scholarly journals EXPERIMENTAL STUDY OF WIND WAVES GENERATED ON CURRENTS

1978 ◽  
Vol 1 (16) ◽  
pp. 42
Author(s):  
Hajime Kato ◽  
Hiroichi Tsuruya
Keyword(s):  
Wind Wave ◽  
Wind Waves ◽  
Water Current ◽  
Pump System ◽  
Frequency Wave ◽  
Wave Channel ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
True Frequency ◽  
The Waves

This paper presents some experimental results of wind waves generated on currents in a wind-wave channel with a water circulation pump system. The waves were measured at fetches less than 27.8 m by using resistance-type wave gauges. Surface velocities as well as velocity profiles in water were also measured elaborately and true frequency wave spectra were obtained from observed apparent spectra which were modified by the doppler effect of current. Significant wave heights Hwj computed from r)2 and peak frequencies of true spectra fprn were examined with emphasis. It was inferred from the variation of true spectra that the most prominent effect of water current is to change the effective fetch length. Then an idea of equivalent fetch length was proposed to express the current effect on the development of total wave energy. By using the equivalent fetch F' in place of the natural fetch it is shown that Hj/3 and fQm measured under various current conditions can be represented by the non-dimensional fetch relations, respectively, which were originally obtained in the case of no current.

scholarly journals Impact of the Reduced Drag Coefficient on Ocean Wave Modeling under Hurricane Conditions

2008 ◽  
Vol 136 (3) ◽  
pp. 1217-1223 ◽  
Author(s):  
Il-Ju Moon ◽  
Isaac Ginis ◽  
Tetsu Hara
Keyword(s):  
Drag Coefficient ◽  
Hurricane Katrina ◽  
Wind Wave ◽  
Wave Model ◽  
High Wind ◽  
Model Surface ◽  
Wind Speeds ◽  
Tank Experiment ◽  
Wave Heights ◽  
Significant Wave Heights

Abstract Effects of new drag coefficient (Cd) parameterizations on WAVEWATCH III (WW3) model surface wave simulations are investigated. The new parameterizations are based on a coupled wind–wave model (CWW) and a wave tank experiment, and yields reduced Cd at high wind speeds. Numerical experiments for uniform winds and Hurricane Katrina (2005) indicate that the original Cd parameterization used in WW3 overestimates drag at high wind speeds compared to recent observational, theoretical, and numerical modeling results. Comparisons with buoy measurements during Hurricane Katrina demonstrate that WW3 simulations with the new Cd parameterizations yield more accurate significant wave heights compared to simulations with the original Cd parameterization, provided that accurate high-resolution wind forcing fields are used.

scholarly journals Analysis of extreme wave events in the southern coast of Brazil

2014 ◽  
Vol 2 (6) ◽  
pp. 4363-4391 ◽  
Author(s):  
P. V. Guimarães ◽  
L. Farina ◽  
E. Toldo
Keyword(s):  
Urban Areas ◽  
Rio Grande ◽  
Rio Grande Do Sul ◽  
Extreme Wave ◽  
Point Of Interest ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Buoy Data ◽  
The Waves ◽  
Good Agreement

Abstract. Using the model SWAN, high waves on the Southwestern Atlantic generated by extra-tropical cyclones are simulated from 2000 to 2010 and their impact on the Rio Grande do Sul coast is studied. The modeled waves are compared with buoy data and good agreement is found. The six extreme events in the period which presented significant wave heights above 5 m, on a particular point of interest, are investigated in detail. It is found that the cyclogenetic pattern between the latitudes 31.5 and 34° S, is the most favorable for developing high waves. Hovmöller diagrams for deep water show that the region between the south of Rio Grande do Sul up to latitude 31.5° S is the most energetic during a cyclone's passage, although the event of May 2008 indicate that the location of this region can vary, depending on the cyclone's displacement. On the oher hand, the Hovmöller diagrams for shallow water show that the different shoreface morphologies were responsable for focusing or dissipating the waves' energy; the regions found are in agreement with the observations of erosion and progradation regions. It can be concluded that some of the urban areas of the beaches of Hermenegildo, Cidreira, Pinhal, Tramandaí, Imbé and Torres have been more exposed during the extreme wave events at Rio Grande do Sul coast, and are more vulnerable to this natural hazard.

