectory and maximum height of the jet are strongly influenced by the vertical position of the cube. Supported by the Office of Naval Research, Contract Monitor R. D. Joslin.

Sedimentological effects of tsunamis, with particular reference to impact-generated and volcanogenic waves

NASA Technical Reports Server (NTRS)

Bourgeois, Joanne; Wiberg, Patricia L.

1988-01-01

Impulse-generated waves (tsunamis) may be produced, at varying scales and global recurrence intervals (RI), by several processes. Meteorite-water impacts will produce tsunamis, and asteroid-scale impacts with associated mega-tsunamis may occur. A bolide-water impact would undoubtedly produce a major tsunami, whose sedimentological effects should be recognizable. Even a bolide-land impact might trigger major submarine landslides and thus tsunamis. In all posulated scenarios for the K/T boundary event, then, tsunamis are expected, and where to look for them must be determined, and how to distinguish deposits from different tsunamis. Also, because tsunamis decrease in height as they move away from their source, the proximal effects will differ by perhaps orders of magnitude from distal effects. Data on the characteristics of tsunamis at their origin are scarce. Some observations exist for tsunamis generated by thermonuclear explosions and for seismogenic tsunamis, and experimental work was conducted on impact-generated tsunamis. All tsunamis of interest have wave-lengths of 0(100) km and thus behave as shallow-water waves in all ocean depths. Typical wave periods are 0(10 to 100) minutes. The effect of these tsunamis can be estimated in the marine and coastal realm by calculating boundary shear stresses (expressed as U*, the shear velocity). An event layer at the K/T boundary in Texas occurs in mid-shelf muds. Only a large, long-period wave with a wave height of 0(50) m, is deemed sufficient to have produced this layer. Such wave heights imply a nearby volcanic explosion on the scale of Krakatau or larger, or a nearby submarine landslide also of great size, or a bolide-water impact in the ocean.

Anisotropic changes in P-wave velocity and attenuation during deformation and fluid infiltration of granite

USGS Publications Warehouse

Stanchits, S.A.; Lockner, D.A.; Ponomarev, A.V.

2003-01-01

Fluid infiltration and pore fluid pressure changes are known to have a significant effect on the occurrence of earthquakes. Yet, for most damaging earthquakes, with nucleation zones below a few kilometers depth, direct measurements of fluid pressure variations are not available. Instead, pore fluid pressures are inferred primarily from seismic-wave propagation characteristics such as Vp/Vs ratio, attenuation, and reflectivity contacts. We present laboratory measurements of changes in P-wave velocity and attenuation during the injection of water into a granite sample as it was loaded to failure. A cylindrical sample of Westerly granite was deformed at constant confining and pore pressures of 50 and 1 MPa, respectively. Axial load was increased in discrete steps by controlling axial displacement. Anisotropic P-wave velocity and attenuation fields were determined during the experiment using an array of 13 piezoelectric transducers. At the final loading steps (86% and 95% of peak stress), both spatial and temporal changes in P-wave velocity and peak-to-peak amplitudes of P and S waves were observed. P-wave velocity anisotropy reached a maximum of 26%. Transient increases in attenuation of up to 483 dB/m were also observed and were associated with diffusion of water into the sample. We show that velocity and attenuation of P waves are sensitive to the process of opening of microcracks and the subsequent resaturation of these cracks as water diffuses in from the surrounding region. Symmetry of the orientation of newly formed microcracks results in anisotropic velocity and attenuation fields that systematically evolve in response to changes in stress and influx of water. With proper scaling, these measurements provide constraints on the magnitude and duration of velocity and attenuation transients that can be expected to accompany the nucleation of earthquakes in the Earth's crust.

Wave Reflection and Loss Characteristics of an Emerged Quarter Circle Breakwater with Varying Seaside Perforations

NASA Astrophysics Data System (ADS)

Binumol, S.; Rao, Subba; Hegde, Arkal Vittal

2017-09-01

Breakwaters are one of the most important harbour structures constructed to withstand and dissipate the dynamic energy due to the action of the waves. Due to fast growing need of the universe and advances in technology different types of breakwaters are being developed. Quarter circle breakwater is a new type of breakwater emerged from semi circular breakwater and the first model was developed in Peoples Republic of China (2006). Quarter circle breakwater with perforations posses merits of caisson as well as perforated breakwaters such as low weight, requires less materials, suited for poor soil conditions, easily transported, handled and placed at the site, aesthetically pleasing, cost effective, eco-friendly and stable. Therefore it is necessary to carry out detailed studies on hydrodynamic characteristics to investigate the suitability and applicability of various types of quarter circle breakwaters. The present study investigates the wave reflection and loss characteristics of an emerged seaside perforated quarter circle breakwater of radius 55 cm and with varying ratios of spacing to diameter of perforations, for different water depths and wave conditions. The tests were conducted in the two-dimensional monochromatic wave flume available in Marine Structures laboratory of Department of Applied Mechanics and Hydraulics of National Institute of Technology, Surathkal, Karnataka, India. The results were plotted as non-dimensional graphs and it was observed that the reflection coefficient increases with increase in wave steepness for all values of ratio of height of breakwater structure to water depth. For a constant water depth, wave reflection increases with increase in ratio of spacing to diameter of perforations. It was also found that the loss coefficient decreases with increase in wave steepness for all values of ratio of height of breakwater structure to water depth, and ratio of spacing to diameter of perforations.

Effects of wave-induced forcing on a circulation model of the North Sea

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian

2017-04-01

The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution NEMO model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force and the sea-state dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water level and current predictions.

Effects of wave-induced forcing on a circulation model of the North Sea

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian

2017-01-01

The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution Nucleus for European Modelling of the Ocean (NEMO) model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force, the sea-state-dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water-level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state-dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water-level and current predictions.

Observations and a model of undertow over the inner continental shelf

USGS Publications Warehouse

Lentz, Steven J.; Fewings, Melanie; Howd, Peter; Fredericks, Janet; Hathaway, Kent

2008-01-01

Onshore volume transport (Stokes drift) due to surface gravity waves propagating toward the beach can result in a compensating Eulerian offshore flow in the surf zone referred to as undertow. Observed offshore flows indicate that wave-driven undertow extends well offshore of the surf zone, over the inner shelves of Martha’s Vineyard, Massachusetts, and North Carolina. Theoretical estimates of the wave-driven offshore transport from linear wave theory and observed wave characteristics account for 50% or more of the observed offshore transport variance in water depths between 5 and 12 m, and reproduce the observed dependence on wave height and water depth.During weak winds, wave-driven cross-shelf velocity profiles over the inner shelf have maximum offshore flow (1–6 cm s−1) and vertical shear near the surface and weak flow and shear in the lower half of the water column. The observed offshore flow profiles do not resemble the parabolic profiles with maximum flow at middepth observed within the surf zone. Instead, the vertical structure is similar to the Stokes drift velocity profile but with the opposite direction. This vertical structure is consistent with a dynamical balance between the Coriolis force associated with the offshore flow and an along-shelf “Hasselmann wave stress” due to the influence of the earth’s rotation on surface gravity waves. The close agreement between the observed and modeled profiles provides compelling evidence for the importance of the Hasselmann wave stress in forcing oceanic flows. Summer profiles are more vertically sheared than either winter profiles or model profiles, for reasons that remain unclear.

Water vapor: An extraordinary terahertz wave source under optical excitation

NASA Astrophysics Data System (ADS)

Johnson, Keith; Price-Gallagher, Matthew; Mamer, Orval; Lesimple, Alain; Fletcher, Clark; Chen, Yunqing; Lu, Xiaofei; Yamaguchi, Masashi; Zhang, X.-C.

2008-09-01

In modern terahertz (THz) sensing and imaging spectroscopy, water is considered a nemesis to be avoided due to strong absorption in the THz frequency range. Here we report the first experimental demonstration and theoretical implications of using femtosecond laser pulses to generate intense broadband THz emission from water vapor. When we focused an intense laser pulse in water vapor contained in a gas cell or injected from a gas jet nozzle, an extraordinarily strong THz field from optically excited water vapor is observed. Water vapor has more than 50% greater THz generation efficiency than dry nitrogen. It had previously been assumed that the nonlinear generation of THz waves in this manner primarily involves a free-electron plasma, but we show that the molecular structure plays an essential role in the process. In particular, we found that THz wave generation from H2O vapor is significantly stronger than that from D2O vapor. Vibronic activities of water cluster ions, occurring naturally in water vapor, may possibly contribute to the observed isotope effect along with rovibrational contributions from the predominant monomers.

Earth's crust model of the South-Okhotsk Basin by wide-angle OBS data

NASA Astrophysics Data System (ADS)

Kashubin, Sergey N.; Petrov, Oleg V.; Rybalka, Alexander V.; Milshtein, Evgenia D.; Shokalsky, Sergey P.; Verba, Mark L.; Petrov, Evgeniy O.

2017-07-01

Deep seismic studies of the Sea of Okhotsk region started in late 1950s. Since that time, wide-angle reflection and refraction data on more than two dozen profiles were acquired. Only five of those profiles either crossed or entered the deep-water area of the South-Okhotsk Basin (also known as the Kuril Basin or the South-Okhotsk Deep-Water Trough). Only P-waves were used to develop velocity-interface models in all the early research. Thus, all seismic and geodynamic models of the Okhotsk region were based only on the information on compressional waves. Nevertheless, the use of Vp/Vs ratio in addition to P-wave velocity allows discriminating felsic and mafic crustal layers with similar Vp values. In 2007 the Russian seismic service company Sevmorgeo acquired multi-component data with ocean bottom seismometers (OBS) along the 1700-km-long north-south 2-DV-M Profile. Only P-wave information was used previously to develop models for the entire profile. In this study, a multi-wave processing, analysis, and interpretation of the OBS data are presented for the 550-km-long southern segment of this Profile that crosses the deep-water South-Okhotsk Basin. Within this segment 50 seismometers were deployed with nominal OBS station spacing of 10-12 km. Shot point spacing was 250 m. Not only primary P-waves and S-waves but also multiples and P-S, S-P converted waves were analyzed in this study to constrain velocity-interface models by means of travel time forward modeling. In offshore deep seismic studies, thick water layer hinders an estimation of velocities in the sedimentary cover and in the upper consolidated crust. Primarily, this is due to the fact that refracted waves propagating in low-velocity solid upper layers interfere with high-amplitude direct water wave. However, in multi-component measurements with ocean bottom seismometers, it is possible to use converted and multiple waves for velocity estimations in these layers. Consequently, one can obtain P- and S-waves velocity models of the sedimentary strata and the upper consolidated crust. Velocity values in the upper consolidated crust beneath the South-Okhotsk Basin (Vp = 5.50-5.80 km/s, Vp/Vs = 1.74-1.76) allow interpretation of this 2.5-3.5-km-thick layer to be consistent with a felsic (granodioritic) crust. These results suggest that the Earth's crust in this region can be considered continental in nature, rather than previously accepted oceanic crust. Even though, the crust is thinned and stretched at this location.

Effects of water saturation on P-wave propagation in fractured coals: An experimental perspective

NASA Astrophysics Data System (ADS)

Liu, Jie; Liu, Dameng; Cai, Yidong; Gan, Quan; Yao, Yanbin

2017-09-01

Internal structure of coalbed methane (CBM) reservoirs can be evaluated through ultrasonic measurements. The compressional wave that propagates in a fractured coal reservoir may indicate the internal coal structure and fluid characteristics. The P-wave propagation was proposed to study the relations between petrophysical parameters (including water saturation, fractures, porosity and permeability) of coals and the P-wave velocity (Vp), using a KON-NM-4A ultrasonic velocity meter. In this study, the relations between Vps and water saturations were established: Type I is mainly controlled by capillary of developed seepage pores. The controlling factors on Type II and Type III are internal homogeneity of pores/fractures and developed micro-fractures, respectively. Micro-fractures density linearly correlates with the Vp due to the fracture volume and dispersion of P-wave; and micro-fractures of types C and D have a priority in Vp. For dry coals, no clear relation exists between porosity, permeability and the Vp. However, as for water-saturated coals, the correlation coefficients of porosity, permeability and Vp are slightly improved. The Vp of saturated coals could be predicted with the equation of Vp-saturated = 1.4952Vp-dry-26.742 m/s. The relation between petrophysical parameters of coals and Vp under various water saturations can be used to evaluate the internal structure in fractured coals. Therefore, these relations have significant implications for coalbed methane (CBM) exploration.

Role of beach morphology in wave overtopping hazard assessment

NASA Astrophysics Data System (ADS)

Phillips, Benjamin; Brown, Jennifer; Bidlot, Jean-Raymond; Plater, Andrew

2017-04-01

Understanding the role of beach morphology in controlling wave overtopping volume will further minimise uncertainties in flood risk assessments at coastal locations defended by engineered structures worldwide. XBeach is used to model wave overtopping volume for a 1:200 yr joint probability distribution of waves and water levels with measured, pre- and post-storm beach profiles. The simulation with measured bathymetry is repeated with and without morphological evolution enabled during the modelled storm event. This research assesses the role of morphology in controlling wave overtopping volumes for hazardous events that meet the typical design level of coastal defence structures. Results show disabling storm-driven morphology under-represents modelled wave overtopping volumes by up to 39% under high Hs conditions, and has a greater impact on the wave overtopping rate than the variability applied within the boundary conditions due to the range of wave-water level combinations that meet the 1:200 yr joint probability criterion. Accounting for morphology in flood modelling is therefore critical for accurately predicting wave overtopping volumes and the resulting flood hazard and to assess economic losses.

Contribution of non-resonant wave-wave interactions in the dynamics of long-crested sea wave fields

NASA Astrophysics Data System (ADS)

Benoit, Michel

2017-04-01

Gravity waves fields at the surface of the oceans evolve under the combined effects of several physical mechanisms, of which nonlinear wave-wave interactions play a dominant role. These interactions transfer energy between components within the energy spectrum and allow in particular to explain the shape of the distribution of wave energy according to the frequencies and directions of propagation. In the oceanic domain (deep water conditions), dominant interactions are third-order resonant interactions, between quadruplets (or quartets) of wave components, and the evolution of the wave spectrum is governed by a kinetic equation, established by Hasselmann (1962) and Zakharov (1968). The kinetic equation has a number of interesting properties, including the existence of self-similar solutions and cascades to small and large wavelengths of waves, which can be studied in the framework of the wave (or weak) turbulence theory (e.g. Badulin et al., 2005). With the aim to obtain more complete and precise modelling of sea states dynamics, we investigate here the possibility and consequences of taking into account the non-resonant interactions -quasi-resonant in practice- among 4 waves. A mathematical formalism has recently been proposed to account for these non-resonant interactions in a statistical framework by Annenkov & Shrira (2006) (Generalized Kinetic Equation, GKE) and Gramstad & Stiassnie (2013) (Phase Averaged Equation, PAE). In order to isolate the non-resonant contributions, we limit ourselves here to monodirectional (i.e. long-crested) wave trains, since in this case the 4-wave resonant interactions vanish. The (stochastic) modelling approaches proposed by Annenkov & Shrira (2006) and Gramstad & Stiassnie (2013) are compared to phase-resolving (deterministic) simulations based on a fully nonlinear potential approach (using a high-order spectral method, HOS). We study and compare the evolution dynamics of the wave spectrum at different time scales (i.e. over durations ranging from a few wave periods to 1000 periods), with the aim of highlighting the capabilities and limitations of the GKE-PAE models. Different situations are considered by varying the relative water depth, the initial steepness of the wave field, and the shape of the initial wave spectrum, including arbitrary forms. References: Annenkov S.Y., Shrira V.I. (2006) Role of non-resonant interactions in the evolution of nonlinear random water wave fields. J. Fluid Mech., 561, 181-207. Badulin S.I., Pushkarev A.N., Resio D., Zakharov V.E. (2005) Self-similarity of wind-driven seas. Nonlin. Proc. Geophys., 12, 891-946. Gramstad O., Stiassnie M. (2013) Phase-averaged equation for water waves. J. Fluid Mech., 718, 280- 303. Hasselmann K. (1962) On the non-linear energy transfer in a gravity-wave spectrum. Part 1. General theory. J. Fluid Mech., 12, 481-500. Zakharov V.E. (1968) Stability of periodic waves of finite amplitude on the surface of a deep fluid. J. App. Mech. Tech. Phys., 9(2), 190-194.

Internal Waves and Wave Attractors in Enceladus' Subsurface Ocean

NASA Astrophysics Data System (ADS)

van Oers, A. M.; Maas, L. R.; Vermeersen, B. L. A.

2016-12-01

One of the most peculiar features on Saturn moon Enceladus is its so-called tiger stripe pattern at the geologically active South Polar Terrain (SPT), as first observed in detail by the Cassini spacecraft early 2005. It is generally assumed that the four almost parallel surface lines that constitute this pattern are faults in the icy surface overlying a confined salty water reservoir. In 2013, we formulated the original idea [Vermeersen et al., AGU Fall Meeting 2013, abstract #P53B-1848] that the tiger stripe pattern is formed and maintained by induced, tidally and rotationally driven, wave-attractor motions in the ocean underneath the icy surface of the tiger-stripe region. Such wave-attractor motions are observed in water tank experiments in laboratories on Earth and in numerical experiments [Maas et al., Nature, 338, 557-561, 1997; Drijfhout and Maas, J. Phys. Oceanogr., 37, 2740-2763, 2007; Hazewinkel et al., Phys. Fluids, 22, 107102, 2010]. Numerical simulations show the persistence of wave attractors for a range of ocean shapes and stratifications. The intensification of the wave field near the location of the surface reflections of wave attractors has been numerically and experimentally confirmed. We measured the forces a wave attractor exerts on a solid surface, near a reflection point. These reflection points would correspond to the location of the tiger stripes. Combining experiments and numerical simulations we conclude that (1) wave attractors can exist in Enceladus' subsurface sea, (2) their shape can be matched to the tiger stripes, (3) the wave attractors cause a localized force at the water-ice boundaries, (4) this force could have been large enough to contribute to fracturing the ice and (5) the wave attractors localize energy (and particles) and cause dissipation along its path, helping explain Enceladus' enigmatic heat output at the tiger stripes.

