An experimental study of the surface elevation probability distribution and statistics of wind-generated waves

1980 ◽  
Vol 101 (1) ◽  
pp. 179-200 ◽  
Author(s):  
Norden E. Huang ◽  
Steven R. Long
Keyword(s):  
Experimental Study ◽  
Probability Density Function ◽  
Probability Distribution ◽  
Wave Field ◽  
Field Data ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Surface Elevation ◽  
Strong Wind ◽  
Non Gaussian

Laboratory experiments were conducted to measure the surface elevation probability density function and associated statistical properties for a wind-generated wave field. The laboratory data together with some limited field data were compared. It is found that the skewness of the surface elevation distribution is proportional to the significant slope of the wave field, §, and all the laboratory and field data are best fitted by \[ K_3 = 8\pi\S, \] with § defined as ($(\overline{\zeta^2})^{\frac{1}{2}}/\lambda_0 $, where ζ is the surface elevation, and λ0 is the wavelength of the energy-containing waves. The value of K3 under strong wind could reach unity. Even under these highly non-Gaussian conditions, the distribution can be approximated by a four-term Gram-Charlier expansion. The approximation does not converge uniformly, however. More terms will make the approximation worse.

Effect of Spatial Variation of a Wave Field on the Resulting Ripple Characteristics and Comparison to Present Ripple Predictors

2009 ◽  
Author(s):  
Blake J. Landry ◽  
Yovanni A. Catan˜o-Lopera ◽  
Matthew J. Hancock ◽  
Chiang C. Mei ◽  
Marcelo H. Garci´a
Keyword(s):  
Spatial Variation ◽  
Wave Field ◽  
Test Section ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Standing Waves ◽  
Sand Ripple ◽  
Wave Measurements ◽  
Progressive Waves ◽  
Sediment Test

Laboratory experiments analyzed herein focus on the validity of ripple predictors under spatially variable wave envelopes. Present-day ripple predictors commonly derived from laboratory data (for smaller wave periods of about 1 to 4 s) within which only small regions of the facilities were used to observe and measure the sand ripple geometric characteristics of the nearly progressive waves measured overhead. When extended to large sediment test sections, our results show that the predictors are still valid along the tank under wave conditions which have significant wave envelope spatial variation (e.g., standing waves), provided that ripple predictors use the wave measurements directly above the respective locations within the computations. Results indicate that even under the case of mild reflection, noticeable variation in ripple characteristics can be seen along the sediment test section; thus, compels the necessity of measuring the wave field along the entire sediment section to achieve accurate results.

Estimating Wave Induced Kinematics Underneath Measured Time Histories of Surface Elevation

2020 ◽  
Author(s):  
Thomas B. Johannessen
Keyword(s):  
Boundary Condition ◽  
Wave Field ◽  
Nonlinear Wave ◽  
Velocity Potential ◽  
Laboratory Data ◽  
Surface Elevation ◽  
Surface Boundary ◽  
Wave Impact ◽  
Measured Time ◽  
Time Histories

Abstract The present paper is concerned with the accurate prediction of nonlinear wave kinematics underneath measured time histories of surface elevation. It is desired to develop a method which is useful in analysis of offshore measurements close to wind turbine foundations. The method should therefore be robust in relatively shallow water and should be able to account for the presence of the foundation and the shortcrestedness of offshore seastates. The present method employs measurements of surface elevation time histories at one or a small number of locations and solves the associated velocity potential by minimizing the error in the free surface boundary conditions. The velocity potential satisfies exactly Laplace’s equation, the bed boundary condition and (optionally) the boundary condition on the wall of a uniform surface piercing column. This is achieved by associating one wavenumber with every wave frequency thereby sacrificing the possibility of following the nonlinear wave evolution but ensuring a good description of the wave properties locally. For shortcrested waves, the direction of wave component propagation is drawn from a known or assumed directional spectrum. No attempt is made to calculate the directional distribution of the wave field from the surface elevation measurements since this is usually not realistically possible with the available data. The method is set up for analysis with or without a uniform current, for shortcrested or longcrested waves and with or without a surface piercing column in the wave field. It has been compared with laboratory data for steep longcrested and shortcrested waves. The method is shown to be in good agreement with measurements. Since the method is based on a Fourier series of surface elevation, however, it cannot model overtopping breaking waves and associated wave impact loading. For problems where wave breaking is important, the method may serve as a screening analysis used to select wave events for detailed analysis using Computational Fluid Dynamics (CFD).

Statistical properties of the kinematics and dynamics of a random gravity-wave field

1975 ◽  
Vol 70 (2) ◽  
pp. 251-255 ◽  
Author(s):  
C. C. Tung
Keyword(s):  
Probability Density Function ◽  
Wave Field ◽  
Gravity Wave ◽  
Vertical Velocity ◽  
Dynamic Pressure ◽  
Kinematics And Dynamics ◽  
Vertical Acceleration ◽  
Vertical Velocity Component ◽  
Wave Solutions ◽  
Non Gaussian

The probability density function and the first three statistical moments of the velocity, acceleration and dynamic pressure are obtained for a Gaussian, stationary, homogeneous, random gravity-wave field in deep water, using infinitesimal wave solutions. It is shown that the velocity, acceleration and pressure are non-Gaussian. While the horizontal accelerations and vertical velocity component are of zero mean and unskewed, the dynamic pressure, vertical acceleration and horizontal velocity components are skewed and have non-zero mean.

scholarly journals Rogue waves in opposing currents: an experimental study on deterministic and stochastic wave trains

