مهندسی دریا
Meysam Salarijazi
Abstract
Estimation of the water level in river’s tidal limit is a suitable tool for the tidal flood management for rivers that are located in coastal areas. In this limit, propagation of tidal waves along the river to the upstream and combination of these waves and upstream flood discharge leads to an ...
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Estimation of the water level in river’s tidal limit is a suitable tool for the tidal flood management for rivers that are located in coastal areas. In this limit, propagation of tidal waves along the river to the upstream and combination of these waves and upstream flood discharge leads to an increase in flood plain limit and risk of damage. In this study, the reach between Ahvaz and Khorramshahr in Karun River is selected as case study and different linear and non-linear models are investigated for prediction of water level as a function of flood discharge of upstream. The analysis is performed for two cases considering the nature of tidal flood. In first case, total recorded data is investigated while in second case tidal flood data is extracted based on peak over threshold series analysis. Analysis of residuals of models in two cases show that the linear models are not acceptable, therefore the transformed nonlinear models that are a form of linear models are considered for modeling too. The power equations with improved coefficient of determination, relatively constant variance and normal distribution of residuals of models are concluded from detailed analysis in calibration parts for two cases. These selected models are used for validation part for two cases. The results confirm the acceptability of these models considering their simplicity and better efficiency for first case than second case.
مهندسی دریا
Morteza Bakhtiari; Shahriyar Shemshaki; Masoud Sadri nasab
Abstract
With the advent of technology and the expansion of human needs, the use of water platforms such as seas, oceans, and the recognition of methods and solutions for the design and implementation of marine structures is becoming increasingly clear.The semi-submerged platform is one of a variety of submarine ...
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With the advent of technology and the expansion of human needs, the use of water platforms such as seas, oceans, and the recognition of methods and solutions for the design and implementation of marine structures is becoming increasingly clear.The semi-submerged platform is one of a variety of submarine platform platforms, which, according to the features of the platform, is mainly used for extracting deep-sea oil and gas resources. In this research a semi- submersible platform under performance condition using ANSYS finite element software is numerical modeling and It is under regular waves. The platform's geometry is based on a platform built in 2012, and the data used in this study is about the average 20 years of Caspian waves.The degree of displacement, rotation, and force of diffusion has been obtained in degrees of freedom and are compared with each other. to apply regular waves Airy theory has been used. The result of this study show that In the loading of regular waves, the two parameters of the wave period and the wave propagation angle were the determining factor in the displacement and the platform time, as well as the dispersion force resulting from the collision of the wave with the platform. Also, the results show that at a 90 degree angle of the wave with the platform, the motion state at 2 degrees Z, Ry was close to zero and was the largest amount of time around the X axis.
مهندسی دریا
Vida Atashi; Mehdi GHomeshi
Abstract
In this paper, the effect of in phase or out of phase fluctuation of two tandem circular cylinders with PTC on FIM is investigated. Flow-Induced Motion (FIM) is a phenomenon that frequently occurs when slender structures are subjected to a transverse fluid flow.VIV and galloping are the most common phenomena ...
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In this paper, the effect of in phase or out of phase fluctuation of two tandem circular cylinders with PTC on FIM is investigated. Flow-Induced Motion (FIM) is a phenomenon that frequently occurs when slender structures are subjected to a transverse fluid flow.VIV and galloping are the most common phenomena in FIM which occurs due to interaction between shear layers and wakes of upstream cylinders. In this paper, the effect of tandem spacing on FIM of two circular cylinders with PTC is investigated by visualization. The power harness graphs for upstream, downstream and synergy was extracted with VIVACE. The VIVACE consists of a rigid bluff body that is mounted on an elastic base and exposed to fluid flow. The mechanical energy from the cylinder vibration is also transmitted by a PTO to a generator. Normally, the harness power in galloping region increases with increasing in flow velocity and Reynolds number. Unlike what was expected, drops and jumps in Power harness in the velocity range of 0.9
مهندسی دریا
Negin Donyavizadeh; Rouzbeh Shafaghat; Morteza Dardel; Saeid Mohammadzade Negharchi
Abstract
High speed craft with the wide and various uses of entertainment, sporting, commercial and military, usually has a top speed of 30 knots. Due to the limitations of the design, use of propulsion system is a key issue, with regard to the desirable features surface-piercing propeller, their use in the propulsion ...
