Sharif Digital Repository

In this paper a 3D numerical model was developed to study the complicated interaction between waves and a set of tandem fixed cylinders. The fluid was considered to be inviscid and irrotational. Therefore, the Helmholtz equation was used as a governing equation. The boundary element method (BEM) was adopted to discretize the relevant equations. Open boundaries were used in far fields of the study domain. Linear waves were generated and propagated towards tandem fixed cylinders to estimate the forces applied on them. Special attention was paid to consideration of the effect on varying non-dimensional cylinder radius and distance between cylinders, ka and kd on forces and trapped modes. The... 

This paper addresses numerically-derived tsunami wave loads on bridge superstructures using smoothed particle hydrodynamics (SPH), which is a type of mesh-free methods. Although there exist some relationships for the case of impinged loads on bridges exerted by regular (sinusoidal) waves, for the case of solitary waves such as tsunamis, no relation has yet been proposed in the literature. This shortcoming is partly due to the lack of understanding the mechanism of wave action on the bridge superstructures. In this study, three water depths, three wave amplitudes and four submergence depths of the deck are considered for the process of numerical investigation of tsunami-induced loads on... 

Rubble-mound breakwaters are common marine structures that provide a safe area for human coastal activities. The stability of these structures against sea-waves requires their seaward slope to be protected by an armor layer consisting of natural rock or concrete units. To provide a safe breakwater, it is reasonable to establish a relation between the exerted wave loads and the stability of the armor units. However, up to now, the empirical design equations, derived from model tests, relate wave parameters to armor weight, and keeps the effect of wave loads in a black box. In this paper, a new approach, based on numerically-derived wave loads on the armor, is presented to evaluate the... 

This paper presents a detailed frequency-domain system identification method applied to identify steering dynamics of a coastal patrol vessel using a data analysis software called CIFER. Advanced features such as the Chirp-Z transform and composite window optimization are used to extract high quality frequency responses. An accurate, robust and linear transfer function model is derived for yaw and roll dynamics of the vessel. To evaluate the accuracy of the identified model, time domain responses from a 45-45 zig-zag test are compared with the responses predicted by the identified model. The identified model shows excellent predictive capability and is well suited for simulation and... 

This paper represents a numerical study on the effects of landslide initial submergence and its geotechnical and rheological properties on the characteristics of landslide-generated waves (LGWs) and landslide deformation. A number of 117 numerical experiments are performed using a two-layer Coulomb Mixture Flow (2LCMFlow) model on a real-sized numerical flume as a simplified cross section of the Maku dam reservoir, located in the Northwest of Iran. Three different initial locations are considered for landslide representing a subaerial (SAL), a semi-submerged (SSL), and a submarine (SML) landslide. Based on the numerical results, the majority of SMLs and in some cases SSLs generate tsunami... 

This paper empirically examines the hydrodynamic performances of squat submarines under the resistance and wave tests beside numerical investigation of pressure drag reduction techniques. Despite vast information about the operation of the streamlined fluid vessels, there is not much information about the geometries and hydrodynamic behaviors of squat vessels with L/D ratios below four. This study experimentally investigates the impacts of various relative depths and flow inclinations, intending to find drag, heave, and sway forces at the velocities of 0.5, 1.0, 1.5, 2.0, and 2.5-m/s. A one-tenth scaled model of a squat submarine is examined under the resistance and wave train scenarios as... 

Jacket-type offshore platforms play an important role in oil and gas industries in shallow and intermediate water depths such as Persian Gulf region. Such important structures need accurate considerations in analysis, design and assessment procedures. In this paper, nonlinear response of jacket-type platforms against extreme waves is examined utilizing sensitivity analyses. Results of this paper can reduce the number of random variables and consequently the computational effort in reliability analysis of jacket platforms, noticeably. Effects of foundation modeling have been neglected in majority of researches on the response of jacket platforms against wave loads. As nonlinear response of...