scholarly journals UPWIND TRAVEL OF REFLECTED WAVES

1968 ◽  
Vol 1 (11) ◽  
pp. 14
Author(s):  
E.P. Richey
Keyword(s):  
Wind Waves ◽  
Full Scale Test ◽  
Deep Lake ◽  
Reflected Waves ◽  
Wind Speeds ◽  
Wave Characteristics ◽  
Wave Heights ◽  
Scale Test ◽  
Floating Bridges ◽  
The Waves

Wind waves in a lake have been observed to reflect from a barrier and to travel upwind for considerable distances. A model has been devised which provides a means of predicting the decay of these waves as a function of wind speed and direction with respect to the barrier. Two floating bridges across a deep lake have formed a convenient, full-scale test basin for the formation and observation of the reflected waves under a range of wind speeds and directions. Wave characteristics have been measured to a limited extent by photographic means, a portable wave probe and visually to provide seme verification of the results computed from the model. The measured and the predicted wave heights and the zones influenced by the waves were found to be in general qualitative agreement.

scholarly journals Temporal Variability of the Wind Wave Parameters in the Baltic Sea in 1979–2018 Based on the Numerical Modeling Results

2020 ◽  
Vol 27 (4) ◽  
Author(s):  
A. N. Sokolov ◽  
◽  
B. V. Chubarenko ◽  
◽  
Keyword(s):  
Baltic Sea ◽  
Temporal Variability ◽  
Wind Wave ◽  
Statistical Significance ◽  
The Baltic Sea ◽  
Significant Wave ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
The Baltic ◽  
Sea Area

Purpose. The aim of the paper is to identify possible trends in the wave climate dynamics in the Baltic Sea, and to analyze statistical significance of the coefficients of these trends based on the results of their numerical modeling for 1979–2018. Methods and Results. The simulations for 1979–2018 (40 years) were carried out on an irregular grid using the MIKE 21 SW spectral wave model. The wind forcing was preset according to the ERA-Interim reanalysis data. The model was calibrated and validated against the data of wave buoys located in the northern and southern parts of the Baltic Sea. Based on the calibrated model, the wind wave parameters were calculated for the whole Baltic Sea area from 1979 to 2018 with the interval 1 hour. These parameters became the initial data for estimating temporal variability of the wind wave heights in the Baltic Sea for 40 years. The simulation results obtained on the irregular grid were interpolated to the regular one. It permitted to construct the maps of distribution of the maximum and average (for the 40-year period) significant wave heights in the Baltic Sea. The time trends for the average annual significant wave height values were revealed, and statistical significance of the coefficients of these trends was estimated. Conclusions. The average annual values of the significant wave heights over almost the whole Baltic Sea area for 1979–2018 (40 years) tend to decrease with the rate not exceeding 2–3 cm (2–3 %) per 10 years. The highest rate reduction is observed in the southeastern part of the Baltic Sea, the lowest – in the Gulf of Bothnia and the Gulf of Finland. Interannual variability of the average annual significant wave heights and the changes along the trend during the entire 40-years period are of the same order.

Wind-induced growth of water waves

1982 ◽  
Vol 123 ◽  
pp. 425-442 ◽  
Author(s):  
H. Mitsuyasu ◽  
T. Honda
Keyword(s):  
Growth Rate ◽  
Water Waves ◽  
Friction Velocity ◽  
Wind Wave ◽  
Wind Waves ◽  
Pure Water ◽  
Wave Flume ◽  
Wind Speeds ◽  
Wind Profiles ◽  
The Waves

Spatial growth of mechanically generated water waves under the action of wind has been measured in a laboratory wind-wave flume both for pure water and for water containing a surfactant (sodium lauryl sulphate, concentration 2.6 × 10−2%). I n the latter case, no wind waves develop on the surface of the mechanically generated waves as well as on the still water surface for wind speeds up to U10≈ 15 m/s, where U10 is the wind velocity at the height Z = 10 m. Therefore we can study the wind-induced growth of monochromatic waves without the effects of co-existing short wind waves. The mechanically generated waves grew exponentially under the action of the wind, with fetch in both cases. The measured growth rate β for the pure water can be fitted by β/f = 0.34(U*/C)2 0.1 [lsime ] U*/C [lsime ] 1.0, where f is the frequency of the waves, C is the corresponding phase velocity, and U, is the friction velocity obtained from vertical wind profiles. The effect of the wave steepness H/L on the dimensionless growth rate β/f is not clear, but seems to be small. For water containing the surfactant, the measured growth rate is smaller than that for pure water, but the friction velocity of the wind is also small, and the above relation between β/f and U*/C holds approximately if the measured friction velocity U* is used for the relation.