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High speed craft with the wide and various uses of entertainment, sporting, commercial and military, usually has a top speed of 30 knots. Due to the limitations of the design, use of propulsion system is a key issue, with regard to the desirable features surface-piercing propeller, their use in the propulsion system of the vessel, has been very useful. High efficiency, no restrictions to increase the diameter, resistance equipment supplied propeller removed, the proper functioning of cavitation, are examples of these features. To achieve the best efficiency and thrust requirements, requires accurate determination of the coefficient of hydrodynamic thrust and torque. Given the importance of determining the coefficients and their dependence on various physical parameters and geometric, it is necessary to understand the effect of these parameters on the hydrodynamic coefficients, so in this study, experimental tests and collect data using sensitivity analysis, the weight of each parameter and the interaction of parameters ُsurface-piercing propeller to evaluate the hydrodynamic coefficients on the propeller thrust, propeller torque, and therefore performance, is desired. Based on the results obtained, the parameters of step angle, ُskew and compared to other parameters, have the greatest impact in changing the propeller efficiency, while changing the ratio Immersion, the change will have little impact on efficiency and propeller.
مهندسی دریا
M Moore; A. Firouzian nejad; S. ZiaeRad; A. Eidani nezhad
Abstract
The interest in bi-stable structures comes from their ability that these structures can have two different stable equilibrium configurations to define a discrete set of stable shapes. The geometrical changes occur with no need to continuously consume power, and mechanical hinges to preserve the structure ...
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The interest in bi-stable structures comes from their ability that these structures can have two different stable equilibrium configurations to define a discrete set of stable shapes. The geometrical changes occur with no need to continuously consume power, and mechanical hinges to preserve the structure in each stable shape.It is known that asymmetric composite laminates can have bi-stable response to different kind of loadings. In this research, the non-linear temperature-curvature relationship for the asymmetric composite laminates is studied using Rayleigh–Ritz technique. Attention is focused on studying the effect of material temperature dependency and resin layers; especially in the bifurcation point by use of analytical method. To this end, the well-known analytical theories are extended and used to consider the temperature dependency of material. The results obtained from the theory are then compared with the finite element simulations results and a good correlation is obtained. Finally, an experimental investigation is carried out and several specimens with [90/0]T, [70/–20]T and [70/20]T compositions were manufactured. In order to study the effect of resin layers, optical microscopy is utilized and the exact thickness of different layers in the manufactured specimens is determined. The thermal responses of the manufactured plates were measured and used to validate the results obtained from the analytical theory and finite element simulations
مهندسی دریا
hossein bahrami; samad emamgholi zadeh
Abstract
Accurate estimation of sediment concentrations in hydraulic sediment transport from different viewpoint such as sediment discharge estimation of river, selection of hydraulic structures and etc. are important. With respect to importance of this issue in this study for prediction of sediment concentration ...
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Accurate estimation of sediment concentrations in hydraulic sediment transport from different viewpoint such as sediment discharge estimation of river, selection of hydraulic structures and etc. are important. With respect to importance of this issue in this study for prediction of sediment concentration of Karun river multi-layer perceptron artificial neural network (ANN / MLP) was used.For this purpose 125 field data including bottom concentration, flow velocity, nearest distance from the beach, and thetotal depth of flow and flow depth was used.Three statistical metrics namely mean absolute error (MAE), root mean square error (RMSE) and coefficient of determination (R2) were used to evaluate the performance of ANN model. The result shows that MLP model with one hidden layer, Sigmoid transfer function and 5 neurons have best structure in the modeling of sediment concentration of Kroon River. The R2 and RMSE value is equal to 0.953 and 63.37 mg/l in training stage and 0.752 and 203.02 mg/l in testing stage, respectively. Finally, the sensitive analysis also showed that the nearest distance from the beachand flow depth had the most and the least effect on the sediment concentration, respectively.
