WorldWideScience

Sample records for surface wave height

  1. Measuring sea surface height with a GNSS-Wave Glider

    Science.gov (United States)

    Morales Maqueda, Miguel Angel; Penna, Nigel T.; Foden, Peter R.; Martin, Ian; Cipollini, Paolo; Williams, Simon D.; Pugh, Jeff P.

    2017-04-01

    A GNSS-Wave Glider is a novel technique to measure sea surface height autonomously using the Global Navigation Satellite System (GNSS). It consists of an unmanned surface vehicle manufactured by Liquid Robotics, a Wave Glider, and a geodetic-grade GNSS antenna-receiver system, with the antenna installed on a mast on the vehicle's deck. The Wave Glider uses the differential wave motion through the water column for propulsion, thus guaranteeing an, in principle, indefinite autonomy. Solar energy is collected to power all on-board instrumentation, including the GNSS system. The GNSS-Wave Glider was first tested in Loch Ness in 2013, demonstrating that the technology is capable of mapping geoid heights within the loch with an accuracy of a few centimetres. The trial in Loch Ness did not conclusively confirm the reliability of the technique because, during the tests, the state of the water surface was much more benign than would normally be expect in the open ocean. We now report on a first deployment of a GNSS-Wave Glider in the North Sea. The deployment took place in August 2016 and lasted thirteen days, during which the vehicle covered a distance of about 350 nautical miles in the north western North Sea off Great Britain. During the experiment, the GNSS-Wave Glider experienced sea states between 1 (0-0.1 m wave heights) and 5 (2.5-4 m wave heights). The GNSS-Wave Glider data, recorded at 5 Hz frequency, were analysed using a post-processed kinematic GPS-GLONASS precise point positioning (PPP) approach, which were quality controlled using double difference GPS kinematic processing with respect to onshore reference stations. Filtered with a 900 s moving-average window, the PPP heights reveal geoid patterns in the survey area that are very similar to the EGM2008 geoid model, thus demonstrating the potential use of a GNSS-Wave Glider for marine geoid determination. The residual of subtracting the modelled or measured marine geoid from the PPP signal combines information

  2. Observing seasonal variations of sea surface wind speed and significant wave height using TOPEX altimetry

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    One year of ocean topography experiment (TOPEX) altimeter data are used to study the seasonal variations of global sea surface wind speed and significant wave height. The major wind and wave zones of the world oceans are precisely identified, their seasonal variability and characteristics are quantitatively analyzed, and the diversity of global wind speed seasonality and the variability of significant wave height in response to sea surface wind speed are also revealed.

  3. Gridded 5-day mean sea surface height anomaly and significant wave height from Jason-1 and OSTM/Jason-2 satellites (NODC Accession 0065055)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains the gridded 5-day mean sea surface height anomaly (SSHA) and Ku Band significant wave height (SWH-KU) observed from Jason-1 and OSTM/Jason-2...

  4. On the hysteresis of the sea surface and its applicability to wave height predictions

    Science.gov (United States)

    Parsons, C. L.

    1977-01-01

    Because of the low dissipation rate of wave energy on the ocean's surface, the wave height at some location and time must be dependent upon wind fields in existence there at previous times and upon swell propagated there from other regions. To study these relationships, significant wave height (SWH) measurements from the Geos-3 radar altimeter are used in conjunction with anemometer windspeed measurements from weather ships, L, C, and R. During the passage of large cyclonic disturbances near the fixed locations of these vessels in the North Atlantic in February 1976, distinct hysteresis profiles that characterize the sea's memory during generation and dissipation conditions are observed. Examples are given that demonstrate the influences of cyclone intensity, movement, velocity, and shape on the configuration of these profiles.

  5. Tsunami Lead Wave Reconstruction Based on Noisy Sea Surface Height Measurements

    Science.gov (United States)

    Yu, Kegen

    2016-06-01

    This paper presents a Tsunami lead wave reconstruction method using noisy sea surface height (SSH) measurements such as observed by a satellite-carried GNSS reflectometry (GNSS-R) sensor. It is proposed to utilize wavelet theory to mitigate the strong noise in the GNSS-R based SSH measurements. Through extracting the noise components by high-pass filters at decomposition stage and shrinking the noise by thresholding prior to reconstruction, the noise is greatly reduced. Real Tsunami data based simulation results demonstrate that in presence of SSH measurement error of standard deviation 50 cm the accuracy in terms of root mean square error (RMSE) of the lead wave height (true value 145.5 cm) and wavelength (true value 592.0 km) estimation is 21.5 cm and 56.2 km, respectively. The results also show that the proposed wavelet based method considerably outperforms the Kalman filter based method on average. The results demonstrate that the proposed wave reconstruction approach has the potential for Tsunami detection and parameter estimation to assist in achieving reliable Tsunami warning.

  6. TSUNAMI LEAD WAVE RECONSTRUCTION BASED ON NOISY SEA SURFACE HEIGHT MEASUREMENTS

    Directory of Open Access Journals (Sweden)

    K. Yu

    2016-06-01

    Full Text Available This paper presents a Tsunami lead wave reconstruction method using noisy sea surface height (SSH measurements such as observed by a satellite-carried GNSS reflectometry (GNSS-R sensor. It is proposed to utilize wavelet theory to mitigate the strong noise in the GNSS-R based SSH measurements. Through extracting the noise components by high-pass filters at decomposition stage and shrinking the noise by thresholding prior to reconstruction, the noise is greatly reduced. Real Tsunami data based simulation results demonstrate that in presence of SSH measurement error of standard deviation 50 cm the accuracy in terms of root mean square error (RMSE of the lead wave height (true value 145.5 cm and wavelength (true value 592.0 km estimation is 21.5 cm and 56.2 km, respectively. The results also show that the proposed wavelet based method considerably outperforms the Kalman filter based method on average. The results demonstrate that the proposed wave reconstruction approach has the potential for Tsunami detection and parameter estimation to assist in achieving reliable Tsunami warning.

  7. Estimation of sea surface wave height from Bhaskara II SAMIR data

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, M.V.; Viswambharan, N.K.; Rao, L.V.G.

    from R V Gaveshani and visual observations from other ships as reported in IDWR) are available. Using this, an attempt has been made to obtain an empirical relation between brightness temperature and significant wave height. Linear correlation between...

  8. An atmosphere-wave regional coupled model: improving predictions of wave heights and surface winds in the southern North Sea

    Science.gov (United States)

    Wahle, Kathrin; Staneva, Joanna; Koch, Wolfgang; Fenoglio-Marc, Luciana; Ho-Hagemann, Ha T. M.; Stanev, Emil V.

    2017-04-01

    The coupling of models is a commonly used approach when addressing the complex interactions between different components of earth systems. We demonstrate that this approach can result in a reduction of errors in wave forecasting, especially in dynamically complicated coastal ocean areas, such as the southern part of the North Sea - the German Bight. Here, we study the effects of coupling of an atmospheric model (COSMO) and a wind wave model (WAM), which is enabled by implementing wave-induced drag in the atmospheric model. The numerical simulations use a regional North Sea coupled wave-atmosphere model as well as a nested-grid high-resolution German Bight wave model. Using one atmospheric and two wind wave models simultaneously allows for study of the individual and combined effects of two-way coupling and grid resolution. This approach proved to be particularly important under severe storm conditions as the German Bight is a very shallow and dynamically complex coastal area exposed to storm floods. The two-way coupling leads to a reduction of both surface wind speeds and simulated wave heights. In this study, the sensitivity of atmospheric parameters, such as wind speed and atmospheric pressure, to the wave-induced drag, in particular under storm conditions, and the impact of two-way coupling on the wave model performance, is quantified. Comparisons between data from in situ and satellite altimeter observations indicate that two-way coupling improves the simulation of wind and wave parameters of the model and justify its implementation for both operational and climate simulations.

  9. Frequency content of sea surface height variability from internal gravity waves to mesoscale eddies

    Science.gov (United States)

    Savage, Anna C.; Arbic, Brian K.; Richman, James G.; Shriver, Jay F.; Alford, Matthew H.; Buijsman, Maarten C.; Thomas Farrar, J.; Sharma, Hari; Voet, Gunnar; Wallcraft, Alan J.; Zamudio, Luis

    2017-03-01

    High horizontal-resolution (1/12.5° and 1/25°) 41-layer global simulations of the HYbrid Coordinate Ocean Model (HYCOM), forced by both atmospheric fields and the astronomical tidal potential, are used to construct global maps of sea surface height (SSH) variability. The HYCOM output is separated into steric and nonsteric and into subtidal, diurnal, semidiurnal, and supertidal frequency bands. The model SSH output is compared to two data sets that offer some geographical coverage and that also cover a wide range of frequencies—a set of 351 tide gauges that measure full SSH and a set of 14 in situ vertical profilers from which steric SSH can be calculated. Three of the global maps are of interest in planning for the upcoming Surface Water and Ocean Topography (SWOT) two-dimensional swath altimeter mission: (1) maps of the total and (2) nonstationary internal tidal signal (the latter calculated after removing the stationary internal tidal signal via harmonic analysis), with an average variance of 1.05 and 0.43 cm2, respectively, for the semidiurnal band, and (3) a map of the steric supertidal contributions, which are dominated by the internal gravity wave continuum, with an average variance of 0.15 cm2. Stationary internal tides (which are predictable), nonstationary internal tides (which will be harder to predict), and nontidal internal gravity waves (which will be very difficult to predict) may all be important sources of high-frequency "noise" that could mask lower frequency phenomena in SSH measurements made by the SWOT mission.

  10. UAS Observations of Polynya Wave Height and Surface Temperature During the September 2012 Terra Nova Bay, Antarctica Field Campaign

    Science.gov (United States)

    Bradley, A. C.; Palo, S. E.; Knuth, S. L.; Cassano, J. J.

    2013-12-01

    A 2012 campaign flew Aerosonde unmanned aerial systems (UASs) over the Terra Nova Bay polynya in Antarctica to study air-sea fluxes in this environment. Sea ice forms over the open water of the polynya and is pushed out from the coast by strong offshore winds, resulting in significant heat and moisture flux out of the area. The Aerosonde UAS payloads contained a number of instruments, including the Everest IR surface temperature sensor and the CULPIS LIDAR profilometer system, for the purpose of measuring these fluxes. Wave heights were extracted from the CULPIS data and compared to wind speed measurements collected onboard the Aerosonde and to wind speed measurements from AWS stations upwind. Wave height showed minimal correlation to the co-located UAS wind speed measurements, but high geographic predictability. High moisture flux out of polynyas often results in cloud formation, limiting the utility of satellite-based IR measurement of surface temperatures and ice extent. This study compares sea surface temperature measurements from the Everest instrument to the MODIS sea ice surface temperature data product. Surface temperature measurements from the Everest system show high agreement with concurrent MODIS data over a variety of ice surface conditions. The sample time of the UAV instrument relative to the time of the MODIS data provides an estimate of the time rate of change of the surface temperatures of different ice surface types (thin ice, thick ice, open water), which is related to air temperature.

  11. Encounter Probability of Significant Wave Height

    DEFF Research Database (Denmark)

    Liu, Z.; Burcharth, H. F.

    The determination of the design wave height (often given as the significant wave height) is usually based on statistical analysis of long-term extreme wave height measurement or hindcast. The result of such extreme wave height analysis is often given as the design wave height corresponding to a c...

  12. Trends in significant wave height and surface wind speed in the China Seas between 1988 and 2011

    Science.gov (United States)

    Zheng, Chongwei; Zhang, Ren; Shi, Weilai; Li, Xin; Chen, Xuan

    2017-10-01

    Wind and waves are key components of the climate system as they drive air-sea interactions and influence weather systems and atmospheric circulation. In marine environments, understanding surface wind and wave fields and their evolution over time is important for conducting safe and efficient human activities, such as navigation and engineering. This study considers long-term trends in the sea surface wind speed (WS) and significant wave height (SWH) in the China Seas over the period 1988-2011 using the Cross-Calibrated Multi-Platform (CCMP) ocean surface wind product and a 24-year hindcast wave dataset obtained from the WAVEWATCH-III (WW3) wave model forced with CCMP winds. The long-term trends in WS and SWH in the China Seas are analyzed over the past 24 years to provide a reference point from which to assess future climate change and offshore wind and wave energy resource development in the region. Results demonstrate that over the period 1988-2011 in the China Seas: 1) WS and SWH showed a significant increasing trend of 3.38 cm s-1 yr-1 and 1.52 cm yr-1, respectively; 2) there were notable regional differences in the long-term trends of WS and SWH; 3) areas with strong increasing trends were located mainly in the middle of the Tsushima Strait, the northern and southern areas of the Taiwan Strait, and in nearshore regions of the northern South China Sea; and 4) the long-term trend in WS was closely associated with El Niño and a significant increase in the occurrence of gale force winds in the region.

  13. Encounter Probability of Individual Wave Height

    DEFF Research Database (Denmark)

    Liu, Z.; Burcharth, H. F.

    1998-01-01

    wave height corresponding to a certain exceedence probability within a structure lifetime (encounter probability), based on the statistical analysis of long-term extreme significant wave height. Then the design individual wave height is calculated as the expected maximum individual wave height...... associated with the design significant wave height, with the assumption that the individual wave heights follow the Rayleigh distribution. However, the exceedence probability of such a design individual wave height within the structure lifetime is unknown. The paper presents a method for the determination...... of the design individual wave height corresponding to an exceedence probability within the structure lifetime, given the long-term extreme significant wave height. The method can also be applied for estimation of the number of relatively large waves for fatigue analysis of constructions....

  14. Projected changes, climate change signal, and uncertainties in the CMIP5-based projections of ocean surface wave heights

    Science.gov (United States)

    Wang, Xiaolan; Feng, Yang; Swail, Val R.

    2016-04-01

    Ocean surface waves can be major hazards in coastal and offshore activities. However, wave observations are available only at limited locations and cover only the recent few decades. Also, there exists very limited information on ocean wave behavior in response to climate change, because such information is not simulated in current global climate models. In a recent study, we used a multivariate regression model with lagged dependent variable to make statistical global projections of changes in significant wave heights (Hs) using mean sea level pressure (SLP) information from 20 CMIP5 climate models for the twenty-first century. The statistical model was calibrated and validated using the ERA-Interim reanalysis of Hs and SLP for the period 1981-2010. The results show Hs increases in the tropics (especially in the eastern tropical Pacific) and in southern hemisphere high-latitudes. Under the projected 2070-2099 climate condition of the RCP8.5 scenario, the occurrence frequency of the present-day one-in-10-year extreme wave heights is likely to double or triple in several coastal regions around the world (e.g., the Chilean coast, Gulf of Oman, Gulf of Bengal, Gulf of Mexico). More recently, we used the analysis of variance approaches to quantify the climate change signal and uncertainty in multi-model ensembles of statistical Hs simulations globally, which are based on the CMIP5 historical, RCP4.5 and RCP8.5 forcing scenario simulations of SLP. In a 4-model 3-run ensemble, the 4-model common signal of climate change is found to strengthen over time, as would be expected. For the historical followed by RCP8.5 scenario, the common signal in annual mean Hs is found to be significant over 16.6%, 55.0% and 82.2% of the area by year 2005, 2050 and 2099, respectively. For the annual maximum, the signal is much weaker. The signal is strongest in the eastern tropical Pacific, featuring significant increases in both the annual mean and maximum of Hs in this region. The climate

  15. Statistical distribution of nonlinear random wave height

    Institute of Scientific and Technical Information of China (English)

    HOU; Yijun; GUO; Peifang; SONG; Guiting; SONG; Jinbao; YIN; Baoshu; ZHAO; Xixi

    2006-01-01

    A statistical model of random wave is developed using Stokes wave theory of water wave dynamics. A new nonlinear probability distribution function of wave height is presented. The results indicate that wave steepness not only could be a parameter of the distribution function of wave height but also could reflect the degree of wave height distribution deviation from the Rayleigh distribution. The new wave height distribution overcomes the problem of Rayleigh distribution that the prediction of big wave is overestimated and the general wave is underestimated. The prediction of small probability wave height value of new distribution is also smaller than that of Rayleigh distribution. Wave height data taken from East China Normal University are used to verify the new distribution. The results indicate that the new distribution fits the measurements much better than the Rayleigh distribution.

  16. Development and Calibration of Two and Four Wire Water Surface Wave Height Measurement Systems

    Science.gov (United States)

    1992-12-01

    upwind of the ruler. The dust travel time between the two points was measured using a Casio Alarm Chrono G-Shock digital watch. The measured surface...7ýz Fxdxy I L-cs Hz 1 141K~ b&4y I At Wifi , o~VDff, I ftV’he. ’Ot (00#4: rft S*A Figure 4.14. Tank Q capacitance system measurement plot. 101 X-2. 1.2

  17. The seasonal variations in the significant wave height and sea surface wind speed of the China’s seas

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chongwei; PAN Jing; TAN Yanke; GAO Zhansheng; RUI Zhenfeng; CHEN Chaohui

    2015-01-01

    Long-term variations in a sea surface wind speed (WS) and a significant wave height (SWH) are associated with the global climate change, the prevention and mitigation of natural disasters, and an ocean resource exploitation, and other activities. The seasonal characteristics of the long-term trends in China’s seas WS and SWH are determined based on 24 a (1988–2011) cross-calibrated, multi-platform (CCMP) wind data and 24 a hindcast wave data obtained with the WAVEWATCH-III (WW3) wave model forced by CCMP wind data. The results show the following. (1) For the past 24 a, the China’s WS and SWH exhibit a significant increasing trend as a whole, of 3.38 cm/(s·a) in the WS, 1.3 cm/a in the SWH. (2) As a whole, the increasing trend of the China’s seas WS and SWH is strongest in March-April-May (MAM) and December-January-February (DJF), followed by June-July-August (JJA), and smallest in September-October-November (SON). (3) The areal extent of significant increases in the WS was largest in MAM, while the area decreased in JJA and DJF;the smallest area was apparent in SON. In contrast to the WS, almost all of China’s seas exhibited a significant increase in SWH in MAM and DJF;the range was slightly smaller in JJA and SON. The WS and SWH in the Bohai Sea, the Yellow Sea, East China Sea, the Tsushima Strait, the Taiwan Strait, the northern South China Sea, the Beibu Gulf, and the Gulf of Thailand exhibited a significant increase in all seasons. (4) The variations in China’s seas SWH and WS depended on the season. The areas with a strong increase usually appeared in DJF.

  18. Challenges in Defining Tsunami Wave Heights

    Science.gov (United States)

    Dunbar, Paula; Mungov, George; Sweeney, Aaron; Stroker, Kelly; Arcos, Nicolas

    2017-08-01

    The National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) and co-located World Data Service for Geophysics maintain the global tsunami archive consisting of the historical tsunami database, imagery, and raw and processed water level data. The historical tsunami database incorporates, where available, maximum wave heights for each coastal tide gauge and deep-ocean buoy that recorded a tsunami signal. These data are important because they are used for tsunami hazard assessment, model calibration, validation, and forecast and warning. There have been ongoing discussions in the tsunami community about the correct way to measure and report these wave heights. It is important to understand how these measurements might vary depending on how the data were processed and the definition of maximum wave height. On September 16, 2015, an 8.3 M w earthquake located 48 km west of Illapel, Chile generated a tsunami that was observed all over the Pacific region. We processed the time-series water level data for 57 coastal tide gauges that recorded this tsunami and compared the maximum wave heights determined from different definitions. We also compared the maximum wave heights from the NCEI-processed data with the heights reported by the NOAA Tsunami Warning Centers. We found that in the near field different methods of determining the maximum tsunami wave heights could result in large differences due to possible instrumental clipping. We also found that the maximum peak is usually larger than the maximum amplitude (½ peak-to-trough), but the differences for the majority of the stations were definition (maximum peak or amplitude) would have validated the forecasts issued by the NOAA Tsunami Warning Centers. Since there is currently only one field in the NCEI historical tsunami database to store the maximum tsunami wave height for each tide gauge and deep-ocean buoy, NCEI will consider adding an additional field for the maximum

  19. Tsunami focusing and leading wave height

    Science.gov (United States)

    Kanoglu, Utku

    2016-04-01

    Field observations from tsunami events show that sometimes the maximum tsunami amplitude might not occur for the first wave, such as the maximum wave from the 2011 Japan tsunami reaching to Papeete, Tahiti as a fourth wave 72 min later after the first wave. This might mislead local authorities and give a wrong sense of security to the public. Recently, Okal and Synolakis (2016, Geophys. J. Int. 204, 719-735) discussed "the factors contributing to the sequencing of tsunami waves in the far field." They consider two different generation mechanisms through an axial symmetric source -circular plug; one, Le Mehaute and Wang's (1995, World Scientific, 367 pp.) formalism where irritational wave propagation is formulated in the framework of investigating tsunamis generated by underwater explosions and two, Hammack's formulation (1972, Ph.D. Dissertation, Calif. Inst. Tech., 261 pp., Pasadena) which introduces deformation at the ocean bottom and does not represent an immediate deformation of the ocean surface, i.e. time dependent ocean surface deformation. They identify the critical distance for transition from the first wave being largest to the second wave being largest. To verify sequencing for a finite length source, Okal and Synolakis (2016) is then used NOAA's validated and verified real time forecasting numerical model MOST (Titov and Synolakis, 1998, J. Waterw. Port Coast. Ocean Eng., 124, 157-171) through Synolakis et al. (2008, Pure Appl. Geophys. 165, 2197-2228). As a reference, they used the parameters of the 1 April 2014 Iquique, Chile earthquake over real bathymetry, variants of this source (small, big, wide, thin, and long) over a flat bathymetry, and 2010 Chile and 211 Japan tsunamis over both real and flat bathymetries to explore the influence of the fault parameters on sequencing. They identified that sequencing more influenced by the source width rather than the length. We extend Okal and Synolakis (2016)'s analysis to an initial N-wave form (Tadepalli

  20. Correlation techniques and measurements of wave-height statistics

    Science.gov (United States)

    Guthart, H.; Taylor, W. C.; Graf, K. A.; Douglas, D. G.

    1972-01-01

    Statistical measurements of wave height fluctuations have been made in a wind wave tank. The power spectral density function of temporal wave height fluctuations evidenced second-harmonic components and an f to the minus 5th power law decay beyond the second harmonic. The observations of second harmonic effects agreed very well with a theoretical prediction. From the wave statistics, surface drift currents were inferred and compared to experimental measurements with satisfactory agreement. Measurements were made of the two dimensional correlation coefficient at 15 deg increments in angle with respect to the wind vector. An estimate of the two-dimensional spatial power spectral density function was also made.

  1. Statistical analysis on extreme wave height

    Digital Repository Service at National Institute of Oceanography (India)

    Teena, N.V.; SanilKumar, V.; Sudheesh, K.; Sajeev, R.

    the distributions fitted to the GEV with annual maximum approach and GPD with peaks over threshold approach have indicated that both GEV and GPD models gave similar or comparable wave height for the study area since there is no multiple storm event in a year...

  2. Estimation of wind speed and wave height during cyclones

    Digital Repository Service at National Institute of Oceanography (India)

    SanilKumar, V.; Mandal, S.; AshokKumar, K.

    reported by ships were comparable. Empirical expressions relating wind speed, wave height and wave period to storm parameters were derived. The design wave height for different return periods was obtained by fitting a two-parameter Weibull distribution...

  3. Nonlinear surface waves over topography

    NARCIS (Netherlands)

    Janssen, T.T.

    2006-01-01

    As ocean surface waves radiate into shallow coastal areas and onto beaches, their lengths shorten, wave heights increase, and the wave shape transforms from nearsinusoidal to the characteristic saw-tooth shapes at the onset of breaking; in the ensuing breaking process the wave energy is cascaded to

  4. Statistical distribution of nonlinear random wave height in shallow water

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Here we present a statistical model of random wave,using Stokes wave theory of water wave dynamics,as well as a new nonlinear probability distribution function of wave height in shallow water.It is more physically logical to use the wave steepness of shallow water and the factor of shallow water as the parameters in the wave height distribution.The results indicate that the two parameters not only could be parameters of the distribution function of wave height but also could reflect the degree of wave height distribution deviation from the Rayleigh distribution.The new wave height distribution overcomes the problem of Rayleigh distribution that the prediction of big wave is overestimated and the general wave is underestimated.The prediction of small probability wave height value of new distribution is also smaller than that of Rayleigh distribution.The effect of wave steepness in shallow water is similar to that in deep water;but the factor of shallow water lowers the wave height distribution of the general wave with the reduced factor of wave steepness.It also makes the wave height distribution of shallow water more centralized.The results indicate that the new distribution fits the in situ measurements much better than other distributions.

  5. Trends in surface wind speed and significant wave height as revealed by ERA-Interim wind wave hindcast in the Central Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Shanas, P.R.; SanilKumar, V.

    The Arabian Sea and Bay of Bengal (BoB) regions are special interested sea areas in the Northern Hemisphere with large seasonal variability. This study focused on the long-term wind and wave in the central BoB from 1979 to 2012 based on the ECMWF...

  6. Synthesizing Waves from Animated Height Fields

    DEFF Research Database (Denmark)

    Nielsen, Michael Bang; Söderström, Andreas; Bridson, Robert

    2013-01-01

    for synthesizing Fourier-based ocean waves that match a previs input, allowing artists to quickly enhance the input wave animation with additional higher-frequency detail that moves consistently with the coarse waves, tweak the wave shapes to flatten troughs and sharpen peaks if desired (as is characteristic...

  7. Prediction of Extreme Significant Wave Height from Daily Maxima

    Institute of Scientific and Technical Information of China (English)

    刘德辅; 李华军; 温书勤; 宋艳; 王树青

    2001-01-01

    For prediction of the extreme significant wave height in the ocean areas where long term wave data are not available, the empirical method of extrapolating short term data (1 ~ 3 years) is used in design practice. In this paper two methods are proposed to predict extreme significant wave height based on short-term daily maxima. According to the daa recorded by the Oceanographic Station of Liaodong Bay at the Bohai Sea, it is supposed that daily maximum wave heights are statistically independent. The data show that daily maximum wave heights obey log-normal distribution, and that the numbers of daily maxima vary from year to year, obeying binomial distribution. Based on these statistical characteristics, the binomial-log-normal compound extremum distribution is derived for prediction of extreme significant wave heights (50~ 100 years). For examination of its accuracy and validity, the prediction of extreme wave heights is based on 12 years′ data at this station, and based on each 3 years′ data respectively. The results show that with consideration of confidence intervals, the predicted wave heights based on 3 years′ data are very close to those based on 12 years′data. The observed data in some ocean areas in the Atlantic Ocean and the North Sea show it is not correct to assume that daily maximum wave heights are statistically independent; they are subject to Markov chain condition, obeying log-normal distribution. In this paper an analytical method is derived to predict extreme wave heights in these cases. A comparison of the computations shows that the difference between the extreme wave heights based on the assumption that daily maxima are statistically independent and that they are subject to Markov Chain condition is smaller than 10%.

  8. The difference between the joint probability distributions of apparent wave heights and periods and individual wave heights and periods

    Institute of Scientific and Technical Information of China (English)

    ZHENGGuizhen; JIANGXiulan; HANShuzong

    2004-01-01

    The joint distribution of wave heights and periods of individual waves is usually approximated by the joint distribution of apparent wave heights and periods. However there is difference between them. This difference is addressed and the theoretical joint distributions of apparent wave heights and periods due to Longuet-Higgins and Sun are modified to give more reasonable representations of the joint distribution of wave heights and periods of individual waves. The modification has overcome an inherent drawback of these joint PDFs that the mean wave period is infinite. A comparison is made between the modified formulae and the field data of Goda, which shows that the new formulae consist with the measurement better than their original counterparts.

  9. Wave Height Distribution Observed by Ships in the North Atlantic

    DEFF Research Database (Denmark)

    Olsen, Anders Smærup; Schrøter, Carsten; Jensen, Jørgen Juncher

    2005-01-01

    The analysis of almost 25000 observation of the wave height from ships in the North Atlantic shows that the encountered wave height distribution is significantly lower than the distribution provided by the classification societies for structural assessment. The joint probability distribution for ...... that the ship will maintain the service speed even in relatively severe sea. The distribution derived could be used to incorporate the effect of weather routing in a long term analysis of the wave loads on a ship....

  10. Synthesizing Waves from Animated Height Fields

    DEFF Research Database (Denmark)

    Nielsen, Michael Bang; Söderström, Andreas; Bridson, Robert

    2013-01-01

    Computer animated ocean waves for feature films are typically carefully choreographed to match the vision of the director and to support the telling of the story. The rough shape of these waves is established in the previsualization (previs) stage, where artists use a variety of modeling tools...

  11. Wave height possibility distribution characteristics of significant wave height in China Sea based on multi-satellite grid data

    Science.gov (United States)

    Han, W.; Yang, J.

    2016-11-01

    This paper discusses the group of wave height possibility distribution characteristics of significant wave height in China Sea based on multi-satellite grid data, the grid SWH data merges six satellites (TOPEX/Poseidon, Jason-1/2, ENVISAT, Cryosat-2, HY-2A) corrected satellite altimeter data into the global SWH grid data in 2000∼2015 using Inverse Distance Weighting Method. Comparing the difference of wave height possibility distribution of two schemes that scheme two includes all of 6 satellite data and scheme one includes all of other 5 satellite data except HY-2A in two wave height interval, the first interval is [0,25) m, the second interval is [4,25) m, finding that two schemes have close wave height probability distribution and the probability change trend, there are difference only in interval [0.4, 1.8) m and the possibility in this interval occupies over 70%; then mainly discussing scheme two, finding that the interval of greatest wave height possibility is [0.6, 3) m, and the wave height possibility that the SWH is greater than 4m is less than 0.18%.

  12. Multiresolution wavelet-ANN model for significant wave height forecasting.

    Digital Repository Service at National Institute of Oceanography (India)

    Deka, P.C.; Mandal, S.; Prahlada, R.

    Hybrid wavelet artificial neural network (WLNN) has been applied in the present study to forecast significant wave heights (Hs). Here Discrete Wavelet Transformation is used to preprocess the time series data (Hs) prior to Artificial Neural Network...

  13. A simple method for retrieving significant wave height from Dopplerized X-band radar

    Science.gov (United States)

    Carrasco, Ruben; Streßer, Michael; Horstmann, Jochen

    2017-02-01

    Retrieving spectral wave parameters such as the peak wave direction and wave period from marine radar backscatter intensity is very well developed. However, the retrieval of significant wave height is difficult because the radar image spectrum (a backscatter intensity variance spectrum) has to be transferred to a wave spectrum (a surface elevation variance spectrum) using a modulation transfer function (MTF) which requires extensive calibration for each individual radar setup. In contrast to the backscatter intensity, the Doppler velocity measured by a coherent radar is induced by the radial velocity (or line-of-sight velocity) of the surface scattering and its periodic component is mainly the contribution of surface waves. Therefore, the variance of the Doppler velocity can be utilized to retrieve the significant wave height. Analyzing approximately 100 days of Doppler velocity measurements of a coherent-on-receive radar operating at X-band with vertical polarization in transmit and receive, a simple relation was derived and validated to retrieve significant wave heights. Comparison to wave measurements of a wave rider buoy as well as an acoustic wave and current profiler resulted in a root mean square error of 0.24 m with a bias of 0.08 m. Furthermore, the different sources of error are discussed and investigated.

  14. Wave Height Distribution for Spilling Waves in and outside the Surf Zone

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The wave characteristics affecting coastal sediment transport include wave height, wave period and breaking wave direction. Wave height is a critical factor in determining the amount of sediment transport in the coastal area. The force of sediment transport is much more intense under breaking waves than under non-breaking waves. Breaking waves exhibit various patterns, principally depending on the incident wave steepness and the beach slope. Based on the equations of conservation of mass, momentum and energy, a theoretical model for wave deformation in and outside the surf zone was obtained, which is used to calculate the wave shoaling, wave set-up and setdown and wave height distributions in and outside the surf zone. The analysis and comparison were made about the breaking point location and the wave height decay caused by the wave breaking and the bottom friction. Flume experiments relating to the spilling wave height distribution across the surf zone were conducted to verify the theoretical model. Advanced wave maker, data sampling devices and data processing system were utilized in the flume experiments with a slope covered by sands of different diameters to facilitate the observation and research on the wave transformation and breaking. The agreement between the theoretical and experimental results is good.

  15. Small-scale open ocean currents have large effects on wind wave heights

    Science.gov (United States)

    Ardhuin, Fabrice; Gille, Sarah T.; Menemenlis, Dimitris; Rocha, Cesar B.; Rascle, Nicolas; Chapron, Bertrand; Gula, Jonathan; Molemaker, Jeroen

    2017-06-01

    Tidal currents and large-scale oceanic currents are known to modify ocean wave properties, causing extreme sea states that are a hazard to navigation. Recent advances in the understanding and modeling capability of open ocean currents have revealed the ubiquitous presence of eddies, fronts, and filaments at scales 10-100 km. Based on realistic numerical models, we show that these structures can be the main source of variability in significant wave heights at scales less than 200 km, including important variations down to 10 km. Model results are consistent with wave height variations along satellite altimeter tracks, resolved at scales larger than 50 km. The spectrum of significant wave heights is found to be of the order of 70>>2/>(g2>>2>) times the current spectrum, where >> is the spatially averaged significant wave height, >> is the energy-averaged period, and g is the gravity acceleration. This variability induced by currents has been largely overlooked in spite of its relevance for extreme wave heights and remote sensing.Plain Language SummaryWe show that the variations in currents at scales 10 to 100 km are the main source of variations in wave heights at the same scales. Our work uses a combination of realistic numerical models for currents and waves and data from the Jason-3 and SARAL/AltiKa satellites. This finding will be of interest for the investigation of extreme wave heights, remote sensing, and air-sea interactions. As an immediate application, the present results will help constrain the error budget of the up-coming satellite missions, in particular the Surface Water and Ocean Topography (SWOT) mission, and decide how the data will have to be processed to arrive at accurate sea level and wave measurements. It will also help in the analysis of wave measurements by the CFOSAT satellite.

  16. Estimation of Design Wave Heights for Coastal Sea Areas

    Institute of Scientific and Technical Information of China (English)

    LI Luping; HUANG Peiji; CHEN Xueying

    2000-01-01

    Based on historical wind fields in the Bohai Sea, a sequence of annual extremal wave heightsis produced with numerical wave models for deep-water and shallow water. The design wave heights with different return periods for the nearest deep-water point and for the shallow water point are estimated on the basis of p-Ⅲ type, Weibull distribution, and Gumbel distribution; and the corresponding values for the shallow water point are also estimated based on the HISWA model with the input of design wave heightsfor the nearest deep-water point. Comparisons between design wave heights for the shallow water point estimated on the basis of both distribution functions are HISWA model show that the results from differentdistribution functions scatter considerably, and influenced strongly by return periods; however, the results from the HISWA model are convergent, that is, the influence of the design wave heights estimated with different distribution functions for deep water is weakened, and the estimated values decrease for long returnperiods and increase for short return periods. Therefore, the numerical wave model gives a more stable result in shallow water design wave estimation because of the consideration of the effect of physical processes which occur in shallow water.

  17. Geosat altimeter derived sea surface wind speeds and significant wave heights for the north Indian Ocean and their comparison with in situ data

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Vaithiyanathan, R.; Almeida, A.M.; Santanam, K.; Rao, L.V.G.; Sarkar, A.; Kumar, R.; Gairola, R.M.; Gohil, B.S.

    coded maps, showing the distribution of mean monthly values of wind and wave parameters over 2.5 degrees square grids. Altimeter derived wind and wave parameters are compared with (1) winds and waves obtained through ships of opportunity and documented...

  18. Height-dependent Refraction of A Global EUV Wave and Its Associated Sympathetic Eruptions

    Science.gov (United States)

    Liu, Wei; Ofman, Leon; Downs, Cooper; Schrijver, Karel

    2014-06-01

    The height dependence of global extreme-ultraviolet (EUV) waves in the solar corona, especially of their wave-like behaviors such as transmission and reflection, is critical to understanding their physical nature. Prior observations of such behaviors, when detected on the solar disk, were compromised because height-dependent information is lost due to the line-of-sight projection from a top-down view. We report a global EUV wave on the limb observed by SDO/AIA from a side-view that evidently shows height-dependent transmission and refraction. As the wave travels through an active region, the orientation of the low-corona wave front changes from a forward inclination toward the solar surface to a backward inclination. This indicates that the EUV wave speed is lower at higher altitudes, which is expected because of the rapid drop with height of the Alfven and fast-mode speeds in active regions, as predicted by MHD models. When traveling into the active region, the EUV wave speed in the low corona increases from ~600 km/s to ~900 km/s. In addition, in the neighborhood of the active region, sympathetic eruptions of local coronal structures take place sequentially upon the wave impact and may appear as wave reflection. Understanding propagation behaviors of global EUV waves brings us one step closer to fully utilizing them for seismological diagnostics of the global corona, such as mapping the spatial distribution of the Alfven speed and magnetic field strength.

  19. Experimental Investigation of Wave Heights in A Directional Wave Field Through Image Sequences

    Institute of Scientific and Technical Information of China (English)

    Chung-Ren CHOU; Teng-Wei LIN; Ruey-Syan SHIH; John Z. YIM

    2005-01-01

    Measurements of wave heights with image sequences from a Charged Coupled Device(CCD) camera were made. Sinusoidal, as well as unidirectional and directional, waves were used for the experiments. A transfer function was obtained by calibration of the magnitudes of the gray values of the images against the results of wave gauge measurements for directional waves. With this transfer function, wave heights for regular waves were deduced. It is shown that the average relative errors are smaller than 16% for both unidirectional and directional waves.

  20. Wave Prediction Model To Study On The Wave Height Variation In Terengganu Coast Of Malaysia

    Directory of Open Access Journals (Sweden)

    Nur Amalina Abdul Latif

    2015-08-01

    Full Text Available Abstract In this study the significant wave height at the Terengganu and the change of wave height at Kuala Terengganu to Merang shoreline were simulated by using the 2D Near-Shore Wave 2D NSW model. The significant wave height by the 2D NSW model at Kuala Terengganu to Merang shoreline from 2008-2012 were simulated. The model was forced by ECMWF European Centre for Medium Range Weather Forecast data. The simulated significant wave height by the 2D NSW model at Airport Kuala Terengganu AWAC station was compared with the observed significant wave height. The mean annual significant wave height indicate the higher wave height with average mean value in a range of 1.08-1.10 m in Kuala Terengganu to Batu Rakit area and lower in Merang area with average mean value in a range of 0.74 m. The detailed 5 years simulation period demonstrates that the strong variability of wave height exists during North-East monsoon. The findings of this study could be useful for the erosive calculation shoreline protection and coastal zone management activities.

  1. A new statistical model of wave heights based on the concept of wave breaking critical zone

    Institute of Scientific and Technical Information of China (English)

    YANG Jiaxuan; LI Xunqiang; ZHU Shouxian; ZHANG Wenjing; WANG Lei

    2015-01-01

    When waves propagate from deep water to shallow water, wave heights and steepness increase and then waves roll back and break. This phenomenon is called surf. Currently, the present statistical calculation model of surf was derived mainly from the wave energy conservation equation and the linear wave dispersion relation, but it cannot reflect accurately the process which is a rapid increasing in wave height near the broken point. So, the concept of a surf breaking critical zone is presented. And the nearshore is divided as deep water zone, shallow water zone, surf breaking critical zone and after breaking zone. Besides, the calculation formula for the height of the surf breaking critical zone has founded based on flume experiments, thereby a new statistical calculation model on the surf has been established. Using the new model, the calculation error of wave height maximum is reduced from 17.62% to 6.43%.

  2. Dyakonov surface waves

    DEFF Research Database (Denmark)

    Takayama, Osamu; Crasovan, Lucian Cornel; Johansen, Steffen Kjær;

    2008-01-01

    The interface of two semi-infinite media, where at least one of them is a birefringent crystal, supports a special type of surface wave that was predicted theoretically by D'yakonov in 1988. Since then, the properties of such waves, which exist in transparent media only under very special......, the existence of these surface waves in specific material examples is analyzed, discussing the challenge posed by their experimental observation....

  3. Preliminary investigation on the relation between maximum wave height and wave spectra

    Science.gov (United States)

    Tao, Aifeng; Wen, Cheng; Wu, Yuqing; Wu, Haoran; Li, Shuo; Cao, Guangsui

    2016-04-01

    The maximum wave height is important not only for the determination of design wave parameters but also for the marine disaster defense. While it cannot be predicted straightforwardly at present, since the general numerical models for wave forecasting are all based on phase averaged spectra model. Then it becomes very useful to make clear the relationship between the maximum wave height and wave spectra parameters, such as average wave steepness, spectra width and spectra type, such as one single peak spectra or multi peaks spectra. In order to perform this research procedure, plenty of observed wave data are required. We collected ten years wave data measured from a ship in North Sea, one year wave pressure data from nine points around Korea, four years buoy data from three points along Chinese coast. The preliminary investigation results on the relations between maximum waves and spectra via the mention observed data will be present here.

  4. Dependence of Wave Height Distribution on Spectral Width and Wave Steepness

    Institute of Scientific and Technical Information of China (English)

    文凡; 吴自库; 吕红民

    2004-01-01

    In this paper experimental wind wave data are analyzed. It is found that differences in spectral width will give rise to differences in wave height distribution. The effect of spectral width on the distribution is mainly in the high wave range.The effect of wave steepness is in low, medium and high wave ranges. In the high wave range the effect of spectral width is comparable to that of wave steepness. Differences in spectral width in the observations may give rise to discrepancies in the result when wave steepness is the only parameter in the distribution.

  5. Space-time extreme wind waves: Analysis and prediction of shape and height

    Science.gov (United States)

    Alvise, Benetazzo; Francesco, Barbariol; Filippo, Bergamasco; Sandro, Carniel; Mauro, Sclavo

    2017-05-01

    In this study, we present the analysis of the temporal profile and height of space-time (ST) extreme wind waves. Wave data were gathered from an observational ST sample of sea surface elevations collected during an active sea state, and they were examined to detect the highest waves (exceeding the rogue wave threshold) of specific 3D wave groups close to the apex of their development. Two different investigations are conducted. Firstly, local maximum elevations of the groups are examined within the framework of statistical models for ST extreme waves, and compared with observations and predictions of maxima derived by one-point time series of sea surface elevations. Secondly, the temporal profile near the maximum wave crests is analyzed and compared with the expectations of the linear and second-order nonlinear extension of the Quasi-Determinism (QD) theory. Our goal is to verify, with real sea data, to what extent, one can estimate the shape and the crest-to-trough height of near-focusing large 3D wave groups using the QD and ST extreme model results. From this study, it emerges that the elevations close to the crest apex are narrowly distributed around a mean profile, whilst a larger dispersion is observed away from the maximum elevation. Yet the QD model furnishes, on average, a fair prediction of the maximum wave heights, especially when nonlinearities are taken into account. Moreover, we discuss how the combination of ST extreme and QD model predictions allows establishing, for a given sea condition, the portrait of waves with very large crest height. Our results show that these theories have the potential to be implemented in a numerical spectral model for wave extreme prediction.

  6. Auto-correlation analysis of wave heights in the Bay of Bengal

    Indian Academy of Sciences (India)

    Abhijit Sarkar; Jignesh Kshatriya; K Satheesan

    2006-04-01

    Time series observations of significant wave heights in the Bay of Bengal were subjected to auto-correlation analysis to determine temporal variability scale.The analysis indicates an exponential fall of auto-correlation in the first few hours with a decorrelation time scale of about six hours.A similar figure was found earlier for ocean surface winds.The nature of variation of auto-correlation with time lags was also found to be similar for winds and wave heights.

  7. Mapping wave heights in sea ice with Sentinel 1

    Science.gov (United States)

    Stopa, Justin; Ardhuin, Fabrice; Collard, Fabrice; Mouche, Alexis; Guitton, Gilles; Sutherland, Peter

    2016-04-01

    Sea ice plays an important role in the Earth system by regulating air-sea fluxes. These fluxes can be enhanced by the breaking of ice into floes which critically depends on wave heights propagating across the ice. Remote sensing with SAR provides a unique coverage of the polar regions but so far the measurement of wave heights has been performed routinely only for open water. The presence of ice completely changes the mechanisms by which waves make patterns in radar images. Namely, in the open ocean, the constructed images appear blurred due to the fact that the high frequency waves are unresolved by the sensor. Instead, in ice-covered seas, high frequency waves have been dissipated or scattered away, and only the low-frequency swell components are observed. Two new algorithms have been proposed by Ardhuin et al. (2015). Refining these algorithms, we analyze the intricate wave patterns captured over sea ice by Sentinel 1-A, and measure both the wave heights and directional spreading of the wave spectrum. The procedure is a two-step process which uses an estimation of the orbital vertical velocities that produce the observed image intensity. The first step is implemented when wiggly lines are present. Wiggly lines are created by the presence of two swell systems and are removed by estimating the wave orbital velocity that causes the amplitude in the wiggly line. The second step uses Fourier analysis to invert the straightened image into a velocity field. As a result we obtain a full non-linear inversion the mapping from the velocity field to the SAR intensity image. The inverted velocities can be used to obtain the wavenumber-direction spectrum. Our algorithm is applied to S1A images from the Arctic and Antarctic and discussions follow in terms of wave-ice interaction. These data will be validated using in situ measurements from the ONR Sea State DRI (Beaufort sea, 2016), and combined with numerical modeling using the WAVEWATCH III model to adjust parameterization

  8. Dyakonov surface waves

    DEFF Research Database (Denmark)

    Takayama, Osamu; Crasovan, Lucian Cornel; Johansen, Steffen Kjær

    2008-01-01

    The interface of two semi-infinite media, where at least one of them is a birefringent crystal, supports a special type of surface wave that was predicted theoretically by D'yakonov in 1988. Since then, the properties of such waves, which exist in transparent media only under very special conditi...

  9. Significant wave heights from Sentinel-1 SAR: Validation and applications

    Science.gov (United States)

    Stopa, J. E.; Mouche, A.

    2017-03-01

    Two empirical algorithms are developed for wave mode images measured from the synthetic aperture radar aboard Sentinel-1 A. The first method, called CWAVE_S1A, is an extension of previous efforts developed for ERS2 and the second method, called Fnn, uses the azimuth cutoff among other parameters to estimate significant wave heights (Hs) and average wave periods without using a modulation transfer function. Neural networks are trained using colocated data generated from WAVEWATCH III and independently verified with data from altimeters and in situ buoys. We use neural networks to relate the nonlinear relationships between the input SAR image parameters and output geophysical wave parameters. CWAVE_S1A performs well and has reduced precision compared to Fnn with Hs root mean square errors within 0.5 and 0.6 m, respectively. The developed neural networks extend the SAR's ability to retrieve useful wave information under a large range of environmental conditions including extratropical and tropical cyclones in which Hs estimation is traditionally challenging.Plain Language SummaryTwo empirical algorithms are developed to estimate integral wave parameters from high resolution synthetic aperture radar (SAR) ocean images measured from recently launched the Sentinel 1 satellite. These methods avoid the use of the complicated image to wave mapping typically used to estimate sea state parameters. In addition, we are able to estimate wave parameters that are not able to be measured using existing techniques for the Sentinel 1 satellite. We use a machine learning technique to create a model that relates the ocean image properties to geophysical wave parameters. The models are developed using data from a numerical model because of the sufficiently large sample of global ocean conditions. We then verify that our developed models perform well with respect to independently measured wave observations from other satellite sensors and buoys. We successfully created models that

  10. Analytic height correlation function of rough surfaces derived from light scattering

    CERN Document Server

    Zamani, M; Fazeli, S M; Downer, M C; Jafari, G R

    2015-01-01

    We obtain an analytic expression for the height correlation function of a rough surface based on the inverse wave scattering method of Kirchhoff theory. The expression directly relates the height correlation function to diffuse scattered intensity. We test the solution by measuring the angular distribution of light scattered from rough silicon surfaces, solving for the height correlation functions, and comparing them to functions derived from AFM measurements. The results show good agreement. The advantages of this method are its accurate analytical equation for the height correlation function and the simplicity of the experimental setup required to measure it.

  11. Progress Report on the GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height) Research Project

    Science.gov (United States)

    Kitazawa, Y.; Ichikawa, K.; Akiyama, H.; Ebinuma, T.; Isoguchi, O.; Kimura, N.; Konda, M.; Kouguchi, N.; Tamura, H.; Tomita, H.; Yoshikawa, Y.; Waseda, T.

    2016-12-01

    Global Navigation Satellite Systems (GNSS), such as GPS is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location to high precision using radio signals transmitted from satellites, GNSS reflectometry (GNSS-R) involves making measurements from the reflections from the Earth of navigation signals from GNSS satellites. Reflected signals from sea surface are considered that those are useful to observe sea state and sea surface height. We have started a research program for GNSS-R applications on oceanographic observations under the contract with MEXT (Ministry of Education Culture, Sports, Science and Technology, JAPAN) and launched a Japanese research consortium, GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height). It is aiming to evaluate the capabilities of GNSS-R observations for oceanographic phenomena with different time scales, such as ocean waves (1/10 to tens of seconds), tides (one or half days), and sea surface dynamic height (a few days to years). In situ observations of ocean wave spectrum, wind speed vertical profile, and sea surface height will be quantitatively compared with equivalent estimates from simultaneous GNSS-R measurements. The GROWTH project will utilize different types of observation platforms; marine observation towers (about 20 m height), multi-copters (about 100 to 150 m height), and much higher-altitude CYGNSS data. Cross-platform data, together with in situ oceanographic observations, will be compared after adequate temporal averaging that accounts differences of the footprint sizes and temporal and spatial scales of oceanographic phenomena. This paper will provide overview of the GROWTH project, preliminary test results, obtained by the multi-sensor platform at observation towers, suggest actual footprint sizes and identification of swell. Preparation status of a ground station which will be supplied to receive CYGNSS data

  12. Verification of model wave heights with long-term moored buoy data: Application to wave field over the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Samiksha, S.V.; Polnikov, V.G.; Vethamony, P.; Rashmi, R.; Pogarskii, F.; Sudheesh, K.

    for the model comparison. Based on the error estimates of significant wave heights and spectral wave energy, improvement achieved in wave prediction using ModWAM is demonstrated. We find that the ModWAM improved the accuracy of significant wave height prediction...

  13. A Rational Procedure for Determination of Directional Individual Design Wave Heights

    DEFF Research Database (Denmark)

    Sterndorff, M.; Sørensen, John Dalsgaard

    2001-01-01

    crest elevation are available. In Sørensen & Sterndorff (2000) stochastic models for the annual maximum values of the omnidirectional and directional significant wave heights, individual wave heights, and individual crest heights were presented. The models include dependencies between the maximum wave......For code-based LRFD and for reliability-based assessment of offshore structures such as steel platforms it is essential that consistent directional and omnidirectional probability distributions for the maximum significant wave height, the maximum individual wave height, and the maximum individual...

  14. Conversion from surface wave to surface wave on reflection

    DEFF Research Database (Denmark)

    Novitsky, Andrey

    2010-01-01

    We discuss the reflection and transmission of an incident surface wave to a pure surface wave state at another interface. This is allowed only for special media parameters: at least one of the media must be magnetic. We found such material characteristics that the obliquely incident surface wave...... can be transmitted without changing its direction (nevertheless the amplitude varies). For other media parameters, only normally incident surface waves can be converted to surface waves. We propose applications of the predicted conversion as a beam splitter and polarization filter for surface waves....

  15. Estimation of design wave heights based on exterme value statistics for Kakinada coast, Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.; Raju, N.S.N.

    lower values, Gumbel distribution appears to estimate the extreme wave height reasonably well and gives a realistic value for the study region. The extreme wave estimated based only on the monsoon wave data deviated significantly from the estimate based...

  16. Numerical Simulation of Wave Height and Wave Set-Up in Nearshore Regions

    Institute of Scientific and Technical Information of China (English)

    郑永红; 沈永明; 邱大洪

    2001-01-01

    Based on the time dependent mild slope equation including the effect of wave energy dissipation, an expression for the energy dissipation factor is derived in conjunction with the wave energy balance equation, and then a practical method for the simulation of wave height and wave set-up in nearshore regions is presented. The variation of the complex wave amplitude is numerically simulated by use of the parabolic mild slope equation including the effect of wave energy dissipation due to wave breaking. The components of wave radiation stress are calculated subsequently by new expressions for them according to the obtained complex wave amplitude, and then the depth-averaged equation is applied to the calculation of wave set-up due to wave breaking. Numerical results are in good agreement with experimental data,showing that the expression for the energy dissipation factor is reasonable and that the new method is effective for the simulation of wave set-up due to wave breaking in nearshore regions.

  17. OW AVISO Sea-Surface Height & Niiler Climatology

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset contains satellite-derived sea-surface height measurements collected by means of the TOPEX/Poseidon/ERS, JASON-1/Envisat, and Jason-2/Envisat satellite...

  18. OW AVISO Sea-Surface Height & Levitus Climatology

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset contains satellite-derived sea-surface height measurements collected by means of the TOPEX/Poseidon/ERS, JASON-1/Envisat, and Jason-2/Envisat satellite...

  19. Surface Acoustic Wave Devices

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    of a Mach-Zehnder interferometer (MZI). This is an optical device consisting if one waveguide that is split into two waveguide arms which are assembled again later on. By applying the mechanical field from a SAW the light in the two arms can be modulated and interfere constructively and destructively......The work of this project is concerned with the simulation of surface acoustic waves (SAW) and topology optimization of SAW devices. SAWs are elastic vibrations that propagate along a material surface and are extensively used in electromechanical filters and resonators in telecommunication. A new...... application is modulation of optical waves in waveguides. This presentation elaborates on how a SAW is generated by interdigital transducers using a 2D model of a piezoelectric, inhomogeneous material implemented in the high-level programming language Comsol Multiphysics. The SAW is send through a model...

  20. Progress Report on the GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height) Research Project

    Science.gov (United States)

    Ichikawa, Kaoru; Akiyama, Hiroaki; Ebinuma, Takuji; Isoguchi, Osamu; Kimura, Noriaki; Kitazawa, Yukihito; Konda, Masanori; Kouguchi, Nobuyuki; Tamura, Hitoshi; Tomita, Hiroyuki; Yoshikawa, Yutaka; Waseda, Takuji

    2016-04-01

    There has been considerable interest in GNSS Reflectometry (GNSS-R) as a new remote-sensing method. We have started a research program for GNSS-R applications on oceanographic observations under the contract with MEXT (Ministry of Education Culture, Sports, Science and Technology, JAPAN) and launched a Japanese research consortium, GROWTH. It is aiming to evaluate the capabilities of GNSS-R observations for oceanographic phenomena with different time scales, such as ocean waves (1/10 to tens of seconds), tides (one or half days), and sea surface dynamic height (a few days to years). In situ observations of ocean wave spectrum, wind speed vertical profile, and sea surface height will be quantitatively compared with equivalent estimates from simultaneous GNSS-R measurements. The GROWTH project will utilize different types of observation platforms; marine observation towers (about 20 m height), multi-copters (about 100 to 200 m height), and much higher-altitude CYGNSS data. Cross-platform data, together with in situ oceanographic observations, will be compared after adequate temporal averaging that accounts differences of the footprint sizes and temporal and spatial scales of oceanographic phenomena. This paper will provide overview of the GROWTH project, preliminary test results obtained by the multi-sensor platform at observation towers, and preparation status of a ground station that will be supplied to receive CYGNSS data at Japan.

  1. A maximum entropy distribution for wave heights of non-linear sea waves

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on the maximum entropy principle, a probability density function (PDF) for the zero-crossing wave height (H)of random waves is derived as the simple form fn (H) = αHγe-βHn ( n is a selectable positive integer) through solving a variational problem subject to some quite general constraints. This PDF maximizes the information entropy of H, and its parameters α, γ and β are expressed ear sea waves with large uncertainty, and its parameters can be simply determined from available data. Comparisons between the PDF with n = 3 and n = 4 and the observed distributions of H from wave records measured in the East China Sea and in a wind-wave tunnel show fairly satisfying agreements.

  2. Surface-wave photonic quasicrystal

    CERN Document Server

    Gao, Zhen; Zhang, Youming; Xu, Hongyi; Zhang, Baile

    2016-01-01

    In developing strategies of manipulating surface electromagnetic waves, it has been recently recognized that a complete forbidden band gap can exist in a periodic surface-wave photonic crystal, which has subsequently produced various surface-wave photonic devices. However, it is not obvious whether such a concept can be extended to a non-periodic surface-wave system that lacks translational symmetry. Here we experimentally demonstrate that a surface-wave photonic quasicrystal that lacks periodicity can also exhibit a forbidden band gap for surface electromagnetic waves. The lower cutoff of this forbidden band gap is mainly determined by the maximum separation between nearest neighboring pillars. Point defects within this band gap show distinct properties compared to a periodic photonic crystal for the absence of translational symmetry. A line-defect waveguide, which is crafted out of this surface-wave photonic quasicrystal by shortening a random row of metallic rods, is also demonstrated to guide and bend sur...

