Masoud Mahmoudof - Academia.edu (original) (raw)

Papers by Masoud Mahmoudof

Science of The Total Environment

International Journal of coastal and offshore engineering

In this study, a simple and efficient approach based on nonlinear wave interaction fundamentals i... more In this study, a simple and efficient approach based on nonlinear wave interaction fundamentals is theoretically proposed to generate surface profile of the cnoidal waves. The approach includes Newton-Raphson algorithm to calculate the Ursell parameter and using a simple formulation to attain time series of cnoidal waves profile. The wave profile is determined as a superposition of limited number of cosine harmonics without encountering difficulties of using elliptic or hyperbolic functions, or any complex and complicated differential equations. It is demonstrated that a cnoidal wave profile is a result of high order self nonlinear interactions of primary frequency. Some definite energy is transmitted to higher harmonics due to nonlinear interactions. The amount of transmitted energy is controlled by Ursell parameter. The desirable accuracy determines the number of included harmonics in the proposed formulation and relative error of approach can be predicted based on Fourier and least square analysis techniques. The outputs of the proposed method are verified with cnoidal resulted from elliptic functions and the high efficiency of new approximation is revealed for engineering applications. The calculation of wave parameters such as energy flux, volume flux and radiation stress for cnoidal wave can be approximated using the proposed method. Using this approach, a physical interpretation of the Bm parameter (introduced in the first order of cnoidal wave theory) is presented. The calculation of several parameters such as velocity vectors and dynamic pressure of cnoidal waves is very simple by means of proposed approach.

Applied Ocean Research, 2021

Abstract The present study analyzes the field measurements of the reflective response of a permea... more Abstract The present study analyzes the field measurements of the reflective response of a permeable rubble mound breakwater encountered with a bimodal wave regime. The coexistence of sea and swell wind-driven waves during the measurement program provided directional spreading wave realizations for subsequent bulk and frequency-dependent wave reflection analysis. The directional wave data were acquired near the primary breakwater of Chabahar Port within 28 days, including 643 bursts using an AWAC wave recorder. The available formulae for wave reflection coefficient were evaluated against this data set. Results showed that the equations proposed by Postma (1989) and Zanuttigh and Van der Meer (2007) are in general agreement with the observations of the present study. However, the accuracy of reflection coefficient predictions was improved by developing two new alternative formulations. It was realized that the frequency reflective response differs between sea and swell prevailing conditions. The reflection coefficient decreases drastically within high sea wave predominant periods for the harmonics higher than peak frequency. However, reflection coefficients of high harmonics reduced slightly within swell domination periods. The frequency-dependent reflection coefficients can be even higher than unity due to energy transfer amongst other wave harmonics.

Journal of Oceanography, 2019

In this study, the compound and overtide constituents resulted from nonlinear triad interactions ... more In this study, the compound and overtide constituents resulted from nonlinear triad interactions were evaluated using Bispectral method at the eastern Iranian coasts of Makran. It was found that the most significant compound constituents at the studies area were KO2, KP2, MS4 and MN4. Also, the overtides of M4 and S4 were detectable by means of implemented method. The superiority of Bispectral method comparing with least square method (harmonic analysis) is in recognizing some of compound tides such as KO2, which is never identifiable using least square method. The corresponding Fourier harmonic frequencies to main tidal constituents were identified by comparing the results of the least square method and the Fourier analysis. Finally, the analysis was performed with d.o.f.s of 16, 32 and 64. The repeated significant bicoherence values in all three d.o.f.s and in the main tidal constituent frequencies range were regarded as the intensive and effective interactions.

Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هول... more Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هولا م ی نا هت د هبهب یداهیز بش رد ی ه زاهس ی رهب د همن به ام همد مها ک رد دا هما ا ی ا ااهجنا هی ن هسررب ی ، جا هما ی رد امز ی هاوهن رد و 3 ، همد 3 رپ ه ی د و 3 ل ت تاهفترا هی درگ ه ی بش اه ب و ی ه زاهس ی ن د هد ل هم رد اهه ی SWAN هه ب اقم ی هس ل ت د هم تادافترا هی امز رد ه هش ی هاوهن ارهب هش ههتتادرپ ل هم و ی ا ااهجنا هی ن اقم ی ههس ه ا رتماراهپ ود ی رد د هج م ی هولا تهسکش Thornton و Guza ه تخم ت اهم رد لاها ی هرب ره هها هش هداد ناهنن و ن هش هی ک زا ا ی ن م ههچ ت ام هی ناز بش رد ار د هبهب ی ه زاهس ی ل ت دا هما هی ی امز رد ی هاوهن د هد ل هم هس ت ی SWAN به ام یهم هنا اهن رد هی ت ارهب ی ا ه ا هی ن رتماراهپ ود ، ر و هطبا ی پ ی داهنهن درگ هی ن لاهمدا اهب هها د هد ل هم رد اهه ی

Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هول... more Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هولا م ی نا هت د هبهب یداهیز بش رد ی ه زاهس ی رهب د همن به ام همد مها ک رد دا هما ا ی ا ااهجنا هی ن هسررب ی ، جا هما ی رد امز ی هاوهن رد و 3 ، همد 3 رپ ه ی د و 3 ل ت تاهفترا هی درگ ه ی بش اه ب و ی ه زاهس ی ن د هد ل هم رد اهه ی SWAN هه ب اقم ی هس ل ت د هم تادافترا هی امز رد ه هش ی هاوهن ارهب هش ههتتادرپ ل هم و ی ا ااهجنا هی ن اقم ی ههس ه ا رتماراهپ ود ی رد د هج م ی هولا تهسکش Thornton و Guza ه تخم ت اهم رد لاها ی هرب ره هها هش هداد ناهنن و ن هش هی ک زا ا ی ن م ههچ ت ام هی ناز بش رد ار د هبهب ی ه زاهس ی ل ت دا هما هی ی امز رد ی هاوهن د هد ل هم هس ت ی SWAN به ام یهم هنا اهن رد هی ت ارهب ی ا ه ا هی ن رتماراهپ ود ، ر و هطبا ی پ ی داهنهن درگ هی ن لاهمدا اهب هها د هد ل هم رد اهه ی

Oceanologia, 2021

Abstract This paper presents the results of a laboratory experiment on transmission, reflection, ... more Abstract This paper presents the results of a laboratory experiment on transmission, reflection, and dissipation of irregular waves over smooth impermeable submerged breakwaters. Experiments included 75 JONSWAP-based irregular waves with five different wave characteristics generated at three water depths in a 2D wave flume. The investigated breakwater sections were three rectangular breakwaters with different widths, a toothed rectangular breakwater, and a trapezoidal breakwater with a slope of 1:2. A new comprehensive dimensionless parameter (β) was proposed representing both wave hydrodynamic and breakwater geometry characteristics. This parameter could be employed as a suitable descriptive option to make an accurate estimate of the hydraulic performances of submerged breakwaters. The β parameter is composed of four conventional simple dimensionless variables. However, the results revealed that the relative submergence depth significantly affects the hydraulic responses of submerged breakwaters. The transmission, reflection and dissipation of waves show a logarithmic growth, a logarithmic reduction, and a quadratic decreasing trend against the increasing of β parameter, respectively. The verifications of results revealed the high efficiency of β parameter for data reported by Carevic et al. (2013) with R2 = 0.88 and high agreement with predictions made by Van der Meer et al. (2005) formulation with R2 = 0.93.

Ocean Engineering, 2021

Abstract This study experimentally investigates the development and decay of bound energy fractio... more Abstract This study experimentally investigates the development and decay of bound energy fractions due to positive and negative interactions (b2p and b2n, respectively) applying bispectral analysis. It was revealed that the Ursell number is the most successful parameter to estimate the variation patterns of b2p and b2n. The experimental waves included 27 waves with three offshore wave heights, three periods, and three offshore water depths propagating over a mild slope of 1:30. A wide variety of wave nonlinearity and bound coupling intensities were observed across the experimental dissipative surf zone. For a wave propagating toward the shore, the corresponding Ursell numbers for the relative maximum values of b2p and b2n are 0.27 and 0.22, respectively. The ratio of significant wave height to water depth corresponding to these extreme values for positive and negative triads are ~0.4 and ~0.32, respectively. The highest values of b2p and b2n for a progressive wave can be predicted as a function of the Ursell number using two new proposed experimental formulations. The sub-harmonics are more persistent during wave-breaking conditions than super-harmonics due to lower wave steepness. The biphase values of self-coupling of the spectral peak are attained negative for waves with Ursell numbers greater than 0.35.