مهندسی دریا
Parisa Koochak; Seyed Mahmood Kashefipour; Mehdi Ghomeshi; Ahmad Fathi
Abstract
One of the ways to control the erosion in the outer bend of rivers is to use spur dikes. In recent years, the efficiency, affordability and environmental suitability of traditional spur dikes has been criticized. Therefore the importance of adopting methods which are both cost-effective and eco-friendly ...
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One of the ways to control the erosion in the outer bend of rivers is to use spur dikes. In recent years, the efficiency, affordability and environmental suitability of traditional spur dikes has been criticized. Therefore the importance of adopting methods which are both cost-effective and eco-friendly has been addressed. The bandal-like spur dike is a combination of a permeable and an impermeable spur dike, which is usually used in Indian Sub-Continents for riverbank protection and improvement of navigation conditions in alluvial rivers. It is made of bamboo therefore it is inexpensive and environmental friendly. In this research the effect of the permeability percentage of the bandal-like structure on the maximum scour depth around it in a 90 degree mild bend flume and in submerged condition is investigated. Therefore a series of impermeable spur dikes (0% permeability) and bandal-like structures with (33,50 and 64) percent permeability are placed in the flume and examined under four different Froude numbers (0.21, 0.23, 0.26, 0.29). The results showed that the maximum scour depth around the bandal-like structure is considerably less than the maximum scour depth around impermeable spur dikes. Also by increasing the permeability percentage of the bandal-like structures the maximum scour depth around it decreases.
مهندسی دریا
AliAsghar Moghaddas Ahangari; Hamid zeraatgar; seyed khalil shariati
Abstract
In designing of a marine vehicle, derivation of hydrodynamic coefficients of the equations of motion is very important. For derivation of these hydrodynamic coefficient's various methods such as analytical-experimental methods, Computational Fluid Dynamic (CFD) method and model test can be used. Among ...
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In designing of a marine vehicle, derivation of hydrodynamic coefficients of the equations of motion is very important. For derivation of these hydrodynamic coefficient's various methods such as analytical-experimental methods, Computational Fluid Dynamic (CFD) method and model test can be used. Among These methods, due to the limitations of analytical-experimental methods and computational fluid dynamic method, the most accurate method is model testing.Empirically derived coefficients, which obtain in the marine laboratory, use to simulate the behavior of a marine vessel in the International Maritime Organization (IMO) maneuver test and determine the vessel's maneuverability.Due to differences in the marine laboratory equipment and test methods and to ensure the accuracy of results, standard models are tested and the results are compared against the results provided by the International Towing Tank Conference (ITTC).Accordingly, this article describes the process of model testing and derivation of the coefficients for the Esso Osaka benchmark vessel, using static and dynamic testing with Horizontal Planar Motion Mechanism (HPMM) in Shohada-e-Khalij-e-Fars national marine laboratory and compare the results with the results provided by the international towing tank conference.
مهندسی دریا
M Kordnaeij; S.A Asghari Pari; S.M Sajjadi; M Shafai Bajestan
Abstract
In this study a porous obstacle was used to evaluate the performance of permeable obstacles for control of turbidity current. To build mathematical obstacle porous strata of 2.1 * 2.1 cm was used. 10 m long steep flume experiments are conducted. Tests were conducted in a double-dip 0 and 2.5 percent. ...
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In this study a porous obstacle was used to evaluate the performance of permeable obstacles for control of turbidity current. To build mathematical obstacle porous strata of 2.1 * 2.1 cm was used. 10 m long steep flume experiments are conducted. Tests were conducted in a double-dip 0 and 2.5 percent. Discharge constant in all tests was 0.7 liters per second. Feed concentration of 20 grams per liter of the concentrated flow and viscous flow in the upstream and downstream concentrations were measured porous barrier. Concentration was measured with use of a sampler flushing. The results showed that the porous barrier stepped porous barrier to the flow is better. Porous barrier stair staircase behind a thick flow of porous barrier and prevents over-stepped the stairs to the amount of sediment discharge reduced more.