  3. STUDY OF NON-BOUSSINESQ EFFCET ON SEA SURFACE HEIGHT

    Institute of Scientific and Technical Information of China (English)

    CHEN Xian-yao; WANG Xuan; WANG Xiu-hong; QIAO Fang-li

    2004-01-01

    A set of equations was derived for a non-Boussinesq ocean model in this paper.A new time-splitting scheme was introduced which incorporates the 4th-order Runge-Kutta explicit scheme of low-frequency mode and an implicit scheme of high-frequency mode.With this model,potential temperature,salinity fields and sea surface height were calculated simultaneously such that the numerical error of extrapolation of density field from the current time level to the next one could be reduced while using the equation of mass conservation to determine sea surface height.The non-Boussinesq effect on the density field and sea surface height was estimated by numerical experiments in the final part of this paper.

  4. A new model to estimate significant wave heights with ERS-1/2 scatterometer data

    Institute of Scientific and Technical Information of China (English)

    GUO Jie; HE Yijun; William Perrie; SHEN Hui; CHU Xiaoqing

    2009-01-01

    A new model is proposed to estimate the significant wave heights with ERS-1/2 scatterometer data. The results show that the relationship between wave parameters and radar backscattering cross section is similar to that between wind and the radar backscattering cross section. Therefore, the relationship between significant wave height and the radar backscattering cross section is established with a neural network algorithm, which is, if the average wave period is ≤7s, the root mean square of significant wave height retrieved from ERS-1/2 data is 0.51 m, or 0.72 m if it is >7s otherwise.

  5. Influence of Earthquake Parameters on Tsunami Wave Height and Inundation

    Science.gov (United States)

    Kulangara Madham Subrahmanian, D.; Sri Ganesh, J.; Venkata Ramana Murthy, M.; V, R. M.

    2014-12-01

    After Indian Ocean Tsunami (IOT) on 26th December, 2004, attempts are being made to assess the threat of tsunami originating from different sources for different parts of India. The Andaman - Sumatra trench is segmented by transcurrent faults and differences in the rate of subduction which is low in the north and increases southward. Therefore key board model with initial deformation calculated using different strike directions, slip rates, are used. This results in uncertainties in the earthquake parameters. This study is made to identify the location of origin of most destructive tsunami for Southeast coast of India and to infer the influence of the earthquake parameters in tsunami wave height travel time in deep ocean as well as in the shelf and inundation in the coast. Five tsunamigenic sources were considered in the Andaman - Sumatra trench taking into consideration the tectonic characters of the trench described by various authors and the modeling was carried out using TUNAMI N2 code. The model results were validated using the travel time and runup in the coastal areas and comparing the water elevation along Jason - 1's satellite track. The inundation results are compared from the field data. The assessment of the tsunami threat for the area south of Chennai city the metropolitan city of South India shows that a tsunami originating in Car Nicobar segment of the Andaman - Sumatra subduction zone can generate the most destructive tsunami. Sensitivity analysis in the modelling indicates that fault length influences the results significantly and the tsunami reaches early and with higher amplitude. Strike angle is also modifying the tsunami followed by amount of slip.

  6. On microseisms recorded near the Ligurian coast (Italy) and their relationship with sea wave height

    DEFF Research Database (Denmark)

    Ferretti, G.; Zunino, Andrea; Scafidi, D.;

    2013-01-01

    In this study, microseism recordings from a near coast seismic station and concurrent significant sea wave heights (H13 ) are analysed to calibrate an empirical relation for predicting sea wave height in the Ligurian Sea. The study stems from the investigation of the damaging sea storms occurred ...

  7. An Internal Wave as a Frequency Filter for Surface Gravity Waves on Water

    CERN Document Server

    Lossow, K

    2010-01-01

    We consider one-dimensional model of the interaction between surface and the internal gravity water waves. The internal wave is modeled by its basic form: a non-dispersive field with a horizontal current that is uniform over all depth, insignificantly affected by the surface waves, while ignoring surface tension and wind growth/decay effects. The depth is infinite. Approximation for the height of the surface wave on the flow by the "elementary quasi stationary" solutions was found. It was shown that the flow acts as a frequency filter for gravitational waves on water.

  8. Triggered lightning sky waves, return stroke modeling, and ionosphere effective height

    Science.gov (United States)

    Carvalho, F. L.; Uman, M. A.; Jordan, D. M.; Hill, J. D.; Cummer, S. A.; Kotovsky, D. A.; Moore, R. C.

    2017-03-01

    Ground waves and sky waves measured 209 km and 250 km south of six triggered lightning flashes containing 30 strokes that occurred in the half-hour before sunset on 27 August 2015 are presented and analyzed. We use a cross-correlation technique to find the ionospheric effective reflection height and compare our results to previous techniques that calculate effective height based on the time delay between ground wave and sky wave time domain features. From the first flash to the last flash there is, on average, a 1.6 km increase in effective ionospheric height, whereas no change in effective ionospheric height can be discerned along the individual strokes of a given flash. We show to what extent the triggered lightning radiation source can be described (using channel-base current, channel geometry, and channel luminosity versus time and height) and speculate that a well-characterized source could allow a more accurate determination of the electromagnetic fields radiated toward the ionosphere than has been done to date. We show that both channel geometry and the change in return stroke current amplitude and waveshape with channel height (inferred from measured channel luminosity versus height and time) determine the waveshape of the ground wave (and presumably the upward propagating wave that results in the sky wave) and that the waveshape of the ground wave does not appear to be related to the current versus time waveform measured at the channel base other than a roughly linear relationship between the two peak values.

  9. Tamm-Langmuir surface waves

    Science.gov (United States)

    Golenitskii, K. Â. Yu.; Koshelev, K. Â. L.; Bogdanov, A. Â. A.

    2016-10-01

    In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states—we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.

  10. Tamm-Langmuir surface waves

    CERN Document Server

    Golenitskii, K U; Bogdanov, A A

    2016-01-01

    In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states - we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.

  11. Sea Surface Height, Absolute, Aviso, 0.25 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Aviso Absolute Sea Surface Height is the Sea Surface Height Deviation plus the long term mean dynamic height. This is Science Quality data.

  12. Surface Waves on Metamaterials Interfaces

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee

    2016-01-01

    We analyze surface electromagnetic waves supported at the interface between isotropic medium and effective anisotropic material that can be realized by alternating conductive and dielectrics layers. This configuration can host various types of surface waves and therefore can serve as a rich platf...

  13. Surface Waves on Metamaterials Interfaces

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee;

    2016-01-01

    We analyze surface electromagnetic waves supported at the interface between isotropic medium and effective anisotropic material that can be realized by alternating conductive and dielectrics layers. This configuration can host various types of surface waves and therefore can serve as a rich platf...

  14. Surface acoustic wave microfluidics.

    Science.gov (United States)

    Ding, Xiaoyun; Li, Peng; Lin, Sz-Chin Steven; Stratton, Zackary S; Nama, Nitesh; Guo, Feng; Slotcavage, Daniel; Mao, Xiaole; Shi, Jinjie; Costanzo, Francesco; Huang, Tony Jun

    2013-09-21

    The recent introduction of surface acoustic wave (SAW) technology onto lab-on-a-chip platforms has opened a new frontier in microfluidics. The advantages provided by such SAW microfluidics are numerous: simple fabrication, high biocompatibility, fast fluid actuation, versatility, compact and inexpensive devices and accessories, contact-free particle manipulation, and compatibility with other microfluidic components. We believe that these advantages enable SAW microfluidics to play a significant role in a variety of applications in biology, chemistry, engineering and medicine. In this review article, we discuss the theory underpinning SAWs and their interactions with particles and the contacting fluids in which they are suspended. We then review the SAW-enabled microfluidic devices demonstrated to date, starting with devices that accomplish fluid mixing and transport through the use of travelling SAW; we follow that by reviewing the more recent innovations achieved with standing SAW that enable such actions as particle/cell focusing, sorting and patterning. Finally, we look forward and appraise where the discipline of SAW microfluidics could go next.

  15. Risk Analysis of Breakwater Caisson Under Wave Attack Using Load Surface Approximation

    Institute of Scientific and Technical Information of China (English)

    Dong Hyawn KIM

    2014-01-01

    A new load surface based approach to the reliability analysis of caisson-type breakwater is proposed. Uncertainties of the horizontal and vertical wave loads acting on breakwater are considered by using the so-called load surfaces, which can be estimated as functions of wave height, water level, and so on. Then, the first-order reliability method (FORM) can be applied to determine the probability of failure under the wave action. In this way, the reliability analysis of breakwaters with uncertainties both in wave height and in water level is possible. Moreover, the uncertainty in wave breaking can be taken into account by considering a random variable for wave height ratio which relates the significant wave height to the maximum wave height. The proposed approach is applied numerically to the reliability analysis of caisson breakwater under wave attack that may undergo partial or full wave breaking.

  16. Global validation of the wave model WAM over a one-year period using geosat wave height data

    Energy Technology Data Exchange (ETDEWEB)

    Romeiser, R. (Universitaet Hamburg (Germany))

    1993-03-15

    The high quality of wave fields simulated by the third-generation wave model WAM has already been demonstrated in various validation studies using in situ measurements as well as data from satellites as reference. However, owing to limitations of the reference data sets, the previous studies concentrated on relatively small regions or short time periods only, for which adequate measurements were available. In this paper the first global verification of the WAM model over a full 1-year period is presented. The significant wave heights hindcast for 1988 by the WAM model as implemented at the European Centre for Medium Range Weather Forecasts are compared with measurements obtained by the Geosat radar altimeter. The wave heights from WAM and Geosat show good agreement in general. However, significant regional and seasonal differences are found. The hindcast wave heights are underestimated by about 20% in large parts of the southern hemisphere and the tropical region during May-September. For the rest of the time, the agreement with Geosat data is fairly good. Together with the fact that also the rms variability of wave heights in the tropical region is clearly underestimated by WAM, this can possibly be attributed to simplifications like the neglect of atmospheric stratification effects when converting wind speeds to the wind stress fields driving WAM. Furthermore, the intercomparison indicates that low wave heights below [approx]1.5 m are generally overestimated by WAM. As it is planned to use altimeter wave heights for updating wave models in future data assimilation systems, it is quite important to have efficient quality control criteria for these data. The difference between the Geosat and WAM wave heights shows a clear dependence on the additional parameters in some cases, which must be related to quality problems of the Geosat data. Some new criteria for the rejection of incorrect Geosat data points are obtained. 16 refs., 6 figs.

  17. Scattering of mid-IR-range surface electromagnetic waves by optically smooth metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bonch-Bruevich, A.M.; Libenson, M.N.; Makin, V.S.; Pudkov, S.D.; Trubaev, V.V.

    1985-09-01

    The paper reports the experimental observation of the intense scattering of surface electromagnetic waves with a wavelength of 10.6 microns excited on an optically smooth metal surface with a residual roughness having a mean square height of less than 25 A. A method for determining the attenuation of surface electromagnetic waves is proposed, and a test of the method is reported which involves the measurement of the relative intensity of the local scattering of the waves along their path. 9 references.

  18. Future Wave Height Situation estimated by the Latest Climate Scenario around Funafuti Atoll, Tuvalu

    Science.gov (United States)

    Sato, D.; Yokoki, H.; Kuwahara, Y.; Yamano, H.; Kayanne, H.; Okajima, H.; Kawamiya, M.

    2012-12-01

    Sea-level rise due to the global warming is significant phenomenon to coastal region in the world. Especially the atoll islands, which are low-lying and narrow, have high vulnerability against the sea-level rise. Recently the improved future climate projection (MIROC-ESM) was provided by JAMSTEC, which adopted the latest climate scenarios based on the RCP (Representative Concentration Pathway) of the green house gasses. Wave field simulation including the latest sea-level rise pathway by MIROC-ESM was conducted to understand the change of significant wave heights in Funafuti Atoll, Tuvalu, which was an important factor to manage the coast protection. MIROC-ESM provides monthly sea surface height in the fine gridded world (1.5 degree near the equator). Wave field simulation was conducted using the climate scenario of RCP45 in which the radioactive forcing of the end of 21st century was stabilized to 4.5 W/m2. Sea-level rise ratio of every 10 years was calculated based on the historical data set from 1850 to 2005 and the estimated data set from 2006 to 2100. In that case, the sea-level increases by 10cm after 100 years. In this study, the numerical simulation of wave field at the rate of sea-level rise was carried out using the SWAN model. The wave and wind conditions around Funafuti atoll is characterized by two seasons that are the trade (Apr. - Nov.) and non-trade (Jan. - Mar., Dec.) wind season. Then, we set up the two seasonal boundary conditions for one year's simulation, which were calculated from ECMWF reanalysis data. Simulated results of significant wave heights are analyzed by the increase rate (%) calculated from the base results (Average for 2000 - 2005) and the results of 2100. Calculated increase rate of the significant wave height for both seasons was extremely high on the reef-flat. Maximum increase rates of the trade and non-trade wind season were 1817% and 686%, respectively. The southern part of the atoll has high increasing rate through the two

  19. Multichannel analysis of surface waves

    Science.gov (United States)

    Park, C.B.; Miller, R.D.; Xia, J.

    1999-01-01

    The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and characterizing the shallow subsurface. Most surface-wave analysis relies on the accurate calculation of phase velocities for the horizontally traveling fundamental-mode Rayleigh wave acquired by stepping out a pair of receivers at intervals based on calculated ground roll wavelengths. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the whole wave field. Among these nonplanar, nonfundamental-mode Rayleigh waves (noise) are body waves, scattered and nonsource-generated surface waves, and higher-mode surface waves. The degree to which each of these types of noise contaminates the dispersion curve and, ultimately, the inverted shear-wave velocity profile is dependent on frequency as well as distance from the source. Multichannel recording permits effective identification and isolation of noise according to distinctive trace-to-trace coherency in arrival time and amplitude. An added advantage is the speed and redundancy of the measurement process. Decomposition of a multichannel record into a time variable-frequency format, similar to an uncorrelated Vibroseis record, permits analysis and display of each frequency component in a unique and continuous format. Coherent noise contamination can then be examined and its effects appraised in both frequency and offset space. Separation of frequency components permits real-time maximization of the S/N ratio during acquisition and subsequent processing steps. Linear separation of each ground roll frequency component allows calculation of phase velocities by simply measuring the linear slope of each frequency component. Breaks in coherent surface-wave arrivals, observable on the decomposed record, can be compensated for during acquisition and processing. Multichannel recording permits single-measurement surveying of a broad depth range, high levels of

  20. Anomalous wave as a result of the collision of two wave groups on sea surface

    CERN Document Server

    Ruban, V P

    2016-01-01

    The numerical simulation of the nonlinear dynamics of the sea surface has shown that the collision of two groups of relatively low waves with close but noncollinear wave vectors (two or three waves in each group with a steepness of about 0.2) can result in the appearance of an individual anomalous wave whose height is noticeably larger than that in the linear theory. Since such collisions quite often occur on the ocean surface, this scenario of the formation of rogue waves is apparently most typical under natural conditions.

  1. Application of Maximum Entropy Principle to Studying the Distribution of Wave Heights in A Random Wave Field

    Institute of Scientific and Technical Information of China (English)

    周良明; 郭佩芳; 王强; 杜伊

    2004-01-01

    Based on the maximum entropy principle, a probability density function (PDF) is derived for the distribution of wave heights in a random wave field, without any more hypothesis. The present PDF, being a non-Rayleigh form, involves two parameters: the average wave height H and the state parameter γ. The role of γ in the distribution of wave heights is examined. It is found that γ may be a certain measure of sea state. A least square method for determining γ from measured data is proposed. In virtue of the method, the values of γ are determined for three sea states from the data measured in the East China Sea. The present PDF is compared with the well known Rayleigh PDF of wave height and it is shown that it much better fits the data than the Rayleigh PDF. It is expected that the present PDF would fit some other wave variables, since its derivation is not restricted only to the wave height.

  2. Projected changes in significant wave height toward the end of the 21st century: Northeast Atlantic

    Science.gov (United States)

    Aarnes, Ole Johan; Reistad, Magnar; Breivik, Øyvind; Bitner-Gregersen, Elzbieta; Ingolf Eide, Lars; Gramstad, Odin; Magnusson, Anne Karin; Natvig, Bent; Vanem, Erik

    2017-04-01

    Wind field ensembles from six CMIP5 models force wave model time slices of the northeast Atlantic over the last three decades of the 20th and the 21st centuries. The future wave climate is investigated by considering the RCP4.5 and RCP8.5 emission scenarios. The CMIP5 model selection is based on their ability to reconstruct the present (1971-2000) extratropical cyclone activity, but increased spatial resolution has also been emphasized. In total, the study comprises 35 wave model integrations, each about 30 years long, in total more than 1000 years. Here annual statistics of significant wave height are analyzed, including mean parameters and upper percentiles. There is general agreement among all models considered that the mean significant wave height is expected to decrease by the end of the 21st century. This signal is statistically significant also for higher percentiles, but less evident for annual maxima. The RCP8.5 scenario yields the strongest reduction in wave height. The exception to this is the north western part of the Norwegian Sea and the Barents Sea, where receding ice cover gives longer fetch and higher waves. The upper percentiles are reduced less than the mean wave height, suggesting that the future wave climate has higher variance than the historical period.

  3. On the joint distribution of wave heights and periods: The role of the spectral bandwidth

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, R.G.; Rubio, R.F.; Pacheco, M.M.; Martinez, M.A. [Univ. de Las Palmas de Gran Canaria (Spain). Dept. de Fisica

    1996-12-31

    The influence of spectral bandwidth on the probabilistic structure of the joint distribution of wave heights and periods is analyzed by means of simulated wave records. The authors put the emphasis on its effect upon the asymmetric and bimodal structure of the distributions. Moreover, the adequacy of some theoretical models to describe such features is considered.

  4. Seasonal distribution of wave heights off Yanam on the east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nayak, B.U.; Chandramohan, D.; Sakhardande, R.N.

    Waves were measured off Yanam on the East Coast of India for a period of one year from June 1983 to May 1984. The data were analysed using the Tucker's zero up-crossing and the spectral methods. Seasonwise distribution of significant wave height...

  5. Final Report for Project: Impacts of stratification and non-equilibrium winds and waves on hub-height winds

    Energy Technology Data Exchange (ETDEWEB)

    Patton, Edward G. [Univ. Corporation for Atmospheric Research, Boulder, CO (United States)

    2015-07-14

    This project used a combination of turbulence-resolving large-eddy simulations, single-column modeling (where turbulence is parameterized), and currently available observations to improve, assess, and develop a parameterization of the impact of non-equilibrium wave states and stratification on the buoy-observed winds to establish reliable wind data at the turbine hub-height level. Analysis of turbulence-resolving simulations and observations illuminates the non-linear coupling between the atmosphere and the undulating sea surface. This analysis guides modification of existing boundary layer parameterizations to include wave influences for upward extrapolation of surface-based observations through the turbine layer. Our surface roughness modifications account for the interaction between stratification and the effects of swell’s amplitude and wavelength as well as swell’s relative motion with respect to the mean wind direction. The single-column version of the open source Weather and Research Forecasting (WRF) model (Skamarock et al., 2008) serves as our platform to test our proposed planetary boundary layer parameterization modifications that account for wave effects on marine atmospheric boundary layer flows. WRF has been widely adopted for wind resource analysis and forecasting. The single column version is particularly suitable to development, analysis, and testing of new boundary layer parameterizations. We utilize WRF’s single-column version to verify and validate our proposed modifications to the Mellor-Yamada-Nakanishi-Niino (MYNN) boundary layer parameterization (Nakanishi and Niino, 2004). We explore the implications of our modifications for two-way coupling between WRF and wave models (e.g.,Wavewatch III). The newly implemented parameterization accounting for marine atmospheric boundary layer-wave coupling is then tested in three-dimensional WRF simulations at grid sizes near 1 km. These simulations identify the behavior of simulated winds at the

  6. [P wave dispersion increased in childhood depending on blood pressure, weight, height, and cardiac structure and function].

    Science.gov (United States)

    Chávez-González, Elibet; González-Rodríguez, Emilio; Llanes-Camacho, María Del Carmen; Garí-Llanes, Merlin; García-Nóbrega, Yosvany; García-Sáez, Julieta

    2014-01-01

    Increased P wave dispersion are identified as a predictor of atrial fibrillation. There are associations between hypertension, P wave dispersion, constitutional and echocardiographic variables. These relationships have been scarcely studied in pediatrics. The aim of this study was to determine the relationship between P wave dispersion, blood pressure, echocardiographic and constitutional variables, and determine the most influential variables on P wave dispersion increases in pediatrics. In the frame of the PROCDEC II project, children from 8 to 11 years old, without known heart conditions were studied. Arterial blood pressure was measured in all the children; a 12-lead surface electrocardiogram and an echocardiogram were done as well. Left ventricular mass index mean values for normotensive (25.91±5.96g/m(2.7)) and hypertensive (30.34±8.48g/m(2.7)) showed significant differences P=.000. When we add prehypertensive and hypertensive there are 50.38% with normal left ventricular mass index and P wave dispersion was increased versus 13.36% of normotensive. Multiple regression demonstrated that the mean blood pressure, duration of A wave of mitral inflow, weight and height have a value of r=0.88 as related to P wave dispersion. P wave dispersion is increased in pre- and hypertensive children compared to normotensive. There are pre- and hypertensive patients with normal left ventricular mass index and increased P wave dispersion. Mean arterial pressure, duration of the A wave of mitral inflow, weight and height are the variables with the highest influence on increased P wave dispersion. Copyright © 2013 Instituto Nacional de Cardiología Ignacio Chávez. Published by Masson Doyma México S.A. All rights reserved.

  7. Final Report for Project: Impacts of stratification and non-equilibrium winds and waves on hub-height winds

    Energy Technology Data Exchange (ETDEWEB)

    Patton, Edward G. [Univ. Corporation for Atmospheric Research, Boulder, CO (United States)

    2015-07-14

    This project used a combination of turbulence-resolving large-eddy simulations, single-column modeling (where turbulence is parameterized), and currently available observations to improve, assess, and develop a parameterization of the impact of non-equilibrium wave states and stratification on the buoy-observed winds to establish reliable wind data at the turbine hub-height level. Analysis of turbulence-resolving simulations and observations illuminates the non-linear coupling between the atmosphere and the undulating sea surface. This analysis guides modification of existing boundary layer parameterizations to include wave influences for upward extrapolation of surface-based observations through the turbine layer. Our surface roughness modifications account for the interaction between stratification and the effects of swell’s amplitude and wavelength as well as swell’s relative motion with respect to the mean wind direction. The single-column version of the open source Weather and Research Forecasting (WRF) model (Skamarock et al., 2008) serves as our platform to test our proposed planetary boundary layer parameterization modifications that account for wave effects on marine atmospheric boundary layer flows. WRF has been widely adopted for wind resource analysis and forecasting. The single column version is particularly suitable to development, analysis, and testing of new boundary layer parameterizations. We utilize WRF’s single-column version to verify and validate our proposed modifications to the Mellor-Yamada-Nakanishi-Niino (MYNN) boundary layer parameterization (Nakanishi and Niino, 2004). We explore the implications of our modifications for two-way coupling between WRF and wave models (e.g.,Wavewatch III). The newly implemented parameterization accounting for marine atmospheric boundary layer-wave coupling is then tested in three-dimensional WRF simulations at grid sizes near 1 km. These simulations identify the behavior of simulated winds at the

  8. The dependence of wind stress on wave height and wind speed

    Science.gov (United States)

    Blake, Reginald A.

    1991-01-01

    Three near-neutral boundary layer data sets were investigated with the aim of finding a dependence of wind stress on both wind speed and significant wave height. The data set most representative of open-ocean wave height, wind speed, and momentum flux conditions, was selected and analyzed by means of the least-squares method to produce a new parameterization for the wind stress as a function of both wind speed and significant wave height. This study shows that the wind stress, and consequently the drag coefficient, decreases with increasing wave height for a fixed wind speed. The study also shows that the curvature of the wind profile decreases with increasing wave height and that the C(DN) = A + BU-bar(10) form for the drag coefficient parameterization is inadequate. A drag coefficient that applies to both smooth and rough flows is proposed. These results are more applicable for open-ocean deep-water conditions and less applicable for sheltered, closed, shallow water sites.

  9. Impacts of tropical cyclone inflow angle on ocean surface waves

    Institute of Scientific and Technical Information of China (English)

    ZHAO Wei; HONG Xin

    2011-01-01

    The inflow angle of tropical cyclones (TC) is generally neglected in numerical studies of ocean surface waves induced by TC. In this study, the impacts of TC inflow angle on ocean surface waves were investigated using a high-resolution wave model. Six numerical experiments were conducted to examine, in detail, the effects of inflow angle on mean wave parameters and the spectrum of wave directions. A comparison of the waves simulated in these experiments shows that inflow angle significantly modifies TC-induced ocean surface waves. As the inflow angle increases, the asymmetric axis of the significant wave height (SWH) field shifts 30° clockwise, and the maximum SWH moves from the front-right to the rear-right quadrant. Inflow angle also affects other mean wave parameters, especially in the rear-left quadrant, such as the mean wave direction, the mean wavelength, and the peak direction. Inflow angle is a key factor in wave models for the reproduction of double-peak or multi-peak patterns in the spectrum of wave directions. Sensitivity experiments also show that the simulation with a 40° inflow angle is the closest to that of the NOAA statistical SLOSH inflow angle. This suggests that 40° can be used as the inflow angle in future TC-induced ocean surface wave simulations when SLOSH or observed inflow angles are not available.

  10. Change of Martian surface height associated with polar cold spots

    Science.gov (United States)

    Ford, P. G.; Pettengill, G. H.

    2003-12-01

    For the past 30 years, orbiting microwave radiometers have observed anomalously low emission temperatures during Martian polar winters. While the physical surface temperature cannot drop significantly below 148K---the point at which CO2 starts to condense---radiometric temperatures of 110K or lower at 25μ wavelength are commonly found in isolated ``cold spots'' throughout both northern and southern polar winters. These form roughly circular patches, tens to hundreds of km in diameter, and persist for no more than a few days. Three models have been proposed to account for them: (a) an atmospheric effect that accompanies CO2 snowfall; (b) fresh surface deposits of CO2 snow; or (c) a change in the properties of CO2 slab ice. Following the success of Smith et al.1 in using the MOLA laser altimeter aboard Mars Global Surveyor to directly measure the growth of the winter polar caps, we have applied the same technique to ask whether cold spots are accompanied by a sudden change in surface height. To identify the cold spots, we first examined all polar observations made by the TES radiometer that was co-boresited with MOLA, and made gridded images of ∂ T / ∂ λ , the derivative of the brightness temperature wrt wavelength, 20μ 50cm) CO2 snow deposits, but it cannot help us decide between the alternatives of CO2 snowfall or a change in slab ice properties. 1 Smith, Zuber, and Neumann, Science, {294}, 2141-2146, 2001.

  11. Application of neural networks and support vector machine for significant wave height prediction

    Directory of Open Access Journals (Sweden)

    Jadran Berbić

    2017-07-01

    Full Text Available For the purposes of planning and operation of maritime activities, information about wave height dynamics is of great importance. In the paper, real-time prediction of significant wave heights for the following 0.5–5.5 h is provided, using information from 3 or more time points. In the first stage, predictions are made by varying the quantity of significant wave heights from previous time points and various ways of using data are discussed. Afterwards, in the best model, according to the criteria of practicality and accuracy, the influence of wind is taken into account. Predictions are made using two machine learning methods – artificial neural networks (ANN and support vector machine (SVM. The models were built using the built-in functions of software Weka, developed by Waikato University, New Zealand.

  12. Height measurement of astigmatic test surfaces by a keratoscope that uses plane geometry surface reconstruction.

    Science.gov (United States)

    Tripoli, N K; Cohen, K L; Obla, P; Coggins, J M; Holmgren, D E

    1996-06-01

    To assess the accuracy with which the Keratron keratoscope (Optikon 2000, Rome, Italy) measured astigmatic test surfaces by a profile reconstruction algorithm within a plane geometry model and to discriminate between error caused by the model and error caused by other factors. Height was reported by the Keratron for eight surfaces with central astigmatism ranging from 4 to 16 diopters. A three-dimensional ray tracing simulation produced theoretic reflected ring patterns on which the Keratron's reconstruction algorithm was performed. The Keratron's measurements were compared with the surfaces' formulas and the ray-traced simulations. With a new mathematical filter for smoothing ring data, now part of the Keratron's software, maximum error was 0.47% of the total height and was usually less than 1% of local power for surfaces with 4 diopters of astigmatism. For surfaces with 16 diopters of astigmatism, maximum error was as high as 2.9% of total height and was usually less than 2.5% of local power. The reconstruction algorithm accounted for 40% and 70% of height error, respectively. The efficacy of keratoscopes cannot be assumed from their design theories but must be tested. Although plane geometry surface reconstruction contributed greatly to total height error, total error was so small that it is unlikely to affect clinical use.

  13. Modeling nonstationary extreme wave heights in present and future climate of Greek Seas

    Directory of Open Access Journals (Sweden)

    Panagiota Galiatsatou

    2016-01-01

    Full Text Available In this study the generalized extreme value (GEV distribution function was used to assess nonstationarity in annual maximum wave heights for selected locations in the Greek Seas, both in the present and future climate. The available significant wave height data were divided into groups corresponding to the present period (1951 to 2000, a first future period (2001 to 2050, and a second future period (2051 to 2100. For each time period, the parameters of the GEV distribution were specified as functions of time-varying covariates and estimated using the conditional density network (CDN. For each location and selected time period, a total number of 29 linear and nonlinear models were fitted to the wave data, for a given combination of covariates. The covariates used in the GEV-CDN models consisted of wind fields resulting from the Regional Climate Model version 3 (RegCM3 developed by the International Center for Theoritical Physics (ICTP with a spatial resolution of 10 km × 10 km, after being processed using principal component analysis (PCA. The results obtained from the best fitted models in the present and future periods for each location were compared, revealing different patterns of relationships between wind components and extreme wave height quantiles in different parts of the Greek Seas and different periods. The analysis demonstrates an increase of extreme wave heights in the first future period as compared with the present period, causing a significant threat to Greek coastal areas in the North Aegean Sea and the Ionian Sea.

  14. An extreme value model for maximum wave heights based on weather types

    Science.gov (United States)

    Rueda, Ana; Camus, Paula; Méndez, Fernando J.; Tomás, Antonio; Luceño, Alberto

    2016-02-01

    Extreme wave heights are climate-related events. Therefore, special attention should be given to the large-scale weather patterns responsible for wave generation in order to properly understand wave climate variability. We propose a classification of weather patterns to statistically downscale daily significant wave height maxima to a local area of interest. The time-dependent statistical model obtained here is based on the convolution of the stationary extreme value model associated to each weather type. The interdaily dependence is treated by a climate-related extremal index. The model's ability to reproduce different time scales (daily, seasonal, and interannual) is presented by means of its application to three locations in the North Atlantic: Mayo (Ireland), La Palma Island, and Coruña (Spain).

  15. Surface wave chemical detector using optical radiation

    Science.gov (United States)

    Thundat, Thomas G.; Warmack, Robert J.

    2007-07-17

    A surface wave chemical detector comprising at least one surface wave substrate, each of said substrates having a surface wave and at least one measurable surface wave parameter; means for exposing said surface wave substrate to an unknown sample of at least one chemical to be analyzed, said substrate adsorbing said at least one chemical to be sensed if present in said sample; a source of radiation for radiating said surface wave substrate with different wavelengths of said radiation, said surface wave parameter being changed by said adsorbing; and means for recording signals representative of said surface wave parameter of each of said surface wave substrates responsive to said radiation of said different wavelengths, measurable changes of said parameter due to adsorbing said chemical defining a unique signature of a detected chemical.

  16. Dynamic Mechanism of Interannual Sea Surface Height Variability in the North Pacific Subtropical Gyre

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong-Chui; ZHANG Li-Feng; L(U) Qing-Ping

    2011-01-01

    In this study, the dynamic mechanisms of interannual sea surface height (SSH) variability are investigated based on the first-mode baroclinic Rossby wave model, with a focus on the effects of different levels of wind stress curl (WSC)、 Maximum covariance analysis (MCA) of WSC and SSH anomalies displays a mode with significant WSC anomalies located primarily in the mid-latitude eastern North Pacific and central tropical Pacific with corresponding SSH anomalies located to the west. This leading mode can be attributed to Ekman pumping induced by local wind stress and the westward-propagating Rossby wave driven by largescale wind stress. It is further found that in the middle latitudes, the SSH anomalies are largely determined by WSC variations associated with the North Pacific Gyre Oscillation (NPGO)、 rather than the Pacific Decadal Oscillation (PDO). The sensitivity of the predictive skill of the linear first-mode baroclinic model to different wind products is also examined.

  17. Modeling extreme wave heights from laboratory experiments with the nonlinear Schrödinger equation

    Science.gov (United States)

    Zhang, H. D.; Guedes Soares, C.; Cherneva, Z.; Onorato, M.

    2014-04-01

    Spatial variation of nonlinear wave groups with different initial envelope shapes is theoretically studied first, confirming that the simplest nonlinear theoretical model is capable of describing the evolution of propagating wave packets in deep water. Moreover, three groups of laboratory experiments run in the wave basin of CEHIPAR (Canal de Experiencias Hidrodinámicas de El Pardo, known also as El Pardo Model Basin) was founded in 1928 by the Spanish Navy. are systematically compared with the numerical simulations of the nonlinear Schrödinger equation. Although a little overestimation is detected, especially in the set of experiments characterized by higher initial wave steepness, the numerical simulation still displays a high degree of agreement with the laboratory experiments. Therefore, the nonlinear Schrödinger equation catches the essential characteristics of the extreme waves and provides an important physical insight into their generation. The modulation instability, resulting from the quasi-resonant four-wave interaction in a unidirectional sea state, can be indicated by the coefficient of kurtosis, which shows an appreciable correlation with the extreme wave height and hence is used in the modified Edgeworth-Rayleigh distribution. Finally, some statistical properties on the maximum wave heights in different sea states have been related with the initial Benjamin-Feir index.

  18. Spatial and temporal variations of wave height in shelf seas around India

    Digital Repository Service at National Institute of Oceanography (India)

    SanilKumar, V.; Anoop, T.R.

    trend (maximum ~-0.18 cm/year) in wave height is observed in the western Bay of Bengal except along the southern region. At most of the locations weak decreasing trend (0.1–2.5 cm/s/year) is observed for the annual mean wind speed. The conflicting trends...

  19. Broadband transverse electric surface wave in silicene

    Science.gov (United States)

    Ukhtary, M. Shoufie; Nugraha, Ahmad R. T.; Hasdeo, Eddwi H.; Saito, Riichiro

    2016-08-01

    Transverse electric (TE) surface wave in silicine is theoretically investigated. The TE surface wave in silicene is found to exhibit better characteristics compared with that in graphene, in terms of a broader frequency range and more confinement to the surface which originate from the buckled structure of silicene. We found that even undoped silicene can support the TE surface wave. We expect the similar characteristics of the TE surface wave in other two-dimensional materials that have a slightly buckled honeycomb lattice.

  20. Excitation of surface plasma waves over corrugated slow-wave structure

    Indian Academy of Sciences (India)

    Ashim P Jain; Jetendra Parashar

    2005-08-01

    A microwave propagating along vacuum–dielectric–plasma interface excites surface plasma wave (SPW). A periodic slow-wave structure placed over dielectric slows down the SPW. The phase velocity of slow SPW is sensitive to height, periodicity, number of periods, thickness and the separation between dielectric and slow-wave structure. These slow SPW can couple the microwave energy to the plasma and can sustain the discharge. The efficiency of the power coupling is few per cent and is sensitive to separation between dielectric and slow-wave structure.

  1. Wave Equation Inversion of Skeletonized SurfaceWaves

    KAUST Repository

    Zhang, Zhendong

    2015-08-19

    We present a surface-wave inversion method that inverts for the S-wave velocity from the Rayleigh dispersion curve for the fundamental-mode. We call this wave equation inversion of skeletonized surface waves because the dispersion curve for the fundamental-mode Rayleigh wave is inverted using finite-difference solutions to the wave equation. The best match between the predicted and observed dispersion curves provides the optimal S-wave velocity model. Results with synthetic and field data illustrate the benefits and limitations of this method.

  2. Calculating wave-generated bottom orbital velocities from surface-wave parameters

    Science.gov (United States)

    Wiberg, P.L.; Sherwood, C.R.

    2008-01-01

    Near-bed wave orbital velocities and shear stresses are important parameters in many sediment-transport and hydrodynamic models of the coastal ocean, estuaries, and lakes. Simple methods for estimating bottom orbital velocities from surface-wave statistics such as significant wave height and peak period often are inaccurate except in very shallow water. This paper briefly reviews approaches for estimating wave-generated bottom orbital velocities from near-bed velocity data, surface-wave spectra, and surface-wave parameters; MATLAB code for each approach is provided. Aspects of this problem have been discussed elsewhere. We add to this work by providing a method for using a general form of the parametric surface-wave spectrum to estimate bottom orbital velocity from significant wave height and peak period, investigating effects of spectral shape on bottom orbital velocity, comparing methods for calculating bottom orbital velocity against values determined from near-bed velocity measurements at two sites on the US east and west coasts, and considering the optimal representation of bottom orbital velocity for calculations of near-bed processes. Bottom orbital velocities calculated using near-bed velocity data, measured wave spectra, and parametric spectra for a site on the northern California shelf and one in the mid-Atlantic Bight compare quite well and are relatively insensitive to spectral shape except when bimodal waves are present with maximum energy at the higher-frequency peak. These conditions, which are most likely to occur at times when bottom orbital velocities are small, can be identified with our method as cases where the measured wave statistics are inconsistent with Donelan's modified form of the Joint North Sea Wave Project (JONSWAP) spectrum. We define the 'effective' forcing for wave-driven, near-bed processes as the product of the magnitude of forcing times its probability of occurrence, and conclude that different bottom orbital velocity statistics

  3. Variations mechanism in entropy of wave height field and its relation with thermodynamic entropy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper gives a brief description of annual period and seasonal variation in the wave height field entropy in the northeastern Pacific. A calculation of the quantity of the, received by lithosphere systems in the northern hemisphere is introduced. The wave heat field entropy is compared with the difference in the quantity of the sun's radiation heat. Analysis on the transfer method, period and lag of this seasonal variation led to the conclusion that the annual period and seasonal variation in the entropy of the wave height field in the Northwestern Pacific is due to the seasonal variation of the sun's radiation heat. Furthermore, the inconsistency between thermodynamic entropy and information entropy was studied.

  4. On the generation of internal wave modes by surface waves

    Science.gov (United States)

    Harlander, Uwe; Kirschner, Ian; Maas, Christian; Zaussinger, Florian

    2016-04-01

    Internal gravity waves play an important role in the ocean since they transport energy and momentum and the can lead to mixing when they break. Surface waves and internal gravity waves can interact. On the one hand, long internal waves imply a slow varying shear current that modifies the propagation of surface waves. Surface waves generated by the atmosphere can, on the other hand, excite internal waves by nonlinear interaction. Thereby a surface wave packet consisting of two close frequencies can resonate with a low frequency internal wave (Phillips, 1966). From a theoretical point of view, the latter has been studied intensively by using a 2-layer model, i.e. a surface layer with a strong density contrast and an internal layer with a comparable weak density contrast (Ball, 1964; Craig et al., 2010). In the present work we analyse the wave coupling for a continuously stratified fluid using a fully non-linear 2D numerical model (OpenFoam) and compare this with laboratory experiments (see Lewis et al. 1974). Surface wave modes are used as initial condition and the time development of the dominant surface and internal waves are studied by spectral and harmonic analysis. For the simple geometry of a box, the results are compared with analytical spectra of surface and gravity waves. Ball, F.K. 1964: Energy transfer between external and internal gravity waves. J. Fluid Mech. 19, 465. Craig, W., Guyenne, P., Sulem, C. 2010: Coupling between internal and surface waves. Natural Hazards 57, 617-642. Lewis, J.E., Lake, B.M., Ko, D.R.S 1974: On the interaction of internal waves and surfacr gravity waves, J. Fluid Mech. 63, 773-800. Phillips, O.M. 1966: The dynamics of the upper ocean, Cambridge University Press, 336pp.

  5. Wave turbulence in a two-layer fluid: coupling between free surface and interface waves

    CERN Document Server

    Issenmann, Bruno; Falcon, Eric

    2016-01-01

    We experimentally study gravity-capillary wave turbulence on the interface between two immiscible fluids of close density with free upper surface. We locally measure the wave height at the interface between both fluids by means of a highly sensitive laser Doppler vibrometer. We show that the inertial range of the capillary wave turbulence regime is significantly extended when the upper fluid depth is increased: The crossover frequency between the gravity and capillary wave turbulence regimes is found to decrease whereas the dissipative cut-off frequency of the spectrum is found to increase. We explain most of these observations by the progressive decoupling between waves propagating at the interface and the ones at the free surface, using the full dispersion relation of gravity-capillary waves in a two-layer fluid of finite depths.s.

  6. Accuracy of Satellite-Measured Wave Heights in the Australian Region for Wave Power Applications

    Science.gov (United States)

    Meath, Sian E.; Aye, Lu; Haritos, Nicholas

    2008-01-01

    This article focuses on the accuracy of satellite data, which may then be used in wave power applications. The satellite data are compared to data from wave buoys, which are currently considered to be the most accurate of the devices available for measuring wave characteristics. This article presents an analysis of satellite- (Topex/Poseidon) and…

  7. Decomposing variations of geopotential height in the troposphere and stratosphere into stationary and travelling waves

    Science.gov (United States)

    Guryanov, Vladimir; Eliseev, Alexey

    2016-07-01

    The ERA-Interim geopotential height in the Northern Hemisphere from November to March, 1992-2015 in the layer from between pressure levels 1000 mb and 1 mb is expanded into stationary and travelling zonal waves with zonal wavenumbers, k, from 1 to 10, and with periods, T, from 2 to 156 days (the so called Hayashi spectra). Among the studied waves, the largest amplitude is attained by the stationary and travelling waves with zonal wavenumber k=1 and with periods from 3 to 4 weeks in the upper stratosphere over the latitudinal belt 60-70oN. The stationary waves with k from 1 to 3 and with T from 2 to 3 weeks are most pronounced in the stratosphere. In turn, the largest amplitudes of the travelling waves with zonal wavenumbers k ≥ 5 are found in the troposphere. The dominant periods of the latter waves are about 1 week or slightly higher, and this dominant period basically decrease with increasing wavenumber. In the upper stratosphere, the eastward travelling waves generally dominate over westward ones. The only exception is the longest zonal mode with k=1, for which the amplitude of the westward travelling wave is larger than that for the eastward one. The period of the travelling waves dominating in the upper stratosphere is close to 3 weeks. In the upper troposphere, the amplitudes of the eastward waves with k from 4 to 10 is several-fold larger than those for their westward counterparts. The latter is reflected in the larger average wavenumber of the eastward travelling wave in comparison to that of the westarward one. The period of the gravest of the dominant travelling waves in the upper troposphere is close to one week, and it decreases to 2-4 days for the dominant travelling waves with k=8-10.

  8. Databases of surface wave dispersion

    Directory of Open Access Journals (Sweden)

    L. Boschi

    2005-06-01

    Full Text Available Observations of seismic surface waves provide the most important constraint on the elastic properties of the Earth’s lithosphere and upper mantle. Two databases of fundamental mode surface wave dispersion were recently compiled and published by groups at Harvard (Ekström et al., 1997 and Utrecht/Oxford (Trampert and Woodhouse, 1995, 2001, and later employed in 3-d global tomographic studies. Although based on similar sets of seismic records, the two databases show some significant discrepancies. We derive phase velocity maps from both, and compare them to quantify the discrepancies and assess the relative quality of the data; in this endeavour, we take careful account of the effects of regularization and parametrization. At short periods, where Love waves are mostly sensitive to crustal structure and thickness, we refer our comparison to a map of the Earth’s crust derived from independent data. On the assumption that second-order effects like seismic anisotropy and scattering can be neglected, we find the measurements of Ekström et al. (1997 of better quality; those of Trampert and Woodhouse (2001 result in phase velocity maps of much higher spatial frequency and, accordingly, more difficult to explain and justify geophysically. The discrepancy is partly explained by the more conservative a priori selection of data implemented by Ekström et al. (1997. Nevertheless, it becomes more significant with decreasing period, which indicates that it could also be traced to the different measurement techniques employed by the authors.

  9. Sea surface height anomaly and upper ocean temperature over the Indian Ocean during contrasting monsoons

    Science.gov (United States)

    Gera, Anitha; Mitra, A. K.; Mahapatra, D. K.; Momin, I. M.; Rajagopal, E. N.; Basu, Swati

    2016-09-01

    Recent research emphasizes the importance of the oceanic feedback to monsoon rainfall over the Asian landmass. In this study, we investigate the differences in the sea surface height anomaly (SSHA) and upper ocean temperature over the tropical Indian Ocean during multiple strong and weak monsoons. Analysis of satellite derived SSHA, sea surface temperature (SST) and ocean reanalysis data reveals that patterns of SSHA, SST, ocean temperature, upper ocean heat content (UOHC) and propagations of Kelvin and Rossby waves differ during strong and weak monsoon years. During strong monsoons positive SSH, SST and UOHC anomalies develop over large parts of north Indian Ocean whereas during weak monsoons much of the north Indian Ocean is covered with negative anomalies. These patterns can be used as a standard tool for evaluating the performance of coupled and ocean models in simulating & forecasting strong and weak monsoons. The rainfall over central India is found to be significantly correlated with SSHA over the regions (Arabian Sea and West central Indian Ocean and Bay of Bengal) where SSHA is positively large during strong monsoons. The SST-SSHA correlation is also very strong over the same area. The study reveals that much convection takes place over these regions during strong monsoons. In contrast during weak monsoons, convection takes place over eastern equatorial region. These changes in SST are largely influenced by oceanic Kelvin and Rossby waves. The Rossby waves initiated in spring at the eastern boundary propagate sub-surface heat content in the ocean influencing SST in summer. The SST anomalies modulate the Hadley circulation and the moisture transport thereby contributing to rainfall over central India. Therefore oceanic Kelvin and Rossby waves influence the rainfall over central India.

  10. Extreme Value Predictions using Monte Carlo Simulations with Artificially Increased Wave Height

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher

    2010-01-01

    accurate. In the present paper the generality of this relation is investigated, considering the probability that the design wave-induced hogging bending moment in a container ship is exceeded, accounting for both non-linear wave load effects (bow flare slamming) and hull flexibility (whipping vibrations)....... accurate result can be obtained by Monte Carlo simulations, but the necessary length of the time domain simulations for very low out-crossing rates might be prohibitively long. The present paper investigates whether the FORM property regarding the dependency of the reliability index on the significant wave...... to the actual significant wave height using this property. Previous results have been presented by Tonguc and Söding (1986), albeit in a more empirical way, and by Jensen (2010), where, considering the overturning of a jack-up rig, a slightly more general relation of the type ß=a(r)+b(r)/Hs was found to be very...

  11. Experimental investigation of the dependence of radar backscattering on wind speed, wind stress and wave height

    Science.gov (United States)

    Gogineni, S. P.; Katsaros, K. B.

    1989-01-01

    During summer 1988, radar measurements were performed in conjunction with detailed environmental observations on Lake Washington at the University of Washington Sand Point field station. Radar data were collected at 5.3 and 10 GHz for incidence angles between 30 and 60 deg with VV-polarization. The environmental measurements included wind speed and direction, large-wave heights, the high-frequency portion of the wave spectrum, humidity, and air and water temperatures. The small-scale wave spectrum was measured using a resistance wire gauge. The results show that backscatter increased with wind speed as expected. However, little difference was observed in the scattering coefficient for upwind and crosswind directions. The results also indicated an increase in the amplitude of small waves with friction velocity.

  12. Surface Acoustic Wave Frequency Comb

    CERN Document Server

    Savchenkov, A A; Ilchenko, V S; Seidel, D; Maleki, L

    2011-01-01

    We report on realization of an efficient triply-resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyper-parametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb observing the modulation of the modulated light escaping the resonator.

  13. The global structure of the annual and semiannual sea surface height variability from Geosat altimeter data

    Science.gov (United States)

    Jacobs, Gregg A.; Born, George H.; Parke, Mike E.; Allen, Patrick C.

    1992-01-01

    Two years of data from the Geosat Exact Repeat Mission are employed to study the annual and semiannual variability of sea-surface height on a global basis. The data are treated with atmospheric corrections and interpolations, and the orbit error of about 40 cm RMS is purged. The spatial variability of the Geosat data is constructed for particular frequencies, and the estimate of the M2 tidal error indicates that the error is aliased to 1.15 cycles/yr and has an unusual spatial pattern. Sine and cosine coefficients are derived for the annual and semiannual frequencies by means of a least squares fit yielding the amplitude and phase of the changes in sea-surface height. A 180-deg phase difference is noted between the Northern and Southern Hemispheres for the annual variability, and large-scale westward propagating waves are identified. The Geosat data also indicate the phase relationships between major current systems and the systems of variations at work in the Intertropical Convergence Zone.

  14. Automation of measurement of heights waves around a model ship; Mokeisen mawari no hako keisoku no jidoka

    Energy Technology Data Exchange (ETDEWEB)

    Ikehata, M.; Kato, M.; Yanagida, F. [Yokohama National University, Yokohama (Japan). Faculty of Engineering

    1997-10-01

    Trial fabrication and tests were performed on an instrument to automate measurement of heights of waves around a model ship. The currently used electric wave height measuring instrument takes long time for measurement, hence poor in efficiency. The method for processing optical images also has a problem in accuracy. Therefore, a computer controlled system was structured by using AC servo motors in driving the X and Y axes of a traverse equipment. Equipment was fabricated to automate the wave height measurement, in which four servo type wave height meters are installed on a moving rack in the lateral (Y-axial) direction so that wave heights to be measured by four meters can be measured automatically all at once. Wave heights can be measured continuously by moving the moving rack at a constant speed, verifying that wave shapes in longitudinal cross sections can be acquired by only one towing. Time required in the measurements using the instrument was 40 hours as a net time for fixed point measurement and 12 hours for continuous measurement, or 52 hours in total. On the other hand, the time may reach 240 hours for fixed point measurement when the conventional all-point manual traverse equipment is used. Enormous effects were obtained from automating the instrument. Collection of wave height data will continue also on tankers and other types of ships. 2 refs., 8 figs., 1 tab.

  15. ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. II. LAMB, SURFACE, AND CENTRIFUGAL WAVES

    Energy Technology Data Exchange (ETDEWEB)

    Peralta, J.; López-Valverde, M. A. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Imamura, T. [Institute of Space and Astronautical Science-Japan Aerospace Exploration Agency 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Read, P. L. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford (United Kingdom); Luz, D. [Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Piccialli, A., E-mail: peralta@iaa.es [LATMOS, UVSQ, 11 bd dAlembert, 78280 Guyancourt (France)

    2014-07-01

    This paper is the second in a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases where the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this second part, we study the waves' solutions when several atmospheric approximations are applied: Lamb, surface, and centrifugal waves. Lamb and surface waves are found to be quite similar to those in a geostrophic regime. By contrast, centrifugal waves turn out to be a special case of Rossby waves that arise in atmospheres in cyclostrophic balance. Finally, we use our results to identify the nature of the waves behind atmospheric periodicities found in polar and lower latitudes of Venus's atmosphere.

  16. A New Approach to Estimating the T-Year Return-Period Wave Height

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; SONG Wenpeng; GE Yong

    2011-01-01

    The paper introduces a new approach to estimating the T-year return-period wave height (TRPW),i.e.the wave height expected to occur in T-year,from two sets of observed extreme data and on the basis of the maximum entropy principle.The main points of the approach are as follows.1) A maximum entropy probability density function (PDF) for the extreme wave height H is derived from a Euler equation subject to some necessary and rational constraints.2) The parameters in the function are expressed in terms of the mth moment of H.3) This PDF is convenient to theoretical and practical applications as it is simple and its four parameters are easy to be determined from observed extreme data.An example is given for estimating the TRPW in 50 and 100 years by the present approach and by some currently used methods using observed data at two hydrographic stations.The comparison of the estimated results shows that the present approach is quite similar to the Pearson-Ⅲ and Gumbel methods.

  17. Surface height map estimation from a single image using convolutional neural networks

    Science.gov (United States)

    Zhou, Xiaowei; Zhong, Guoqiang; Qi, Lin; Dong, Junyu; Pham, Tuan D.; Mao, Jianzhou

    2017-02-01

    Surface height map estimation is an important task in high-resolution 3D reconstruction. This task differs from general scene depth estimation in the fact that surface height maps contain more high frequency information or fine details. Existing methods based on radar or other equipments can be used for large-scale scene depth recovery, but might fail in small-scale surface height map estimation. Although some methods are available for surface height reconstruction based on multiple images, e.g. photometric stereo, height map estimation directly from a single image is still a challenging issue. In this paper, we present a novel method based on convolutional neural networks (CNNs) for estimating the height map from a single image, without any equipments or extra prior knowledge of the image contents. Experimental results based on procedural and real texture datasets show the proposed algorithm is effective and reliable.

  18. Numerical modeling and validation of wave heights and directionality in the ice using WAVEWATCH III

    Science.gov (United States)

    Ardhuin, Fabrice; Dumont, Dany; Accensi, Mickael; Sevigny, Caroline; Boutin, Guillaume; Rogers, Erick

    2016-04-01

    The poorly understood attenuation of waves, the key dynamic effect that defines the width of the Marginal Ice Zone, has been attributed to the combined effect of wave scattering and wave dissipation. Because scattering and dissipation have very different effects on the directional distribution of wave energy, it is possible to better understand the balance between scattering and dissipation by an analysis of the width of the directional wave spectrum. We have thus introduced dissipation and scattering terms in the spectral wave model WAVEWATCH III, and an estimation of the maximum ice floe size. Academic and realistic simulations show that the energy level and directional spreading far into the Arctic pack ice (Wadhams and Doble 2009) can be well explained by dissipative processes without the need for scattering. The same is true of observed swells in the Southern Ocean (Ardhuin et al. 2015). However, the dissipation level required to explain the observed wave height goes from 2 in the southern ocean to 12 times the viscous dissipation under a smooth ice plate. This and other data suggest that broken ice causes less dissipation than a continuous ice cover, possibly due to the dissipation by creep inside the ice when it is not broken and bends. Work is under way to parameterize that effect using the estimated maximum ice floe size.

  19. Parabolic Wave Equation for Surface Water Waves.

    Science.gov (United States)

    1986-11-01

    extended to wave propagation problems in other fields of physical sciences, such as nonlinear optics ( Svelto , 1974), plasma physics (Karpman, 1975...34 Journal of Fluid Mechanics, Vol. 72, pp. 373-384. Svelto , 0., 1974, Progress in Optics, North-Holland Pub., Chapter 1, pp. 1-51. Tappert, F.D., 1977, "The

  20. A Study on the Relationships among Surface Variables to Adjust the Height of Surface Temperature for Data Assimilation.

    Science.gov (United States)

    Kang, J. H.; Song, H. J.; Han, H. J.; Ha, J. H.

    2016-12-01

    The observation processing system, KPOP (KIAPS - Korea Institute of Atmospheric Prediction Systems - Package for Observation Processing) have developed to provide optimal observations to the data assimilation system for the KIAPS Integrated Model (KIM). Currently, the KPOP has capable of processing almost all of observations for the KMA (Korea Meteorological Administration) operational global data assimilation system. The height adjustment of SURFACE observations are essential for the quality control due to the difference in height between observation station and model topography. For the SURFACE observation, it is usual to adjust the height using lapse rate or hypsometric equation, which decides values mainly depending on the difference of height. We have a question of whether the height can be properly adjusted following to the linear or exponential relationship solely with regard to the difference of height, with disregard the atmospheric conditions. In this study, firstly we analyse the change of surface variables such as temperature (T2m), pressure (Psfc), humidity (RH2m and Q2m), and wind components (U and V) according to the height difference. Additionally, we look further into the relationships among surface variables . The difference of pressure shows a strong linear relationship with difference of height. But the difference of temperature according to the height shows a significant correlation with difference of relative humidity than with the height difference. A development of reliable model for the height-adjustment of surface temperature is being undertaken based on the preliminary results.

  1. Calibration of HY-2A satellite significant wave heights within situ observation

    Institute of Scientific and Technical Information of China (English)

    PENG Hailong; LIN Mingsen

    2016-01-01

    Significant wave height (SWH) can be computed from the returning waveform of radar altimeter, this parameter is only raw estimates if it does not calibrate. But accurate calibration is important for all applications, especially for climate studies. HY-2a altimeter has been operational since April 2012 and its products are available to the scientific community. In this work, SWH data from HY-2A altimeters are calibrated againstin situ buoy data from the National Data Buoy Center (NDBC), Distinguished from previous calibration studies which generally regarded buoy data as "truth", the work of calibration for HY-2A altimeter wave data againstin situ buoys was applied a more sophisticated statistical technique—the total least squares (TLS) method which can take into account errors in both variables. We present calibration results for HY-2A radar altimeter measurement of wave height against NDBC buoys. In addition, cross-calibration for HY-2A and Jason-2 wave data are talked over and the result is given.