Reduced-order prediction of rogue waves in two-dimensional deep-water waves

NASA Astrophysics Data System (ADS)

Sapsis, Themistoklis; Farazmand, Mohammad

2017-11-01

We consider the problem of large wave prediction in two-dimensional water waves. Such waves form due to the synergistic effect of dispersive mixing of smaller wave groups and the action of localized nonlinear wave interactions that leads to focusing. Instead of a direct simulation approach, we rely on the decomposition of the wave field into a discrete set of localized wave groups with optimal length scales and amplitudes. Due to the short-term character of the prediction, these wave groups do not interact and therefore their dynamics can be characterized individually. Using direct numerical simulations of the governing envelope equations we precompute the expected maximum elevation for each of those wave groups. The combination of the wave field decomposition algorithm, which provides information about the statistics of the system, and the precomputed map for the expected wave group elevation, which encodes dynamical information, allows (i) for understanding of how the probability of occurrence of rogue waves changes as the spectrum parameters vary, (ii) the computation of a critical length scale characterizing wave groups with high probability of evolving to rogue waves, and (iii) the formulation of a robust and parsimonious reduced-order prediction scheme for large waves. T.S. has been supported through the ONR Grants N00014-14-1-0520 and N00014-15-1-2381 and the AFOSR Grant FA9550-16-1-0231. M.F. has been supported through the second Grant.

The interaction of extreme waves with hull elements

NASA Astrophysics Data System (ADS)

Galiev, Shamil; Flay, Richard

2010-05-01

The problem of the impact of a rogue wave onto a deformable marine structure is formulated in a few publications (see, for example, a short review in http://researchspace.auckland.ac.nz/handle/2292/4474). In this paper the results from numerical and experimental investigations of the effect of cavitation on the deformation of a hull element, loaded by a wall of water, generated by an extreme ocean surface wave are considered. The hull element is modelled as a circular metal plate with the edge of the plate rigidly clamped. The plate surface is much smaller than the surface of the wave front, so that at the initial moment of the interaction, the pressure is constant on the plate surface. At the next instant, because of the plate deformation, axisymmetric loading of the plate occurs. The influences of membrane forces and plastic deformations are ignored, and therefore, the equation of plate motion has the following classical form Eh3(wrrrr+2r -1wrrrr- r-2wrr+r-3wr) = - 121- ν2)[ρhwtt+ δ(r,t)(p+ ρ0a0wt)]. Here w is the plate displacement, subscripts t and rindicate derivatives with respect to time and the radial coordinate, PIC is the plate material density, his the plate thickness, Eis Young's modulus, PIC is Poisson's ratio and p is the pressure of the incident surface wave measured on the wall, PIC is the water density, PIC is the speed of sound in water, and PIC is the normal velocity of the plate. The term PIC takes into account the effect of the deformability of the plate. Obviously, the hull of a vessel is not rigid like a solid wall, but starts to deform and to move. This motion produces a reflected pressure wave, which travels from the hull into the water wave with a magnitude equal to PIC . The normal velocity is positive so the reflected pressure PIC is negative (tensile wave). If the fluid pressure drops below some critical value pk, the wet plate surface separates from the water, and cavitation may be generated. The function δ(r,t) takes into account the effect of the hull cavitation. The function PIC or 0, and is determined during the numerical calculations. Case PIC is valid for the case with no cavitation, and the case δ(r,t) = 0 corresponds to the case with hull cavitation. The results from these calculations allow us to draw the following conclusions. 1) The pressures generated depend greatly on the irregularity of waves. In particular, the shock pressures are affected by this irregularity, making the prediction of their magnitude almost impossible. 2) In the majority of cases, the elastic deformation of thin hull elements by a short duration water wave pressure pulse is accompanied by hull cavitation. The effect of cavitation may be important, provided that the time of loading by the water wall pressure is less than the period of the fundamental frequency of the hull element oscillations. 3) The cavitation zones can enclose practically the whole wet surface and thus completely change the water loading onto the hull element, compared to the pressures that would be developed in the absence of cavitation. 4) The hull element deformation generates surface pressure and cavitation waves. 5) Cavitation interaction of extreme water waves with structures, and hull response, are complex topics, which are not well understood and are expected to be important in the design of advanced ships in the future. 6) The existence of rogue waves makes it important to re-examine some of the ideas developed earlier which are fundamental to merchant ship design.

Simulation of Wave-Current Interaction Using a Three-Dimensional Hydrodynamic Model Coupled With a Phase Averaged Wave Model

NASA Astrophysics Data System (ADS)

Marsooli, R.; Orton, P. M.; Georgas, N.; Blumberg, A. F.

2016-02-01

The Stevens Institute of Technology Estuarine and Coastal Ocean Model (sECOM) has been coupled with a more advanced surface wave model to simulate wave‒current interaction, and results have been validated in estuarine and nearshore waters. sECOM is a three‒dimensional, hydrostatic, free surface, primitive equation model. It solves the Navier‒Stokes equations and the conservation equations for temperature and salinity using a finite‒difference method on an Arakawa C‒grid with a terrain‒following (sigma) vertical coordinate and orthogonal curvilinear horizontal coordinate system. The model is coupled with the surface wave model developed by Mellor et al. (2008), which solves the spectral equation and takes into account depth and current refraction, and deep and shallow water. The wave model parameterizes the energy distribution in frequency space and the wave‒wave interaction process by using a specified spectrum shape. The coupled wave‒hydrodynamic model considers the wave‒current interaction through wave‒induced bottom stress, depth‒dependent radiation stress, and wave effects on wind‒induced surface stress. The model is validated using the data collected at a natural sandy beach at Duck, North Carolina, during the DUCK94 experiment. This test case reveals the capability of the model to simulate the wave‒current interaction in nearshore coastal systems. The model is further validated using the data collected in Jamaica Bay, a semi‒enclosed body of water located in New York City region. This test reveals the applicability of the model to estuarine systems. These validations of the model and comparisons to its prior wave model, the Great Lakes Environmental Research Laboratory (GLERL) wave model (Donelan 1977), are presented and discussed. ReferencesG.L. Mellor, M.A. Donelan, and L‒Y. Oey, 2008, A Surface Wave Model for Coupling with Numerical Ocean Circulation Models. J. Atmos. Oceanic Technol., 25, 1785‒1807.Donelan, M. A 1977. A simple numerical model for wave and wind stress application. Report, National Water Research Institute, Burlington, Ontario, Canada, 28 pp.

Mathematical model of snake-type multi-directional wave generation

NASA Astrophysics Data System (ADS)

Muarif; Halfiani, Vera; Rusdiana, Siti; Munzir, Said; Ramli, Marwan

2018-01-01

Research on extreme wave generation is one intensive research on water wave study because the fact that the occurrence of this wave in the ocean can cause serious damage to the ships and offshore structures. One method to be used to generate the wave is self-correcting. This method controls the signal on the wavemakers in a wave tank. Some studies also consider the nonlinear wave generation in a wave tank by using numerical approach. Study on wave generation is essential in the effectiveness and efficiency of offshore structure model testing before it can be operated in the ocean. Generally, there are two types of wavemakers implemented in the hydrodynamic laboratory, piston-type and flap-type. The flap-type is preferred to conduct a testing to a ship in deep water. Single flap wavemaker has been explained in many studies yet snake-type wavemaker (has more than one flap) is still a case needed to be examined. Hence, the formulation in controlling the wavemaker need to be precisely analyzed such that the given input can generate the desired wave in the space-limited wave tank. By applying the same analogy and methodhology as the previous study, this article represents multi-directional wave generation by implementing snake-type wavemakers.

Noninvasive measurement of wave speed of porcine cornea in ex vivo porcine eyes for various intraocular pressures.

PubMed

Zhou, Boran; Sit, Arthur J; Zhang, Xiaoming

2017-11-01

The objective of this study was to extend an ultrasound surface wave elastography (USWE) technique for noninvasive measurement of ocular tissue elastic properties. In particular, we aim to establish the relationship between the wave speed of cornea and the intraocular pressure (IOP). Normal ranges of IOP are between 12 and 22mmHg. Ex vivo porcine eye balls were used in this research. The porcine eye ball was supported by the gelatin phantom in a testing container. Some water was pour into the container for the ultrasound measurement. A local harmonic vibration was generated on the side of the eye ball. An ultrasound probe was used to measure the wave propagation in the cornea noninvasively. A 25 gauge butterfly needle was inserted into the vitreous humor of the eye ball under the ultrasound imaging guidance. The needle was connected to a syringe. The IOP was obtained by the water height difference between the water level in the syringe and the water level in the testing container. The IOP was adjusted between 5mmHg and 30mmHg with a 5mmHg interval. The wave speed was measured at each IOP for three frequencies of 100, 150 and 200Hz. Finite element method (FEM) was used to simulate the wave propagation in the corneal according to our experimental setup. A linear viscoelastic FEM model was used to compare the experimental data. Both the experiments and the FEM analyses showed that the wave speed of cornea increased with IOP. Copyright © 2017 Elsevier B.V. All rights reserved.

Modification of land-atmosphere interactions by CO2 effects: Implications for summer dryness and heat wave amplitude

NASA Astrophysics Data System (ADS)

Lemordant, Léo.; Gentine, Pierre; Stéfanon, Marc; Drobinski, Philippe; Fatichi, Simone

2016-10-01

Plant stomata couple the energy, water, and carbon cycles. We use the framework of Regional Climate Modeling to simulate the 2003 European heat wave and assess how higher levels of surface CO2 may affect such an extreme event through land-atmosphere interactions. Increased CO2 modifies the seasonality of the water cycle through stomatal regulation and increased leaf area. As a result, the water saved during the growing season through higher water use efficiency mitigates summer dryness and the heat wave impact. Land-atmosphere interactions and CO2 fertilization together synergistically contribute to increased summer transpiration. This, in turn, alters the surface energy budget and decreases sensible heat flux, mitigating air temperature rise. Accurate representation of the response to higher CO2 levels and of the coupling between the carbon and water cycles is therefore critical to forecasting seasonal climate, water cycle dynamics, and to enhance the accuracy of extreme event prediction under future climate.

Method and apparatus for measuring surface contour on parts with elevated temperatures

DOEpatents

Horvath, Mark S.; Nance, Roy A.; Cohen, George H.; Fodor, George

1991-01-01

The invention is directed to a method and apparatus for measuring the surface contour of a test piece, such as the bow of a radioactive fuel rod, which is completely immersed in water. The invention utilizes ultrasonic technology and is capable of measuring surface contours of test pieces which are at a higher temperature than the surrounding water. The presence of a test piece at a higher temperature adversely affects the distance measurements by causing thermal variations in the water near the surface of the test piece. The contour measurements depend upon a constant temperature of the water in the path of the ultrasonic wave to provide a constant acoustical velocity (the measurement is made by the time of flight measurement for an ultrasonic wave). Therefore, any variations of water temperature near the surface will introduce errors degrading the measurement. The present invention overcomes these problems by assuring that the supply of water through which the ultrasonic waves travel is at a predetermined and constant temperature.

Optodynamic characterization of shock waves after laser-induced breakdown in water.

PubMed

Petkovsek, Rok; Mozina, Janez; Mocnik, Grisa

2005-05-30

Plasma and a cavitation bubble develop at the site of laser-induced breakdown in water. Their formation and the propagation of the shock wave were monitored by a beam-deflection probe and an arm-compensated interferometer. The interferometer part of the setup was used to determine the relative position of the laser-induced breakdown. The time-of-flight data from the breakdown site to the probe beam yielded the velocity, and from the velocity the shock-wave pressure amplitudes were calculated. Two regions were found where the pressure decays with different exponents, pointing to a strong attenuation mechanism in the initial phase of the shock-wave propagation.

The effects of pressure, temperature, and pore water on velocities in Westerly granite. [for seismic wave propagation

NASA Technical Reports Server (NTRS)

Spencer, J. W., Jr.; Nur, A. M.

1976-01-01

A description is presented of an experimental assembly which has been developed to conduct concurrent measurements of compressional and shear wave velocities in rocks at high temperatures and confining pressures and with independent control of the pore pressure. The apparatus was used in studies of the joint effects of temperature, external confining pressure, and internal pore water on sonic velocities in Westerly granite. It was found that at a given temperature, confining pressure has a larger accelerating effect on compressional waves in dry rock, whereas at a given confining pressure, temperature has a larger retarding effect on shear waves.

History of shock wave lithotripsy

NASA Astrophysics Data System (ADS)

Delius, Michael

2000-07-01

The first reports on the fragmentation of human calculi with ultrasound appeared in the fifties. Initial positive results with an extracorporeal approach with continuous wave ultrasound could, however, not be reproduced. A more promising result was found by generating the acoustic energy either in pulsed or continuous form directly at the stone surface. The method was applied clinically with success. Extracorporeal shock-wave generators unite the principle of using single ultrasonic pulses with the principle of generating the acoustic energy outside the body and focusing it through the skin and body wall onto the stone. Häusler and Kiefer reported the first successful contact-free kidney stone destruction by shock waves. They had put the stone in a water filled cylinder and generated a shock wave with a high speed water drop which was fired onto the water surface. To apply the new principle in medicine, both Häusler and Hoff's group at Dornier company constructed different shock wave generators for the stone destruction; the former used a torus-shaped reflector around an explosion wire, the latter the electrode-ellipsoid system. The former required open surgery to access the kidney stone, the latter did not. It was introduced into clinical practice after a series of experiments in Munich.

Experimental investigation of the propagation of a planar shock wave through a two-phase gas-liquid medium

NASA Astrophysics Data System (ADS)

Chauvin, A.; Jourdan, G.; Daniel, E.; Houas, L.; Tosello, R.

2011-11-01

We conducted a series of shock tube experiments to study the influence of a cloud of water droplets on the propagation of a planar shock wave. In a vertically oriented shock tube, the cloud of droplets was released downwards into the air at atmospheric pressure while the shock wave propagated upwards. Two shock wave Mach numbers, 1.3 and 1.5, and three different heights of clouds, 150 mm, 400 mm, and 700 mm, were tested with an air-water volume fraction and a droplet diameter fixed at 1.2% and 500 μm, respectively. From high-speed visualization and pressure measurements, we analyzed the effect of water clouds on the propagation of the shock wave. It was shown that the pressure histories recorded in the two-phase gas-liquid mixture are different from those previously obtained in the gas-solid case. This different behavior is attributed to the process of atomization of the droplets, which is absent in the gas-solid medium. Finally, it was observed that the shock wave attenuation was dependent on the exchange surface crossed by the shock combined with the breakup criterion.

AKNS eigenvalue spectrum for densely spaced envelope solitary waves

NASA Astrophysics Data System (ADS)

Slunyaev, Alexey; Starobor, Alexey

2010-05-01

The problem of the influence of one envelope soliton to the discrete eigenvalues of the associated scattering problem for the other envelope soliton, which is situated close to the first one, is discussed. Envelope solitons are exact solutions of the integrable nonlinear Schrödinger equation (NLS). Their generalizations (taking into account the background nonlinear waves [1-4] or strongly nonlinear effects [5, 6]) are possible candidates to rogue waves in the ocean. The envelope solitary waves could be in principle detected in the stochastic wave field by approaches based on the Inverse Scattering Technique in terms of ‘unstable modes' (see [1-3]), or envelope solitons [7-8]. However, densely spaced intense groups influence the spectrum of the associated scattering problem, so that the solitary trains cannot be considered alone. Here we solve the initial-value problem exactly for some simplified configurations of the wave field, representing two closely placed intense wave groups, within the frameworks of the NLS equation by virtue of the solution of the AKNS system [9]. We show that the analogues of the level splitting and the tunneling effects, known in quantum physics, exist in the context of the NLS equation, and thus may be observed in application to sea waves [10]. These effects make the detecting of single solitary wave groups surrounded by other nonlinear wave groups difficult. [1]. A.L. Islas, C.M. Schober (2005) Predicting rogue waves in random oceanic sea states. Phys. Fluids 17, 031701-1-4. [2]. A.R. Osborne, M. Onorato, M. Serio (2005) Nonlinear Fourier analysis of deep-water random surface waves: Theoretical formulation and and experimental observations of rogue waves. 14th Aha Huliko's Winter Workshop, Honolulu, Hawaii. [3]. C.M. Schober, A. Calini (2008) Rogue waves in higher order nonlinear Schrödinger models. In: Extreme Waves (Eds.: E. Pelinovsky & C. Kharif), Springer. [4]. N. Akhmediev, A. Ankiewicz, M. Taki (2009) Waves that appear from nowhere and disappear without a trace. Phys. Lett. A 373, 675-678. [5]. A.I. Dyachenko, V.E. Zakharov (2008) On the formation of freak waves on the surface of deep water. JETP Lett. 88 (5), 307-311. [6]. A.V. Slunyaev (2009) Numerical simulation of "limiting" envelope solitons of gravity waves on deep water. JETP 109, 676-686. [7]. A. Slunyaev, E. Pelinovsky, and C. Guedes Soares (2005) Modeling freak waves from the North Sea. Appl. Ocean Res. 27, 12-22. [8]. A. Slunyaev (2006) Nonlinear analysis and simulations of measured freak wave time series. Eur. J. Mech. B / Fluids 25, 621-635. [9]. M.J. Ablowitz, D.J. Kaup, A.C. Newell, H. Segur (1974) The inverse scattering transform - Fourier analysis for nonlinear problems. Stud. Appl. Math. 53, 249-315. [10]. A.V. Starobor (2009) Interpretation of the inverse scattering data for the analysis of wave groups on water surface. Bachelor degree thesis. N. Novgorod State University, in Russian.

The Seasat SAR Wind and Ocean Wave Monitoring Capabilities: A case study for pass 1339m

NASA Technical Reports Server (NTRS)

Beal, R. C.

1980-01-01

A well organized low energy 11 sec. swell system off the East Coast of the U.S. was detected with the Seasat Synthetic Aperture Radar and successfully tracked from deep water, across the continental shelf, and into shallow water. In addition, a less organized 7 sec. system was tentatively identified in the imagery. Both systems were independently confirmed with simultaneous wave spectral measurements from a research pier, aircraft laser profilometer data, and Fleet Numerical Spectral Ocean Wave Models.

Spatial Statistics of Deep-Water Ambient Noise; Dispersion Relations for Sound Waves and Shear Waves

DTIC Science & Technology

2014-09-30

marine sediments. New focus is on very fine- grained sediments (silt and clay ). OBJECTIVES 1) The scientific objective of the deep-water ambient...density, grain size and overburden pressure. A new focus is on the inter-particle cohesive forces in silts and clays and their role in controlling wave...algebraic expressions. The GS theory is the basis for new research on very fine-grained sediments (silts and clays ), in which inter-granular cohesion is

An Analytical Model of Periodic Waves in Shallow Water--Summary.