مهندسی دریا
Tooba Heidari; nima shahni karamzadeh; Javad Ahadiyan
Abstract
In this study, results of experiments about the trajectory and the advance velocity of inclined and convergent rectangular surface jet into stagnant ambient have been presented. In order to discharge process simulation was used a flume with 3.2 m length, 0.6 m width and 0.9 m height and a rectangular ...
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In this study, results of experiments about the trajectory and the advance velocity of inclined and convergent rectangular surface jet into stagnant ambient have been presented. In order to discharge process simulation was used a flume with 3.2 m length, 0.6 m width and 0.9 m height and a rectangular channel with 6 cm width. Discharge channel was designed in the four angle of convergence 12.5, 25, 45 and 90 degree. This channel injected the jet stream to form of tangent to the surface of ambient and in three different slopes 0, 4 and 8 percent. Receiving fluid had been prepared from urban water. As well as the jet fluid had been prepared from the salt liquidation in water and in three concentrations 5, 15 and 45 gr/l. After running the experiments and using of images routing process were analyzed the data. In this regard, hydraulic and geometric parameters on the trajectory and the advance velocity of jet was investigated. According to the results, increase the slope and decrease the angle of convergence causes increase in length of trajectory and decrease in the advance velocity of jet. Reduce the densimetric froude number causes decrease in length of trajectory. Also, in order to investigate of influence of convergence on the movement path of flow, by comparison of trajectory in convergent channel and simple channel, More relative advance was seen in convergent channel. Finally, using of the data analysis, relation between advance velocity of jet and dependent parameters was determined with RMSE=0.034.
مهندسی دریا
Mahboobeh Golaghapoor Kami; Mostafa Jafarzadeh Khatibani; Etemadaldin Rabei Gholami
Abstract
For all new ships sea trials should be carried out as a part of the delivery from the yard to the ship owner. An important part of the delivery sea trial is to determine the speed capability of the ship in the contractual condition, which is traditionally deep, calm water and no wind, at some specified ...
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For all new ships sea trials should be carried out as a part of the delivery from the yard to the ship owner. An important part of the delivery sea trial is to determine the speed capability of the ship in the contractual condition, which is traditionally deep, calm water and no wind, at some specified loading condition. However, it is seldom possible to perform this particular test under such conditions, and when the test is done in other conditions, the result is corrected back to the contractual condition. The correction can be of a significant magnitude. The correction procedure can be influenced by different parameters such as wind resistance, shallow water effect, sea currents and added resistance due to diffraction. There are different experimental methods for correction of measured speed. Since the latter parameter is the most important between others, In this article added resistance due to diffraction has been calculated for three ships using existing methods and comparisoned with the speed correction result of shipbuilder company (Hyundai Heavy Industries). The results show considerable deviation between HHI sea trial speed correction method and other methods. So HHI added resistance calculation method needs to be revised.
مهندسی دریا
seyed khalil shariati; s m
Abstract
In the conceptual design of a submarine quick estimation of hydrodynamic coefficients of a body and appendages is needed. In these methods, formulas are given for different coefficients and for the control surfaces, using two-dimensional factor provided for hydrofoil in wing sections theory books, are ...
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In the conceptual design of a submarine quick estimation of hydrodynamic coefficients of a body and appendages is needed. In these methods, formulas are given for different coefficients and for the control surfaces, using two-dimensional factor provided for hydrofoil in wing sections theory books, are suggested. A Critical point in using these coefficients of wing sections theory books is, these coefficients are calculated for far from the free surface and for near the free surface is needed to be improved. Then in In the present work, Based on the assumption of potential flow and boundary element method a computer program has been developed to calculate the coefficient of hydrofoils with various sections in near the free surface. results in submerged is in full compliance with experimental and numerical results and in the near the free surface, these results are consistent with good accuracy.