  2. Non-conventional modeling of extreme significant wave height through random sets

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi; LAM Jasmine Siu Lee

    2014-01-01

    The analysis and design of offshore structures necessitates the consideration of wave loads. Realistic model-ing of wave loads is particularly important to ensure reliable performance of these structures. Among the available methods for the modeling of the extreme significant wave height on a statistical basis, the peak over threshold method has attracted most attention. This method employs Poisson process to character-ize time-varying properties in the parameters of an extreme value distribution. In this paper, the peak over threshold method is reviewed and extended to account for subjectivity in the modeling. The freedom in selecting the threshold and the time span to separate extremes from the original time series data is incorpo-rated as imprecision in the model. This leads to an extension from random variables to random sets in the probabilistic model for the extreme significant wave height. The extended model is also applied to different periods of the sampled data to evaluate the significance of the climatic conditions on the uncertainties of the parameters.

  3. Low frequency variability of the Indian Ocean from TOPEX/POSEIDON sea surface height anomalies

    Digital Repository Service at National Institute of Oceanography (India)

    Somayajulu, Y.K.; Murty, V.S.N.; Sarma, Y.V.B.

    The sea surface height (SSH) anomalies derived from TOPEX/POSEIDON altimeter have been utilized to study the variability of surface circulation in the Indian Ocean during 1993-1999. The Western Bay, southeastern Arabian Sea, regions off Somalia...

  4. A Refined Method for Estimating the Annual Extreme Wave Heights at A Project Site

    Institute of Scientific and Technical Information of China (English)

    徐德伦; 范海梅; 张军

    2003-01-01

    This paper presents a refined method for estimating the annual extreme wave heights at a coastal or offshore project site on the basis of the data acquired at some nearby routine hydrographic stations. This method is based on the orthogonality principle in linear mean square estimation of stochastic processes. The error of the method is analyzed and compared with that of the conventional method. It is found that the method is able to effectively reduce the error so long as some feasible measures are adopted. A simulated test of the method has been conducted in a large-scale wind-wave flume. The test results are in good agreement with those given by theoretical error analysis. A scheme to implement the method is proposed on the basis of error analysis. The scheme is so designed as to reduce the estimation error as far as possible. This method is also suitable to utilizing satellite wave data for the estimation.

  5. Surface waves on metal-dielectric metamaterials

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee;

    2016-01-01

    of surface waves and, therefore, can serve as a platform allowing many applications for surface photonics. Most of these surface waves are directional and their propagation direction is sensitive to permittivities of the media forming the interface. Hence, their propagation can be effectively controlled...... by changing a wavelength or material parameters. We discover that two new types of surface waves with complex dispersion exist for a uniaxial medium with both negative ordinary and extraordinary permittivities. Such new surface wave solutions originate from the anisotropic permittivities of the uniaxial media......, resulting in unique hyperbolic–like wavevector dependencies....

  6. Characteristics of the large-height swell-like waves on the east coast of Korea

    Science.gov (United States)

    Oh, S.-H.; Jeong, W.-M.; Baek, W.-D.

    2012-04-01

    On the east coast of Korean peninsula, unusually high swell-like waves are occasionally observed several times during the winter season. These high swell-like waves are not related to the northwest monsoon that is typical in winter season, but are generated when strong northeasters blow continuously over the East Sea of Korea. In recent years, exceptionally high swell-like waves compared to the past observation record has attacked the east coast of Korean peninsula and caused severe casualties and damages of ships and coastal structures. Taking a few examples, abnormally high swell-waves of Hs =9.69 m were observed near Sokcho harbor on October 2006. More recently on the first day of Year 2011, large-height swell-like waves of Hs = 6.7 m visited at Jukbyeon port. At the present, the occurrence of such high swell-like waves are not fully predicted and only partially included in the normal weather forecast. Hence, researchers have much interest in improving understanding of the detailed generation mechanism of the high swell-like waves and predicting its occurrence. In this presentation, the characteristics of the high swell-like waves occurred on the first day of 2011 will be reported, with some supplementary results of the other big wave events that occurred previously. The New Year wave was monitored at 12 measuring stations simultaneously along the east coast. By analyzing these wave data with the corresponding meteorological data provided by Korean Meteorological Agency (KMA), major characteristics of these waves were clarified in some detail. The reason for appearance of the high swell-like waves was found to be due to the long-lasting strong northeasters in the East Sea, which was formed as a result of the low pressure trough in the vicinity of the extra-tropical low pressure system that advances to East Sea from the China inland with decreasing its central pressure. Such a strong low pressure system can be occasionally developed in winter season and may cause

  7. Broadband wave manipulation in surface-wave photonic crystal

    CERN Document Server

    Gao, Zhen

    2016-01-01

    The ability to perfectly guide surface electromagnetic waves around ultra-sharp corners without back-scattering and radiation is in great demand for various photonic and plasmonic applications. This is fundamentally difficult to realize because of the dramatic momentum mismatch and wave nature of radiation at the sharp corners. Here we experimentally demonstrate that a simple photonic structure, a periodic square array of metallic cylinders standing on a metal surface, can behaves as a surface-wave photonic crystal with complete photonic band gap to overcome this bottleneck simply. A line-defect waveguide can support and guide surface waves around ultra-sharp corners without perceptible radiation and reflection, achieving almost perfect transmission efficiency in a broad frequency range. We also demonstrate an ideal T-shaped splitter to split input surface waves equally into two arms and a square radiation-suppressed plasmonic open resonator with high quality factors by simply inducing line-defects in this fu...

  8. Linear surface capillary-gravity short-crested waves on a current

    Institute of Scientific and Technical Information of China (English)

    HUANG Hu

    2008-01-01

    One of the forward situations in the study of water waves is the basic three-dimensional surface wave motion of short-crested waves. Capillary waves result in rich effects concerned closely with remote sensing in the open ocean. Ocean currents experience a complete process in surface wave motion. Based on the above ideas, a linear dynamical system of surface capillary-gravity short-crested waves is developed by considering the current effects, thus leading to the following analytical expressions of the kinematic and dynamic variables: the wave height, the wave steepness, the phase velocity, the wave-particle velocities, accelerations and trajectories and the wave pressure. A number of the classi-cal, typical and latest special wave cases can arise from these expressions.

  9. The impact of North Atlantic wind and cyclone trends on European precipitation and significant wave height in the Atlantic.

    Science.gov (United States)

    Trigo, Ricardo M; Valente, Maria A; Trigo, Isabel F; Miranda, Pedro M A; Ramos, Alexandre M; Paredes, Daniel; García-Herrera, Ricardo

    2008-12-01

    An analysis of the frequency of cyclones and surface wind velocity for the Euro-Atlantic sector is performed by means of an objective methodology. Monthly and seasonal trends of cyclones and wind speed magnitude are computed and trends between 1960 and 2000 evaluated. Results reveal a significant frequency decrease (increase) in the western Mediterranean (Greenland and Scandinavia), particularly in December, February, and March. Seasonal and monthly analysis of wind magnitude trends shows similar spatial patterns. We show that these changes in the frequency of low-pressure centers and the associated wind patterns are partially responsible for trends in the significant height of waves. Throughout the extended winter months (October-March), regions with positive (negative) wind magnitude trends, of up to 5 cm/s/year, often correspond to regions of positive (negative) significant wave height trends. The cyclone and wind speed trends computed for January-March are well matched by the corresponding trends in significant wave height, with February being the month with the highest trends (negative south of lat 50 degrees N up to -3 cm/year, and positive up to 5 cm/year just north of Scotland). Trends in European precipitation are assessed using the Climatic Research Unit data set. The results of the assessment emphasize the link with the corresponding tendencies of cyclone frequencies. Finally, it is shown that these changes are associated, to a large extent, with the preferred phases of major large-scale atmospheric circulation modes, particularly with the North Atlantic Oscillation, the eastern Atlantic pattern, and the Scandinavian pattern.

  10. Dyakonov surface waves in lossy metamaterials

    CERN Document Server

    Sorni, A J; Zapata-Rodríguez, C J; Miret, J J

    2015-01-01

    We analyze the existence of localized waves in the vicinities of the interface between two dielectrics, provided one of them is uniaxial and lossy. We found two families of surface waves, one of them approaching the well-known Dyakonov surface waves (DSWs). In addition, a new family of wave fields exists which are tightly bound to the interface. Although its appearance is clearly associated with the dissipative character of the anisotropic material, the characteristic propagation length of such surface waves might surpasses the working wavelength by nearly two orders of magnitude.

  11. NUMERICAL SIMULATION OF SEA SURFACE DIRECTIONAL WAVE SPECTRA UNDER TYPHOON WIND FORCING

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Numercial simulation of sea surface directional wave spectra under typhoon wind forcing in the South China Sea (SCS) was carreid out using the WAVEWATCH-III wave model. The simulation was run for 210 h until the Typhoon Damrey (2005) approached Vietnam. The simulated data were compared with buoy observations, which were obtained in the northwest sea area of Hainan Island. The results show that the significant wave height, wave direction, wave length and frequency spetra agree well with buoy observations. The spatial characteristics of the signifciant wave height, mean wave period, mean wave length, wave age and directional spectra depend on the relative position from the typhoon center. Also, the misalignment between local wind and wave directions were investigated.

  12. Surface air quality implications of volcanic injection heights

    Science.gov (United States)

    Thomas, Manu Anna; Brännström, Niklas; Persson, Christer; Grahn, Håkan; von Schoenberg, Pontus; Robertson, Lennart

    2017-10-01

    Air quality implications of volcanic eruptions have gained increased attention recently in association with the 2010 Icelandic eruption that resulted in the shut-down of European air space. The emission amount, injection height and prevailing weather conditions determine the extent of the impact through the spatio-temporal distribution of pollutants. It is often argued that in the case of a major eruption in Iceland, like Laki in 1783-1784, that pollutants injected high into the atmosphere lead to substantially increased concentrations of sulfur compounds over continental Europe via long-range transport in the jet stream and eventual large-scale subsidence in a high-pressure system. Using state-of-the-art simulations, we show that the air quality impact of Icelandic volcanoes is highly sensitive to the injection height. In particular, it is the infinitesimal injections into the lower half of the troposphere, rather than the substantial injections into the upper troposphere/lower stratosphere that contribute most to increased pollutant concentrations, resulting in atmospheric haze over mainland Europe/Scandinavia. Besides, the persistent high pressure system over continental Europe/Scandinavia traps the pollutants from dispersing, thereby prolonging the haze.

  13. Generation of long subharmonic internal waves by surface waves

    Science.gov (United States)

    Tahvildari, Navid; Kaihatu, James M.; Saric, William S.

    2016-10-01

    A new set of Boussinesq equations is derived to study the nonlinear interactions between long waves in a two-layer fluid. The fluid layers are assumed to be homogeneous, inviscid, incompressible, and immiscible. Based on the Boussinesq equations, an analytical model is developed using a second-order perturbation theory and applied to examine the transient evolution of a resonant triad composed of a surface wave and two oblique subharmonic internal waves. Wave damping due to weak viscosity in both layers is considered. The Boussinesq equations and the analytical model are verified. In contrast to previous studies which focus on short internal waves, we examine long waves and investigate some previously unexplored characteristics of this class of triad interaction. In viscous fluids, surface wave amplitudes must be larger than a threshold to overcome viscous damping and trigger internal waves. The dependency of this critical amplitude as well as the growth and damping rates of internal waves on important parameters in a two-fluid system, namely the directional angle of the internal waves, depth, density, and viscosity ratio of the fluid layers, and surface wave amplitude and frequency is investigated.

  14. Symmetric waves are traveling waves for a shallow water equation for surface waves of moderate amplitude

    OpenAIRE

    Geyer, Anna

    2016-01-01

    Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.

  15. Symmetric waves are traveling waves for a shallow water equation for surface waves of moderate amplitude

    OpenAIRE

    Geyer, Anna

    2016-01-01

    Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.

  16. Experimental study of breaking and energy dissipation in surface waves

    Science.gov (United States)

    Ruiz Chavarria, Gerardo; Le Gal, Patrice; Le Bars, Michael

    2014-11-01

    We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as ɛ = H/ λ (where H is the wave height and λ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when ɛ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry. G. Ruiz Chavarria acknowledges DGAPA-UNAM by support under Project IN 116312 (Vorticidad y ondas no lineales en fluidos).

  17. A fuzzy quantification approach of uncertainties in an extreme wave height modeling

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi; CAO Yingyi

    2015-01-01

    A non-traditional fuzzy quantification method is presented in the modeling of an extreme significant wave height. First, a set of parametric models are selected to fit time series data for the significant wave height and the extrapolation for extremes are obtained based on high quantile estimations. The quality of these results is compared and discussed. Then, the proposed fuzzy model, which combines Poisson process and gener-alized Pareto distribution (GPD) model, is applied to characterizing the wave extremes in the time series data. The estimations for a long-term return value are considered as time-varying as a threshold is regarded as non-stationary. The estimated intervals coupled with the fuzzy theory are then introduced to construct the probability bounds for the return values. This nontraditional model is analyzed in comparison with the traditional model in the degree of conservatism for the long-term estimate. The impact on the fuzzy bounds of extreme estimations from the non stationary effect in the proposed model is also investigated.

  18. Surface Shear, Persistent Wave Groups and Rogue Waves

    CERN Document Server

    Chafin, Clifford

    2014-01-01

    We investigate the interaction of waves with surface flows by considering the full set of conserved quantities, subtle but important surface elevations induced by wave packets and by directly considering the necessary forces to prevent packet spreading in the deep water limit. Narrow surface shear flows are shown to exert strong localizing and stabilizing forces on wavepackets to maintain their strength and amplify their intensity even in the linear regime. Necessary criticisms of some earlier notions of stress and angular momentum of waves are included and we argue that nonlinearity enters the system in a way that makes the formation of rogue waves nonperturbative. Quantitative bounds on the surface shear flow necessary to stabilize packets of any wave amplitude are given.

  19. Characters of surface deformation and surface wave in thermal capillary convection

    Institute of Scientific and Technical Information of China (English)

    DUAN; Li; KANG; Qi; HU; Wenrei

    2006-01-01

    In the field of fluid mechanics, free surface phenomena is one of the most important physical processes. In the present research work, the surface deformation and surface wave caused by temperature difference of sidewalls in a rectangular cavity have been investigated. The horizontal cross-section of the container is 52 mm×42 mm, and there is a silicon oil layer of height 3.5 mm in the experimental cavity. Temperature difference between the two side walls of the cavity is increased gradually, and the flow on the liquid layer will develop from stable convection to un-stable convection. An optical diagnostic system consisting of a modified Michelson interferometer and image processor has been developed for study of the surface deformation and surface wave of thermal capillary convection. The Fourier transformation method is used to interferometer fringe analysis. The quantitative results of surface deformation and surface wave have been calculated from a serial of the interference fringe patterns. The characters of surface deformation and surface wave have been obtained. They are related with temperature gradient and surface tension. Surface deformation is fluctuant with time, which shows the character of surface wave. The cycle period of the wave is 4.8 s, and the amplitudes are from 0 to 0.55 μm. The phase of the wave near the cool side of the cavity is opposite and correlative to that near the hot side. The present experiment proves that the surface wave of thermal capillary convection exists on liquid free surface, and it is wrapped in surface deformation.

  20. The maximum sloshing wave height evaluation in cylindrical metallic tanks by numerical means

    Directory of Open Access Journals (Sweden)

    Manser Walid Samir

    2017-01-01

    Full Text Available The metallic cylindrical storage tanks are very common structures in the field of civil engineering; These facilities are especially used in the industry in which they are used to store all kinds of products-which are for the most toxic or flammable. The tanks are also used in the storing of drinking water. When earthquakes, these structures must be strictly maintained in order to avoid that they lose their precious contents causing reactions that can cause more damage than the earthquake itself. In this study, the effects of the liquid height, the geometric parameters of tanks in the variation of the maximum sloshing wave height are studied: For this purpose, the software ANSYS V11.0 is used for modelling the tanks, the results found are compared with thus given in the Euro code 8

  1. Improvements on Mean Free Wave Surface Modeling

    Institute of Scientific and Technical Information of China (English)

    董国海; 滕斌; 程亮

    2002-01-01

    Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream function wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave breaker index in the calculation of wave breaking dissipation. The model is based on Roelvink (1993), but the numerical techniques used in the solution are based on the Weighted-Average Flux (WAF) method (Watson et al., 1992), with Time-Operator-Splitting (TOS) used for the treatment of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modeling wave set-up. The short wave (or incident primary wave) energy equation issolved by use of a traditional Lax-Wendroff technique. The present model is found to be satisfactory compared with the measurements conducted by Stive (1983).

  2. Managing Information Uncertainty in Wave Height Modeling for the Offshore Structural Analysis through Random Set

    Directory of Open Access Journals (Sweden)

    Keqin Yan

    2017-01-01

    Full Text Available This chapter presents a reliability study for an offshore jacket structure with emphasis on the features of nonconventional modeling. Firstly, a random set model is formulated for modeling the random waves in an ocean site. Then, a jacket structure is investigated in a pushover analysis to identify the critical wave direction and key structural elements. This is based on the ultimate base shear strength. The selected probabilistic models are adopted for the important structural members and the wave direction is specified in the weakest direction of the structure for a conservative safety analysis. The wave height model is processed in a P-box format when it is used in the numerical analysis. The models are applied to find the bounds of the failure probabilities for the jacket structure. The propagation of this wave model to the uncertainty in results is investigated in both an interval analysis and Monte Carlo simulation. The results are compared in context of information content and numerical accuracy. Further, the failure probability bounds are compared with the conventional probabilistic approach.

  3. A background error covariance model of significant wave height employing Monte Carlo simulation

    Institute of Scientific and Technical Information of China (English)

    GUO Yanyou; HOU Yijun; ZHANG Chunmei; YANG Jie

    2012-01-01

    The quality of background error statistics is one of the key components for successful assimilation of observations in a numerical model.The background error covariance(BEC)of ocean waves is generally estimated under an assumption that it is stationary over a period of time and uniform over a domain.However,error statistics are in fact functions of the physical processes governing the meteorological situation and vary with the wave condition.In this paper,we simulated the BEC of the significant wave height(SWH)employing Monte Carlo methods.An interesting result is that the BEC varies consistently with the mean wave direction(MWD).In the model domain,the BEC of the SWH decreases significantly when the MWD changes abruptly.A new BEC model of the SWH based on the correlation between the BEC and MWD was then developed.A case study of regional data assimilation was performed,where the SWH observations of buoy 22001 were used to assess the SWH hindcast.The results show that the new BEC model benefits wave prediction and allows reasonable approximations of anisotropy and inhomogeneous errors.

  4. Inter-annual variability of sea surface temperature, wind speed and sea surface height anomaly over the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; Pankajakshan, T.; Sathe, P.V.

    have made an attempt to study the annual and inter-annual variability of certain prominent processes occurring over the tropical Indian Ocean. The monthly mean values of Wind Speed (FSU), Sea Surface Temperature (REYNOLDS) and Sea Surface Height Anomaly...

  5. nowCOAST's Map Service for NOAA NWS NDFD Gridded Forecasts of Significant Wave Height (feet) (Time Offsets)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Map Information: This nowCOAST time-offsets map service provides maps depicting the NWS significant wave height forecasts from the National Digital Forecast Database...

  6. Reflection and transmission of regular waves at a surface-pitching slotted barrier

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The interactions between regular surface waves and a surface-pitching slotted barrier are investigated both analytically and experimentally.A quasi-linear theory is developed using the eigenfunction expansion method.The energy dissipation within the barriers is modeled by a quadratic friction factor, and an equivalent linear dissipation coefficient, which is depth-varying, wave-height dependent, is introduced to linearize the matching condition at the surface-pitching barrier.By comparing the theoretical results with laboratory experiments, it is shown that the present method can satisfactorily predict the variation of the reflection and transmission coefficients with wave height.

  7. A Wave Modulation Model of Ripples over Long Surface Waves

    Institute of Scientific and Technical Information of China (English)

    CONG Peixiu; ZHENG Guizhen

    2011-01-01

    A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modulation model is proposed. In this model, the wind surface stress modulation is related to the modulation of tipple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the tipple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves.

  8. Wave scattering from statistically rough surfaces

    CERN Document Server

    Bass, F G; ter Haar, D

    2013-01-01

    Wave Scattering from Statistically Rough Surfaces discusses the complications in radio physics and hydro-acoustics in relation to wave transmission under settings seen in nature. Some of the topics that are covered include radar and sonar, the effect of variations in topographic relief or ocean waves on the transmission of radio and sound waves, the reproduction of radio waves from the lower layers of the ionosphere, and the oscillations of signals within the earth-ionosphere waveguide. The book begins with some fundamental idea of wave transmission theory and the theory of random processes a

  9. Step-height measurements on sand surfaces: A comparison between optical scanner and coordinate measuring machine

    DEFF Research Database (Denmark)

    Mohaghegh, Kamran; Yazdanbakhsh, Seyed Alireza; Tiedje, Niels Skat

    2016-01-01

    the same routine to touch the different positions on the polygonised mesh. Each measurement was repeated 5 times. The results of step height measurements on sand surfaces showed a maximum error of ± 12 µm for CMM, while scanner shows only ± 4 µm. Generally speaking, optical step height values were measured...

  10. Interaction of Waves, Surface Currents, and Turbulence: the Application of Surface-Following Coordinate Systems

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Surface waves comprise an important aspect of the interaction between the atmosphere and the ocean, so a dynamically consistent framework for modelling atmosphere-ocean interaction must take account of surface waves, either implicitly or explicitly. In order to calculate the effect of wind forcing on waves and currents, and vice versa, it is necessary to employ a consistent formulation of the energy and momentum balance within the airflow, wave field, and water column. It is very advantageous to apply surface-following coordinate systems, whereby the steep gradients in mean flow properties near the air-water interface in the cross-interface direction may be resolved over distances which are much smaller than the height of the waves themselves. We may account for the waves explicitly by employing a numerical spectral wave model, and applying a suitable theory of wave-mean flow interaction. If the mean flow is small compared with the wave phase speed, perturbation expansions of the hydrodynamic equations in a Lagrangian or generalized Lagrangian mean framework are useful: for stronger flows, such as for wind blowing over waves, the presence of critical levels where the mean flow velocity is equal to the wave phase speed necessitates the application of more general types of surface-following coordinate system. The interaction of the flow of air and water and associated differences in temperature and the concentration of various substances (such as gas species) gives rise to a complex boundary-layer structure at a wide range of vertical scales, from the sub-millimetre scales of gaseous diffusion, to several tens of metres for the turbulent Ekman layer. The balance of momentum, heat, and mass is also affected significantly by breaking waves, which act to increase the effective area of the surface for mass transfer, and increase turbulent diffusive fluxes via the conversion of wave energy to turbulent kinetic energy.

  11. Constraining Depths and Wave Heights for Titan's lakes with Cassini RADAR Data

    Science.gov (United States)

    Wye, L.; Zebker, H. A.; Hayes, A. G.; Lorenz, R. D.; Notarnicola, C.; Ventura, B.; Casarano, D.; Cassini RADAR Team

    2010-12-01

    Ontario Lacus' near shore regions, we evaluate partial depth profiles for these two northern lakes. We assume the dielectric properties to apply uniformly across the lake volumes, but we explore the effects that differing dielectric properties has on the depth interpretations. In our analysis, we allow for scatter from small-scale waves on the surface of these lakes. We find that the wave activity, assumed uniform across the lake, has to be less than 1 mm in rms height according to small perturbation theory. These results are consistent with the analysis of altimetry echoes from Ontario Lacus (Wye et al., GRL 2009) and suggest either that the wind is not strong enough at the time of the observations to initiate significant wave activity or that the liquid properties are quite different from what has been assumed (Lorenz et al., Icarus 2010). The outputs of this analysis will also be compared with those of another double layer model applied to SAR data. This model uses a Bayesian inversion algorithm to provide the mean values and the PDFs of the single parameter estimates, including wind speeds and optical thickness (Notarnicola et. al, IEEE TGRS 2009).

  12. Estimating Aerodynamic Parameters of Urban-Like Surfaces with Heterogeneous Building Heights

    Science.gov (United States)

    Millward-Hopkins, J. T.; Tomlin, A. S.; Ma, L.; Ingham, D.; Pourkashanian, M.

    2011-12-01

    There are many geometrical factors than can influence the aerodynamic parameters of urban surfaces and hence the vertical wind profiles found above. The knowledge of these parameters has applications in numerous fields, such as dispersion modelling, wind loading calculations, and estimating the wind energy resource at urban locations. Using quasi-empirical modelling, we estimate the dependence of the aerodynamic roughness length and zero-plane displacement for idealized urban surfaces, on the two most significant geometrical characteristics; surface area density and building height variability. A validation of the spatially-averaged, logarithmic wind profiles predicted by the model is carried out, via comparisons with available wind-tunnel and numerical data for arrays of square based blocks of uniform and heterogeneous heights. The model predicts two important properties of the aerodynamic parameters of surfaces of heterogeneous heights that have been suggested by experiments. Firstly, the zero-plane displacement of a heterogeneous array can exceed the surface mean building height significantly. Secondly, the characteristic peak in roughness length with respect to surface area density becomes much softer for heterogeneous arrays compared to uniform arrays, since a variation in building height can prevent a skimming flow regime from occurring. Overall the simple model performs well against available experimental data and may offer more accurate estimates of surface aerodynamic parameters for complex urban surfaces compared to models that do not include height variability.

  13. Unidirectional propagation of designer surface acoustic waves

    CERN Document Server

    Lu, Jiuyang; Ke, Manzhu; Liu, Zhengyou

    2014-01-01

    We propose an efficient design route to generate unidirectional propagation of the designer surface acoustic waves. The whole system consists of a periodically corrugated rigid plate combining with a pair of asymmetric narrow slits. The directionality of the structure-induced surface waves stems from the destructive interference between the evanescent waves emitted from the double slits. The theoretical prediction is validated well by simulations and experiments. Promising applications can be anticipated, such as in designing compact acoustic circuits.

  14. Electromagnetic backscattering from one-dimensional drifting fractal sea surface I: Wave-current coupled model

    Science.gov (United States)

    Tao, Xie; Shang-Zhuo, Zhao; William, Perrie; He, Fang; Wen-Jin, Yu; Yi-Jun, He

    2016-06-01

    To study the electromagnetic backscattering from a one-dimensional drifting fractal sea surface, a fractal sea surface wave-current model is derived, based on the mechanism of wave-current interactions. The numerical results show the effect of the ocean current on the wave. Wave amplitude decreases, wavelength and kurtosis of wave height increase, spectrum intensity decreases and shifts towards lower frequencies when the current occurs parallel to the direction of the ocean wave. By comparison, wave amplitude increases, wavelength and kurtosis of wave height decrease, spectrum intensity increases and shifts towards higher frequencies if the current is in the opposite direction to the direction of ocean wave. The wave-current interaction effect of the ocean current is much stronger than that of the nonlinear wave-wave interaction. The kurtosis of the nonlinear fractal ocean surface is larger than that of linear fractal ocean surface. The effect of the current on skewness of the probability distribution function is negligible. Therefore, the ocean wave spectrum is notably changed by the surface current and the change should be detectable in the electromagnetic backscattering signal. Project supported by the National Natural Science Foundation of China (Grant No. 41276187), the Global Change Research Program of China (Grant No. 2015CB953901), the Priority Academic Development Program of Jiangsu Higher Education Institutions (PAPD), Program for the Innovation Research and Entrepreneurship Team in Jiangsu Province, China, the Canadian Program on Energy Research and Development, and the Canadian World Class Tanker Safety Service.

  15. The mean sea surface height and geoid along the Geosat subtrack from Bermuda to Cape Cod

    Science.gov (United States)

    Kelly, Kathryn A.; Joyce, Terrence M.; Schubert, David M.; Caruso, Michael J.

    1991-07-01

    Measurements of near-surface velocity and concurrent sea level along an ascending Geosat subtrack were used to estimate the mean sea surface height and the Earth's gravitational geoid. Velocity measurements were made on three traverses of a Geosat subtrack within 10 days, using an acoustic Doppler current profiler (ADCP). A small bias in the ADCP velocity was removed by considering a mass balance for two pairs of triangles for which expendable bathythermograph measurements were also made. Because of the large curvature of the Gulf Stream, the gradient wind balance was used to estimate the cross-track component of geostrophic velocity from the ADCP vectors; this component was then integrated to obtain the sea surface height profile. The mean sea surface height was estimated as the difference between the instantaneous sea surface height from ADCP and the Geosat residual sea level, with mesoscale errors reduced by low-pass filtering. The error estimates were divided into a bias, tilt, and mesoscale residual; the bias was ignored because profiles were only determined within a constant of integration. The calculated mean sea surface height estimate agreed with an independent estimate of the mean sea surface height from Geosat, obtained by modeling the Gulf Stream as a Gaussian jet, within the expected errors in the estimates: the tilt error was 0.10 m, and the mesoscale error was 0.044 m. To minimize mesoscale errors in the estimate, the alongtrack geoid estimate was computed as the difference between the mean sea level from the Geosat Exact Repeat Mission and an estimate of the mean sea surface height, rather than as the difference between instantaneous profiles of sea level and sea surface height. In the critical region near the Gulf Stream the estimated error reduction using this method was about 0.07 m. Differences between the geoid estimate and a gravimetric geoid were not within the expected errors: the rms mesoscale difference was 0.24 m rms.

  16. Measuring the Absolute Height and Profile of the Mesospheric Sodium Layer using a Continuous Wave Laser

    CERN Document Server

    Butler, D J; Redfern, R M; Ageorges, N; Fews, H

    2003-01-01

    We have developed and tested a novel method, based on LIDAR, of measuring the height and profile of the mesospheric sodium layer using a continuous wave laser. It is more efficient than classical LIDAR as the laser is on for 50% of the time, and so can in principle be used during laser guide star adaptive optics observations. It also has significant advantages over direct imaging techniques because it does not require a second telescope, is almost independent of the atmospheric conditions, and avoids triangulation problems in determining the height. In the long term, regular monitoring using this method would allow a valuable database of sodium layer profiles, heights, and return flux measurements to be built up which would enable observatory staff astronomers to schedule observations optimally. In this paper we describe the original experiment carried out using the ALFA laser guide star system at Calar Alto Observatory in Spain. We validate the method by comparing the LIDAR results with those obtained from s...

  17. Regional Frequency Analysis of Significant Wave Heights Based on L-moments

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    L-moments are defined as linear combinations of probability-weighted moments. They are virtually unbiased for small samples, and perform well in parameter estimation, choice of the distribution type and regional analysis. The traditional methods of determining the design wave heights for planning marine structures use data only from the site of interest. Regional frequency analysis gives a new approach to estimate quantile by use of the homogeneous neighborhood information. A regional frequency analysis based on L-moments with a case study of the California coast is presented. The significant wave height data for the California coast is offered by NDBC. A 6-site region without 46023 is considered to be a homogeneous region, whose optimal regional distribution is Pearson Ⅲ. The test is conducted by a simulation process. The regional quantile is compared with the at-site quantile, and it is shown that efficient neighborhood information can be used via regional frequency analysis to give a reasonable estimation of the site without enough historical data.

  18. THE EFFECTS OF RADIATION STRESS ON WAVE HEIGHTS AND SEA LEVEL IN THE INTERACTION OF COUPLED WAVE-TIDE-SURGE IN THE COASTAL AREA

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Based on coastal high-resolution (2′×2′) coupled wave-tide-surge interaction numerical model, the effects of radiation stress on wave heights and sea level in the coastal area of Huanghe Delta were studied. By comparisons of simulated and measured wave heights and sea level for two mediately strong weather cases, it is demonstrated that the results simulated by coupled wave-tide-surge model are closer to the measured and particularly in excellent agreement in the extreme values of the wave heights and set-up. This study shows that the radiation stress can increase the wave heights maximally to 67cm and sea level to 40cm. It is also found that there are areas of over 50cm wave height increase and an area of over 20cm sea level increase in the Huanghe Delta coastal area, and this find may be very important in engineering. For this reason, it is suggested that in the practical engineering application, the coupled wave-tide-surge interaction numerical model should be prefered.

  19. Individual wave height distributions in the coastal zone: Measurements and simulations and the effect of directional spreading

    NARCIS (Netherlands)

    Van Vledder, G.P.; Ruessink, G.; Rijnsdorp, D.P.

    2013-01-01

    Characteristics of the individual wave height distribution in shallow water have been investigated using measured wave data and results of numerical simulations using the non-hydrostatic SWASH model. It is shown that the SWASH model is capable of reproducing the temporal and spatial variation of sur

  20. A Maximum-Entropy Compound Distribution Model for Extreme Wave Heights of Typhoon-Affected Sea Areas

    Institute of Scientific and Technical Information of China (English)

    WANG Li-ping; SUN Xiao-guang; LU Ke-bo; XU De-lun

    2012-01-01

    A new compound distribution model for extreme wave heights of typhoon-affected sea areas is proposed on the basis of the maximum-entropy principle.The new model is formed by nesting a discrete distribution in a continuous one,having eight parameters which can be determined in terms of observed data of typhoon occurrence-frequency and extreme wave heights by numerically solving two sets of equations derived in this paper.The model is examined by using it to predict the N-year return-periodwave height at two hydrology stations in the Yellow Sea,and the predicted results are compared with those predicted by use of some other compound distribution models.Examinations and comparisons show that the model has some advantages for predicting the N-year return-period wave height in typhoon-affected sea areas.

  1. Skeletonized wave-equation Qs tomography using surface waves

    KAUST Repository

    Li, Jing

    2017-08-17

    We present a skeletonized inversion method that inverts surface-wave data for the Qs quality factor. Similar to the inversion of dispersion curves for the S-wave velocity model, the complicated surface-wave arrivals are skeletonized as simpler data, namely the amplitude spectra of the windowed Rayleigh-wave arrivals. The optimal Qs model is then found that minimizes the difference in the peak frequencies of the predicted and observed Rayleigh wave arrivals using a gradient-based wave-equation optimization method. Solutions to the viscoelastic wave-equation are used to compute the predicted Rayleigh-wave arrivals and the misfit gradient at every iteration. This procedure, denoted as wave-equation Qs tomography (WQs), does not require the assumption of a layered model and tends to have fast and robust convergence compared to Q full waveform inversion (Q-FWI). Numerical examples with synthetic and field data demonstrate that the WQs method can accurately invert for a smoothed approximation to the subsur-face Qs distribution as long as the Vs model is known with sufficient accuracy.

  2. Wave-equation Qs Inversion of Skeletonized Surface Waves

    KAUST Repository

    Li, Jing

    2017-02-08

    We present a skeletonized inversion method that inverts surface-wave data for the Qs quality factor. Similar to the inversion of dispersion curves for the S-wave velocity model, the complicated surface-wave arrivals are skeletonized as simpler data, namely the amplitude spectra of the windowed Rayleigh-wave arrivals. The optimal Qs model is the one that minimizes the difference in the peak frequencies of the predicted and observed Rayleigh wave arrivals using a gradient-based wave-equation optimization method. Solutions to the viscoelastic wave-equation are used to compute the predicted Rayleigh-wave arrivals and the misfit gradient at every iteration. This procedure, denoted as wave-equation Qs inversion (WQs), does not require the assumption of a layered model and tends to have fast and robust convergence compared to full waveform inversion (FWI). Numerical examples with synthetic and field data demonstrate that the WQs method can accurately invert for a smoothed approximation to the subsurface Qs distribution as long as the Vs model is known with sufficient accuracy.

  3. Identification of the Rayleigh surface waves for estimation of viscoelasticity using the surface wave elastography technique.

    Science.gov (United States)

    Zhang, Xiaoming

    2016-11-01

    The purpose of this Letter to the Editor is to demonstrate an effective method for estimating viscoelasticity based on measurements of the Rayleigh surface wave speed. It is important to identify the surface wave mode for measuring surface wave speed. A concept of start frequency of surface waves is proposed. The surface wave speeds above the start frequency should be used to estimate the viscoelasticity of tissue. The motivation was to develop a noninvasive surface wave elastography (SWE) technique for assessing skin disease by measuring skin viscoelastic properties. Using an optical based SWE system, the author generated a local harmonic vibration on the surface of phantom using an electromechanical shaker and measured the resulting surface waves on the phantom using an optical vibrometer system. The surface wave speed was measured using a phase gradient method. It was shown that different standing wave modes were generated below the start frequency because of wave reflection. However, the pure symmetric surface waves were generated from the excitation above the start frequency. Using the wave speed dispersion above the start frequency, the viscoelasticity of the phantom can be correctly estimated.

  4. Skeletonized wave equation of surface wave dispersion inversion

    KAUST Repository

    Li, Jing

    2016-09-06

    We present the theory for wave equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. Similar to wave-equation travel-time inversion, the complicated surface-wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the (kx,ω) domain. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2D or 3D velocity models. This procedure, denoted as wave equation dispersion inversion (WD), does not require the assumption of a layered model and is less prone to the cycle skipping problems of full waveform inversion (FWI). The synthetic and field data examples demonstrate that WD can accurately reconstruct the S-wave velocity distribution in laterally heterogeneous media.

  5. Links of the significant wave height distribution in the Mediterranean sea with the Northern Hemisphere teleconnection patterns

    Directory of Open Access Journals (Sweden)

    P. Lionello

    2008-06-01

    Full Text Available This study analyzes the link between the SWH (Significant Wave Height distribution in the Mediterranean Sea during the second half of the 20th century and the Northern Hemisphere SLP (Sea Level Pressure teleconnection patterns.

    The SWH distribution is computed using the WAM (WAve Model forced by the surface wind fields provided by the ERA-40 reanalysis for the period 1958–2001. The time series of mid-latitude teleconnection patterns are downloaded from the NOAA web site. This study shows that several mid-latitude patterns are linked to the SWH field in the Mediterranean, especially in its western part during the cold season: East Atlantic Pattern (EA, Scandinavian Pattern (SCA, North Atlantic Oscillation (NAO, East Atlantic/West Russia Pattern (EA/WR and East Pacific/ North Pacific Pattern (EP/NP. Though the East Atlantic pattern exerts the largest influence, it is not sufficient to characterize the dominant variability. NAO, though relevant, has an effect smaller than EA and comparable to other patterns. Some link results from possibly spurious structures. Patterns which have a very different global structure are associated to similar spatial features of the wave variability in the Mediterranean Sea. These two problems are, admittedly, shortcomings of this analysis, which shows the complexity of the response of the Mediterranean SWH to global scale SLP teleconnection patterns.

  6. Tapping of Love waves in an isotropic surface waveguide by surface-to-bulk wave transduction.

    Science.gov (United States)

    Tuan, H.-S.; Chang, C.-P.

    1972-01-01

    A theoretical study of tapping a Love wave in an isotropic microacoustic surface waveguide is given. The surface Love wave is tapped by partial transduction into a bulk wave at a discontinuity. It is shown that, by careful design of the discontinuity, the converted bulk wave power and the radiation pattern may be controlled. General formulas are derived for the calculation of these important characteristics from a relatively general surface contour deformation.

  7. An idealised experimental model of ocean surface wave transmission by an ice floe

    CERN Document Server

    Bennetts, Luke; Meylan, Michael; Cavaliere, Claudio; Babanin, Alexander; Toffoli, Alessandro

    2015-01-01

    An experimental model of transmission of ocean waves by an ice floe is presented. Thin plastic plates with different material properties and thicknesses are used to model the floe. Regular incident waves with different periods and steepnesses are used, ranging from gently-sloping to storm-like conditions. A wave gauge is used to measure the water surface elevation in the lee of the floe. The depth of wave overwash on the floe is measured by a gauge in the centre of the floe's upper surface. Results show transmitted waves are regular for gently-sloping incident waves but irregular for storm-like incident waves. The proportion of the incident wave transmitted is shown to decrease as incident wave steepness increases, and to be at its minimum for an incident wavelength equal to the floe length. Further, a trend is noted for transmission to decrease as the mean wave height in the overwash region increases.

  8. Superdirected Beam of the Surface Spin Wave

    CERN Document Server

    Annenkov, Alexander Yu; Lock, Edwin H

    2016-01-01

    Visualized diffraction patterns of the surface spin wave excited by arbitrarily oriented linear transducer in tangentially magnetized ferrite film are investigated experimentally in the plane of ferrite film for the case where the transducer length D is much larger than the wavelength L. Superdirected (nonexpanding) beam of the surface spin wave with noncollinear wave vector k and group velocity vector V was observed experimentally: the angular width of this beam was about zero, the smearing of the beam energy along the film plane was minimal and the length of the beam trajectory was maximal (50 mm). Thus it was shown that such phenomenon as superdirected propagation of the wave exists in the nature.

  9. Performance of a data-driven technique to changes in wave height and its effect on beach response

    Directory of Open Access Journals (Sweden)

    Jose M. Horrillo-Caraballo

    2016-01-01

    Full Text Available In this study the medium-term response of beach profiles was investigated at two sites: a gently sloping sandy beach and a steeper mixed sand and gravel beach. The former is the Duck site in North Carolina, on the east coast of the USA, which is exposed to Atlantic Ocean swells and storm waves, and the latter is the Milford-on-Sea site at Christchurch Bay, on the south coast of England, which is partially sheltered from Atlantic swells but has a directionally bimodal wave exposure. The data sets comprise detailed bathymetric surveys of beach profiles covering a period of more than 25 years for the Duck site and over 18 years for the Milford-on-Sea site. The structure of the data sets and the data-driven methods are described. Canonical correlation analysis (CCA was used to find linkages between the wave characteristics and beach profiles. The sensitivity of the linkages was investigated by deploying a wave height threshold to filter out the smaller waves incrementally. The results of the analysis indicate that, for the gently sloping sandy beach, waves of all heights are important to the morphological response. For the mixed sand and gravel beach, filtering the smaller waves improves the statistical fit and it suggests that low-height waves do not play a primary role in the medium-term morphological response, which is primarily driven by the intermittent larger storm waves.

  10. Backward Surface Wave Propagation and Radiation along a One-Dimensional Folded Cylindrical Helix Array

    Directory of Open Access Journals (Sweden)

    Bin Xu

    2015-01-01

    Full Text Available Wave propagation along a closely spaced folded cylindrical helix (FCH array is investigated for the purpose of designing compact array for energy transport and antenna radiation. It is found that the height of this surface wave guiding structure can be decreased from 0.24λ0 to 0.06λ0 by replacing the monopole element with the FCH. Both the propagation constant and the mode distribution of the dominant wave mechanism are extracted by ESPRIT algorithm, which indicates that a backward propagating surface wave is supported by the array structure. A compact backfire FCH antenna array is designed and measured based on the identified dominant wave mechanism.

  11. Estimates of ocean wave heights and attenuation in sea ice using the SAR wave mode on Sentinel-1A

    Science.gov (United States)

    Ardhuin, Fabrice; Collard, Fabrice; Chapron, Bertrand; Girard-Ardhuin, Fanny; Guitton, Gilles; Mouche, Alexis; Stopa, Justin E.

    2015-04-01

    Swell evolution from the open ocean into sea ice is poorly understood, in particular the amplitude attenuation expected from scattering and dissipation. New synthetic aperture radar (SAR) data from Sentinel-1A wave mode reveal intriguing patterns of bright oscillating lines shaped like instant noodles. We investigate cases in which the oscillations are in the azimuth direction, around a straight line in the range direction. This observation is interpreted as the distortion by the SAR processing of crests from a first swell, due to the presence of a second swell. Since deviations from a straight line should be proportional to the orbital velocity toward the satellite, swell height can be estimated, from 1.5 to 5 m in the present case. The evolution of this 13 s period swell across the ice pack is consistent with an exponential attenuation on a length scale of 200 km.

  12. Nonlinear surface waves in photonic hypercrystals

    Science.gov (United States)

    Ali, Munazza Zulfiqar

    2017-08-01

    Photonic crystals and hyperbolic metamaterials are merged to give the concept of photonic hypercrystals. It combines the properties of its two constituents to give rise to novel phenomena. Here the propagation of Transverse Magnetic waves at the interface between a nonlinear dielectric material and a photonic hypercrystal is studied and the corresponding dispersion relation is derived using the uniaxial parallel approximation. Both dielectric and metallic photonic hypercrystals are studied and it is found that nonlinearity limits the infinite divergence of wave vectors of the surface waves. These states exist in the frequency region where the linear surface waves do not exist. It is also shown that the nonlinearity can be used to engineer the group velocity of the resulting surface wave.

  13. Interplay between surface and surface resonance states on height selective stability of fcc Dy(111) film at nanoscale.

    Science.gov (United States)

    Liu, Xiaojie; Wang, Cai-Zhuang; Hupalo, Myron; Ho, Kai-Ming; Thiel, Patricia A; Tringides, Michael C

    2016-11-16

    Using first-principles calculations we show that face-centered cubic Dy(111) ultrathin films exhibit height selective stability. The origin of such height selection can be attributed to the interplay between the localized surface states and surface resonance states due to electron confinement effects. Such effect could be utilized to manipulate the film thickness at the atomic level to achieve desirable film properties or to control the growth of nanostructures on the thin film for various applications.

  14. Interannual variability and future projection of summertime ocean wave heights in the western North Pacific

    Directory of Open Access Journals (Sweden)

    W. Sasaki

    2006-10-01

    Full Text Available A 70-yr (from 1985–1995 to 2055–2065 change of decadal mean summertime extreme significant wave heights (SWH in the western North Pacific under CO2-induced global warming condition is projected. For this purpose, possible atmospheric fields under future global warming are derived from 10-yr time-slice experiments using a T106 AGCM. The future changes of SWH are assessed by an empirical approach, where possible changes of SWH are estimated using a linear regression model which shows an empirical relationship between SWH anomalies and an eastward shift of the monsoon trough. It is projected that SWH increases by up to ~0.4 m over a wide area of the western North Pacific.

  15. Ruts and waves in the road surface.

    NARCIS (Netherlands)

    Tromp, J.P.M.

    1989-01-01

    The characteristics of a road and a road surface should not unexpectedly change, if the traffic process is to be kept safe and under control. Knowledge on accidents, in which ruts and waves played a part does not seem to exist. Knowledge on driver behaviour due to the occurrence of waves or ruts is

  16. River dykes investigation using seismic surface waves

    Science.gov (United States)

    Bitri, Adnand; Jousset, Philippe; Samyn, Kévin; Naylor, Adam

    2010-05-01

    Natural underground caves such as karsts are quite common in the region "Centre", France. These subsurface perturbations can be found underneath the protection dykes around "the Loire" River and the damage caused can create routes for floods. Geophysical methods such as Multi-channel Analysis of Surface Waves (MASW) can be used for locating voids or karsts systems, but its efficiency on surface with strong topography such as dykes is not certain. Three dimensional Rayleigh wave modelling was used to understand the role of topography in the propagation of surface waves and with the aim of determining the best way for MASW investigations of surfaces with strong topography such as river dykes. Numerical modelling shows that surface waves propagation is not strongly affected by topography for an array parallel to the dyke. For homogeneous models with topography, a diminution of surface waves amplitude is observed while higher propagation modes are amplified in the dispersion curves in the case of heterogeneous models with topography. For an array perpendicular to the dyke, numerical modeling shows that Rayleigh waves' velocity is lower. MASW investigations can then be applied if lateral variations of the topography are not too strong along the seismic line. Diffraction hyperbolas created by a full of water cavity were identified in numerical modelling with topography. According to these elements, a MASW survey has been performed on the dykes of "the Loire" river close to a collapsed cavity and potential karstic systems were discovered.

  17. Photonics surface waves on metamaterials interfaces.

    Science.gov (United States)

    Takayama, Osamu; Bogdanov, Andrey; Lavrinenko, Andrei V

    2017-09-12

    A surface wave (SW) in optics is a light wave, which is supported at an interface of two dissimilar media and propagates along the interface with its field amplitude exponentially decaying away from the boundary. The research on surface waves has been flourishing in last few decades thanks to their unique properties of surface sensitivity and field localization. These features have resulted in applications in nano-guiding, sensing, light-trapping and imaging based on the near-field techniques, contributing to the establishment of the nanophotonics as a field of research. Up to present, a wide variety of surface waves has been investigated in numerous material and structure settings. This paper reviews the recent progress and development in the physics of SWs localized at metamaterial interfaces, as well as bulk media in order to provide broader perspectives on optical surface waves in general. For each type of the surface waves, we discuss material and structural platforms. We mainly focus on experimental realizations in the visible and near-infrared wavelength ranges. We also address existing and potential application of SWs in chemical and biological sensing, and experimental excitation and characterization methods. © 2017 IOP Publishing Ltd.

  18. Surface waves of Min-proteins

    Science.gov (United States)

    Fischer-Friedrich, Elisabeth; Nguyen van yen, Romain; Kruse, Karsten

    2007-03-01

    In the bacterium Escherichia coli, the Min-proteins show pronounced pole-to-pole oscillations. They are functional for suppressing cell division at the cell ends, leaving the center as the only possible site for division. Analyzing different models of Min-protein dynamics in a bacterial geometry, we find waves on the cytoplasmic membrane. Interestingly, the surface wave solutions of different models belong to different symmetry classes. We suggest that experiments on Min-protein surface waves in vitro are helpful in distinguishing between different classes of models of Min-protein dynamics.

  19. Wave-scattering from a gently curved surface

    CERN Document Server

    Bimonte, Giuseppe

    2016-01-01

    We study wave scattering from a gently curved surface. We show that the recursive relations, implied by shift invariance, among the coefficients of the perturbative series for the scattering amplitude allow to perform an infinite resummation of the perturbative series to all orders in the amplitude of the corrugation. The resummed series provides a derivative expansion of the scattering amplitude in powers of derivatives of the height profile, which is expected to become exact in the limit of quasi-specular scattering. We discuss the relation of our results with the so-called small-slope approximation introduced some time ago by Voronovich.

  20. Structure of the airflow above surface waves

    Science.gov (United States)

    Buckley, Marc; Veron, Fabrice

    2016-04-01

    Weather, climate and upper ocean patterns are controlled by the exchanges of momentum, heat, mass, and energy across the ocean surface. These fluxes are, in turn, influenced by the small-scale physics at the wavy air-sea interface. We present laboratory measurements of the fine-scale airflow structure above waves, achieved in over 15 different wind-wave conditions, with wave ages Cp/u* ranging from 1.4 to 66.7 (where Cp is the peak phase speed of the waves, and u* the air friction velocity). The experiments were performed in the large (42-m long) wind-wave-current tank at University of Delaware's Air-Sea Interaction laboratory (USA). A combined Particle Image Velocimetry and Laser Induced Fluorescence system was specifically developed for this study, and provided two-dimensional airflow velocity measurement as low as 100 um above the air-water interface. Starting at very low wind speeds (U10~2m/s), we directly observe coherent turbulent structures within the buffer and logarithmic layers of the airflow above the air-water interface, whereby low horizontal velocity air is ejected away from the surface, and higher velocity fluid is swept downward. Wave phase coherent quadrant analysis shows that such turbulent momentum flux events are wave-phase dependent. Airflow separation events are directly observed over young wind waves (Cp/u*wind waves (Cp/u*=3.7). Over slightly older wind waves (Cp/u* = 6.5), the measured wave-induced airflow perturbations are qualitatively consistent with linear critical layer theory.

  1. Bidirectional surface wave splitter at visible frequencies.

    Science.gov (United States)

    Gan, Qiaoqiang; Bartoli, Filbert J

    2010-12-15

    We experimentally demonstrate a metal-film bidirectional surface wave splitter for guiding light at two visible wavelengths in opposite directions. Two nanoscale gratings were patterned on opposite sides of a subwavelength slit. The metallic surface grating structures were tailored geometrically to have different plasmonic bandgaps, enabling each grating to guide light of one wavelength and prohibit propagation at the other wavelength. The locations of the bandgaps were experimentally confirmed by interferometric measurements. Based on these design principles, a green-red bidirectional surface wave splitter is demonstrated, and the observed optical properties are shown to agree with theoretical predictions.

  2. Jason-2 Validation Test Report (VTR): Validation of Sea Surface Height Anomaly Precision and Accuracy for Mesoscale Applications

    Science.gov (United States)

    2010-05-07

    SSH ) is of importance. If G is the geoid height above the reference then ( )SSH O R A G (2) Often the geoid height is unknown or contains...The sea surface height anomaly ( SSHA ) is ( )SSHA SSH MDH SL G MDH (3) where MDH is the mean dynamic height or height above the geoid due to...knowledge of the geoid (G) provides the sea surface height (SSH). 4 6378136.3 m and a flattening of 1/298.257. The satellite position

  3. Effects of Pentacam on the posterior corneal surface height changes after LASEK and LASIK operation

    Directory of Open Access Journals (Sweden)

    Qing-Song Zhang

    2014-05-01

    Full Text Available AIM: To explore the application of Pentacam excimer laser epithelial keratomileusis(LASEKand excimer laser in situ keratomileusis(LASIKafter the changes of posterior corneal surface height.METHODS: Retrospective analysis of clinical data of 100 patients with myopia by using LASEK and LASIK for the treatment of the 50 patients(100 eyesin our hospital from January 2013 to June 2013, surface height changes after preoperative and postoperative 3 months were compared by measuring Pentacam corneal analysis system.RESULTS: Three months after operation, the LASEK posterior corneal surface height was 7.4±5.0mm, significantly higher than 5.6±3.4mm before operation, LASIK posterior corneal surface height was 7.5±5.1mm, significantly higher than 5.5±3.5mm before operation, the differences were statistically significant(PP>0.05.CONCLUSION: LASEK and LASIK on corneal posterior surface forward, LASIK is slightly obvious in early period.

  4. Automated detection and association of surface waves

    Directory of Open Access Journals (Sweden)

    C. R. D. Woodgold

    1994-06-01

    Full Text Available An algorithm for the automatic detection and association of surface waves has been developed and tested over an 18 month interval on broad band data from the Yellowknife array (YKA. The detection algorithm uses a conventional STA/LTA scheme on data that have been narrow band filtered at 20 s periods and a test is then applied to identify dispersion. An average of 9 surface waves are detected daily using this technique. Beamforming is applied to determine the arrival azimuth; at a nonarray station this could be provided by poIarization analysis. The detected surface waves are associated daily with the events located by the short period array at Yellowknife, and later with the events listed in the USGS NEIC Monthly Summaries. Association requires matching both arrival time and azimuth of the Rayleigh waves. Regional calibration of group velocity and azimuth is required. . Large variations in both group velocity and azimuth corrections were found, as an example, signals from events in Fiji Tonga arrive with apparent group velocities of 2.9 3.5 krn/s and azimuths from 5 to + 40 degrees clockwise from true (great circle azimuth, whereas signals from Kuriles Kamchatka have velocities of 2.4 2.9 km/s and azimuths off by 35 to 0 degrees. After applying the regional corrections, surface waves are considered associated if the arrival time matches to within 0.25 km/s in apparent group velocity and the azimuth is within 30 degrees of the median expected. Over the 18 month period studied, 32% of the automatically detected surface waves were associated with events located by the Yellowknife short period array, and 34% (1591 with NEIC events; there is about 70% overlap between the two sets of events. Had the automatic detections been reported to the USGS, YKA would have ranked second (after LZH in terms of numbers of associated surface waves for the study period of April 1991 to September 1992.

  5. Surface acoustic wave mode conversion resonator

    Science.gov (United States)

    Martin, S. J.; Gunshor, R. L.; Melloch, M. R.; Datta, S.; Pierret, R. F.

    1983-08-01

    The fact that a ZnO-on-Si structure supports two distinct surface waves, referred to as the Rayleigh and the Sezawa modes, if the ZnO layer is sufficiently thick is recalled. A description is given of a unique surface wave resonator that operates by efficiently converting between the two modes at the resonant frequency. Since input and output coupling is effected through different modes, the mode conversion resonator promises enhanced out-of-band signal rejection. A Rayleigh wave traversing the resonant cavity in one direction is reflected as a Sezawa wave. It is pointed out that the off-resonance rejection of the mode conversion resonator could be enhanced by designing the transducers to minimize the level of cross coupling between transducers and propagating modes.

  6. On the Simulation of Sea States with High Significant Wave Height for the Validation of Parameter Retrieval Algorithms for Future Altimetry Missions

    Science.gov (United States)

    Kuschenerus, Mieke; Cullen, Robert

    2016-08-01

    To ensure reliability and precision of wave height estimates for future satellite altimetry missions such as Sentinel 6, reliable parameter retrieval algorithms that can extract significant wave heights up to 20 m have to be established. The retrieved parameters, i.e. the retrieval methods need to be validated extensively on a wide range of possible significant wave heights. Although current missions require wave height retrievals up to 20 m, there is little evidence of systematic validation of parameter retrieval methods for sea states with wave heights above 10 m. This paper provides a definition of a set of simulated sea states with significant wave height up to 20 m, that allow simulation of radar altimeter response echoes for extreme sea states in SAR and low resolution mode. The simulated radar responses are used to derive significant wave height estimates, which can be compared with the initial models, allowing precision estimations of the applied parameter retrieval methods. Thus we establish a validation method for significant wave height retrieval for sea states causing high significant wave heights, to allow improved understanding and planning of future satellite altimetry mission validation.