DTIC Science & Technology

1984-01-01

Petviashvili equation , and is based on a Riemann theta function of genus 2. These bi-periodic waves are direct generalizations of the well-known (simply... Petviashvili (KP; 1970) equation , (ut 6uux + U ) 3uyy -0, (1) is a scaled, dimensionless equation that describes the evolution of long water waves of...Fluid Mech., vol. 92, pp 691-715 Dubrovin, B. A., 1981, Russ. Math. Surveys, vol. 36, pp 11-92 Kadomtsev , B. B. & V. I. Petviashvili , 1970,) Soy. Phys

Simulation of Water Waves by Boussinesq Models

DTIC Science & Technology

1998-03-01

as nonlinearity. The other independent parameter is the ratio of water depth to wave length (fi = ho/L) or equivalently, the product of wavenumber...tw [l - (1 + 2a)//2] <f>\\A = 0 (2.118) Terms with products of 7?i,m and fatm (m = —1,1) indicate nonlinear interaction between the first order... product for u and ß is essential to the stability of uniform Stokes waves. From the analytical solutions, the values of u>" are always nega- tive. However

Application of Temperature-Dependent Fluorescent Dyes to the Measurement of Millimeter Wave Absorption in Water Applied to Biomedical Experiments

PubMed Central

Popenko, Oleksandr

2014-01-01

Temperature sensitivity of the fluorescence intensity of the organic dyes solutions was used for noncontact measurement of the electromagnetic millimeter wave absorption in water. By using two different dyes with opposite temperature effects, local temperature increase in the capillary that is placed inside a rectangular waveguide in which millimeter waves propagate was defined. The application of this noncontact temperature sensing is a simple and novel method to detect temperature change in small biological objects. PMID:25435859

Application of temperature-dependent fluorescent dyes to the measurement of millimeter wave absorption in water applied to biomedical experiments.

PubMed

Kuzkova, Nataliia; Popenko, Oleksandr; Yakunov, Andrey

2014-01-01

Temperature sensitivity of the fluorescence intensity of the organic dyes solutions was used for noncontact measurement of the electromagnetic millimeter wave absorption in water. By using two different dyes with opposite temperature effects, local temperature increase in the capillary that is placed inside a rectangular waveguide in which millimeter waves propagate was defined. The application of this noncontact temperature sensing is a simple and novel method to detect temperature change in small biological objects.

Wave- and tidally-driven flow and sediment flux across a fringing coral reef: Southern Molokai, Hawaii

USGS Publications Warehouse

Storlazzi, C.D.; Ogston, A.S.; Bothner, Michael H.; Field, M.E.; Presto, M.K.

2004-01-01

The fringing coral reef off the south coast of Molokai, Hawaii is currently being studied as part of a US Geological Survey (USGS) multi-disciplinary project that focuses on geologic and oceanographic processes that affect coral reef systems. For this investigation, four instrument packages were deployed across the fringing coral reef during the summer of 2001 to understand the processes governing fine-grained terrestrial sediment suspension on the shallow reef flat (h=1m) and its advection across the reef crest and onto the deeper fore reef. The time-series measurements suggest the following conceptual model of water and fine-grained sediment transport across the reef: Relatively cool, clear water flows up onto the reef flat during flooding tides. At high tide, more deep-water wave energy is able to propagate onto the reef flat and larger Trade wind-driven waves can develop on the reef flat, thereby increasing sediment suspension. Trade wind-driven surface currents and wave breaking at the reef crest cause setup of water on the reef flat, further increasing the water depth and enhancing the development of depth-limited waves and sediment suspension. As the tide ebbs, the water and associated suspended sediment on the reef flat drains off the reef flat and is advected offshore and to the west by Trade wind- and tidally- driven currents. Observations on the fore reef show relatively high turbidity throughout the water column during the ebb tide. It therefore appears that high suspended sediment concentrations on the deeper fore reef, where active coral growth is at a maximum, are dynamically linked to processes on the muddy, shallow reef flat.

Coastal loading and transport of Escherichia coli at an embayed beach in Lake Michigan

USGS Publications Warehouse

Ge, Z.; Nevers, M.B.; Schwab, D.J.; Whitman, R.L.

2010-01-01

A Chicago beach in southwest Lake Michigan was revisited to determine the influence of nearshore hydrodynamic effects on the variability of Escherichia coli (E. coli) concentration in both knee-deep and offshore waters. Explanatory variables that could be used for identifying potential bacteria loading mechanisms, such as bed shear stress due to a combined wave-current boundary layer and wave runup on the beach surface, were derived from an existing wave and current database. The derived hydrodynamic variables, along with the actual observed E. coli concentrations in the submerged and foreshore sands, were expected to reveal bacteria loading through nearshore sediment resuspension and swash on the beach surface, respectively. Based on the observation that onshore waves tend to result in a more active hydrodynamic system at this embayed beach, multiple linear regression analysis of onshore-wave cases further indicated the significance of sediment resuspension and the interaction of swash with gull-droppings in explaining the variability of E. coli concentration in the knee-deep water. For cases with longshore currents, numerical simulations using the Princeton Ocean Model revealed current circulation patterns inside the embayment, which can effectively entrain bacteria from the swash zone into the central area of the embayed beach water and eventually release them out of the embayment. The embayed circulation patterns are consistent with the statistical results that identified that 1) the submerged sediment was an additional net source of E. coli to the offshore water and 2) variability of E. coli concentration in the knee-deep water contributed adversely to that in the offshore water for longshore-current cases. The embayed beach setting and the statistical and numerical methods used in the present study have wide applicability for analyzing recreational water quality at similar marine and freshwater sites. ?? 2010 American Chemical Society.

In-Service Monitoring of Steam Pipe Systems at High Temperatures

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; Badescu, Mircea; Bao, Xiaoqi; Sherrit, Stewart; Scott, James S.; Blosiu, Julian O.; Widholm, Scott E.

2011-01-01

An effective, in-service health monitoring system is needed to track water condensation in real time through the walls of steam pipes. The system is required to measure the height of the condensed water from outside the pipe, while operating at temperatures that are as high as 250 C. The system needs to account for the effects of water flow and cavitation. In addition, it is desired that the system does not require perforating the pipes and thereby reducing the structural integrity. Generally, steam pipes are used as part of the district heating system carrying steam from central power stations under the streets to heat, cool, or supply power to high-rise buildings and businesses. This system uses ultrasonic waves in pulse-echo and acquires reflected signal data. Via autocorrelation, it determines the water height while eliminating the effect of noise and multiple reflections from the wall of the pipe. The system performs nondestructive monitoring through the walls of steam pipes, and automatically measures the height of condensed water while operating at the high-temperature conditions of 250 C. For this purpose, the ultrasonic pulse-echo method is used where the time-of-flight of the wave reflections inside the water are measured, and it is multiplied by the wave velocity to determine the height. The pulse-echo test consists of emitting ultrasonic wave pulses from a piezoelectric transducer and receiving the reflections from the top and bottom of the condensed water. A single transducer is used as a transmitter as well as the receiver of the ultrasonic waves. To obtain high resolution, a broadband transducer is used and the frequency can be in the range of 2.25 to 10 MHz, providing sharp pulses in the time domain allowing for higher resolution in identifying the individual reflections.

Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Overview and spectral characteristics

NASA Technical Reports Server (NTRS)

Glassmeier, Karl-Heinz; Neubauer, Fritz M.

1993-01-01

Large-amplitude electromagnetic plasma waves are one of the dominant features of the solar wind-comet interaction. Wave characteristics strongly depend on parameters such as the solar wind flow and Alfven velocities and the angle between flow and interplanetary magnetic field as well as the production rate. With respect to the latter the flyby of the spacecraft Giotto at comet P/Griff-Skjellerup provides a unique possibility to study such waves in further detail. Pickup ion-related wave signatures have been observed up to a distance of 600,000 km from the nucleus. Peak spectral power in the spacecraft frame of reference occurs at frequencies mainly somewhat below the water group ion gyrofrequency. From this the waves are determined to be mainly left-hand polarized waves, causing one-sided pitch angle diffusion outbound. The wave activity strongly increases close to the comet; upstream it exhibits a quadratic dependence on the water group pickup ion free energy. Furthermore, a phenomenological study of the wave characteristics provides a unique description of the fine-structure of the interaction region. Indications of steepened magnetosonic waves have been found in the outbound magnetosheath region.

Study on unsteady hydrodynamic performance of propeller in waves

NASA Astrophysics Data System (ADS)

Zhao, Qingxin; Guo, Chunyu; Su, Yumin; Liu, Tian; Meng, Xiangyin

2017-09-01

The speed of a ship sailing in waves always slows down due to the decrease in efficiency of the propeller. So it is necessary and essential to analyze the unsteady hydrodynamic performance of propeller in waves. This paper is based on the numerical simulation and experimental research of hydrodynamics performance when the propeller is under wave conditions. Open-water propeller performance in calm water is calculated by commercial codes and the results are compared to experimental values to evaluate the accuracy of the numerical simulation method. The first-order Volume of Fluid (VOF) wave method in STAR CCM+ is utilized to simulate the three-dimensional numerical wave. According to the above prerequisite, the numerical calculation of hydrodynamic performance of the propeller under wave conditions is conducted, and the results reveal that both thrust and torque of the propeller under wave conditions reveal intense unsteady behavior. With the periodic variation of waves, ventilation, and even an effluent phenomenon appears on the propeller. Calculation results indicate, when ventilation or effluent appears, the numerical calculation model can capture the dynamic characteristics of the propeller accurately, thus providing a significant theory foundation for further studying the hydrodynamic performance of a propeller in waves.

A numerical model investigation of the impacts of Hurricane Sandy on water level variability in Great South Bay, New York

USGS Publications Warehouse

Bennett, Vanessa C. C.; Mulligan, Ryan P.; Hapke, Cheryl J.

2018-01-01

Hurricane Sandy was a large and intense storm with high winds that caused total water levels from combined tides and storm surge to reach 4.0 m in the Atlantic Ocean and 2.5 m in Great South Bay (GSB), a back-barrier bay between Fire Island and Long Island, New York. In this study the impact of the hurricane winds and waves are examined in order to understand the flow of ocean water into the back-barrier bay and water level variations within the bay. To accomplish this goal, a high resolution hurricane wind field is used to drive the coupled Delft3D-SWAN hydrodynamic and wave models over a series of grids with the finest resolution in GSB. The processes that control water levels in the back-barrier bay are investigated by comparing the results of four cases that include: (i) tides only; (ii) tides, winds and waves with no overwash over Fire Island allowed; (iii) tides, winds, waves and limited overwash at the east end of the island; (iv) tides, winds, waves and extensive overwash along the island. The results indicate that strong local wind-driven storm surge along the bay axis had the largest influence on the total water level fluctuations during the hurricane. However, the simulations allowing for overwash have higher correlation with water level observations in GSB and suggest that island overwash provided a significant contribution of ocean water to eastern GSB during the storm. The computations indicate that overwash of 7500–10,000 m3s−1 was approximately the same as the inflow from the ocean through the major existing inlet. Overall, the model results indicate the complex variability in total water levels driven by tides, ocean storm surge, surge from local winds, and overwash that had a significant impact on the circulation in Great South Bay during Hurricane Sandy.

A numerical model investigation of the impacts of Hurricane Sandy on water level variability in Great South Bay, New York

NASA Astrophysics Data System (ADS)

Bennett, Vanessa C. C.; Mulligan, Ryan P.; Hapke, Cheryl J.

2018-06-01

Hurricane Sandy was a large and intense storm with high winds that caused total water levels from combined tides and storm surge to reach 4.0 m in the Atlantic Ocean and 2.5 m in Great South Bay (GSB), a back-barrier bay between Fire Island and Long Island, New York. In this study the impact of the hurricane winds and waves are examined in order to understand the flow of ocean water into the back-barrier bay and water level variations within the bay. To accomplish this goal, a high resolution hurricane wind field is used to drive the coupled Delft3D-SWAN hydrodynamic and wave models over a series of grids with the finest resolution in GSB. The processes that control water levels in the back-barrier bay are investigated by comparing the results of four cases that include: (i) tides only; (ii) tides, winds and waves with no overwash over Fire Island allowed; (iii) tides, winds, waves and limited overwash at the east end of the island; (iv) tides, winds, waves and extensive overwash along the island. The results indicate that strong local wind-driven storm surge along the bay axis had the largest influence on the total water level fluctuations during the hurricane. However, the simulations allowing for overwash have higher correlation with water level observations in GSB and suggest that island overwash provided a significant contribution of ocean water to eastern GSB during the storm. The computations indicate that overwash of 7500-10,000 m3s-1 was approximately the same as the inflow from the ocean through the major existing inlet. Overall, the model results indicate the complex variability in total water levels driven by tides, ocean storm surge, surge from local winds, and overwash that had a significant impact on the circulation in Great South Bay during Hurricane Sandy.

Analysis of the Tangjiaxi landslide-generated waves in the Zhexi Reservoir, China, by a granular flow coupling model

NASA Astrophysics Data System (ADS)

Huang, Bolin; Yin, Yueping; Wang, Shichang; Tan, Jianmin; Liu, Guangning

2017-05-01

A rocky granular flow is commonly formed after the failure of rocky bank slopes. An impulse wave disaster may also be initiated if the rocky granular flow rushes into a river with a high velocity. Currently, the granular mass-water body coupling study is an important trend in the field of landslide-induced impulse waves. In this paper, a full coupling numerical model for landslide-induced impulse waves is developed based on a non-coherent granular flow equation, i.e., the Mih equation. In this model, the Mih equation for continuous non-coherent granular flow controls movements of sliding mass, the two-phase flow equation regulates the interaction between sliding mass and water, and the renormalization group (RNG) turbulence model governs the movement of the water body. The proposed model is validated and applied for the 2014 Tangjiaxi landslide of the Zhexi Reservoir located in Hunan Province, China, to analyze the characteristics of both landslide motion and its following impulse waves. On 16 July 2014, a rocky debris flow was formed after the failure of the Tangjiaxi landslide, damming the Tangjiaxi stream and causing an impulse wave disaster with three dead and nine missing bodies. Based on the full coupling numerical analysis, the granular flow impacts the water with a maximum velocity of about 22.5 m s-1. Moreover, the propagation velocity of the generated waves reaches up to 12 m s-1. The maximum calculated run-up of 21.8 m is close enough to the real value of 22.7 m. The predicted landslide final deposit and wave run-up heights are in a good agreement with the field survey data. These facts verify the ability of the proposed model for simulating the real impulse wave generated by rocky granular flow events.

Impacts of short-time scale water column variability on broadband high-frequency acoustic wave propagation

NASA Astrophysics Data System (ADS)

Eickmeier, Justin

Acoustical oceanography is one way to study the ocean, its internal layers, boundaries and all processes occurring within using underwater acoustics. Acoustical sensing techniques allows for the measurement of ocean processes from within that logistically or financially preclude traditional in-situ measurements. Acoustic signals propagate as pressure wavefronts from a source to a receiver through an ocean medium with variable physical parameters. The water column physical parameters that change acoustic wave propagation in the ocean include temperature, salinity, current, surface roughness, seafloor bathymetry, and vertical stratification over variable time scales. The impacts of short-time scale water column variability on acoustic wave propagation include coherent and incoherent surface reflections, wavefront arrival time delay, focusing or defocusing of the intensity of acoustic beams and refraction of acoustic rays. This study focuses on high-frequency broadband acoustic waves, and examines the influence of short-time scale water column variability on broadband high-frequency acoustics, wavefronts, from 7 to 28 kHz, in shallow water. Short-time scale variability is on the order of seconds to hours and the short-spatial scale variability is on the order of few centimeters. Experimental results were collected during an acoustic experiment along 100 m isobaths and data analysis was conducted using available acoustic wave propagation models. Three main topics are studied to show that acoustic waves are viable as a remote sensing tool to measure oceanographic parameters in shallow water. First, coherent surface reflections forming striation patterns, from multipath receptions, through rough surface interaction of broadband acoustic signals with the dynamic sea surface are analyzed. Matched filtered results of received acoustic waves are compared with a ray tracing numerical model using a sea surface boundary generated from measured water wave spectra at the time of signal propagation. It is determined that on a time scale of seconds, corresponding to typical periods of surface water waves, the arrival time of reflected acoustic signals from surface waves appear as striation patterns in measured data and can be accurately modelled by ray tracing. Second, changes in acoustic beam arrival angle and acoustic ray path influenced by isotherm depth oscillations are analyzed using an 8-element delay-sum beamformer. The results are compared with outputs from a two-dimensional (2-D) parabolic equation (PE) model using measured sound speed profiles (SSPs) in the water column. Using the method of beamforming on the received signal, the arrival time and angle of an acoustic beam was obtained for measured acoustic signals. It is determined that the acoustic ray path, acoustic beam intensity and angular spread are a function of vertical isotherm oscillations on a time scale of minutes and can be modeled accurately by a 2-D PE model. Third, a forward problem is introduced which uses acoustic wavefronts received on a vertical line array, 1.48 km from the source, in the lower part of the water column to infer range dependence or independence in the SSP. The matched filtering results of received acoustic wavefronts at all hydrophone depths are compared with a ray tracing routine augmented to calculate only direct path and bottom reflected signals. It is determined that the SSP range dependence can be inferred on a time scale of hours using an array of hydrophones spanning the water column. Sound speed profiles in the acoustic field were found to be range independent for 11 of the 23 hours in the measurements. A SSP cumulative reconstruction process, conducted from the seafloor to the sea surface, layer-by-layer, identifies critical segments in the SSP that define the ray path, arrival time and boundary interactions. Data-model comparison between matched filtered arrival time spread and arrival time output from the ray tracing was robust when the SSP measured at the receiver was input to the model. When the SSP measured nearest the source (at the same instant in time) was input to the ray tracing model, the data-model comparison was poor. It was determined that the cumulative sound speed change in the SSP near the source was 1.041 m/s greater than that of the SSP at the receiver and resulted in the poor data-model comparison. In this study, the influences on broadband acoustic wave propagation in the frequency range of 7 to 28 kHz of spatial and temporal changes in the oceanography of shallow water regions are addressed. Acoustic waves can be used as remote sensing tools to measure oceanographic parameters in shallow water and data-model comparison results show a direct relationship between the oceanographic variations and acoustic wave propagations.

Incident wave, infragravity wave, and non-linear low-frequency bore evolution across fringing coral reefs

NASA Astrophysics Data System (ADS)

Storlazzi, C. D.; Griffioen, D.; Cheriton, O. M.

