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In this research study, effects of the draught and sheet height in pontoon floating sheet-breakwaters on the transmission and reflection coefficients against irregular sea waves was investigated. The project has been carried out using an experimental method within a wave flume of Soil Conservation and Watershed Research Institute. The incident waves were irregular and the wave spectrum was JONSWAP. The range of wave heights varied between 2 and 12cm and their mean periods were set to be between 0.63 and 1.26 seconds. To investigate the effect of draught in pontoon breakwaters, three experimental model with similar breadth and different draughts of 8, 10 and 12 cm were tested. Also, in order to investigate effect of sheet height in pontoon sheet breakwaters, sheet heights with 8, 16 and 24 cm were examined and compared without sheet case. The water depth was set to be 60 cm. The number of waves for each test was 250.

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In the current study, the step floating breakwaters were under consideration to improve the π type floating breakwater performance. By means of physical modeling 180 experiments were carried out in the wave flume for different geometric and hydrodynamic parameters including 2 and 3 step FBs. Result were then compared with standard π type FB with the same width. To be able to compare experimental results, kHi50 (which is an incident wave characteristics with transmission coefficient less than 0.5) was introduced. Results obtained through this study show that using step floating breakwater can be enhanced the hydrodynamic performance as well as reducing the construction material. In addition by increasing the width of steps, FBs performance was improved. Comparison of 2 and 3 step floating breakwaters reveal that the performance of each type is dependent on the draft depth. However it can be concluded that with increasing the step width, the difference of their performance is decreased.

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One of the major and effectual issues in designing of floating breakwater is its geometry. In this study, effect of geometry of floating breakwater on wave transmission coefficient for the periods ranging from 0.63 to 1.26(s) will be discussed using Flow_3D software, which is mainly based on trapezoidal geometry and curvature in various sections.
First, the numerical results of the base model were verified against the experimental model and then seven various geometries are designed in two groups. For the first group, the draft was assumed to be constant and to provide this particular draft, different geometrical sections were examined, using various masses and densities. In the second group, the cross-sectional area, mass and hence density were assumed to be constant and the proposed models were evaluated at different drafts. Finally, within the range of periods stated, the geometry having the best performance and economical is suggested for the related projects.

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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%.

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In the field of port design or protection of marine structures, one of the important things is predicting the performance of breakwaters against radiation waves. A type of breakwater that today, in addition to being able to be quickly installed, moved and reused in areas with similar conditions, maintains the water connection between protected space and open waters, is a floating breakwater. One of the factors influencing the performance of floating breakwaters is the geometrical parameters of the floating breakwater section. In this research, the numerical investigation of the effect of geometrical parameters of rectangular floating breakwater in single-row and double-row state on its hydrodynamic performance and wave transmission coefficient in ANSYS-AQWA software for wave periods in the range of 3 to 7 seconds has been investigated. For verification, the results of the present numerical model were compared with the laboratory results of Ji Deng et al. in (2019), which is in good agreement. The results showed that the use of a rectangular floating breakwater with the ratio of the height of the structure to the width of the structure in the range of 0.35 to 0.45 has the best performance. Also, increasing the mass of the structure against short-period waves improves performance and reduces the forces on the restraining cable and while in the face of long-period waves, reducing the mass of the structure improves the performance of the rectangular floating breakwater.