Estuarine, Coastal and Shelf Science, 2021

Abstract This study analyzed the characteristics of infragravity waves (hereafter IGWs) based on ... more Abstract This study analyzed the characteristics of infragravity waves (hereafter IGWs) based on field observations collected near the plunging cliffs of Chabahar bay, Iran. Observations were made near Chabahar city during the summer monsoon season of 2018. The wave climate included two different durations of sea and swell predominance, with a maximum wave height reaching 2.5 m. Concurrent with the duration of the sea predominance, the ratio of IGW to swell wave height had an insensitive fluctuation against tidal variations, while this ratio had a strong negative correlation with tidal level during the high swell condition. The investigation of directional wave energy distribution revealed two correlated trends of shoreward and seaward IGWs with the wave regime. Larger values of the IGW reflection coefficients were observed during high sea wave conditions compared with high swell conditions. The IGW reflection coefficients decreased against swell energy growth with a logarithmic trend. The bound IGW energy fraction was studied using bispectral analysis. It is demonstrated that the maximum values of this parameter corresponded to high swell waves observed within low ebbs of the spring tide. The insignificant values of bound IGW energy fraction and the non-extended surf-zone revealed that most of the released IGWs originated from offshore and intermediate water depths. In addition, it was revealed that the inverse tidal trend of normalized IGW by swell height was due to bound IGW enhancement during ebb periods as a result of the nonlinear coupling of swell waves.

Applied Ocean Research, 2020

In this study, a linear formulation is found to estimate the wave reflection coefficient (K r) fr... more In this study, a linear formulation is found to estimate the wave reflection coefficient (K r) from plunging cliff coasts of Chabahar city according to field data measurements. The field measurement included directional wave data via three bursts for each hour and in total 1345 bursts during summer Southern-West monsoon using an ADCP gague. The significant wave heights reached 2.5 m and the corresponding peak periods were greater than 11 s. It was observed that the wave reflection coefficients are fully tidally modulated. The maximum values of K r reached 0.7 in a flood period of spring tide, while the minimum values were greater than 0.3 and corresponded to ebb periods in spring tide. The corresponding dimensionless parameters of wave height to depth, wave steepness and Ursell number to the highest values of K r were obtained as 0.17, 0.014, and 22, respectively. The variation ranges of reflection coefficient pertaining to the effect of four main tidal constituents as M2, S2, K1, and O1 were achieved as ∼ 9.6, 4.1, 7.1, and 3.6%, respectively. Finally, a linear formulation as a function of the tidal level was resulted to estimate the most accurate values of K r in the studied area. The averaged inaccuracy of resulted formulation was approximately 6.5%. The frequency reflection coefficients K r (f) was also investigated in this study. The results indicated the values close to 1 for long infragravity waves, because of occurrence of no significant dissipation. However, the similar values for short waves (fr > 0.25 Hz) were greater than 1 due to wind wave breaking as a result of the cliff toe collision. The temporal histogram of K r (f) revealed the tidally controlled variations of this parameter.

Applied Ocean Research, 2020

This paper presents the results of bound infragravity observation at the Nowshahr beach located i... more This paper presents the results of bound infragravity observation at the Nowshahr beach located in the southern part of the Caspian Sea. The water level data were measured at 6 stations along a transect perpendicular to the coastline. The bispectral method was utilized to show that the extreme values for the bound infragravity energy fraction (b ii) were occurring when dimensionless values of wave height to depth ratio, relative depth, and wave steepness were in the range of 0.18-0.22, 0.4-0.5 and 0.015-0.017, respectively. These detailed results could be equivalently summarized with the condition of having the Ursell number of peak waves within the range of 30-40. The corresponding short wave groupiness factor (G.F.) values for waves with high values of b ii were between 0.5 and 0.55. Also, it was revealed that the wave groupiness envelope had a positive correlation with infragravity wave energy level, but its correlation with the bound infragravity wave was negative when G.F. > 0.55. On the other hand, the low values of b ii against the spectrum peakedness parameter for breaking waves followed an exponential relationship. The correlation of bound and free infragravity waves with wind waves was also studied. For non-breaking condition, the correlations of bound infragravity waves with swell and sea waves were considerable. The correlation of free waves with swells was also significant. In contrast, for breaking waves, a negligible correlation was observed between bound infragravity waves and wind waves. o o 1/2 and H T o p 2

Journal of Marine Science and Application, 2018

This study evaluates the capability of the Simulating WAves Nearshore (SWAN) wave model (version ... more This study evaluates the capability of the Simulating WAves Nearshore (SWAN) wave model (version 41.01) in predicting significant wave height and spectral peak energy content for swell waves in very shallow water of surf zone during depth-induced wave breaking and dissipation. The model results were compared with field measurements at five nearshore stations. The results demonstrated that some breaker index formulations were successful for significant wave height prediction in surf zones. However, an incorrect shape of the energy spectrum and overestimated near spectral peak energy content at shallow water stations were obtained using all of the embedded depth-induced wave breaking formulations in SWAN. The dependent breaker index on relative depth (K p d) formulation, which was successful in predicting near spectral peak energy content, resulted in an average error of 30%. Finally, this formulation was modified to enhance the model performance in reproducing the spectral peak energy content.