2016-12-01

Coral reefs have been shown to significantly attenuate incident wave energy and thus provide protection for 100s of millions of people globally. To better constrain wave dynamics and wave-driven water levels over fringing coral reefs, a 4-month deployment of wave and tide gauges was conducted across two shore-normal transects on Roi-Namur Island and two transects on Kwajalein Island in the Republic of the Marshall Islands. At all locations, although incident wave (periods <25 s) heights were an order of magnitude greater than infragravity wave (periods > 250 s) heights on the outer reef flat just inshore of the zone of wave breaking, the infragravity wave heights generally equaled the incident wave heights by the middle of the reef flat and exceeded the incident wave heights on the inner reef flat by the shoreline. The infragravity waves generally were asymmetric, positively skewed, bore-like forms with incident-band waves riding the infragravity wave crest at the head of the bore; these wave packets have similar structure to high-frequency internal waves on an internal wave bore. Bore height was shown to scale with water depth, offshore wave height, and offshore wave period. For a given tidal elevation, with increasing offshore wave heights, such bores occurred more frequently on the middle reef flat, whereas they occurred less frequently on the inner reef flat. Skewed, asymmetric waves are known to drive large gradients in velocity and shear stress that can transport material onshore. Thus, a better understanding of these low-frequency, energetic bores on reef flats is critical to forecasting how coral reef-lined coasts may respond to sea-level rise and climate change.

A Variational Reduction and the Existence of a Fully Localised Solitary Wave for the Three-Dimensional Water-Wave Problem with Weak Surface Tension

NASA Astrophysics Data System (ADS)

Buffoni, Boris; Groves, Mark D.; Wahlén, Erik

2017-12-01

Fully localised solitary waves are travelling-wave solutions of the three- dimensional gravity-capillary water wave problem which decay to zero in every horizontal spatial direction. Their existence has been predicted on the basis of numerical simulations and model equations (in which context they are usually referred to as `lumps'), and a mathematically rigorous existence theory for strong surface tension (Bond number {β} greater than {1/3} ) has recently been given. In this article we present an existence theory for the physically more realistic case {0 < β < 1/3} . A classical variational principle for fully localised solitary waves is reduced to a locally equivalent variational principle featuring a perturbation of the functional associated with the Davey-Stewartson equation. A nontrivial critical point of the reduced functional is found by minimising it over its natural constraint set.

A Variational Reduction and the Existence of a Fully Localised Solitary Wave for the Three-Dimensional Water-Wave Problem with Weak Surface Tension

NASA Astrophysics Data System (ADS)

Buffoni, Boris; Groves, Mark D.; Wahlén, Erik

2018-06-01

Fully localised solitary waves are travelling-wave solutions of the three- dimensional gravity-capillary water wave problem which decay to zero in every horizontal spatial direction. Their existence has been predicted on the basis of numerical simulations and model equations (in which context they are usually referred to as `lumps'), and a mathematically rigorous existence theory for strong surface tension (Bond number {β} greater than {1/3}) has recently been given. In this article we present an existence theory for the physically more realistic case {0 < β < 1/3}. A classical variational principle for fully localised solitary waves is reduced to a locally equivalent variational principle featuring a perturbation of the functional associated with the Davey-Stewartson equation. A nontrivial critical point of the reduced functional is found by minimising it over its natural constraint set.

Ultrasound Algorithm Derivation for Soil Moisture Content Estimation

NASA Technical Reports Server (NTRS)

Belisle, W.R.; Metzl, R.; Choi, J.; Aggarwal, M. D.; Coleman, T.

1997-01-01

Soil moisture content can be estimated by evaluating the velocity at which sound waves travel through a known volume of solid material. This research involved the development of three soil algorithms relating the moisture content to the velocity at which sound waves moved through dry and moist media. Pressure and shear wave propagation equations were used in conjunction with soil property descriptions to derive algorithms appropriate for describing the effects of moisture content variation on the velocity of sound waves in soils with and without complete soil pore water volumes, An elementary algorithm was used to estimate soil moisture contents ranging from 0.08 g/g to 0.5 g/g from sound wave velocities ranging from 526 m/s to 664 m/s. Secondary algorithms were also used to estimate soil moisture content from sound wave velocities through soils with pores that were filled predominantly with air or water.

The meteorite impact-induced tsunami hazard.

PubMed

Wünnemann, K; Weiss, R

2015-10-28

When a cosmic object strikes the Earth, it most probably falls into an ocean. Depending on the impact energy and the depth of the ocean, a large amount of water is displaced, forming a temporary crater in the water column. Large tsunami-like waves originate from the collapse of the cavity in the water and the ejecta splash. Because of the far-reaching destructive consequences of such waves, an oceanic impact has been suggested to be more severe than a similar-sized impact on land; in other words, oceanic impacts may punch over their weight. This review paper summarizes the process of impact-induced wave generation and subsequent propagation, whether the wave characteristic differs from tsunamis generated by other classical mechanisms, and what methods have been applied to quantify the consequences of an oceanic impact. Finally, the impact-induced tsunami hazard will be evaluated by means of the Eltanin impact event. © 2015 The Author(s).

Abyssal Upwelling in Mid-Ocean Ridge Fracture Zones

NASA Astrophysics Data System (ADS)

Clément, Louis; Thurnherr, Andreas M.

2018-03-01

Turbulence in the abyssal ocean plays a fundamental role in the climate system by sustaining the deepest branch of the overturning circulation. Over the western flank of the Mid-Atlantic Ridge in the South Atlantic, previously observed bottom-intensified and tidally modulated mixing of abyssal waters appears to imply a counterintuitive densification of deep and bottom waters. Here we show that inside fracture zones, however, turbulence is elevated away from the seafloor because of intensified downward propagating near-inertial wave energy, which decays below a subinertial shear maximum. Ray-tracing simulations predict a decay of wave energy subsequent to wave-mean flow interactions. The hypothesized wave-mean flow interactions drive a deep flow toward lighter densities of up to 0.6 Sv over the mid-ocean ridge flank in the Brazil Basin, and the same process may also cause upwelling of abyssal waters in other ocean basins with mid-ocean ridges with fracture zones.

Analysis of the high water wave volume for the Sava River near Zagreb

NASA Astrophysics Data System (ADS)

Trninic, Dusan

2010-05-01

The paper analyses volumes of the Sava River high water waves near Zagreb during the period: 1926-2008 (N = 83 years), which is needed for more efficient control of high and flood waters. The primary Sava flood control structures in the City of Zagreb are dikes built on both riverbanks, and the Odra Relief Canal with lateral spillway upstream from the City of Zagreb. Intensive morphological changes in the greater Sava area near Zagreb, and anthropological and climate variations and changes at the Sava catchment up to the Zagreb area require detailed analysis of the water wave characteristics. In one analysis, maximum annual volumes are calculated for high water waves with constant duration of: 10, 20, 30, 40, 50 and 60 days. Such calculations encompass total quantity of water (basic and surface runoff). The log Pearson III distribution is adapted for this series of maximum annual volumes. Based on the results obtained, the interrelations are established between the wave volume as function of duration and occurrence probability. In addition to the analysis of maximum volumes of constant duration, it is interesting to carry out the analyses of maximum volume in excess of the reference discharge since it is very important for the flood control. To determine the reference discharges, a discharge of specific duration is used from an average discharge duration curve. The adopted reference discharges have durations of 50, 40, 30, 20 and 10%. Like in the previous case, log Pearson III distribution is adapted to the maximum wave data series. For reference discharge Q = 604 m3/s (duration 10%), a linear trend is calculated of maximum annual volumes exceeding the reference discharge for the Sava near Zagreb during the analyzed period. The analysis results show a significant decrease trend. A similar analysis is carried out for the following three reference discharges: regular flood control measures at the Sava near Zagreb, which are proclaimed when the water level is 350 cm (Q = 2114 m3/s), extraordinary flood control measures taken when the water level is 450 cm (Q = 2648 m3/s), and the discharge at the deterministic inlet into the Odra Canal of approximately Q = 2300 m3/s. The results of these analyses have shown that water wave volumes higher than the reference discharges occurred in a comparatively small number of years, and that their duration was one to two days.

Changes in crack shape and saturation during water penetration into stressed rock

NASA Astrophysics Data System (ADS)

Masuda, K.; Nishizawa, O.

2012-12-01

Open cracks and cavities in rocks play important roles in fluid transport. Water penetration induced microcrack activities and caused the failure of rocks. Fluids in cracks affect earthquake generation mechanism through physical and physicochemical effects. Methods of characterizing crack shape and water saturation of rocks underground are needed for many scientific and industrial applications. It would be desirable to estimate the status of cracks using readily observable data such as elastic-wave velocities. We demonstrate a laboratory method for estimating crack status inside a cylindrical rock sample based on least-squares fitting of a cracked solid model to measured P- and S-wave velocities, and porosity derived from strain data. We used a cylinder (50 mm in diameter and 100 mm in length) of medium-grained granite. We applied a differential stress of 370 MPa, which corresponds to about 70% of fracture strength, to the rock sample under 30 MPa confining pressure and held it constant throughout the experiment. When the primary creep stage and acoustic emission (AE) caused by the initial loading had ceased, we injected distilled water into the bottom end of the sample at a constant pressure of 25 MPa until macroscopic fracture occurred. During water migration, we measured P waves and S waves (Sv and Sh), in five directions parallel to the top and bottom surfaces of the sample. We also measured strains of the sample surface and monitored AE. We created X-ray computer tomography (CT) images of the rock sample after the experiment in order to recognize the location and shape of fractured surfaces. We observed the different patterns of velocity changes in the upper and lower portions of the rock sample. Changes in P-wave velocities can be interpreted based on the crack density. S-waves showed the splitting with Vsv being faster than Vsh, corresponding to the second kind of anisotropy. We estimated two crack characteristics, crack shape and the degree of water saturation, and their changes during the loading and water migration into a granitic rock subjected to confining pressure and differential stress. We found that during injection of water to induce failure of a stressed rock sample, the aspect ratio of cracks increased and the degree of water saturation increased to about 70%. Laboratory derived method can be applicable for the well-planned observation in the field experiments. Monitoring in situ crack situations with seismic waves are useful for industrial and scientific applications such as sequestrations of carbon dioxide and waste, and measuring the regional stress field.

Molding acoustic, electromagnetic and water waves with a single cloak

PubMed Central

Xu, Jun; Jiang, Xu; Fang, Nicholas; Georget, Elodie; Abdeddaim, Redha; Geffrin, Jean-Michel; Farhat, Mohamed; Sabouroux, Pierre; Enoch, Stefan; Guenneau, Sébastien

2015-01-01

We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves. PMID:26057934

Water-waves on linear shear currents. A comparison of experimental and numerical results.

NASA Astrophysics Data System (ADS)

Simon, Bruno; Seez, William; Touboul, Julien; Rey, Vincent; Abid, Malek; Kharif, Christian

2016-04-01

Propagation of water waves can be described for uniformly sheared current conditions. Indeed, some mathematical simplifications remain applicable in the study of waves whether there is no current or a linearly sheared current. However, the widespread use of mathematical wave theories including shear has rarely been backed by experimental studies of such flows. New experimental and numerical methods were both recently developed to study wave current interactions for constant vorticity. On one hand, the numerical code can simulate, in two dimensions, arbitrary non-linear waves. On the other hand, the experimental methods can be used to generate waves with various shear conditions. Taking advantage of the simplicity of the experimental protocol and versatility of the numerical code, comparisons between experimental and numerical data are discussed and compared with linear theory for validation of the methods. ACKNOWLEDGEMENTS The DGA (Direction Générale de l'Armement, France) is acknowledged for its financial support through the ANR grant N° ANR-13-ASTR-0007.

Solitary wave runup and force on a vertical barrier

NASA Astrophysics Data System (ADS)

Liu, Philip L.-F.; Al-Banaa, Khaled

2004-04-01

In this paper we investigate the interaction between a solitary wave and a thin vertical barrier. A set of laboratory experiments was performed with different values of incident wave height to water depth ratio, H/h, and the draught of the barrier to water depth ratio, D/h. While wave gauges were used to measure the reflected and transmitted waves, pressure transducers were installed on both sides of the barrier, enabling the calculation of wave force. The particle image velocimetry (PIV) technique is also employed to measure the velocity field in the vicinity of the barrier. A numerical model, based on the Reynolds-averaged Navier Stokes (RANS) equations and the k - epsilon turbulence closure model, was first checked with experimental data and then employed to obtain additional results for the range of parameters where the laboratory experiments were not performed. Using both experimental data and numerical results, formulae for the maximum runup height, and the maximum wave force are derived in terms of H/h and D/h.

Molding acoustic, electromagnetic and water waves with a single cloak.

PubMed

Xu, Jun; Jiang, Xu; Fang, Nicholas; Georget, Elodie; Abdeddaim, Redha; Geffrin, Jean-Michel; Farhat, Mohamed; Sabouroux, Pierre; Enoch, Stefan; Guenneau, Sébastien

2015-06-09

We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves.

Embedded optical fibers for PDV measurements in shock-loaded, light and heavy water

NASA Astrophysics Data System (ADS)

Mercier, Patrick; Benier, Jacky; Frugier, Pierre Antoine; Debruyne, Michel; Bolis, Cyril

2012-03-01

In order to study the shock-detonation transition, we propose to characterize the shock loading of a high explosive plane wave generator into a nitromethane cell. To eliminate the reactive behaviour, we replace the nitromethane by an inert liquid compound. Light water (H2O) has been first employed; eventually heavy water (D2O) has been chosen for its better infrared spectral properties. We present the PDV results of different embedded optical fibers which sense the medium with two different approaches: a non intrusive optical observation of phenomena coming in front of them (interface, shock wave, detonation wave) followed by their mechanical interaction with the fiber.

Negative refraction of acoustic waves using a foam-like metallic structure

NASA Astrophysics Data System (ADS)

Hladky-Hennion, A.-C.; Vasseur, J. O.; Haw, G.; Croënne, C.; Haumesser, L.; Norris, A. N.

2013-04-01

A phononic crystal (PC) slab made of a single metallic phase is shown, theoretically and experimentally, to display perfect negative index matching and focusing capability when surrounded with water. The proposed PC slab is a centimeter scale hollow metallic foam-like structure in which acoustic energy is mediated via the metal lattice. The negative index property arises from an isolated branch of the dispersion curves corresponding to a mode that can be coupled to incident acoustic waves in surrounding water. This band also intercepts the water sound line at a frequency in the ultrasonic range. The metallic structure is consequently a candidate for the negative refraction of incident longitudinal waves.

Monochromatic body waves excited by great subduction zone earthquakes

NASA Astrophysics Data System (ADS)

Ihmlé, Pierre F.; Madariaga, Raúl

Large quasi-monochromatic body waves were excited by the 1995 Chile Mw=8.1 and by the 1994 Kurile Mw=8.3 events. They are observed on vertical/radial component seismograms following the direct P and Pdiff arrivals, at all azimuths. We devise a slant stack algorithm to characterize the source of the oscillations. This technique aims at locating near-source isotropic scatterers using broadband data from global networks. For both events, we find that the oscillations emanate from the trench. We show that these monochromatic waves are due to localized oscillations of the water column. Their period corresponds to the gravest ID mode of a water layer for vertically traveling compressional waves. We suggest that these monochromatic body waves may yield additional constraints on the source process of great subduction zone earthquakes.

Experimental study on waves propagation over a coarse-grained sloping beach

NASA Astrophysics Data System (ADS)

Hsu, Tai-Wen; Lai, Jian-Wu

2013-04-01

This study investigates velocity fields of wave propagation over a coarse-grained sloping beach using laboratory experiments. The experiment was conducted in a wave flume of 25 m long, 0.5 m wide and 0.6 m high in which a coarse-grained sloping 1:5 beach was placed with two layers ball. The glass ball is D=7.9 cm and the center to center distance of each ball is 8.0 cm. The test section for observing wave and flow fields is located at the middle part of the flume. A piston type wave maker driven by an electromechanical hydraulic serve system is installed at the end of the flume. The intrinsic permeability Kp and turbulent drag coefficient Cf were obtained from steady flow water-head experiments. The flow velocity was measured by the particle image velocimeter (PIV) and digital image process (DIP) techniques. Eleven fields of view (FOVS) were integrated into a complete representation including the outer, surf and swash zone. Details of the definition sketch of the coarse-grained sloping beach model as well as experimental setup are referred to Lai et al. (2008). A high resolution of CCD camera was used to capture the images which was calibrated by the direct linear transform (DCT) algorithm proposed by Abed El-Aziz and Kar-Ara (1971). The water surface between the interface of air and water at each time step are calculated by Otsu' (1978) detect algorithm. The comparison shows that the water surface elevation observed by integrated image agrees well with that of Otsu' detection results. For the flow field measurement, each image pair was cross correlated with 32X32 pixel inter rogation window and a half overlap between adjacent windows. The repeatability and synchronization are the key elements for both wave motion and PIV technique. The wave profiles and flow field were compared during several wave periods to ensure that they can be reproduced by the present system. The water depth is kept as a constant of h=32 cm. The incident wave conditions are set to be wave height H0 = 3.86 cm or 7.75 cm and wave period T = 1.0 s. The illumination source of the PIV system is a dual-head frequency-doubled Nd:YAG laser, which has a maximum energy output of 120 mJ per pulse at two wavelengths of 523nm and 266nm. A synchronizer controls the emission time of a pulse laser beam as well as the camera exposure and shutter time. Linear wave theory (LWT) of wave propagation over a constant water depth was tested to validate the DIP/PIV algorithm. The comparison of velocity profiles in X and Z directions are in good agreement with those of LWT. Waves propagating over a coarse-grained sloping beach were investigated using PIV/DIP techniques. Detailed analysis of experimental results show that the flow field, turbulent intensity and vorticity are primarily located above the wave trough. A detailed description is provided in terms of free surface, velocity field, and turbulent energy transport. References 1. Abdel-Aziz, Karara.1971, Direct linear transformation into object space coordinates in closerange photogrametry. In Proc. Symp. Close-Range Photogrametry, 1-18. 2. Flow-3D (2008) user manual, version 9.3. 3. Otsu N. 1978. A threshold selection method from gray level histogram, IEEE Trans. on System, Man, and Cybernetics, 8, 62-66.

Many atolls may be uninhabitable within decades due to climate change

USGS Publications Warehouse

Storlazzi, Curt; Elias, Edwin P.L.; Berkowitz, Paul

2015-01-01

Observations show global sea level is rising due to climate change, with the highest rates in the tropical Pacific Ocean where many of the world’s low-lying atolls are located. Sea-level rise is particularly critical for low-lying carbonate reef-lined atoll islands; these islands have limited land and water available for human habitation, water and food sources, and ecosystems that are vulnerable to inundation from sea-level rise. Here we demonstrate that sea-level rise will result in larger waves and higher wave-driven water levels along atoll islands’ shorelines than at present. Numerical model results reveal waves will synergistically interact with sea-level rise, causing twice as much land forecast to be flooded for a given value of sea-level rise than currently predicted by current models that do not take wave-driven water levels into account. Atolls with islands close to the shallow reef crest are more likely to be subjected to greater wave-induced run-up and flooding due to sea-level rise than those with deeper reef crests farther from the islands’ shorelines. It appears that many atoll islands will be flooded annually, salinizing the limited freshwater resources and thus likely forcing inhabitants to abandon their islands in decades, not centuries, as previously thought.

