نشریه مهندسی دریا
پیاپی 36 (پاییز و زمستان 1401)

This article presents a case study of numerical simulation of effluent in Konarak plant. by collecting data related to the case study which includes data such as output water characteristics of desalination (water concentration, discharge, temperature, outlet geometry), environmental conditions including wind speed in the region, the velocity of water flow, tidal velocity, tidal depth, and sea surface profile, to launch a numerical distribution model pollution at the seashore have been investigated using Cormix11 software at different depths and the effect of important parameters of effluent distribution on distribution and considering environmental conditions have been studied.Numerical results show that increasing the discharge of effluent leads to more salinity in the sea. but in some cases, it can be managed with flow velocity and tidal time so that increasing discharge has less effect on water distribution in the sea.

The morphodynamic status of the coasts is considered as a preliminary estimate of the risk of rip current formation that can be used for shoreline management. Rip currents are a common type of nearshore cycles that can have a major impact on any area of ​​the coast, and lead to the drowning of many people in the sea every year, so predicting these currents will help save lives. In this study, the beach state model (Ω-RTR) has been used to estimate the risk of rip current formation in vicinity of Bushehr coastal waters of Iran. By examining the characteristics of waves, tidal phenomena and sediment in 16 stations of Bushehr province, an initial assessment of the potential for the formation of rip current was performed. The results show that the coasts of Bushehr province are mainly the wave dominate and with the advance from north to south of the coastline, the state of the coast has changed from Ultra-Dissipative to Dissipative and in the central and southern stations of Bushehr province are more likely to expand the rip current.

Assessing the ultimate strength of the stiffened plates forming the ship structure is the first step in assessing its ultimate strength. Over time and increase the life of the structure, failures such as cracks reduce the load-bearing capacity of the structure. The main purpose of this paper is to present a machine learning method based on XGBoost algorithm to calculate the ultimate compressive strength of stiffened plates with crack failure using the results of multiple finite element analyzes. To achieve the best possible results from the XGBoost algorithm, some of the hyperparameters in this algorithm have been optimized using the Bayesian optimization method. The results of this method show that the accuracy of using the optimized XGBoost algorithm is much higher than conventional methods based on linear regression.

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.

The research objective was to identify and map the tidal zones that play a decisive role in integrated coastal zone management. Methodology designed based on the expert interpretation of the spatial boarders of the High Astronomical Tide (HAT), the spring and neap tides on the Sentinel-2A satellite images of 2018 with a spatial resolution of 10 meters to determine the risk of long-term flooding, supratidal and subtidal zones, respectively. In the coastal region of Bushehr province, an area of 81,000 hectares is subject to long-term flooding, 15,000 hectares are subject to monthly flooding, and 53.5 thousand hectares are subject to daily flooding. The results showed that up to 62% of the coasts of Bushehr province are tide-dominated coasts. Implementation of sustainable land use in the coastal region of Bushehr province is not possible without considering this risk. However, these lands are suitable for developing aquaculture, salinity, and mangrove forestry.

Bulbous bow optimization for ship is one of the ways to increase the efficiency of the ship through its hydrodynamic performance. In this study, with the aim of STAR-CCM +, the effects of changes in bulbous bow length for the KCS ship on hydrodynamic behaviour investigated. For this purpose, the leng3th of the bulbous bow was reduced by 5%, and increase 5%, 15% and 25% compared to the baseline, and then simulations were performed on three Froude numbers of 0.22, 0.26 and 0.30. Their results of the simulations show that with reducing the bulbous bow length by 5%, the total resistance in the three Froud number increased, respectively, but increased the bulbous bow length the total resistance reduced. Also, with increasing Froude number, the effect of the bulbous bow length will be more influence in reducing the total resistance.

Accurate Attitude estimation/ localization of robots for research, industrial, military, etc., applications has always been a challenge for designers. The purpose of this research is to present an attitude estimation method based on simple principles of low-pass and high-pass filter in the Complementary Filter with Adaptable gains of the least squares method for combining inexpensive sensor information for navigation of an underwater robot with dolphin motion scenario. The proposed adaptive algorithm; automatically calculates the complementary filter gains according to the measurement error and eliminate the need for manual adjustment or the use of fixed gains according to the device dynamics. Proper  performance of the proposed adaptive complementary filter for estimating the attitude of the underwater robot in field tests; confirms the advantage of this method for compensating for noise and time-varying bias inexpensive sensor.