In this study the mass transport through free turbulent liquid surfaces, or gas/liquid interfaces, is considered. The main direction of mass transfer is perpendicular to the interface, so that a one-dimensional point of view is followed. The equations for the interfacial gas/liquid transport are presented using the RANDOM square WAVES method (RSW), a statistical tool that models the fluctuations of physical variables as ideal signals. The method defines three statistical functions (partition, reduction, and superposition), related to fluctuations of concentration and velocity, which were introduced into the mass advection-diffusion equation generating a set of differential equations adequate for boundary layer problems. Solution profiles of the partition and reduction functions, and of turbulent fluxes across the boundary layer were obtained for transient situations. The solutions use Taylor series centered at the immersed border of the concentration boundary layer. For practical applications, the series were truncated and the coefficients were calculated in order to satisfy adequate physical conditions. The proposed procedure substitutes coefficients of the higher order parcels of the truncated series, enabling them to satisfy boundary conditions in the two borders of the domain of interest, which is the region of variation of the mass concentration. The theoretical profiles for concentration and turbulent fluxes close to the interface agree with measurements and predictions found in the literature.

Understanding of wave hydrodynamics and its effects are important for engineers and scientists. Important insights may be gained from laboratory studies. Often the WAVES are simulated in laboratory flumes do not have the full characteristics of real sea WAVES. It is then necessary to present reliable methods of wave generation in wave flumes. In this paper, the results of numerically simulated water WAVES using different methods are presented. A model was developed to simulate water wave profile using DSA, NAS and WNDF methods. The results showed that although DSA method provides better agreement between output and target spectra, it is associated with non realistic simulation of sea WAVES. In the other hand WNDF method involves better stochastic wave characteristics if a qualitative white noise is used. It is also possible to put some controls on wave characteristics as input to WNDF model.

Seawalls are sheltering structures used for protecting the coastal regions against wave induced forces. Storm, movement of the ships, explosions caused by the attacks to the platforms and issues like these could result in the creation of RANDOM WAVES in significant areas of the port. Because of RANDOM nature of the wave behavior, the application of physical models for the study of wave-structure interaction can be quite efficient. In the present research, physical models of thin flexible walls were constructed and tested in a wave flume subject to generated RANDOM WAVES.The water surface variations and the strains at the base of the wall were recorded using sensors; and the relationship between the strain and the wave height was obtained using the zero up-crossing method. The results indicate that the strain-wave height relationship is linear. Since the behavior of the wall is within the elastic region, the relationship between the strain and the flexural moment at the base of the wall follows the Hook’s Law; and accordingly the relationship between the wave height and flexural moment at the base of the wall was obtained.

Wind WAVES, which are one of the most important phenomena in the marine environment, are generally progressive in nature and can move far distances out of their area of formation. Thus, an understanding of wave hydrodynamics and their effects is important for engineers in the design and construction of marine structures and coastal management. Significant insights may be gained from numerical and laboratory studies. Often the WAVES simulated in numerical and physical models do not have the full characteristics of real sea WAVES. It is then necessary to present a reliable method of wave simulation for numerical and laboratory wave flumes. In this paper, the results of numerically simulated water WAVES, using digital filters, are presented. A model has been developed to simulate a water wave profile from different target spectra using WNDF methods. The results showed that the WNDF method involves good stochastic wave characteristics if a suitable spectrum is used as target. The results have implications for the numerical or laboratory estimation of wave forces on model offshore or coastal structures.

Most Code such as API and BSI recommend Morison's equation to estimate hydrodynamic forces on offshore structures. Significant difference exists among these Codes due to using different methods of analysis and estimation of force coefficients. In this paper, data from full scale tests have been used to evaluate RANDOM WAVES and uniform current actions on the smooth piles.Four time and frequency domain analysis methods were used to estimate Cd & Cm, Force Time Series Fitting Method (LS-TS) has given better results than the others. Furthermore, the errors from estimating hydrodynamic forces on smooth piles are more than those on rough piles.