  7. Photonic crystal surface waves for optical biosensors.

    Science.gov (United States)

    Konopsky, Valery N; Alieva, Elena V

    2007-06-15

    We present a new optical biosensor technique based on registration of dual optical s-polarized modes on a photonic crystal surface. The simultaneous registration of two optical surface waves with different evanescent depths from the same surface spot permits the segregation of the volume and the surface contributions from an analyte, while the absence of metal damping permits an increase in the propagation length of the optical surface waves and the sensitivity of the biosensor. Our technique was tested with the binding of biotin molecules to a streptavidin monolayer that has been detected with signal/noise ratio of approximately 15 at 1-s signal accumulation time. The detection limit is approximately 20 fg of the analyte on the probed spot of the surface.

  8. The validation of HY-2 altimeter measurements of a significant wave height based on buoy data

    Institute of Scientific and Technical Information of China (English)

    WANG Jichao; ZHANG Jie; YANG Jungang

    2013-01-01

    HY-2 has been launched by China on August 16, 2011 which assembles multi-microwave remote sensing payloads in a body and has the ability of monitoring ocean dynamic environments. The HY-2 satellite data need to be calibrated and validated before being put into use. Based on the in-situ buoys from the Nation-al Data Buoy Center (NDBC), Ku-band significant wave heights (SWH, hs) of HY-2 altimeter are validated. Eleven months of HY-2 altimeter Level 2 products data are chose from October 1, 2011 to August 29, 2012. Using NDBC 60 buoys yield 902 collocations for HY-2 by adopting collocation criteria of 30 min for tempo-ral window and 50 km for a spatial window. An overall RMS difference of the SWH between HY-2 and buoy data is 0.297 m. A correlation coefficient between these is 0.964. An ordinary least squares (OLS) regression is performed with the buoy data as an independent variable and the altimeter data as a dependent vari-able. The regression equation of hs is hs(HY-2)=0.891×hs(NDBC)+0.022. In addition, 2016 collocations are matched with temporal window of 30 min at the crossing points of HY-2 and Jason-2 orbits. RMS difference of Ku-band SWH between the two data sets is 0.452 m.

  9. Estimating fog-top height through near-surface micrometeorological measurements

    NARCIS (Netherlands)

    Román-Cascón, Carlos; Yagüe, Carlos; Steeneveld, Gert Jan; Sastre, Mariano; Arrillaga, Jon Ander; Maqueda, Gregorio

    2016-01-01

    Fog-top height (fog thickness) is very useful information for aircraft maneuvers, data assimilation/validation of Numerical Weather Prediction models or nowcasting of fog dissipation. This variable is usually difficult to determine, since the fog-layer top cannot be observed from the surface. In

  10. Multimodel simulations of Arctic Ocean sea surface height variability in the period 1970-2009

    DEFF Research Database (Denmark)

    Koldunov, Nikolay V.; Serra, Nuno; Koehl, Armin

    2014-01-01

    The performance of several numerical ocean models is assessed with respect to their simulation of sea surface height (SSH) in the Arctic Ocean, and the main patterns of SSH variability and their causes over the past 40 years (1970-2009) are analyzed. In comparison to observations, all tested mode...

  11. Blackfolds, plane waves and minimal surfaces

    OpenAIRE

    Armas, Jay; Blau, Matthias

    2015-01-01

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and comp...

  12. Influence of Surface Topography on ICESat/GLAS Forest Height Estimation and Waveform Shape

    Directory of Open Access Journals (Sweden)

    Claudia Hilbert

    2012-07-01

    Full Text Available This study explores ICESat/GLAS waveform data in Thuringian Forest, a low mountain range located in central Germany. Lidar remote sensing has been proven to directly derive tree height as a key variable of forest structure. The GLAS signal is, however, very sensitive to surface topography because of the large footprint size. This study therefore focuses on forests in a mountainous area to assess the potential of GLAS data to derive terrain elevation and tree height. The work enhances the empirical knowledge about the interaction between GLAS waveform and landscape structure regarding a special temperate forest site with a complex terrain. An algorithm to retrieve tree height directly from GLA01 waveform data is proposed and compared to an approach using GLA14 Gaussian parameters. The results revealed that GLAS height estimates were accurate for areas with a slope up to 10° whereas waveforms of areas above 15° were problematic. Slopes between 10–15° have been found to be a critical crossover. Further, different waveform shape types and landscape structure classes were developed as a new possibility to explore the waveform in its whole structure. Based on the detailed analysis of some waveform examples, it could be demonstrated that the waveform shape can be regarded as a product of the complex interaction between surface and canopy structure. Consequently, there is a great variety of waveform shapes which in turn considerably hampers GLAS tree height extraction in areas with steep slopes and complex forest conditions.

  13. Self-similarity Based Editing of 3D Surface Textures Using Height and Albedo Maps

    Institute of Scientific and Technical Information of China (English)

    DONG Junyu; REN Jing; CHEN Guojiang

    2007-01-01

    This paper presents an inexpensive method for self-similarity based editing of real-world 3D surface textures by using height and albedo maps. Unlike self-similarity based 2D texture editing approaches which only make changes to pixel color or intensity values, this technique also allows surface geometry and reflectance of the captured 3D surface textures to be edited and relit using illumination conditions and viewing angles that differ from those of the original. A single editing operation at a given location affects all similar areas and produces changes on all images of the sample rendered under different conditions. Since surface height and albedo maps can be used to describe seabed topography and geologic features, which play important roles in many oceanic processes, the proposed method can be effectively employed in applications regarding visualization and simulation of oceanic phenomena.

  14. Surface tension effects in breaking wave noise.

    Science.gov (United States)

    Deane, Grant B

    2012-08-01

    The role of surface active materials in the sea surface microlayer on the production of underwater noise by breaking waves is considered. Wave noise is assumed to be generated by bubbles formed within actively breaking whitecaps, driven into breathing mode oscillation at the moment of their formation by non-equilibrium, surface tension forces. Two significant effects associated with surface tension are identified-a reduction in low frequency noise (bubbles by fluid turbulence within the whitecap and a reduction in overall noise level due to a decrease in the excitation amplitude of bubbles associated with reduced surface tension. The impact of the latter effect on the accuracy of Weather Observations Through Ambient Noise estimates of wind speed is assessed and generally found to be less than ±1 m s(-1) for wind speeds less than 10 m s(-1) and typical values of surfactant film pressure within sea slicks.

  15. Decadal variations in wave heights off Cape Kelba, Saaremaa Island, and their relationships with changes in wind climate

    Directory of Open Access Journals (Sweden)

    Ülo Suursaar

    2009-03-01

    Full Text Available Based on wind data from the Vilsandi meteorological station and a 5-month calibration measurement with a bottom-mounted Recording Doppler Current Profiler (RDCP, a semi-empirical hindcast of wave parameters near the quickly developing accumulative Kelba Spit is presented for the period 1966-2006. The significant wave heights with a gross mean value of 0.56 m exhibited some quasiperiodic cycles, with the last high stage in 1980-95 and a decreasing overall trend of $-0.001$ m per year. At the same time, both the frequency and intensity of high wave events showed rising trends, and the mean wave heights during winter (December to February increased as well. As the study area has the longest fetches in westerly directions, the discussed tendencies in wave conditions are sensitive to regional changes in the wind climate and can be related to a decrease in the local average wind speed on the one hand, but an intensification of westerly winds, storm events and the wintertime NAO index on the other. The roughest wave storms on record were associated with prominent W-storms on 2 November 1969 and 9 January 2005; a few other extreme wind events (e.g. in 1967, 1999, 2001, however, did not yield equally prominent waves.

  16. Observation of strongly non-Gaussian statistics for random sea surface gravity waves in wave flume experiments.

    Science.gov (United States)

    Onorato, M; Osborne, A R; Serio, M; Cavaleri, L; Brandini, C; Stansberg, C T

    2004-12-01

    We study random surface gravity wave fields and address the formation of large-amplitude waves in a laboratory environment. Experiments are performed in one of the largest wave tank facilities in the world. We present experimental evidence that the tail of the probability density function for wave height strongly depends on the Benjamin-Feir index (BFI)-i.e., the ratio between wave steepness and spectral bandwidth. While for a small BFI the probability density functions obtained experimentally are consistent with the Rayleigh distribution, for a large BFI the Rayleigh distribution clearly underestimates the probability of large events. These results confirm experimentally the fact that large-amplitude waves in random spectra may result from the modulational instability.

  17. An MCV Nonhydrostatic Atmospheric Model with Height-Based Terrain following Coordinate: Tests of Waves over Steep Mountains

    Directory of Open Access Journals (Sweden)

    Xingliang Li

    2016-01-01

    Full Text Available A nonhydrostatic atmospheric model was tested with the mountain waves over various bell-shaped mountains. The model is recently proposed by using the MCV (multimoment constrained finite volume schemes with the height-based terrain following coordinate representing the topography. As discussed in our previous work, the model has some appealing features for atmospheric modeling and can be expected as a practical framework of the dynamic cores, which well balances the numerical accuracy and algorithmic complexity. The flows over the mountains of various half widths and heights were simulated with the model. The semianalytic solutions to the mountain waves through the linear theory are used to check the performance of the MCV model. It is revealed that the present model can accurately reproduce various mountain waves including those generated by the mountains with very steep inclination and is very promising for numerically simulating atmospheric flows over complex terrains.

  18. Large scale spatio-temporal behaviour in surface growth. Scaling and dynamics of slow height variations in generalized two-dimensional Kuramoto-Sivashinsky equations

    Science.gov (United States)

    Juknevičius, Vaidas; Ruseckas, Julius; Armaitis, Jogundas

    2017-09-01

    This paper presents new findings concerning the dynamics of the slow height variations in surfaces produced by the two-dimensional isotropic Kuramoto-Sivashinsky equation with an additional nonlinear term. In addition to the disordered cellular patterns of specific size evident at small scales, slow height variations of scale-free character become increasingly evident when the system size is increased. This paper focuses on the parameter range in which the kinetic roughening with eventual saturation in surface roughness and coarseness is obtained, and the statistical and dynamical properties of surfaces in the long-time stationary regime are investigated. The resulting long-range scaling properties of the saturated surface roughness consistent with the power-law shape of the surface spectrum at small wave numbers are obtained in a wider parameter range than previously reported. The temporal properties of these long-range height variations are investigated by analysing the time series of surface roughness fluctuations. The resulting power-spectral densities can be expressed as a generalized Lorentzian whose cut-off frequency varies with system size. The dependence of this lower cut-off frequency on the smallest wave number connects spatial and temporal properties and gives new insight into the surface evolution on large scales.

  19. Viscoelastic love-type surface waves

    Science.gov (United States)

    Borcherdt, Roger D.

    2008-01-01

    The general theoretical solution for Love-Type surface waves in viscoelastic media provides theoreticalexpressions for the physical characteristics of the waves in elastic as well as anelastic media with arbitraryamounts of intrinsic damping. The general solution yields dispersion and absorption-coefficient curves for the waves as a function of frequency and theamount of intrinsic damping for any chosen viscoelastic model.Numerical results valid for a variety of viscoelastic models provide quantitative estimates of the physicalcharacteristics of the waves pertinent to models of Earth materials ranging from small amounts of damping in the Earth’s crust to moderate and large amounts of damping in soft soils and water-saturated sediments. Numerical results, presented herein, are valid for a wide range of solids and applications.

  20. Height estimate for special Weingarten surfaces of elliptic type in ${\\mathbb M}^2(c \\times \\mathbb {R}$

    Directory of Open Access Journals (Sweden)

    Filippo Morabito

    2014-01-01

    Full Text Available In this article we provide a vertical height estimate for compact special Weingarten surfaces of elliptic type in ²(×ℝ, i.e. surfaces whose mean curvature ℍ and extrinsic Gauss curvature ₑ satisfy ℍ=(ℍ²-ₑ with 4(’(²<1, for all ∈[0,+∞. The vertical height estimate generalizes a result by Rosenberg and Sa Earp and applies only to surfaces verifying a height estimate condition. When <0, using also a horizontal height estimate, we show a non-existence result for properly embedded Weingarten surfaces of elliptic type in ℍ²(×ℝ with finite topology and one end.

  1. Sea surface height determination in the arctic ocean from Cryosat2 SAR data, the impact of using different empirical retrackers

    DEFF Research Database (Denmark)

    Jain, Maulik; Andersen, Ole Baltazar; Stenseng, Lars

    2012-01-01

    Cryosat2 Level 1B SAR data can be processed using different empirical retrackers to determine the sea surface height and its variations in the Arctic Ocean. Two improved retrackers based on the combination of OCOG (Offset Centre of Gravity), Threshold methods and Leading Edge Retrieval is used...... to estimate the sea surface height in the Arctic Region. This sea surface height determination is to be compared with the Level2 sea surface height components available in the Cryosat2 data. Further a comparison is done with the marine gravity field for retracker performance evaluation....

  2. Chiral Surface Waves for Enhanced Circular Dichroism

    CERN Document Server

    Pellegrini, Giovanni; Celebrano, Michele; Duò, Lamberto; Biagioni, Paolo

    2016-01-01

    We present a novel chiral sensing platform that combines a one-dimensional photonic crystal design with a birefringent surface defect. The platform sustains simultaneous transverse electric and transverse magnetic surface modes, which are exploited to generate chiral surface waves. The present design provides homogeneous and superchiral fields of both handednesses over arbitrarily large areas in a wide spectral range, resulting in the enhancement of the circular dichroism signal by two orders of magnitude, thus paving the road toward the successful combination of surface-enhanced spectroscopies and electromagnetic superchirality.

  3. Surface acoustic wave propagation in graphene film

    Energy Technology Data Exchange (ETDEWEB)

    Roshchupkin, Dmitry, E-mail: rochtch@iptm.ru; Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Irzhak, Dmitry [Institute of Microelectronics Technology and High-Purity Materials Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Ortega, Luc [Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS, UMR 8502, 91405 Orsay Cedex (France); Zizak, Ivo; Erko, Alexei [Institute for Nanometre Optics and Technology, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein Strasse 15, 12489 Berlin (Germany); Tynyshtykbayev, Kurbangali; Insepov, Zinetula [Nazarbayev University Research and Innovation System, 53 Kabanbay Batyr St., Astana 010000 (Kazakhstan)

    2015-09-14

    Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals.

  4. Chiral surface waves for enhanced circular dichroism

    Science.gov (United States)

    Pellegrini, Giovanni; Finazzi, Marco; Celebrano, Michele; Duò, Lamberto; Biagioni, Paolo

    2017-06-01

    We present a novel chiral sensing platform that combines a one-dimensional photonic crystal design with a birefringent surface defect. The platform sustains simultaneous transverse electric and transverse magnetic surface modes, which are exploited to generate chiral surface waves. The present design provides homogeneous and superchiral fields of both handednesses over arbitrarily large areas in a wide spectral range, resulting in the enhancement of the circular dichroism signal by more than two orders of magnitude, thus paving the road toward the successful combination of surface-enhanced spectroscopies and electromagnetic superchirality.

  5. Surface acoustic wave propagation in graphene film

    Science.gov (United States)

    Roshchupkin, Dmitry; Ortega, Luc; Zizak, Ivo; Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Erko, Alexei; Tynyshtykbayev, Kurbangali; Irzhak, Dmitry; Insepov, Zinetula

    2015-09-01

    Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals.

  6. Gas sensing with surface acoustic wave devices

    Science.gov (United States)

    Martin, S. J.; Schweizer, K. S.; Ricco, A. J.; Zipperian, T. E.

    1985-03-01

    The use of a ZnO-on-Si surface acoustic wave (SAW) resonator as a gas sensor is discussed. In particular, the sensitivity of the device to organic vapors is examined. The planar nature of the SAW device, in which the acoustic energy is confined to within roughly one acoustic wavelength of the surface, makes the device extremely sensitive to surface perturbations. This characteristic has been exploited in the construction of SAW gas sensors in which the surface wave propagation characteristics are altered by species adsorbed from the ambient gas. The porous nature of the sputtered ZnO film, in conjunction with the microbalance capability of the SAW device, gives the sensor the ability to distinguish molecules on the basis of both size and mass.

  7. Active micromixer using surface acoustic wave streaming

    Science.gov (United States)

    Branch; Darren W. , Meyer; Grant D. , Craighead; Harold G.

    2011-05-17

    An active micromixer uses a surface acoustic wave, preferably a Rayleigh wave, propagating on a piezoelectric substrate to induce acoustic streaming in a fluid in a microfluidic channel. The surface acoustic wave can be generated by applying an RF excitation signal to at least one interdigital transducer on the piezoelectric substrate. The active micromixer can rapidly mix quiescent fluids or laminar streams in low Reynolds number flows. The active micromixer has no moving parts (other than the SAW transducer) and is, therefore, more reliable, less damaging to sensitive fluids, and less susceptible to fouling and channel clogging than other types of active and passive micromixers. The active micromixer is adaptable to a wide range of geometries, can be easily fabricated, and can be integrated in a microfluidic system, reducing dead volume. Finally, the active micromixer has on-demand on/off mixing capability and can be operated at low power.

  8. Surface waves on metal-dielectric metamaterials

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee;

    2016-01-01

    In this paper we analyze surface electromagnetic waves supported at an interface between an isotropic medium and an effective anisotropic material that can be realized by alternating conductive and dielectric layers with deep subwavelength thicknesses. This configuration can host various types of...

  9. Some Applications of Surface Acoustic Wave Sensors

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The paper describes the evaluation of thin amorphous magnetic film by using of surface acoustic waves on piezo electric substrate. The obtained experimental data show strong dependence of material parameters on the annealing temperature. The mixed ferromagnetic/SAW devices for electronic applications will be also discussed.

  10. Determining surface wave arrival angle anomalies

    Science.gov (United States)

    Larson, Erik W. F.; Ekström, Göran

    2002-06-01

    A new method for measuring arrival angles of teleseismic Love and Rayleigh waves is developed. The new method utilizes estimates of surface wave dispersion to create a phase-matched filter to isolate the Love or Rayleigh wave in three-component recordings. The polarization of the filtered wave group is determined in the time domain by application of a variation of the complex polarization method of Vidale [1986]. Orientation, linearity, and ellipticity of particle motion are estimated in several frequency bands to determine the frequency-dependent polarization. The method employs an iterative scheme, by which a predicted Love wave, based on the estimated dispersion and polarization, is subtracted from the three-component data prior to the estimation of Rayleigh wave polarization, and vice versa. The method is applied to an extensive set of Global Seismographic Network data covering the years 1989-1998. Between 4244 and 15,075 measurements are collected for fundamental mode Love and Rayleigh waves at nine different periods (37 to 150 s). Measurement uncertainties are estimated using the statistics of observations for pairwise similar paths and are generally of the order of 15-50% of the total signal, depending on the period and the wave type. Large and azimuthally invariant angle anomalies are documented for several stations and are consistent with misorientation of the horizontal seismometers. Two schemes are employed to determine the misorientations: (1) an azimuthally weighted average at each station, and (2) a joint inversion for seismometer misorientation and globally heterogeneous phase velocities. The determined corrections are robust and correlate well with those reported in earlier studies. Azimuthally varying arrival angle anomalies are shown to agree qualitatively with predictions of wave refraction calculated for recent phase velocity maps, which explain up to 30% of the variance in the new measurements.

  11. Surface and Internal Waves due to a Moving Load on a Very Large Floating Structure

    Directory of Open Access Journals (Sweden)

    Taro Kakinuma

    2012-01-01

    Full Text Available Interaction of surface/internal water waves with a floating platform is discussed with nonlinearity of fluid motion and flexibility of oscillating structure. The set of governing equations based on a variational principle is applied to a one- or two-layer fluid interacting with a horizontally very large and elastic thin plate floating on the water surface. Calculation results of surface displacements are compared with the existing experimental data, where a tsunami, in terms of a solitary wave, propagates across one-layer water with a floating thin plate. We also simulate surface and internal waves due to a point load, such as an airplane, moving on a very large floating structure in shallow water. The wave height of the surface or internal mode is amplified when the velocity of moving point load is equal to the surface- or internal-mode celerity, respectively.

  12. Absolute height measurement of specular surfaces with modified active fringe reflection photogrammetry

    Science.gov (United States)

    Ren, Hongyu; Jiang, Xiangqian; Gao, Feng; Zhang, Zonghua

    2014-07-01

    Deflectometric methods have been studied for more than a decade for slope measurement of specular freeform surfaces through utilization of the deformation of a sample pattern after reflection from a tested sample surface. Usually, these approaches require two-directional fringe patterns to be projected on a LCD screen or ground glass and require slope integration, which leads to some complexity for the whole measuring process. This paper proposes a new mathematical measurement model for measuring topography information of freeform specular surfaces, which integrates a virtual reference specular surface into the method of active fringe reflection photogrammetry and presents a straight-forward relation between height of the tested surface and phase signals. This method only requires one direction of horizontal or vertical sinusoidal fringe patterns to be projected from a LCD screen, resulting in a significant reduction in capture time over established methods. Assuming the whole system has been precalibrated during the measurement process, the fringe patterns are captured separately via the virtual reference and detected freeform surfaces by a CCD camera. The reference phase can be solved according to the spatial geometric relation between the LCD screen and the CCD camera. The captured phases can be unwrapped with a heterodyne technique and optimum frequency selection method. Based on this calculated unwrapped-phase and that proposed mathematical model, absolute height of the inspected surface can be computed. Simulated and experimental results show that this methodology can conveniently calculate topography information for freeform and structured specular surfaces without integration and reconstruction processes.

  13. Influence of virtual height exposure on postural reactions to support surface translations.

    Science.gov (United States)

    Cleworth, Taylor W; Chua, Romeo; Inglis, J Timothy; Carpenter, Mark G

    2016-06-01

    As fear of falling is related to the increased likelihood of falls, it is important to understand the effects of threat-related factors (fear, anxiety and confidence) on dynamic postural reactions. Previous studies designed to examine threat effects on dynamic postural reactions have methodological limitations and lack a comprehensive analysis of simultaneous kinetic, kinematic and electromyographical recordings. The current study addressed these limitations by examining postural reactions of 26 healthy young adults to unpredictable anterior-posterior support-surface translations (acceleration=0.6m/s(2), constant velocity=0.25m/s, total displacement=0.75m) while standing on a narrow virtual surface at Low (0.4cm) and High (3.2m) virtual heights. Standing at virtual height increased fear and anxiety, and decreased confidence. Prior to perturbations, threat led to increased tonic muscle activity in tibialis anterior, resulting in a higher co-contraction index between lower leg muscles. For backward perturbations, muscle activity in the lower leg and arm, and center of pressure peak displacements, were earlier and larger when standing at virtual height. In addition, arm flexion significantly increased while leg, trunk and center of mass displacements remained unchanged across heights. When controlling for leaning, threat-related factors can influence the neuro-mechanical responses to an unpredictable perturbation, causing specific characteristics of postural reactions to be facilitated in young adults when their balance is threatened. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Trends of wave height and period in the Central Arabian Sea from 1996 to 2012: A study based on satellite altimeter data

    Digital Repository Service at National Institute of Oceanography (India)

    Hithin, N.K.; SanilKumar, V.; Shanas, P.R.

    : Ocean Eng., Vol.108; 2015; 416-425. Trends of wave height and period in the Central Arabian Sea from 1996 to 2012: A study based on satellite altimeter data N.K. Hithin, V. Sanil Kumar*, P.R. Shanas+ Ocean Engineering Division, CSIR... measures wind speed at 3 m above the sea surface and SWH at a 3-h interval. Wind observation is a 10-minute average with wind speed and direction sampled at 1 Hz by a cup anemometer with vane. The accuracy of wind speed measurements is 1.5% of full scale...

  15. New expressions for the surface roughness length and displacement height in the atmospheric boundary layer

    Institute of Scientific and Technical Information of China (English)

    Lin Jian-Zhong; Li Hui-Jun; Zhang Kai

    2007-01-01

    An alternative model for the prediction of surface roughness length is developed. In the model a new factor is introduced to compensate for the effects of wake diffusion and interactions between the wake and roughness obstacles.The experiments are carried out by the use of the hot wire anemometry in the simulated atmospheric boundary layer in a wind tunnel. Based on the experimental data, a new expression for the zero-plane displacement height is proposed for the square arrays of roughness elements, which highlights the influence of free-stream speed on the roughness length. It appears that the displacement height increases with the wind speed while the surface roughness length decreases with Reynolds number increasing. It is shown that the calculation results based on the new expressions are in reasonable agreement with the experimental data.

  16. Linear and Nonlinear Surface Waves in Electrohydrodynamics

    CERN Document Server

    Hunt, Matthew; Vanden-broeck, Jean-Marc; Papageorgiou, Demetrios

    2015-01-01

    The problem of interest in this article are waves on a layer of finite depth governed by the Euler equations in the presence of gravity, surface tension, and vertical electric fields. Perturbation theory is used to identify canonical scalings and to derive a Kadomtsev-Petviashvili equation withan additional non-local term arising in interfacial electrohydrodynamics.When the Bond number is equal to 1/3, dispersion disappears and shock waves could potentially form. In the additional limit of vanishing electric fields, a new evolution equation is obtained which contains third and fifth-order dispersion as well as a non-local electric field term.

  17. Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014

    Science.gov (United States)

    Armitage, Thomas W. K.; Bacon, Sheldon; Ridout, Andy L.; Thomas, Sam F.; Aksenov, Yevgeny; Wingham, Duncan J.

    2016-06-01

    Arctic sea surface height (SSH) is poorly observed by radar altimeters due to the poor coverage of the polar oceans provided by conventional altimeter missions and because large areas are perpetually covered by sea ice, requiring specialized data processing. We utilize SSH estimates from both the ice-covered and ice-free ocean to present monthly estimates of Arctic Dynamic Ocean Topography (DOT) from radar altimetry south of 81.5°N and combine this with GRACE ocean mass to estimate steric height. Our SSH and steric height estimates show good agreement with tide gauge records and geopotential height derived from Ice-Tethered Profilers. The large seasonal cycle of Arctic SSH (amplitude ˜5 cm) is dominated by seasonal steric height variation associated with seasonal freshwater fluxes, and peaks in October-November. Overall, the annual mean steric height increased by 2.2 ± 1.4 cm between 2003 and 2012 before falling to circa 2003 levels between 2012 and 2014 due to large reductions on the Siberian shelf seas. The total secular change in SSH between 2003 and 2014 is then dominated by a 2.1 ± 0.7 cm increase in ocean mass. We estimate that by 2010, the Beaufort Gyre had accumulated 4600 km3 of freshwater relative to the 2003-2006 mean. Doming of Arctic DOT in the Beaufort Sea is revealed by Empirical Orthogonal Function analysis to be concurrent with regional reductions in the Siberian Arctic. We estimate that the Siberian shelf seas lost ˜180 km3 of freshwater between 2003 and 2014, associated with an increase in annual mean salinity of 0.15 psu yr-1. Finally, ocean storage flux estimates from altimetry agree well with high-resolution model results, demonstrating the potential for altimetry to elucidate the Arctic hydrological cycle.

  18. Remote Observations of the Spatial Variability of Surface Waves Interacting With an Estuarine Outflow

    Science.gov (United States)

    2006-10-01

    He joined Instituto Mexicano del Petroleo (IMP), Mexico , where he partici- terns at the Chesapeake Bay entrance," Cont. ShelfRes., vol. 18, pp...ENGINEERING, VOL. 31, NO. 4, OCTOBER 2006 [21] H. C. Graber and M. L. Heron, "Wave height measurements from HF Rafael J. Ramos was born in Mexico City, Mexico ...Vizinho, and J. Vogelzang, "Moni- neering from Instituto Politecnico Nacional, Mexico toring surface waves in coastal waters by integrating HF radar

  19. On the observability of bottom topography from measurements of tidal sea surface height

    Science.gov (United States)

    Zaron, Edward D.

    2016-06-01

    The question of whether features of the ocean bottom topography can be identified from measurements of water level is investigated using a simplified one-dimensional barotropic model. Because of the nonlinear dependence of the sea surface height on the water depth, a linearized analysis is performed concerning the identification of a Gaussian bump within two specific depth profiles, (1) a constant depth domain, and, (2) a constant depth domain adjoining a near-resonant continental shelf. Observability is quantified by examining the estimation error in a series of identical-twin experiments varying data density, tide wavelength, assumed (versus actual) topographic correlation scale, and friction. For measurements of sea surface height that resolve the scale of the topographic perturbation, the fractional error in the bottom topography is approximately a factor of 10 larger than the fractional error of the sea surface height. Domain-scale and shelf-scale resonances may lead to inaccurate topography estimates due to a reduction in the effective number of degrees of freedom in the dynamics, and the amplification of nonlinearity. A realizability condition for the variance of the topography error in the limit of zero bottom depth is proposed which is interpreted as a bound on the fractional error of the topography. Appropriately designed spatial covariance models partly ameliorate the negative impact of shelf-scale near-resonance, and highlight the importance of spatial covariance modeling for bottom topography estimation.

  20. Blackfolds, plane waves and minimal surfaces

    Science.gov (United States)

    Armas, Jay; Blau, Matthias

    2015-07-01

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.

  1. Temporal and spatial characteristics of sea surface height variability in the North Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    D. Cromwell

    2006-01-01

    Full Text Available We investigate the spatial and temporal variability of sea surface height (SSH in the North Atlantic basin using satellite altimeter data from October 1992–January 2004. Our primary aim is to provide a detailed description of such variability, including that associated with propagating signals. We also investigate possible correlations between SSH variability and atmospheric pressure changes as represented by climate indices. We first investigate interannual SSH variations by deriving the complex empirical orthogonal functions (CEOFs of altimeter data lowpass-filtered at 18 months. We determine the spatial structure of the leading four modes (both in amplitude and phase and also the associated principal component (PC time series. Using wavelet analysis we derive the time-varying spectral density of the PCs, revealing when particular modes were strongest between 1992–2004. The spatial pattern of the leading CEOF, comprising 30% of the total variability, displays a 5-year periodicity in phase; signal propagation is particularly marked in the Labrador Sea. The second mode, with a dominant 3-year signal, has strong variability in the eastern basin. Secondly, we focus on the Azores subtropical frontal zone. The leading mode (35% is strong in the south and east of this region with strong variations at 3- and 5-year periods. The second mode (21% has a near-zonal band of low variance between  22°–27° N, sandwiched between two regions of high variance. Thirdly, we lowpass filter the altimeter data at a cutoff of 30 days, instead of 18 months, in order to retain signals associated with propagating baroclinic Rossby waves and/or eddies. The leading mode is the annual steric signal, around 46% of the SSH variability. The third and fourth CEOFs,  11% of the remaining variability, are associated with westward propagation which is particularly dominant in a "waveband" between 32°–36° N. For all three cases considered above, no significant cross

  2. Droplet evaporation of pure water and protein solution on nanostructured superhydrophobic surfaces of varying heights.

    Science.gov (United States)

    Choi, Chang-Hwan; Kim, Chang-Jin C J

    2009-07-07

    Evaporation of liquids on substrates is important for many applications including lab-on-a-chip, especially when they are in droplets. Unlike on planar substrates, droplet evaporation on micropatterned substrates has been studied only recently and none so far on nanopatterns. Driven by the applicability of nanostructured surfaces to biomaterials and tissue engineering, we report on the evaporative process of sessile droplets of pure water and a protein solution on superhydrophobic surfaces of sharp-tip post structures in a submicrometer pitch (230 nm) and varying heights (100-500 nm). We find that the nanotopographical three-dimensionalities such as structural height and sidewall profile affect the surface superhydrophobicity in such a way that only tall and slender nanostructures provide the surface with great superhydrophobicity (a contact angle more than 170 degrees). The evaporation process was different between the pure water and the protein solution; unlike pure water, a significant contact-line spreading and pinning effect was observed in a droplet of a protein solution with an intermediate transition from a dewetting (Cassie) to a wetting (Wenzel) state. Enabled by well-defined nanostructures, our results highlight that the surface superhydrophobicity and the droplet evaporation are significantly affected by the three-dimensional nanometric topography and the surface fouling such as protein adsorption.

  3. NUMERICAL STUDY ON EFFECT OF WAVING BED ON THE SURFACE WAVE

    Institute of Scientific and Technical Information of China (English)

    WU Zheng-ren; CHENG You-liang; WANG Song-ling

    2006-01-01

    The effect of the waving bed on the surface wave was investigated. The wave equation was reduced from the potential flow theory with the perturbation technique, and then was solved by using the pseudo-spectral method. The waterfall of the surface wave was simulated with the Matlab. It is shown that for the waving bed, an additional harmonic wave appears on the surface together with the solitary wave existing for the non-waving bed, and two kinds of waves do not interfere with each other. With the development of time, the waveform for the waving bed is kept invariable, and just the amplitude is reduced gradually. Wave-breaking phenomenon for the non-waving bed does not appear, so the waving bed seems useful to prevent the breaking of the wave.

  4. Econometric analysis of the changing effects in wind strength and significant wave height on the probability of casualty in shipping.

    Science.gov (United States)

    Knapp, Sabine; Kumar, Shashi; Sakurada, Yuri; Shen, Jiajun

    2011-05-01

    This study uses econometric models to measure the effect of significant wave height and wind strength on the probability of casualty and tests whether these effects changed. While both effects are in particular relevant for stability and strength calculations of vessels, it is also helpful for the development of ship construction standards in general to counteract increased risk resulting from changing oceanographic conditions. The authors analyzed a unique dataset of 3.2 million observations from 20,729 individual vessels in the North Atlantic and Arctic regions gathered during the period 1979-2007. The results show that although there is a seasonal pattern in the probability of casualty especially during the winter months, the effect of wind strength and significant wave height do not follow the same seasonal pattern. Additionally, over time, significant wave height shows an increasing effect in January, March, May and October while wind strength shows a decreasing effect, especially in January, March and May. The models can be used to simulate relationships and help understand the relationships. This is of particular interest to naval architects and ship designers as well as multilateral agencies such as the International Maritime Organization (IMO) that establish global standards in ship design and construction.

  5. Validation of Chinese HY-2 satellite radar altimeter significant wave height

    Institute of Scientific and Technical Information of China (English)

    YE Xiaomin; LIN Mingsen; XU Ying

    2015-01-01

    Chinese Haiyang-2(HY-2) satellite is the first Chinese marine dynamic environment satellite. The dual-frequency (Ku and C band) radar altimeter onboard HY-2 has been working effective to provide operational significant wave height (SWH) for more than three years (October 1, 2011 to present).We validated along-track Ku-band SWH data of HY-2 satellite against National Data Buoy Center (NDBC)in-situ measurements over a time period of three years from October 1, 2011 to September 30, 2014, the root mean square error (RMSE) and mean bias of HY-2 SWH is 0.38 m and (–0.13±0.35) m, respectively. We also did cross validation against Jason-2 altimeter SWH data,the RMSE and the mean bias is 0.36m and (–0.22±0.28) m, respectively. In order to compare the statistical results between HY-2 and Jason-2 satellite SWH data, we validated the Jason-2 satellite radar altimeter along-track Ku-band SWH data against NDBC measurements using the same method. The results demonstrate the validation method in this study is scientific and the RMSE and mean bias of Jason-2 SWH data is 0.26 m and (0.00±0.26) m, respectively. We also validated both HY-2 and Jason-2 SWH data every month, the mean bias of Jason-2 SWH data almost equaled to zero all the time, while the mean bias of HY-2 SWH data was no less than –0.31m before April 2013 and dropped to zero after that time. These results indicate that the statistical results for HY-2 altimeter SWH are reliable and HY-2 altimeter along-track SWH data were steady and of high quality in the last three years. The results also indicate that HY-2 SWH data have greatly been improved and have the same accuracy with Jason-2 SWH data after April, 2013. SWH data provided by HY-2 satellite radar altimeter are useful and acceptable for ocean operational applications.

  6. Characterization of Wave Climate at Hanstholm Location with Focus on the Ratio between Average and Extreme Waves Heights

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Frigaard, Peter; Stratigaki, V.

    2011-01-01

    differences between the extreme wave conditions in which the device is designed to survive and the average wave conditions for which the device is to be optimised. Indeed, the ratio between extreme loads and operational loads has been identified to be a fundamental factor for the design and the cost analysis......The wave energy sector is in need of showing positive experience from the real sea trial in order to prove its feasibility. For this purpose, an accurate knowledge of wave conditions at the selected location of installation is fundamental. A design challenge for wave energy devices is the large...

  7. Blackfolds, Plane Waves and Minimal Surfaces

    CERN Document Server

    Armas, Jay

    2015-01-01

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid...

  8. Watching surface waves in phononic crystals.

    Science.gov (United States)

    Wright, Oliver B; Matsuda, Osamu

    2015-08-28

    In this paper, we review results obtained by ultrafast imaging of gigahertz surface acoustic waves in surface phononic crystals with one- and two-dimensional periodicities. By use of quasi-point-source optical excitation, we show how, from a series of images that form a movie of the travelling waves, the dispersion relation of the acoustic modes, their corresponding mode patterns and the position and widths of phonon stop bands can be obtained by temporal and spatio-temporal Fourier analysis. We further demonstrate how one can follow the temporal evolution of phononic eigenstates in k-space using data from phononic-crystal waveguides as an example. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  9. Wireless Multiplexed Surface Acoustic Wave Sensors Project

    Science.gov (United States)

    Youngquist, Robert C.

    2014-01-01

    Wireless Surface Acoustic Wave (SAW) Sensor is a new technology for obtaining multiple, real-time measurements under extreme environmental conditions. This project plans to develop a wireless multiplexed sensor system that uses SAW sensors, with no batteries or semiconductors, that are passive and rugged, can operate down to cryogenic temperatures and up to hundreds of degrees C, and can be used to sense a wide variety of parameters over reasonable distances (meters).

  10. Wave groups in uni-directional surface-wave models

    NARCIS (Netherlands)

    Groesen, van E.

    1998-01-01

    Uni-directional wave models are used to study wave groups that appear in wave tanks of hydrodynamic laboratories; characteristic for waves in such tanks is that the wave length is rather small, comparable to the depth of the layer. In second-order theory, the resulting Nonlinear Schrödinger (NLS) eq

  11. Broadband surface-wave transformation cloak

    Science.gov (United States)

    Xu, Su; Xu, Hongyi; Gao, Hanhong; Jiang, Yuyu; Yu, Faxin; Joannopoulos, John D.; Soljačić, Marin; Chen, Hongsheng; Sun, Handong; Zhang, Baile

    2015-01-01

    Guiding surface electromagnetic waves around disorder without disturbing the wave amplitude or phase is in great demand for modern photonic and plasmonic devices, but is fundamentally difficult to realize because light momentum must be conserved in a scattering event. A partial realization has been achieved by exploiting topological electromagnetic surface states, but this approach is limited to narrow-band light transmission and subject to phase disturbances in the presence of disorder. Recent advances in transformation optics apply principles of general relativity to curve the space for light, allowing one to match the momentum and phase of light around any disorder as if that disorder were not there. This feature has been exploited in the development of invisibility cloaks. An ideal invisibility cloak, however, would require the phase velocity of light being guided around the cloaked object to exceed the vacuum speed of light—a feat potentially achievable only over an extremely narrow band. In this work, we theoretically and experimentally show that the bottlenecks encountered in previous studies can be overcome. We introduce a class of cloaks capable of remarkable broadband surface electromagnetic waves guidance around ultrasharp corners and bumps with no perceptible changes in amplitude and phase. These cloaks consist of specifically designed nonmagnetic metamaterials and achieve nearly ideal transmission efficiency over a broadband frequency range from 0+ to 6 GHz. This work provides strong support for the application of transformation optics to plasmonic circuits and could pave the way toward high-performance, large-scale integrated photonic circuits. PMID:26056299

  12. Common-optical axis Fourier transform profilometry for water surface waves

    Science.gov (United States)

    Ghadiri, Mahdi; Krechetnikov, Rouslan

    2016-11-01

    The Fourier transform profilometry - a single-shot optical profilometric measurement of surface deformation - has been widely used to visualize and measure water surface waves. This well-known method is based on an optical system composed of a video projector displaying a fringe pattern on the surface and a camera recording this pattern as the reference image. The deformed fringe pattern following deformation of the surface later is then recorded and compared to the reference image in order to produce a phase map, from which the height of the deformed surface is reconstructed through a phase-to-height relation. The biggest challenge encountered while applying this method for water surface is the light reflection which previously has been partially treated by enhancing the water light diffusivity with the addition of Titanium dioxide. As part of the effort to improve the accuracy and practical applicability of the method, in this talk we will present a new implementation of a common-optical axis geometry along with an appropriate phase-height relation. Furthermore, in the case of water surface waves, we introduce a proper light filtration, which removes all the reflections remaining after addition of Titanium dioxide. The proposed technique provides an order of magnitude improvement in the accuracy of detecting and reconstructing the surface deformation, which is crucial for studying small amplitude waves and bifurcation phenomena.

  13. Parallel Algorithm in Surface Wave Waveform Inversion

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In Surface wave waveform inversion, we want to reconstruct 3Dshear wav e velocity structure, which calculation beyond the capability of the powerful pr esent day personal computer or even workstation. So we designed a high parallele d algorithm and carried out the inversion on Parallel computer based on the part itioned waveform inversion (PWI). It partitions the large scale optimization pro blem into a number of independent small scale problems and reduces the computati onal effort by several orders of magnitude. We adopted surface waveform inversio n with a equal block(2°×2°) discretization.

  14. Illusions and Cloaks for Surface Waves

    Science.gov (United States)

    McManus, T. M.; Valiente-Kroon, J. A.; Horsley, S. A. R.; Hao, Y.

    2014-08-01

    Ever since the inception of Transformation Optics (TO), new and exciting ideas have been proposed in the field of electromagnetics and the theory has been modified to work in such fields as acoustics and thermodynamics. The most well-known application of this theory is to cloaking, but another equally intriguing application of TO is the idea of an illusion device. Here, we propose a general method to transform electromagnetic waves between two arbitrary surfaces. This allows a flat surface to reproduce the scattering behaviour of a curved surface and vice versa, thereby giving rise to perfect optical illusion and cloaking devices, respectively. The performance of the proposed devices is simulated using thin effective media with engineered material properties. The scattering of the curved surface is shown to be reproduced by its flat analogue (for illusions) and vice versa for cloaks.

  15. Megaquakes, prograde surface waves and urban evolution

    Science.gov (United States)

    Lomnitz, C.; Castaños, H.

    2013-05-01

    Cities grow according to evolutionary principles. They move away from soft-ground conditions and avoid vulnerable types of structures. A megaquake generates prograde surface waves that produce unexpected damage in modern buildings. The examples (Figs. 1 and 2) were taken from the 1985 Mexico City and the 2010 Concepción, Chile megaquakes. About 400 structures built under supervision according to modern building codes were destroyed in the Mexican earthquake. All were sited on soft ground. A Rayleigh wave will cause surface particles to move as ellipses in a vertical plane. Building codes assume that this motion will be retrograde as on a homogeneous elastic halfspace, but soft soils are intermediate materials between a solid and a liquid. When Poisson's ratio tends to ν→0.5 the particle motion turns prograde as it would on a homogeneous fluid halfspace. Building codes assume that the tilt of the ground is not in phase with the acceleration but we show that structures on soft ground tilt into the direction of the horizontal ground acceleration. The combined effect of gravity and acceleration may destabilize a structure when it is in resonance with its eigenfrequency. Castaños, H. and C. Lomnitz, 2013. Charles Darwin and the 1835 Chile earthquake. Seismol. Res. Lett., 84, 19-23. Lomnitz, C., 1990. Mexico 1985: the case for gravity waves. Geophys. J. Int., 102, 569-572. Malischewsky, P.G. et al., 2008. The domain of existence of prograde Rayleigh-wave particle motion. Wave Motion 45, 556-564.; Figure 1 1985 Mexico megaquake--overturned 15-story apartment building in Mexico City ; Figure 2 2010 Chile megaquake Overturned 15-story R-C apartment building in Concepción

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

    Science.gov (United States)

    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.

  17. On the retrieval of significant wave heights from spaceborne Synthetic Aperture Radar using the Max-Planck Institut algorithm.

    Science.gov (United States)

    Violante-Carvalho, Nelson

    2005-12-01

    Synthetic Aperture Radar (SAR) onboard satellites is the only source of directional wave spectra with continuous and global coverage. Millions of SAR Wave Mode (SWM) imagettes have been acquired since the launch in the early 1990's of the first European Remote Sensing Satellite ERS-1 and its successors ERS-2 and ENVISAT, which has opened up many possibilities specially for wave data assimilation purposes. The main aim of data assimilation is to improve the forecasting introducing available observations into the modeling procedures in order to minimize the differences between model estimates and measurements. However there are limitations in the retrieval of the directional spectrum from SAR images due to nonlinearities in the mapping mechanism. The Max-Planck Institut (MPI) scheme, the first proposed and most widely used algorithm to retrieve directional wave spectra from SAR images, is employed to compare significant wave heights retrieved from ERS-1 SAR against buoy measurements and against the WAM wave model. It is shown that for periods shorter than 12 seconds the WAM model performs better than the MPI, despite the fact that the model is used as first guess to the MPI method, that is the retrieval is deteriorating the first guess. For periods longer than 12 seconds, the part of the spectrum that is directly measured by SAR, the performance of the MPI scheme is at least as good as the WAM model.

  18. Investigation of a digital FEM height reference surface as vertical reference system

    Science.gov (United States)

    Schneid, Sascha

    In recent years, the number of precise online DGNSS (Differential Global Navigation Satellite System) applications has significantly increased. Precise DGNSS correction services have been created that enable an online positioning with accuracy in the centimetre region, hi contrast to the co-ordinates found by DGNSS, the measured height needs to be transformed. This is because national height systems refer to a physically defined Height Reference Surface, HRS, that approximates the mean sea level, while the height derived from DGNSS positioning is the height above the WGS84 (World Geodetic System 1984), a mathematical model of the earth and is therefore called "ellipsoidal height". So for the application of precise DGNSS services and for the generation of transformation messages, such as RTCM 3.0, there is an urgent need for a HRS, in a unified datum with appropriate accuracy. This thesis deals with the concept of the Digital FEM (Finite Element Method) Height Reference Surface, DFHRS. This concept enables the rigorous least squares adjustment of any HRS related observation. The HRS is modelled as continuous surface by a local Taylor-series expansion in a grid of FEM-meshes. With this, areas of any size may be computed. The theory of the DFHRS and further development of the mathematical model, especially the incorporation of observed gravity accelerations, are the main parts of this thesis. As the applied Taylor-series expansion of the DFHRS concept only holds for a two- dimensional approximation. Spherical Cap Harmonics, SCH, had to be introduced as auxiliary parameter, to give a complete representation of the local gravity field. Spherical Cap Harmonics, SCH, may be interpreted as the general case of Spherical Harmonics, SH, that have been applied in geodetic applications for decades. The goal of the SCH coefficients, in contrast to the SH coefficients is that they may be applied over areas with limited extent. Due to numerical reasons, the combined least squares

  19. Impact of surface waves in a Regional Climate Model

    DEFF Research Database (Denmark)

    Rutgersson, Anna; Sætra, Oyvind; Semedo, Alvaro

    2010-01-01

    A coupled regional atmosphere-wave model system is developed with the purpose of investigating the impact of climate changes on the wave field, as well as feed-back effects of the wave field on the atmospheric parameters. This study focuses on the effects of introducing a two-way atmosphere-wave...... coupling on the atmosphere as well as on wave parameters. The model components are the regional climate model RCA, and the third generation wave model WAM. Two different methods are used for the coupling, using the roughness length and only including the effect of growing sea, and using the wave age...... and introducing the reduction of roughness due to decaying sea (swell). Introducing a two-way coupling results in an altered frequency distribution of wind speed and wave heights. When only including growing sea the impact of waves on the long term mean atmospheric parameters is limited, inducing a reduction...

  20. Impact of Assimilating Surface Velocity Observations on the Model Sea Surface Height Using the NCOM-4DVAR

    Science.gov (United States)

    2016-09-26

    atmospheric pressure , and surface heat flux is provided by the 0.58 NOGAPS model every 3h (Rosmond et al. 2002); river forcing is provided via an...horizontal pressure -gradient force in an oceanic model with nonaligned vertical grid. J. Geophys. Res., 108, 3090, doi:10.1029/2001JC001047. ——, and... Model Sea Surface Height Using the NCOM-4DVAR 0602435N 73-4727-14-5 MATTHEW J. CARRIER, HANS E. NGODOCK, PHILIP MUSCARELLA, AND SCOTT SMITH Naval

  1. Extraordinary transmission of gigahertz surface acoustic waves

    Science.gov (United States)

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H.; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H.; Wright, Oliver B.

    2016-09-01

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.

  2. Extraordinary transmission of gigahertz surface acoustic waves.

    Science.gov (United States)

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H; Wright, Oliver B

    2016-09-19

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3-50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.

  3. Extraordinary transmission of gigahertz surface acoustic waves

    Science.gov (United States)

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H.; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H.; Wright, Oliver B.

    2016-01-01

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging. PMID:27640998

  4. Interaction of Vortices with a progressive Surface Wave

    Institute of Scientific and Technical Information of China (English)

    LinlinWANG; HuiyangMA

    1996-01-01

    Interaction of submerged vortices with a progressive surface wave is investigated by the finite-difference numerical solution of Navier-Stokes equations.The progressive wave is the surface gravity water wave in a finite depth.The initial vortex model is Oseen vortex.The numerical computations show that a special pattern of the wave surface may be observed by the interaction from the submerged vortices.The influences of Froude number,the initial geometric configuration of vortices,and the amplitude,inital phase of surface wave on the wave pattern are discussed.

  5. The applicability of the dubois height weight formula for measurement of body surface of Indian subjects

    Directory of Open Access Journals (Sweden)

    S. S. Ramaswami

    1953-07-01

    Full Text Available The body surface area of 18 healthy adult Indian subjects was measured by taking part by part linear measurements for the whole body with the help of Anthropometry Beam Calipers and applying Du Bois linear formula method. The surface area values computed from Du Bois Height-weight formula were compared with the measured values. The average error in the eighteen cases is 1.5 percent. The standard deviation of the errors is 1.8 percent about the mean error of -0.5 percent. The errors are not statistically significant. As the original Du Bois formula itself is stated to have an average error of 1.5 percent, the present work confirms that the accuracy, with which Du Bois formula predicts body surface, is not sensibly different for Indians as against Europeans

  6. Evolution of bed form height and length during a discharge wave

    NARCIS (Netherlands)

    Warmink, J.J.; Schielen, R.M.J.; Dohmen-Janssen, C.M.; Lancker, van V.; Garlan, T.

    2013-01-01

    This research focusses on modeling the evolution of bed form during a discharge wave for application in operational flood forecasting. The objective of this research was to analyze and predict the bed form evolution during a discharge wave in a flume experiment. We analyzed the data of a flume exper

  7. Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

    CERN Document Server

    Gao, Zhen; Zhang, Baile

    2016-01-01

    We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices.

  8. Kernel empirical orthogonal function analysis of 1992-2008 global sea surface height anomaly data

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg; Andersen, Ole Baltazar; Knudsen, Per

    2009-01-01

    This paper describes a kernel version of empirical orthogonal function (EOF) analysis and its application to detect patterns of interest in global monthly mean sea surface height (SSH) anomalies from satellite altimetry acquired during the last 17 years. EOF analysis like principal component...... to large scale ocean currents and particularly to the pulsing of the El Niño/Southern Oscillation. Large scale ocean events associated with the El Niño/Southern Oscillation related signals are conveniently concentrated in the first SSH EOF modes. A major difference between the classical linear EOF...

  9. Surface height retrieval based on fringe shifting of color-encoded structured light pattern.

    Science.gov (United States)

    Chen, Hui Jun; Zhang, Jue; Fang, Jing

    2008-08-15

    A new method of fringe shifting for color structured pattern projection is presented for three-dimensional (3D) surface height measurement. Temporal encoding of color stripes is combined with locally spatial shifting of multiple fringes to realize image acquisition with a small number of pattern projections. Object topography is retrieved with high resolution by decoding the code word of each fringe with the help of the redundant information provided by the shifting patterns and the encoding patterns in their temporal and spatial neighborhoods. An application to evaluate the shape of a buckled tube demonstrates the effectiveness of the method.

  10. Steady periodic gravity waves with surface tension

    CERN Document Server

    Walsh, Samuel

    2009-01-01

    In this paper we consider two-dimensional, stratified, steady water waves propagating over an impermeable flat bed and with a free surface. The motion is assumed to be driven by capillarity (that is, surface tension) on the surface and a gravitational force acting on the body of the fluid. We prove the existence of global continua of classical solutions that are periodic and traveling. This is accomplished by first constructing a 1-parameter family of laminar flow solutions, $\\mathcal{T}$, then applying bifurcation theory methods to obtain local curves of small amplitude solutions branching from $\\mathcal{T}$ at an eigenvalue of the linearized problem. Each solution curve is then continued globally by means of a degree theoretic theorem in the spirit of Rabinowitz. Finally, we complement the degree theoretic picture by proving an alternate global bifurcation theorem via the analytic continuation method of Dancer.

  11. A Surface Acoustic Wave Ethanol Sensor with Zinc Oxide Nanorods

    Directory of Open Access Journals (Sweden)

    Timothy J. Giffney

    2012-01-01

    Full Text Available Surface acoustic wave (SAW sensors are a class of piezoelectric MEMS sensors which can achieve high sensitivity and excellent robustness. A surface acoustic wave ethanol sensor using ZnO nanorods has been developed and tested. Vertically oriented ZnO nanorods were produced on a ZnO/128∘ rotated Y-cut LiNbO3 layered SAW device using a solution growth method with zinc nitrate, hexamethylenetriamine, and polyethyleneimine. The nanorods have average diameter of 45 nm and height of 1 μm. The SAW device has a wavelength of 60 um and a center frequency of 66 MHz at room temperature. In testing at an operating temperature of 270∘C with an ethanol concentration of 2300 ppm, the sensor exhibited a 24 KHz frequency shift. This represents a significant improvement in comparison to an otherwise identical sensor using a ZnO thin film without nanorods, which had a frequency shift of 9 KHz.

  12. FREQUENCY LOCK—IN PHENOMENON OF FLAPPING MOTION WITH SURFACE WATER WAVE

    Institute of Scientific and Technical Information of China (English)

    HsuChintsau; KuangJun; SunJianhong

    2002-01-01

    To study the effect of a progressive surface wave on the flapping motion of a vertical turbulent plane jet in shallow water,the laser visualizations and measurements were carried out in a water tank.The images of visualization by laser-induced fluorescence(LIF)technique show that the jet flapping motion occurs in the wave environ-ment.Using the wave height gauge and laser Doppler velocimetry(LDV) ,experimental results show that the jet flapping motions indeed lock-in to the wave oscillations if the wave frequency is close to but lower than the nature frequency of jet flapping motion.The phenomenon does not occur when the wave frequency is above the nature frequency of jet flapping motion.

  13. SeaBuoySoft – an On-line Automated Windows based Ocean Wave height Data Acquisition and Analysis System for Coastal Field’s Data Collection

    Directory of Open Access Journals (Sweden)

    P.H.Tarudkar

    2014-12-01

    Full Text Available Measurement of various hydraulic parameters such as wave heights for the research and the practical purpose in the coastal fields is one of the critical and challenging but equally important criteria in the field of ocean engineering for the design and the development of hydraulic structures such as construction of sea walls, break waters, oil jetties, fisheries harbors, all other structures, and the ships maneuvering, embankments, berthing on jetties. This paper elucidates the development of “SeaBuoySoft online software system for coastal field‟s wave height data collection” for the coastal application work. The system could be installed along with the associated hardware such as a Digital Waverider Receiver unit and a Waverider Buoy at the shore. The ocean wave height data, transmitted by wave rider buoy installed in the shallow/offshore waters of sea is received by the digital waverider receiver unit and it is interfaced to the SeaBuoySoft software. The design and development of the software system has been worked out in-house at Central Water and Power Research Station, Pune, India. The software has been developed as a Windows based standalone version and is unique of its kind for the reception of real time ocean wave height data, it takes care of its local storage of wave height data for its further analysis work as and when required. The system acquires real time ocean wave height data round the clock requiring no operator intervention during data acquisition process on site.

  14. A proof of concept: Airborne LIDAR-measured ellipsoidal heights of a lake surface correspond to a local geoid model

    Science.gov (United States)

    Zlinszky, András; Ressl, Camillo; Timár, Gábor; Weber, Robert; Székely, Balázs; Briese, Christian; Pfeifer, Norbert

    2013-04-01

    accurate representation of the local geoid. In case of a natural lake, the question whether the water surface was in equilibrium has to be discussed. The lake lies perpendicular to the prevailing wind direction, so strong winds are known to displace the water surface and create differences in water levels known as seiche. However, during periods of relatively calm weather, these seiche effects remain low in amplitude. The airborne survey was carried out in a period of very calm weather and over several days, so this effect is believed to be negligible. The lake has a single outflow and a main tributary supplying more than half of the incoming water, but due to strong evaporation and relatively low input, the average turnover time for water in Lake Balaton is four years. This means that no significant deviation from the gravity-controlled equilibrium is expected to result from the flow of water. The errors remaining in the dataset are explained by the elevations of artificial structures such as boats and platforms that were not masked out as non water points, by the height of waves (up to 30 cm between neighbouring ALS points in some rare cases), and the slight systematic errors encountered around the edges of the scanned strips. Taking these errors into account, the good fit of the water surface elevation to the local geoid model has provided a proof of the concept of Newton. While this is evident based on the laws of hydrostatics, to our best knowledge, it has not yet been demonstrated by statistically sound measurements of a large natural inland water surface.