scholarly journals The rate of the turbulence dissipation in a water layer under wind waves based on the data of laboratory experiment

2019 ◽  
Vol 55 (5) ◽  
pp. 126-136
Author(s):  
V. G. Polnikov ◽  
G. A. Baidakov ◽  
Yu. I. Troitskaya
Keyword(s):  
Friction Velocity ◽  
Wind Wave ◽  
Wind Waves ◽  
Vertical Component ◽  
Water Layer ◽  
Peak Frequency ◽  
Laboratory Measurements ◽  
Kolmogorov Type ◽  
Frequency Spectra ◽  
Wave Channel

The aim of the work is to obtain estimates and parameterization of the dissipation rate of the turbulence kinetic energy of (TKE-dissipation) in the upper water layer, induced by the presence of wind waves at the surface. For this purpose, data from the laboratory measurements of the wind waves and three components of currents at six horizons in the upper water layer and four different winds, performed in the wind-wave channel of IAP RAS [1, 2], were used. It was established that for a majority of horizons, the frequency spectra, SUz( f ), for the vertical component of the flow velocity, Uz, induced by wind and waves, have the Kolmogorov-type ranges of the kind: Using the algorithms described in [3, 4], this fact allows us to obtain estimates of the TKE-dissipation at the corresponding horizons, and then establish the dependence of on the friction velocity, u*, the height of waves at the surface, a0, the peak frequency of the spectrum, p, and the depth of the horizon, z. The analysis of the obtained results allows (for the available data) to propose a parameterization of the form 0.00025 for which a physical interpretation is proposed.

EFFECTS OF AN OIL SLICK ON WIND WAVES1

1979 ◽  
Vol 1979 (1) ◽  
pp. 665-674 ◽  
Author(s):  
Hsien-Ta Liu ◽  
Jung-Tai Lin
Keyword(s):  
Wave Breaking ◽  
Wind Wave ◽  
Wind Waves ◽  
Ocean Waves ◽  
Diesel Oil ◽  
Wave Tank ◽  
Oil Slick ◽  
Wave Profiles ◽  
The Waves ◽  
Integrated Program

ABSTRACT Laboratory experiments were performed to investigate the effects of an oil slick on ocean waves. This is part of an integrated program aimed at understanding the vertical dispersion of oil in the upper ocean. The experiments were conducted in a wind-wave tank which measured 9.1 m long, 1.2 m wide, and 1.8 m deep. Both wind waves and mechanically-generated waves with wind were considered. No. 2 Diesel oil was fed at a rate of 0.35 liters/sec onto the water surface from the upstream end of the wave tank. To measure the wave profiles, an optical sensor-photodiode wave gauge was developed and is described herein. The effects of an oil slick on wind waves were examined in terms of wave profiles and rms wave amplitudes. For wind waves, the presence of the oil slick damps the waves significantly. The amount of damping increases with the wind speed in the range from U∞ = 4 m/sec to 10 m/sec. At U∞ = 10 m/sec, the oil slick breaks into small lenses. The rms amplitudes of the wind-generated waves increase with the fetch without the oil slick, but they do not change appreciably in the presence of the oil slick. For mechanically-generated waves with wind, wave damping by the oil slick becomes insignificant when the waves are sufficiently steep and wave breaking occurs. Prior to wave breaking, however, steepening of the wave crests due to the presence of the oil slick has been observed occasionally as a result of the reduction in the surface tension by the oil film.

Numerical Simulation for Typhoon and Wave of Qiongzhou Strait

2016 ◽  
Author(s):  
Yanan Xu
Keyword(s):  
Southern China ◽  
Numerical Models ◽  
Wave Model ◽  
Numerical Approach ◽  
Wind Speeds ◽  
Qiongzhou Strait ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
The Waves ◽  
Simulated Wind

Southern China has been subject to some of the deadliest typhoons in history with records going back over a thousand years. Before the large waves associated with a typhoon reach the mainland of China there is a delay between the typhoon reaching landfall and the time of the extreme waves arriving. This paper focuses on an approach to simulate this lag in the waves reaching landfall in the Qiongzhou Strait in southern China. A numerical approach has been adopted to simulate the typhoon and wave processes using a parametric typhoon model and the SWAN wave model. Two typhoon events are simulated (typhoon Kai-Tak in 2012 and typhoon Jebi in 2013) and used to tune the parameters for the numerical models. The simulated wind speeds and significant wave heights of the typhoon are compared with measured data. For the simulation of typhoon Kai-Tak, the correlation coefficient gives an 87% agreement between the simulated and measured values of wave height with a standard deviation of 0.29 m. For typhoon Jebi the fit is less good (66%). However, the simulation results have provided insight into improving the parametric typhoon model.