Liquefaction, ground oscillation, and soil deformation at the Wildlife Array, California

USGS Publications Warehouse

Holzer, T.L.; Youd, T.L.

2007-01-01

Excess pore-water pressure and liquefaction at the Wildlife Liquefaction Array in 1987 were caused by deformation associated with both high-frequency strong ground motion and 5.5-second-period Love waves. The Love waves produced large (???1.5%) cyclic shear strains well after the stronger high-frequency ground motion abated. These cyclic strains generated approximately from 13 to 35% of the excess pore-water pressure in the liquefied layer and caused excess pore-water pressures ultimately to reach effective overburden stress. The deformation associated with the Love waves explains the "postearthquake" increase of pore-water pressure that was recorded at the array. This explanation suggests that conventional methods for predicting liquefaction based on peak ground acceleration are incomplete and may need to consider cyclic strains associated with long-period surface waves. A post-earthquake survey of an inclinometer casing indicated permanent shear strain associated with lateral spreading primarily occurred in the upper part of the liquefied layer. Comparison of cone penetration test soundings conducted after the earthquake with pre-earthquake soundings suggests sleeve friction increased. Natural lateral variability of the liquefied layer obscured changes in tip resistance despite a ???1% reduction in volume. The large oscillatory motion associated with surface waves explains ground oscillation that has been reported at some liquefaction sites during earthquakes.

Laboratory tests of short intense envelope solitons

NASA Astrophysics Data System (ADS)

Slunyaev, A.; Clauss, G. F.; Klein, M.; Onorato, M.

2012-04-01

Stability of short intense nonlinear wave groups propagating over deep water is tested in laboratory runs which are performed in the facility of the Technical University of Berlin. The strongly nonlinear simulation of quasi-steady nonlinear wave groups within the framework of the Euler equations is used to generate the surface elevation time series at a border of the water tank. Besides, the exact analytic solution of the nonlinear Schrodinger equation is used for this purpose. The time series is then transformed to a wave maker signal with use of a designed transfer algorithm. Wave group propagation along the tank was recorded by 4 distant gauges and by an array of 6 densely situated gauges. This setup allows to consider the wave evolution from 10 to 85 m from the wave maker, and to obtain the wave envelope shape directly from the instrumental data. In the experiments wave groups were characterized by the steepness values up to kAcr < 0.32 and kAtr < 0.24, where k is the mean wavenumber, Acr is the crest amplitude, and Atr is the trough amplitude; and the maximum local wave slope was up to 0.34. Wave breaking phenomenon was not observed in the experiments. Different mean wave numbers and wave groups of different intensities were considered. In some cases the wave groups exhibit noticeable radiation in the course of propagation, though the groups are not dispersed fully. The effect of finite water depth is found to be significant on the wave group stability. Intense wave groups have shorter time of adjustment, what in some sense may help them to manifest their individuality clearer. The experimental tests confirm recent numerical simulations of fully nonlinear equations, where very steep stable single and interacting nonlinear wave groups were reported [1-3]. The quasi-stationary wave groups observed in numerical and laboratory experiments are strongly nonlinear analogues of the nonlinear Schrodinger envelope solitons. The results emphasize the importance of long-living nonlinear wave groups in dynamics of intense sea waves. [1] V.E. Zakharov, A.I. Dyachenko, A.O. Prokofiev, Eur. J. Mech. B / Fluids 25, 677 (2006). [2] A.I. Dyachenko, V.E. Zakharov, JETP Lett. 88, 307 (2008). [3] A.V. Slunyaev, JETP 109, 676 (2009).

Secondary Flows and Sediment Transport due to Wave - Current Interaction

NASA Astrophysics Data System (ADS)

Ismail, Nabil; Wiegel, Robert

2015-04-01

Objectives: The main purpose of this study is to determine the modifications of coastal processes driven by wave-current interaction and thus to confirm hydrodynamic mechanisms associated with the interaction at river mouths and tidal inlets where anthropogenic impacts were introduced. Further, the aim of the work has been to characterize the effect of the relative strength of momentum action of waves to the opposing current on the nearshore circulation where river flow was previously effective to entrain sediments along the shoreline. Such analytical information are useful to provide guidelines for sustainable design of coastal defense structures. Methodology and Analysis: Use is made of an earlier study reported by the authors (1983) on the interaction of horizontal momentum jets and opposing shallow water waves at shorelines, and of an unpublished laboratory study (1980). The turbulent horizontal discharge was shore-normal, directed offshore, and the incident wave direction was shore-normal, travelling toward shore. Flow visualization at the smooth bottom and the water surface, velocity and water surface elevation measurements were made. Results were obtained for wave , current modifications as well as the flow pattern in the jet and the induced circulation on both sides of the jet, for a range of wave and jet characteristics. The experimental data, obtained from measurement in the 3-D laboratory basin, showed several distinct flow pattern regimes on the bottom and the water surface. The observed flow circulation regimes were found to depend on the ratio of the wave momentum action on the jet to the jet initial momentum. Based on the time and length scales of wave and current parameters and using the time average of the depth integrated conservation equations, it is found that the relative strength of the wave action on the jet could be represented by a dimensionless expression; Rsm ( ) 12ρSa20g-L0h-Cg- 2 Rsm ≈ (C0 - U) /ρ0U w (1) In the above dimensionless expression, ρs is the seawater mass density, ρ is the river current mass density, a0 is the deep water wave amplitude, g is the acceleration of gravity, Cg is the wave group velocity, L is the deep water wave length, h is the average water depth near the river mouth, C0 is the deep water wave phase velocity, U is the average jet exit velocity and w is the river or the tidal inlet effective width. The values of the above number were found to be in the range between 1.0 and 6.0-8.0 for the examined laboratory and field case studies for non-buoyant jets. Upper bound corresponds to cases of higher wave activity on the coast while the lower bound corresponds to cases of tidal currents with minimum wave activity, Coastal Processes Modifications due to River and Ebb Current Interaction with Opposing Waves: Confirmation of the obtained theoretical expression was obtained by comparison against field data for shoreline variability at river mouths and the formation of accretion shoals and erosion spots at tidal inlets and ocean outfalls in the USA and the Nile delta coastline. The predicted extent of the coast reshaping process, due to shoreline erosion and subsequent accretion, due to the absence of the river Nile current after 1965, east of the Rosetta headland, was determined. The obtained shoreline erosion spatial extent using the above correlation showed that the long term length of coastline recession would be in the neighborhood of 16-20 km east of Rosetta headland (1990-2014). Such results were further confirmed by the recent satellite data (Ghoneim, et al, 2015). The results of the present work were well compared to the data on Fort Pierce Inlet, Florida, where severe erosion is known to exist on both sides of the inlet (Joshi, 1983). The current results are qualitatively in parallel to that obtained recently by the numerical model Delft3D coupled with the wave model SWAN ( Nardin, et al, 2013) on wave- current interaction at river mouths and the formation of mouth bars. Further analyses were also conducted to test the validity of the derived expression to the cases of wave interaction with buoyant currents in shallow waters. The buoyant jets represent the thermal discharges from power plants on coastlines of Diablo Canyon cove in CA at the Pacific Ocean (Ismail, et al,1988) and at the northern coast of Egypt at Al-Arish. The comparison showed higher values range of Rsm for the cases of buoyant jets. References: Ghoneim, E., Mashaly , J., Gamble, D., Halls, J., and AbuBakr, M. (2015). "Nile Delta Exhibited a Spatial Reversal in the Rates of Shoreline Retreat on the Rosetta Promontory; comparing pre- and post-beach protection", Geomorphology, 228,1-14. Ismail, N. (2007). "Reynolds Stresses and Velocity Distributions in a Wave-Current Coexisting Environment', Discussion, J. Waterway, Port, Coastal, and Ocean Engineering,10.1061/(ASCE)0733-950X(2007)133:2(168),168-170. Ismail, N.M., Wiegel, R.L., Ryan, P.J., and Tu, S. W. (1988). "Mixing of Thermal Discharges in Coastal Waters" , 21 st International Conference on Coastal Engineering, ASCE, Malaga, Spain, 2521-2535. Ismail, N. (1984). "Wave-Current Models for Design of Marine Structures" , Journal of Waterway, Port, Coastal and Ocean Engineering, Vol. 110, No. 4, 432-447. Ismail, N.M. and Wiegel, R.L. (1983). "Opposing Waves Effect on Momentum Jets Spreading Rate", J. Waterways, Port, Coastal and Ocean Division, Proc., ASCE, vol. 109, No.4, 465-483. Joshi, P. and Taylor, R. (1983). 'Circulation Induced by Tidal Jets.' J. Waterway, Port, Coastal, Ocean Eng., 109(4), 445-464. Nardin, W., Mariotti, G., Edmonds, D., Guercio, R., and Fagherazzi, S. (2013). "Growth of River Mouth Bars in Sheltered Bays in the Presence of Frontal Waves." Journal of Geophysical Research: Earth Surface,10, 872-886.

Wave Propagation and Inversion in Shallow Water and Poro-elastic Sediment

DTIC Science & Technology

1997-09-30

water and high freq. acoustics LONG-TERM GOALS To create codes accurately model wave propagation and scattering in shallow water, and to quantify...is undergoing testing for the acoustic stratified Green’s function. We have adapted code generated by J. Schuster in Geophysics for the FDTD model ...inversions and modelling , and have repercussions in environmental imaging [5], acoustic imaging [1,4,5,6,7] and early breast cancer diagnosis

Wave Tank Studies of Phase Velocities of Short Wind Waves

NASA Astrophysics Data System (ADS)

Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

Wave tank studies of phase velocities of short wind waves have been carried out using Ka-band radar and an Optical Spectrum Analyser. The phase velocities were retrieved from measured radar and optical Doppler shifts, taking into account measurements of surface drift velocities. The dispersion relationship was studied in centimetre (cm)- and millimetre(mm)-scale wavelength ranges at different fetches and wind speeds, both for a clean water surface and for water covered with surfactant films. It is ob- tained that the phase velocities do not follow the dispersion relation of linear capillary- gravity waves, increasing with fetch and, therefore, depending on phase velocities of dominant decimetre (dm)-centimetre-scale wind waves. One thus can conclude that nonlinear cm-mm-scale harmonics bound to the dominant wind waves and propagat- ing with the phase velocities of the decimetric waves are present in the wind wave spectrum. The resulting phase velocities of short wind waves are determined by re- lation between free and bound waves. The relative intensity of the bound waves in the spectrum of short wind waves is estimated. It is shown that this relation depends strongly on the surfactant concentration, because the damping effect due to films is different for free and bound waves; this results to changes of phase velocities of wind waves in the presence of surfactant films. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

Using Kinect to Measure Wave Spectrum

NASA Astrophysics Data System (ADS)

Fong, J.; Loose, B.; Lovely, A.

2012-12-01

Gas exchange at the air-sea interface is enhanced by aqueous turbulence generated by capillary-gravity waves, affecting the absorption of atmospheric carbon dioxide by the ocean. The mean squared wave slope of these waves correlates strongly with the gas transfer velocity. To measure the energy in capillary-gravity waves, this project aims to use the Microsoft Xbox Kinect to measure the short period wave spectrum. Kinect is an input device for the Xbox 360 with an infrared laser and camera that can be used to map objects at high frequency and spatial resolution, similar to a LiDAR sensor. For air-sea gas exchange, we are interested in the short period gravity waves with a wavenumber of 40 to 100 radians per meter. We have successfully recorded data from Kinect at a sample rate of 30 Hz with 640x480 pixel resolution, consistent with the manufacturer specifications for its scanning capabilities. At 0.5 m distance from the surface, this yields a nominal resolution of approximately 0.7 mm with a theoretical vertical precision of 0.24 mm and a practical 1 σ noise level of 0.91 mm. We have found that Kinect has some limitations in its ability to detect the air-water interface. Clean water proved to be a weaker reflector for the Kinect IR source, whereas a relatively strong signal can be received for liquids with a high concentration of suspended solids. Colloids such as milk and Ca(OH)2 in water proved more suitable media from which height and wave spectra were detectable. Moreover, we will show results from monochromatic as well as wind-wave laboratory studies. With the wave field measurements from Kinect, gas transfer velocities at the air-sea interface can be determined.

An Eulerian two-phase flow model for sediment transport under realistic surface waves

NASA Astrophysics Data System (ADS)

Hsu, T. J.; Kim, Y.; Cheng, Z.; Chauchat, J.

2017-12-01

Wave-driven sediment transport is of major importance in driving beach morphology. However, the complex mechanisms associated with unsteadiness, free-surface effects, and wave-breaking turbulence have not been fully understood. Particularly, most existing models for sediment transport adopt bottom boundary layer approximation that mimics the flow condition in oscillating water tunnel (U-tube). However, it is well-known that there are key differences in sediment transport when comparing to large wave flume datasets, although the number of wave flume experiments are relatively limited regardless of its importance. Thus, a numerical model which can resolve the entire water column from the bottom boundary layer to the free surface can be a powerful tool. This study reports an on-going effort to better understand and quantify sediment transport under shoaling and breaking surface waves through the creation of open-source numerical models in the OpenFOAM framework. An Eulerian two-phase flow model, SedFoam (Cheng et al., 2017, Coastal Eng.) is fully coupled with a volume-of-fluid solver, interFoam/waves2Foam (Jacobsen et al., 2011, Int. J. Num. Fluid). The fully coupled model, named SedWaveFoam, regards the air and water phases as two immiscible fluids with the interfaces evolution resolved, and the sediment particles as dispersed phase. We carried out model-data comparisons with the large wave flume sheet flow data for nonbreaking waves reported by Dohmen-Janssen and Hanes (2002, J. Geophysical Res.) and good agreements were obtained for sediment concentration and net transport rate. By further simulating a case without free-surface (mimic U-tube condition), the effects of free-surface, most notably the boundary layer streaming effect on total transport, can be quantified.

Nonlinear water waves: introduction and overview

NASA Astrophysics Data System (ADS)

Constantin, A.

2017-12-01

For more than two centuries progress in the study of water waves proved to be interdependent with innovative and deep developments in theoretical and experimental directions of investigation. In recent years, considerable progress has been achieved towards the understanding of waves of large amplitude. Within this setting one cannot rely on linear theory as nonlinearity becomes an essential feature. Various analytic methods have been developed and adapted to come to terms with the challenges encountered in settings where approximations (such as those provided by linear or weakly nonlinear theory) are ineffective. Without relying on simpler models, progress becomes contingent upon the discovery of structural properties, the exploitation of which requires a combination of creative ideas and state-of-the-art technical tools. The successful quest for structure often reveals unexpected patterns and confers aesthetic value on some of these studies. The topics covered in this issue are both multi-disciplinary and interdisciplinary: there is a strong interplay between mathematical analysis, numerical computation and experimental/field data, interacting with each other via mutual stimulation and feedback. This theme issue reflects some of the new important developments that were discussed during the programme `Nonlinear water waves' that took place at the Isaac Newton Institute for Mathematical Sciences (Cambridge, UK) from 31st July to 25th August 2017. A cross-section of the experts in the study of water waves who participated in the programme authored the collected papers. These papers illustrate the diversity, intensity and interconnectivity of the current research activity in this area. They offer new insight, present emerging theoretical methodologies and computational approaches, and describe sophisticated experimental results. This article is part of the theme issue 'Nonlinear water waves'.

Nonlinear water waves: introduction and overview.

PubMed

Constantin, A

2018-01-28

For more than two centuries progress in the study of water waves proved to be interdependent with innovative and deep developments in theoretical and experimental directions of investigation. In recent years, considerable progress has been achieved towards the understanding of waves of large amplitude. Within this setting one cannot rely on linear theory as nonlinearity becomes an essential feature. Various analytic methods have been developed and adapted to come to terms with the challenges encountered in settings where approximations (such as those provided by linear or weakly nonlinear theory) are ineffective. Without relying on simpler models, progress becomes contingent upon the discovery of structural properties, the exploitation of which requires a combination of creative ideas and state-of-the-art technical tools. The successful quest for structure often reveals unexpected patterns and confers aesthetic value on some of these studies. The topics covered in this issue are both multi-disciplinary and interdisciplinary: there is a strong interplay between mathematical analysis, numerical computation and experimental/field data, interacting with each other via mutual stimulation and feedback. This theme issue reflects some of the new important developments that were discussed during the programme 'Nonlinear water waves' that took place at the Isaac Newton Institute for Mathematical Sciences (Cambridge, UK) from 31st July to 25th August 2017. A cross-section of the experts in the study of water waves who participated in the programme authored the collected papers. These papers illustrate the diversity, intensity and interconnectivity of the current research activity in this area. They offer new insight, present emerging theoretical methodologies and computational approaches, and describe sophisticated experimental results.This article is part of the theme issue 'Nonlinear water waves'. © 2017 The Author(s).

Lake St. Clair: Storm Wave and Water Level Modeling

DTIC Science & Technology

2013-06-01

R. A. Luettich, C. Dawson, V. J. Cardone , A. T. Cox, M. D. Powell, H. J. Westerink, and H. J. Roberts. 2010. A high resolution coupled riverine flow...Storm Wave and Water Level Modeling 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Tyler J. Hesser

Generation of shockwave and vortex structures at the outflow of a boiling water jet

NASA Astrophysics Data System (ADS)

Alekseev, M. V.; Lezhnin, S. I.; Pribaturin, N. A.; Sorokin, A. L.

2014-12-01

Results of numerical simulation for shock waves and generation of vortex structures during unsteady outflow of boiling liquid jet are presented. The features of evolution of shock waves and vortex structures formation during unsteady outflow of boiling water are compared with corresponding structures during unsteady gas outflow.

Performance of wave function and density functional methods for water hydrogen bond spin-spin coupling constants.

PubMed

García de la Vega, J M; Omar, S; San Fabián, J

2017-04-01

Spin-spin coupling constants in water monomer and dimer have been calculated using several wave function and density functional-based methods. CCSD, MCSCF, and SOPPA wave functions methods yield similar results, specially when an additive approach is used with the MCSCF. Several functionals have been used to analyze their performance with the Jacob's ladder and a set of functionals with different HF exchange were tested. Functionals with large HF exchange appropriately predict 1 J O H , 2 J H H and 2h J O O couplings, while 1h J O H is better calculated with functionals that include a reduced fraction of HF exchange. Accurate functionals for 1 J O H and 2 J H H have been tested in a tetramer water model. The hydrogen bond effects on these intramolecular couplings are additive when they are calculated by SOPPA(CCSD) wave function and DFT methods. Graphical Abstract Evaluation of the additive effect of the hydrogen bond on spin-spin coupling constants of water using WF and DFT methods.

