نشریه مهندسی دریا
پیاپی 37 (پاییز و زمستان 1401)

Coastal walls (dyke) are one of the methods of protecting the coast against coastal erosion and destructive forces of waves. The purpose of this study is to simulate the wave collision with the coastal dyke and compare the results with the laboratory model. Open FOAM open source software and K-ω SST turbulence model were used to simulate the amount of wave consumed by the coastal dyke. Taking into account the different conditions for modeling, a total of 45 experiments were selected to run the program. Modeling was performed in two general conditions with and without structures and for 3 heights of the structure, 3 different positions of the structure and 5 wave heights. The results showed that the absorption of forces has increased compared to the unstructured state and it can be said that the presence of the structure has been able to play a role in the dissipation of wave force up to 10 times compared to the unstructured state. The intensity of force changes in the structure is a function of wave height and this effect decreases with increasing wave height. Under different wave heights, the farther the structure is from the wave generating tank, the less force is applied to the structure.

Due to the range of hazards threatening the navigation of vessels such as collisions with other passing vessels, collisions with structures such as breakwaters, and collisions with the bottom of vessels with the seabed, the design and use of fixed and floating signs should be considered. These signs, in addition to daytime operation, should also be equipped with portable lights to navigate during the night. Since the maritime industry is international, these signs must have the same standards in terms of the shape, color, and rhythm of the lights These standards are developed by IALA. In this study, by reviewing international standards, navigation signs are first introduced and the use and characteristics of each of these signs are determined. In the following, as a case study, the location of these signs by using principles has been done for Tombak port and Lavan oil wharf.

This study presents a novel sensitivity-based finite element model updating approach to estimate structural parameters using output-only data. A quasi-exact sensitivity relation based on transmissibility data is introduced. Partially measured structural responses are included in mathematical formulations to address incomplete measurement problems and improve the accuracy of the sensitivity relationship. The least-squares algorithm is used to solve the normalized set of equations, and also a weighting approach is used to improve the parameter estimation results. The performance of the proposed method is evaluated based on numerical data of a ship structure model. Appropriate approaches have been used to select the excitation points and optimal sensor placement. The stability of the proposed method against measurement and mass modelling errors, and incompleteness of the measured responses are studied.

Estuaries and bays are areas with a wide range of hydrodynamic and morphological phenomena. The existence of this diversity in environmental processes will lead to complex and sometimes unknown interactions in their structure. Understanding the behavior and environmental conditions of these beaches will improve the attitude of coastal users for better management of these areas. Many classifications have been made by researchers to understand the behavior of this coastal environment. The dimensionless VU parameter is a numerical parameter to facilitate speed, accuracy as well as cost reduction in the classification of this coastal environment. This parameter classifies the estuaries into three categories: tidal domination, wave domination, and mixed energy, based on the relative strength of the tides and the river flow relative to the wave infiltration. Each of these classes has its own behavioral characteristics. The purpose of this study is to identify the type of performance of the North Persian Gulf estuaries and sensitivity measurement The dimensionless VU parameter in the classification of morphodynamic class of Persian Gulf estuaries. Morphological classification was used as the basic criterion for validation and Hayes hydrodynamic classification was used as a comparison tool. For this purpose, data from observing the trend of changes from satellite images, wave data and tides and meteorology have been used. To classify the dimensionless parameters of the estuaries, the tidal amplitude, the area of the estuaries and the tidal prism in the estuaries have been calculated. The results of morphological classification indicate that the study area is dominated by tides and the results of Hayes hydrodynamic classification with 96% accuracy have presented similar results to morphological classification. In contrast, the dimensionless parameter VU with poor accuracy of 53% presented poor results in classification. By examining the calculation results, the error rate of the dimensionless parameter VU in small estuaries and tidal domains has been determined. By defining the ratio of wave height to tidal amplitude (H / TR), regression lines of difference intervals, the dimensionless parameter VU with morphological classification is determined. It was also found that in a constant ratio of wave height to tidal amplitude, with increasing wave height, the percentage of classification the dimensionless parameter VU error increases. And also at a constant wave height, with decreasing tidal amplitude, the percentage of the dimensionless parameter VU increases.