  15. Surface Features Parameterization and Equivalent Roughness Height Estimation of a Real Subglacial Conduit in the Arctic

    Science.gov (United States)

    Chen, Y.; Liu, X.; Manko ff, K. D.; Gulley, J. D.

    2016-12-01

    The surfaces of subglacial conduits are very complex, coupling multi-scale roughness, large sinuosity, and cross-sectional variations together. Those features significantly affect the friction law and drainage efficiency inside the conduit by altering velocity and pressure distributions, thus posing considerable influences on the dynamic development of the conduit. Parameterizing the above surface features is a first step towards understanding their hydraulic influences. A Matlab package is developed to extract the roughness field, the conduit centerline, and associated area and curvature data from the conduit surface, acquired from 3D scanning. By using those data, the characteristic vertical and horizontal roughness scales are then estimated based on the structure functions. The centerline sinuosities, defined through three concepts, i.e., the traditional definition of a fluvial river, entropy-based sinuosity, and curvature-based sinuosity, are also calculated and compared. The cross-sectional area and equivalent circular diameter along the centerline are also calculated. Among those features, the roughness is especially important due to its pivotal role in determining the wall friction, and thus an estimation of the equivalent roughness height is of great importance. To achieve such a goal, the original conduit is firstly simplified into a straight smooth pipe with the same volume and centerline length, and the roughness field obtained above is then reconstructed into the simplified pipe. An OpenFOAM-based Large-eddy-simulation (LES) is then performed based on the reconstructed pipe. Considering that the Reynolds number is of the order 106, and the relative roughness is larger than 5% for 60% of the conduit, we test the validity of the resistance law for completely rough pipe. The friction factor is calculated based on the pressure drop and mean velocity in the simulation. Working together, the equivalent roughness height can be calculated. However, whether the

  16. Scattered surface wave energy in the seismic coda

    Science.gov (United States)

    Zeng, Y.

    2006-01-01

    One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.

  17. Piezoelectric Film Waveguides for Surface Acoustic Waves

    Directory of Open Access Journals (Sweden)

    M.F. Zhovnir

    2016-11-01

    Full Text Available The paper presents results of mathematical modeling of piezoelectric film waveguide structures for surface acoustic waves (SAW. Piezoelectric ZnO film is supposed to be placed on a fused quartz substrate. The analytical ratios and numerical results allow to determine the design parameters of the waveguide structures to provide a single-mode SAW propagation mode. The results of amplitude and phase experimental studies of the SAW in the waveguide structures that were carried out on the laser optical sensing set up confirm the theoretical calculations.

  18. Surface Acoustic Wave Atomizer and Electrostatic Deposition

    Science.gov (United States)

    Yamagata, Yutaka

    A new methodology for fabricating thin film or micro patters of organic/bio material using surface acoustic wave (SAW) atomizer and electrostatic deposition is proposed and characteristics of atomization techniques are discussed in terms of drop size and atomization speed. Various types of SAW atomizer are compared with electrospray and conventional ultrasonic atomizers. It has been proved that SAW atomizers generate drops as small as electrospray and have very fast atomization speed. This technique is applied to fabrication of micro patterns of proteins. According to the result of immunoassay, the specific activity of immunoglobulin was preserved after deposition process.

  19. Absorption of surface acoustic waves by graphene

    Directory of Open Access Journals (Sweden)

    S. H. Zhang

    2011-06-01

    Full Text Available We present a theoretical study on interactions of electrons in graphene with surface acoustic waves (SAWs. We find that owing to momentum and energy conservation laws, the electronic transition accompanied by the SAW absorption cannot be achieved via inter-band transition channels in graphene. For graphene, strong absorption of SAWs can be observed in a wide frequency range up to terahertz at room temperature. The intensity of SAW absorption by graphene depends strongly on temperature and can be adjusted by changing the carrier density. This study is relevant to the exploration of the acoustic properties of graphene and to the application of graphene as frequency-tunable SAW devices.

  20. Surface waves in fibre-reinforced anisotropic elastic media

    Indian Academy of Sciences (India)

    P R Sengupta; Sisir Nath

    2001-08-01

    The aim of this paper is to investigate surface waves in anisotropic fibre-reinforced solid elastic media. First, the theory of general surface waves has been derived and applied to study the particular cases of surface waves – Rayleigh, Love and Stoneley types. The wave velocity equations are found to be in agreement with the corresponding classical result when the anisotropic elastic parameters tends to zero. It is important to note that the Rayleigh type of wave velocity in the fibre-reinforced elastic medium increases to a considerable amount in comparison with the Rayleigh wave velocity in isotropic materials.

  1. Resonant surface acoustic wave chemical detector

    Energy Technology Data Exchange (ETDEWEB)

    Brocato, Robert W.; Brocato, Terisse; Stotts, Larry G.

    2017-08-08

    Apparatus for chemical detection includes a pair of interdigitated transducers (IDTs) formed on a piezoelectric substrate. The apparatus includes a layer of adsorptive material deposited on a surface of the piezoelectric substrate between the IDTs, where each IDT is conformed, and is dimensioned in relation to an operating frequency and an acoustic velocity of the piezoelectric substrate, so as to function as a single-phase uni-directional transducer (SPUDT) at the operating frequency. Additionally, the apparatus includes the pair of IDTs is spaced apart along a propagation axis and mutually aligned relative to said propagation axis so as to define an acoustic cavity that is resonant to surface acoustic waves (SAWs) at the operating frequency, where a distance between each IDT of the pair of IDTs ranges from 100 wavelength of the operating frequency to 400 wavelength of the operating frequency.

  2. Multi-scale wavelet analysis of TOPEX/Poseidon altimeter significant wave height in eastern China seas

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The multi-scale characteristics of wave significant height (Hs) in eastern China seas were revealed by multi-scale wavelet analysis. In order to understand the relation between wave and wind, the TOPEX/Poseidon measurements of Hs and wind speed were analyzed. The result showed that Hs and wind speed change in multi-scale at one-, two-month, half-, one- and two-year cycles. But in a larger time scale, the variations in Hs and wind speed are different. Hs has a five-year cycle similar to the cycle of ENSO variation, while the wind speed has no such cycle. In the time domain, the correlation between Hs and ENSO is unclear.

  3. A new global model for the ionospheric F2 peak height for radio wave propagation

    Directory of Open Access Journals (Sweden)

    M. M. Hoque

    2012-05-01

    Full Text Available The F2-layer peak density height hmF2 is one of the most important ionospheric parameters characterizing HF propagation conditions. Therefore, the ability to model and predict the spatial and temporal variations of the peak electron density height is of great use for both ionospheric research and radio frequency planning and operation. For global hmF2 modelling we present a nonlinear model approach with 13 model coefficients and a few empirically fixed parameters. The model approach describes the temporal and spatial dependencies of hmF2 on global scale. For determining the 13 model coefficients, we apply this model approach to a large quantity of global hmF2 observational data obtained from GNSS radio occultation measurements onboard CHAMP, GRACE and COSMIC satellites and data from 69 worldwide ionosonde stations. We have found that the model fits to these input data with the same root mean squared (RMS and standard deviations of 10%. In comparison with the electron density NeQuick model, the proposed Neustrelitz global hmF2 model (Neustrelitz Peak Height Model – NPHM shows percentage RMS deviations of about 13% and 12% from the observational data during high and low solar activity conditions, respectively, whereas the corresponding deviations for the NeQuick model are found 18% and 16%, respectively.

  4. Numerical simulations and observations of surface wave fields under an extreme tropical cyclone

    Science.gov (United States)

    Fan, Y.; Ginis, I.; Hara, T.; Wright, C.W.; Walsh, E.J.

    2009-01-01

    The performance of the wave model WAVEWATCH III under a very strong, category 5, tropical cyclone wind forcing is investigated with different drag coefficient parameterizations and ocean current inputs. The model results are compared with field observations of the surface wave spectra from an airborne scanning radar altimeter, National Data Buoy Center (NDBC) time series, and satellite altimeter measurements in Hurricane Ivan (2004). The results suggest that the model with the original drag coefficient parameterization tends to overestimate the significant wave height and the dominant wavelength and produces a wave spectrum with narrower directional spreading. When an improved drag parameterization is introduced and the wave-current interaction is included, the model yields an improved forecast of significant wave height, but underestimates the dominant wavelength. When the hurricane moves over a preexisting mesoscale ocean feature, such as the Loop Current in the Gulf of Mexico or a warm-and cold-core ring, the current associated with the feature can accelerate or decelerate the wave propagation and significantly modulate the wave spectrum. ?? 2009 American Meteorological Society.

  5. Surface Plasmon Wave Adapter Designed with Transformation Optics

    DEFF Research Database (Denmark)

    Zhang, Jingjing; Xiao, Sanshui; Wubs, Martijn

    2011-01-01

    On the basis of transformation optics, we propose the design of a surface plasmon wave adapter which confines surface plasmon waves on non-uniform metal surfaces and enables adiabatic mode transformation of surface plasmon polaritons with very short tapers. This adapter can be simply achieved...... with homogeneous anisotropic naturally occurring materials or subwavelength grating-structured dielectric materials. Full wave simulations based on a finite-element method have been performed to validate our proposal....

  6. Surface Plasmon Wave Adapter Designed with Transformation Optics

    DEFF Research Database (Denmark)

    Zhang, Jingjing; Xiao, Sanshui; Wubs, Martijn;

    2011-01-01

    On the basis of transformation optics, we propose the design of a surface plasmon wave adapter which confines surface plasmon waves on non-uniform metal surfaces and enables adiabatic mode transformation of surface plasmon polaritons with very short tapers. This adapter can be simply achieved...... with homogeneous anisotropic naturally occurring materials or subwavelength grating-structured dielectric materials. Full wave simulations based on a finite-element method have been performed to validate our proposal....

  7. A next generation altimeter for mapping the sea surface height variability: opportunities and challenges

    Science.gov (United States)

    Fu, Lee-Lueng; Morrow, Rosemary

    2016-07-01

    The global observations of the sea surface height (SSH) have revolutionized oceanography since the beginning of precision radar altimetry in the early 1990s. For the first time we have continuous records of SSH with spatial and temporal sampling for detecting the global mean sea level rise, the waxing and waning of El Niño, and the ocean circulation from gyres to ocean eddies. The limit of spatial resolution of the present constellation of radar altimeters in mapping SSH variability is approaching 100 km (in wavelength) with 3 or more simultaneous altimetric satellites in orbit. At scales shorter than 100 km, the circulation contains substantial amount of kinetic energy in currents, eddies and fronts that are responsible for the stirring and mixing of the ocean, especially from the vertical exchange of the upper ocean with the deep. A mission currently in development will use the technique of radar interferometry for making high-resolution measurement of the height of water over the ocean as well as on land. It is called Surface Water and Ocean Topography (SWOT), which is a joint mission of US NASA and French CNES, with contributions from Canada and UK. SWOT promises the detection of SSH at scales approaching 15 km, depending on the sea state. SWOT will make SSH measurement over a swath of 120 km with a nadir gap of 20 km in a 21-day repeat orbit. A conventional radar altimeter will provide measurement along the nadir. This is an exploratory mission with applications in oceanography and hydrology. The increased spatial resolution offers an opportunity to study ocean surface processes to address important questions about the ocean circulation. However, the limited temporal sampling poses challenges to map the evolution of the ocean variability that changes rapidly at the small scales. The measurement technique and the development of the mission will be presented with emphasis on its science program with outlook on the opportunities and challenges.

  8. Satellite altimetry in sea ice regions - detecting open water for estimating sea surface heights

    Science.gov (United States)

    Müller, Felix L.; Dettmering, Denise; Bosch, Wolfgang

    2017-04-01

    The Greenland Sea and the Farm Strait are transporting sea ice from the central Arctic ocean southwards. They are covered by a dynamic changing sea ice layer with significant influences on the Earth climate system. Between the sea ice there exist various sized open water areas known as leads, straight lined open water areas, and polynyas exhibiting a circular shape. Identifying these leads by satellite altimetry enables the extraction of sea surface height information. Analyzing the radar echoes, also called waveforms, provides information on the surface backscatter characteristics. For example waveforms reflected by calm water have a very narrow and single-peaked shape. Waveforms reflected by sea ice show more variability due to diffuse scattering. Here we analyze altimeter waveforms from different conventional pulse-limited satellite altimeters to separate open water and sea ice waveforms. An unsupervised classification approach employing partitional clustering algorithms such as K-medoids and memory-based classification methods such as K-nearest neighbor is used. The classification is based on six parameters derived from the waveform's shape, for example the maximum power or the peak's width. The open-water detection is quantitatively compared to SAR images processed while accounting for sea ice motion. The classification results are used to derive information about the temporal evolution of sea ice extent and sea surface heights. They allow to provide evidence on climate change relevant influences as for example Arctic sea level rise due to enhanced melting rates of Greenland's glaciers and an increasing fresh water influx into the Arctic ocean. Additionally, the sea ice cover extent analyzed over a long-time period provides an important indicator for a globally changing climate system.

  9. Toward autonomous surface-based infrared remote sensing of polar clouds: cloud-height retrievals

    Science.gov (United States)

    Rowe, Penny M.; Cox, Christopher J.; Walden, Von P.

    2016-08-01

    Polar regions are characterized by their remoteness, making measurements challenging, but an improved knowledge of clouds and radiation is necessary to understand polar climate change. Infrared radiance spectrometers can operate continuously from the surface and have low power requirements relative to active sensors. Here we explore the feasibility of retrieving cloud height with an infrared spectrometer that would be designed for use in remote polar locations. Using a wide variety of simulated spectra of mixed-phase polar clouds at varying instrument resolutions, retrieval accuracy is explored using the CO2 slicing/sorting and the minimum local emissivity variance (MLEV) methods. In the absence of imposed errors and for clouds with optical depths greater than ˜ 0.3, cloud-height retrievals from simulated spectra using CO2 slicing/sorting and MLEV are found to have roughly equivalent high accuracies: at an instrument resolution of 0.5 cm-1, mean biases are found to be ˜ 0.2 km for clouds with bases below 2 and -0.2 km for higher clouds. Accuracy is found to decrease with coarsening resolution and become worse overall for MLEV than for CO2 slicing/sorting; however, the two methods have differing sensitivity to different sources of error, suggesting an approach that combines them. For expected errors in the atmospheric state as well as both instrument noise and bias of 0.2 mW/(m2 sr cm-1), at a resolution of 4 cm-1, average retrieval errors are found to be less than ˜ 0.5 km for cloud bases within 1 km of the surface, increasing to ˜ 1.5 km at 4 km. This sensitivity indicates that a portable, surface-based infrared radiance spectrometer could provide an important complement in remote locations to satellite-based measurements, for which retrievals of low-level cloud are challenging.

  10. Predicting Boat-Generated Wave Heights: A Quantitative Analysis through Video Observations of Vessel Wakes

    Science.gov (United States)

    2012-05-18

    Engineering ________________________________ (signature) Acceptance for the Trident Scholar Committee Professor Carl Wick Deputy Director of Research... Whittaker et al, 2001). The angle of propagation increases and is dependent on the depth Froude number...7) Figure 4: Super-critical wave pattern (Adapted from Whittaker et al, 2001) 18 Therefore, when

  11. Joint Occurrence Period of Wind Speed and Wave Height Based on Both Service Term and Risk Probability

    Institute of Scientific and Technical Information of China (English)

    DONG Sheng; FAN Dunqiu; TAO Shanshan

    2012-01-01

    Return periods calculated for different environmental conditions are key parameters for ocean platform design.Many codes for offshore structure design give no consideration about the correlativity among multi-loads and over-estimate design values.This frequently leads to not only higher investment but also distortion of structural reliability analysis.The definition of design return period in existing codes and industry criteria in China are summarized.Then joint retum periods of different ocean environmental parameters are determined from the view of service term and danger risk.Based on a bivariate equivalent maximum entropy distribution,joint design parameters are estimated for the concomitant wave height and wind speed at a site in the Bohai Sea.The calculated results show that even if the return period of each environmental factor,such as wave height or wind speed,is small,their combinations can lead to larger joint return periods.Proper design criteria for joint return period associated with concomitant environmental conditions will reduce structural size and lead to lower investment of ocean platforms for the exploitation of marginal oil field.

  12. Satellite-derived sea surface height and sea surface wind data fusion for spilled oil tracking

    Science.gov (United States)

    Kozai, Katsutoshi

    2003-12-01

    An attempt is made to estimate the trajectory of the spilled oil from the sunken tanker Nakhodka occurred on January 2, 1997 in the Japan Sea by fusing two microwave sensor data, namely ERS-2 altimeter and ADEOS/NSCAT scatterometer data. In this study 'fusion' is defined as the method of more reliable prediction for the trajectory of spilled oil than before. Geostrophic current vectors are derived from ERS-2 altimeter and wind-induced drift vectors are derived from ADEOS/NSCAT scatterometer data These two different satellite-derived vectors are 'fused' together in the surface current model to estimate and evaluate the trajectory of spilled oil from the sunken tanker Nakhodka. The distribution of component of spill vector is mostly accounted for by the distribution of geostrophic velocity component during the study period with some discrepancies during March, 1997.

  13. Engineered metabarrier as shield from seismic surface waves

    OpenAIRE

    2016-01-01

    Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by bu...

  14. On elliptic cylindrical Kadomtsev-Petviashvili equation for surface waves

    CERN Document Server

    Khusnutdinova, K R; Matveev, V B; Smirnov, A O

    2012-01-01

    The `elliptic cylindrical Kadomtsev-Petviashvili equation' is derived for surface gravity waves with nearly-elliptic front, generalising the cylindrical KP equation for nearly-concentric waves. We discuss transformations between the derived equation and two existing versions of the KP equation, for nearly-plane and nearly-concentric waves. The transformations are used to construct important classes of exact solutions of the derived equation and corresponding approximate solutions for surface waves.

  15. Surface wave inversion for a p-wave velocity profile: Estimation of the squared slowness gradient

    NARCIS (Netherlands)

    Ponomarenko, A.V.; Kashtan, B.M.; Troyan, V.N.; Mulder, W.A.

    2013-01-01

    Surface waves can be used to obtain a near-surface shear wave profile. The inverse problem is usually solved for the locally 1-D problem of a set of homogeneous horizontal elastic layers. The output is a set of shear velocity values for each layer in the profile. P-wave velocity profile can be estim

  16. Surface-wave mode coupling : modelling and inverting waveforms including body-wave phases

    NARCIS (Netherlands)

    Marquering, H.A.

    1996-01-01

    This thesis is concerned with a similar problem as addressed by Li & Tanimoto (1993) in the surfacewave mode approach. In this thesis it is shown that surface-wave mode coupling is required when body-wave phases in laterally heterogeneous media are modelled by surface-wave mode summation. An efficie

  17. Changes in extreme regional sea surface height due to an abrupt weakening of the Atlantic MOC

    Directory of Open Access Journals (Sweden)

    S.-E. Brunnabend

    2014-04-01

    Full Text Available As an extreme scenario of dynamical sea level changes, regional sea surface height (SSH changes that occur in the North Atlantic due to an abrupt weakening of the Atlantic Meridional Overturning Circulation (AMOC are simulated. Two versions of the same ocean-only model are used to study the effect of ocean model resolution on these SSH changes: a high-resolution (HR strongly eddying version and a low-resolution (LR version in which the effect of eddies are parameterized. The weakening of the AMOC is induced in both model versions by applying strong freshwater perturbations around Greenland. A rapid decrease of the AMOC in the HR version induces much shorter return times of several specific regional and coastal extremes in North Atlantic SSH than in the LR version. This effect is caused by a change in main eddy pathways associated with a change in separation latitude of the Gulf Stream.

  18. Dispersion and Polarization of Surface Waves Trapped in High Aspect Ratio Electrode Arrays

    DEFF Research Database (Denmark)

    Laude, Vincent; Dühring, Maria Bayard; Moubchir, Hanane

    2007-01-01

    .Phys., 90(5):2492, 2001; Appl. Phys. Lett., 89:083515, 2006.) an experimental and theoretical analysis of the transduction of SAW under a metallic array of electrodes with a large aspect ratio on a piezoelectric substrate, whereby allowing the electrode height to become larger than one wavelength....... The multimode character of SAW propagation was observed and the explicit dependence of the SAW velocities as a function of the electrode height was obtained experimentally. Up to a 10-fold slowing of surface waves was observed, with the phase velocity dropping from 4000 m/s down to 450 m/s. We present...

  19. Surface-acoustic-wave (SAW) flow sensor

    Science.gov (United States)

    Joshi, Shrinivas G.

    1991-03-01

    The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 deg rotated Y-cut lithium niobate substrate and heated to 55 C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cu cm/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

  20. Surface Waves in Almost Incompressible Elastic Materials

    CERN Document Server

    Virta, Kristoffer

    2013-01-01

    A recent study shows that the classical theory concerning accuracy and points per wavelength is not valid for surface waves in almost incompressible elastic materials. The grid size must instead be proportional to $(\\frac{\\mu}{\\lambda})^{(1/p)}$ to achieve a certain accuracy. Here $p$ is the order of accuracy the scheme and $\\mu$ and $\\lambda$ are the Lame parameters. This accuracy requirement becomes very restrictive close to the incompressible limit where $\\frac{\\mu}{\\lambda} \\ll 1$, especially for low order methods. We present results concerning how to choose the number of grid points for 4th, 6th and 8th order summation-by-parts finite difference schemes. The result is applied to Lambs problem in an almost incompressible material.

  1. The radiation of surface wave energy: Implications for volcanic tremor

    Science.gov (United States)

    Haney, M. M.; Denolle, M.; Lyons, J. J.; Nakahara, H.

    2015-12-01

    The seismic energy radiated by active volcanism is one common measurement of eruption size. For example, the magnitudes of individual earthquakes in volcano-tectonic (VT) swarms can be summed and expressed in terms of cumulative magnitude, energy, or moment release. However, discrepancies exist in current practice when treating the radiated energy of volcano seismicity dominated by surface waves. This has implications for volcanic tremor, since eruption tremor typically originates at shallow depth and is made up of surface waves. In the absence of a method to compute surface wave energy, estimates of eruption energy partitioning between acoustic and seismic waves typically assume seismic energy is composed of body waves. Furthermore, without the proper treatment of surface wave energy, it is unclear how much volcanic tremor contributes to the overall seismic energy budget during volcanic unrest. To address this issue, we derive, from first principles, the expression of surface wave radiated energy. In contrast with body waves, the surface wave energy equation is naturally expressed in the frequency domain instead of the time domain. We validate our result by reproducing an analytical solution for the radiated power of a vertical force source acting on a free surface. We further show that the surface wave energy equation leads to an explicit relationship between energy and the imaginary part of the surface wave Green's tensor at the source location, a fundamental property recognized within the field of seismic interferometry. With the new surface wave energy equation, we make clear connections to reduced displacement and propose an improved formula for the calculation of surface wave reduced displacement involving integration over the frequency band of tremor. As an alternative to reduced displacement, we show that reduced particle velocity squared is also a valid physical measure of tremor size, one based on seismic energy rate instead of seismic moment rate. These

  2. Sea surface height variability in the North East Atlantic from satellite altimetry

    Science.gov (United States)

    Sterlini, Paul; de Vries, Hylke; Katsman, Caroline

    2016-08-01

    Data from 21 years of satellite altimeter measurements are used to identify and understand the major contributing components of sea surface height variability (SSV) on monthly time-scales in the North East Atlantic. A number of SSV drivers is considered, which are categorised into two groups; local (wind and sea surface temperature) and remote (sea level pressure and the North Atlantic oscillation index). A multiple linear regression model is constructed to model the SSV for a specific target area in the North Sea basin. Cross-correlations between candidate regressors potentially lead to ambiguity in the interpretation of the results. We therefore use an objective hierarchical selection method based on variance inflation factors to select the optimal number of regressors for the target area and accept these into the regression model if they can be associated to SSV through a direct underlying physical forcing mechanism. Results show that a region of high SSV exists off the west coast of Denmark and that it can be represented well with a regression model that uses local wind, sea surface temperature and sea level pressure as primary regressors. The regression model developed here helps to understand sea level change in the North East Atlantic. The methodology is generalised and easily applied to other regions.

  3. Adjusting altimetric sea surface height observations in coastal regions. Case study in the Greek Seas

    Directory of Open Access Journals (Sweden)

    Mintourakis Ioannis

    2014-09-01

    Full Text Available When processing satellite altimetry data for Mean Sea Surface (MSS modelling in coastal environments many problems arise. The degradation of the accuracy of the Sea Surface Height (SSH observations close to the coastline and the usually irregular pattern and variability of the sea surface topography are the two dominant factors which have to be addressed. In the present paper, we study the statistical behavior of the SSH observations in relation to the range from the coastline for many satellite altimetry missions and we make an effort to minimize the effects of the ocean variability. Based on the above concepts we present a process strategy for the homogenization of multi satellite altimetry data that takes advantage ofweighted SSH observations and applies high degree polynomials for the adjustment and their uniffcation at a common epoch. At each step we present the contribution of each concept to MSS modelling and then we develop a MSS, a marine geoid model and a grid of gravity Free Air Anomalies (FAA for the area under study. Finally, we evaluate the accuracy of the resulting models by comparisons to state of the art global models and other available data such as GPS/leveling points, marine GPS SSH’s and marine gravity FAA’s, in order to investigate any progress achieved by the presented strategy

  4. Significant wave height estimation using azimuth cutoff of C-band RADARSAT-2 single-polarization SAR images

    Institute of Scientific and Technical Information of China (English)

    REN Lin; YANG Jingsong; ZHENG Gang; WANG Juan

    2015-01-01

    This paper proposes two simple models, look-up table (LUT) model and empirical model, to directly retrieve significant wave height (Hs) using synthetic aperture radar (SAR) azimuth cutoff (λc). Both models aim at C-band VV, HH, VH, and HV single-polarization SAR images. The LUT model relatesHs toλc, while the empirical model relatesHs to bothλc and SAR range-to-velocity (β). The LUT model coefficients are derived by simulation under different sea states and observation conditions, which depend on incidence angle (θ), wave direction (dw), andβbut are independent of polarization. The empirical model coefficients are obtained by fitting the collocated data, which only depend on polarization. To fit empirical model coefficients and validate the two models, C-band RADARSAT-2 fine quad-polarization (VV+HH+VH+HV) single-look complex (SLC) SAR images and collocated buoy data are collected. RetrievedHs, using Yang model and the two models proposed in this paper from four kinds of polarization SAR data, are compared with buoyHs. Results show that both LUT and empirical models have the capacity of retrievingHs from C-band RADARSAT-2 co-polarization SAR data, while Yang model is not suitable for these kinds of SAR data. Moreover, the empirical model is also valid for cross-polarization SAR data showing clear ocean wave stripes.

  5. Experimental Evaluation of the Atmospheric Energy Input to Sea Surface Waves

    Science.gov (United States)

    2011-09-30

    with sonic anemometers , cups , vanes, measuring airflow velocity, sensitive barometers. Instruments for GPS and inertial navigation were positioned...constant, Ω is the Instruments Quantity measured Height/Location 7 Sonic Anemometers Wind velocity, Air temperature On the mast 5 RMY Prop... Anemometers Wind speed & direction At 5 levels on the mast 8 Pressure Instruments Atmospheric pressure On the mast 2 Wave Wires Sea surface elevation At

  6. Simulation and Optimization of Surface Acoustic Wave Devises

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    2007-01-01

    In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model of a piezoele......In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model...

  7. Surface acoustic wave (SAW) vibration sensors.

    Science.gov (United States)

    Filipiak, Jerzy; Solarz, Lech; Steczko, Grzegorz

    2011-01-01

    In the paper a feasibility study on the use of surface acoustic wave (SAW) vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.

  8. Surface Acoustic Wave (SAW Vibration Sensors

    Directory of Open Access Journals (Sweden)

    Jerzy Filipiak

    2011-12-01

    Full Text Available In the paper a feasibility study on the use of surface acoustic wave (SAW vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.

  9. An Efficient Hydrodynamic Model for Surface Waves

    Institute of Scientific and Technical Information of China (English)

    WANG Kun; JIN Sheng; LU Gang

    2009-01-01

    In the present study,a semi-implicit finite difference model for non-bydrostatic,free-surface flows is analyzed and discussed.The governing equations are the three-dimensional free-surface Reynolds-averaged Navier-Stokes equations defined on a general,irregular domain of arbitrary scale.At outflow,a combination of a sponge layer technique and a radiation boundary condition is applied to minimize wave reflection.The equations are solved with the fractional step method where the hydrostatic pressure component is determined first,while the non-hydrostatic component of the pressure is computed from the pressure Poisson equation in which the coefficient matrix is positive definite and symmetric.The advectiou and horizontal viscosity terms are discretized by use of a semi-Lagrangian approach.The resulting model is computationally efficient and unrestricted to the CFL condition.The developed model is verified against analytical solutions and experimental data,with excellent agreement.

  10. Statistical model on the surface elevation of waves with breaking

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In the surface wind drift layer with constant momentum flux, two sets of the consistent surface eleva- tion expressions with breaking and occurrence conditions for breaking are deduced from the first in- tegrals of the energy and vortex variations and the kinetic and mathematic breaking criterions, then the expression of the surface elevation with wave breaking is established by using the Heaviside function. On the basis of the form of the sea surface elevation with wave breaking and the understanding of small slope sea waves, a triple composite function of real sea waves is presented including the func- tions for the breaking, weak-nonlinear and basic waves. The expression of the triple composite func- tion and the normal distribution of basic waves are the expected theoretical model for surface elevation statistics.

  11. Spoof surface plasmon Fabry-Perot open resonators in a surface-wave photonic crystal

    CERN Document Server

    Gao, Zhen; Xu, Hongyi; Zhang, Youming; Zhang, Baile

    2016-01-01

    We report on the proposal and experimental realization of a spoof surface plasmon Fabry-Perot (FP) open resonator in a surface-wave photonic crystal. This surface-wave FP open resonator is formed by introducing a finite line defect in a surface-wave photonic crystal. The resonance frequencies of the surface-wave FP open resonator lie exactly within the forbidden band gap of the surface-wave photonic crystal and the FP open resonator uses this complete forbidden band gap to concentrate surface waves within a subwavelength cavity. Due to the complete forbidden band gap of the surface-wave photonic crystal, a new FP plasmonic resonance mode that exhibits monopolar features which is missing in traditional FP resonators and plasmonic resonators is demonstrated. Near-field response spectra and mode profiles are presented in the microwave regime to characterize properties of the proposed FP open resonator for spoof surface plasmons.

  12. Improving the Accuracy of Coastal Sea Surface Heights by Retracking Decontaminated Radar Altimetry Waveforms

    Science.gov (United States)

    Huang, Zhengkai; Wang, Haihong; Luo, Zhicai

    2017-04-01

    Due to the complex coastal topography and energetic ocean dynamics effect, the return echoes are contaminated while the satellite footprint approaches or leaves the coastline. Specular peaks are often induced in the trailing edges of contaminated waveforms, thus leading the error in the determination of the leading edge and associated track offset in the waveform retracking process. We propose an improved algorithm base on Tseng's modification method to decontaminated coastal (0-7 km from coastline) waveforms, thus improving both the utilization and precision of coastal sea surface height (SSH). Using the Envisat/Jason-2 SGDR data, the shortcoming of Tseng's method is pointed out and the novel algorithm is proposed by revising the strategy of selecting reference waveform and determining weight for removing outlier. The reference waveform of the decontaminated technology is closer to the real waveform of the offshore area, which avoids the over-modification problem of Tseng method. The sea-level measurements from tide gauge station and geoid height from EGM2008 model were used to validate the retracking strategy. Experimental results show that decontaminated waveform was more suitable than original and Tseng modified waveform and has uniform performance in both compare to the tide gauge and geoid. The retrieved altimetry data in the 0-1km and 1-7km coastal zone indicate that threshold retracker with decontaminated waveform have STD of 73.8cm and 33cm as compared with in situ gauge data,which correspond to 62.1% and 58% in precession compared to the unretracked altimetry measurements. The retracked SSHs are better in two coastal (0-1 km and 1-7km) zones, which have STD of 11.9cm and 22.7cm as compared with geoid height. Furthermore, the comparisons shows that the precision of decontaminated technology improve 0.3cm and 3.3cm than the best result of PISTACH product in coastal sea. This work is supported by the National Natural Science Foundation of China (Grant Nos

  13. Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

    Science.gov (United States)

    Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

    2017-08-01

    The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

  14. Ocean surface waves and winds over the north Indian Ocean from satellite altimeter - preliminary results of SAC-NIO joint project

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.; Rajkumar, R.; Gairola, R.M.; Gohil, B.S.; Vethamony, P.; Rao, L.V.G.

    and NIO. Though there had been three cruises during the period, there were very few satellite-ship overlaps. Data pairs (satellite derived and in situ) of surface wind speed, significant wave height and minimum significant swell height were used to find...

  15. Surface spin-electron acoustic waves in magnetically ordered metals

    CERN Document Server

    Andreev, Pavel A

    2015-01-01

    Degenerate plasmas with motionless ions show existence of three surface waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound. Applying the separated spin evolution quantum hydrodynamics to half-space plasma we demonstrate the existence of the surface spin-electron acoustic wave (SSEAW). We study dispersion of the SSEAW. We show that there is hybridization between the surface Langmuir wave and the SSEAW at rather small spin polarization. In the hybridization area the dispersion branches are located close to each other. In this area there is a strong interaction between these waves leading to the energy exchange. Consequently, generating the Langmuir waves with the frequencies close to hybridization area we can generate the SSEAWs. Thus, we report a method of creation of the SEAWs.

  16. Observation of resonant interactions among surface gravity waves

    CERN Document Server

    Bonnefoy, F; Michel, G; Semin, B; Humbert, T; Aumaître, S; Berhanu, M; Falcon, E

    2016-01-01

    We experimentally study resonant interactions of oblique surface gravity waves in a large basin. Our results strongly extend previous experimental results performed mainly for perpendicular or collinear wave trains. We generate two oblique waves crossing at an acute angle, while we control their frequency ratio, steepnesses and directions. These mother waves mutually interact and give birth to a resonant wave whose properties (growth rate, resonant response curve and phase locking) are fully characterized. All our experimental results are found in good quantitative agreement with four-wave interaction theory with no fitting parameter. Off-resonance experiments are also reported and the relevant theoretical analysis is conducted and validated.

  17. Opportunities and pitfalls in surface-wave interpretation

    KAUST Repository

    Schuster, Gerard T.

    2017-01-21

    Many explorationists think of surface waves as the most damaging noise in land seismic data. Thus, much effort is spent in designing geophone arrays and filtering methods that attenuate these noisy events. It is now becoming apparent that surface waves can be a valuable ally in characterizing the near-surface geology. This review aims to find out how the interpreter can exploit some of the many opportunities available in surface waves recorded in land seismic data. For example, the dispersion curves associated with surface waves can be inverted to give the S-wave velocity tomogram, the common-offset gathers can reveal the presence of near-surface faults or velocity anomalies, and back-scattered surface waves can be migrated to detect the location of near-surface faults. However, the main limitation of surface waves is that they are typically sensitive to S-wave velocity variations no deeper than approximately half to one-third the dominant wavelength. For many exploration surveys, this limits the depth of investigation to be no deeper than approximately 0.5-1.0 km.

  18. Determination of ocean surface wave shape from forward scattered sound.

    Science.gov (United States)

    Walstead, Sean P; Deane, Grant B

    2016-08-01

    Forward scattered sound from the ocean surface is inverted for wave shape during three periods: low wind, mix of wind and swell, and stormy. Derived wave profiles are spatially limited to a Fresnel region at or near the nominal surface specular reflection point. In some cases, the surface wave profiles exhibit unrealistic temporal and spatial properties. To remedy this, the spatial gradient of inverted waves is constrained to a maximum slope of 0.88. Under this global constraint, only surface waves during low wind conditions result in a modeled surface multipath that accurately matches data. The power spectral density of the inverted surface wave field saturates around a frequency of 8 Hz while upward looking SONAR saturates at 1 Hz. Each shows a high frequency spectral slope of -4 that is in agreement with various empirical ocean wave spectra. The improved high frequency resolution provided by the scattering inversion indicates that it is possible to remotely gain information about high frequency components of ocean waves. The inability of the inversion algorithm to determine physically realistic surface waves in periods of high wind indicates that bubbles and out of plane scattering become important in those operating scenarios.

  19. Freely decaying weak turbulence for sea surface gravity waves.

    Science.gov (United States)

    Onorato, M; Osborne, A R; Serio, M; Resio, D; Pushkarev, A; Zakharov, V E; Brandini, C

    2002-09-30

    We study the long-time evolution of deep-water ocean surface waves in order to better understand the behavior of the nonlinear interaction processes that need to be accurately predicted in numerical models of wind-generated ocean surface waves. Of particular interest are those nonlinear interactions which are predicted by weak turbulence theory to result in a wave energy spectrum of the form of [k](-2.5). We numerically implement the primitive Euler equations for surface waves and demonstrate agreement between weak turbulence theory and the numerical results.

  20. Typhoon generated surface gravity waves measured by NOMAD-type buoys

    Science.gov (United States)

    Collins, Clarence O., III

    This study examines wind-generated ocean surface waves as measured by NOMAD-type buoys during the ONR-sponsored Impact of Typhoons on the Ocean in the Pacific (ITOP) field experiment in 2010. 1-D measurements from two new Extreme Air-Sea Interaction (EASI) NOMAD-type buoys were validated against measurements from established Air-Sea Interaction Spar (ASIS) buoys. Also, during ITOP, 3 drifting Miniature Wave Buoys, a wave measuring marine radar on the R/V Roger Revelle, and several overpasses of JASON-1 (C- and Ku-band) and -2 (Ku-band) satellite altimeters were within 100 km of either EASI buoy. These additional measurements were compared against both EASI buoys. Findings are in line with previous wave parameter inter-comparisons. A corroborated measurement of mean wave direction and direction at the peak of the spectrum from the EASI buoy is presented. Consequently, this study is the first published account of directional wave information which has been successfully gathered from a buoy with a 6 m NOMAD-type hull. This result may be applied to improve operational coverage of wave direction. In addition, details for giving a consistent estimate of sea surface elevation from buoys using strapped down accelerometers are given. This was found to be particularly important for accurate measurement of extreme waves. These technical studies established a high level of confidence in the ITOP wave measurements. Detailed frequency-direction spectra were analyzed. Structures in the wave field were described during the close passages of 4 major tropical cyclones (TC) including: severe tropical storm Dianmu, Typhoon Fanapi, Super Typhoon Megi, and Typhoon Chaba. In addition, significant swell was measured from a distant 5th TC, Typhoon Malakas. Changes in storm direction and intensity are found to have a profound impact on the wave field. Measurements of extreme waves were explored. More extreme waves were measured during TCs which coincided with times of increased wave

  1. Determination of the normalized surface height autocorrelation function of a two-dimensional randomly rough dielectric surface by the inversion of light scattering data

    CERN Document Server

    Simonsen, Ingve; Kryvi, Jacob B; Maradudin, Alexei A

    2015-01-01

    An expression is obtained on the basis of phase perturbation theory for the contribution to the mean differential reflection coefficient from the in-plane co-polarized component of the light scattered diffusely from a two-dimensional randomly rough dielectric surface when the latter is illuminated by s-polarized light. This result forms the basis for an approach to inverting experimental light scattering data to obtain the normalized surface height autocorrelation function of the surface. Several parametrized forms of this correlation function, and the minimization of a cost function with respect to the parameters defining these representations, are used in the inversion scheme. This approach also yields the rms height of the surface roughness, and the dielectric constant of the dielectric substrate if it is not known in advance. The input data used in validating this inversion consists of computer simulation results for surfaces defined by exponential and Gaussian surface height correlation functions, withou...

  2. Surface characters of internal waves generated by Rankine ovoid

    Institute of Scientific and Technical Information of China (English)

    Zhaoting Xu; Xu Chen; Izolda V. Sturova

    2006-01-01

    A linear theory on the internal waves generated in the stratified fluid with a pycnocline is presented in this paper. The internal wave fields such as the velocity fields in the stratified fluid and velocity gradient fields at the free surface are also investigated by means of the theoretical and numerical method. From the numerical results, it is shown that the internal wave generated by horizontally moving Rankine ovoid is a sort of trapped wave which propagates in a wave guide, and its waveform is a kind of Mach front-type internal wave in the pycnocline. Influence of the internal wave on the flow fields at the free surface is represented by the velocity gradient fields resulted from the internal waves generated by motion of the Rankine ovoid. At the same time, it is also shown that under the hypothesis of inviscid fluid, the synchronism between the surface velocity gradient fields at the free surface and the internal wave fields in the fluid is retained. This theory opens a possibility to study further the modulated spectrum of the Bragg waves at the free surface.

  3. Evaluation of ground stiffness parameters using continuous surface wave geophysics

    DEFF Research Database (Denmark)

    Gordon, Anne; Foged, Niels

    2000-01-01

    -small-strain stiffness of the ground Gmax. Continuous surface wave geophysics offers a quick, non-intrusive and economical way of making such measurements. This paper reviews the continuous surface wave techniques and evaluates, in engineering terms, the applicability of the method to the site investigation industry....

  4. Evaluation of ground stiffness parameters using continuous surface wave geophysics

    DEFF Research Database (Denmark)

    Gordon, Anne; Foged, Niels

    2000-01-01

    -small-strain stiffness of the ground Gmax. Continuous surface wave geophysics offers a quick, non-intrusive and economical way of making such measurements. This paper reviews the continuous surface wave techniques and evaluates, in engineering terms, the applicability of the method to the site investigation industry....

  5. The Influence of Structure Heights and Opening Angles of Micro- and Nanocones on the Macroscopic Surface Wetting Properties

    DEFF Research Database (Denmark)

    Sun, Ling; Laustsen, Milan; Mandsberg, Nikolaj

    2016-01-01

    We discuss the influence of surface structure, namely the height and opening angles of nano-and microcones on the surface wettability. We show experimental evidence that the opening angle of the cones is the critical parameter on sample superhydrophobicity, namely static contact angles and roll...... to superhydrophobic without altering surface structures. In addition, we show examples of polymer replicas (polypropylene and poly(methyl methacrylate) with different wettability, fabricated by injection moulding using templates of the silicon cone-structures....

  6. Surface acoustic wave devices for sensor applications

    Science.gov (United States)

    Bo, Liu; Xiao, Chen; Hualin, Cai; Mohammad, Mohammad Ali; Xiangguang, Tian; Luqi, Tao; Yi, Yang; Tianling, Ren

    2016-02-01

    Surface acoustic wave (SAW) devices have been widely used in different fields and will continue to be of great importance in the foreseeable future. These devices are compact, cost efficient, easy to fabricate, and have a high performance, among other advantages. SAW devices can work as filters, signal processing units, sensors and actuators. They can even work without batteries and operate under harsh environments. In this review, the operating principles of SAW sensors, including temperature sensors, pressure sensors, humidity sensors and biosensors, will be discussed. Several examples and related issues will be presented. Technological trends and future developments will also be discussed. Project supported by the National Natural Science Foundation of China (Nos. 60936002, 61025021, 61434001, 61574083), the State Key Development Program for Basic Research of China (No. 2015CB352100), the National Key Project of Science and Technology (No. 2011ZX02403-002) and the Special Fund for Agroscientific Research in the Public Interest of China (No. 201303107). M.A.M is additionally supported by the Postdoctoral Fellowship (PDF) program of the Natural Sciences and Engineering Research Council (NSERC) of Canada and the China Postdoctoral Science Foundation (CPSF).

  7. Surface Acoustic Waves to Drive Plant Transpiration

    Science.gov (United States)

    Gomez, Eliot F.; Berggren, Magnus; Simon, Daniel T.

    2017-03-01

    Emerging fields of research in electronic plants (e-plants) and agro-nanotechnology seek to create more advanced control of plants and their products. Electronic/nanotechnology plant systems strive to seamlessly monitor, harvest, or deliver chemical signals to sense or regulate plant physiology in a controlled manner. Since the plant vascular system (xylem/phloem) is the primary pathway used to transport water, nutrients, and chemical signals—as well as the primary vehicle for current e-plant and phtyo-nanotechnology work—we seek to directly control fluid transport in plants using external energy. Surface acoustic waves generated from piezoelectric substrates were directly coupled into rose leaves, thereby causing water to rapidly evaporate in a highly localized manner only at the site in contact with the actuator. From fluorescent imaging, we find that the technique reliably delivers up to 6x more water/solute to the site actuated by acoustic energy as compared to normal plant transpiration rates and 2x more than heat-assisted evaporation. The technique of increasing natural plant transpiration through acoustic energy could be used to deliver biomolecules, agrochemicals, or future electronic materials at high spatiotemporal resolution to targeted areas in the plant; providing better interaction with plant physiology or to realize more sophisticated cyborg systems.

  8. Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhen; Gao, Fei [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Zhang, Baile, E-mail: blzhang@ntu.edu.sg [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore, Singapore 637371 (Singapore)

    2016-01-25

    We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find use in the design of integrated surface-wave devices with suppressed crosstalk.

  9. Northern North Atlantic Sea Surface Height and Ocean Heat Content Variability

    Science.gov (United States)

    Hakkinen, Sirpa; Rhines, Peter; Worthen, Denise L.

    2013-01-01

    The evolution of nearly 20 years of altimetric sea surface height (SSH) is investigated to understand its association with decadal to multidecadal variability of the North Atlantic heat content. Altimetric SSH is dominated by an increase of about 14 cm in the Labrador and Irminger seas from 1993 to 2011, while the opposite has occurred over the Gulf Stream region over the same time period. During the altimeter period the observed 0-700 m ocean heat content (OHC) in the subpolar gyre mirrors the increased SSH by its dominantly positive trend. Over a longer period, 1955-2011, fluctuations in the subpolar OHC reflect Atlantic multidecadal variability (AMV) and can be attributed to advection driven by the wind stress ''gyre mode'' bringing more subtropical waters into the subpolar gyre. The extended subpolar warming evident in SSH and OHC during the altimeter period represents transition of the AMV from cold to warm phase. In addition to the dominant trend, the first empirical orthogonal function SSH time series shows an abrupt change 2009-2010 reaching a new minimum in 2010. The change coincides with the change in the meridional overturning circulation at 26.5N as observed by the RAPID (Rapid Climate Change) project, and with extreme behavior of the wind stress gyre mode and of atmospheric blocking. While the general relationship between northern warming and Atlantic meridional overturning circulation (AMOC) volume transport remains undetermined, the meridional heat and salt transport carried by AMOC's arteries are rich with decade-to-century timescale variability.

  10. The Kuroshio Transport East of Taiwan and the Sea Surface Height Anomaly from the Interior Ocean

    Institute of Scientific and Technical Information of China (English)

    LIU Wei; LIU Qinyu; JIA Yinglai

    2004-01-01

    The relationship between the Kuroshio transport to the east of Taiwan and the SSHA(Sea Surface Height Anomaly)field is studied based on the World Ocean Circulation Experiment(WOCE)PCM-1 moored current meter array observation, the satellite altimeter data from the MSLA(Map of Sea Level Anomaly)products merged with the ERS and TOPEX/POSEIDON(T/P)data sets, and the WOCE satellite-tracked drifting buoy data. It is confirmed that the Kuroshio transport across PCM-1 array highly correlates with the SSHA upstream(22°-24°, 121.75°-124°E). The SSHA is not locally generated by the developed Kuroshio meandering but is from the interior ocean and is propagating westward or northwestward. During the period from October 1992 to January 1998, two events of the northwestward propagating negative SSHA occurred, during which the SSHA merged into the Kuroshio and caused the remarkable low transport events in contrast to the normal westward propagating negative SSHA. It is also shown that the lower Kuroshio transport event would be generated in different ways. The negative anomaly in the upstream of PCM-1 array can reduce the Kuroshio transport by either offshore or onshore Kuroshio meandering. The positive anomaly, which is strong enough to detour the Kuroshio, can cause an offshore meandering and a low transport event at the PCM-1 array.

  11. Sea surface height evidence for long-term warming effects of tropical cyclones on the ocean.

    Science.gov (United States)

    Mei, Wei; Primeau, François; McWilliams, James C; Pasquero, Claudia

    2013-09-17

    Tropical cyclones have been hypothesized to influence climate by pumping heat into the ocean, but a direct measure of this warming effect is still lacking. We quantified cyclone-induced ocean warming by directly monitoring the thermal expansion of water in the wake of cyclones, using satellite-based sea surface height data that provide a unique way of tracking the changes in ocean heat content on seasonal and longer timescales. We find that the long-term effect of cyclones is to warm the ocean at a rate of 0.32 ± 0.15 PW between 1993 and 2009, i.e., ∼23 times more efficiently per unit area than the background equatorial warming, making cyclones potentially important modulators of the climate by affecting heat transport in the ocean-atmosphere system. Furthermore, our analysis reveals that the rate of warming increases with cyclone intensity. This, together with a predicted shift in the distribution of cyclones toward higher intensities as climate warms, suggests the ocean will get even warmer, possibly leading to a positive feedback.

  12. Feasibility of Using Dynamically Oscillating Surfaces to Control Tollmien-Schlichting Waves

    Science.gov (United States)

    Dell'Orso, Haley

    This work characterizes and controls Tollmien-Schlichting (T-S) waves by means of Piezoelectrically-Driven Oscillating Surface (PDOS) actuators, using Particle Image Velocimetry (PIV). A parametric study of PDOS actuator design parameters was conducted and a 0.79 mm thick rubber surface with a 12.7 mm diameter circular dimple, a cavity height of 2 mm, and a neck height of 2 mm was selected for implementation in T-S wave control over a flat plate. Two circular PDOS actuators were used to excite and control the most amplified frequency of the T-S wave on a flat plate. The actuators were placed at the mid-span of a flat plate at two streamwise locations of x/L = 0.18 and x/L = 0.28 downstream from the leading edge, where the free-stream velocity was U = 16 m/s. The upstream actuator was used to excite and phase-lock the T-S waves at an excitation frequency of ƒact = 250 Hz (corresponding to the most amplified frequency of the T-S wave, based on linear stability analysis), and the downstream PDOS was used to mitigate the T-S wave by driving it at an anti-phase with the appropriate amplitude. Time- and phase-averaged flow fields were acquired at two downstream interrogation domains. The first window of data, taken in between the two PDOS actuators, explored the effect of the excitation amplitude on the magnitude of the excited T-S waves. At the second window, located downstream of both PDOS actuators, the simultaneous activation of both actuators at an appropriate phase shift and amplitudes resulted in a significant reduction or augmentation of the T-S waves, depending on the phase shift between the two actuators.

  13. A Multiscale Nested Modeling Framework to Simulate the Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves

    Science.gov (United States)

    2015-09-30

    Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves Lian Shen St. Anthony Falls Laboratory and Department of Mechanical...on studying surface gravity wave evolution and spectrum in the presence of surface currents caused by strongly nonlinear internal solitary waves...interaction of surface and internal gravity waves in the South China Sea. We will seek answers to the following questions: 1) How does the wind-wave

  14. Impacts of climate changes on ocean surface gravity waves over the eastern Canadian shelf

    Science.gov (United States)

    Guo, Lanli; Sheng, Jinyu

    2017-05-01

    A numerical study is conducted to investigate the impact of climate changes on ocean surface gravity waves over the eastern Canadian shelf (ECS). The "business-as-usual" climate scenario known as Representative Concentration Pathway RCP8.5 is considered in this study. Changes in the ocean surface gravity waves over the study region for the period 1979-2100 are examined based on 3 hourly ocean waves simulated by the third-generation ocean wave model known as WAVEWATCHIII. The wave model is driven by surface winds and ice conditions produced by the Canadian Regional Climate Model (CanRCM4). The whole study period is divided into the present (1979-2008), near future (2021-2050) and far future (2071-2100) periods to quantify possible future changes of ocean waves over the ECS. In comparison with the present ocean wave conditions, the time-mean significant wave heights ( H s ) are expected to increase over most of the ECS in the near future and decrease over this region in the far future period. The time-means of the annual 5% largest H s are projected to increase over the ECS in both near and far future periods due mainly to the changes in surface winds. The future changes in the time-means of the annual 5% largest H s and 10-m wind speeds are projected to be twice as strong as the changes in annual means. An analysis of inverse wave ages suggests that the occurrence of wind seas is projected to increase over the southern Labrador and central Newfoundland Shelves in the near future period, and occurrence of swells is projected to increase over other areas of the ECS in both the near and far future periods.

  15. Impacts of climate changes on ocean surface gravity waves over the eastern Canadian shelf

    Science.gov (United States)

    Guo, Lanli; Sheng, Jinyu

    2017-03-01

    A numerical study is conducted to investigate the impact of climate changes on ocean surface gravity waves over the eastern Canadian shelf (ECS). The "business-as-usual" climate scenario known as Representative Concentration Pathway RCP8.5 is considered in this study. Changes in the ocean surface gravity waves over the study region for the period 1979-2100 are examined based on 3 hourly ocean waves simulated by the third-generation ocean wave model known as WAVEWATCHIII. The wave model is driven by surface winds and ice conditions produced by the Canadian Regional Climate Model (CanRCM4). The whole study period is divided into the present (1979-2008), near future (2021-2050) and far future (2071-2100) periods to quantify possible future changes of ocean waves over the ECS. In comparison with the present ocean wave conditions, the time-mean significant wave heights (H s ) are expected to increase over most of the ECS in the near future and decrease over this region in the far future period. The time-means of the annual 5% largest H s are projected to increase over the ECS in both near and far future periods due mainly to the changes in surface winds. The future changes in the time-means of the annual 5% largest H s and 10-m wind speeds are projected to be twice as strong as the changes in annual means. An analysis of inverse wave ages suggests that the occurrence of wind seas is projected to increase over the southern Labrador and central Newfoundland Shelves in the near future period, and occurrence of swells is projected to increase over other areas of the ECS in both the near and far future periods.

  16. Splitting the surface wave in metal/dielectric nanostructures

    Institute of Scientific and Technical Information of China (English)

    Zhu Song; Wu Jian

    2011-01-01

    We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain (FDTD) simulation method.The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths,thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4~5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.

  17. Direct detection of near-surface faults by migration of back-scattered surface waves

    KAUST Repository

    Yu, Han

    2014-08-05

    We show that diffraction stack migration can be used to estimate the distribution of near-surface faults. The assumption is that near-surface faults generate detectable back-scattered surface waves from impinging surface waves. The processing steps are to isolate the back-scattered surface waves, and then migrate them by diffraction migration using the surface wave velocity as the migration velocity. Instead of summing events along trial quasi-hyperbolas, surface wave migration sums events along trial quasi-linear trajectories that correspond to the moveout of back-scattered surface waves. A deconvolution filter derived from the data can be used to collapse a dispersive arrival into a non-dispersive event. Results with synthetic data and field records validate the feasibility of this method. Applying this method to USArray data or passively recorded exploration data might open new opportunities in mapping tectonic features over the extent of the array.

  18. Wave-current interaction near the Gulf Stream during the surface wave dynamics experiment

    Science.gov (United States)

    Wang, David W.; Liu, Antony K.; Peng, Chih Y.; Meindl, Eric A.

    1994-01-01

    This paper presents a case study on the wave-current interaction near the local curvature of a Gulf Stream meander. The wave data were obtained from in situ measurements by a pitch-roll discus buoy during the Surface Wave Dynamics Experiment (SWADE) conducted off Wallops Island, Virginia, from October 1990 to March 1991. Owing to the advection of the Gulf Stream by the semidiurnal tide, the discus buoy was alternately located outside and inside the Gulf Stream. The directional wave measurements from the buoy show the changes in wave direction, wave energy, and directional spreading when waves encountered the current in the Gulf Stream meanders. A wave refraction model, using the ray-tracing method with an estimated Gulf Stream velocity field and meandering condition, was used to simulate wave refraction patterns and to estimate wave parameters at relative locations corresponding to buoy measurements. The numerical simulation shows that a focusing zone of wave rays was formed near the boundary and behind the crest of a simulated Gulf Stream meander. The focusing of wave rays causes changes in wave direction, increases in wave energy, and decreases in wave directional spreading, which are in good agreement with the results from the buoy measurements.

  19. Properties of high-frequency wave power halos around active regions: an analysis of multi-height data from HMI and AIA onboard SDO

    CERN Document Server

    Rajaguru, S P; Sun, Xudong; Hayashi, K; Schunker, H

    2012-01-01

    We study properties of waves of frequencies above the photospheric acoustic cut-off of $\\approx$5.3 mHz, around four active regions, through spatial maps of their power estimated using data from Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). The wavelength channels 1600 {\\AA} and 1700 {\\AA} from AIA are now known to capture clear oscillation signals due to helioseismic p modes as well as waves propagating up through to the chromosphere. Here we study in detail, in comparison with HMI Doppler data, properties of the power maps, especially the so called 'acoustic halos' seen around active regions, as a function of wave frequencies, inclination and strength of magnetic field (derived from the vector field observations by HMI) and observation height. We infer possible signatures of (magneto-)acoustic wave refraction from the observation height dependent changes, and hence due to changing magnetic strength and geometry, in the dependences of ...