Rockslide and Impulse Wave Modelling in the Vajont Reservoir by DEM-CFD Analyses

NASA Astrophysics Data System (ADS)

Zhao, T.; Utili, S.; Crosta, G. B.

2016-06-01

This paper investigates the generation of hydrodynamic water waves due to rockslides plunging into a water reservoir. Quasi-3D DEM analyses in plane strain by a coupled DEM-CFD code are adopted to simulate the rockslide from its onset to the impact with the still water and the subsequent generation of the wave. The employed numerical tools and upscaling of hydraulic properties allow predicting a physical response in broad agreement with the observations notwithstanding the assumptions and characteristics of the adopted methods. The results obtained by the DEM-CFD coupled approach are compared to those published in the literature and those presented by Crosta et al. (Landslide spreading, impulse waves and modelling of the Vajont rockslide. Rock mechanics, 2014) in a companion paper obtained through an ALE-FEM method. Analyses performed along two cross sections are representative of the limit conditions of the eastern and western slope sectors. The max rockslide average velocity and the water wave velocity reach ca. 22 and 20 m/s, respectively. The maximum computed run up amounts to ca. 120 and 170 m for the eastern and western lobe cross sections, respectively. These values are reasonably similar to those recorded during the event (i.e. ca. 130 and 190 m, respectively). Therefore, the overall study lays out a possible DEM-CFD framework for the modelling of the generation of the hydrodynamic wave due to the impact of a rapid moving rockslide or rock-debris avalanche.

Offshore Breaking of Impact Tsunami: Van Dorn was Right

NASA Technical Reports Server (NTRS)

Korycansky, D. G.; Lynett, P. J.

2005-01-01

Tsunami generated by the impacts of asteroids and comets into the Earth s oceans are widely recognized as a potentially catastrophic hazard to the Earth s population (e.g. Chapman and Morrison 1994, Nature, 367, 33; Hills et al. 1994, in Hazards Due to Comets and Asteroids, (ed. T. Gehrels), 779; Atkinson et al. 2000, Report of the UK Task Force on Potentially Hazardous NEOs; Ward and Asphaug 2000, Icarus, 145, 64). A peculiarity of ocean impacts is the potential global effects of an impact that would otherwise be of only regional or local importance should it occur on land. This is, of course, due to the ability of waves to propagate globally, as seen by the terrible effects of the recent earthquake off the coast of Sumatra. The overall process of an impact tsunami is complex and falls into several distinct phases: 1) initial impact of the bolide into the ocean and formation of a transient cavity in the water, 2) collapse of the cavity and propagation of large waves from the impact center outward over deep water (typically several km in depth), 3) initial effects on wave amplitude as shallower water of the continental slope is reached ("wave shoaling"), possible breaking of waves in relatively shallow water (less than 100 m depth), on continental shelves, and 5) final contact of waves with the shore and their progression onto dry land ("run-up" and "run-in"). Here we report on numerical calculations (and semi-analytic theory) covering phases 3 and 4.

Proceedings, Nonlinear Water Waves Workshop Held at the University of Bristol on October 22-25, 1991

DTIC Science & Technology

1991-01-01

far as I understand, you have studied the case of one -dimensional spectrum of waves. I think that taking into account non- one -dimensional triplets...2b Evolving shoi waves (T- 1.0s). 13 components even became larger than that of the primary wave itself. The short waves (ff= 1.0 Hz), on the...breaking waves. This allows one to study statistics of breaking waves as rare events of high level excursion by a (three-dimensional) field of the wave

Modeling Wind Wave Evolution from Deep to Shallow Water

DTIC Science & Technology

2012-09-30

WORK COMPLETED Development of a Lumped Quadruplet Approximation ( LQA ) A scalable parameterization of non-linear four-wave interactions is being...what we refer to as the Lumped Quadruplet Approximation ( LQA ), in which discrete contributions on the locus are treated as individual wave number...includes inhomogeneous wave fields, but is compatible with the action balance generally used in operational wave models. RESULTS Development LQA

Island-Trapped Waves, Internal Waves, and Island Circulation

DTIC Science & Technology

2014-09-30

from the government of Palau to allow us to deliver some water and food to the officers. Governor Patris of Hatohobei State and the Coral Reef ...Island-trapped waves , internal waves , and island circulation T. M. Shaun Johnston Scripps Institution of Oceanography University of California...large islands (Godfrey, 1989; Firing et al., 1999); • Westward propagating eddies and/or Rossby waves encounter large islands and produce boundary

Development of Laser-induced Grating Spectroscopy for Underwater Temperature Measurement in Shock Wave Focusing Regions

NASA Technical Reports Server (NTRS)

Gojani, Ardian B.; Danehy, Paul M.; Alderfer, David W.; Saito, Tsutomu; Takayama, Kazuyoshi

2003-01-01

In Extracorporeal Shock Wave Lithotripsy (ESWL) underwater shock wave focusing generates high pressures at very short duration of time inside human body. However, it is not yet clear how high temperatures are enhanced at the spot where a shock wave is focused. The estimation of such dynamic temperature enhancements is critical for the evaluation of tissue damages upon shock loading. For this purpose in the Interdisciplinary Shock Wave Research Center a technique is developed which employs laser induced thermal acoustics or Laser Induced Grating Spectroscopy. Unlike most of gasdynamic methods of measuring physical quantities this provides a non-invasive one having spatial and temporal resolutions of the order of magnitude of 1.0 mm3 and 400 ns, respectively. Preliminary experiments in still water demonstrated that this method detected sound speed and hence temperature in water ranging 283 K to 333 K with errors of 0.5%. These results may be used to empirically establish the equation of states of water, gelatin or agar cells which will work as alternatives of human tissues.

Laboratory testing the Anaconda.

PubMed

Chaplin, J R; Heller, V; Farley, F J M; Hearn, G E; Rainey, R C T

2012-01-28

Laboratory measurements of the performance of the Anaconda are presented, a wave energy converter comprising a submerged water-filled distensible tube aligned with the incident waves. Experiments were carried out at a scale of around 1:25 with a 250 mm diameter and 7 m long tube, constructed of rubber and fabric, terminating in a linear power take-off of adjustable impedance. The paper presents some basic theory that leads to predictions of distensibility and bulge wave speed in a pressurized compound rubber and fabric tube, including the effects of inelastic sectors in the circumference, longitudinal tension and the surrounding fluid. Results are shown to agree closely with measurements in still water. The theory is developed further to provide a model for the propagation of bulges and power conversion in the Anaconda. In the presence of external water waves, the theory identifies three distinct internal wave components and provides theoretical estimates of power capture. For the first time, these and other predictions of the behaviour of the Anaconda, a device unlike almost all other marine systems, are shown to be in remarkably close agreement with measurements.

A method for determining average beach slope and beach slope variability for U.S. sandy coastlines

USGS Publications Warehouse

Doran, Kara S.; Long, Joseph W.; Overbeck, Jacquelyn R.

2015-01-01

The U.S. Geological Survey (USGS) National Assessment of Hurricane-Induced Coastal Erosion Hazards compares measurements of beach morphology with storm-induced total water levels to produce forecasts of coastal change for storms impacting the Gulf of Mexico and Atlantic coastlines of the United States. The wave-induced water level component (wave setup and swash) is estimated by using modeled offshore wave height and period and measured beach slope (from dune toe to shoreline) through the empirical parameterization of Stockdon and others (2006). Spatial and temporal variability in beach slope leads to corresponding variability in predicted wave setup and swash. For instance, seasonal and storm-induced changes in beach slope can lead to differences on the order of 1 meter (m) in wave-induced water level elevation, making accurate specification of this parameter and its associated uncertainty essential to skillful forecasts of coastal change. A method for calculating spatially and temporally averaged beach slopes is presented here along with a method for determining total uncertainty for each 200-m alongshore section of coastline.

Ginzburg-Landau equation as a heuristic model for generating rogue waves

NASA Astrophysics Data System (ADS)

Lechuga, Antonio

2016-04-01

Envelope equations have many applications in the study of physical systems. Particularly interesting is the case 0f surface water waves. In steady conditions, laboratory experiments are carried out for multiple purposes either for researches or for practical problems. In both cases envelope equations are useful for understanding qualitative and quantitative results. The Ginzburg-Landau equation provides an excellent model for systems of that kind with remarkable patterns. Taking into account the above paragraph the main aim of our work is to generate waves in a water tank with almost a symmetric spectrum according to Akhmediev (2011) and thus, to produce a succession of rogue waves. The envelope of these waves gives us some patterns whose model is a type of Ginzburg-Landau equation, Danilov et al (1988). From a heuristic point of view the link between the experiment and the model is achieved. Further, the next step consists of changing generating parameters on the water tank and also the coefficients of the Ginzburg-Landau equation, Lechuga (2013) in order to reach a sufficient good approach.

Observations and Simulations of the Impact of Wave-Current Interaction on Wave Direction in the Surf Zone

NASA Astrophysics Data System (ADS)

Hopkins, Julia; Elgar, Steve; Raubenheimer, Britt

2017-04-01

Accurately characterizing the interaction of waves and currents can improve predictions of wave propagation and subsequent sediment transport in the nearshore. Along the southern shoreline of Martha's Vineyard, MA, waves propagate across strong tidal currents as they shoal, providing an ideal environment for investigating wave-current interaction. Wave directions and mean currents observed for two 1-month-long periods in 7- and 2-m water depths along 11 km of the Martha's Vineyard shoreline have strong tidal modulations. Wave directions shift by as much as 70 degrees over a tidal cycle in 7 m depth, and by as much as 25 degrees in 2 m depth. The magnitude of the tidal modulations in the wave field decreases alongshore to the west, consistent with the observed decrease in tidal currents from 2.1 to 0.2 m/s. The observations are reproduced accurately by a numerical model (SWAN and Deflt3D-FLOW) that simulates waves and currents over the observed bathymetry. Model simulations with and without wave-current interaction and tidal depth changes demonstrate that the observed tidal modulations of the wave field primarily are caused by wave-current interaction and not by tidal changes to water depths over the nearby complex shoals. Sediment transport estimates from simulated wave conditions using a range of tidal currents and offshore wave fields indicate that the modulation of the wave field at Martha's Vineyard can impact the direction of wave-induced alongshore sediment transport, sometimes driving transport opposing the direction of the offshore incident wave field. As such, the observations and model simulations suggest the importance of wave-current interaction to tidally averaged transport in mixed-energy wave-and-current nearshore environments. Supported by ASD(R&E), NSF, NOAA (Sea Grant), and ONR.

Rough surface wavelength measurement through self mixing of Doppler microwave backscatter. [from ocean waves

NASA Technical Reports Server (NTRS)

Weissman, D. E.; Johnson, J. W.

1979-01-01

A microwave backscatter technique is presented that has the ability to sense the dominant surface wavelength of a random rough surface. The purpose of this technique is to perform this measurement from an aircraft or spacecraft, wherein the horizontal velocity of the radar is an important parameter of the measurement system. Attention will be directed at water surface conditions for which a dominant wavelength can be defined, then the spatial variations of reflectivity will have a two dimensional spectrum that is sufficiently close to that of waves to be useful. The measurement concept is based on the relative motion between the water waves and a nadir looking radar, and the fact that while the instantaneous Doppler frequency at the receiver returned by any elementary group of scatterers on a water wave is monotonically changing, the difference in the Doppler frequency between any two scattering 'patches' stays approximately constant as these waves travel parallel to the major axis of an elliptical antenna footprint. The results of a theoretical analysis and a laboratory experiment with a continuous wave (CW) radar that encompasses several of the largest waves in the illuminated area show how the structure in the Doppler spectrum of the backscattered signal is related to the surface spectrum and its parameters in an especially direct and simple way when an incoherent envelope detector is the receiver.

Fully- and weakly-nonlinear biperiodic traveling waves in shallow water

NASA Astrophysics Data System (ADS)

Hirakawa, Tomoaki; Okamura, Makoto

2018-04-01

We directly calculate fully nonlinear traveling waves that are periodic in two independent horizontal directions (biperiodic) in shallow water. Based on the Riemann theta function, we also calculate exact periodic solutions to the Kadomtsev-Petviashvili (KP) equation, which can be obtained by assuming weakly-nonlinear, weakly-dispersive, weakly-two-dimensional waves. To clarify how the accuracy of the biperiodic KP solution is affected when some of the KP approximations are not satisfied, we compare the fully- and weakly-nonlinear periodic traveling waves of various wave amplitudes, wave depths, and interaction angles. As the interaction angle θ decreases, the wave frequency and the maximum wave height of the biperiodic KP solution both increase, and the central peak sharpens and grows beyond the height of the corresponding direct numerical solutions, indicating that the biperiodic KP solution cannot qualitatively model direct numerical solutions for θ ≲ 45^\\circ . To remedy the weak two-dimensionality approximation, we apply the correction of Yeh et al (2010 Eur. Phys. J. Spec. Top. 185 97-111) to the biperiodic KP solution, which substantially improves the solution accuracy and results in wave profiles that are indistinguishable from most other cases.

High-resolution seismic measurements at loamy dikes for monitoring high-water influences

NASA Astrophysics Data System (ADS)

Jaksch, Katrin; Giese, Rüdiger

2010-05-01

For the risk management of high-water events it is important to know how secure river dikes are. Even the structures of dikes are often unknown. Methods for the exploration of existing dikes and of their underground, for an evaluation of failure potential and strengthening requirements are needed. In the presented work, the potential of a high-resolution seismics to monitor the moisture penetration of dikes during flood periods was analyzed. To identify the extent of moisture penetration and to determine the structures of a loamy dike body would enable to determine the probability of a dike failure. Dikes made of loam show a different behavior of moisture penetration under high-water influence. The distribution and penetration of water is moderate compared to sandy dikes and resist longer high-water events. The water expands slowly in the dike body in all directions known as fingering. It should be analyzed how the moisture penetration from a dike can be displayed with seismic methods. The aim was to identify on the basis of seismic measurements the areas of moisture penetration within a dike during a flood and out of it to determine the probability of collapse of the dike. For that purpose the structures in the dike body should be determined in reference to the materials and his soil parameters like water content and porosity. A test facility was built for dikes including a regulation for the water level. This allowed the simulation of flood scenarios at dikes. Two dikes with different loam content were built in order to determine the failure mechanism of dikes. With a width of 8 meters at the basis they had nearly the dimension of river dikes. Seismic instrumentation was installed on both dike models. The seismic survey consists of three parallel receiver lines on the dike which recorded seismic signals emitted along the same lines, resulting in a 3D-seismic data set. The receivers were 3-component-geophones fixed in spikes, at the flooded side of the dike were taken water-proof geophones. In order to achieve a high resolution a magnetostricitve actuator was used as seismic source. The actuator generated sweeps within a frequency range from 100 up to 6100 Hz. The measurements show a complex wave field, which is dominated by direct P-waves, surface waves as well as refracted waves at the boundaries of the model. The frequencies of the direct P-waves are up to 3000 Hz at small offsets and beyond it declines to about 700 to 900 Hz. Close to the source the entire sweep energy for all frequencies is transmitted in the dike. Surface waves show frequencies from 300 to 400 Hz. A comparison of seismic data at not flooded conditions and at high flood mark shows clearly that the seismic waves were attenuated due to strong moisture penetration of the dike, surface waves were not observed after flooding the dike. Also, travel times and wave field differ in their characteristics. With increasing moisture content in the dike body the P-wave velocity decreases continuously over 30 percent from 290 m/s at not flooded conditions to 200 m/s at the highest flood. The first breaks at longer distances of the measured data stem from refractions at the dike underground which is made of concrete. Calculated travel time tomography's of different saturation states of the dike show the water content in the dike body on the basis of a correlation with the P-wave velocity. Structural heterogeneities in the dike were also visualized by the travel time tomography's.

The influences of soil and nearby structures on dispersion characteristics of wave propagating along buried plastic pipes

NASA Astrophysics Data System (ADS)

Liu, Shuyong; Jiang, J.; Parr, Nicola

2016-09-01

Water loss in distribution systems is a global problem for the water industry and governments. According to the international water supply association (IWSA), as a result of leaks from distribution pipes, 20% to 30% of water is lost while in transit from treatment plants to consumers. Although governments have tried to push the water industry to reduce the water leaks, a lot of experts have pointed out that a wide use of plastic pipes instead of metal pipes in recent years has caused difficulties in the detection of leaks using current acoustic technology. Leaks from plastic pipes are much quieter than traditional metal pipes and comparing to metal pipes the plastic pipes have very different coupling characteristics with soil, water and surrounding structures, such as other pipes, road surface and building foundations. The dispersion characteristics of wave propagating along buried plastic pipes are investigated in this paper using finite element and boundary element based models. Both empty and water- filled pipes were considered. Influences from nearby pipes and building foundations were carefully studied. The results showed that soil condition and nearby structures have significant influences on the dispersion characteristics of wave propagating along buried plastic pipes.

Sele coastal plain flood risk due to wave storm and river flow interaction

NASA Astrophysics Data System (ADS)

Benassai, Guido; Aucelli, Pietro; Di Paola, Gianluigi; Della Morte, Renata; Cozzolino, Luca; Rizzo, Angela

2016-04-01

Wind waves, elevated water levels and river discharge can cause flooding in low-lying coastal areas, where the water level is the interaction between wave storm elevated water levels and river flow interaction. The factors driving the potential flood risk include weather conditions, river water stage and storm surge. These data are required to obtain inputs to run the hydrological model used to evaluate the water surface level during ordinary and extreme events regarding both the fluvial overflow and storm surge at the river mouth. In this paper we studied the interaction between the sea level variation and the river hydraulics in order to assess the location of the river floods in the Sele coastal plain. The wave data were acquired from the wave buoy of Ponza, while the water level data needed to assess the sea level variation were recorded by the tide gauge of Salerno. The water stages, river discharges and rating curves for Sele river were provided by Italian Hydrographic Service (Servizio Idrografico e Mareografico Nazionale, SIMN).We used the dataset of Albanella station (40°29'34.30"N, 15°00'44.30"E), located around 7 km from the river mouth. The extreme river discharges were evaluated through the Weibull equation, which were associated with their return period (TR). The steady state river water levels were evaluated through HEC-RAS 4.0 model, developed by Hydrologic Engineering Center (HEC) of the United States Army Corps of Engineers Hydrologic Engineering Center (USACE,2006). It is a well-known 1D model that computes water surface elevation (WSE) and velocity at discrete cross-sections by solving continuity, energy and flow resistance (e.g., Manning) equation. Data requirements for HEC-RAS include topographic information in the form of a series of cross-sections, friction parameter in the form of Manning's n values across each cross-section, and flow data including flow rates, flow change locations, and boundary conditions. For a steady state sub-critical simulation, the boundary condition is a known downstream WSE, in this case the elevated water level due to wave setup, wind setup and inverted barometer, while the upstream boundary condition consisted in WSE corresponding to river discharges associated to different return periods. The results of the simulations evidence, for the last 10 kilometers of the river, the burst of critical inundation scenarios even with moderate flow discharge, if associated with concurrent storm surge which increase the water level at the river mouth, obstructing normal flow discharge.