By investigating the research in the field of planing vessels, limited research has been conducted to investigate the behavior and other hydromantic parameters. Given that such vessels can have better hydrodynamic performance than similar vessels, research and study is one of the needs and priorities of designers. With this purpose, this study examines the effects of the transverse steps hydrodynamic element on the single hull planing vessel. Since researchers in this study are looking for general and not specific results, empirical research conducted on the Friedzema model, at three different deaerise angles as well as in different speeds and geometric parameters (different heights and locations steps) and at the exit of the experimental part of the research, the location and heights of the steps are expressed at different angles. Other output results of the present study are the process of building a new model of vessel that can simultaneously combine several models.

Today, marine transportation has a significant role in global trade. The characteristics of the containerized shipping have made the number of container ships grow every day and made significant improvements in the construction and operation of these ships.
In this research, the main dimensions of a container ship are optimized according to different objectives. This optimization aims to reduce both hydrodynamic resistance and the steel weight of the ship. Initially, the information needed for optimization is specified, and the problem's constraints are determined. Then, the optimization is done using the optimization tool of the genetic algorithm toolbox in Matlab software. Also, a software code is developed, and the optimization case is done using this code. The results show that the genetic algorithm can be used as a practical tool for optimizing the dimensions of the ships.

These days, the sea level rising and excessive harvesting of coastal aquifers has caused the intrusion of saltwater into underground water sources. In this study, the performance of the use of cut of wall, discharge well, and their simultaneous use in preventing saltwater intrusion has been evaluated in a laboratory model and under different scenarios. The results show that the appropriate use of the wall will reduce saltwater penetration by 15%. In addition, the use of a discharge well with flow rates of 0.065, 0.13, and 0.2 liters per minute will cause the return of salt water wedge by 5, 30, and 37%, respectively. The results of the simultaneous use of the discharge well with flow rates of 0.13 and 0.2 liters per minute and the cut of wall showed that the salt water wedge has retreated by 38 and 41%, respectively.

Floating breakwaters are good alternative to the so-called fixed base breakwaters, which, in addition to having the main purpose of protecting the beach from waves, also maintain the water connection between the sea and the protected area. Researchers in order to increase the efficiency and increase the performance range of floating breakwaters, have done many researches on their effective parameters. In this research, due to improve the performance of the rectangular floating breakwater, the effect of using straight transverse ducts with a rectangular cross-section and transverse ducts with a geometric design modeled after the Tesla valve on the performance of the floating breakwater using ANSYSAQWA software was investigated. In this modeling, floating breakwaters with a height of 4 meters and an immersion depth of 2 meters were analyzed under the influence of waves with a height of 1 meter and in the range of wave periods (3-8) seconds. The results showed that compared to the rectangular floating breakwater model in the period (3-8) seconds, Using a straight channel in the body of a rectangular floating breakwater up to an average value of 20.9% and using a duct with a geometric design modeled on the Tesla valve in the body of a rectangular floating breakwater improves the performance of the structure up to an average of 20.3%.

The use of step at the bottom of the hull is one of the effective factors in reducing the resistance and increasing the stability of the Planning hull. The presence of step at the bottom of this type of hulls creates a separation in the flow, which reduces the wet surface on the hull, thus reducing the drag on the body, as well as reducing the dynamic trim. In this study, a design space was created by making changes to the three input parameters. Input parameters include the linear speed of the hull, the distance from the step from the transom and the change in the step height across the hull. The present study was carried out using the Computational Fluid Dynamics (CFD) coupled with Response Surface Method (RSM). The Computational Fluid Dynamics simulation was done by StarCCM+ software. The design of experiments and the Box–Behnken design method were used to select samples and the Kriging model for the Response Surface Method was used. Genetic Algorithm and screening method were also used to find optimal points. Output parameters include Drag and Lift force on the hull, the total hull trim. The results of the sensitivity analysis on the input parameters show that the hulling speed is the most influential parameter on the value of the output parameter.