  20. Development of Surface Acoustic Wave Electronic Nose

    Directory of Open Access Journals (Sweden)

    S.K. Jha

    2010-07-01

    Full Text Available The paper proposes an effective method to design and develop surface acoustic wave (SAW sensor array-based electronic nose systems for specific target applications. The paper suggests that before undertaking full hardware development empirically through hit and trial for sensor selection, it is prudent to develop accurate sensor array simulator for generating synthetic data and optimising sensor array design and pattern recognition system. The latter aspects are most time-consuming and cost-intensive parts in the development of an electronic nose system. This is because most of the electronic sensor platforms, circuit components, and electromechanical parts are available commercially-off-the-shelve (COTS, whereas knowledge about specific polymers and data analysis software are often guarded due to commercial or strategic interests. In this study, an 11-element SAW sensor array is modelled to detect and identify trinitrotoluene (TNT and dinitrotoluene (DNT explosive vapours in the presence of toluene, benzene, di-methyl methyl phosphonate (DMMP and humidity as interferents. Additive noise sources and outliers were included in the model for data generation. The pattern recognition system consists of: (i a preprocessor based on logarithmic data scaling, dimensional autoscaling, and singular value decomposition-based denoising, (ii principal component analysis (PCA-based feature extractor, and (iii an artificial neural network (ANN classifier. The efficacy of this approach is illustrated by presenting detailed PCA analysis and classification results under varied conditions of noise and outlier, and by analysing comparative performance of four classifiers (neural network, k-nearest neighbour, naïve Bayes, and support vector machine.Defence Science Journal, 2010, 60(4, pp.364-376, DOI:http://dx.doi.org/10.14429/dsj.60.493

  1. Apertureless SNOM imaging of the surface phonon polariton waves: what do we measure?

    Science.gov (United States)

    Kazantsev, D. V.; Ryssel, H.

    2013-10-01

    The apertureless scanning near-field microscope (ASNOM) mapping of surface phonon polariton (SPP) waves being excited at the surface of the SiC polar crystal at a frequency corresponding to the lattice resonance was investigated. The wave with well-defined direction and source position, as well as a well-known propagation law, was used to calibrate the signal of an ASNOM. An experimental proof is presented showing that the signal collected by the ASNOM in such a case is proportional (as a complex number) to the local field amplitude above the surface, regardless of the tip response model. It is shown that the expression describing an ASNOM response, which is, in general case, rather complicated nonlinear function of a surface/tip dielectric constants, wavelength, tip vibration amplitude, tip shape etc., can be dramatically simplified in the case of the SPP waves mapping in a mid-IR range, due to a lucky combination of the tip and surface parameters for the case being considered. A tip vibration amplitude is much less than a running SPP wave field decay height in a normal direction. At the same time, the tip amplitude is larger than a characteristic distance at which a tip-surface electromagnetic near-field interaction plays a significant role.

  2. Study of Magnetohydrodynamic Surface Waves on Liquid Gallium

    Energy Technology Data Exchange (ETDEWEB)

    Hantao Ji; William Fox; David Pace; H.L. Rappaport

    2004-05-13

    Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak, waves are weakly damped and the real part of the dispersion is unaffected, while in the opposite limit waves are strongly damped with shortened wavelengths. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A non-invasive diagnostic accurately measures surface waves at multiple locations by reflecting an array of lasers off the surface onto a screen, which is recorded by an Intensified-CCD camera. The measured dispersion relation is consistent with the linear theory with a reduced surface tension likely due to surface oxidation. In excellent agreement with linear theory, it is observed that surface waves are damped only when a horizontal magnetic field is imposed parallel to the propagation direction. No damping is observed under a perpendicular magnetic field. The existence of strong wave damping even without magnetic field suggests the importance of the surface oxide layer. Implications to the liquid metal wall concept in fusion reactors, especially on the wave damping and a Rayleigh-Taylor instability when the Lorentz force is used to support liquid metal layer against gravity, are discussed.

  3. Sea Surface Height Determination In The Arctic Using Cryosat-2 SAR Data From Primary Peak Empirical Retrackers

    DEFF Research Database (Denmark)

    Jain, Maulik; Andersen, Ole Baltazar; Dall, Jørgen

    2015-01-01

    SAR waveforms from Cryosat-2 are processed using primary peak empirical retrackers to determine the sea surface height in the Arctic. The empirical retrackers investigated are based on the combination of the traditional OCOG (Offset Center of Gravity) and threshold methods with primary peak...

  4. Time-resolved coherent X-ray diffraction imaging of surface acoustic waves.

    Science.gov (United States)

    Nicolas, Jan-David; Reusch, Tobias; Osterhoff, Markus; Sprung, Michael; Schülein, Florian J R; Krenner, Hubert J; Wixforth, Achim; Salditt, Tim

    2014-10-01

    Time-resolved coherent X-ray diffraction experiments of standing surface acoustic waves, illuminated under grazing incidence by a nanofocused synchrotron beam, are reported. The data have been recorded in stroboscopic mode at controlled and varied phase between the acoustic frequency generator and the synchrotron bunch train. At each time delay (phase angle), the coherent far-field diffraction pattern in the small-angle regime is inverted by an iterative algorithm to yield the local instantaneous surface height profile along the optical axis. The results show that periodic nanoscale dynamics can be imaged at high temporal resolution in the range of 50 ps (pulse length).

  5. Study on the double transmission of ultrasonic waves through statistic rough surfaces

    Institute of Scientific and Technical Information of China (English)

    CHEN Ziqiang; CHEN Ligong; NI Chunzhen; WANG Yuwen

    2002-01-01

    A model evaluating the signal loss of the double transmitted acoustic beams through random rough surfaces was established based on the Fresnel approximation and phasescreen approximation. A simple analytical solution was achieved using the exponential substitution approach to remove the nonlinear integral terms. The factors that affect the signal of double transmissions from random rough surfaces were analyzed. The research results demonstrated that the signal loss is not only related to the root-mean-squire height of the roughness,but also to the distance of wave traveling in the materials. The model can be very helpful for improving the reliability of NDT (Non-Destructive Testing).

  6. Observation of Zenneck-Like Waves over a Metasurface Designed for Launching HF Radar Surface Wave

    Directory of Open Access Journals (Sweden)

    Florent Jangal

    2016-01-01

    Full Text Available Since the beginning of the 20th century a controversy has been continuously revived about the existence of the Zenneck Wave. This wave is a theoretical solution of Maxwell’s equations and might be propagated along the interface between the air and a dielectric medium. The expected weak attenuation at large distance explains the constant interest for this wave. Notably in the High Frequency band such a wave had been thought as a key point to reduce the high attenuation observed in High Frequency Surface Wave Radar. Despite many works on that topic and various experiments attempted during one century, there is still an alternation of statements between its existence and its nonexistence. We report here an experiment done during the optimisation of the transmitting antennas for Surface Wave Radars. Using an infrared method, we visualize a wave having the structure described by Zenneck above a metasurface located on a dielectric slab.

  7. An experimental study of wave coupling in gravity surface wave turbulence

    Science.gov (United States)

    Aubourg, Quentin; Sommeria, Joel; Viboud, Samuel; Mordant, Nicolas

    2016-11-01

    Weak turbulence is a theoretical framework aimed at describing wave turbulence (in the weakly nonlinear limit) i.e. a statistical state involving a large number of nonlinearly coupled waves. For gravity waves at the surface of water, it provides a phenomenology that may describe the formation of the spectrum of the ocean surface. Analytical predictions of the spectra are made based on the fact that energy transfer occurs through 4-wave coupling. By using an advanced stereoscopic imaging technique, we measure in time the deformation of the water surface. We obtain a state of wave turbulence by using two small wedge wavemakers in a 13-m diameter wavetank. We then use high order correlator (bi- and tri-coherence) in order to get evidence of the active wave coupling present in our system as used successfully for gravity-capillary wave turbulence. At odds with the weak turbulence theory we observe 3-wave interaction involving 2 quasi linear wave and a bound wave whose frequency lies on the first harmonics of the linear dispersion relation. We do not observe 4-wave coupling within the accuracy of our measurement. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement No 647018-WATU).

  8. Statistical multi-model climate projections of surface ocean waves in Europe

    Science.gov (United States)

    Perez, Jorge; Menendez, Melisa; Camus, Paula; Mendez, Fernando J.; Losada, Inigo J.

    2015-12-01

    In recent years, the impact of climate change on sea surface waves has received increasingly more attention by the climate community. Indeed, ocean waves reaching the coast play an important role in several processes concerning coastal communities, such as inundation and erosion. However, regional downscaling at the high spatial resolution necessary for coastal studies has received less attention. Here, we present a novel framework for regional wave climate projections and its application in the European region. Changes in the wave dynamics under different scenarios in the Northeast Atlantic Ocean and the Mediterranean are analyzed. The multi-model projection methodology is based on a statistical downscaling approach. The statistical relation between the predictor (atmospheric conditions) and the predictand (multivariate wave climate) is based on a weather type (WT) classification. This atmospheric classification is developed by applying the k-means clustering technique over historical offshore sea level pressure (SLP) fields. Each WT is linked to sea wave conditions from a wave hindcast. This link is developed by associating atmospheric conditions from reanalysis with multivariate local waves. This predictor-predictand relationship is applied to the daily SLP fields from global climate models (GCMs) in order to project future changes in regional wave conditions. The GCMs used in the multi-model projection are selected according to skill criteria. The application of this framework uses CMIP5-based wave climate projections in Europe. The low computational requirements of the statistical approach allow a large number of GCMs and climate change scenarios to be studied. Consistent with previous works on global wave climate projections, the estimated changes from the regional wave climate projections show a general decrease in wave heights and periods in the Atlantic Europe for the late twenty-first century. The regional projections, however, allow a more detailed

  9. Decadal variability of extreme wave height representing storm severity in the northeast Atlantic and North Sea since the foundation of the Royal Society

    Science.gov (United States)

    Santo, H.; Taylor, P. H.; Gibson, R.

    2016-09-01

    Long-term estimation of extreme wave height remains a key challenge because of the short duration of available wave data, and also because of the possible impact of climate variability on ocean waves. Here, we analyse storm-based statistics to obtain estimates of extreme wave height at locations in the northeast Atlantic and North Sea using the NORA10 wave hindcast (1958-2011), and use a 5 year sliding window to examine temporal variability. The decadal variability is correlated to the North Atlantic oscillation and other atmospheric modes, using a six-term predictor model incorporating the climate indices and their Hilbert transforms. This allows reconstruction of the historic extreme climate back to 1661, using a combination of known and proxy climate indices. Significant decadal variability primarily driven by the North Atlantic oscillation is observed, and this should be considered for the long-term survivability of offshore structures and marine renewable energy devices. The analysis on wave climate reconstruction reveals that the variation of the mean, 99th percentile and extreme wave climates over decadal time scales for locations close to the dominant storm tracks in the open North Atlantic are comparable, whereas the wave climates for the rest of the locations including the North Sea are rather different.

  10. Decadal variability of extreme wave height representing storm severity in the northeast Atlantic and North Sea since the foundation of the Royal Society.

    Science.gov (United States)

    Santo, H; Taylor, P H; Gibson, R

    2016-09-01

    Long-term estimation of extreme wave height remains a key challenge because of the short duration of available wave data, and also because of the possible impact of climate variability on ocean waves. Here, we analyse storm-based statistics to obtain estimates of extreme wave height at locations in the northeast Atlantic and North Sea using the NORA10 wave hindcast (1958-2011), and use a 5 year sliding window to examine temporal variability. The decadal variability is correlated to the North Atlantic oscillation and other atmospheric modes, using a six-term predictor model incorporating the climate indices and their Hilbert transforms. This allows reconstruction of the historic extreme climate back to 1661, using a combination of known and proxy climate indices. Significant decadal variability primarily driven by the North Atlantic oscillation is observed, and this should be considered for the long-term survivability of offshore structures and marine renewable energy devices. The analysis on wave climate reconstruction reveals that the variation of the mean, 99th percentile and extreme wave climates over decadal time scales for locations close to the dominant storm tracks in the open North Atlantic are comparable, whereas the wave climates for the rest of the locations including the North Sea are rather different.

  11. Sea Surface Height Variability and Eddy Statistical Properties in the Red Sea

    KAUST Repository

    Zhan, Peng

    2013-05-01

    Satellite sea surface height (SSH) data over 1992-2012 are analyzed to study the spatial and temporal variability of sea level in the Red Sea. Empirical orthogonal functions (EOF) analysis suggests the remarkable seasonality of SSH in the Red Sea, and a significant correlation is found between SSH variation and seasonal wind cycle. A winding-angle based eddy identification algorithm is employed to derive the mesoscale eddy information from SSH data. Totally more than 5500 eddies are detected, belonging to 2583 eddy tracks. Statistics suggest that eddies generate over the entire Red Sea, with two regions in the central basin of high eddy frequency. 76% of the detected eddies have a radius ranging from 40km to 100km, of which both intensity and absolute vorticity decrease with eddy radius. The average eddy lifespan is about 5 weeks, and eddies with longer lifespan tend to have larger radius but less intensity. Different deformation rate exists between anticyclonic eddies (AEs) and cyclonic eddies (CEs), those eddies with higher intensity appear to be less deformed and more circular. Inspection of the 84 long-lived eddies suggests the AEs tend to move a little more northward than CEs. AE generation during summer is obviously lower than that during other seasons, while CE generation is higher during spring and summer. Other features of AEs and CEs are similar with both vorticity and intensity reaching the summer peaks in August and winter peaks in January. Inter-annual variability reveals that the eddies in the Red Sea are isolated from the global event. The eddy property tendencies are different from the south and north basin, both of which exhibit a two-year cycle. Showing a correlation coefficient of -0.91, Brunt–Väisälä frequency is negatively correlated with eddy kinetic energy (EKE), which results from AE activities in the high eddy frequency region. Climatological vertical velocity shear variation is identical with EKE except in the autumn, suggesting the

  12. Surface Wave Cloak from Graded Refractive Index Nanocomposites

    Science.gov (United States)

    La Spada, L.; McManus, T. M.; Dyke, A.; Haq, S.; Zhang, L.; Cheng, Q.; Hao, Y.

    2016-07-01

    Recently, a great deal of interest has been re-emerged on the possibility to manipulate surface waves, in particular, towards the THz and optical regime. Both concepts of Transformation Optics (TO) and metamaterials have been regarded as one of key enablers for such applications in applied electromagnetics. In this paper, we experimentally demonstrate for the first time a dielectric surface wave cloak from engineered gradient index materials to illustrate the possibility of using nanocomposites to control surface wave propagation through advanced additive manufacturing. The device is designed analytically and validated through numerical simulations and measurements, showing good agreement and performance as an effective surface wave cloak. The underlying design approach has much wider applications, which span from microwave to optics for the control of surface plasmon polaritons (SPPs) and radiation of nanoantennas.

  13. Surface waves in a vertically excited circular cylindrical container

    Institute of Scientific and Technical Information of China (English)

    Jian Yong-Jun; E Xue-Quan; Zhang Jie; Meng Jun-Min

    2004-01-01

    The nonlinear free surface amplitude equation, which has been derived from the inviscid fluid by solving the potential equation of water waves with a singular perturbation theory in a vertically oscillating rigid circular cylinder,is investigated successively in the fourth-order Runge-Kutta approach with an equivalent time-step. Computational results include the evolution of the amplitude with time, the characteristics of phase plane determined by the real and imaginary parts of the amplitude, the single-mode selection rules of the surface waves in different forced frequencies,contours of free surface displacement and corresponding three-dimensional evolution of surface waves, etc. In addition,the comparison of the surface wave modes is made between theoretical calculations and experimental measurements,and the results are reasonable although there are some differences in the forced frequency.

  14. Spatial characteristics of ocean surface waves

    Science.gov (United States)

    Gemmrich, Johannes; Thomson, Jim; Rogers, W. Erick; Pleskachevsky, Andrey; Lehner, Susanne

    2016-08-01

    The spatial variability of open ocean wave fields on scales of O (10km) is assessed from four different data sources: TerraSAR-X SAR imagery, four drifting SWIFT buoys, a moored waverider buoy, and WAVEWATCH III Ⓡ model runs. Two examples from the open north-east Pacific, comprising of a pure wind sea and a mixed sea with swell, are given. Wave parameters attained from observations have a natural variability, which decreases with increasing record length or acquisition area. The retrieval of dominant wave scales from point observations and model output are inherently different to dominant scales retrieved from spatial observations. This can lead to significant differences in the dominant steepness associated with a given wave field. These uncertainties have to be taken into account when models are assessed against observations or when new wave retrieval algorithms from spatial or temporal data are tested. However, there is evidence of abrupt changes in wave field characteristics that are larger than the expected methodological uncertainties.

  15. Surface Waves in the paritally ionized solar plasma slab

    CERN Document Server

    Pandey, B P

    2013-01-01

    The properties of surface waves in the partially ionized, incompressible magnetized plasma slab are investigated in the present work. The waves are affected by the non ideal MHD effects which causes the finite drift of the magnetic field in the medium. When the finite drift of the magnetic field is ignored, the characteristics of the wave propagation in the partially ionized plasma fluid is similar to the ideal MHD except now the propagation properties depend on the fractional ionization of the medium. In the presence of Hall diffusion, the propagation of the sausage and kink surface waves depends on the level of fractional ionization of the medium. When both the Hall and Pedersen diffusion are present in the medium, the waves undergoes damping. For typical solar parameters, waves may damp over few minutes.

  16. Experimental study of three-wave interactions among capillary-gravity surface waves

    CERN Document Server

    Haudin, Florence; Deike, Luc; Jamin, Timothée; Falcon, Eric; Berhanu, Michael

    2016-01-01

    In propagating wave systems, three or four-wave resonant interactions constitute a classical non-linear mechanism exchanging energy between the different scales. Here we investigate three-wave interactions for gravity-capillary surface waves in a closed laboratory tank. We generate two crossing wave-trains and we study their interaction. Using two optical methods, a local one (Laser Doppler Vibrometry) and a spatio-temporal one (Diffusive Light Photography), a third wave of smaller amplitude is detected, verifying the three-wave resonance conditions in frequency and in wavenumber. Furthermore, by focusing on the stationary regime and by taking into account viscous dissipation, we directly estimate the growth rate of the resonant mode. The latter is then compared to the predictions of the weakly non-linear triadic resonance interaction theory. The obtained results confirm qualitatively and extend previous experimental results obtained only for collinear wave-trains. Finally, we discuss the relevance of three-w...

  17. Comparison of gridded multi-mission and along-track mono-mission satellite altimetry wave heights with in situ near-shore buoy data.

    Digital Repository Service at National Institute of Oceanography (India)

    Shanas, P.R.; SanilKumar, V.; Hithin, N.K.

    The applicability of altimeter data for the coastal region is examined by comparing the gridded multi-mission and along-track mono-mission significant wave height (SWH) data with the in situ buoy measurements at four stations off the east and west...

  18. Ray-map migration of transmitted surface waves

    KAUST Repository

    Li, Jing

    2016-08-25

    Near-surface normal faults can sometimes separate two distinct zones of velocity heterogeneity, where the medium on one side of the fault has a faster velocity than on the other side. Therefore, the slope of surface-wave arrivals in a common-shot gather should abruptly change near the surface projection of the fault. We present ray-map imaging method that migrates transmitted surface waves to the fault plane, and therefore it roughly estimates the orientation, depth, and location of the near-surface fault. The main benefits of this method are that it is computationally inexpensive and robust in the presence of noise.

  19. Enhanced Sensitive Love Wave Surface Acoustic Wave Sensor Designed for Immunoassay Formats

    OpenAIRE

    Mihaela Puiu; Ana-Maria Gurban; Lucian Rotariu; Simona Brajnicov; Cristian Viespe; Camelia Bala

    2015-01-01

    We report a Love wave surface acoustic wave (LW-SAW) immunosensor designed for the detection of high molecular weight targets in liquid samples, amenable also for low molecular targets in surface competition assays. We implemented a label-free interaction protocol similar to other surface plasmon resonance bioassays having the advantage of requiring reduced time analysis. The fabricated LW-SAW sensor supports the detection of the target in the nanomolar range, and can be ultimately incorporat...

  20. Horizon effects with surface waves on moving water

    CERN Document Server

    Rousseaux, Germain; Mathis, Christian; Coullet, Pierre; Philbin, Thomas G; Leonhardt, Ulf

    2010-01-01

    Surface waves on a stationary flow of water are considered, in a linear model that includes the surface tension of the fluid. The resulting gravity-capillary waves experience a rich array of horizon effects when propagating against the flow. In some cases three horizons (points where the group velocity of the wave reverses) exist for waves with a single laboratory frequency. Some of these effects are familiar in fluid mechanics under the name of wave blocking, but other aspects, in particular waves with negative co-moving frequency and the Hawking effect, were overlooked until surface waves were investigated as examples of analogue gravity [R. Schuetzhold and W. G. Unruh W G, Phys. Rev. D 66 (2002) 044019]. A comprehensive presentation of the various horizon effects for gravity-capillary waves is given, with emphasis on the deep water/long wavelength case kh>>1 where many analytical results can be derived. A similarity of the state space of the waves to that of a thermodynamic system is pointed out.

  1. Numerical simulation of floating bodies in extreme free surface waves

    Directory of Open Access Journals (Sweden)

    Z. Z. Hu

    2011-02-01

    Full Text Available In this paper, we use the in-house Computational Fluid Dynamics (CFD flow code AMAZON-SC as a numerical wave tank (NWT to study wave loading on a wave energy converter (WEC device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water. The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.

  2. Numerical simulation of floating bodies in extreme free surface waves

    Science.gov (United States)

    Hu, Z. Z.; Causon, D. M.; Mingham, C. G.; Qian, L.

    2011-02-01

    In this paper, we use the in-house Computational Fluid Dynamics (CFD) flow code AMAZON-SC as a numerical wave tank (NWT) to study wave loading on a wave energy converter (WEC) device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water). The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.

  3. Interpretation of nonlinearity in wind generated ocean surface waves

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    This study attempts to resolve a mix-up between a physical process and its mathematical interpretation in the context of wind waves on ocean surface. Wind generated wave systems, are conventionally interpreted as a result of interaction of a number...

  4. Palladium nanoparticle-based surface acoustic wave hydrogen sensor.

    Science.gov (United States)

    Sil, Devika; Hines, Jacqueline; Udeoyo, Uduak; Borguet, Eric

    2015-03-18

    Palladium (Pd) nanoparticles (5-20 nm) are used as the sensing layer on surface acoustic wave (SAW) devices for detecting H2. The interaction with hydrogen modifies the conductivity of the Pd nanoparticle film, producing measurable changes in acoustic wave propagation, which allows for the detection of this explosive gas. The nanoparticle-based SAW sensor responds rapidly and reversibly at room temperature.

  5. Stokesian swimming of a sphere by radial helical surface wave

    CERN Document Server

    Felderhof, B U

    2016-01-01

    The swimming of a sphere by means of radial helical surface waves is studied on the basis of the Stokes equations. Explicit expressions are derived for the matrices characterizing the mean translational and rotational swimming velocities and the mean rate of dissipation to second order in the wave amplitude.

  6. Comments on ‘Temporal significant wave height estimation from wind speed by perceptron Kalman filtering’ by A. Altunkaynak and M. Ozger, Ocean Engineering, Vol. 31(10); 2004,1245-1255

    Digital Repository Service at National Institute of Oceanography (India)

    Mandal, S.

    The significant wave heights and periods are conventionally forecasted from the wind information on the basis of the wind–wave relationship. However, the error may become large due to many uncertainties in the wind generation prediction and wind...

  7. Quantifying changes in land-surface height in bioenergy palm oil plantations (Sumatra) using InSAR time series.

    Science.gov (United States)

    Zhou, Zhiwei; Waldron, Susan; Li, Zhenhong

    2013-04-01

    Tropical peatlands in Southeast Asia cover ~ 439,238 km sq. and represent ~77 % of global tropical peatland carbon stores and ~11 % of global peatland area. These landscapes are substantial C stores accounting for ~17-19 % of the global peat C pool (Page et al., 2010). Within southeast Asia, Indonesian peatlands hold most C (57.4 Pg, 65 %), followed by Malaysia (9.1 Pg, 10 %). In recent decades the drive to use these soils for agriculture and often the palm oil biogenergy crop, has driven fire-clearing, deforestation and drainage of these carbon landscapes. The drainage can lead to respiration of the soil carbon store and subsidence of the peatland (Hooijer et al., 2012), reducing their strength as a current C store and their capacity for future soil C storage. Using field-based surveying to monitor changes in the past peatland surface height, and over the large areas typical of commercial agricultural palm oil plantations, is challenging such that measurements are more likely to describe a small area and be only a snapshot in time. Upscaling and understanding the rate of change in surface height through time may be overcome using remote sensing approaches. Here we present data on the change in peatland surface height in Indonesia palm oil plantations, detected using the Interferometry Synthetic Aperture Radar (InSAR) Small BAseline Set (SBAS) approach (Berardino et al., 2002). Using data from July 2007 to January 2011, we have generated a map of the rate of change of mean height, and time series of change in surface height for several plantation areas. To do this we used two independent ALOS L-band tracks SAR images, as there is a lack of ground data for validation, coherence in output provides confidence the results are representative. Our analysis to date shows that in drained and planted palm oil areas: 1) the rate of change in surface height (decrease) can vary; 2) the decrease in surface height can be up to 5 cm/year; 3) the largest decrease in surface height

  8. Oil slicks on water surface: Breakup, coalescence, and droplet formation under breaking waves.

    Science.gov (United States)

    Nissanka, Indrajith D; Yapa, Poojitha D

    2017-01-15

    The ability to calculate the oil droplet size distribution (DSD) and its dynamic behavior in the water column is important in oil spill modeling. Breaking waves disperse oil from a surface slick into the water column as droplets of varying sizes. Oil droplets undergo further breakup and coalescence in the water column due to the turbulence. Available models simulate oil DSD based on empirical/equilibrium equations. However, the oil DSD evolution due to subsequent droplet breakup and coalescence in the water column can be best represented by a dynamic population model. This paper develops a phenomenological model to calculate the oil DSD in wave breaking conditions and ocean turbulence and is based on droplet breakup and coalescence. Its results are compared with data from laboratory experiments that include different oil types, different weathering times, and different breaking wave heights. The model comparisons showed a good agreement with experimental data.

  9. Scaling observations of surface waves in the Beaufort Sea

    Directory of Open Access Journals (Sweden)

    Madison Smith

    2016-04-01

    Full Text Available Abstract The rapidly changing Arctic sea ice cover affects surface wave growth across all scales. Here, in situ measurements of waves, observed from freely-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 the wind duration was sufficient for the conditions to be considered stationary. The scaling of wave energy and frequency with open water distance demonstrated the indirect effects of ice cover on regional wave evolution. Waves in partial ice cover could be similarly categorized as distance-limited by applying the same open water scaling to determine an ‘effective fetch’. The process of local wave generation in ice appeared to be a strong function of the ice concentration, wherein the ice cover severely reduces the effective fetch. The wave field in the Beaufort Sea is thus a function of the sea ice both locally, where wave growth primarily occurs in the open water between floes, and regionally, where the ice edge may provide a more classic fetch limitation. Observations of waves in recent years may be indicative of an emerging trend in the Arctic Ocean, where we will observe increasing wave energy with decreasing sea ice extent.

  10. Wave Generated by the NACA4412 Hydrofoil near Free Surface

    Directory of Open Access Journals (Sweden)

    Hassan Ghassemi

    2013-01-01

    Full Text Available The generation of wave due to moving hydrofoil in steady streams close to a free surface is presented. The potential-based boundary element method is employed to the NACA4412 hydrofoil with linearized dynamic and kinematic boundary conditions on the free surface. The perturbation velocity potential is calculated using the Green formulation and Kutta condition. The numerical results of waves generated by the hydrofoil are presented and discussed at various Froude numbers and immersion depths.

  11. Anomalous Surface Wave Launching by Handedness Phase Control

    KAUST Repository

    Zhang, Xueqian

    2015-10-09

    Anomalous launch of a surface wave with different handedness phase control is achieved in a terahertz metasurface based on phase discontinuities. The polarity of the phase profile of the surface waves is found to be strongly correlated to the polarization handedness, promising polarization-controllable wavefront shaping, polarization sensing, and environmental refractive-index sensing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Estimating propagation velocity through a surface acoustic wave sensor

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wenyuan (Oakdale, MN); Huizinga, John S. (Dellwood, MN)

    2010-03-16

    Techniques are described for estimating the propagation velocity through a surface acoustic wave sensor. In particular, techniques which measure and exploit a proper segment of phase frequency response of the surface acoustic wave sensor are described for use as a basis of bacterial detection by the sensor. As described, use of velocity estimation based on a proper segment of phase frequency response has advantages over conventional techniques that use phase shift as the basis for detection.

  13. Estimation of Sea Surface Wave Spectra Using Acoustic Tomography.

    Science.gov (United States)

    1987-09-01

    Holister Dis speciael Dean of Graduate Studiesj ESTIMATION OF SEA SURFACE WAVE SPECTRA USING ACOUSTIC TOMOGRAPHY by James Henry Miller B.S. Electrical...James Henry Miller 1987 The author hereby prants to MIT permission to reproduce and distribute copies of this thesis in whole or in part. Signature of...ESTIMATION OF SEA SURFACE WAVE SPECTRA USING ACOUSTIC TOMOGRAPHY by James Henry Miller Submitted in partial fulfillment of the requirements for the

  14. Modulation of cavity-polaritons by surface acoustic waves

    DEFF Research Database (Denmark)

    de Lima, M. M.; Poel, Mike van der; Hey, R.;

    2006-01-01

    We modulate cavity-polaritons using surface acoustic waves. The corresponding formation of a mini-Brillouin zone and band folding of the polariton dispersion is demonstrated for the first time. Results are in good agreement with model calculations.......We modulate cavity-polaritons using surface acoustic waves. The corresponding formation of a mini-Brillouin zone and band folding of the polariton dispersion is demonstrated for the first time. Results are in good agreement with model calculations....

  15. Visualization of Surface Acoustic Waves in Thin Liquid Films

    OpenAIRE

    Rambach, R. W.; Taiber, J.; Scheck, C. M. L.; Meyer, C.; Reboud, J.; Cooper, Jonathan M.; Franke, T.

    2016-01-01

    We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with anWe demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfl...

  16. Estimating propagation velocity through a surface acoustic wave sensor

    Science.gov (United States)

    Xu, Wenyuan; Huizinga, John S.

    2010-03-16

    Techniques are described for estimating the propagation velocity through a surface acoustic wave sensor. In particular, techniques which measure and exploit a proper segment of phase frequency response of the surface acoustic wave sensor are described for use as a basis of bacterial detection by the sensor. As described, use of velocity estimation based on a proper segment of phase frequency response has advantages over conventional techniques that use phase shift as the basis for detection.

  17. Beam interactions with surface waves and higher-order modes in oversized backward wave oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Kazuo; Kojima, Akihiko; Kawabe, Fumiaki; Yambe, Kiyoyuki [Niigata University, Niigata (Japan); Amin, Ruhul [Islamic University of Technology, Gazipur (Bangladesh)

    2014-10-15

    Beam interactions with surface waves and higher-order modes in an oversized backward wave oscillator (BWO) are studied. In addition to the well-known Cherenkov interaction, the slow cyclotron interaction occurs due to transverse perturbations of the electron beam. The Cherenkov interaction dominates the slow cyclotron interaction. Growth rates of both the interactions for the higher order modes are small compared with those for the surface-wave modes in an oversized BWO. The coaxial slow-wave structure exhibits a reduced number of higher-order modes, which consequently reduces the mode competition problem and improves beam interactions with higher order modes. For higher values of beam currents, the slow cyclotron wave grows at a faster rate than the Cherenkov waves.

  18. Energy budget of surface waves in the global ocean

    Institute of Scientific and Technical Information of China (English)

    TENG Yong; YANG Yongzeng; QIAO Fangli; LU Jing; YIN Xunqiang

    2009-01-01

    Mechanical energy input from atmosphere and losses from wave-breaking dissipation of sea surface waves are estimated by a direct scheme. This scheme is based on the integration in the wavenumber space of the wind input and breaking dissipation source functions of the MASNUM wave model.The global amount of wind energy input, averaged in 2005, is about 57 TW, and the wave-breaking dissipation summed in deep-water is about 33 TW, over a half of the wind energy input. The residual may be dissipated by beach processes. Global distributions of the energy input and breaking dissipation concentrate in the westerlies of the Southern Hemisphere.

  19. The Surface Wave Scattering-Microwave Scanner (SWS-MS)

    Science.gov (United States)

    Geffrin, Jean-Michel; Chamtouri, Maha; Merchiers, Olivier; Tortel, Hervé; Litman, Amélie; Bailly, Jean-Sébastien; Lacroix, Bernard; Francoeur, Mathieu; Vaillon, Rodolphe

    2016-01-01

    The Surface Wave Scattering-Microwave Scanner (SWS-MS) is a device that allows the measurement of the electromagnetic fields scattered by objects totally or partially submerged in surface waves. No probe is used to illuminate the sample, nor to guide or scatter the local evanescent waves. Surface waves are generated by total internal reflection and the amplitude and phase of the fields scattered by the samples are measured directly, both in the far-field and the near-field regions. The device's principles and their practical implementation are described in details. The surface wave generator is assessed by measuring the spatial distribution of the electric field above the surface. Drift correction and the calibration method for far-field measurements are explained. Comparison of both far-field and near-field measurements against simulation data shows that the device provides accurate results. This work suggests that the SWS-MS can be used for producing experimental reference data, for supporting a better understanding of surface wave scattering, for assisting in the design of near-field optical or infrared systems thanks to the scale invariance rule in electrodynamics, and for performing nondestructive control of defects in materials.

  20. Polarization controlled directional propagation of Bloch surface wave.

    Science.gov (United States)

    Kovalevich, Tatiana; Boyer, Philippe; Suarez, Miguel; Salut, Roland; Kim, Myun-Sik; Herzig, Hans Peter; Bernal, Maria-Pilar; Grosjean, Thierry

    2017-03-06

    Bloch surface waves (BSWs) are recently developing alternative to surface plasmon polaritons (SPPs). Due to dramatically enhanced propagation distance and strong field confinement these surface states can be successfully used in on-chip all-optical integrated devices of increased complexity. In this work we propose a highly miniaturized grating based BSW coupler which is gathering launching and directional switching functionalities in a single element. This device allows to control with polarization the propagation direction of Bloch surface waves at subwavelength scale, thus impacting a large panel of domains such as optical circuitry, function design, quantum optics, etc.

  1. Acoustomicrofluidic application of quasi-shear surface waves.

    Science.gov (United States)

    Darinskii, A N; Weihnacht, M; Schmidt, H

    2017-02-20

    The paper analyzes the possibility of using predominantly boundary polarized surface acoustic waves for actuating fluidic effects in microchannels fabricated inside containers made of PDMS. The aim is to remove a shortcoming peculiar to conventionally utilized predominantly vertically polarized waves. Such waves strongly attenuate while they propagate under container side walls because of the leakage into them. Due to a specific feature of PDMS - extremely small shear elastic modulus - losses of boundary polarized modes should be far smaller. The amplitude of vertical mechanical displacements can be increased right inside the channel owing to the scattering of acoustic fields. As an example, the predominantly vertically polarized surface wave on 128YX LiNbO3 is compared with the quasi-shear leaky wave on 64YX LiNbO3. Our computations predict that, given the electric power supplied to the launching transducer, the quasi-shear wave will drive the fluid more efficiently than the surface wave on 128YX LiNbO3 when the container wall thickness is larger than 25-30 wavelengths, if there are no additional scatterers inside the channel. In the presence of a scatterer, such as a thin gold strip, the quasi-shear wave can be more efficient when the wall thickness exceeds 10-15 wavelengths.

  2. Steep waves in free-surface flow past narrow topography

    Science.gov (United States)

    Wade, Stephen L.; Binder, Benjamin J.; Mattner, Trent W.; Denier, James P.

    2017-06-01

    In this work, we compute steep forced solitary wave solutions for the problem of free-surface flow over a localised topographic disturbance in an otherwise flat horizontal channel bottom. A single forced solitary wave and a double-crested forced solitary wave solution are shown to exist, both of which approach the Stokes limiting configuration of an included angle of 12 0° and a stagnation point at the wave crests. The solution space for the topographically forced problem is compared to that found in Wade et al. ["On the free-surface flow of very steep forced solitary waves," J. Fluid Mech. 739, 1-21 (2014)], who considered forcing due to a localised distribution of pressure applied to the free surface. The main feature that differentiates the two types of forcing is an additional solution that exists in the pressure-forced problem, a steep wave with a cusp at a single wave crest. Our numerical results suggest that this cusped-wave solution does not exist in the topographically forced problem.

  3. Surface plasma waves over bismuth–vacuum interface

    Indian Academy of Sciences (India)

    Ashim P Jain; J Parashar

    2003-09-01

    A surface plasma wave (SPW) over bismuth–vacuum interface has a signature of mass anisotropy of free electrons. For SPW propagation along the trigonal axis there is no birefringence. The frequency cutoff of SPW cutoff=$_{p}/\\sqrt{2(_{L}+)}$ lies in the far infrared region and can be accessed using free electron laser. The damping rate of waves at low temperatures is low. The surface plasma wave may be excited by an electron beam of current ∼ 100 mA propagating parallel to the interface in its close proximity.

  4. Some aspects of dispersive horizons: lessons from surface waves

    CERN Document Server

    Chaline, J; Maïssa, P; Rousseaux, G

    2012-01-01

    Hydrodynamic surface waves propagating on a moving background flow experience an effective curved space-time. We discuss experiments with gravity waves and capillary-gravity waves in which we study hydrodynamic black/white-hole horizons and the possibility of penetrating across them. Such possibility of penetration is due to the interaction with an additional "blue" horizon, which results from the inclusion of surface tension in the low-frequency gravity-wave theory. This interaction leads to a dispersive cusp beyond which both horizons completely disappear. We speculate the appearance of high-frequency "superluminal" corrections to be a universal characteristic of analogue gravity systems, and discuss their relevance for the trans-Planckian problem. We also discuss the role of Airy interference in hybridising the incoming waves with the flowing background (the effective spacetime) and blurring the position of the black/white-hole horizon.

  5. High-frequency shear-horizontal surface acoustic wave sensor

    Science.gov (United States)

    Branch, Darren W

    2013-05-07

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  6. Estimation of near-surface shear-wave velocity by inversion of Rayleigh waves

    Science.gov (United States)

    Xia, J.; Miller, R.D.; Park, C.B.

    1999-01-01

    The shear-wave (S-wave) velocity of near-surface materials (soil, rocks, pavement) and its effect on seismic-wave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh-wave phase velocity of a layered-earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion-curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high-frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the weighted equation proved very effective in the high-frequency range when using the Levenberg-Marquardt and singular-value decomposition techniques. Convergence of the weighted solution is guaranteed through selection of the damping factor using the Levenberg-Marquardt method. Synthetic examples demonstrated calculation efficiency and stability of inverse procedures. We verify our method using borehole S-wave velocity measurements.Iterative solutions to the weighted equation by the Levenberg-Marquardt and singular-value decomposition techniques are derived to estimate near-surface shear-wave velocity. Synthetic and real examples demonstrate the calculation efficiency and stability of the inverse procedure. The inverse results of the real example are verified by borehole S-wave velocity measurements.

  7. Terahertz-wave generation by surface-emitted four-wave mixing in optical fiber

    Institute of Scientific and Technical Information of China (English)

    Ping Zhou; Dianyuan Fan

    2011-01-01

    We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional singlemode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range.Surface-emitted geometry is employed to decrease absorption loss.A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory.This is a promising way for realizing a reasonable narrow-band terahert-wave source.%@@ We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional singlemode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range.Surface-emitted geometry is employed to decrease absorption loss.A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory.This is a promising way for realizing a reasonable narrow-band terahertz-wave source.

  8. Reconstruction of the sea surface elevation from the analysis of the data collected by a wave radar system

    Science.gov (United States)

    Ludeno, Giovanni; Soldovieri, Francesco; Serafino, Francesco; Lugni, Claudio; Fucile, Fabio; Bulian, Gabriele

    2016-04-01

    X-band radar system is able to provide information about direction and intensity of the sea surface currents and dominant waves in a range of few kilometers from the observation point (up to 3 nautical miles). This capability, together with their flexibility and low cost, makes these devices useful tools for the sea monitoring either coastal or off-shore area. The data collected from wave radar system can be analyzed by using the inversion strategy presented in [1,2] to obtain the estimation of the following sea parameters: peak wave direction; peak period; peak wavelength; significant wave height; sea surface current and bathymetry. The estimation of the significant wave height represents a limitation of the wave radar system because of the radar backscatter is not directly related to the sea surface elevation. In fact, in the last period, substantial research has been carried out to estimate significant wave height from radar images either with or without calibration using in-situ measurements. In this work, we will present two alternative approaches for the reconstruction of the sea surface elevation from wave radar images. In particular, the first approach is based on the basis of an approximated version of the modulation transfer function (MTF) tuned from a series of numerical simulation, following the line of[3]. The second approach is based on the inversion of radar images using a direct regularised least square technique. Assuming a linearised model for the tilt modulation, the sea elevation has been reconstructed as a least square fitting of the radar imaging data[4]. References [1]F. Serafino, C. Lugni, and F. Soldovieri, "A novel strategy for the surface current determination from marine X-band radar data," IEEE Geosci.Remote Sens. Lett., vol. 7, no. 2, pp. 231-235, Apr. 2010. [2]Ludeno, G., Brandini, C., Lugni, C., Arturi, D., Natale, A., Soldovieri, F., Serafino, F. (2014). Remocean System for the Detection of the Reflected Waves from the Costa

  9. Omnidirectional surface wave cloak using an isotropic homogeneous dielectric coating

    Science.gov (United States)

    Mitchell-Thomas, R. C.; Quevedo-Teruel, O.; Sambles, J. R.; Hibbins, A. P.

    2016-08-01

    The field of transformation optics owes a lot of its fame to the concept of cloaking. While some experimental progress has been made towards free-space cloaking in three dimensions, the material properties required are inherently extremely difficult to achieve. The approximations that then have to be made to allow fabrication produce unsatisfactory device performance. In contrast, when surface wave systems are the focus, it has been shown that a route distinct from those used to design free-space cloaks can be taken. This results in very simple solutions that take advantage of the ability to incorporate surface curvature. Here, we provide a demonstration in the microwave regime of cloaking a bump in a surface. The distortion of the shape of the surface wave fronts due to the curvature is corrected with a suitable refractive index profile. The surface wave cloak is fabricated from a metallic backed homogeneous dielectric waveguide of varying thickness, and exhibits omnidirectional operation.

  10. Empirical Results of a Surface-Level GNSS-R Experiment in a Wave Channel

    Directory of Open Access Journals (Sweden)

    Hugo Carreno-Luengo

    2015-06-01

    Full Text Available The scattering of GNSS signals over a water surface is studied when the receiver is at a low height, as in GNSS-R coastal altimetry. The precise determination of the local sea level and wave state from the coast will provide useful altimetry and wave information as “dry” tide and wave gauges. An experiment has been conducted at the Canal d'Investigació i Experimentació Marítima (CIEM wave channel for two simulated “sea” states. The GNSS-reflectometer used is the P(Y and C/A ReflectOmeter (PYCARO instrument, a closed-loop receiver with delay and Doppler tracking loops that uses the conventional GNSS-R technique for the GPS C/A code. After retracking of the scattered GPS signals, the coherent and incoherent components have been studied. To reproduce the transmitted GPS signals indoors, a Rohde and Schwarz signal generator is used. It is found that, despite the ratio of the coherent and incoherent components being ~1, the coherent component is strong enough that it can be tracked. The coherent component comes from clusters of points on the surface that approximately satisfy the specular reflection conditions (“roughed facet”. The Pearson’s linear correlation coefficients of the derived “sea” surface height with the wave gauge data are: 0.78, 0.85 and 0.81 for a SWH = 36 cm and 0.34, 0.74, and 0.72 for a SWH = 64 cm, respectively, for transmitter elevation angles of = 60°, 75° and 86°, respectively. Finally, the rms phase of the received signal before the retracking processing is used to estimate the effective rms surface height of the ‘facets’, where the waves get scattered. It is found to be between 2.5- and 4.1-times smaller than the theoretical values corresponding to the half of the coherent reflectivity decaying factor.

  11. Study on the Detectability of the Sky-Surface Wave Hybrid Radar

    Directory of Open Access Journals (Sweden)

    Hou Chengyu

    2014-01-01

    Full Text Available Working in the HF (high-frequency band and the transmitter and receiver locating separately, the sky-surface wave hybrid radar both has the capabilities of the OTHR (over-the-horizon radar and the advantage of the bistatic radar. As the electromagnetic wave will be disturbed by the ionosphere, interfered by the sea clutter and attenuated by the sea surface, the detectability of this radar system is more complex. So, in this paper, we will discuss the problem detailedly. First of all, the radar equation is deduced based on the propagation of the electromagnetic wave. Then, how to calculate the effect of the ionosphere and the propagation loss is discussed. And an example based on the radar equation is given. At last, the ambiguity function is used to analyze the range and velocity resolution. From the result, we find that the resolution has relation with the location of the target and the height of reflection point of the ionosphere. But compared with the location, the effect of the ionospheric height can be ignored.

  12. Surface-wave potential for triggering tectonic (nonvolcanic) tremor

    Science.gov (United States)

    Hill, D.P.

    2010-01-01

    Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle is anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45?? incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia mega-thrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction, ????? 0.2). However, documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, is associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (?? ~ 0.6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.

  13. Research into surface wave phenomena in sedimentary basins

    Science.gov (United States)

    Wojcik, G. L.; Isenberg, J.; Ma, F.; Richardson, E.

    1981-12-01

    This study is a continuation of an engineering seismology research effort prompted by the sensitivity of guidance sets in Minuteman Wing V to distant earthquakes. An earlier report considers the probable cause of anomalous patterns of seismic alarms triggered by two North American earthquakes. This report extends the previous study by examining the propagation of surface waves from the 1975 Pocatello Valley, Idaho earthquake sequence across Wyoming to Wing V. In addition, the more general question of surface wave phenomena in sedimentary basins is addressed, particularly the effect of laterally inhomogeneous (dipping) basin-bedrock interfaces. Findings indicate that fundamental and first overtone surface waves are significantly modified by the travel path. In contrast, higher modes are relatively unchanged by the travel path, and affect Wing V in much the same way as body waves considered in the previous study.

  14. Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements

    Science.gov (United States)

    Xia, J.; Miller, R.D.; Park, C.B.; Hunter, J.A.; Harris, J.B.; Ivanov, J.

    2002-01-01

    Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated Vs and borehole measured Vs in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived Vs values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis. ?? 2002 Elsevier Science Ltd. All rights reserved.

  15. Horizon effects for surface waves in wave channels and circular jumps

    CERN Document Server

    Jannes, Gil; Chaline, Jennifer; Maïssa, Philippe; Mathis, Christian; Rousseaux, Germain

    2011-01-01

    Surface waves in classical fluids experience a rich array of black/white hole horizon effects. The dispersion relation depends on the characteristics of the fluid (in our case, water and silicon oil) as well as on the fluid depth and the wavelength regime. In some cases, it can be tuned to obtain a relativistic regime plus high-frequency dispersive effects. We discuss two types of ongoing analogue white-hole experiments: deep water waves propagating against a counter-current in a wave channel and shallow waves on a circular hydraulic jump.

  16. Investigation into Mass Loading Sensitivity of Sezawa Wave Mode-Based Surface Acoustic Wave Sensors

    OpenAIRE

    N. Ramakrishnan; Parthiban, R.; Sawal Hamid Md Ali; Md. Shabiul Islam; Ajay Achath Mohanan

    2013-01-01

    In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW) device is investigated through finite element method (FEM) simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered SAW resonator is considered for the simulation study. Initially the occurrence of Sezawa wave mode and displacement amplitude of the Rayleigh and Sezawa wave mode is studied for lower ZnO film thickness. Further, a thin film...

  17. Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

    Directory of Open Access Journals (Sweden)

    W. Choi

    2011-07-01

    Full Text Available The atmospheric boundary layer (ABL height (zi over complex, forested terrain is estimated based on the power spectra and the integral length scale of cross-stream winds obtained from a three-axis sonic anemometer during the two summers of the BEARPEX (Biosphere Effects on Aerosol and Photochemistry Experiment. The zi values estimated with this technique show very good agreement with observations obtained from balloon tether sondes (2007 and rawinsondes (2009 under unstable conditions (z/L < 0 at the coniferous forest in the California Sierra Nevada. On the other hand, the low frequency behavior of the streamwise upslope winds did not exhibit significant variations and was therefore not useful in predicting boundary layer height. The behavior of the nocturnal boundary layer height (h with respect to the power spectra of the v-wind component and temperature under stable conditions (z/L > 0 is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007, although it was observed to only vary from 60–80 m during the 2009 experiment in which it was measured. Finally, significant directional wind shear was observed during both day and night soundings. The winds were found to be consistently backing from the prevailing west-southwesterlies within the ABL (the anabatic cross-valley circulation to southerlies in a layer ~1–2 km thick just above the ABL before veering to the prevailing westerlies further aloft. This shear pattern is shown to be consistent with the forcing of a thermal wind driven by the regional temperature gradient directed east-southeast in the lower troposphere.

  18. Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

    Directory of Open Access Journals (Sweden)

    W. Choi

    2010-11-01

    Full Text Available In this study the atmospheric boundary layer (ABL height (zi over complex, forested terrain is estimated based on the power spectra and the integral length scale of horizontal winds obtained from a three-axis sonic anemometer during the BEARPEX (Biosphere Effects on Aerosol and Photochemistry Experiment. The zi values estimated with this technique showed very good agreement with observations obtained from balloon tether sonde (2007 and rawinsonde (2009 measurements under unstable conditions (z/L < 0 at the coniferous forest in the California Sierra Nevada. The behavior of the nocturnal boundary layer height (h and power spectra of lateral winds and temperature under stable conditions (z/L > 0 is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007, although it was observed to only vary from 60–80 m during the experiment. Finally, significant directional wind shear was observed during both day and night with winds backing from the prevailing west-southwesterlies in the ABL (anabatic cross-valley circulation to consistent southerlies in a layer ~1 km thick just above the ABL before veering to the prevailing westerlies further aloft. We show that this is consistent with the forcing of a thermal wind driven by the regional temperature gradient directed due east in the lower troposphere.

  19. A surface wave elastography technique for measuring tissue viscoelastic properties.

    Science.gov (United States)

    Zhang, Xiaoming

    2017-04-01

    A surface wave elastography method is proposed to study the viscoelastic properties of skin by measuring the surface wave speed and attenuation on the skin. Experiments were carried out on porcine skin tissues. The surface wave speed is measured by the change of phase with distance. The wave attenuation is measured by the decay of wave amplitude with distance. The change of viscoelastic properties with temperature was studied at room and body temperatures. The wave speed was 1.83m/s at 22°C but reduced to 1.52m/s at 33°C. The viscoelastic ratio was almost constant from 22°C to 33°C. Fresh and decayed tissues were studied. The wave speed of the decayed tissue increased from 1.83m/s of fresh state to 2.73m/s. The viscoelastic ratio was 0.412/mm at the decayed state compared to 0.215/mm at the fresh state. More tissue samples are needed to study these viscoelastic parameters according to specific applications.

  20. Temperature Compensation of Surface Acoustic Waves on Berlinite

    Science.gov (United States)

    Searle, David Michael Marshall

    The surface acoustic wave properties of Berlinite (a-AlPO4) have been investigated theoretically and experimentally, for a variety of crystallographic orientations, to evaluate its possible use as a substrate material for temperature compensated surface acoustic wave devices. A computer program has been developed to calculate the surface wave properties of a material from its elastic, piezoelectric, dielectric and lattice constants and their temperature derivatives. The program calculates the temperature coefficient of delay, the velocity of the surface wave, the direction of power flow and a measure of the electro-mechanical coupling. These calculations have been performed for a large number of orientations using a modified form of the data given by Chang and Barsch for Berlinite and predict several new temperature compensated directions. Experimental measurements have been made of the frequency-temperature response of a surface acoustic wave oscillator on an 80° X axis boule cut which show it to be temperature compensated in qualitative agreement with the theoretical predictions. This orientation shows a cubic frequency-temperature dependence instead of the expected parabolic response. Measurements of the electro-mechanical coupling coefficient k gave a value lower than predicted. Similar measurements on a Y cut plate gave a value which is approximately twice that of ST cut quartz, but again lower than predicted. The surface wave velocity on both these cuts was measured to be slightly higher than predicted by the computer program. Experimental measurements of the lattice parameters a and c are also presented for a range of temperatures from 25°C to just above the alpha-beta transition at 584°C. These results are compared with the values obtained by Chang and Barsch. The results of this work indicate that Berlinite should become a useful substrate material for the construction of temperature compensated surface acoustic wave devices.

  1. Magnetoacoustic surface gravity waves at a spherical interface

    Science.gov (United States)

    Ballai, I.; Forgács-Dajka, E.; Douglas, M.

    2011-03-01

    Aims: The plasma structured by magnetic fields in the solar atmosphere is a perfect medium for the propagation of guided magnetic and magnetoacoustic waves. Geometrical restriction of wave propagation is known to confer a dispersive character for waves. In addition, waves propagating along discontinuities in the medium are known to remain localized. As an extension to theories of guided waves in magnetic slabs and cylinders under solar and stellar conditions, we aim to study the propagation of magnetoacoustic-gravity waves at a spherical interface in the low solar corona (considered here as a density discontinuity), modelling global waves recently observed in the corona in EUV wavelengths. Methods: Using conservation laws at the interface we derive the dispersion relation in spherical geometry with a radially expanding magnetic field in the presence of gravitational stratification. The obtained dispersion relation describing fast magnetoacoustic-gravity surface waves is derived using an approximative method taking into account that propagation takes place near the solar surface. Results: Theoretical results obtained in the present study are applied to investigate the propagation of EIT waves in the low corona. The frequency of waves is shown to increase with decreasing density contrast at the interface. We also show that, for a given azimuthal wavenumber, the magnetic field has a very small effect on the value of the frequency of waves. When plotted against the location of the interface (in the radial direction) the frequency varies inversely proportional to the distance, while for a fixed density ratio and location of the interface the frequency is obtained to be defined in a very narrow region.

  2. Generation of 1D interference patterns of Bloch surface waves

    Science.gov (United States)

    Kadomina, E. A.; Bezus, E. A.; Doskolovich, L. L.

    2016-09-01

    Interference patterns of Bloch surface waves with a period that is significantly less than the wavelength of incident radiation are formed using dielectric diffraction gratings located on the surface of photonic crystal. The simulation based on electromagnetic diffraction theory is used to demonstrate the possibility of high-quality interference patterns due to resonant enhancement of higher evanescent diffraction orders related to the excitation of the Bloch surface waves. The contrast of the interference patterns is close to unity, and the period is less than the period of the diffraction structure by an order of magnitude.

  3. Solar energy converter using surface plasma waves

    Science.gov (United States)

    Anderson, L. M. (Inventor)

    1984-01-01

    Sunlight is dispersed over a diffraction grating formed on the surface of a conducting film on a substrate. The angular dispersion controls the effective grating period so that a matching spectrum of surface plasmons is excited for parallel processing on the conducting film. The resulting surface plasmons carry energy to an array of inelastic tunnel diodes. This solar energy converter does not require different materials for each frequency band, and sunlight is directly converted to electricity in an efficient manner by extracting more energy from the more energetic photons.

  4. Determination of the normalized surface height autocorrelation function of a two-dimensional randomly rough dielectric surface by the inversion of light scattering data in p-polarization

    Science.gov (United States)

    Kryvi, J. B.; Simonsen, I.; Maradudin, A. A.

    2016-09-01

    The contribution to the mean differential reflection coefficient from the in-plane, co-polarized scattering of p- polarized light from a two-dimensional randomly rough dielectric surface is used to invert scattering data to obtain the normalized surface height autocorrelation function of the surface. Within phase perturbation theory this contribution to the mean differential reflection coefficient possesses singularities (poles) when the polar scattering angle θs equals +/-θB= +/- tan-1√E, where E is the dielectric constant of the dielectric medium and θB is the Brewster angle. Nevertheless, we show in this paper that if the mean differential reflection coefficient is measured only in the angular range |θs| inversion scheme. This approach also yields the rms height of the surface roughness, and the dielectric constant of the scattering medium if it is not known in advance. The input data used in this minimization procedure consist of computer simulation results for surfaces defined by exponential and Gaussian surface height correlation functions, without and with the addition of multiplicative noise. The proposed inversion scheme is computationally efficient.

  5. The Dynamics of Flat Surface Internal Geophysical Waves with Currents

    Science.gov (United States)

    Compelli, Alan; Ivanov, Rossen I.