2015 ◽  
Vol 769 ◽  
pp. 277-297 ◽  
Author(s):  
A. Toffoli ◽  
T. Waseda ◽  
H. Houtani ◽  
L. Cavaleri ◽  
D. Greaves ◽  
...  
Keyword(s):  
Experimental Study ◽  
Nonlinear Wave ◽  
Large Amplitude ◽  
Laboratory Experiments ◽  
Rogue Waves ◽  
Rapid Transition ◽  
Wave Trains ◽  
Non Gaussian ◽  
Directional Sea States

Interaction with an opposing current amplifies wave modulation and accelerates nonlinear wave focusing in regular wavepackets. This results in large-amplitude waves, usually known as rogue waves, even if the wave conditions are less prone to extremes. Laboratory experiments in three independent facilities are presented here to assess the role of opposing currents in changing the statistical properties of unidirectional and directional mechanically generated random wavefields. The results demonstrate in a consistent and robust manner that opposing currents induce a sharp and rapid transition from weakly to strongly non-Gaussian properties. This is associated with a substantial increase in the probability of occurrence of rogue waves for unidirectional and directional sea states, for which the occurrence of extreme and rogue waves is normally the least expected.

scholarly journals The Effect of Candidate Quality on Electoral Equilibrium: An Experimental Study

2004 ◽  
Vol 98 (1) ◽  
pp. 77-90 ◽  
Author(s):  
ENRIQUETA ARAGONES ◽  
THOMAS R. PALFREY
Keyword(s):  
Experimental Study ◽  
Probability Distribution ◽  
Laboratory Experiments ◽  
Median Voter ◽  
Strong Support ◽  
Quantal Response ◽  
Policy Space ◽  
One Dimensional ◽  
Electoral Equilibrium ◽  
Main Effects

When two candidates of different quality compete in a one-dimensional policy space, the equilibrium outcomes are asymmetric and do not correspond to the median. There are three main effects. First, the better candidate adopts more centrist policies than the worse candidate. Second, the equilibrium is statistical, in the sense that it predicts a probability distribution of outcomes rather than a single degenerate outcome. Third, the equilibrium varies systematically with the level of uncertainty about the location of the median voter. We test these three predictions using laboratory experiments and find strong support for all three. We also observe some biases and show that they can be explained by quantal response equilibrium.

Experimental study on okra planter for sowing of soaked seed

2020 ◽  
Vol 44 (04) ◽  
pp. 22-29
Author(s):  
Badgujar C M ◽  
H S Dhingra ◽  
A Gautam ◽  
R Khurana ◽  
G S Mannes
Keyword(s):  
Experimental Study ◽  
Laboratory Experiments ◽  
Evaluation Studies ◽  
Laboratory Data ◽  
Field Capacity ◽  
Field Evaluation ◽  
Field Conditions ◽  
Plant Spacing ◽  
Performance Indices ◽  
Plant Plant

India is one of the leading Okra-producing countries producing 66.3% of the World’s okra. However, the traditional manual sowing methods result in low yield, poor quality, and high cost of cultivation. Therefore, an experimental study was designed to evaluate a tractor-operated Okra planter in the laboratory and field conditions for a locally available seed variety (Pusa A4). Laboratory experiments consisted of three independent variables; inclined plates (3 levels), inclination angles (3 levels), and speed of operations (4 levels). Dependent variables were seed spacing, a number of seeds/meter row length, and performance indices (multiple index, miss index, and quality of feed index). A 3×3×4 factorial design was applied to laboratory data analysis. The planter’s best parameter combination (plate, Inclination angle, and speed) was evaluated on actual field conditions at two different locations (X and Y). The field evaluation includes; plant-plant spacing, performance indices, planter field capacity, and fuel consumption. The planter was operated at 2.17, 2.25 km/h and plant-plant spacing was observed 15.98 cm, 17.11 cm, respectively, for locations X and Y. The observed plant spacing was close to desired spacing (15 cm). The field evaluation studies validated the results of laboratory experiments and desirable plant population were observed at both locations.

Deposition Prediction of Debris Flow Alluvial Fan Based on Experimental Study

2012 ◽  
Vol 518-523 ◽  
pp. 4819-4822
Author(s):  
Jin Feng Liu ◽  
Shun Yang ◽  
Guo Qiang Ou
Keyword(s):  
Experimental Study ◽  
Debris Flow ◽  
Statistical Method ◽  
Laboratory Experiments ◽  
Empirical Models ◽  
Alluvial Fan ◽  
Disaster Prevention ◽  
Average Accuracy ◽  
Hazardous Area ◽  
Debris Flow Disaster

The deposition prediction of debris flow hazardous area is very important for organizing and implementing debris flow disaster prevention and reduction. This paper selected the data base from laboratory experiments and applied the multiple regression statistical method to establish a series of empirical calculation models for delimiting the debris flow hazardous areas on the alluvial fan. The empirical models for predicting the maximum deposition length (Lc), the maximum deposition width (Bmax) and the maximum deposition thichness (Z0) under the condition of different debris flow volumes (V), densities (rm) and slopes of accumulation area (θd) were establised. And the verification results indicated that the established models can predict the debris flow hazards area with the average accuracy of 86%.

Nutritional ecology of the invasive freshwater mysid Limnomysis benedeni: field data and laboratory experiments on food choice and juvenile growth

Hydrobiologia ◽  
2012 ◽  
Vol 705 (1) ◽  
pp. 75-86 ◽  
Author(s):  
Almut J. Hanselmann ◽  
Bettina Hodapp ◽  
Karl-Otto Rothhaupt
Keyword(s):  
Food Choice ◽  
Field Data ◽  
Laboratory Experiments ◽  
Nutritional Ecology ◽  
Juvenile Growth ◽  
Limnomysis Benedeni
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