Nonlinear dead water resistance at subcritical speed

NASA Astrophysics Data System (ADS)

Grue, John

2015-08-01

The dead water resistance F 1 = /1 2 C d w ρ S U 2 (ρ fluid density, U ship speed, S wetted body surface, Cdw resistance coefficient) on a ship moving at subcritical speed along the upper layer of a two-layer fluid is calculated by a strongly nonlinear method assuming potential flow in each layer. The ship dimensions correspond to those of the Polar ship Fram. The ship draught, b0, is varied in the range 0.25h0-0.9h0 (h0 the upper layer depth). The calculations show that Cdw/(b0/h0)2 depends on the Froude number only, in the range close to critical speed, Fr = U/c0 ˜ 0.875-1.125 (c0 the linear internal long wave speed), irrespective of the ship draught. The function Cdw/(b0/h0)2 attains a maximum at subcritical Froude number depending on the draught. Maximum Cdw/(b0/h0)2 becomes 0.15 for Fr = 0.76, b0/h0 = 0.9, and 0.16 for Fr = 0.74, b0/h0 = 1, where the latter extrapolated value of the dead water resistance coefficient is about 60 times higher than the frictional drag coefficient and relevant for the historical dead water observations. The nonlinear Cdw significantly exceeds linear theory (Fr < 0.85). The ship generated waves have a wave height comparable to the upper layer depth. Calculations of three-dimensional wave patterns at critical speed compare well to available laboratory experiments. Upstream solitary waves are generated in a wave tank of finite width, when the layer depths differ, causing an oscillation of the force. In a wide ocean, a very wide wave system develops at critical speed. The force approaches a constant value for increasing time.

Investigation of the foam influence on the wind-wave momentum exchange and cross-polarization microwave radar return within laboratory modeling of atmosphere-ocean boundary layer

NASA Astrophysics Data System (ADS)

Sergeev, Daniil; Troitskaya, Yuliya; Vdovin, Maxim; Ermoshkin, Alexey

2016-04-01

The effect of foam presence on the transfer processes and the parameters of the surface roughness within the laboratory simulation of wind-wave interaction was carried out on the Thermostratified Wind-Wave Tank (TSWiWaT) IAP, using a specially designed foam generator. The parameters of air flow profiles and waves elevation were measured with scanning Pitot gauge and wire wave gauges respectively in the range of equivalent wind speed U10 from 12 to 38 m/s (covering strong winds) on the clean water and with foam. It was shown that the foam reduces the amplitudes and slopes of the waves in comparison with the clean water in the hole range of wind speeds investigated, and the peak frequency and wave numbers remain almost constant. The drag coefficient calculating by profiling method demonstrated similar behavior (almost independent on U10) for case of foam and increased compared with clear water, particularly noticeable for low wind speeds. Simultaneously the investigations of influence of the foam on the peculiarity of the microwave radio back scattering of X-diapason was investigated. These measurements were carried for different sensing angles (30, 40 i 50 degrees from vertical) and for four polarizations: co-polarized HH and VV, and de-polarized HV and VH. It was shown that foam leads to decrease of specific radar cross section of the wavy surface in comparison with clean water. The work was supported by the Russian Foundation for Basic Research (grants No. 15-35-20953, 14-05-00367, 16-55-52022) and project ASIST of FP7. The experiment is supported by Russian Science Foundation (Agreement No. 15-17-20009), radilocation measurments are partially supported by Russian Science Foundation (Agreement No. 14-17-00667).

Rotating magnetic shallow water waves and instabilities in a sphere

NASA Astrophysics Data System (ADS)

Márquez-Artavia, X.; Jones, C. A.; Tobias, S. M.

2017-07-01

Waves in a thin layer on a rotating sphere are studied. The effect of a toroidal magnetic field is considered, using the shallow water ideal MHD equations. The work is motivated by suggestions that there is a stably stratified layer below the Earth's core mantle boundary, and the existence of stable layers in stellar tachoclines. With an azimuthal background field known as the Malkus field, ?, ? being the co-latitude, a non-diffusive instability is found with azimuthal wavenumber ?. A necessary condition for instability is that the Alfvén speed exceeds ? where ? is the rotation rate and ? the sphere radius. Magneto-inertial gravity waves propagating westward and eastward occur, and become equatorially trapped when the field is strong. Magneto-Kelvin waves propagate eastward at low field strength, but a new westward propagating Kelvin wave is found when the field is strong. Fast magnetic Rossby waves travel westward, whilst the slow magnetic Rossby waves generally travel eastward, except for some ? modes at large field strength. An exceptional very slow westward ? magnetic Rossby wave mode occurs at all field strengths. The current-driven instability occurs for ? when the slow and fast magnetic Rossby waves interact. With strong field the magnetic Rossby waves become trapped at the pole. An asymptotic analysis giving the wave speed and wave form in terms of elementary functions is possible both in polar trapped and equatorially trapped cases.

Wave loading on bridge decks : final report, December 2009.

DOT National Transportation Integrated Search

2009-12-01

This report covers the results of experimental and theoretical analyses of wave loading on bridge superstructures. A number of wave tank tests were performed on both slab and girder type spans with different water depths, span positions relative to t...

Army Net Zero Prove Out. Army Net Zero Training Report

DTIC Science & Technology

2014-11-20

existing reporting systems (e.g., Army Energy and Water Reporting System, Solid Waste Annual Reporting- web , Headquarters Army Environmental System). 3...Testing a wave energy converter  Harnesses the pressure of a wave on the ocean floor 22  Conduct thermal building envelope analysis  IR ...bathroom f ixtures, ai r handling units, Less than 3𔄃W i rrigat ion controls w ith EPA Water’Sense approved equipment 1% 0 . .279% Acqu ire lower water

Seismic moulin tremor

NASA Astrophysics Data System (ADS)

Roeoesli, Claudia; Walter, Fabian; Ampuero, Jean-Paul; Kissling, Edi

2016-08-01

Through glacial moulins, meltwater is routed from the glacier surface to its base. Moulins are a main feature feeding subglacial drainage systems and thus influencing basal motion and ice dynamics, but their geometry remains poorly known. Here we show that analysis of the seismic wavefield generated by water falling into a moulin can help constrain its geometry. We present modeling results of hour-long seimic tremors emitted from a vertical moulin shaft, observed with a seismometer array installed at the surface of the Greenland Ice Sheet. The tremor was triggered when the moulin water level exceeded a certain height, which we associate with the threshold for the waterfall to hit directly the surface of the moulin water column. The amplitude of the tremor signal changed over each tremor episode, in close relation to the amount of inflowing water. The tremor spectrum features multiple prominent peaks, whose characteristic frequencies are distributed like the resonant modes of a semiopen organ pipe and were found to depend on the moulin water level, consistent with a source composed of resonant tube waves (water pressure waves coupled to elastic deformation of the moulin walls) along the water-filled moulin pipe. Analysis of surface particle motions lends further support to this interpretation. The seismic wavefield was modeled as a superposition of sustained wave radiation by pressure sources on the side walls and at the bottom of the moulin. The former was found to dominate the wave field at close distance and the latter at large distance to the moulin.

Effects of contrasting wave conditions on scour and drag on pioneer tidal marsh plants

NASA Astrophysics Data System (ADS)

Silinski, Alexandra; Heuner, Maike; Troch, Peter; Puijalon, Sara; Bouma, Tjeerd J.; Schoelynck, Jonas; Schröder, Uwe; Fuchs, Elmar; Meire, Patrick; Temmerman, Stijn

2016-02-01

Tidal marshes are increasingly valued for protecting shorelines against wave impact, but waves in turn may limit the initial establishment of tidal marsh pioneer plants. In estuaries, the shorelines typically experience a wide range of wave periods, varying from short period wind waves (usually of around 1-2 s in fair weather conditions) to long ship-generated waves, with secondary waves in the order of 2-7 s and primary waves with periods that can exceed 1 min. Waves are known to create sediment scour around, as well as to exert drag forces on obstacles such as seedlings and adults of establishing pioneer plant species. In intertidal systems, these two mechanisms have been identified as main causes for limiting potential colonization of bare tidal flats. In this paper, we want to assess to which extent common quantitative formulae for predicting local scour and drag forces on rigid cylindrical obstacles are valid for the estimation of scour and drag on slightly flexible plants with contrasting morphology, and hence applicable to predict plant establishment and survival under contrasting wave conditions. This has been tested in a full-scale wave flume experiment on two pioneer species (Scirpus maritimus and Scirpus tabernaemontani) and two life stages (seedlings and adults of S. maritimus) as well as on cylindrical reference sticks, which we have put under a range of wave periods (2-10 s), intended to mimic natural wind waves (short period waves) and ship-induced waves (artificial long period waves), at three water levels (5, 20, 35 cm). Our findings suggest that at very shallow water depths (5 cm) particular hydrodynamic conditions are created that lead to drag and scour that deviate from predictions. For higher water levels (20, 35 cm) scour can be well predicted for all wave conditions by an established formula for wave-induced scour around rigid cylinders. Drag forces can be relatively well predicted after introducing experimentally derived drag coefficients that are specific for the different plant morphologies. Best predictions were found for plants with a simple near-cylindrical morphology such as S. tabernaemontani, but are less accurate for plants of more complex structure such as S. maritimus, particularly for long period waves. In conclusion, our study offers valuable insights towards predicting/modelling the conditions under which seedlings and shoots of pioneer species can establish, and elucidates that long waves are more likely to counteract successful plant establishment than natural short waves.

In Pursuit of Nearshore Wave Characteristics- Implementation and Validation of a Shallow Water Correction for High Frequency Radars along the New Jersey Coast

NASA Astrophysics Data System (ADS)

Livermont, E. A.

2014-12-01

Within the U.S., coastal ocean current mapping with HF radar has matured to the point where it is now considered an essential component of regional ocean observing systems. A Mid-Atlantic HF radar network now provides high-resolution coverage within five localized networks, which are linked together to cover the full range of the Mid-Atlantic coast. While the primary focus of these networks has been on offshore current mapping observations, a long-term objective has been to develop and evaluate nearshore waves and currents. Of particular interest is the height of ocean waves that play a crucial role in engineering projects, ship navigation and design, vessel traffic control as well as shoreline protection, beach erosion, and mitigation of oil spills and ocean pollution. The radars owned by Rutgers University cover the coastline of New Jersey at multiple frequencies from 4.5 to 25 MHz. Their echoes contain information on both currents and waves from deep water up into the shallow coastal zone, providing an excellent archive for this study. Radar sea-echo spectra consist of dominant first-order peaks surrounded with lower-energy second-order structures. Present analysis methods assume that the waves do not interact with the ocean floor. The assumption of deep water is often invalid close to the coast and for broad continental shelves, and is particularly inadequate to describe the second-order sea-echo used to give information on ocean waves. Additionally, second-order echo is often only visible above the noise floor at close ranges. In this paper, a shallow water spectral theory is implemented at four locations on the New Jersey coast- Strathmere, Wildwood, Brant Beach, and Sea Bright. The corrected wave characteristics extracted from the HF radars were then compared to several in situ wave measurements. The first three sites—Strathmere, Wildwood and Brant Beach—were validated against two long-term (1999-2007) wave gauges deployed by Stevens Institute of Technology in 5 meters of water. Based on this initial comparison, several additional corrections to the radar processing were implemented. The site at Sea Bright was used for independent verification and validated against an ADCP deployed for three weeks in March 2012.

Multiple periodic-soliton solutions of the (3+1)-dimensional generalised shallow water equation

NASA Astrophysics Data System (ADS)

Li, Ye-Zhou; Liu, Jian-Guo

2018-06-01

Based on the extended variable-coefficient homogeneous balance method and two new ansätz functions, we construct auto-Bäcklund transformation and multiple periodic-soliton solutions of (3 {+} 1)-dimensional generalised shallow water equations. Completely new periodic-soliton solutions including periodic cross-kink wave, periodic two-solitary wave and breather type of two-solitary wave are obtained. In addition, cross-kink three-soliton and cross-kink four-soliton solutions are derived. Furthermore, propagation characteristics and interactions of the obtained solutions are discussed and illustrated in figures.

Working Group on Ice Forces (4th) State-of-the-Art Report Held in Iowa City, Iowa in 1986.

DTIC Science & Technology

1989-02-01

INTRODUCTION When droplets generated from sea water fly in cold air, cool and hit an object, spray ice will form. Spray ice causes hazards and...or spray generated by waves hitting the structure. Wind-generated spray forms as a result of direct whipping of wave crests by the wind and of bursting...Spray generated by waves hitting a structure, on the other hand, can result in very high liquid water contents. Values of up to 5 kgm -3 have been

CMS-Wave

DTIC Science & Technology

2014-10-27

a phase-averaged spectral wind-wave generation and transformation model and its interface in the Surface-water Modeling System (SMS). Ambrose...applications of the Boussinesq (BOUSS-2D) wave model that provides more rigorous calculations for design and performance optimization of integrated...navigation systems . Together these wave models provide reliable predictions on regional and local spatial domains and cost-effective engineering solutions

33 CFR 177.07 - Other unsafe conditions.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) The wave height within the Regulated Boating Area is 4 feet or greater; or (2) The wave height within the Regulated Boating Area is equal to or greater than the wave height determined by the formula L/10... from the lowest point along the upper strake edge to the surface of the water. W=Maximum wave height in...

33 CFR 177.07 - Other unsafe conditions.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) The wave height within the Regulated Boating Area is 4 feet or greater; or (2) The wave height within the Regulated Boating Area is equal to or greater than the wave height determined by the formula L/10... from the lowest point along the upper strake edge to the surface of the water. W=Maximum wave height in...

33 CFR 177.07 - Other unsafe conditions.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) The wave height within the Regulated Boating Area is 4 feet or greater; or (2) The wave height within the Regulated Boating Area is equal to or greater than the wave height determined by the formula L/10... from the lowest point along the upper strake edge to the surface of the water. W=Maximum wave height in...

Empirical Guidelines for Use of Irregular Wave Model to Estimate Nearshore Wave Height.

DTIC Science & Technology

1982-07-01

height, the easier to use tech- nique presented by McClenan (1975) was employed. The McClenan technique uti- lizes a monogram which was constructed from...the SPM equations and gives the same results. The inputs to the monogram technique are the period, the deep- water wave height, the deepwater wave

Digital core based transmitted ultrasonic wave simulation and velocity accuracy analysis

NASA Astrophysics Data System (ADS)

Zhu, Wei; Shan, Rui

2016-06-01

Transmitted ultrasonic wave simulation (TUWS) in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When simulating wave propagates in a 3D digital core, two additional layers are attached to its two surfaces vertical to the wave-direction and one planar wave source and two receiver-arrays are properly installed. After source excitation, the two receivers then record incident and transmitted waves of the digital rock. Wave propagating velocity, which is the velocity of the digital core, is computed by the picked peak-time difference between the two recorded waves. To evaluate the accuracy of TUWS, a digital core is fully saturated with gas, oil, and water to calculate the corresponding velocities. The velocities increase with decreasing wave frequencies in the simulation frequency band, and this is considered to be the result of scattering. When the pore fluids are varied from gas to oil and finally to water, the velocity-variation characteristics between the different frequencies are similar, thereby approximately following the variation law of velocities obtained from linear elastic statics simulation (LESS), although their absolute values are different. However, LESS has been widely used. The results of this paper show that the transmission ultrasonic simulation has high relative precision.

Ocean Wave-to-Ice Energy Transfer Determined from Seafloor Pressure and Ice Shelf Seismic Observations

NASA Astrophysics Data System (ADS)

Chen, Z.; Bromirski, P. D.; Gerstoft, P.; Stephen, R. A.; Wiens, D.; Aster, R. C.; Nyblade, A.

2017-12-01

Ice shelves play an important role in buttressing land ice from reaching the sea, thus restraining the rate of sea level rise. Long-period gravity wave impacts excite vibrations in ice shelves that may trigger tabular iceberg calving and/or ice shelf collapse events. Three kinds of seismic plate waves were continuously observed by broadband seismic arrays on the Ross Ice Shelf (RIS) and on the Pine Island Glacier (PIG) ice shelf: (1) flexural-gravity waves, (2) flexural waves, and (3) extensional Lamb waves, suggesting that all West Antarctic ice shelves are subjected to similar gravity wave excitation. Ocean gravity wave heights were estimated from pressure perturbations recorded by an ocean bottom differential pressure gauge at the RIS front, water depth 741 m, about 8 km north of an on-ice seismic station that is 2 km from the shelf front. Combining the plate wave spectrum, the frequency-dependent energy transmission and reflection at the ice-water interface were determined. In addition, Young's modulus and Poisson's ratio of the RIS are estimated from the plate wave motions, and compared with the widely used values. Quantifying these ice shelf parameters from observations will improve modeling of ice shelf response to ocean forcing, and ice shelf evolution.

Simulation of asteroid impact on ocean surfaces, subsequent wave generation and the effect on US shorelines

DOE PAGES

Ezzedine, Souheil M.; Lomov, Ilya; Miller, Paul L.; ...

2015-05-19

As part of a larger effort involving members of several other organizations, we have conducted numerical simulations in support of emergency-response exercises of postulated asteroid ocean impacts. We have addressed the problem from source (asteroid entry) to ocean impact (splash) to wave generation, propagation and interaction with the U.S. shoreline. We simulated three impact sites. The first site is located off the east coast by Maryland's shoreline. The second site is located off of the West coast, the San Francisco bay. The third set of sites are situated in the Gulf of Mexico. Asteroid impacts on the ocean surface aremore » conducted using LLNL's hydrocode GEODYN to create the impact wave source for the shallow water wave propagation code, SWWP, a shallow depth averaged water wave code.« less

Measurement of stimulated Hawking emission in an analogue system.

PubMed

Weinfurtner, Silke; Tedford, Edmund W; Penrice, Matthew C J; Unruh, William G; Lawrence, Gregory A

2011-01-14

Hawking argued that black holes emit thermal radiation via a quantum spontaneous emission. To address this issue experimentally, we utilize the analogy between the propagation of fields around black holes and surface waves on moving water. By placing a streamlined obstacle into an open channel flow we create a region of high velocity over the obstacle that can include surface wave horizons. Long waves propagating upstream towards this region are blocked and converted into short (deep-water) waves. This is the analogue of the stimulated emission by a white hole (the time inverse of a black hole), and our measurements of the amplitudes of the converted waves demonstrate the thermal nature of the conversion process for this system. Given the close relationship between stimulated and spontaneous emission, our findings attest to the generality of the Hawking process.

