Water waves excited by near-impulsive wind forcing

2017 ◽  
Vol 828 ◽  
pp. 459-495 ◽  
Author(s):  
Andrey Zavadsky ◽  
Lev Shemer
Keyword(s):  
Wave Field ◽  
Water Waves ◽  
Wind Wave ◽  
Wind Forcing ◽  
Wave Parameter ◽  
Small Scale ◽  
Detailed Knowledge ◽  
Limited Information ◽  
Statistical Parameters ◽  
Resonance Model

Only limited information is currently available on the evolution of waves generated by wind that varies in time, and in particular on the initial stages of wind–wave growth from rest under a suddenly applied wind forcing. The emerging wind–wave field varies in time as well as in space. Detailed knowledge of wave parameter distributions under those conditions contributes to a better understanding of the mechanisms of wind wave generation. In the present study, the instantaneous surface elevation and two components of the instantaneous surface slope were recorded at various fetches in a small-scale experimental facility under nearly impulsive wind forcing. Numerous independent realizations have been recorded for each selection of operational conditions. Sufficient data at a number of fetches were accumulated to calculate reliable ensemble-averaged statistical parameters of the evolving random wind–wave field as a function of the time elapsed from activation of wind forcing. Distinct stages in the wave evolution process from appearance of initial ripples to emergence of a quasi-steady wind–wave field were identified. The experimental results during each stage of evolution were analysed in view of the viscous instability theory by Kawai (J. Fluid Mech., vol. 93, 1979, pp. 661–703) and the resonance model by Phillips (J. Fluid Mech., vol. 2, 1957, pp. 417–445).

scholarly journals On Evolution of Young Wind Waves in Time and Space

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 562 ◽  
Author(s):  
Shemer
Keyword(s):  
Wave Field ◽  
Field Experiments ◽  
Wind Wave ◽  
Wind Waves ◽  
Wave Generation ◽  
Wind Forcing ◽  
Spatial And Temporal Variation ◽  
Extensive Discussion ◽  
Deterministic Theory ◽  
Theoretical Approaches

The mechanisms governing the evolution of the wind-wave field in time and in space are not yet fully understood. Various theoretical approaches have been offered to model wind-wave generation. To examine their validity, detailed and accurate experiments under controlled conditions have to be carried out. Since it is next to impossible to get the required control of the governing parameters and to accumulate detailed data in field experiments, laboratory studies are needed. Extensive previously unavailable results on the spatial and temporal variation of wind waves accumulated in our laboratory under a variety of wind-forcing conditions and using diverse measuring techniques are reviewed. The spatial characteristics of the wind-wave field were determined using stereo video imaging. The turbulent airflow above wind waves was investigated using an X-hot film. The wave field under steady wind forcing as well as evolving from rest under impulsive loading was studied. An extensive discussion of the various aspects of wind waves is presented from a single consistent viewpoint. The advantages of the stochastic approach suggested by Phillips over the deterministic theory of wind-wave generation introduced by Miles are demonstrated. Essential differences between the spatial and the temporal analyses of wind waves’ evolution are discussed, leading to examination of the applicability of possible approaches to wind-wave modeling.

scholarly journals Statistical Parameters of the Air Turbulent Boundary Layer over Steep Water Waves Measured by the PIV Technique

2011 ◽  
Vol 41 (8) ◽  
pp. 1421-1454 ◽  
Author(s):  
Yu. Troitskaya ◽  
D. Sergeev ◽  
O. Ermakova ◽  
G. Balandina
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Interaction Parameter ◽  
Water Waves ◽  
Water Surface ◽  
Wind Wave ◽  
Wave Interaction ◽  
Statistical Parameters ◽  
Piv Technique ◽  
Wave Induced

Abstract A turbulent airflow with a centerline velocity of 4 m s−1 above 2.5-Hz mechanically generated gravity waves of different amplitudes has been studied in experiments using the particle image velocimetry (PIV) technique. Direct measurements of the instantaneous flow velocity fields above a curvilinear interface demonstrating flow separation are presented. Because the airflow above the wavy water surface is turbulent and nonstationary, the individual vector fields are conditionally averaged sampled on the phase of the water elevation. The flow patterns of the phase-averaged fields are relatively smooth. Because the averaged flow does not show any strongly nonlinear effects, the quasi-linear approximation can be used. The parameters obtained by the flow averaging are compared with the theoretical results obtained within the theoretical quasi-linear model of a turbulent boundary layer above the wavy water surface. The wave-induced pressure disturbances in the airflow are calculated using the retrieved statistical ensemble of wind flow velocities. The energy flux from the wind to waves and the wind–wave interaction parameter are estimated using the obtained wave-induced pressure disturbances. The estimated values of the wind–wave interaction parameter are in a good agreement with the theory.