مهندسی دریا
Abdullah Eidani nezhad; A.Kabir Kabiri; S.H. Dibajian; A. Mardan
Abstract
There is an increasing interest in the marine industry to use composites to improve the hydrodynamic and structural performance of naval structures. The materials used within the composite are commercially available, and it is important the development of the right mix of fibers, resin and laminate lay-up ...
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There is an increasing interest in the marine industry to use composites to improve the hydrodynamic and structural performance of naval structures. The materials used within the composite are commercially available, and it is important the development of the right mix of fibers, resin and laminate lay-up that provide the desired mechanical and environmental performance for marine application. In this paper, to improve the stiffness and control the geometry of the blades of a marine propeller made of carbon/epoxy genetic algorithm to determination of optimal stacking Sequence is used. Using this method will minimize the deformation of tip blades. The optimization process has executed by linking ABAQUS and MATLAB software. Optimal angles of blade propeller obtained by using this process.
مهندسی دریا
maryam yaghoubzadeh; Afshin Danehkar; Bahman jabbarian amiri; Sohrab ashrafi
Abstract
We used 6 criteria and 29 indicators for determination environmental sensitivity of geomorphologic aspects of the coastal area in Hormozgan. Identification and determination of the important coefficient showed exclusivity and wilderness are the most important coefficients and industrial dependency had ...
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We used 6 criteria and 29 indicators for determination environmental sensitivity of geomorphologic aspects of the coastal area in Hormozgan. Identification and determination of the important coefficient showed exclusivity and wilderness are the most important coefficients and industrial dependency had the lowest priority for determination of the environmental sensitivity in this regard.Moreover, in order to, determine importance and priority of sensitivity of ecosystems in the study area 9 physical structure were studied in both shore and coastal zone (include: 4 structure in coastal area and 5 structure in shore area). According to the results, Inundated mudflat and in shore area and Low flat land in coastal area are of the most important sensitivity .After reviewing the physical structure and preparation map of overlaying this structure, sensitivity zoning was developed coastline in Hormozgan province on 5 class of sensitivity, Very low sensitivity, low sensitivity, moderate sensitivity, high sensitivity and very high sensitivity. Zoning of sensitive physical structure in coastal zone shows the lowest extent areas are in Low sensitive degree and the most extent areas are in moderate sensitive degree in physical sensitivity classes.According to the results, shore area in Hormozgan province that includes 11.35% of coastal zone has high physical sensitivity. In shore area Inundated Mudflat, Rocky shore and Inundate beach have most physical sensitivity and inundated process is the most important phenomena on the structures mentioned the shores. The most sensitive of coastal area is Low flat land.
مهندسی دریا
morteza Bakhtiari; FARZAD ORAK
Abstract
Sea Walls are constructed to protect coastal against of waves and prevent water to coastal. In order to properly understand the behavior of these structures must have proper information of loads to the structure. One of the main significance loads over the seawall is wave’s loads. Weight forces ...
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Sea Walls are constructed to protect coastal against of waves and prevent water to coastal. In order to properly understand the behavior of these structures must have proper information of loads to the structure. One of the main significance loads over the seawall is wave’s loads. Weight forces the walls, Weight backfill, Seawater weight on the heel wall and Forces exerted on the beach other forces that enters the coastal wall. Considering the importance of seawalls study on the stability of these structures has been the subject of study. In order to achieve the objectives of the study, three scenarios include changes in the geometry of the wall and Soil properties. In present study four geometry vertical, inclined, convex, concave, are considered and modeling with Flac 3D software. The results of this study showed that the minimum of horizontal and vertical displacement are about convex seawalls and the maximum of them is about vertical concave seawalls. Also the results showed that in the higher shear strength of soils the minimum of horizontal and vertical displacements occurred.
مهندسی دریا
ahmad rezaie mazyak; mehdi sanayei
Abstract
The main goal of using floating breakwaters is to provide the sheltered area of calm water in the coastal zone. In present research, for analyzing hydrodynamic modeling of pontoon floating breakwaters the AQWA module of ANSYS software has been selected. The main parameters that have been considered in ...