Rotational superradiant scattering in a vortex flow

NASA Astrophysics Data System (ADS)

Torres, Theo; Patrick, Sam; Coutant, Antonin; Richartz, Maurício; Tedford, Edmund W.; Weinfurtner, Silke

2017-09-01

When an incident wave scatters off of an obstacle, it is partially reflected and partially transmitted. In theory, if the obstacle is rotating, waves can be amplified in the process, extracting energy from the scatterer. Here we describe in detail the first laboratory detection of this phenomenon, known as superradiance. We observed that waves propagating on the surface of water can be amplified after being scattered by a draining vortex. The maximum amplification measured was 14% +/- 8%, obtained for 3.70 Hz waves, in a 6.25-cm-deep fluid, consistent with the superradiant scattering caused by rapid rotation. We expect our experimental findings to be relevant to black-hole physics, since shallow water waves scattering on a draining fluid constitute an analogue of a black hole, as well as to hydrodynamics, due to the close relation to over-reflection instabilities.

Simulation of asteroid impact on ocean surfaces, subsequent wave generation and the effect on US shorelines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ezzedine, Souheil M.; Lomov, Ilya; Miller, Paul L.

As part of a larger effort involving members of several other organizations, we have conducted numerical simulations in support of emergency-response exercises of postulated asteroid ocean impacts. We have addressed the problem from source (asteroid entry) to ocean impact (splash) to wave generation, propagation and interaction with the U.S. shoreline. We simulated three impact sites. The first site is located off the east coast by Maryland's shoreline. The second site is located off of the West coast, the San Francisco bay. The third set of sites are situated in the Gulf of Mexico. Asteroid impacts on the ocean surface aremore » conducted using LLNL's hydrocode GEODYN to create the impact wave source for the shallow water wave propagation code, SWWP, a shallow depth averaged water wave code.« less

Testing the effectiveness of monolayers under wind and wave conditions.

PubMed

Palada, C; Schouten, P; Lemckert, C

2012-01-01

Monolayers are highly desirable for their evaporation reducing capabilities due to their relatively minimal cost and ease of application. Despite these positive attributes, monolayers have consistently failed to perform effectively due to the harsh wind and wave conditions prevalent across real-world water reserves. An exhaustive and consistent study testing the influence of wind and wave combinations on monolayer performance has yet to be presented in the literature. To remedy this, the effect of simultaneous wind and wave conditions on a benchmark high-performance monolayer (octadecanol suspension, CH(3)(CH(2))(16)CH(2)OH) has been analysed. Subjected only to waves, the monolayer remained intact due to its innate ability to compress and expand. However, the constant simultaneous application of wind and waves caused the monolayer to break up and gather down-wind where it volatilised over time. At wind speeds above 1.3 m s(-1) the monolayer was completely ineffective. For wind speeds below this threshold, the monolayer had an influence on the evaporation rate dependent on wind speed. From these results a series of application protocols can now be developed for the optimised deployment of monolayers in real-world water reserves. This will be of interest to private, commercial and government organisations involved in the storage and management of water resources.

Signatures of Air-Wave Interactions Over a Large Lake

NASA Astrophysics Data System (ADS)

Li, Qi; Bou-Zeid, Elie; Vercauteren, Nikki; Parlange, Marc

2018-06-01

The air-water exchange of momentum and scalars (temperature and water vapour) is investigated using the Lake-Atmosphere Turbulent EXchange (LATEX) dataset. The wind waves and swell are found to affect the coupling between the water surface and the air differently. The surface-stress vector aligns with the wind velocity in the presence of wind waves, but a wide range of stress-wind misalignment angles is observed during swell. The momentum transport efficiency decreases when significant stress-wind misalignment is present, suggesting a strong influence of surface wave properties on surface drag. Based on this improved understanding of the role of wave-wind misalignment, a new relative wind speed for surface-layer similarity formulations is proposed and tested using the data. The new expression yields a value of the von Kármán constant (κ ) of 0.38, compared to 0.36 when using the absolute wind speed, as well as reduced data fitting errors. Finally, the ratios of aerodynamic to scalar roughness lengths are computed and various existing models in the literature are tested using least-square fitting to the observed ratios. The tests are able to discriminate between the performance of various models; however, they also indicate that more investigations are required to understand the physics of scalar exchanges over waves.

Enhanced submarine ground water discharge form mixing of pore water and estuarine water

USGS Publications Warehouse

Martin, Jonathan B.; Cable, Jaye E.; Swarzenski, Peter W.; Lindenberg, Mary K.

2004-01-01

Submarine ground water discharge is suggested to be an important pathway for contaminants from continents to coastal zones, but its significance depends on the volume of water and concentrations of contaminants that originate in continental aquifers. Ground water discharge to the Banana River Lagoon, Florida, was estimated by analyzing the temporal and spatial variations of Cl− concentration profiles in the upper 230 cm of pore waters and was measured directly by seepage meters. Total submarine ground water discharge consists of slow discharge at depths > ∼70 cm below seafloor (cmbsf) of largely marine water combined with rapid discharge of mixed pore water and estuarine water above ∼70 cmbsf. Cl− profiles indicate average linear velocities of ∼0.014 cm/d at depths > ∼70 cmbsf. In contrast, seepage meters indicate water discharges across the sediment-water interface at rates between 3.6 and 6.9 cm/d. The discrepancy appears to be caused by mixing in the shallow sediment, which may result from a combination of bioirrigation, wave and tidal pumping, and convection. Wave and tidal pumping and convection would be minor because the tidal range is small, the short fetch of the lagoon limits wave heights, and large density contacts are lacking between lagoon and pore water. Mixing occurs to ∼70 cmbsf, which represents depths greater than previously reported. Mixing of oxygenated water to these depths could be important for remineralization of organic matter.

A laboratory investigation of mixing dynamics between biofuels and surface waters

NASA Astrophysics Data System (ADS)

Wang, Xiaoxiang; Cotel, Aline

2017-11-01

Recently, production and usage of ethanol-blend fuels or biofuels have increased dramatically along with increasing risk of spilling into surface waters. Lack of understanding of the environmental impacts and absence of standard clean-up procedures make it crucial to study the mixing behavior between biofuels and water. Biofuels are represented by a solution of ethanol and glycol. A Plexiglas tank in conjunction with a wave generator is used to simulate the mixing of surface waters and biofuels under different natural conditions. In our previous experiments, two distinct mixing regimes were observed. One regime was driven by turbulence and the other by interfacial instabilities. However, under more realistic situations, without wind driven waves, only the first mixing regime was found. After one minute of rapid turbulent mixing, biofuels and water were fully mixed and no interface was formed. During the mixing process, chemical reactions happened simultaneously and influenced mixing dynamics. Current experiments are investigating the effect of waves on the mixing dynamics. Support from NSF CBET 1335878.

Three-Dimensional Simulations of Oblique Asteroid Impacts into Water

NASA Astrophysics Data System (ADS)

Gisler, G. R.; Ferguson, J. M.; Heberling, T.; Plesko, C. S.; Weaver, R.

2016-12-01

Waves generated by impacts into oceans may represent the most significant danger from near-earth asteroids and comets. For impacts near populated shores, the crown splash and subsequent waves, accompanied by sediment lofting and high winds, could be more damaging than storm surges from the strongest hurricanes. For asteroids less than 500 m in diameter that impact into deep water far from shores, the waves produced will be detectable over large distances, but probably not significantly dangerous. We present new three-dimensional simulations of oblique impacts into deep water, with trajectory angles ranging from 20 degrees to 60 degrees (where 90 degrees is vertical). These simulations are performed with the Los Alamos Rage hydrocode, and include atmospheric effects including ablation and airbursts. These oblique impact simulations are specifically performed in order to help determine whether there are additional dangers from the obliquity of impact not covered by previous two-dimensional studies. Water surface elevation profiles, surface pressures, and depth-averaged mass fluxes within the water are prepared for use in propagation studies.

Optical fiber humidity sensor based on evanescent-wave scattering.

PubMed

Xu, Lina; Fanguy, Joseph C; Soni, Krunal; Tao, Shiquan

2004-06-01

The phenomenon of evanescent-wave scattering (EWS) is used to design an optical-fiber humidity sensor. Porous solgel silica (PSGS) coated on the surface of a silica optical-fiber core scatters evanescent waves that penetrate the coating layer. Water molecules in the gas phase surrounding the optical fiber can be absorbed into the inner surface of the pores of the porous silica. The absorbed water molecules form a thin layer of liquid water on the inner surface of the porous silica and enhance the EWS. The amount of water absorbed into the PSGS coating is in dynamic equilibrium with the water-vapor pressure in the gas phase. Therefore the humidity in the air can be quantitatively determined with fiber-optic EWS caused by the PSGS coating. The humidity sensor reported here is fast in response, reversible, and has a wide dynamic range. The possible interference caused by EWS to an optical-fiber gas sensor with a reagent-doped PSGS coating as a transducer is also discussed.

Modeling of Acoustic Field Statistics for Deep and Shallow Water Environments and 2015 CANAPE Pilot Study Moored Oceanographic Observations

DTIC Science & Technology

2015-09-30

into acoustic fluctuation calculations. In the Philippine Sea, models of eddies, internal tides, internal waves, and fine structure ( spice ) are...needed, while in the shallow water case a models of the random linear internal waves and spice are lacking. APPROACH The approach to this research is to

Stilling Waves with Ordered Molecular Monolayers

ERIC Educational Resources Information Center

Vitz, Ed

2008-01-01

A demonstration of the damping effect of an oil monolayer on water waves is described. The history of this remarkable demonstration--with a 2000 (or more) year span--and a brief explanation in terms of the properties of water and the monolayer are presented. If a layer of olive oil, one molecule thick (about one-ten millionth of a centimeter), is…

Impact of Varying Wave Conditions on the Mobility of Arsenic in a Nearshore Aquifer on the Great Lakes

NASA Astrophysics Data System (ADS)

Rakhimbekova, S.; O'Carroll, D. M.; Robinson, C. E.

2017-12-01

Groundwater-coastal water interactions play an important role in controlling the behavior of inorganic chemicals in nearshore aquifers and the subsequent flux of these chemicals to receiving coastal waters. Previous studies have shown that dynamic groundwater flows and water exchange across the sediment-water interface can set up strong geochemical gradients and an important reaction zone in a nearshore aquifer that affect the fate of reactive chemicals. There is limited understanding of the impact of transient coastal forcing such as wave conditions on groundwater dynamics and geochemistry in a nearshore aquifer. The goal of this study was to assess the impact of intensified wave conditions on the behavior of arsenic in a nearshore aquifer and to determine the hydrological and geochemical factors controlling its fate and ultimate delivery to receiving coastal waters. Field investigations were conducted over the period of intensified wave conditions on a freshwater beach on Lake Erie, Canada. High spatial resolution aqueous and sediment sampling was conducted to characterize the subsurface distribution of inorganic species in the nearshore aquifer. Numerical groundwater flow and transport simulations were conducted to evaluate wave-induced perturbations in the flow dynamics including characterizing changes in the groundwater flow recirculations in the nearshore aquifer. The combination of field data and numerical simulations reveal that varying wave conditions alter groundwater flows and set up geochemical transition zones within the aquifer resulting in the release and sequestration of arsenic. Interactions between oxic surface water, mildly reducing shallow groundwater, and reducing sulfur- and iron-rich deep groundwater promote dynamic iron, sulfur and manganese cycling which control the mobility of arsenic in the aquifer. The findings of this study have potential implications for the fate and transport of other reactive chemicals (e.g. phosphorus, mercury) in nearshore marine and freshwater aquifers exposed to transient coastal forcing. Understanding the fate of chemicals and the dynamics of the reaction zone in nearshore aquifers is critical for evaluating the importance of groundwater as a pathway for delivering pollutants to coastal waters.

Simulation of sea surface wave influence on small target detection with airborne laser depth sounding.

PubMed

Tulldahl, H Michael; Steinvall, K Ove

2004-04-20

A theoretical model for simulation of airborne depth-sounding lidar is presented with the purpose of analyzing the influence from water surface waves on the ability to detect 1-m3 targets placed on the sea bottom. Although water clarity is the main limitation, sea surface waves can significantly affect the detectability. The detection probability for a target at a 9-m depth can be above 90% at 1-m/s wind and below 80% at 6-m/s wind for the same water clarity. The simulation model contains both numerical and analytical components. Simulated data are compared with measured data and give realistic results for bottom depths between 3 and 10 m.

Lightweight dew-/frost-point hygrometer based on a surface-acoustic-wave sensor for balloon-borne atmospheric water vapor profile sounding

NASA Astrophysics Data System (ADS)

Hansford, Graeme M.; Freshwater, Ray A.; Eden, Louise; Turnbull, Katharine F. V.; Hadaway, David E.; Ostanin, Victor P.; Jones, Roderic L.

2006-01-01

The design of a very lightweight dew-/frost-point hygrometer for balloon-borne atmospheric water vapor profiling is described. The instrument is based on a surface-acoustic-wave sensor. The low instrument weight is a key feature, allowing flights on meteorological balloons which brings many more flight opportunities. The hygrometer shows consistently good performance in the troposphere and while water vapor measurements near the tropopause and in the stratosphere are possible with the current instrument, the long-time response in these regions hampers realistic measurements. The excellent intrinsic sensitivity of the surface-acoustic-wave sensor should permit considerable improvement in the hygrometer performance in the very dry regions of the atmosphere.

Optimal Control of the Valve Based on Traveling Wave Method in the Water Hammer Process

NASA Astrophysics Data System (ADS)

Cao, H. Z.; Wang, F.; Feng, J. L.; Tan, H. P.

2011-09-01

Valve regulation is an effective method for process control during the water hammer. The principle of d'Alembert traveling wave theory was used in this paper to construct the exact analytical solution of the water hammer, and the optimal speed law of the valve that can reduce the water hammer pressure in the maximum extent was obtained. Combining this law with the valve characteristic curve, the principle corresponding to the valve opening changing with time was obtained, which can be used to guide the process of valve closing and to reduce the water hammer pressure in the maximum extent.

Coastal circulation and water column properties off Kalaupapa National Historical Park, Molokai, Hawaii, 2008-2010

USGS Publications Warehouse

Storlazzi, Curt D.; Presto, Katherine; Brown, Eric K.

2011-01-01

More than 2.2 million measurements of oceanographic forcing and the resulting water-column properties were made off U.S. National Park Service's Kalaupapa National Historical Park on the north shore of Molokai, Hawaii, between 2008 and 2010 to understand the role of oceanographic processes on the health and sustainability of the area's marine resources. The tides off the Kalaupapa Peninsula are mixed semidiurnal. The wave climate is dominated by two end-members: large northwest Pacific winter swell that directly impacts the study site, and smaller, shorter-period northeast trade-wind waves that have to refract around the peninsula, resulting in a more northerly direction before propagating over the study site. The currents primarily are alongshore and are faster at the surface than close to the seabed; large wave events, however, tend to drive flow in a more cross-shore orientation. The tidal currents flood to the north and ebb to the south. The waters off the peninsula appear to be a mix of cooler, more saline, deeper oceanic waters and shallow, warmer, lower-salinity nearshore waters, with intermittent injections of freshwater, generally during the winters. Overall, the turbidity levels were low, except during large wave events. The low overall turbidity levels and rapid return to pre-event background levels following the cessation of forcing suggest that there is little fine-grained material. Large wave events likely inhibit the settlement of fine-grained sediment at the site. A number of phenomena were observed that indicate the complexity of coastal circulation and water-column properties in the area and may help scientists and resource managers to better understand the implications of the processes on marine ecosystem health.

Coastal circulation and sediment dynamics in Hanalei Bay, Kauai. Part I: Measurements of waves, currents, temperature, salinity and turbidity : June - August, 2005

USGS Publications Warehouse

Storlazzi, Curt D.; Presto, M. Kathy; Logan, Joshua B.; Field, Michael E.

2006-01-01

Introduction: High-resolution measurements of waves, currents, water levels, temperature, salinity and turbidity were made in Hanalei Bay, northern Kauai, Hawaii, during the summer of 2005 to better understand coastal circulation and sediment dynamics in coral reef habitats. A series of bottom-mounted instrument packages were deployed in water depths of 10 m or less to collect long-term, high-resolution measurements of waves, currents, water levels, temperature, salinity and turbidity. These data were supplemented with a series of vertical instrument casts to characterize the vertical and spatial variability in water column properties within the bay. The purpose of these measurements was to collect hydrographic data to learn how waves, currents and water column properties vary spatially and temporally in an embayment that hosts a nearshore coral reef ecosystem adjacent to a major river drainage. These measurements support the ongoing process studies being conducted as part of the U.S. Geological Survey (USGS) Coastal and Marine Geology Program's Coral Reef Project; the ultimate goal is to better understand the transport mechanisms of sediment, larvae, pollutants and other particles in coral reef settings. This report, the first part in a series, describes data acquisition, processing and analysis.

A Bayesian-Based System to Assess Wave-Driven Flooding Hazards on Coral Reef-Lined Coasts

NASA Astrophysics Data System (ADS)

Pearson, S. G.; Storlazzi, C. D.; van Dongeren, A. R.; Tissier, M. F. S.; Reniers, A. J. H. M.

2017-12-01

Many low-elevation, coral reef-lined, tropical coasts are vulnerable to the effects of climate change, sea level rise, and wave-induced flooding. The considerable morphological diversity of these coasts and the variability of the hydrodynamic forcing that they are exposed to make predicting wave-induced flooding a challenge. A process-based wave-resolving hydrodynamic model (XBeach Non-Hydrostatic, "XBNH") was used to create a large synthetic database for use in a "Bayesian Estimator for Wave Attack in Reef Environments" (BEWARE), relating incident hydrodynamics and coral reef geomorphology to coastal flooding hazards on reef-lined coasts. Building on previous work, BEWARE improves system understanding of reef hydrodynamics by examining the intrinsic reef and extrinsic forcing factors controlling runup and flooding on reef-lined coasts. The Bayesian estimator has high predictive skill for the XBNH model outputs that are flooding indicators, and was validated for a number of available field cases. It was found that, in order to accurately predict flooding hazards, water depth over the reef flat, incident wave conditions, and reef flat width are the most essential factors, whereas other factors such as beach slope and bed friction due to the presence or absence of corals are less important. BEWARE is a potentially powerful tool for use in early warning systems or risk assessment studies, and can be used to make projections about how wave-induced flooding on coral reef-lined coasts may change due to climate change.