Statistical Analysis of the Spatial Evolution of the Stationary Wind Wave Field

2013 ◽  
Vol 43 (1) ◽  
pp. 65-79 ◽  
Author(s):  
A. Zavadsky ◽  
D. Liberzon ◽  
L. Shemer
Keyword(s):  
Wave Field ◽  
High Frequency ◽  
Water Waves ◽  
Wind Wave ◽  
Field Measurements ◽  
Quantitative Comparison ◽  
Spatial Evolution ◽  
Frequency Spectra ◽  
Wave Flume ◽  
Laboratory Facilities

Abstract Detailed investigation of wind-generated water waves in a 5-m-long wind wave flume facility is reported. Careful measurements were carried out at a large number of locations along the test section and at numerous airflow rates. The evolution of the wind wave field was investigated using appropriate dimensionless parameters. When possible, quantitative comparison with the results accumulated in field measurements and in larger laboratory facilities was performed. Particular attention was given to the evolution of wave frequency spectra along the tank, distinguishing between the frequency domain around the spectral peak and the high-frequency tail of the spectrum. Notable similarity between the parameters of the evolving wind wave field in the present facility and in field measurements was observed.

Wind–wave coupling study using LES of wind and phase-resolved simulation of nonlinear waves

2019 ◽  
Vol 874 ◽  
pp. 391-425 ◽  
Author(s):  
Xuanting Hao ◽  
Lian Shen
Keyword(s):  
Wave Field ◽  
Water Waves ◽  
Wind Wave ◽  
Wave Spectrum ◽  
High Order ◽  
Band Spectrum ◽  
Wave Growth ◽  
Turbulent Wind ◽  
Wind Turbulence ◽  
The Waves

We present a study on the interaction between wind and water waves with a broad-band spectrum using wave-phase-resolved simulation with long-term wave field evolution. The wind turbulence is computed using large-eddy simulation and the wave field is simulated using a high-order spectral method. Numerical experiments are carried out for turbulent wind blowing over a wave field initialised using the Joint North Sea Wave Project spectrum, with various wind speeds considered. The results show that the waves, together with the mean wind flow and large turbulent eddies, have a significant impact on the wavenumber–frequency spectrum of the wind turbulence. It is found that the shear stress contributed by sweep events in turbulent wind is greatly enhanced as a result of the waves. The dependence of the wave growth rate on the wave age is consistent with the results in the literature. The probability density function and high-order statistics of the wave surface elevation deviate from the Gaussian distribution, manifesting the nonlinearity of the wave field. The shape of the change in the spectrum of wind-waves resembles that of the nonlinear wave–wave interactions, indicating the dominant role played by the nonlinear interactions in the evolution of the wave spectrum. The frequency downshift phenomenon is captured in our simulations wherein the wind-forced wave field evolves for $O(3000)$ peak wave periods. Using the numerical result, we compute the universal constant in a wave-growth law proposed in the literature, and substantiate the scaling of wind–wave growth based on intrinsic wave properties.