scholarly journals THE CHARACTERISTICS OF WIND-WAVES GENERATED IN THE LABORATORY

1968 ◽  
Vol 1 (11) ◽  
pp. 4
Author(s):  
Theodore E. Lee
Keyword(s):  
Wind Wave ◽  
Wind Waves ◽  
Ocean Waves ◽  
Coastal Engineering ◽  
Wave Period ◽  
Zero Crossing ◽  
Wave Data ◽  
Wave Characteristics ◽  
Significant Correction ◽  
Wave Heights

Wind-wave characteristics were recorded in the laboratory for the primary purposes of (a) analysis of the probability distribution of wave height and wave period with wind speed, water depth, and fetch length as major parameters, and (b) comparison of the test results with existing theory and empirical formulae. An important aspect of this study was to test the validity of the Tucker and Draper method (Draper, 1966) for the presentation of ocean wave data as applicable to wave-data analysis for simulated wind waves. It was interesting to note that some corrections were necessary when the method proposed by Draper at the 10th Coastal Engineering Conference was used for analyzing waves generated in the laboratory. Approximately a positive 20% correction was necessary for this study in which the wave spectra distribution is of very narrow range, the wave width parametere = V1-(T /T ) varles from 0.25 to 0.50, where Tc and T2 represent crest wave period ana zero-crossing wave period, respectively. However, only a negative 5% correction was necessary when the method was used to analyze sea waves (e = 0 73 to 0 76) measured off the shoreline near Look Laboratory Therefore, it was concluded that the Tucker and Draper Method is quite feasible for engineering purposes in analyzing wind-waves having a spectral width parameter of 0.60 to 0.75 The experimental data were compared with those wave heights predicted by the Darbyshire formulas (Francis, 1959) developed for ocean waves. A significant correction factor was necessary for laboratory waves produced by low-speed wi nds. The "fetch graph" was prepared and compared with those developed theoretically by Hino (1966) and empirically by Ijima and Tang (1966) at the 10th Conference on Coastal Engineering, Tokyo, Japan Comparison was also made with the previous empirical formulae by Bretschneider (1951, 1957), Sverdrup and Munk (1947), and Wilson (1961,1962). The experimental results compared well with the Hino theory for both wave heights and wave periods, and fairly well with Bretschneider's fetch graph for wave heights The difference in the comparison of wave data with other investigators is illustrated in this paper. It is recommended that further study be made with emphasis on (a) theoretical and experimental studies of wind-wave characteristics on pre-existing waves, particularly moving storms, (b) wave-energy spectra involving stochastic characteristics and extreme values of wind waves

scholarly journals Analysis of extreme wave events on the southern coast of Brazil

2014 ◽  
Vol 14 (12) ◽  
pp. 3195-3205 ◽  
Author(s):  
P. V. Guimarães ◽  
L. Farina ◽  
E. E. Toldo Jr.
Keyword(s):  
Urban Areas ◽  
Rio Grande ◽  
Wave Model ◽  
Rio Grande Do Sul ◽  
Extreme Wave ◽  
Point Of Interest ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Buoy Data ◽  
The Waves

Abstract. Using the wave model SWAN (simulating waves nearshore), high waves on the southwestern Atlantic generated by extra-tropical cyclones are simulated from 2000 to 2010, and their impact on the Rio Grande do Sul (RS) coast is studied. The modeled waves are compared with buoy data and good agreement is found. The six extreme events in the period that presented significant wave heights above 5 m, on a particular point of interest, are investigated in detail. It is found that the cyclogenetic pattern between the latitudes 31.5 and 34° S is the most favorable for developing high waves. Hovmöller diagrams for deep water show that the region between the south of Rio Grande do Sul up to a latitude of 31.5° S is the most energetic during a cyclone's passage, although the event of May 2008 indicates that the location of this region can vary, depending on the cyclone's displacement. On the other hand, the Hovmöller diagrams for shallow water show that the different shoreface morphologies were responsible for focusing or dissipating the waves' energy; the regions found are in agreement with the observations of erosion and progradation regions. It can be concluded that some of the urban areas of the beaches of Hermenegildo, Cidreira, Pinhal, Tramandaí, Imbé and Torres have been more exposed during the extreme wave events on the Rio Grande do Sul coast, and are more vulnerable to this natural hazard.

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