    2016-08-01

    A two-dimensional water wave system is examined consisting of two discrete incompressible fluid domains separated by a free common interface. In a geophysical context this is a model of an internal wave, formed at a pycnocline or thermocline in the ocean. The system is considered as being bounded at the bottom and top by a flatbed and wave-free surface respectively. A current profile with depth-dependent currents in each domain is considered. The Hamiltonian of the system is determined and expressed in terms of canonical wave-related variables. Limiting behaviour is examined and compared to that of other known models. The linearised equations as well as long-wave approximations are presented.

  6. The Dynamics of Flat Surface Internal Geophysical Waves with Currents

    CERN Document Server

    Compelli, Alan

    2016-01-01

    A two-dimensional water wave system is examined consisting of two discrete incompressible fluid domains separated by a free common interface. In a geophysical context this is a model of an internal wave, formed at a pycnocline or thermocline in the ocean. The system is considered as being bounded at the bottom and top by a flatbed and wave-free surface respectively. A current profile with depth-dependent currents in each domain is considered. The Hamiltonian of the system is determined and expressed in terms of canonical wave-related variables. Limiting behaviour is examined and compared to that of other known models. The linearised equations as well as long-wave approximations are presented.

  7. Propagation of elastic waves in a plate with rough surfaces

    Institute of Scientific and Technical Information of China (English)

    DAI Shuwu; ZHANG Hailan

    2003-01-01

    The characteristics of Lamb wave propagating in a solid plate with rough surfacesare studied on the basis of small perturbation approximation. The Rayleigh-Lamb frequencyequation expressed with SA matrix is presented. The Rayleigh-Lamb frequency equation fora rough surface plate is different from that for a smooth surface plate, resulting in a smallperturbation Ak on Lamb wave vector k. The imaginary part of Ak gives the attenuationcaused by wave scattering. An experiment is designed to test our theoretical predications.By using wedge-shape pipes, different Lamb wave modes are excited. The signals at differentpositions are received and analyzed to get the dispersion curves and attenuations of differentmodes. The experimental results are compared with the theoretical predications.

  8. On the cascade mechanism of short surface wave modulation

    Directory of Open Access Journals (Sweden)

    M. Charnotskii

    2002-01-01

    Full Text Available Modulation of short surface ripples by long surface or internal waves by a cascade mechanism is considered. At the first stage, the orbital velocity of the long wave (LW adiabatically modulates an intermediate length nonlinear gravity wave (GW, which generates a bound (parasitic capillary wave (CW near its crest in a wide spatial frequency band. Due to strong dependence of the CW amplitude on that of the GW, the resulting ripple modulation by LW can be strong. Adiabatic modulation at the first stage is calculated for an arbitrarily strong LW current. The CWs are calculated based on the Lonquet-Higgins theory, in the framework of a steady periodic solution, which proves to be sufficient for the cases considered. Theoretical results are compared with data from laboratory experiments. A discussion of related sea clutter data is given in the conclusion.

  9. The Whitham Equation as a Model for Surface Water Waves

    CERN Document Server

    Moldabayev, Daulet; Dutykh, Denys

    2014-01-01

    The Whitham equation was proposed as an alternate model equation for the simplified description of uni-directional wave motion at the surface of an inviscid fluid. As the Whitham equation incorporates the full linear dispersion relation of the water wave problem, it is thought to provide a more faithful description of shorter waves of small amplitude than traditional long wave models such as the KdV equation. In this work, we identify a scaling regime in which the Whitham equation can be derived from the Hamiltonian theory of surface water waves. The Whitham equation is integrated numerically, and it is shown that the equation gives a close approximation of inviscid free surface dynamics as described by the Euler equations. The performance of the Whitham equation as a model for free surface dynamics is also compared to two standard free surface models: the KdV and the BBM equation. It is found that in a wide parameter range of amplitudes and wavelengths, the Whitham equation performs on par with or better tha...

  10. Artificial ocean upwelling utilizing the energy of surface waves

    Science.gov (United States)

    Soloviev, Alexander

    2016-04-01

    Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10 oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.

  11. Modeling anomalous surface - wave propagation across the Southern Caspian basin

    Energy Technology Data Exchange (ETDEWEB)

    Priestly, K.F.; Patton, H.J.; Schultz, C.A.

    1998-01-09

    The crust of the south Caspian basin consists of 15-25 km of low velocity, highly attenuating sediment overlying high velocity crystalline crust. The Moho depth beneath the basin is about 30 km as compared to about 50 km in the surrounding region. Preliminary modeling of the phase velocity curves shows that this thick sediments of the south Caspian basin are also under-lain by a 30-35 km thick crystalline crust and not by typical oceanic crust. This analysis also suggest that if the effect of the over-pressuring of the sediments is to reduce Poissons` ratio, the over-pressured sediments observed to approximately 5 km do not persist to great depths. It has been shown since 1960`s that the south Caspian basin blocks the regional phase Lg. Intermediate frequency (0.02-0.04 Hz) fundamental mode Raleigh waves propagating across the basin are also severely attenuated, but the low frequency surface waves are largely unaffected. This attenuation is observed along the both east-to-west and west-to-east great circle paths across the basin, and therefore it cannot be related to a seismograph site effect. We have modeled the response of surface waves in an idealized rendition of the south Caspian basin model using a hybrid normal mode / 2-D finite difference approach. To gain insight into the features of the basin which cause the anomalous surface wave propagation, we have varied parameters of the basin model and computed synthetic record sections to compare with the observed seismograms. We varied the amount of mantel up-warp, the shape of the boundaries, the thickness and shear wave Q of the sediments and mantle, and the depth of the water layer. Of these parameters, the intermediate frequency surface waves are most severely affected by the sediments thickness and shear wave attenuation. fundamental mode Raleigh wave phase velocities measure for paths crossing the basin are extremely low.

  12. Gravitational waves from surface inhomogeneities of neutron stars

    Science.gov (United States)

    Konar, Sushan; Mukherjee, Dipanjan; Bhattacharya, Dipankar; Sarkar, Prakash

    2016-11-01

    Surface asymmetries of accreting neutron stars are investigated for their mass quadrupole moment content. Though the amplitude of the gravitational waves from such asymmetries seems to be beyond the limit of detectability of the present generation of detectors, it appears that rapidly rotating neutron stars with strong magnetic fields residing in high-mass x-ray binaries would be worth considering for a targeted search for continuous gravitational waves with the next generation of instruments.

  13. High-Temperature Surface-Acoustic-Wave Transducer

    Science.gov (United States)

    Zhao, Xiaoliang; Tittmann, Bernhard R.

    2010-01-01

    Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection. An efficient, high-temperature, low-profile surface acoustic wave transducer design has been identified and tested for nondestructive evaluation of structures or materials. The development is a Sol-Gel bismuth titanate-based surface-acoustic-wave (SAW) sensor that can generate efficient surface acoustic waves for crack inspection. The produced sensor is very thin (submillimeter), and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. One major uniqueness of the Sol-Gel bismuth titanate SAW sensor is that it is easy to implement to structures of various shapes. With a spray coating process, the sensor can be applied to surfaces of large curvatures. Second, the sensor is very thin (as a coating) and has very minimal effect on airflow or rotating equipment imbalance. Third, it can withstand temperatures up to 530 C, which is very useful for engine applications where high temperature is an issue.

  14. Lateral Flooding Associated to Wave Flood Generation on River Surface

    Science.gov (United States)

    Ramírez-Núñez, C.; Parrot, J.-F.

    2016-06-01

    This research provides a wave flood simulation using a high resolution LiDAR Digital Terrain Model. The simulation is based on the generation of waves of different amplitudes that modify the river level in such a way that water invades the adjacent areas. The proposed algorithm firstly reconstitutes the original river surface of the studied river section and then defines the percentage of water loss when the wave floods move downstream. This procedure was applied to a gently slope area in the lower basin of Coatzacoalcos river, Veracruz (Mexico) defining the successive areas where lateral flooding occurs on its downstream movement.

  15. Surface waves propagation on a turbulent flow forced electromagnetically

    CERN Document Server

    Gutiérrez, Pablo

    2015-01-01

    We study the propagation of monochromatic surface waves on a turbulent flow. The flow is generated in a layer of liquid metal by an electromagnetic forcing. This forcing creates a quasi two-dimensional (2D) turbulence with strong vertical vorticity. The turbulent flow contains much more energy than the surface waves. In order to focus on the surface wave, the deformations induced by the turbulent flow are removed. This is done by performing a coherent phase averaging. For wavelengths smaller than the forcing lengthscale, we observe a significant increase of the wavelength of the propagating wave that has not been reported before. We suggest that it can be explained by the random deflection of the wave induced by the velocity gradient of the turbulent flow. Under this assumption, the wavelength shift is an estimate of the fluctuations of deflection angle. The local measurements of the wave frequency far from the wavemaker do not reveal such systematic behavior, although a small shift is measured. Finally we qu...

  16. Analysis shear wave velocity structure obtained from surface wave methods in Bornova, Izmir

    Energy Technology Data Exchange (ETDEWEB)

    Pamuk, Eren, E-mail: eren.pamuk@deu.edu.tr; Akgün, Mustafa, E-mail: mustafa.akgun@deu.edu.tr [Department of Geophysical Engineering, Dokuz Eylul University, Izmir (Turkey); Özdağ, Özkan Cevdet, E-mail: cevdet.ozdag@deu.edu.tr [Dokuz Eylul University Rectorate, Izmir (Turkey)

    2016-04-18

    Properties of the soil from the bedrock is necessary to describe accurately and reliably for the reduction of earthquake damage. Because seismic waves change their amplitude and frequency content owing to acoustic impedance difference between soil and bedrock. Firstly, shear wave velocity and depth information of layers on bedrock is needed to detect this changing. Shear wave velocity can be obtained using inversion of Rayleigh wave dispersion curves obtained from surface wave methods (MASW- the Multichannel Analysis of Surface Waves, ReMi-Refraction Microtremor, SPAC-Spatial Autocorrelation). While research depth is limeted in active source study, a passive source methods are utilized for deep depth which is not reached using active source methods. ReMi method is used to determine layer thickness and velocity up to 100 m using seismic refraction measurement systems.The research carried out up to desired depth depending on radius using SPAC which is utilized easily in conditions that district using of seismic studies in the city. Vs profiles which are required to calculate deformations in under static and dynamic loads can be obtained with high resolution using combining rayleigh wave dispersion curve obtained from active and passive source methods. In the this study, Surface waves data were collected using the measurements of MASW, ReMi and SPAC at the İzmir Bornova region. Dispersion curves obtained from surface wave methods were combined in wide frequency band and Vs-depth profiles were obtained using inversion. Reliability of the resulting soil profiles were provided by comparison with theoretical transfer function obtained from soil paremeters and observed soil transfer function from Nakamura technique and by examination of fitting between these functions. Vs values are changed between 200-830 m/s and engineering bedrock (Vs>760 m/s) depth is approximately 150 m.

  17. Towards operational determination of boundary layer height using sodar/RASS soundings and surface heat flux data

    Energy Technology Data Exchange (ETDEWEB)

    Kirtzel, H.J. [METEK GmbH, Elmshorn (Germany); Hennemuth, B.

    2008-06-15

    A method for the derivation of boundary layer height from measurements of sodar, RASS and sonic anemometer-thermometer data is presented. Datasets of the years 2004 and 2005 measured at the Meteorological Observatory Lindenberg (Germany) are used. The time resolution is 15 min. Special emphasis is laid on air pollution issues where mixing heights shallower than 500 m are important. A difference to the numerous methods already presented in the literature is twofold. Firstly, not only single vertical profiles of measured or derived parameters are used but also bulk information, e.g. histograms and boundary layer evolution over time intervals, is considered. Secondly, the presented method analyses sodar data and confirms or corrects the results by use of temperature profiles from RASS and by sonic surface heat flux data. The results are presented as frequency distributions for the whole period and for the four seasons, stratified by the hour of the day. The additional analysis of temperature profiles and surface heat flux is particularly helpful for the detection of stable boundary layers and increases the number of shallow boundary layers particularly in the evening. The comparison with radiosonde-derived boundary layer heights shows a good agreement, deviations are mostly due to a complicated boundary layer structure. Boundary layer depths derived after a formalism given in the German administrative regulation TA-Luft show - compared to the sodar/RASS-derived values - too many very small or partly very large values. The height range between 100 m and 300 m which is essential for pollutant dispersion issues is nearly missing. Requirements for a future operational use of the method are formulated. (orig.)

  18. Enhanced Sensitive Love Wave Surface Acoustic Wave Sensor Designed for Immunoassay Formats

    Directory of Open Access Journals (Sweden)

    Mihaela Puiu

    2015-05-01

    Full Text Available We report a Love wave surface acoustic wave (LW-SAW immunosensor designed for the detection of high molecular weight targets in liquid samples, amenable also for low molecular targets in surface competition assays. We implemented a label-free interaction protocol similar to other surface plasmon resonance bioassays having the advantage of requiring reduced time analysis. The fabricated LW-SAW sensor supports the detection of the target in the nanomolar range, and can be ultimately incorporated in portable devices, suitable for point-of-care testing (POCT applications.

  19. Enhanced sensitive love wave surface acoustic wave sensor designed for immunoassay formats.

    Science.gov (United States)

    Puiu, Mihaela; Gurban, Ana-Maria; Rotariu, Lucian; Brajnicov, Simona; Viespe, Cristian; Bala, Camelia

    2015-05-05

    We report a Love wave surface acoustic wave (LW-SAW) immunosensor designed for the detection of high molecular weight targets in liquid samples, amenable also for low molecular targets in surface competition assays. We implemented a label-free interaction protocol similar to other surface plasmon resonance bioassays having the advantage of requiring reduced time analysis. The fabricated LW-SAW sensor supports the detection of the target in the nanomolar range, and can be ultimately incorporated in portable devices, suitable for point-of-care testing (POCT) applications.

  20. Influence of the atmosphere on the evaluation of the geopotential from global models on the surface of the Earth: implications for the realization of a World Height System

    Science.gov (United States)

    Mäkinen, Jaakko

    2016-04-01

    Outside the atmosphere, the potential of a standard atmosphere can with high accuracy be approximated with the potential of a surface layer with the same mass, independently of the scale height of the atmosphere. Not so when the potential is evaluated on the surface of the Earth. In a spherically symmetric approximation and assuming a scale height of 7.6 km, the potential at zero height is in a back-of-the-envelope calculation 0.12 percent less than the potential of the surface laýer. This corresponds to a difference of -1.2 ppb in the total geopotential evaluated on the surface of the Earth, the equivalent of a difference of +8 mm in height. Using a realistic atmospheric and Earth model, the difference is not constant. This has obvious implications for the geopotential values associated with a World Height System. The question has in fact already been extensively analyzed in the context of geoid determination.

  1. Langasite Surface Acoustic Wave Sensors: Fabrication and Testing

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Peng; Greve, David W.; Oppenheim, Irving J.; Chin, Tao-Lun; Malone, Vanessa

    2012-02-01

    We report on the development of harsh-environment surface acoustic wave sensors for wired and wireless operation. Surface acoustic wave devices with an interdigitated transducer emitter and multiple reflectors were fabricated on langasite substrates. Both wired and wireless temperature sensing was demonstrated using radar-mode (pulse) detection. Temperature resolution of better than ±0.5°C was achieved between 200°C and 600°C. Oxygen sensing was achieved by depositing a layer of ZnO on the propagation path. Although the ZnO layer caused additional attenuation of the surface wave, oxygen sensing was accomplished at temperatures up to 700°C. The results indicate that langasite SAW devices are a potential solution for harsh-environment gas and temperature sensing.

  2. Surface Wave Velocity-Stress Relationship in Uniaxially Loaded Concrete

    DEFF Research Database (Denmark)

    Shokouhi, Parisa; Zoëga, Andreas; Wiggenhauser, Herbert

    2012-01-01

    loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface......The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave...... velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several...

  3. A Variable-resolution Surface Wave Dispersion Study of Eurasia, North Africa, and Surrounding Regions

    Energy Technology Data Exchange (ETDEWEB)

    Pasyanos, M E

    2005-03-21

    This paper presents the results of a large-scale study of surface wave dispersion performed across Eurasia and North Africa. Improvements were made to previous surface wave work by enlarging the study region, increasing path density, improving spatial resolution, and expanding the period range. This study expands the coverage area northwards and eastwards relative to a previous dispersion analysis, which covered only North Africa and the Middle East. We have significantly increased the number of seismograms examined and group velocity measurements made. We have now made good quality dispersion measurements for about 30,000 Rayleigh wave and 20,000 Love wave paths, and have incorporated measurements from several other researchers into the study. A conjugate gradient method was employed for the group velocity tomography, which improved the inversion from the previous study by adopting a variable smoothness. This technique allows us to go to higher resolution where the data allow without producing artifacts. The current results include both Love and Rayleigh wave inversions across the region for periods from 7 to 100 seconds at 1{sup o} resolution. Short period group velocities are sensitive to slow velocities associated with large sedimentary features such as the Caspian Sea, West Siberian Platform, Mediterranean Sea, Bay of Bengal, Tarim Basin, and Persian Gulf. Intermediate periods are sensitive to differences in crustal thickness, such as those between oceanic and continental crust or along orogenic zones and continental plateaus. At longer periods, fast velocities are consistently found beneath cratons while slow upper mantle velocities occur along rift systems, subduction zones, and collision zones such as the Tethys Belt. We have compared the group velocities at various periods with features such as sediment thickness, topographic height, crustal thickness, proximity to plate boundaries, lithospheric age and lithospheric thickness, and find significant

  4. Multichannel analysis of surface wave method with the autojuggie

    Science.gov (United States)

    Tian, G.; Steeples, D.W.; Xia, J.; Miller, R.D.; Spikes, K.T.; Ralston, M.D.

    2003-01-01

    The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the 'autojuggie') is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys. ?? 2003 Elsevier Science Ltd. All rights reserved.

  5. Engineered metabarrier as shield from seismic surface waves

    Science.gov (United States)

    Palermo, Antonio; Krödel, Sebastian; Marzani, Alessandro; Daraio, Chiara

    2016-12-01

    Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by burying sub-wavelength resonant structures under the soil surface. Each resonant structure consists of a cylindrical mass suspended by elastomeric springs within a concrete case and can be tuned to the resonance frequency of interest. The design allows controlling seismic waves with wavelengths from 10-to-100 m with meter-sized resonant structures. We develop an analytical model based on effective medium theory able to capture the mode conversion mechanism. The model is used to guide the design of metabarriers for varying soil conditions and validated using finite-element simulations. We investigate the shielding performance of a metabarrier in a scaled experimental model and demonstrate that surface ground motion can be reduced up to 50% in frequency regions below 10 Hz, relevant for the protection of buildings and civil infrastructures.

  6. Engineered metabarrier as shield from seismic surface waves.

    Science.gov (United States)

    Palermo, Antonio; Krödel, Sebastian; Marzani, Alessandro; Daraio, Chiara

    2016-12-20

    Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by burying sub-wavelength resonant structures under the soil surface. Each resonant structure consists of a cylindrical mass suspended by elastomeric springs within a concrete case and can be tuned to the resonance frequency of interest. The design allows controlling seismic waves with wavelengths from 10-to-100 m with meter-sized resonant structures. We develop an analytical model based on effective medium theory able to capture the mode conversion mechanism. The model is used to guide the design of metabarriers for varying soil conditions and validated using finite-element simulations. We investigate the shielding performance of a metabarrier in a scaled experimental model and demonstrate that surface ground motion can be reduced up to 50% in frequency regions below 10 Hz, relevant for the protection of buildings and civil infrastructures.

  7. Sensitivity of surface acoustic wave devices

    Science.gov (United States)

    Filipiak, Jerzy; Zubko, Konrad

    2001-08-01

    The SAW devices are widely used as filters, delay lines, resonators and gas sensors. It is possible to use it as mechanical force. The paper describes sensitivity of acceleration sensor based on SAW using the Rayleigh wave propagation. Since characteristic of acceleration SAW sensors are largely determined by piezoelectric materials, it is very important to select substrate with required characteristics. Researches and numerical modeling based on simply sensor model include piezoelectric beam with unilateral free end. An aggregated mass is connected to the one. The dimension and aggregated mass are various. In this case a buckling stress and sensitivity are changed. Sensitivity in main and perpendicular axis are compare for three sensor based on SiO2, LiNbO3, Li2B4O7. Influences of phase velocity, electro-mechanical coupling constant and density on sensitivity are investigated. Some mechanical parameters of the substrates in dynamic work mode are researched using sensor model and Rayleigh model of vibrations without vibration damping. The model is useful because it simply determines dependencies between sensor parameters and substrate parameters. Differences between measured and evaluated quantities are less than 5 percent. Researches based on sensor modes, which fulfilled mechanical specifications similarly to aircraft navigation.

  8. Characteristics of surface waves in anisotropic left-handed materials

    Institute of Scientific and Technical Information of China (English)

    Jiang Yong-Yuan; Shi Hong-Yan; Zhang Yong-Qiang; Hou Chun-Feng; Sun Xiu-Dong

    2007-01-01

    We report the coexistence of TE and TM surface modes in certain same frequency domain at the interface between one isotropic regular medium and another biaxially anistotropic left-handed medium. The conditions for the existence of TE and TM polarized surface waves in biaxially anisotropic left-handed materials are identified, respectively.The Poynting vector and the energy density associated with surface modes are calculated. Depending on the system parameters, either TE or TM surface modes can have the time averaged Poynting vector directed to or opposite to the mode phase velocity. It is seen that the characteristics of surface waves in biaxially anisotropic left-handed media are significantly different from that in isotropic left-handed media.

  9. Super-virtual Interferometric Separation and Enhancement of Back-scattered Surface Waves

    KAUST Repository

    Guo, Bowen

    2015-08-19

    Back-scattered surface waves can be migrated to detect near-surface reflectors with steep dips. A robust surface-wave migration requires the prior separation of the back-scattered surface-wave events from the data. This separation is often difficult to implement because the back-scattered surface waves are masked by the incident surface waves. We mitigate this problem by using a super-virtual interferometric method to enhance and separate the back-scattered surface waves. The key idea is to calculate the virtual back-scattered surface waves by stacking the resulting virtual correlated and convolved traces associated with the incident and back-scattered waves. Stacking the virtual back-scattered surface waves improves their signal-to-noise ratio and separates the back-scattered surface-waves from the incident field. Both synthetic and field data results validate the robustness of this method.

  10. Fabricating micro embossments on the metal surface through spatially modulating laser-induced shock wave

    Science.gov (United States)

    Ye, Y. X.; Xuan, T.; Lian, Z. C.; Hua, X. J.; Fu, Y. H.

    2015-12-01

    In this paper, we propose one improved method to fabricate micro embossments on the metal surface through laser shock processing. One mapping layer with holes must be actively designed and produced on the metal surface, with which, laser-induced shock wave will be spatially modulated. Laser shock experiments were conducted. Then the surface morphologies, and metallographic microstructures were characterized. The forming process of the micro embossments was simulated with ABAQUS. The results show that under the spatially modulated shock loading, the surface material flows from the high-pressure zone to the low-pressure zone, which is responsible for forming the micro embossments. The shapes, sizes and arrangements of the micro embossments conform to those of the mapping holes. The hardnesses on the entire laser-shocked zones improve remarkably due to the plastic deformation at a high strain rate. The influences of the laser energy and mask pattern on the embossed structures are presented. Within certain limits, increasing laser energy is beneficial for making the embossment more convex. However, further excessively increasing the laser energy, the embossment will exhibit the height saturation due to the pressure rise within the closed mapping hole. The transverse sizes of the mapping holes also can influence the embossment heights significantly. Process parameters need to be chosen carefully to suppress the severe adiabatic compression of the gas within the mapping holes, and then avoid weakening the mechanical properties of the micro embossments. This method has a potential application in manufacturing protruded structures on the metal surface.

  11. Investigation of surface magnetostatic wave propagation in ferrite superconductor structure

    CERN Document Server

    Semenov, A A; Melkov, A A; Bobyl', A V; Suris, R A; Gal'perin, Y M; Iokhansen, T K

    2001-01-01

    Electrodynamic model describing dispersion properties of surface magnetostatic wave in ferrite/superconductor structure was suggested. On the basis of the model a new method of ascertaining superhigh frequency surface resistance R sub s of superconducting films in magnetic fields was developed. The calculated values agree with the results obtained by the Tauber method, making up R sub s =0.20-1.96 m Ohm. A regulated incursion of wave phase amounting to about 1.5 pi with the change in penetration depth 2.0-0.8 mu m for YBCO film was attained for YIG/YBCO structures

  12. Photonic Crystal Biosensor Based on Optical Surface Waves

    Directory of Open Access Journals (Sweden)

    Giovanni Dietler

    2013-02-01

    Full Text Available A label-free biosensor device based on registration of photonic crystal surface waves is described. Angular interrogation of the optical surface wave resonance is used to detect changes in the thickness of an adsorbed layer, while an additional simultaneous detection of the critical angle of total internal reflection provides independent data of the liquid refractive index. The abilities of the device are demonstrated by measuring of biotin molecule binding to a streptavidin monolayer, and by measuring association and dissociation kinetics of immunoglobulin G proteins. Additionally, deposition of PSS / PAH polyelectrolytes is recorded in situ resulting calculation of PSS and PAH monolayer thicknesses separately.

  13. Photonic crystal biosensor based on optical surface waves.

    Science.gov (United States)

    Konopsky, Valery N; Karakouz, Tanya; Alieva, Elena V; Vicario, Chiara; Sekatskii, Sergey K; Dietler, Giovanni

    2013-02-19

    A label-free biosensor device based on registration of photonic crystal surface waves is described. Angular interrogation of the optical surface wave resonance is used to detect changes in the thickness of an adsorbed layer, while an additional simultaneous detection of the critical angle of total internal reflection provides independent data of the liquid refractive index. The abilities of the device are demonstrated by measuring of biotin molecule binding to a streptavidin monolayer, and by measuring association and dissociation kinetics of immunoglobulin G proteins. Additionally, deposition of PSS / PAH polyelectrolytes is recorded in situ resulting calculation of PSS and PAH monolayer thicknesses separately.

  14. Techniques for Down-Sampling a Measured Surface Height Map for Model Validation

    Science.gov (United States)

    Sidick, Erkin

    2012-01-01

    This software allows one to down-sample a measured surface map for model validation, not only without introducing any re-sampling errors, but also eliminating the existing measurement noise and measurement errors. The software tool of the current two new techniques can be used in all optical model validation processes involving large space optical surfaces

  15. Unidirectional propagation of magnetostatic surface spin waves at a magnetic film surface

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Kin L.; Bao, Mingqiang, E-mail: mingqiangbao@gmail.com, E-mail: caross@mit.edu; Lin, Yen-Ting; Wang, Kang L. [Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, California 90095 (United States); Bi, Lei [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Wen, Qiye; Zhang, Huaiwu [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Chatelon, Jean Pierre [Univerisité de Saint-Etienne, Université de Lyon, LT2C, 25 rue du Docteur Rémy Annino, 42000 Saint-Etienne (France); Ross, C. A., E-mail: mingqiangbao@gmail.com, E-mail: caross@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-12-08

    An analytical expression for the amplitudes of magnetostatic surface spin waves (MSSWs) propagating in opposite directions at a magnetic film surface is presented. This shows that for a given magnetic field H, it is forbidden for an independent MSSW to propagate along the direction of −H{sup →}×n{sup →}, where n{sup →} is the surface normal. This unidirectional propagation property is confirmed by experiments with both permalloy and yttrium iron garnet films of different film thicknesses, and has implications in the design of spin-wave devices such as isolators and spin-wave diodes.

  16. The stress-induced surface wave velocity variations in concrete

    Science.gov (United States)

    Spalvier, Agustin; Bittner, James; Evani, Sai Kalyan; Popovics, John S.

    2017-02-01

    This investigation studies the behavior of surface wave velocity in concrete specimens subjected to low levels of compressive and tensile stress in beams from applied flexural loads. Beam specimen is loaded in a 4-point-load bending configuration, generating uniaxial compression and tension stress fields at the top and bottom surfaces of the beam, respectively. Surface waves are generated through contactless air-coupled transducers and received through contact accelerometers. Results show a clear distinction in responses from compression and tension zones, where velocity increases in the former and decreases in the latter, with increasing load levels. These trends agree with existing acoustoelastic literature. Surface wave velocity tends to decrease more under tension than it tends to increase under compression, for equal load levels. It is observed that even at low stress levels, surface wave velocity is affected by acoustoelastic effects, coupled with plastic effects (stress-induced damage). The acoustoelastic effect is isolated by means of considering the Kaiser effect and by experimentally mitigating the viscoelastic effects of concrete. Results of this ongoing investigation contribute to the overall knowledge of the acoustoelastic behavior of concrete. Applications of this knowledge may include structural health monitoring of members under flexural loads, improved high order modelling of materials, and validation of results seen in dynamic acoustoelasticity testing.

  17. Experimental evidence of wave chaos from a double slit experiment with water surface waves.

    Science.gov (United States)

    Tang, Yunfei; Shen, Yifeng; Yang, Jiong; Liu, Xiaohan; Zi, Jian; Li, Baowen

    2008-10-01

    In this paper, we report experimental evidence of wave chaos using the double slit water surface wave experiment. We demonstrate that classical dynamics of a domain manifests itself in the interference patterns after the diffraction behind the double slit. For a domain whose classical dynamics is integrable clear interference fringes can be observed behind the double slits; for a domain whose classical dynamics is chaotic, however, interference fringes can totally disappear. Our experimental results clearly demonstrate that the centuries-old double slit experiment can render an excellent tool to observe the manifestations of wave chaos.

  18. Attenuation of Rayleigh Surface Waves in a Porous Material

    Institute of Scientific and Technical Information of China (English)

    DEBBOUB Salima; BOUMA(I)ZA Youcef; BOUDOUR Amar; TAHRAOUI Tarek

    2012-01-01

    Using acoustic microscopy at higher frequency,we show the velocity evolutions of surface acoustic waves,in particular Rayleigh waves that depend on porosity for a mesoporous silicon layer.The velocities are obtained from different V(z) curves,which are determined experimentally at a frequency of 600MHz.The analysis of V(z) data yields attenuation that is directly dependent on porosity.On the other hand,αN attenuation has been modeled and allows us to investigate its influence on the velocity VR of the propagation for Rayleigh waves.%Using acoustic microscopy at higher frequency, we show the velocity evolutions of surface acoustic waves, in particular Rayleigh waves that depend on porosity for a mesoporous silicon layer. The velocities are obtained from different V(z) curves, which are determined experimentally at a frequency of 600 MHz. The analysis of V(z) data yields attenuation that is directly dependent on porosity. On the other hand, αN attenuation has been modeled and allows us to investigate its influence on the velocity VR of the propagation for Rayleigh waves.

  19. Application of Displacement Height and Surface Roughness Length to Determination Boundary Layer Development Length over Stepped Spillway

    Directory of Open Access Journals (Sweden)

    Xiangju Cheng

    2014-12-01

    Full Text Available One of the most uncertain parameters in stepped spillway design is the length (from the crest of boundary layer development. The normal velocity profiles responding to the steps as bed roughness are investigated in the developing non-aerated flow region. A detailed analysis of the logarithmic vertical velocity profiles on stepped spillways is conducted through experimental data to verify the computational code and numerical experiments to expand the data available. To determine development length, the hydraulic roughness and displacement thickness, along with the shear velocity, are needed. This includes determining displacement height d and surface roughness length z0 and the relationship of d and z0 to the step geometry. The results show that the hydraulic roughness height ks is the primary factor on which d and z0 depend. In different step height, step width, discharge and intake Froude number, the relations d/ks = 0.22–0.27, z0/ks = 0.06–0.1 and d/z0 = 2.2–4 result in a good estimate. Using the computational code and numerical experiments, air inception will occur over stepped spillway flow as long as the Bauer-defined boundary layer thickness is between 0.72 and 0.79.

  20. Surface properties of solids and surface acoustic waves: Application to chemical sensors and layer characterization

    Science.gov (United States)

    Krylov, V. V.

    1995-09-01

    A general phenomenological approach is given for the description of mechanical surface properties of solids and their influence on surface acoustic wave propogation. Surface properties under consideration may be changes of the stress distribution in subsurface atomic layers, the presence of adsorbed gas molecules, surface degradation as a result of impacts from an aggressive environment, damage due to mechanical manufacturing or polishing, deposition of thin films or liquid layers, surface corrugations, etc. If the characteristic thickness of the affected layers is much less than the wavelengths of the propagating surface waves, then the effects of all these irregularities can be described by means of non-classical boundary conditions incorporating the integral surface parameters such as surface tension, surface moduli of elasticity and surface mass density. The effect of surface properties on the propagation of Rayleigh surface waves is analysed in comparison with the results of traditional approaches, in particular with Auld's energy perturbation method. One of the important implications of the above-mentioned boudnary conditions is that they are adequate for the description of the effect of rarely distributed adsorbed atoms or molecules. This allows, in particular, to obtain a rigorous theoretical description of chemical sensors using surface acoustic waves and to derive analytical expressions for their sensitivity.

  1. Imaging near-surface heterogeneities by natural migration of backscattered surface waves

    KAUST Repository

    AlTheyab, Abdullah

    2016-02-01

    We present a migration method that does not require a velocity model to migrate backscattered surface waves to their projected locations on the surface. This migration method, denoted as natural migration, uses recorded Green\\'s functions along the surface instead of simulated Green\\'s functions. The key assumptions are that the scattering bodies are within the depth interrogated by the surface waves, and the Green\\'s functions are recorded with dense receiver sampling along the free surface. This natural migration takes into account all orders of multiples, mode conversions and non-linear effects of surface waves in the data. The natural imaging formulae are derived for both active source and ambient-noise data, and computer simulations show that natural migration can effectively image near-surface heterogeneities with typical ambient-noise sources and geophone distributions.

  2. Sea surface height anomaly and geostrophic circulation variations in the South China Sea from TOPEX/POSEIDON altimetry

    Institute of Scientific and Technical Information of China (English)

    刘克修; 马继瑞; 许建平; 韩桂军; 范振华

    2002-01-01

    --The sea surface height anomaly (SSHA) and geostrophic circulation in the South ChinaSea (SCS) are studied using TOPEX/POSEIDON (T/P) altimetry data. The SSHA, which is obtained after tidal correction based on the tidal results from T/P data, is predominated by seasonal alternating monsoons. The results reveal that the SSHA in the central part of the SCS is positive in spring and summer, but negative in autumn and winter. It is also found that the SSHA in the SCS can be approached with the sum of tidal constituents SA and SSA. The geostrophic circulations in the SCS are calculated according to sea surface dynamic topography, which is the sum of SSHA and mean sea surface height. It is suggested that the circulation in the upper layer of the SCS is generally cyclonic and notably western intensified during autumn and winter, while the western intensification is weak during spring and summer. It is also indicated that the Kuroshio intrudes into the northeastern SCS throuth the Luzon Strait in winter. But there is no indication of Kuroshio intruding into the SCS in summer.

  3. Flow above the free end of a surface-mounted finite-height circular cylinder: A review

    Science.gov (United States)

    Sumner, D.

    2013-11-01

    The wake of a surface-mounted finite-height circular cylinder and the associated vortex patterns are strongly dependent on the cylinder aspect ratio and the thickness of the boundary layer on the ground plane relative to the dimensions of the cylinder. Above a critical aspect ratio, the mean wake is characterized by streamwise tip vortex structures and Kármán vortex shedding from the sides of the cylinder. Below a critical aspect ratio, a unique mean wake structure is observed. Recent experimental studies in the literature that used phase-averaged techniques, as well as recent numerical simulations, have led to an improved physical understanding of the near-wake vortex flow patterns. However, the flow above the free end of the finite circular cylinder, and its relationship to the near wake, has not been systematically studied. The effects of aspect ratio and boundary layer thickness on the free-end flow field are also not completely understood, nor has the influence of Reynolds number on the free-end flow field been fully explored. Common features associated with the free end include separation from the leading edge, a mean recirculation zone containing a prominent cross-stream arch (or mushroom) vortex, and reattachment onto the free-surface. Other flow features that remain to be clarified include a separation bubble near the leading edge, one or two cross-stream vortices within this separation bubble, the origins of the streamwise tip or trailing vortices, and various critical points in the near-surface flow topology. This paper reviews the current understanding of the flow above the free end of a surface-mounted finite-height circular cylinder, with a focus on models of the flow field, surface oil flow visualization studies, pressure and heat flux distributions on the free-end surface, measurements of the local velocity field, and numerical simulations, found in the literature.

  4. Polarization controlled directional excitation of Bloch surface waves (Conference Presentation)

    Science.gov (United States)

    Kovalevich, Tatiana; Boyer, Philippe; Bernal, Maria-Pilar; Kim, Myun-Sik; Herzig, Hans Peter; Grosjean, Thierry

    2016-09-01

    Bloch surface waves (BSWs) are electromagnetic surface waves which can be excited at the interface between periodic dielectric multilayer and a surrounding medium. In comparison with surface plasmon polaritons these surface states perform high quality factor due to low loss characteristics of dielectric materials and can be exited both by TE and TM polarized light. A platform consisting of periodic stacks of alternative SiO2 and Si3N4 layers is designed and fabricated to work at the wavelength of 1.55 µm. The platform has an application in sensing and in integrated optics domain. A standard way of BSW excitation is coupling via Kretschmann configuration, but in this work we investigate a grating coupling of BSWs. Grating parameters are analytically and numerically optimized by RCWA and FDTD methods in order to obtain the best coupling conditions. The light is launched orthogonally to the surface of the photonic crystal and the grating. Due to a special grating configuration we demonstrate directionality of the BSW propagation depending on polarization of the incident light. The structure was experimentally realized on the surface of the photonic crystal by FIB milling. Experimental results are in a good agreement with a theory. The investigated configuration can be successfully used as a BSW launcher in on-chip all-optical integrated systems and work as a surface wave switch or modulator.

  5. Boussinesq modeling of surface waves due to underwater landslides

    Directory of Open Access Journals (Sweden)

    D. Dutykh

    2013-05-01

    Full Text Available Consideration is given to the influence of an underwater landslide on waves at the surface of a shallow body of fluid. The equations of motion that govern the evolution of the barycenter of the landslide mass include various dissipative effects due to bottom friction, internal energy dissipation, and viscous drag. The surface waves are studied in the Boussinesq scaling, with time-dependent bathymetry. A numerical model for the Boussinesq equations is introduced that is able to handle time-dependent bottom topography, and the equations of motion for the landslide and surface waves are solved simultaneously. The numerical solver for the Boussinesq equations can also be restricted to implement a shallow-water solver, and the shallow-water and Boussinesq configurations are compared. A particular bathymetry is chosen to illustrate the general method, and it is found that the Boussinesq system predicts larger wave run-up than the shallow-water theory in the example treated in this paper. It is also found that the finite fluid domain has a significant impact on the behavior of the wave run-up.

  6. Surface waves on currents with arbitrary vertical shear

    Science.gov (United States)

    Smeltzer, Benjamin K.; Ellingsen, Simen Å.

    2017-04-01

    We study dispersion properties of linear surface gravity waves propagating in an arbitrary direction atop a current profile of depth-varying magnitude using a piecewise linear approximation and develop a robust numerical framework for practical calculation. The method has been much used in the past for the case of waves propagating along the same axis as the background current, and we herein extend and apply it to problems with an arbitrary angle between the wave propagation and current directions. Being valid for all wavelengths without loss of accuracy, the scheme is particularly well suited to solve problems involving a broad range of wave vectors, such as ship waves and Cauchy-Poisson initial value problems. We examine the group and phase velocities over different wavelength regimes and current profiles, highlighting characteristics due to the depth-variable vorticity. We show an example application to ship waves on an arbitrary current profile and demonstrate qualitative differences in the wake patterns between concave down and concave up profiles when compared to a constant shear profile with equal depth-averaged vorticity. We also discuss the nature of additional solutions to the dispersion relation when using the piecewise-linear model. These are vorticity waves, drifting vortical structures which are artifacts of the piecewise model. They are absent for a smooth profile and are spurious in the present context.

  7. Observations of surface waves interacting with ice using stereo imaging

    Science.gov (United States)

    Campbell, Alexander J.; Bechle, Adam J.; Wu, Chin H.

    2014-06-01

    A powerful Automated Trinocular Stereo Imaging System (ATSIS) is used to remotely measure waves interacting with three distinct ice types: brash, frazil, and pancake. ATSIS is improved with a phase-only correlation matching algorithm and parallel computation to provide high spatial and temporal resolution 3-D profiles of the water/ice surface, from which the wavelength, frequency, and energy flux are calculated. Alongshore spatial frequency distributions show that pancake and frazil ices differentially attenuate at a greater rate for higher-frequency waves, causing a decrease in mean frequency. In contrast, wave propagation through brash ice causes a rapid increase in the dominant wave frequency, which may be caused by nonlinear energy transfer to higher frequencies due to collisions between the brash ice particles. Consistent to the results in frequency, the wavelengths in pancake and frazil ices increase but decrease in brash ice. The total wave energy fluxes decrease exponentially in both pancake and frazil ice, whereas the overall energy flux remain constant in the brash ice due to thin layer thickness. The spatial energy flux distributions also reveal that wave reflection occurs at the boundary of each ice layer, with reflection coefficient decaying exponentially away from the ice interface. Reflection is the strongest at the pancake/ice-free and frazil/brash interfaces and the weakest at the brash/ice-free interface. These high resolution observations measured by ATSIS demonstrate the spatially variable nature of waves propagating through ice.

  8. Electromagnetic waves in a magnetized plasma near the critical surface

    Energy Technology Data Exchange (ETDEWEB)

    Timofeev, Aleksandr V [Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation)

    2004-06-30

    Electromagnetic waves in a plasma in a magnetic field give rise to enhanced refraction, produce a change in polarization, and cause electromagnetic energy to flow from one wave mode to another when propagating near the critical surface (CS), the one where the electron Langmuir frequency is equal to the wave frequency. A simple unified model of all phenomena taking place near the CS is proposed. These phenomena are due to electromagnetic waves linearly interacting with electron Langmuir oscillations which are localized at the CS in a cold plasma. This interaction manifests itself most strikingly in electron Langmuir oscillation energy escaping directly into a vacuum in the form of electromagnetic radiation. (reviews of topical problems)

  9. Monthly Maps of Sea Surface Height in the North Atlantic and Zonal Indices for the Gulf Stream Using TOPEX/Poseidon Altimeter Data

    Science.gov (United States)

    Singh, Sandipa; Kelly, Kathryn A.

    1997-01-01

    Monthly Maps of sea surface height are constructed for the North Atlantic Ocean using TOPEX/Poseidon altimeter data. Mean sea surface height is reconstructed using a weighted combination of historical, hydrographic data and a synthetic mean obtained by fitting a Gaussian model of the Gulf Stream jet to altimeter data. The resultant mean shows increased resolution over the hydrographic mean, and incorporates recirculation information that is absent in the synthetic mean. Monthly maps, obtained by adding the mean field to altimeter sea surface height residuals, are used to derive a set of zonal indices that describe the annual cycle of meandering as well as position and strength of the Gulf Stream.

  10. Observability of surface currents in p-wave superconductors

    Science.gov (United States)

    Bakurskiy, S. V.; Klenov, N. V.; Soloviev, I. I.; Kupriyanov, M. Yu; Golubov, A. A.

    2017-04-01

    A general approach is formulated to describe spontaneous surface current distribution in a chiral p-wave superconductor. We use the quasiclassical Eilenberger formalism in the Ricatti parametrization to describe various types of the superconductor surface, including arbitrary roughness and metallic behavior of the surface layer. We calculate angle resolved distributions of the spontaneous surface currents and formulate the conditions of their observability. We argue that local measurements of these currents by muon spin rotation technique may provide an information on the underlying pairing symmetry in the bulk superconductor.

  11. Surface waves on a quantum plasma half-space

    CERN Document Server

    Lázár, M; Smolyakov, A

    2007-01-01

    Surface modes are coupled electromagnetic/electrostatic excitations of free electrons near the vacuum-plasma interface and can be excited on a sufficiently dense plasma half-space. They propagate along the surface plane and decay in either sides of the boundary. In such dense plasma models, which are of interest in electronic signal transmission or in some astrophysical applications, the dynamics of the electrons is certainly affected by the quantum effects. Thus, the dispersion relation for the surface wave on a quantum electron plasma half-space is derived by employing the quantum hydrodynamical (QHD) and Maxwell-Poison equations. The QHD include quantum forces involving the Fermi electron temperature and the quantum Bohm potential. It is found that, at room temperature, the quantum effects are mainly relevant for the electrostatic surface plasma waves in a dense gold metallic plasma.

  12. On the retrieval of significant wave heights from spaceborne Synthetic Aperture Radar (ERS-SAR using the Max-Planck Institut (MPI algorithm

    Directory of Open Access Journals (Sweden)

    Violante-Carvalho Nelson

    2005-01-01

    Full Text Available Synthetic Aperture Radar (SAR onboard satellites is the only source of directional wave spectra with continuous and global coverage. Millions of SAR Wave Mode (SWM imagettes have been acquired since the launch in the early 1990's of the first European Remote Sensing Satellite ERS-1 and its successors ERS-2 and ENVISAT, which has opened up many possibilities specially for wave data assimilation purposes. The main aim of data assimilation is to improve the forecasting introducing available observations into the modeling procedures in order to minimize the differences between model estimates and measurements. However there are limitations in the retrieval of the directional spectrum from SAR images due to nonlinearities in the mapping mechanism. The Max-Planck Institut (MPI scheme, the first proposed and most widely used algorithm to retrieve directional wave spectra from SAR images, is employed to compare significant wave heights retrieved from ERS-1 SAR against buoy measurements and against the WAM wave model. It is shown that for periods shorter than 12 seconds the WAM model performs better than the MPI, despite the fact that the model is used as first guess to the MPI method, that is the retrieval is deteriorating the first guess. For periods longer than 12 seconds, the part of the spectrum that is directly measured by SAR, the performance of the MPI scheme is at least as good as the WAM model.

  13. On-surface radiation condition for multiple scattering of waves

    CERN Document Server

    Acosta, Sebastian

    2013-01-01

    The formulation of the on-surface radiation condition (OSRC) is extended to handle wave scattering problems in the presence of multiple obstacles. The new multiple-OSRC simultaneously accounts for the outgoing behavior of the wave fields, as well as, the multiple wave reflections between the obstacles. Like boundary integral equations (BIE), this method leads to a reduction in dimensionality (from volume to surface) of the discretization region. However, as opposed to BIE, the proposed technique leads to boundary integrals with smooth kernels. In addition, under appropriate conditions, this approach leads to approximate explicit (up to numerical integration) formulas for the solution, avoiding the need to invert any operator or matrix. As a result, the computational effort is significantly reduced. This approach may serve as a fast method to explore parameter-spaces or as an inexpensive pre-conditioner for Krylov iterative solutions of BIE.

  14. Langasite surface acoustic wave gas sensors: modeling and verification

    Energy Technology Data Exchange (ETDEWEB)

    Peng Zheng,; Greve, D. W.; Oppenheim, I. J.

    2013-03-01

    We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.

  15. Individually Identifiable Surface Acoustic Wave Sensors, Tags and Systems

    Science.gov (United States)

    Hines, Jacqueline H. (Inventor); Solie, Leland P. (Inventor); Tucker, Dana Y. G. (Inventor); Hines, Andrew T. (Inventor)

    2017-01-01

    A surface-launched acoustic wave sensor tag system for remotely sensing and/or providing identification information using sets of surface acoustic wave (SAW) sensor tag devices is characterized by acoustic wave device embodiments that include coding and other diversity techniques to produce groups of sensors that interact minimally, reducing or alleviating code collision problems typical of prior art coded SAW sensors and tags, and specific device embodiments of said coded SAW sensor tags and systems. These sensor/tag devices operate in a system which consists of one or more uniquely identifiable sensor/tag devices and a wireless interrogator. The sensor device incorporates an antenna for receiving incident RF energy and re-radiating the tag identification information and the sensor measured parameter(s). Since there is no power source in or connected to the sensor, it is a passive sensor. The device is wirelessly interrogated by the interrogator.

  16. SAW devices based on novel surface wave excitations

    Science.gov (United States)

    Therrien, Joel; Dai, Lian

    2015-03-01

    Surface Acoustic Wave (SAW) devices have applications in radio frequency and microwave filtering as well as highly sensitive sensors. Current SAW design employs the use of an array of electrode pairs, referred to as Inter-Digitated Transducers (IDTs) for creating and receiving surface waves on piezoelectric substrates. The pitch of the electrode pairs along with the properties of the substrate determine the operating frequency. The number of electrode pairs determine the bandwidth of the emitted waves. We will present a novel configuration that eliminates the need for the IDTs and replaces with with a single circular electrode located inside a larger ground ring. This configuration induces drumhead modes. We will show that the resonant frequencies follow the zeros of Bessel functions of the first kind. Applications in RF filtering and mass sensing will be presented.

  17. Multiple-frequency surface acoustic wave devices as sensors

    Science.gov (United States)

    Ricco, Antonio J.; Martin, Stephen J.

    We have designed, fabricated, and tested a multiple-frequency acoustic wave (MUFAW) device on ST-cut quartz with nominal surface acoustic wave (SAW) center frequencies of 16, 40, 100, and 250 MHz. The four frequencies are obtained by patterning four sets of input and output interdigital transducers of differing periodicities on a single substrate. Such a device allows the frequency dependence of AW sensor perturbations to be examined, aiding in the elucidation of the operative interaction mechanism(s). Initial measurements of the SAW response to the vacuum deposition of a thin nickel film show the expected frequency dependence of mass sensitivity in addition to the expected frequency independence of the magnitude of the acoustoelectric effect. By measuring changes in both wave velocity and attenuation at multiple frequencies, extrinsic perturbations such as temperature and pressure changes are readily differentiated from one another and from changes in surface mass.

  18. Drops subjected to surface acoustic waves: flow dynamics

    Science.gov (United States)

    Brunet, Philippe; Baudoin, Michael; Bou Matar, Olivier; Dynamique Des Systèmes Hors Equilibre Team; Aiman-Films Team

    2012-11-01

    Ultrasonic acoustic waves of frequency beyond the MHz are known to induce streaming flow in fluids that can be suitable to perform elementary operations in microfluidics systems. One of the currently appealing geometry is that of a sessile drop subjected to surface acoustic waves (SAW). Such Rayleigh waves produce non-trival actuation in the drop leading to internal flow, drop displacement, free-surface oscillations and atomization. We recently carried out experiments and numerical simulations that allowed to better understand the underlying physical mechanisms that couple acoustic propagation and fluid actuation. We varied the frequency and amplitude of actuation, as well as the properties of the fluid, and we measured the effects of these parameters on the dynamics of the flow. We compared these results to finite-elements numerical simulations.

  19. Surface waves in the magnetized, collisional dusty plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, B. P. [Department of Physics, Astronomy and Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney NSW 2109 (Australia); Vladimirov, S. V. [School of Physics, The University of Sydney, Sydney NSW 2006 (Australia); Faculty of Engineering, Yokohama National University, Yokohama 240-8501 (Japan); Metamaterials Laboratory, National Research University of Information Technology, Mechanics, and Optics, St. Petersburg 199034 (Russian Federation); Ishihara, O. [Faculty of Engineering, Yokohama National University, Yokohama 240-8501 (Japan)

    2013-10-15

    The properties of the low frequency surface waves in inhomogeneous, magnetized collisional complex dusty plasma are investigated in this work. The inhomogeneity is modelled by the two distinct regions of the dusty medium with different dust densities. The external magnetic field is assumed to be oriented along the interface dividing the two medium. It is shown that the collisional momentum exchange that is responsible for the relative drift between the plasma particles affects the propagation of the surface waves in the complex plasma via the Hall drift of the magnetic fluctuations. The propagation properties of the sausage and kink waves depend not only on the grain charge and size distribution but also on the ambient plasma thermal conditions.

  20. Langasite Surface Acoustic Wave Gas Sensors: Modeling and Verification

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Peng; Greve, David W; Oppenheim, Irving J

    2013-01-01

    We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.

  1. Tuning Acoustic Wave Properties by Mechanical Resonators on a Surface

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard; Laude, Vincent; Khelif, Abdelkrim

    Vibrations generated by high aspects ratio electrodes are studied by the finite element method. It is found that the modes are combined of a surface wave and vibration in the electrodes. For increasing aspect ratio most of the mechanical energy is confined to the electrodes which act as mechanical...

  2. Monolithic ZnO SAW (Surface Acoustic Waves) structures

    Science.gov (United States)

    Gunshor, R. L.; Pierret, R. F.

    1983-07-01

    ZnO-on-silicon surface acoustic wave devices have been fabricated and tested. Electronic erasure of a stored correlator reference was demonstrated, the effect of laser annealing on propagation loss was examined, preliminary ageing studies were performed, and a conceptually new mode conversion resonator configuration was reported.

  3. Dispersive surface waves along partially saturated porous media

    NARCIS (Netherlands)

    Chao, G.; Smeulders, D.M.J.; Van Dongen, M.E.H.

    2006-01-01

    Numerical results for the velocity and attenuation of surface wave modes in fully permeable liquid/partially saturated porous solid plane interfaces are reported in a broadband of frequencies (100 Hz–1 MHz). A modified Biot theory of poromechanics is implemented which takes into account the interact

  4. Quantitative photography of intermittency in surface wave turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Wright, W.; Budakian, R.; Putterman, S.J. [Univ. of California, Los Angeles, CA (United States)

    1997-12-31

    At high amplitudes of excitation surface waves on water distribute their energy according to a Kolmogorov type of turbulent power spectrum. We have used diffusing light photography to measure the power spectrum and to quantify the presence of large structures in the turbulent state.

  5. On the dependence of sea surface roughness on wind waves

    DEFF Research Database (Denmark)

    Johnson, H.K.; Højstrup, J.; Vested, H.J.;

    1998-01-01

    The influence of wind waves on the momentum transfer (wind stress) between the atmosphere and sea surface was studied using new measured data from the RASEX experiment and other datasets compiled by Donelan et al. Results of the data analysis indicate that errors in wind friction velocity u...

  6. Slow and Steady: Ocean Circulation. The Influence of Sea Surface Height on Ocean Currents

    Science.gov (United States)

    Haekkinen, Sirpa

    2000-01-01

    The study of ocean circulation is vital to understanding how our climate works. The movement of the ocean is closely linked to the progression of atmospheric motion. Winds close to sea level add momentum to ocean surface currents. At the same time, heat that is stored and transported by the ocean warms the atmosphere above and alters air pressure distribution. Therefore, any attempt to model climate variation accurately must include reliable calculations of ocean circulation. Unlike movement of the atmosphere, movement of the ocean's waters takes place mostly near the surface. The major patterns of surface circulation form gigantic circular cells known as gyres. They are categorized according to their general location-equatorial, subtropical, subpolar, and polar-and may run across an entire ocean. The smaller-scale cell of ocean circulation is known' as an eddy. Eddies are much more common than gyres and much more difficult to track in computer simulations of ocean currents.

  7. Surface height adjustments in pyroclastic-flow deposits observed at Unzen volcano by JERS-1 SAR interferometry

    Science.gov (United States)

    Matthews, J. P.; Kamata, H.; Okuyama, S.; Yusa, Y.; Shimizu, H.

    2003-07-01

    Pyroclastic flows from the 1990-1995 eruption of Unzen, a dacitic volcano in the southwest of Japan, descended the mountain along a variety of routes causing widespread damage and loss of life. Interferograms constructed from JERS-1 L-band Synthetic Aperture Radar (SAR) images show a number of features related to these pyroclastic flows and their secondary effects. The most useful interferogram in this respect is based on images acquired on 22 July 1993 and 1 December 1993 and shows the descent paths for pyroclastic flows occurring in four valley systems within this time window as zones of decorrelation caused by the repeated resurfacing. The 22 July 1993 SAR image was, through considerable good fortune, acquired only 2.6 days after a major pyroclastic flow had descended into the Mizunashi valley so that, in the absence of rainfall, the fresh 2-m-thick deposits were dry when first imaged. The largest differential surface height changes observed in the interferogram represent height decreases in the vertical of ˜12 cm and, significantly, lie within a small region of the Mizunashi valley which was resurfaced by the pyroclastic flow of 19 July 1993 but not subsequently. Within this small region, radar coherence is higher (maximum correlation value of ˜0.75) in a center-valley site where ash but relatively few large boulders are present. In a qualitative sense, the new ash surfaces exhibit higher levels of radar coherence than the older (pre-19 July) deposits. In other Unzen valleys visited by pyroclastic flows, smaller differential surface height decreases (˜4 cm) are observed where the surface deposits were emplaced by events taking place between 1-3 months before the acquisition date of the 22 July 1993 image. The 'extra' ˜8 cm of surface height decrease observed in the case of the freshly laid Mizunashi deposits must result from a deflationary mechanism (or mechanisms) operating in a spatially uniform manner in order for radar coherence to be maintained. A

  8. Certification of contact probe measurement of surface wave of Li jet for IFMIF

    Energy Technology Data Exchange (ETDEWEB)

    Okita, Takafumi, E-mail: okita@stu.nucl.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka (Japan); Hoashi, Eiji; Yoshihashi, Sachiko [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka (Japan); Kondo, Hiroo; Kanemura, Takuji [Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki (Japan); Yamaoka, Nobuo; Horiike, Hiroshi [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka (Japan)

    2015-10-15

    Highlights: • We have conducted experiments of liquid lithium free-surface flow for IFMIF. • In the experiment using electro-contact probe apparatus, a droplet of liquid Li on the middle of measurement probe was observed. • Behavior of a droplet and false detections were observed by using HSV camera. • The error of the statistical result was roughly evaluated about 1%. • From results of numerical simulations, we obtained the detailed information about the behavior of a Li droplet. - Abstract: The international fusion material irradiation facility (IFMIF) is a neutron source for developing fusion reactor materials. A liquid lithium (Li) jet with free surface is planned as a target to generate intense neutron field. It is important to obtain information on the surface wave characteristic for safety of the facility and efficient neutron generation. Surface wave characteristics experiment using the liquid Li circulation facility is carried out at Osaka University. In our studies, measurement using an electro-contact probe apparatus is conducted and many data about surface wave height were taken. In this experiment, a liquid Li droplet was observed on the probe. To see effect due to droplets on the probe needle, images near the surface of the Li jet including the Li droplet were taken by HSV camera synchronized with probe contact signals, and correlation between the behavior of the Li droplet and signals was evaluated. From the results, when the droplet on the probe contacts of the droplet with the surface, signals obviously different from the regular signal were observed. The influence on the result of frequency was estimated and is approximately <1%. Accuracy of measurement using probe could be increased by carefully deleting false signals.

