The main purpose of this paper is to investigate the stochastic roll motion of a ship in IRREGULAR WAVES. To achieve this goal, the differential equation of ship roll motion roll in longitudinal WAVES with respect to nonlinear damping and restoring arm has been created. Due to the stochastic nature of sea WAVES, the wave excitation force is generated through stochastic excitation using effective wave theory. To achieve the ship roll motion response, the stochastic differential equation of the roll is converted to the Ito’s stochastic differential equation form. The generated equation is solved several times using the Monte Carlo process to statistically evaluate the roll motion response. Finally, the probability distribution function of the ship's roll motion at IRREGULAR WAVES is calculated for the C11 container ship as a sample ship. Using these results, a better approximation of the maximum angle of roll motion of a ship in IRREGULAR WAVES can be obtained.

Guyed tower is a compliant offshore platform used for drilling and extraction of oil in deep water. This platform has a flexible body and needs proper mooring system to control the deck movements. In present study this platform is analyzed in frequency domain due to IRREGULAR WAVES. The exiting force extracted from Pierson Moskovits spectrum using Morrison Equation. Modeling of moorings is difficult due to their variable stiffness and non linear interaction with main structure. Therefore first using static analysis data the diagram for mooring force excursion was obtained and fitted to a polynomial of order 5. Then using this equation the spring force of moorings was linearized. Furthermore the drag term was linearized and both of these two linearized terms used in dynamic equation of motion. The results of analysis showed that errors due to this linearization on final results are negligible. Results of this research can be used for optimum design of guyed towers in deep water and its special application in Caspian Sea can be considered.

Ship harmonic motion is an important and practical characteristic in ship design and performance evaluation. The development and optimization of hull-form, ship’ s dynamic effects, seakeeping performance, and motion control, all require the motion data that includes wave exciting forces as well as dynamic response of the ship. This paper presents a new approach for time-domain simulation of full-scale ship model with four degrees of freedom based on computational fluid dynamics using unsteady RANS method. The key objective of this paper was the full-scale simulation of ship motion in oblique WAVES and assessment of time domain forces, moments, and other motion parameters. The David Taylor Model Basin (DTMB) 5415 full-scale model has been used for the numerical studies in this paper. The obtained computational results showed good conformation to the results obtained using the strip theory. It is intended to extend this research to subscale test experiments for more definite validation of the results.

The sea wave causes excess resistance which is out of scope of calm water resistance. The total wave force in horizontal plane is divided into "Added Resistance" and "Drift Force". In this study, based on Gerritsma and Beuckelman [3] hypothesis a computer program has been developed for calculation of added resistance and drift force at various ship speeds and various heading angles in oblique seas. This program calculates wave force both in regular and IRREGULAR WAVES. After validation of the program, effects of different parameters on wave force imposed on vessel have been studied.      

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.

A mathematical model is presented to investigate the effects of sandiness, IRREGULAR boundary interfaces, heterogeneity and viscoelasticity on the phase velocity of Love WAVES. Geometry of the problem is consisting of an initially stressed viscoelastic layer with corrugated IRREGULAR boundaries, which is sandwiched between heterogeneous orthotropic semi-infinite half-space with initial stress and pre-stressed dry sandy half-space. Heterogeneity arises in the upper half-space is due to trigonometric variation in elastic parameters of the orthotropic medium. Inclusion of the concept of corrugated IRREGULAR viscoelastic layer clamped between two dissimilar half-spaces under different physical circumstances such as initial stress and heterogeneity brings a novelty to the existing literature related to the study of Love wave. Dispersion equation for Love wave is obtained in closed form. The obtained dispersion relation is found to be in well agreement with classical Love wave equation. Numerical example and graphical illustrations are made to demonstrate notable effect of initial stress, internal friction, wave number and amplitude of corrugations on the phase velocity of Love WAVES.

In this study, the performance of a cylinder absorbing wave energy from IRREGULAR incident WAVES, as one of the renewable energy systems, is investigated numerically using complete solution of the Navier-Stokes equations. For this purpose, the control volume approach in conjunction with the fictitious domain method, for modeling the solid object motions inside fluid, are used where a two-step projection method is used to solve the governing equations. The results show that despite the cylinder absorbs energy in two main directions, its energy absorption efficiency in IRREGULAR WAVES is about 8%. Due to the employed spring and damper in these devices, the system has only one natural frequency which is the reason for its low efficiency at IRREGULAR WAVES. Results also show that for steep WAVES at deep waters, the maximum efficiency occurs at larger spring coefficient and smaller damping coefficients, while at moderate water depths and wave steepness, the maximum efficiency occurs at smaller spring coefficients and larger damping coefficients. Therefore, to reach maximum energy absorption efficiency at IRREGULAR WAVES, not only these coefficient has to be adjusted carefully, but also it is recommended to use multi-resonance systems or several cylinders with different natural frequencies.