Journal of Oceanography, 2018

In this study, the laboratory observations were accomplished for 36 random and irregular waves in... more In this study, the laboratory observations were accomplished for 36 random and irregular waves initiated according to the JONSWAP spectrum to study the impotance of energy transition to low and high frequency harmonics due to wave breaking in the outer surf-zone. The wave transformation was investigated using two trinary groups of pressure sensors at the beginning and end of ramp with the slope of 1:16. The maximum observed transferred energy due to wave breaking was about 22% of dissipated energy which was equal to 9% of total energy of the primary wave. In this manner, the prediced significant broken wave height was 8% underestimated using phased avraged wave models. The observations indicated the fraction of dissipated energy, which was transferred to low and high frequencies growth with increment of primary wave Ursell parameter at the initial depth.

International Journal of Maritime Technology, 2017

Cross-shore sediment transport is one of the effective factors in erosion and sedimentation, and ... more Cross-shore sediment transport is one of the effective factors in erosion and sedimentation, and affects dynamics of the beach profile in coastal areas. Furthermore, sandbar migration due to cross-shore sediment transport mostly effects beach nourishment, displacement of pollutions trapped in sediments, and organism and plants' lives. In this manuscript, sandbar migration due to cross-shore sediment transport is studied and results have been compared to field data. Field data used here have been measured at the southern Caspian Sea, Noshahr coasts, Iran. During the measurement period, two high-energy events with significant wave height of approximately 1.4 m have been measured. All simulations have been done based on a one dimensional crossshore transect. Wave transformation during propagation toward the coast has been modeled using the third generation model SWAN, and long-shore waveinduced current has been simulated by solving alongshore momentum equilibrium equation. To include the morphological change, the cross-shore sediment transport rate has been estimated using Bagnold [1966], Bowen [1980], and Bailard's [1981] (BBB) energetic sediment transport model, and results has been compared to the model developed by Plant et al. [2001], which itself is an energetic model based on Bagnold [1966]. Finally, bathymetric changes has been forecasted by solving cross-shore mass conservation equation which indicated slight outperform of BBB rather than Plant et al. model in this study area.

Continental Shelf Research, 2016

In this study, a series of field measurements were carried out to investigate triad interactions ... more In this study, a series of field measurements were carried out to investigate triad interactions of spectral peak in near shore. The water level fluctuations were recorded at 5 stations with depths varying from 0.8 to 5 meters along a shore-perpendicular transect at sandy coasts of Nowshahr, located in the southern Caspian Sea coast. Two storms with significant wave height of approximately 1.4 m were observed during the measurement period. Using bispectral analysis, a new quantitative index is proposed to investigate temporal and spatial intensity of nonlinear interaction between spectral peak and other harmonics. The proposed index was evaluated for time series of water level data and compared with the bicoherence value of self-spectral peak triad interaction (SSPT);) , (2 p p f f b. Comparing to SSPT, the proposed new index includes all positive and negative triad interactions with spectral peak. The relative depth, d k p , of non-breaking waves varied from 0.25 to 2.00 along the transect during the study period, where p k is the wave-number and d is the water depth. In general, SSPT increased by decreasing d k p ; however, the results showed that in two shallow stations the maximum SSPT did not correspond to the lowest values of d k p. A considerable time lag was observed between occurrence of the most intensive triad interactions and termination of wave breaking in post storm condition. Furthermore, the intensive triad interactions happened several hours after the largest Ursell numbers of non-breaking waves.

International Journal of coastal and offshore engineering, 2018

In this study, the evolution and dependency of infragravity waves (IGWs) on wind waves for breaki... more In this study, the evolution and dependency of infragravity waves (IGWs) on wind waves for breaking and nonbreaking conditions is separately investigated. The efficiency of two constant cutoff frequencies (0.125 and 0.14 Hz) is compared for wave data measured in the sandy beaches of Nowshahr at the Southern Caspian Sea. It is found that the frequency of 0.125 Hz results higher correlation coefficients between IGWs energy content and two wind wave groups. Two pair different correlation patterns between IGWs in one side and wind waves higher and lower than 0.125 Hz in another side were recognized for breaking and nonbreaking conditions. It can be concluded that the IGWs excitation is controlled by the frequency distribution of wind wave energy. According to 0.125 Hz as more successful option, the correlation of IGWs with swell waves is generally more significant than sea waves. In the nonbreaking wave condition, the IGWs are well correlated with sea waves, whereas no considerable correlation between IGWs and sea waves is found in the breaking condition. It is resulted that IGWs energy is approximately linearly proportional of both swell and sea waves in nonbreaking condition. In the high and moderate conditions of incident wave energy, the density of IGWs energy grows shoreward, while energy attenuation can be detected for IGWs in very low energy waves.