  9. Muscle reflexes and synergies triggered by an unexpected support surface height during walking.

    NARCIS (Netherlands)

    Linden, M.H. van der; Marigold, D.S.; Gabreels, F.J.M.; Duysens, J.E.J.

    2007-01-01

    An important phase in the step cycle is foot contact. When the moment of foot contact differs from the one expected, a fast response is needed. Such a mismatch can be caused by hitting a support surface earlier or later than expected. To study this, experiments were performed with healthy young adul

  10. Mixing heights and surface fluxes over Galveston Bay and the Gulf of Mexico: Implications for modeling of pollution episodes

    Science.gov (United States)

    Angevine, W. M.; Tucker, S. C.; Fairall, C.; Bariteau, L.; Wolfe, D.; Zagar, M.; Brewer, A.

    2007-12-01

    During the 2006 Texas Air Quality Study, boundary layer measurements were made by in-situ instruments, lidars, and rawinsondes on the NOAA RV Ronald H. Brown as well as by radar wind profilers on land. Brown also carried instruments to measure surface heat and momentum fluxes. This presentation will emphasize measurements made in Galveston Bay and in the Gulf of Mexico near the Houston area. Details of boundary layer depth and turbulence intensity over these waters have not been well known previously, but are quite important to the understanding of high ozone episodes in Houston. One somewhat surprising result is that the boundary layer over water was almost always slightly unstable, with positive surface heat flux. Mixing depths were moderate, although mixing was generally weak compared to that over land. Boundary layer heights over the water were substantially shallower than daytime heights over land. Experiments in modeling ozone episodes with WRF at 1.5-km grid spacing will be shown and compared with the measurements.

  11. Decay of viscous surface waves without surface tension

    CERN Document Server

    Guo, Yan

    2010-01-01

    Consider a viscous fluid of finite depth below the air. In the absence of the surface tension effect at the air-fluid interface, the long time behavior of a free surface with small amplitude has been an intriguing question since the work of Beale \\cite{beale_1}. In this monograph, we develop a new mathematical framework to resolve this question. If the free interface is horizontally infinite, we establish that it decays to a flat surface at an algebraic rate. On the other hand, if the free interface is periodic, we establish that it decays at an almost exponential rate, i.e. at an arbitrarily fast algebraic rate determined by the smallness of the data. Our framework contains several novel techniques, which include: (1) a local well-posed theory of the Navier-Stokes equations in the presence of a moving boundary; (2) a two-tier energy method that couples the boundedness of high-order energy to the decay of low-order energy, the latter of which is necessary to balance out the growth of the highest derivatives o...

  12. Investigation into Mass Loading Sensitivity of Sezawa Wave Mode-Based Surface Acoustic Wave Sensors

    Directory of Open Access Journals (Sweden)

    N. Ramakrishnan

    2013-02-01

    Full Text Available In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW device is investigated through finite element method (FEM simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered SAW resonator is considered for the simulation study. Initially the occurrence of Sezawa wave mode and displacement amplitude of the Rayleigh and Sezawa wave mode is studied for lower ZnO film thickness. Further, a thin film made of an arbitrary material is coated over the ZnO surface and the resonance frequency shift caused by mass loading of the film is estimated. It was observed that Sezawa wave mode shows significant sensitivity to change in mass loading and has higher sensitivity (eight times higher than Rayleigh wave mode for the same device configuration. Further, the mass loading sensitivity was observed to be greater for a low ZnO film thickness to wavelength ratio. Accordingly, highly sensitive SAW sensors can be developed by coating a sensing medium over a layered SAW device and operating at Sezawa mode resonance frequency. The sensitivity can be increased by tuning the ZnO film thickness to wavelength ratio.

  13. Investigation into mass loading sensitivity of sezawa wave mode-based surface acoustic wave sensors.

    Science.gov (United States)

    Mohanan, Ajay Achath; Islam, Md Shabiul; Ali, Sawal Hamid; Parthiban, R; Ramakrishnan, N

    2013-02-06

    In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW) device is investigated through finite element method (FEM) simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered SAW resonator is considered for the simulation study. Initially the occurrence of Sezawa wave mode and displacement amplitude of the Rayleigh and Sezawa wave mode is studied for lower ZnO film thickness. Further, a thin film made of an arbitrary material is coated over the ZnO surface and the resonance frequency shift caused by mass loading of the film is estimated. It was observed that Sezawa wave mode shows significant sensitivity to change in mass loading and has higher sensitivity (eight times higher) than Rayleigh wave mode for the same device configuration. Further, the mass loading sensitivity was observed to be greater for a low ZnO film thickness to wavelength ratio. Accordingly, highly sensitive SAW sensors can be developed by coating a sensing medium over a layered SAW device and operating at Sezawa mode resonance frequency. The sensitivity can be increased by tuning the ZnO film thickness to wavelength ratio.

  14. Imaging near-surface heterogeneities by natural migration of surface waves

    KAUST Repository

    Liu, Zhaolun

    2016-09-06

    We demonstrate that near-surface heterogeneities can be imaged by natural migration of backscattered surface waves in common shot gathers. No velocity model is required because the data are migrated onto surface points with the virtual Green\\'s functions computed from the shot gathers. Migrating shot gathers recorded by 2D and 3D land surveys validates the effectiveness of detecting nearsurface heterogeneities by natural migration. The implication is that more accurate hazard maps can be created by migrating surface waves in land surveys.

  15. Impact of density information on Rayleigh surface wave inversion results

    Science.gov (United States)

    Ivanov, Julian; Tsoflias, Georgios; Miller, Richard D.; Peterie, Shelby; Morton, Sarah; Xia, Jianghai

    2016-12-01

    We assessed the impact of density on the estimation of inverted shear-wave velocity (Vs) using the multi-channel analysis of surface waves (MASW) method. We considered the forward modeling theory, evaluated model sensitivity, and tested the effect of density information on the inversion of seismic data acquired in the Arctic. Theoretical review, numerical modeling and inversion of modeled and real data indicated that the density ratios between layers, not the actual density values, impact the determination of surface-wave phase velocities. Application on real data compared surface-wave inversion results using: a) constant density, the most common approach in practice, b) indirect density estimates derived from refraction compressional-wave velocity observations, and c) from direct density measurements in a borehole. The use of indirect density estimates reduced the final shear-wave velocity (Vs) results typically by 6-7% and the use of densities from a borehole reduced the final Vs estimates by 10-11% compared to those from assumed constant density. In addition to the improved absolute Vs accuracy, the resulting overall Vs changes were unevenly distributed laterally when viewed on a 2-D section leading to an overall Vs model structure that was more representative of the subsurface environment. It was observed that the use of constant density instead of increasing density with depth not only can lead to Vs overestimation but it can also create inaccurate model structures, such as a low-velocity layer. Thus, optimal Vs estimations can be best achieved using field estimates of subsurface density ratios.

  16. Continuous measurements of water surface height and width along a 6.5km river reach for discharge algorithm development

    Science.gov (United States)

    Tuozzolo, S.; Durand, M. T.; Pavelsky, T.; Pentecost, J.

    2015-12-01

    The upcoming Surface Water and Ocean Topography (SWOT) satellite will provide measurements of river width and water surface elevation and slope along continuous swaths of world rivers. Understanding water surface slope and width dynamics in river reaches is important for both developing and validating discharge algorithms to be used on future SWOT data. We collected water surface elevation and river width data along a 6.5km stretch of the Olentangy River in Columbus, Ohio from October to December 2014. Continuous measurements of water surface height were supplemented with periodical river width measurements at twenty sites along the study reach. The water surface slope of the entire reach ranged from during 41.58 cm/km at baseflow to 45.31 cm/km after a storm event. The study reach was also broken into sub-reaches roughly 1km in length to study smaller scale slope dynamics. The furthest upstream sub-reaches are characterized by free-flowing riffle-pool sequences, while the furthest downstream sub-reaches were directly affected by two low-head dams. In the sub-reaches immediately upstream of each dam, baseflow slope is as low as 2 cm/km, while the furthest upstream free-flowing sub-reach has a baseflow slope of 100 cm/km. During high flow events the backwater effect of the dams was observed to propagate upstream: sub-reaches impounded by the dams had increased water surface slopes, while free flowing sub-reaches had decreased water surface slopes. During the largest observed flow event, a stage change of 0.40 m affected sub-reach slopes by as much as 30 cm/km. Further analysis will examine height-width relationships within the study reach and relate cross-sectional flow area to river stage. These relationships can be used in conjunction with slope data to estimate discharge using a modified Manning's equation, and are a core component of discharge algorithms being developed for the SWOT mission.

  17. Photon management assisted by surface waves on photonic crystals

    CERN Document Server

    Angelini, Angelo

    2017-01-01

    This book illustrates original pathways to manipulate light at the nanoscale by means of surface electromagnetic waves (here, Bloch surface waves, BSWs) on planar dielectric multilayers, also known as one-dimensional photonic crystals. This approach is particularly valuable as it represents an effective alternative to the widely exploited surface plasmon paradigm. After a brief overview on the fundamentals of BSWs, several significant applications of BSW-sustaining structures are described. Particular consideration is given to the propagation, guiding, and diffraction of BSW-coupled radiation. Further, the interaction of organic emitters with BSWs on planar and corrugated multilayers is investigated, including fluorescence beaming in free space. To provide greater insight into sensing applications, an illustrative example of fluorescent microarray-based detection is presented. The book is intended for scientists and researchers working on photon management opportunities in fields such as biosensing, optical c...

  18. Spin density wave order, topological order, and Fermi surface reconstruction

    CERN Document Server

    Sachdev, Subir; Chatterjee, Shubhayu; Schattner, Yoni

    2016-01-01

    In the conventional theory of density wave ordering in metals, the onset of spin density wave (SDW) order co-incides with the reconstruction of the Fermi surfaces into small 'pockets'. We present models which display this transition, while also displaying an alternative route between these phases via an intermediate phase with topological order, no broken symmetry, and pocket Fermi surfaces. The models involve coupling emergent gauge fields to a fractionalized SDW order, but retain the canonical electron operator in the underlying Hamiltonian. We establish an intimate connection between the suppression of certain defects in the SDW order, and the presence of Fermi surface sizes distinct from the Luttinger value in Fermi liquids. We discuss the relevance of such models to the physics of the hole-doped cuprates near optimal doping.

  19. Wavefront modulation of water surface wave by a metasurface

    Institute of Scientific and Technical Information of China (English)

    孙海涛; 程营; 王敬时; 刘晓峻

    2015-01-01

    We design a planar metasurface to modulate the wavefront of a water surface wave (WSW) on a deep sub-wavelength scale. The metasurface is composed of an array of coiling-up-space units with specially designed parameters, and can take on the work of steering the wavefront when it is pierced into water. Like their acoustic counterparts, the modulation of WSW is ascribed to the gradient phase shift of the coiling-up-space units, which can be perfectly tuned by changing the coiling plate length and channel number inside the units. According to the generalized Snell’s law, negative refraction and‘driven’ surface mode of WSW are also demonstrated at certain incidences. Specially, the transmitted WSW could be efficiently guided out by linking a symmetrically-corrugated channel in‘driven’ surface mode. This work may have potential applications in water wave energy extraction and coastal protection.

  20. Seeing the Fields and Forests: Application of Surface-Layer Theory and Flux-Tower Data to Calculating Vegetation Canopy Height

    Science.gov (United States)

    Pennypacker, Sam; Baldocchi, Dennis

    2016-02-01

    Canopy height is an important and dynamic site variable that affects the mass and energy exchanges between vegetation and the atmosphere. We develop a method to estimate canopy height routinely, using surface-layer theory and turbulence measurements made from a collection of flux towers. This tool is based on connecting the logarithmic wind profile generally expected in a neutral surface layer with direct measurements of friction velocity and assumptions about canopy height's relationships with zero-plane displacement and aerodynamic roughness length. Tests over a broad range of canopy types and heights find that calculated values are in good agreement with direct measurements of canopy height, including in a heterogeneous landscape. Based on the various uncertainties associated with our starting assumptions about canopy micrometeorology, we present a blueprint for future work that is necessary for expanding and improving these initial calculations.

  1. Boussinesq modeling of surface waves due to underwater landslides

    CERN Document Server

    Dutykh, Denys

    2013-01-01

    Consideration is given to the influence of an underwater landslide on waves at the surface of a shallow body of fluid. The equations of motion which govern the evolution of the barycenter of the landslide mass include various dissipative effects due to bottom friction, internal energy dissipation, and viscous drag. The surface waves are studied in the Boussinesq scaling, with time-dependent bathymetry. A numerical model for the Boussinesq equations is introduced which is able to handle time-dependent bottom topography, and the equations of motion for the landslide and surface waves are solved simultaneously. The numerical solver for the Boussinesq equations can also be restricted to implement a shallow-water solver, and the shallow-water and Boussinesq configurations are compared. A particular bathymetry is chosen to illustrate the general method, and it is found that the Boussinesq system predicts larger wave run-up than the shallow-water theory in the example treated in this paper. It also found that the fi...

  2. Mode transformation and frequency change with height in 3D numerical simulations of magneto-acoustic wave propagation in sunspots

    CERN Document Server

    Felipe, T; Collados, M

    2010-01-01

    Three-dimensional numerical simulations of magnetoacoustic wave propagation are performed in a sunspot atmosphere with a computational domain covering from the photosphere to the chromosphere. The wave source, with properties resembling the solar spectrum, is located at different distances from the axis of the sunspot for each simulation. These results are compared with the theory of mode transformation and also with observational features. Simulations show that the dominant oscillation frequency in the chromosphere decreases with the radial distance from the sunspot axis. The energy flux of the different wave modes involved, including de Alfv\\'en mode, is evaluated and discussed.

  3. Precessional magnetization switching by a surface acoustic wave

    Science.gov (United States)

    Thevenard, L.; Camara, I. S.; Majrab, S.; Bernard, M.; Rovillain, P.; Lemaître, A.; Gourdon, C.; Duquesne, J.-Y.

    2016-04-01

    Precessional switching allows subnanosecond and deterministic reversal of magnetic data bits. It relies on triggering a large-angle, highly nonlinear precession of magnetic moments around a bias field. Here we demonstrate that a surface acoustic wave (SAW) propagating on a magnetostrictive semiconducting material produces an efficient torque that induces precessional switching. This is evidenced by Kerr microscopy and acoustic behavior analysis in a (Ga,Mn)(As,P) thin film. Using SAWs should therefore allow remote and wave control of individual magnetic bits at potentially GHz frequencies.

  4. Evaluation of multilayered pavement structures from measurements of surface waves

    Science.gov (United States)

    Ryden, N.; Lowe, M.J.S.; Cawley, P.; Park, C.B.

    2006-01-01

    A method is presented for evaluating the thickness and stiffness of multilayered pavement structures from guided waves measured at the surface. Data is collected with a light hammer as the source and an accelerometer as receiver, generating a synthetic receiver array. The top layer properties are evaluated with a Lamb wave analysis. Multiple layers are evaluated by matching a theoretical phase velocity spectrum to the measured spectrum. So far the method has been applied to the testing of pavements, but it may also be applicable in other fields such as ultrasonic testing of coated materials. ?? 2006 American Institute of Physics.

  5. Lagrangian modelling of ocean surface waves and synthetic aperture radar wave measurements

    Energy Technology Data Exchange (ETDEWEB)

    Fouques, Sebastien

    2005-07-01

    The present thesis is concerned with the estimation of the ocean wave spectrum from synthetic aperture radar imaging and the modelling of ocean surface waves using the Lagrangian formalism. The first part gives a short overview of the theories of ocean surface waves and synthetic aperture radar (SAR) whereas the second part consists of five independent publications. The first two articles investigate the influence of the radar backscatter model on the SAR imaging of ocean waves. In Article I, Monte Carlo simulations of SAR images of the ocean surface are carried out using a nonlinear backscatter model that include both specular reflection and Bragg scattering and the results are compared to simulations from the classical Hasselmann integral transform (Hasselmann and Hasselmann, 1991). It is shown that nonlinearities in the backscatter model strongly influence the imaging of range-travelling waves and that the former can suppress the range-splitting effect (Bruning et al., 1988). Furthermore, in Article II a database of Envisat-ASAR Wave Mode products co-located with directional wave spectra from the numerical model WAM and which contains range-travelling wave cases only, is set up. The WAM spectra are used as input to several ocean-to-SAR integral transforms, with various real aperture radar (RAR) models and the obtained SAR image cross-spectra are compared to the Envisat-ASAR observations. A first result is that the use of a linear backscatter model leads to a high proportion of non-physical negative backscatter values in the RAR image, as suggested by Schulz-Stellenfleth (2001). Then, a comparison between the observed SAR cross-spectra and the ones simulated through Hasselmann's integral transform reveals that only twenty percents of the observations show a range-splitting effect as strong as in the simulations. A much better agreement is obtained when using the integral transform by Schulz-Stellenfleth (2003), which is based on a nonlinear hackscatter model

  6. Damping of an ion acoustic surface wave due to surface currents

    CERN Document Server

    Lee, H J

    1999-01-01

    The well-known linear dispersion relation for an ion acoustic surface wave has been obtained by including the linear surface current density J sub z parallel to the interface and by neglecting the linear surface current density J sub x perpendicular to the interface. The neglect of J sub x is questionable although it leads to the popular boundary condition that the tangential electric field is continuous. In this work, linear dispersion relation for an ion acoustic surface wave is worked out by including both components of the linear current density J . When that is done, the ion acoustic wave turns out to be heavily damped. If the electron mass is taken to be zero (electrons are Bolzmann-distributed), the perpendicular component of the surface current density vanishes, and we have the well-known ion acoustic surface wave eigenmode. We conclude that an ion acoustic surface wave propagates as an eigenmode only when its phase velocity is much smaller than the electron thermal velocity.

  7. Observations and Modelling of Winds and Waves During the Surface Wave Dynamics Experiment

    Science.gov (United States)

    1994-03-01

    l’Environnement Terrestre et Planitalre (CRPE), France; Dr. Will M. Drennan, National Water Research Institute, CCIW; Dr. Lynn "Nick" K. Shay, RSMAS; Dr...250 m), and the orbital velocities of the low-frequency surface wave components. A summary of the results from SWADE are described in Shay (1993). 18

  8. A hybrid surface layer parameterization scheme for the two-way fully coupled atmosphere-ocean wave system WEW

    Science.gov (United States)

    Katsafados, Petros; Papadopoulos, Anastasios; Varlas, George; Korres, Gerasimos

    2015-04-01

    The two-way fully coupled atmosphere-ocean wave system WEW has been recently developed in order to study the factors that contribute to the air-sea interaction processes and feedbacks. The coupled system consists of two components: the atmospheric component which is based on the Workstation Eta non-hydrostatic limited area model and the ocean-wave component which is based on the fourth generation OpenMP (OMP) version of the WAM model. The WEW has been already evaluated in a number of high-impact weather and sea state events where generally a more realistic representation of the momentum exchanges in the ocean wind-wave system has been shown However, the new developed wind-wave parameterization scheme reduces both the near surface wind speed and the significant wave height as a response to the increased aerodynamic drag considered by the atmospheric model over rough sea surfaces. Such behavior is mainly attributed to the surface layer parameterization scheme of the atmospheric component which is based on the Mellor-Yamada-Janjic (MYJ) scheme. It is noted that this scheme has been adjusted to support independent atmospheric simulations. Therefore, we proceed to develop a new hybrid surface layer parameterization based on the MYJ and the Janssen schemes that operate in the atmospheric and ocean wave components of the WEW, respectively. In this case the roughness length depends on the wave age instead of the Charnock parameter following the formulation proposed by Vickers and Mahrt. The spatial variability of the wave age is estimated at each ocean wave component time step and it is directly provided to the MYJ scheme. The parameterization of the viscous sublayer and the universal functions for the estimation of the near surface wind speed have been also revised accordingly. In this study, a test version of the new hybrid scheme of WEW has been statistically evaluated against a number of buoys and satellite retrievals over the Mediterranean Sea in a case study of high

  9. Microwave Emission and Scattering from Ocean Surface Waves in the Southern Beaufort Sea

    Directory of Open Access Journals (Sweden)

    Mukesh Gupta

    2014-01-01

    Full Text Available Estimates of the relationships between geophysical variables and microwave backscatter/emission are important for the evaluation of atmosphere-ocean interaction, as well as energy, and mass transfer across this interface. We evaluate ship-based passive microwave brightness temperatures Tb at 37 and 89 GHz and active polarimetric backscatter at 5.5 GHz (C-band, as these relate to buoy-derived ocean wave parameters for distinct wave regimes in the southern Beaufort Sea. Microwave emission and backscatter are shown to be sensitive to the ocean surface physical roughness as defined by the significant wave height Hm0, compared to wind speed. The Tb shows significant correlation with Hm0, with the strongest correlation for the H-polarization channel at 37 and 89 GHz. Active co-γco and cross-γcross polarization ratios at 40° incidence angle are associated with Hm0, with the γco increase proportional to Hm0. The polarimetric coherence parameter ρVVHH at 20° also shows an inverse relationship with Hm0 because of an expected decorrelation of complex returns with greater surface roughness.

  10. Mississippi River and Sea Surface Height Effects on Oil Slick Migration

    Science.gov (United States)

    Falcini, Frederico; Jerolmack, Douglas J.; Buongiorno Nardelli, Bruno

    2012-01-01

    Millions of barrels of oil escaped into the Gulf of Mexico (GoM) after the 20 April, 2010 explosion of Deepwater Horizon (DH). Ocean circulation models were used to forecast oil slick migration in the GoM, however such models do not explicitly treat the effects of secondary eddy-slopes or Mississippi River (MR) hydrodynamics. Here we report oil front migration that appears to be driven by sea surface level (SSL) slopes, and identify a previously unreported effect of the MR plume: under conditions of relatively high river discharge and weak winds, a freshwater mound can form around the MR Delta. We performed temporal oil slick position and altimeter analysis, employing both interpolated altimetry data and along-track measurements for coastal applications. The observed freshwater mound appears to have pushed the DH oil slick seaward from the Delta coastline. We provide a physical mechanism for this novel effect of the MR, using a two-layer pressure-driven flow model. Results show how SSL variations can drive a cross-slope migration of surface oil slicks that may reach velocities of order km/day, and confirm a lag time of order 5–10 days between mound formation and slick migration, as observed form the satellite analysis. Incorporating these effects into more complex ocean models will improve forecasts of slick migration for future spills. More generally, large SSL variations at the MR mouth may also affect the dispersal of freshwater, nutrients and sediment associated with the MR plume. PMID:22558317

  11. Lagrangian modelling of ocean surface waves and synthetic aperture radar wave measurements

    Energy Technology Data Exchange (ETDEWEB)

    Fouques, Sebastien

    2005-07-01

    The present thesis is concerned with the estimation of the ocean wave spectrum from synthetic aperture radar imaging and the modelling of ocean surface waves using the Lagrangian formalism. The first part gives a short overview of the theories of ocean surface waves and synthetic aperture radar (SAR) whereas the second part consists of five independent publications. The first two articles investigate the influence of the radar backscatter model on the SAR imaging of ocean waves. In Article I, Monte Carlo simulations of SAR images of the ocean surface are carried out using a nonlinear backscatter model that include both specular reflection and Bragg scattering and the results are compared to simulations from the classical Hasselmann integral transform (Hasselmann and Hasselmann, 1991). It is shown that nonlinearities in the backscatter model strongly influence the imaging of range-travelling waves and that the former can suppress the range-splitting effect (Bruning et al., 1988). Furthermore, in Article II a database of Envisat-ASAR Wave Mode products co-located with directional wave spectra from the numerical model WAM and which contains range-travelling wave cases only, is set up. The WAM spectra are used as input to several ocean-to-SAR integral transforms, with various real aperture radar (RAR) models and the obtained SAR image cross-spectra are compared to the Envisat-ASAR observations. A first result is that the use of a linear backscatter model leads to a high proportion of non-physical negative backscatter values in the RAR image, as suggested by Schulz-Stellenfleth (2001). Then, a comparison between the observed SAR cross-spectra and the ones simulated through Hasselmann's integral transform reveals that only twenty percents of the observations show a range-splitting effect as strong as in the simulations. A much better agreement is obtained when using the integral transform by Schulz-Stellenfleth (2003), which is based on a nonlinear hackscatter model

  12. Comparative study of binding constants from Love wave surface acoustic wave and surface plasmon resonance biosensors using kinetic analysis.

    Science.gov (United States)

    Lee, Sangdae; Kim, Yong-Il; Kim, Ki-Bok

    2013-11-01

    Biosensors are used in a variety of fields for early diagnosis of diseases, measurement of toxic contaminants, quick detection of pathogens, and separation of specific proteins or DNA. In this study, we fabricated and evaluated the capability of a high sensitivity Love wave surface acoustic wave (SAW) biosensor. The experimental setup was composed of the fabricated 155-MHz Love wave SAW biosensor, a signal measurement system, a liquid flow system, and a temperature-control system. Subsequently, we measured the lower limit of detection (LOD) of the 155-MHz Love wave SAW biosensor, and calculated the association and dissociation constants between protein G and anti-mouse IgG using kinetic analysis. We compared these results with those obtained using a commercial surface plasmon resonance (SPR) biosensor. We found that the LOD of the SAW biosensor for anti-mouse IgG and mouse IgG was 0.5 and 1 microg/ml, respectively, and the resultant equilibrium association and dissociation constants were similar to the corresponding values obtaining using the commercial SPR biosensor. Thus, we conclude that the fabricated 155-MHz Love wave SAW biosensor exhibited the high sensitivity of the commercial SPR biosensor and was able to analyze the binding properties of the ligand and receptor by kinetic analysis similarly to the commercial SPR biosensor.

  13. Adaptive re-tracking algorithm for retrieval of water level variations and wave heights from satellite altimetry data for middle-sized inland water bodies

    Science.gov (United States)

    Troitskaya, Yuliya; Lebedev, Sergey; Soustova, Irina; Rybushkina, Galina; Papko, Vladislav; Baidakov, Georgy; Panyutin, Andrey

    by the improved threshold algorithm. The possibility of determination of significant wave height (SWH) in the lakes through a two-step adaptive retracking is also studied. Calculation of the parameter SWH for Gorky Reservoir from May 2010 to March 2014 showed the anomalously high values of SWH, derived from altimetry data [15], which means that the calibration of this SWH for inland waters is required. Calibration ground measurements were performed at Gorky reservoir in 2011-2013, when wave height, wind speed and air temperature were collected by equipment placed on a buoy [15] collocated with Jason-1 and Jason-2 altimetry data acquisition. The results obtained on the basis of standard algorithm and method for adaptive re-tracking at Rybinsk , Gorky , Kuibyshev , Saratov and Volgograd reservoirs and middle-sized lakes of Russia: Chany, Segozero, Hanko, Oneko, Beloye, water areas of which are intersected by the Jason-1,2 tracks, were compared and their correlation with the observed data of hydrological stations in reservoirs and lakes was investigated. It was noted that the Volgograd reservoir regional re-tracking to determine the water level , while the standard GDR data are practically absent. REFERENCES [1] AVISO/Altimetry. User Handbook. Merged TOPEX/ POSEIDON Products. Edition 3.0. AVISO. Toulouse., 1996. [2] C.M. Birkett et al., “Surface water dynamics in the Amazon Basin: Application of satellite radar altimetry,” J. Geophys. Res., vol. 107, pp. 8059, 2002. [3] G. Brown, “The average impulse response of a rough surface and its applications,” IEEE Trans. Antennas Propagat., vol. 25, pp. 67-74, 1977. [4] I.O. Campos et al., “Temporal variations of river basin waters from Topex/Poseidon satellite altimetry. Application to the Amazon basin,” Earth and Planetary Sciences, vol. 333, pp. 633-643, 2001. [5] A.V. Kouraev et al., “Ob’ river discharge from TOPEX/Poseidon satellite altimetry (1992-2002),” Rem. Sens. Environ., vol. 93, pp. 238-245, 2004

  14. Optimization of Surface Acoustic Wave-Based Rate Sensors

    Directory of Open Access Journals (Sweden)

    Fangqian Xu

    2015-10-01

    Full Text Available The optimization of an surface acoustic wave (SAW-based rate sensor incorporating metallic dot arrays was performed by using the approach of partial-wave analysis in layered media. The optimal sensor chip designs, including the material choice of piezoelectric crystals and metallic dots, dot thickness, and sensor operation frequency were determined theoretically. The theoretical predictions were confirmed experimentally by using the developed SAW sensor composed of differential delay line-oscillators and a metallic dot array deposited along the acoustic wave propagation path of the SAW delay lines. A significant improvement in sensor sensitivity was achieved in the case of 128° YX LiNbO3, and a thicker Au dot array, and low operation frequency were used to structure the sensor.

  15. Waves on the surface of the Orion molecular cloud.

    Science.gov (United States)

    Berné, Olivier; Marcelino, Núria; Cernicharo, José

    2010-08-19

    Massive stars influence their parental molecular cloud, and it has long been suspected that the development of hydrodynamical instabilities can compress or fragment the cloud. Identifying such instabilities has proved difficult. It has been suggested that elongated structures (such as the 'pillars of creation') and other shapes arise because of instabilities, but alternative explanations are available. One key signature of an instability is a wave-like structure in the gas, which has hitherto not been seen. Here we report the presence of 'waves' at the surface of the Orion molecular cloud near where massive stars are forming. The waves seem to be a Kelvin-Helmholtz instability that arises during the expansion of the nebula as gas heated and ionized by massive stars is blown over pre-existing molecular gas.

  16. Biological decontamination of surfaces using guided ionization waves

    Science.gov (United States)

    Jarrige, Julien; Zaepffel, Clement

    2016-09-01

    Atmospheric pressure plasma jets have received an increasing attention these last ten years in various domains, including biomedical applications and decontamination. Among these technologies, guided ionization waves (also called ``plasma bullets'') are very promising because of their ability to produce a highly non-equilibrium plasma. Reactive species can be generated in the open air over a long distance during the propagation of the wave (typically: several cm), while the background gas remains at ambient temperature. A non-thermal plasma system has been developed and tested for the biological decontamination of surfaces. It consists of a dielectric barrier discharge in a helium flow driven by high voltage pulses. The propagation of the ionization wave and the spatial distribution of the species have been characterized by high speed imaging and optical emission spectroscopy. The influence of the discharge parameters on the plasma properties is investigated. Results of decontamination on several bacteria are shown, and the decontamination efficiency is compared with the plasma properties.

  17. Surface wave dynamics in orbital shaken cylindrical containers

    Science.gov (United States)

    Reclari, M.; Dreyer, M.; Tissot, S.; Obreschkow, D.; Wurm, F. M.; Farhat, M.

    2014-05-01

    Be it to aerate a glass of wine before tasting, to accelerate a chemical reaction, or to cultivate cells in suspension, the "swirling" (or orbital shaking) of a container ensures good mixing and gas exchange in an efficient and simple way. Despite being used in a large range of applications this intuitive motion is far from being understood and presents a richness of patterns and behaviors which has not yet been reported. The present research charts the evolution of the waves with the operating parameters identifying a large variety of patterns, ranging from single and multiple crested waves to breaking waves. Free surface and velocity fields measurements are compared to a potential sloshing model, highlighting the existence of various flow regimes. Our research assesses the importance of the modal response of the shaken liquids, laying the foundations for a rigorous mixing optimization of the orbital agitation in its applications.

  18. Surface wave dynamics in orbital shaken cylindrical containers

    CERN Document Server

    Reclari, Martino; Tissot, Stéphanie; Obreschkow, Danail; Wurm, Florian Maria; Farhat, Mohamed

    2014-01-01

    Be it to aerate a glass of wine before tasting, to accelerate a chemical reaction or to cultivate cells in suspension, the "swirling" (or orbital shaking) of a container ensures good mixing and gas exchange in an efficient and simple way. Despite being used in a large range of applications this intuitive motion is far from being understood and presents a richness of patterns and behaviors which has not yet been reported. The present research charts the evolution of the waves with the operating parameters identifying a large variety of patterns, ranging from single and multiple crested waves to breaking waves. Free surface and velocity fields measurements are compared to a potential sloshing model, highlighting the existence of various flow regimes. Our research assesses the importance of the modal response of the shaken liquids, laying the foundations for a rigorous mixing optimization of the orbital agitation in its applications. Copyright (2014) American Institute of Physics. This article may be downloaded ...

  19. Identification of Swell in Nearshore Surface Wave Energy Spectra

    Directory of Open Access Journals (Sweden)

    Paul A. Work

    2010-06-01

    Full Text Available An approach for routine identification of swell and sea in nominally fully developed, omnidirectional, surface water wave energy spectra measured in arbitrary water depth is developed, applied, and discussed. The methodology is an extension of earlier work with deepwater spectra and involves identifying the frequency at which wave steepness is maximized and relating this to the swell separation frequency. The TMA parameterized spectrum is employed to establish a relationship between the two frequencies so that the methodology can be used when wind data are unavailable. The methodology is developed for finite water depth and tested using a dataset that includes both acoustic Doppler current profiler and wave buoy data, recorded simultaneously at the same location. For cases where the sea and swell are clearly, visually distinguishable in the omnidirectional spectra, the new method accurately distinguishes between the two, but it can also be used to identify sea and swell in unimodal spectra.

  20. Bohm potential effect on the propagation of electrostatic surface wave in semi-bounded quantum plasmas

    Science.gov (United States)

    Lee, Myoung-Jae; Jung, Young-Dae

    2017-02-01

    High frequency electrostatic wave propagation in a dense and semi-bounded electron quantum plasma is investigated with consideration of the Bohm potential. The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. We found that the quantum effect enhances the frequency of the wave especially in the high wave number regime. However, the frequency of surface wave is found to be always lower than that of the bulk wave for the same quantum wave number. The group velocity of the surface wave for various quantum wave number is also obtained.

  1. Surface acoustic waves enhance neutrophil killing of bacteria.

    Science.gov (United States)

    Loike, John D; Plitt, Anna; Kothari, Komal; Zumeris, Jona; Budhu, Sadna; Kavalus, Kaitlyn; Ray, Yonatan; Jacob, Harold

    2013-01-01

    Biofilms are structured communities of bacteria that play a major role in the pathogenicity of bacteria and are the leading cause of antibiotic resistant bacterial infections on indwelling catheters and medical prosthetic devices. Failure to resolve these biofilm infections may necessitate the surgical removal of the prosthetic device which can be debilitating and costly. Recent studies have shown that application of surface acoustic waves to catheter surfaces can reduce the incidence of infections by a mechanism that has not yet been clarified. We report here the effects of surface acoustic waves (SAW) on the capacity of human neutrophils to eradicate S. epidermidis bacteria in a planktonic state and within biofilms. Utilizing a novel fibrin gel system that mimics a tissue-like environment, we show that SAW, at an intensity of 0.3 mW/cm(2), significantly enhances human neutrophil killing of S. epidermidis in a planktonic state and within biofilms by enhancing human neutrophil chemotaxis in response to chemoattractants. In addition, we show that the integrin CD18 plays a significant role in the killing enhancement observed in applying SAW. We propose from out data that this integrin may serve as mechanoreceptor for surface acoustic waves enhancing neutrophil chemotaxis and killing of bacteria.

  2. Surface acoustic waves enhance neutrophil killing of bacteria.

    Directory of Open Access Journals (Sweden)

    John D Loike

    Full Text Available Biofilms are structured communities of bacteria that play a major role in the pathogenicity of bacteria and are the leading cause of antibiotic resistant bacterial infections on indwelling catheters and medical prosthetic devices. Failure to resolve these biofilm infections may necessitate the surgical removal of the prosthetic device which can be debilitating and costly. Recent studies have shown that application of surface acoustic waves to catheter surfaces can reduce the incidence of infections by a mechanism that has not yet been clarified. We report here the effects of surface acoustic waves (SAW on the capacity of human neutrophils to eradicate S. epidermidis bacteria in a planktonic state and within biofilms. Utilizing a novel fibrin gel system that mimics a tissue-like environment, we show that SAW, at an intensity of 0.3 mW/cm(2, significantly enhances human neutrophil killing of S. epidermidis in a planktonic state and within biofilms by enhancing human neutrophil chemotaxis in response to chemoattractants. In addition, we show that the integrin CD18 plays a significant role in the killing enhancement observed in applying SAW. We propose from out data that this integrin may serve as mechanoreceptor for surface acoustic waves enhancing neutrophil chemotaxis and killing of bacteria.

  3. Mississippi River and sea surface height effects on oil slick migration.

    Directory of Open Access Journals (Sweden)

    Frederico Falcini

    Full Text Available Millions of barrels of oil escaped into the Gulf of Mexico (GoM after the 20 April, 2010 explosion of Deepwater Horizon (DH. Ocean circulation models were used to forecast oil slick migration in the GoM, however such models do not explicitly treat the effects of secondary eddy-slopes or Mississippi River (MR hydrodynamics. Here we report oil front migration that appears to be driven by sea surface level (SSL slopes, and identify a previously unreported effect of the MR plume: under conditions of relatively high river discharge and weak winds, a freshwater mound can form around the MR Delta. We performed temporal oil slick position and altimeter analysis, employing both interpolated altimetry data and along-track measurements for coastal applications. The observed freshwater mound appears to have pushed the DH oil slick seaward from the Delta coastline. We provide a physical mechanism for this novel effect of the MR, using a two-layer pressure-driven flow model. Results show how SSL variations can drive a cross-slope migration of surface oil slicks that may reach velocities of order km/day, and confirm a lag time of order 5-10 days between mound formation and slick migration, as observed form the satellite analysis. Incorporating these effects into more complex ocean models will improve forecasts of slick migration for future spills. More generally, large SSL variations at the MR mouth may also affect the dispersal of freshwater, nutrients and sediment associated with the MR plume.

  4. Effect of roughness lengths on surface energy and the planetary boundary layer height over high-altitude Ngoring Lake

    Science.gov (United States)

    Li, Zhaoguo; Lyu, Shihua; Wen, Lijuan; Zhao, Lin; Meng, Xianhong; Ao, Yinhuan

    2017-08-01

    The special climate environment creates a distinctive air-lake interaction characteristic in the Tibetan Plateau (TP) lakes, where the variations of surface roughness lengths also differ somewhat from those of other regions. However, how different categories of roughness lengths affect the lake surface energy exchange and the planetary boundary layer height (PBLH) remains unclear in the TP lakes. In this study, we used a tuned Weather Research and Forecasting (WRF) model version 3.6.1 to investigate the responses of the freeze-up date, turbulent fluxes, meteorological variables, and PBLH to surface roughness length variations in Ngoring Lake. Of all meteorological variables, the lake surface temperature responded to roughness length variations most sensitively; increasing roughness lengths can put the lake freeze-up date forward. The effect of momentum roughness length on wind speed was significantly affected by the fetch length. The increase in the roughness length for heat can induce the increment of the nightly PBLH in most months, especially for the central lake area in autumn. The primary factors that contribute to sensible heat flux (H) and latent heat flux (LE) were the roughness lengths for heat and momentum during the ice-free period, respectively. Increasing roughness length for heat can increase the nightly PBLH, and decreasing roughness length for moisture can also promote growth of the PBLH, but there was no obvious correlation between the momentum roughness length and the PBLH.

  5. A Japanese New Altimetry Mission, COMPIRA - Towards High Temporal and Spatial Sampling of Sea Surface Height Measurement

    Science.gov (United States)

    Ito, N.; Uematsu, A.; Yajima, Y.; Isoguchi, O.

    2014-12-01

    Japan Aerospace Exploration Agency (JAXA) is working on a conceptual study of altimeter mission named Coastal and Ocean measurement Mission with Precise and Innovative Radar Altimeter (COMPIRA), which will carry a wide-swath altimeter named Synthetic aperture radar (SAR) Height Imaging Oceanic Sensor with Advanced Interferometry (SHIOSAI). Capturing meso/submeso-scale phenomena is one of important objectives of the COMPIRA mission, as well as operational oceanography and fishery. For operational oceanography including coastal forecast, swath of SHIOSAI is selected to be 80 km in left and right sides to maximize temporal and spatial sampling of the sea surface height. Orbit specifications are also designed to be better sampling especially for mid-latitude region. That is, a spatial grid sampling is 5 km and an observation times per revisit period (about 10 days) is 2 to 3 times. In order to meet both sampling frequency and spatial coverage requirements as much as possible, orbit inclination was set relatively low, 51 degrees. Although this sampling frequency is, of course, not enough high to capture time evolution of coastal phenomena, an assimilation process would compensate its time evolution if 2D SSH fields was observed at least once within decal time scale of phenomena. JAXA has launched a framework called "Coastal forecast core team" to aim at developing coastal forecast system through pre-launch activities toward COMPIRA. Assimilation segment as well as satellite and in situ data provision will play an important role on these activities. As a first step, we evaluated effects of ocean current forecast improvement with COMPIRA-simulated wide-swath and high sampling sea surface heights (SSH) data. Simulated SSH data are generated from regional ocean numerical models and the COMPIRA orbit and error specifications. Then, identical twin experiments are conducted to investigate the effect of wide-swath SSH measurements on coastal forecast in the Tohoku Pacific coast

  6. Cluster observations of surface waves on the dawn flank magnetopause

    Directory of Open Access Journals (Sweden)

    C. J. Owen

    2004-03-01

    Full Text Available On 14 June 2001 the four Cluster spacecraft recorded multiple encounters of the dawn-side flank magnetopause. The characteristics of the observed electron populations varied between a cold, dense magnetosheath population and warmer, more rarified boundary layer population on a quasi-periodic basis. The demarcation between these two populations can be readily identified by gradients in the scalar temperature of the electrons. An analysis of the differences in the observed timings of the boundary at each spacecraft indicates that these magnetopause crossings are consistent with a surface wave moving across the flank magnetopause. When compared to the orientation of the magnetopause expected from models, we find that the leading edges of these waves are approximately 45° steeper than the trailing edges, consistent with the Kelvin-Helmholtz (KH driving mechanism. A stability analysis of this interval suggests that the magnetopause is marginally stable to this mechanism during this event. Periods in which the analysis predicts that the magnetopause is unstable correspond to observations of greater wave steepening. Analysis of the pulses suggests that the waves have an average wavelength of approximately 3.4 RE and move at an average speed of ~65km s-1 in an anti-sunward and northward direction, despite the spacecraft location somewhat south of the GSE Z=0 plane. This wave propagation direction lies close to perpendicular to the average magnetic field direction in the external magnetosheath, suggesting that these waves may preferentially propagate in the direction that requires no bending of these external field lines

    Key words. Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and unstabilities; solar wind-magnetosphere interactions

  7. Surface Wave Propagation in non--ideal plasmas

    CERN Document Server

    Pandey, B P

    2015-01-01

    The properties of surface waves in a partially ionized, compressible magnetized plasma slab are investigated in this work. The waves are affected by the nonideal magnetohydrodynamic effects which causes finite drift of the magnetic field in the medium. When the magnetic field drift is ignored, the characteristics of the wave propagation in a partially ionized plasma fluid is similar to the fully ionized ideal MHD except now the propagation properties depend on the fractional ionization as well as on the compressibility of the medium. The phase velocity of the sausage and kink waves increases marginally (by a few percent) due to the compressibility of the medium in both ideal as well as Hall diffusion dominated regimes. However, unlike ideal regime, only waves below certain cut off frequency can propagate in the medium in Hall dominated regime. This cut off for a thin slab has a weak dependence on the plasma beta whereas for thick slab no such dependence exists. More importantly, since the cut off is introduce...

  8. Turbulence-particle interactions under surface gravity waves

    Science.gov (United States)

    Paskyabi, Mostafa Bakhoday

    2016-11-01

    The dispersion and transport of single inertial particles through an oscillatory turbulent aquatic environment are examined numerically by a Lagrangian particle tracking model using a series of idealised test cases. The turbulent mixing is incorporated into the Lagrangian model by the means of a stochastic scheme in which the inhomogeneous turbulent quantities are governed by a one-dimensional k- ɛ turbulence closure scheme. This vertical mixing model is further modified to include the effects of surface gravity waves including Coriolis-Stokes forcing, wave breaking, and Langmuir circulations. To simplify the complex interactions between the deterministic and the stochastic phases of flow, we assume a time-invariant turbulent flow field and exclude the hydrodynamic biases due to the effects of ambient mean current. The numerical results show that the inertial particles acquire perturbed oscillations traced out as time-varying sinking/rising orbits in the vicinity of the sea surface under linear and cnoidal waves and acquire a non-looping single arc superimposed with the high-frequency fluctuations beneath the nonlinear solitary waves. Furthermore, we briefly summarise some recipes through the course of this paper on the implementation of the stochastic particle tracking models to realistically describe the drift and suspension of inertial particles throughout the water column.

  9. Optical biosensors based on photonic crystal surface waves.

    Science.gov (United States)

    Konopsky, Valery N; Alieva, Elena V

    2009-01-01

    Optical biosensors have played a key role in the selective recognition of target biomolecules and in biomolecular interaction analysis, providing kinetic data about biological binding events in real time without labeling. The advantages of the label-free concept are the elimination of detrimental effects from labels that may interfere with fundamental interaction and the absence of a time-consuming pretreatment. The disadvantages of all label-free techniques--including the most mature one, surface plasmon resonance (SPR) technique, are a deficient sensitivity to a specific signal and undesirable susceptibilities to non-specific signals, e.g., to the volume effect of refraction index variations. These variations arise from temperature fluctuations and drifts and they are the limiting factor for many state-of-the-art optical biosensors. Here we describe a new optical biosensor technique based on the registration of dual optical s-polarized waves on a photonic crystal surface. The simultaneous registration of two different optical modes from the same surface spot permits the segregation of the volume and the surface signals, while the absence of metal damping permits an increase in the propagation length of the optical surface waves and the sensitivity of the biosensor. The technique was tested with the binding of biotin molecules to a streptavidin monolayer that has been detected with a signal/noise ratio of about 15 at 1 s signal accumulation time. The detection limit is about 20 fg of the analyte on the probed spot of the surface.

  10. Surface water waves due to an oscillatory wavemaker in the presence of surface tension

    Directory of Open Access Journals (Sweden)

    B. N. Mandal

    1992-01-01

    Full Text Available The initial value problem of generation of surface water waves by a harmonically oscillating plane vertical wavemaker in an infinite incompressible fluid under the action of gravity and surface tension is investigated. In the asymptotic evaluation of the free surface depression for large time and distance, the contribution to the integral by stationary phase method gives rise to transient component of the free surface depression while the contribution from the poles give rise to steady state component. It is observed that the presence of surface tension sometimes changes the qualitative nature of the transient component of free surface depression.

  11. Spin wave absorber generated by artificial surface anisotropy for spin wave device network

    Science.gov (United States)

    Kanazawa, Naoki; Goto, Taichi; Sekiguchi, Koji; Granovsky, Alexander B.; Takagi, Hiroyuki; Nakamura, Yuichi; Inoue, Mitsuteru

    2016-09-01

    Spin waves (SWs) have the potential to reduce the electric energy loss in signal processing networks. The SWs called magnetostatic forward volume waves (MSFVWs) are advantageous for networking due to their isotropic dispersion in the plane of a device. To control the MSFVW flow in a processing network based on yttrium iron garnet, we developed a SW absorber using artificial structures. The mechanical surface polishing method presented in this work can well control extrinsic damping without changing the SW dispersion of the host material. Furthermore, enhancement of the ferromagnetic resonance linewidth over 3 Oe was demonstrated.

  12. Wave-equation dispersion inversion of surface waves recorded on irregular topography

    KAUST Repository

    Li, Jing

    2017-08-17

    Significant topographic variations will strongly influence the amplitudes and phases of propagating surface waves. Such effects should be taken into account, otherwise the S-velocity model inverted from the Rayleigh dispersion curves will contain significant inaccuracies. We now show that the recently developed wave-equation dispersion inversion (WD) method naturally takes into account the effects of topography to give accurate S-velocity tomograms. Application of topographic WD to demonstrates that WD can accurately invert dispersion curves from seismic data recorded over variable topography. We also apply this method to field data recorded on the crest of mountainous terrain and find with higher resolution than the standard WD tomogram.

  13. Nonlinear mixing of laser generated narrowband Rayleigh surface waves

    Science.gov (United States)

    Bakre, Chaitanya; Rajagopal, Prabhu; Balasubramaniam, Krishnan

    2017-02-01

    This research presents the nonlinear mixing technique of two co-directionally travelling Rayleigh surface waves generated and detected using laser ultrasonics. The optical generation of Rayleigh waves on the specimen is obtained by shadow mask method. In conventional nonlinear measurements, the inherently small higher harmonics are greatly influenced by the nonlinearities caused by coupling variabilities and surface roughness between the transducer and specimen interface. The proposed technique is completely contactless and it should be possible to eliminate this problem. Moreover, the nonlinear mixing phenomenon yields not only the second harmonics, but also the sum and difference frequency components, which can be used to measure the acoustic nonlinearity of the specimen. In this paper, we will be addressing the experimental configurations for this technique. The proposed technique is validated experimentally on Aluminum 7075 alloy specimen.

  14. Nonlinear surface waves in soft, weakly compressible elastic media.

    Science.gov (United States)

    Zabolotskaya, Evgenia A; Ilinskii, Yurii A; Hamilton, Mark F

    2007-04-01

    Nonlinear surface waves in soft, weakly compressible elastic media are investigated theoretically, with a focus on propagation in tissue-like media. The model is obtained as a limiting case of the theory developed by Zabolotskaya [J. Acoust. Soc. Am. 91, 2569-2575 (1992)] for nonlinear surface waves in arbitrary isotropic elastic media, and it is consistent with the results obtained by Fu and Devenish [Q. J. Mech. Appl. Math. 49, 65-80 (1996)] for incompressible isotropic elastic media. In particular, the quadratic nonlinearity is found to be independent of the third-order elastic constants of the medium, and it is inversely proportional to the shear modulus. The Gol'dberg number characterizing the degree of waveform distortion due to quadratic nonlinearity is proportional to the square root of the shear modulus and inversely proportional to the shear viscosity. Simulations are presented for propagation in tissue-like media.

  15. Surface wave and linear operating mode of a plasma antenna

    Energy Technology Data Exchange (ETDEWEB)

    Bogachev, N. N., E-mail: bgniknik@yandex.ru; Bogdankevich, I. L.; Gusein-zade, N. G.; Rukhadze, A. A. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

    2015-10-15

    The relation between the propagation conditions of a surface electromagnetic wave along a finiteradius plasma cylinder and the linear operating mode of a plasma antenna is investigated. The solution to the dispersion relation for a surface wave propagating along a finite-radius plasma cylinder is analyzed for weakly and strongly collisional plasmas. Computer simulations of an asymmetrical plasma dipole antenna are performed using the KARAT code, wherein the dielectric properties of plasma are described in terms of the Drude model. The plasma parameters corresponding to the linear operating mode of a plasma antenna are determined. It is demonstrated that the characteristics of the plasma antenna in this mode are close to those of an analogous metal antenna.

  16. Surface Catalytic Mechanism in Square-Wave Voltammetry

    OpenAIRE

    Mirceski, Valentin; Gulaboski, Rubin

    2001-01-01

    A pseudo-first-order catalytic mechanism in which both reactant and product of the redox reaction are strongly immobilized on the electrode surface is theoretically analyzed under conditions of square-wave voltammetry (SWV). A mathematical procedure is developed for diffusionless conditions. The relationships between the properties of the voltammetric response and both the kinetic parameters of the redox reaction and the parameters of the excitement signal are studied. The phenomenon...

  17. Laser ablation method for production of surface acoustic wave sensors

    Science.gov (United States)

    Lukyanov, Dmitry; Shevchenko, Sergey; Kukaev, Alexander; Safronov, Daniil

    2016-10-01

    Nowadays surface acoustic wave (SAW) sensors are produced using a photolithography method. In case of inertial sensors it suffers several disadvantages, such as difficulty in matching topologies produced on opposite sides of the wafer, expensive in small series production, not allowing further topology correction. In this case a laser ablation method seems promising. Details of a proposed technique are described in the paper along with results of its experimental test and discussion.

  18. Surface acoustic wave probe implant for predicting epileptic seizures

    Science.gov (United States)

    Gopalsami, Nachappa [Naperville, IL; Kulikov, Stanislav [Sarov, RU; Osorio, Ivan [Leawood, KS; Raptis, Apostolos C [Downers Grove, IL

    2012-04-24

    A system and method for predicting and avoiding a seizure in a patient. The system and method includes use of an implanted surface acoustic wave probe and coupled RF antenna to monitor temperature of the patient's brain, critical changes in the temperature characteristic of a precursor to the seizure. The system can activate an implanted cooling unit which can avoid or minimize a seizure in the patient.

  19. Slippery Liquid-Infused Porous Surfaces and Droplet Transportation by Surface Acoustic Waves

    Science.gov (United States)

    Luo, J. T.; Geraldi, N. R.; Guan, J. H.; McHale, G.; Wells, G. G.; Fu, Y. Q.

    2017-01-01

    On a solid surface, a droplet of liquid will stick due to the capillary adhesion, and this causes low droplet mobility. To reduce contact line pinning, surface chemistry can be coupled to micro- and/or nanostructures to create superhydrophobic surfaces on which a droplet balls up into an almost spherical shape, thus, minimizing the contact area. Recent progress in soft matter has now led to alternative lubricant-impregnated surfaces capable of almost zero contact line pinning and high droplet mobility without causing droplets to ball up and minimize the contact area. Here we report an approach to surface-acoustic-wave- (SAW) actuated droplet transportation enabled using such a surface. These surfaces maintain the contact area required for efficient energy and momentum transfer of the wave energy into the droplet while achieving high droplet mobility and a large footprint, therefore, reducing the threshold power required to induce droplet motion. In our approach, we use a slippery layer of lubricating oil infused into a self-assembled porous hydrophobic layer, which is significantly thinner than the SAW wavelength, and avoid damping of the wave. We find a significant reduction (up to 85%) in the threshold power for droplet transportation compared to that using a conventional surface-treatment method. Moreover, unlike droplets on superhydrophobic surfaces, where interaction with the SAW induces a transition from a Cassie-Baxter state to a Wenzel state, the droplets on our liquid-impregnated surfaces remain in a mobile state after interaction with the SAW.

  20. Elastic friction drive of surface acoustic wave motor.

    Science.gov (United States)

    Kurosawa, Minoru Kuribayashi; Itoh, Hidenori; Asai, Katsuhiko

    2003-06-01

    Importance of elastic deformation control to obtain large output force with a surface acoustic wave (SAW) motor is discussed in this paper. By adding pre-load to slider, stator and slider surfaces are deformed in a few tens nanometer. Appropriate deformation in normal direction against normal vibration displacement amplitude of SAW existed. By moderate deformation, the output force of the SAW motor was enlarged up to about 10 N and no-load speed was 0.7 m/s. To produce this performance, the transducer weight and slider size were only 4.2 g and 4 x 4 mm(2).By traveling wave propagation, surface particles of the SAW device move in elliptical motion. Due to the amplitude of the elliptical motion is 10 or 20 nm order, the contact condition of the slider is very critical. To control the contact condition, namely, the elastic deformation of the slider and stator surface in nanometer order, a lot of projections were fabricated on the slider surface. The projection diameter was 20 micro m. In static condition, the elastic deformation and stress were evaluated with the FEM analysis. From this calculation and the simulation result, it is consider that the wave crest is distorted, hence the elasticity has influence on the friction drive condition. Elastic deformation of the stator surface beneath the projection from the initial position were evaluated. In 4 x 4 mm(2) square area, the sliders had from 1089 to 23,409 projections. Depression was independent to the contact pressure. However, the output force depended on the depression although the projection density were different. From the view point of the output power of the motor, the proper depression was independent to the projection density. Around 25 nm depression, the output force and output power were maximized. This depression value was almost same as the vibration displacement amplitude of the stator transducer.