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The main goal of using floating breakwaters is to provide the sheltered area of calm water in the coastal zone. In present research, for analyzing hydrodynamic modeling of pontoon floating breakwaters the AQWA module of ANSYS software has been selected. The main parameters that have been considered in this research are pattern of significant wave height, wave period, and draft and width of floating pontoon. Wave transmission coefficient can be obtained from water surface changes in any point of leeward. Results of numerical modeling demonstrate that a pontoon floating breakwater with relative width greater than 0.4 have appropriate performance. Also it has been found that the transmission coefficient of pontoon floating breakwaters will be in the range of 0.35 to 0.60 if the relative wave period changes in the range of 1.5 to 4.
مهندسی دریا
hossein bahrami; Mehdi ghomeshi; Seyed Mahmoud kashefi por; Seyed Ali Akbar Salehi Neyshabouri
Abstract
Density current is one of the relative motions that occur between two fluid layers, even in fluids with small difference in density. Differences in specific mass may cause of temperature, suspended material, solved material or a combination of them. These currents are so important specially in cases ...
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Density current is one of the relative motions that occur between two fluid layers, even in fluids with small difference in density. Differences in specific mass may cause of temperature, suspended material, solved material or a combination of them. These currents are so important specially in cases such as water containing sediment entering rivers into dam reservoir, seas or lakes and can also have destructive effects such as sedimentation in reservoir and estuaries to the sea and coastal areas as well as changing bedding sets Offshore areas (Kostic & Parker, 2005). The identification of type of move and change in current regime on the characteristics of the flow movement is very important. Investigation of flow movement, require to recognition of velocity profiles. A physical modeling used for this proposes and measurement and investigation of velocity on the body of current carried out. The results showed that the Coefficients of velocity profiles in wall and jet regions were respectively 2.83, 0.87 and 2.08 for sub critical flow and 1.174, 1.062 and 2.09 for super critical flow, also the maximum height of the supercritical flow was lower than sub critical flows. The other results showed that the velocity reduced 14 to 19 percent and the flow depth increased 21 to 32 percent affected by hydraulic jump respectively. Also, in some cases, large differences were observed between the results of the analytical jump relationship and measured data.
مهندسی دریا
Mohammad Khedmati; Mahdi Omidali; Roohollah Hadipoor Goodarzi
Abstract
A common way to join dissimilar materials in industrial applications is to use adhesives. Marine industries use this kind of joints for attaching main hull to superstructure of the ships. Most previous researches have focused on composite-composite joints, while a few of them are devoted to aluminum- ...
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A common way to join dissimilar materials in industrial applications is to use adhesives. Marine industries use this kind of joints for attaching main hull to superstructure of the ships. Most previous researches have focused on composite-composite joints, while a few of them are devoted to aluminum- sandwich panel joints. This study focuses on the numerical static strength analysis of a typical aluminum-sandwich panel T-joints and improving its strength through a novel design. The results of numerical analyses are in a good agreement with those of the experimental tests and confirm the accuracy of numerical analyses. In analyzing the adhesive between joint elements, contact elements and cohesive zone model (CZM) in ANSYS as well as nonlinear analysis is used. Results show that change in joint geometry considered in this paper, caused a 7.25% increase in vertical failure load of the joint. This increase in strength of joint attained in a situation that because of the merging of the joined parts, the process of construction became easier.
مهندسی دریا
Saeed Shadkam; EatemadO’Din Rabei Gholami; Nasim Al Ali
Abstract
Each Ship Can Transfer Safely in certain Zone According to It`s Stability and Regime of Sea State. Therefore, if Ship Have to Pass in Specific Condition that Sea State is Jumpy, Should be Provide One or More Anti Rolling Methods to Survive. The Purpose of this Article is Reduction and Control of Rolling ...
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Each Ship Can Transfer Safely in certain Zone According to It`s Stability and Regime of Sea State. Therefore, if Ship Have to Pass in Specific Condition that Sea State is Jumpy, Should be Provide One or More Anti Rolling Methods to Survive. The Purpose of this Article is Reduction and Control of Rolling Motion to Reach Proper Hydrostatic Stability with Assessment Activity of Two Methods Using Commonly to Reduce Rolling Motion. This Methods are Activated Anti Rolling Tanks And Gyroscope. In this Article Trying to Solve Its Equations in Matlab Software and Compare it to Reach More Activity Method. The Results Shown that Anti Rolling Method Proposed for Large Displacement Ships and Otherwise Gyroscope is More Activity for Passenger Ships and Small Vessels.