Science of The Total Environment

International Journal of coastal and offshore engineering

In this study, a simple and efficient approach based on nonlinear wave interaction fundamentals i... more In this study, a simple and efficient approach based on nonlinear wave interaction fundamentals is theoretically proposed to generate surface profile of the cnoidal waves. The approach includes Newton-Raphson algorithm to calculate the Ursell parameter and using a simple formulation to attain time series of cnoidal waves profile. The wave profile is determined as a superposition of limited number of cosine harmonics without encountering difficulties of using elliptic or hyperbolic functions, or any complex and complicated differential equations. It is demonstrated that a cnoidal wave profile is a result of high order self nonlinear interactions of primary frequency. Some definite energy is transmitted to higher harmonics due to nonlinear interactions. The amount of transmitted energy is controlled by Ursell parameter. The desirable accuracy determines the number of included harmonics in the proposed formulation and relative error of approach can be predicted based on Fourier and least square analysis techniques. The outputs of the proposed method are verified with cnoidal resulted from elliptic functions and the high efficiency of new approximation is revealed for engineering applications. The calculation of wave parameters such as energy flux, volume flux and radiation stress for cnoidal wave can be approximated using the proposed method. Using this approach, a physical interpretation of the Bm parameter (introduced in the first order of cnoidal wave theory) is presented. The calculation of several parameters such as velocity vectors and dynamic pressure of cnoidal waves is very simple by means of proposed approach.

Applied Ocean Research, 2021

Abstract The present study analyzes the field measurements of the reflective response of a permea... more Abstract The present study analyzes the field measurements of the reflective response of a permeable rubble mound breakwater encountered with a bimodal wave regime. The coexistence of sea and swell wind-driven waves during the measurement program provided directional spreading wave realizations for subsequent bulk and frequency-dependent wave reflection analysis. The directional wave data were acquired near the primary breakwater of Chabahar Port within 28 days, including 643 bursts using an AWAC wave recorder. The available formulae for wave reflection coefficient were evaluated against this data set. Results showed that the equations proposed by Postma (1989) and Zanuttigh and Van der Meer (2007) are in general agreement with the observations of the present study. However, the accuracy of reflection coefficient predictions was improved by developing two new alternative formulations. It was realized that the frequency reflective response differs between sea and swell prevailing conditions. The reflection coefficient decreases drastically within high sea wave predominant periods for the harmonics higher than peak frequency. However, reflection coefficients of high harmonics reduced slightly within swell domination periods. The frequency-dependent reflection coefficients can be even higher than unity due to energy transfer amongst other wave harmonics.

Journal of Oceanography, 2019

In this study, the compound and overtide constituents resulted from nonlinear triad interactions ... more In this study, the compound and overtide constituents resulted from nonlinear triad interactions were evaluated using Bispectral method at the eastern Iranian coasts of Makran. It was found that the most significant compound constituents at the studies area were KO2, KP2, MS4 and MN4. Also, the overtides of M4 and S4 were detectable by means of implemented method. The superiority of Bispectral method comparing with least square method (harmonic analysis) is in recognizing some of compound tides such as KO2, which is never identifiable using least square method. The corresponding Fourier harmonic frequencies to main tidal constituents were identified by comparing the results of the least square method and the Fourier analysis. Finally, the analysis was performed with d.o.f.s of 16, 32 and 64. The repeated significant bicoherence values in all three d.o.f.s and in the main tidal constituent frequencies range were regarded as the intensive and effective interactions.

Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هول... more Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هولا م ی نا هت د هبهب یداهیز بش رد ی ه زاهس ی رهب د همن به ام همد مها ک رد دا هما ا ی ا ااهجنا هی ن هسررب ی ، جا هما ی رد امز ی هاوهن رد و 3 ، همد 3 رپ ه ی د و 3 ل ت تاهفترا هی درگ ه ی بش اه ب و ی ه زاهس ی ن د هد ل هم رد اهه ی SWAN هه ب اقم ی هس ل ت د هم تادافترا هی امز رد ه هش ی هاوهن ارهب هش ههتتادرپ ل هم و ی ا ااهجنا هی ن اقم ی ههس ه ا رتماراهپ ود ی رد د هج م ی هولا تهسکش Thornton و Guza ه تخم ت اهم رد لاها ی هرب ره هها هش هداد ناهنن و ن هش هی ک زا ا ی ن م ههچ ت ام هی ناز بش رد ار د هبهب ی ه زاهس ی ل ت دا هما هی ی امز رد ی هاوهن د هد ل هم هس ت ی SWAN به ام یهم هنا اهن رد هی ت ارهب ی ا ه ا هی ن رتماراهپ ود ، ر و هطبا ی پ ی داهنهن درگ هی ن لاهمدا اهب هها د هد ل هم رد اهه ی

Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هول... more Thornton و Guza لاهس رد 1983 هسررب ی اره ه ا اه ب هها هش هداد ناهنن و ه هش ی ب رد د هج م نهیا هولا م ی نا هت د هبهب یداهیز بش رد ی ه زاهس ی رهب د همن به ام همد مها ک رد دا هما ا ی ا ااهجنا هی ن هسررب ی ، جا هما ی رد امز ی هاوهن رد و 3 ، همد 3 رپ ه ی د و 3 ل ت تاهفترا هی درگ ه ی بش اه ب و ی ه زاهس ی ن د هد ل هم رد اهه ی SWAN هه ب اقم ی هس ل ت د هم تادافترا هی امز رد ه هش ی هاوهن ارهب هش ههتتادرپ ل هم و ی ا ااهجنا هی ن اقم ی ههس ه ا رتماراهپ ود ی رد د هج م ی هولا تهسکش Thornton و Guza ه تخم ت اهم رد لاها ی هرب ره هها هش هداد ناهنن و ن هش هی ک زا ا ی ن م ههچ ت ام هی ناز بش رد ار د هبهب ی ه زاهس ی ل ت دا هما هی ی امز رد ی هاوهن د هد ل هم هس ت ی SWAN به ام یهم هنا اهن رد هی ت ارهب ی ا ه ا هی ن رتماراهپ ود ، ر و هطبا ی پ ی داهنهن درگ هی ن لاهمدا اهب هها د هد ل هم رد اهه ی

Oceanologia, 2021

Abstract This paper presents the results of a laboratory experiment on transmission, reflection, ... more Abstract This paper presents the results of a laboratory experiment on transmission, reflection, and dissipation of irregular waves over smooth impermeable submerged breakwaters. Experiments included 75 JONSWAP-based irregular waves with five different wave characteristics generated at three water depths in a 2D wave flume. The investigated breakwater sections were three rectangular breakwaters with different widths, a toothed rectangular breakwater, and a trapezoidal breakwater with a slope of 1:2. A new comprehensive dimensionless parameter (β) was proposed representing both wave hydrodynamic and breakwater geometry characteristics. This parameter could be employed as a suitable descriptive option to make an accurate estimate of the hydraulic performances of submerged breakwaters. The β parameter is composed of four conventional simple dimensionless variables. However, the results revealed that the relative submergence depth significantly affects the hydraulic responses of submerged breakwaters. The transmission, reflection and dissipation of waves show a logarithmic growth, a logarithmic reduction, and a quadratic decreasing trend against the increasing of β parameter, respectively. The verifications of results revealed the high efficiency of β parameter for data reported by Carevic et al. (2013) with R2 = 0.88 and high agreement with predictions made by Van der Meer et al. (2005) formulation with R2 = 0.93.

Ocean Engineering, 2021

Abstract This study experimentally investigates the development and decay of bound energy fractio... more Abstract This study experimentally investigates the development and decay of bound energy fractions due to positive and negative interactions (b2p and b2n, respectively) applying bispectral analysis. It was revealed that the Ursell number is the most successful parameter to estimate the variation patterns of b2p and b2n. The experimental waves included 27 waves with three offshore wave heights, three periods, and three offshore water depths propagating over a mild slope of 1:30. A wide variety of wave nonlinearity and bound coupling intensities were observed across the experimental dissipative surf zone. For a wave propagating toward the shore, the corresponding Ursell numbers for the relative maximum values of b2p and b2n are 0.27 and 0.22, respectively. The ratio of significant wave height to water depth corresponding to these extreme values for positive and negative triads are ~0.4 and ~0.32, respectively. The highest values of b2p and b2n for a progressive wave can be predicted as a function of the Ursell number using two new proposed experimental formulations. The sub-harmonics are more persistent during wave-breaking conditions than super-harmonics due to lower wave steepness. The biphase values of self-coupling of the spectral peak are attained negative for waves with Ursell numbers greater than 0.35.