Similar to RANDOM sea WAVES, forces on the offshore structures due to WAVES are RANDOM. These forces can be mainly divided into two componen.ts, namely, inline forces and transverse or lift forces. The RANDOM nature of lift forces is more complicated than that of inline forces and both should be combined for design purposes. In the present paper, two different approaches have been used to determine time series of lift forces. Along these lines, the determination of lift coefficients is discussed which have then been used to obtain transverse forces and compared with experimental data. The experimental data used in this study were coliected at Delft Hydraulics Laboratory on a full-scale rough vertical cylinder.

Most of the Codes of Practice (API, BSI, DnV, NPD) uses Morison’s equation to estimate hydrodynamic loads on fixed and moving offshore structures. The significant difference in the prediction of the loads mainly arises from the assumption of the values of hydrodynamic coefficients. In this paper by analyzing a full scale set of data in large KC’s numbers collected from Delta Wave Flume in the Netherlands the effects of RANDOM WAVES (JONSWAP spectrum) and uniform current over the artificially rough cylinder have been investigated. The prediction of water particle kinematics has been made from the surface elevation measurements using Stokes fifth order wave theory. By using the Weighted Least Squares technique the hydrodynamic coefficients have been estimated. A comparison between measured force and predicted force shows that although the accuracy of prediction over the whole data is about 90%, the errors on the local peaks are significant (24%) the case which is of interest in the ultimate limit state involving a single extreme wave.

Quay walls are sheltering structures used for protecting coastal regions against wave-induced forces. Because of the RANDOM nature of the wave behavior, the application of physical models for the study of wave-structure interaction can be quite efficient. The aim of this study was to investigate the behavior of quay walls under RANDOM WAVES through experimental methods. The study used walls with vertical geometrical form, which were exposed to sea RANDOM WAVES under the JONSWAP spectrum. Surface level and wall strain values were measured using built-in sensors. A neural network model was developed using the feed-forward method with the backpropagation algorithm to analyze the time series of water surface level and strain. High coefficients of determination during the training and verification phases were observed, indicating good network performance. Self-correlation analysis of the time series showed that the data exhibited first-degree Markov characteristics. This finding was taken into consideration and increased the coefficients of determination in the neural network model.

The stability of the roll motion of crafts is of great importance because of its significant impact on safety, ease of travel, overall performance and potential capsizing of the system. It is important to study this motion and to investigate its dynamic stability, which is completely nonlinear and highly sensitive to atmospheric conditions, asymmetric loads and the presence of water on the deck. In this research, it was tried to study the stability of the roll motion under the pointed conditions and RANDOM white-noise WAVES analytically. To do this, the probability density function of response was obtained using the Fokker Planck Kolmogorov (FPK) method and the stationary solution of the corresponding partial differential equation. Then, the effect of water on the deck, deviation moment due to the asymmetric load or crossing winds, the damping coefficient and the intensity of the RANDOM wave was investigated. Introducing non-dimensional parameters, the equation of roll motion was derived so that it could be applied to a wide range types of crafts. The results, as expected, indicate a significant qualitative change i. e. a bifurcation in the behavior when we have water on the deck. The stability of three types of the crafts is also studied and it is shown that in the presence of water on the deck, the type of craft can completely effect on instability phenomenon.

Using the statistical characteristics is one of the methods to justify the RANDOM nature of the ocean WAVES. Probability function is used to facilitate the studies of the RANDOM wave’s parameters, such as the surface and height and period of the WAVES. Since, the force of the ocean WAVES are the prevalent principal forces on the offshore structures, the assignment of the significant structural responses such as applied inline and transverse forces and also total moment on the piles is the main step for design and construction of the structures. In this paper, the RANDOM WAVES and their effects on the cylindrical pile will be investigated. These WAVES have been recorded during some tests which will be illustrated separately. The oscillation of some linear or nonlinear responses of the pile has been discussed statistically and then spectral analysis performed and their extremity amplitude statistical analysis interpreted and prevalent probability functions determined.