مهندسی دریا
Morteza Bakhtiari; seyed mahmood kashefipour; Mehdi GHomeshi
Abstract
One application of spur dikes is ensure navigability of rivers Through regulation and stabilization of sufficient width and depth, balance changes for the development of depth and The radius of curvature.Nowadays, spurs are also employed for promoting environmental conditions along a riverbank. One of ...
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One application of spur dikes is ensure navigability of rivers Through regulation and stabilization of sufficient width and depth, balance changes for the development of depth and The radius of curvature.Nowadays, spurs are also employed for promoting environmental conditions along a riverbank. One of the important topics abut spurs is their protection against scouring that has been less studied. One of the simple and economic ways for protection of spur against scouring is using riprap. Riprap is very common because it is easily available, cheap and simple for construction.Since using, spur dikes to protect riverbanks spatially in bends is very common, This research was carried out in order to investigate the effect of the structure stability. The purpose of this study is evaluation of depth-placed riprap for protection of spur dike in 90° Bend. In order to achieve the research objectives, one riprap size of inch diameter was used. Ripraps are placed in 3 depths ( ), and used for 3 lengths of spur(15%,20% and 25% width of flume), two angles (90 and 120 degree) and three longitude distance (3,5 and 7 times of spur length). Parameters as variables in this study were selected which The results can be used in large rivers, including navigable rivers and the Gulf.The results showed that stability of ripraps are increased with increasing the depth-placed riprap and angle of spurs, whereas increasing in spur length and longitude distance decreases stability of ripraps.
مهندسی دریا
Ataollah Gharechahi; Mohammad , Rahimi
Abstract
In this paper the amount of pollution produced by boats with 2-stroke engines have been calculated, in different seasons in southern coast of Iran. The seasonal activity of boats is estimated based on the average of wide range of expert opinion whom familiar with these type of vessel according to crowd ...
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In this paper the amount of pollution produced by boats with 2-stroke engines have been calculated, in different seasons in southern coast of Iran. The seasonal activity of boats is estimated based on the average of wide range of expert opinion whom familiar with these type of vessel according to crowd wisdom theorem. Also the amount pollution per hours power of engine is derivates from similar international researches.The results show that the proportion of pollution from these boats is about 290 times greater than pollution from stern tube and deck machinery leakage from vessels in southern Iran. In particular, they are contains toxic compounds of BTEX which is generated in way of marine life near coastal waters. In spring and winter the pollution is greater than other seasons. with emphasis on the Persian Gulf and Oman Sea are the “Especial Area” and the threat of activity of boats on marine life; Suitable solution to reduce the pollution from these vessels, Should be in priority program of coastal countries especially the Islamic Republic of Iran .
مهندسی دریا
Seyed Amin Asghari Pari; Seyed Malek Mohagheghiyan
Abstract
Turbidity currents are one of the most fundamental factors that transferring sediment near the dam. In this article, the effect of roughness, pattern, height and the shape of roughness in the floor on controlling turbidity current are studied using finite elements numerical method by ANSYS-CFX. For solving ...
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Turbidity currents are one of the most fundamental factors that transferring sediment near the dam. In this article, the effect of roughness, pattern, height and the shape of roughness in the floor on controlling turbidity current are studied using finite elements numerical method by ANSYS-CFX. For solving turbulence equations are used K-e method. After calibrating of model has done, at the first, simulated flow without roughness and then three shape of roughness pyramid-shaped, round edge cylindrical and cubic with two alternative zigzag and consecutive, with 5 different height and for subcritical and supercritical flow regime are modeled. The results indicated that with the increase in height of the roughness and cross flow and with zigzag arrangement, reduced the turbidity current discharge. Also the effect of roughness on controlling subcritical turbidity current are more than supercritical flow.