Estuarine, Coastal and Shelf Science, 2021

Abstract This study analyzed the characteristics of infragravity waves (hereafter IGWs) based on ... more Abstract This study analyzed the characteristics of infragravity waves (hereafter IGWs) based on field observations collected near the plunging cliffs of Chabahar bay, Iran. Observations were made near Chabahar city during the summer monsoon season of 2018. The wave climate included two different durations of sea and swell predominance, with a maximum wave height reaching 2.5 m. Concurrent with the duration of the sea predominance, the ratio of IGW to swell wave height had an insensitive fluctuation against tidal variations, while this ratio had a strong negative correlation with tidal level during the high swell condition. The investigation of directional wave energy distribution revealed two correlated trends of shoreward and seaward IGWs with the wave regime. Larger values of the IGW reflection coefficients were observed during high sea wave conditions compared with high swell conditions. The IGW reflection coefficients decreased against swell energy growth with a logarithmic trend. The bound IGW energy fraction was studied using bispectral analysis. It is demonstrated that the maximum values of this parameter corresponded to high swell waves observed within low ebbs of the spring tide. The insignificant values of bound IGW energy fraction and the non-extended surf-zone revealed that most of the released IGWs originated from offshore and intermediate water depths. In addition, it was revealed that the inverse tidal trend of normalized IGW by swell height was due to bound IGW enhancement during ebb periods as a result of the nonlinear coupling of swell waves.

Applied Ocean Research, 2020

In this study, a linear formulation is found to estimate the wave reflection coefficient (K r) fr... more In this study, a linear formulation is found to estimate the wave reflection coefficient (K r) from plunging cliff coasts of Chabahar city according to field data measurements. The field measurement included directional wave data via three bursts for each hour and in total 1345 bursts during summer Southern-West monsoon using an ADCP gague. The significant wave heights reached 2.5 m and the corresponding peak periods were greater than 11 s. It was observed that the wave reflection coefficients are fully tidally modulated. The maximum values of K r reached 0.7 in a flood period of spring tide, while the minimum values were greater than 0.3 and corresponded to ebb periods in spring tide. The corresponding dimensionless parameters of wave height to depth, wave steepness and Ursell number to the highest values of K r were obtained as 0.17, 0.014, and 22, respectively. The variation ranges of reflection coefficient pertaining to the effect of four main tidal constituents as M2, S2, K1, and O1 were achieved as ∼ 9.6, 4.1, 7.1, and 3.6%, respectively. Finally, a linear formulation as a function of the tidal level was resulted to estimate the most accurate values of K r in the studied area. The averaged inaccuracy of resulted formulation was approximately 6.5%. The frequency reflection coefficients K r (f) was also investigated in this study. The results indicated the values close to 1 for long infragravity waves, because of occurrence of no significant dissipation. However, the similar values for short waves (fr > 0.25 Hz) were greater than 1 due to wind wave breaking as a result of the cliff toe collision. The temporal histogram of K r (f) revealed the tidally controlled variations of this parameter.

Applied Ocean Research, 2020

This paper presents the results of bound infragravity observation at the Nowshahr beach located i... more This paper presents the results of bound infragravity observation at the Nowshahr beach located in the southern part of the Caspian Sea. The water level data were measured at 6 stations along a transect perpendicular to the coastline. The bispectral method was utilized to show that the extreme values for the bound infragravity energy fraction (b ii) were occurring when dimensionless values of wave height to depth ratio, relative depth, and wave steepness were in the range of 0.18-0.22, 0.4-0.5 and 0.015-0.017, respectively. These detailed results could be equivalently summarized with the condition of having the Ursell number of peak waves within the range of 30-40. The corresponding short wave groupiness factor (G.F.) values for waves with high values of b ii were between 0.5 and 0.55. Also, it was revealed that the wave groupiness envelope had a positive correlation with infragravity wave energy level, but its correlation with the bound infragravity wave was negative when G.F. > 0.55. On the other hand, the low values of b ii against the spectrum peakedness parameter for breaking waves followed an exponential relationship. The correlation of bound and free infragravity waves with wind waves was also studied. For non-breaking condition, the correlations of bound infragravity waves with swell and sea waves were considerable. The correlation of free waves with swells was also significant. In contrast, for breaking waves, a negligible correlation was observed between bound infragravity waves and wind waves. o o 1/2 and H T o p 2

Journal of Marine Science and Application, 2018

This study evaluates the capability of the Simulating WAves Nearshore (SWAN) wave model (version ... more This study evaluates the capability of the Simulating WAves Nearshore (SWAN) wave model (version 41.01) in predicting significant wave height and spectral peak energy content for swell waves in very shallow water of surf zone during depth-induced wave breaking and dissipation. The model results were compared with field measurements at five nearshore stations. The results demonstrated that some breaker index formulations were successful for significant wave height prediction in surf zones. However, an incorrect shape of the energy spectrum and overestimated near spectral peak energy content at shallow water stations were obtained using all of the embedded depth-induced wave breaking formulations in SWAN. The dependent breaker index on relative depth (K p d) formulation, which was successful in predicting near spectral peak energy content, resulted in an average error of 30%. Finally, this formulation was modified to enhance the model performance in reproducing the spectral peak energy content.