Energy Content Characterization of Water Waves Using Linear and Nonlinear Spectral Analysis

2021 ◽  
pp. 1-30
Author(s):  
Ali Mohtat ◽  
Solomon Yim ◽  
Alfred R. Osborne
Keyword(s):  
Wave Field ◽  
Nonlinear Wave ◽  
Water Waves ◽  
Ad Hoc ◽  
Energy Content ◽  
Energy Calculation ◽  
Linear And Nonlinear ◽  
Definition Of ◽  
Exact Energy ◽  
Wave Modes

Abstract The survivability, safe operation, and design of marine vehicles and wave energy converters are highly dependent on accurate characterization and estimation of the energy content of the ocean wave field. In this study, analytical solutions of the nonlinear Schrödinger equation (NLS) using periodic inverse scattering transformation (IST) and its associated Riemann spectrum are employed to obtain the nonlinear wave modes (eigen functions of the nonlinear equation consisting of multiple phase-locked harmonic components). These nonlinear wave modes are used in two approaches to develop a more accurate definition of the energy content. First, in an ad hoc approach, the amplitudes of the nonlinear wave modes are used with a linear energy calculation resulting in a semi-linear energy estimate. Next, a novel, mathematically exact definition of the energy content taking into account the nonlinear effects up to fifth order is introduced in combination with the nonlinear wave modes, the exact energy content of the wave field is computed. Experimental results and numerical simulations were used to compute and analyze the linear, ad hoc, and exact energy contents of the wave field, using both linear and nonlinear spectra. The ratio of the ad hoc and exact energy estimates to the linear energy content were computed to examine the effect of nonlinearity on the energy content. In general, an increasing energy ratio was observed for increasing nonlinearity of the wave field, with larger contributions from higher-order harmonic terms. It was confirmed that the significant increase in nonlinear energy content with respect to its linear counterpart is due to the increase in the number of nonlinear phase-locked (bound wave) modes.

Pre-Test and Analysis of a Reinforced Concrete Slab Subjected to Blast From a Non-Confined Explosive

2018 ◽  
pp. 272-287
Author(s):  
Fausto B. Mendonça ◽  
Girum S. Urgessa
Keyword(s):  
Dynamic Analysis ◽  
Large Scale ◽  
Concrete Slab ◽  
Wave Parameter ◽  
Experimental Program ◽  
Small Scale ◽  
Maximum Displacement ◽  
Reinforced Concrete Slab ◽  
Test Experiment ◽  
Rc Slabs

A large scale experimental program consisting of testing 10 RC slabs with different variations of concrete compressive strength, reinforcement ratio and retrofit was conducted in Brazil. As part of that test program, a small-scale blast pre-test setup and associated dynamic analysis were conducted in order to confirm the proper functioning of the blast test sensors (pressure gages, displacement meter and accelerometers). The results of the pre-test were compared with theoretical blast wave parameter predictions using established equations and maximum displacement predictions using simplified dynamic analysis. The pre-test experiment provided useful insights and was shown to be critical for the success of the subsequent large scale blast tests.

An Integrated Approach for History Matching of Multiscale-Fracture Reservoirs

SPE Journal ◽  
2019 ◽  
Vol 24 (04) ◽  
pp. 1508-1525
Author(s):  
Mengbi Yao ◽  
Haibin Chang ◽  
Xiang Li ◽  
Dongxiao Zhang
Keyword(s):  
History Matching ◽  
Large Scale ◽  
Fractured Reservoirs ◽  
Integrated Approach ◽  
Small Scale ◽  
Gaussian Field ◽  
Limited Information ◽  
Fractured Reservoir ◽  
Discrete Fracture Model ◽  
Single Scale

Summary Naturally or hydraulically fractured reservoirs usually contain fractures at various scales. Among these fractures, large-scale fractures might strongly affect fluid flow, making them essential for production behavior. Areas with densely populated small-scale fractures might also affect the flow capacity of the region and contribute to production. However, because of limited information, locating each small-scale fracture individually is impossible. The coexistence of different fracture scales also constitutes a great challenge for history matching. In this work, an integrated approach is proposed to inverse model multiscale fractures hierarchically using dynamic production data. In the proposed method, a hybrid of an embedded discrete fracture model (EDFM) and a dual-porosity/dual-permeability (DPDP) model is devised to parameterize multiscale fractures. The large-scale fractures are explicitly modeled by EDFM with Hough-transform-based parameterization to maintain their geometrical details. For the area with densely populated small-scale fractures, a truncated Gaussian field is applied to capture its spatial distribution, and then the DPDP model is used to model this fracture area. After the parameterization, an iterative history-matching method is used to inversely model the flow in a fractured reservoir. Several synthetic cases, including one case with single-scale fractures and three cases with multiscale fractures, are designed to test the performance of the proposed approach.

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