Journal of Oceanography, 2018

In this study, the laboratory observations were accomplished for 36 random and irregular waves in... more In this study, the laboratory observations were accomplished for 36 random and irregular waves initiated according to the JONSWAP spectrum to study the impotance of energy transition to low and high frequency harmonics due to wave breaking in the outer surf-zone. The wave transformation was investigated using two trinary groups of pressure sensors at the beginning and end of ramp with the slope of 1:16. The maximum observed transferred energy due to wave breaking was about 22% of dissipated energy which was equal to 9% of total energy of the primary wave. In this manner, the prediced significant broken wave height was 8% underestimated using phased avraged wave models. The observations indicated the fraction of dissipated energy, which was transferred to low and high frequencies growth with increment of primary wave Ursell parameter at the initial depth.

International Journal of Maritime Technology, 2017

Cross-shore sediment transport is one of the effective factors in erosion and sedimentation, and ... more Cross-shore sediment transport is one of the effective factors in erosion and sedimentation, and affects dynamics of the beach profile in coastal areas. Furthermore, sandbar migration due to cross-shore sediment transport mostly effects beach nourishment, displacement of pollutions trapped in sediments, and organism and plants' lives. In this manuscript, sandbar migration due to cross-shore sediment transport is studied and results have been compared to field data. Field data used here have been measured at the southern Caspian Sea, Noshahr coasts, Iran. During the measurement period, two high-energy events with significant wave height of approximately 1.4 m have been measured. All simulations have been done based on a one dimensional crossshore transect. Wave transformation during propagation toward the coast has been modeled using the third generation model SWAN, and long-shore waveinduced current has been simulated by solving alongshore momentum equilibrium equation. To include the morphological change, the cross-shore sediment transport rate has been estimated using Bagnold [1966], Bowen [1980], and Bailard's [1981] (BBB) energetic sediment transport model, and results has been compared to the model developed by Plant et al. [2001], which itself is an energetic model based on Bagnold [1966]. Finally, bathymetric changes has been forecasted by solving cross-shore mass conservation equation which indicated slight outperform of BBB rather than Plant et al. model in this study area.

Continental Shelf Research, 2016

In this study, a series of field measurements were carried out to investigate triad interactions ... more In this study, a series of field measurements were carried out to investigate triad interactions of spectral peak in near shore. The water level fluctuations were recorded at 5 stations with depths varying from 0.8 to 5 meters along a shore-perpendicular transect at sandy coasts of Nowshahr, located in the southern Caspian Sea coast. Two storms with significant wave height of approximately 1.4 m were observed during the measurement period. Using bispectral analysis, a new quantitative index is proposed to investigate temporal and spatial intensity of nonlinear interaction between spectral peak and other harmonics. The proposed index was evaluated for time series of water level data and compared with the bicoherence value of self-spectral peak triad interaction (SSPT);) , (2 p p f f b. Comparing to SSPT, the proposed new index includes all positive and negative triad interactions with spectral peak. The relative depth, d k p , of non-breaking waves varied from 0.25 to 2.00 along the transect during the study period, where p k is the wave-number and d is the water depth. In general, SSPT increased by decreasing d k p ; however, the results showed that in two shallow stations the maximum SSPT did not correspond to the lowest values of d k p. A considerable time lag was observed between occurrence of the most intensive triad interactions and termination of wave breaking in post storm condition. Furthermore, the intensive triad interactions happened several hours after the largest Ursell numbers of non-breaking waves.

International Journal of coastal and offshore engineering, 2018

In this study, the evolution and dependency of infragravity waves (IGWs) on wind waves for breaki... more In this study, the evolution and dependency of infragravity waves (IGWs) on wind waves for breaking and nonbreaking conditions is separately investigated. The efficiency of two constant cutoff frequencies (0.125 and 0.14 Hz) is compared for wave data measured in the sandy beaches of Nowshahr at the Southern Caspian Sea. It is found that the frequency of 0.125 Hz results higher correlation coefficients between IGWs energy content and two wind wave groups. Two pair different correlation patterns between IGWs in one side and wind waves higher and lower than 0.125 Hz in another side were recognized for breaking and nonbreaking conditions. It can be concluded that the IGWs excitation is controlled by the frequency distribution of wind wave energy. According to 0.125 Hz as more successful option, the correlation of IGWs with swell waves is generally more significant than sea waves. In the nonbreaking wave condition, the IGWs are well correlated with sea waves, whereas no considerable correlation between IGWs and sea waves is found in the breaking condition. It is resulted that IGWs energy is approximately linearly proportional of both swell and sea waves in nonbreaking condition. In the high and moderate conditions of incident wave energy, the density of IGWs energy grows shoreward, while energy attenuation can be detected for IGWs in very low energy waves.