مهندسی دریا
khosro fazelpoor
Abstract
In order to provide SST images, the sensor MODIS installed on Aqua Satellite EOS-1 was used. Applying lighting assessment out of images from Modis 21-Level 1B Calibrated Radiances -1km in Persian Gulf and the Bushehr sea station (Bouyeh) from global algorithm specified for above sensor was used to estimate ...
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In order to provide SST images, the sensor MODIS installed on Aqua Satellite EOS-1 was used. Applying lighting assessment out of images from Modis 21-Level 1B Calibrated Radiances -1km in Persian Gulf and the Bushehr sea station (Bouyeh) from global algorithm specified for above sensor was used to estimate the sea surface temperature. With function of Matlab software to extract data of satellite images, and GIS software to convert the matris obtained, the maps of sea surface temperature were used. Forty eight images taken in 2008, 2009, 2012, and 2013 were selected. Their correlation coefficient eventually was 0.75, 0.86, and 0.75 respectively. Likewise the special coefficient obtained as 0.86, 0.90, 0.94 and 0.86 respectively. Finally, taking the 31 band temperature into consideration for the years 2008, 2009, 2012 and temperature differences of bands 31 and 32 and the sensor angle as independent factors were used at Bouyeh temperature as an affiliated factor calibrated by SPSS software for global algorithm of Persian Gulf. In order to check the correctness the algorithm suggested, the sea surface temperature was re-examined with satellite images of the year 2013; the correlation coefficient 0.96 and 0.94 were obtained. The searching has shown that the depth with current sea and latitude have effect on sea surface temperature, and temperature balance specially in north and central latitude have contrary relation with depth.
مهندسی دریا
Mahpeykar, Omid; Masoud Sadrinasab; , Morteza Bakhtiari; , Nima Shahni karamzadeh
Abstract
Developed countries are using renewable energy in order to minimize emission of harmful gases, and many countries are studied new designs. Which uses of the later is increasing rapidly. One of the cleanest renewable ocean energy is using the potential of tidal energy. Studies show that the best place ...
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Developed countries are using renewable energy in order to minimize emission of harmful gases, and many countries are studied new designs. Which uses of the later is increasing rapidly. One of the cleanest renewable ocean energy is using the potential of tidal energy. Studies show that the best place for obtaining tidal energy in the Persian Gulf and is the Doragh Estuary, which is located in the northern part of the Persian Gulf. This estuary is the unique area in the Persian Gulf with more than 5 meters tidal range which has the potential to produces maximum tidal energy in this region.In this study, a physical model of Doragh estuary is constructed and employed a pumping system as well as a source of water to create tide in the model. Also two dams are made somehow in the model to reserve water behind these dams during ebb and flood. A propeller which is connected to a turbine is fixed to one of the dams, and works during both ebb and flood in which transfers movement of propeller into electricity. Electrical current is connected to an instrument which show the amount of produced electricity in the model. The results of the model show that by increasing tidal range, electricity increases electricity exponentially. In this experiment the model run with different scenarios to get maximum efficiency which is recorded to 15% during flood and producing of electrical power can increased by 30 to 50 percent during both ebb and flood.
مهندسی دریا
A. Mohammad Rahimi; Mohammad Khedmati
Abstract
Grillages consisting of intersecting beams are supporting shell structures of the ships in different places such as bottom, deck and sides. Different methods available for strength analysis of plated grillages are studied from the viewpoints of characteristics and limitations. Finally, the way to assess ...
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Grillages consisting of intersecting beams are supporting shell structures of the ships in different places such as bottom, deck and sides. Different methods available for strength analysis of plated grillages are studied from the viewpoints of characteristics and limitations. Finally, the way to assess the strength of such structural elements is investigated. This study is based on preparation of a soft-ware for analysing the grillages. Using the software, it is possible to analyse grillages used in the ships’ structures for any type of boundary and loading conditions that are simply selectable by users. Getting the required input data from the user, elastic deflections and stresses induced as a result of applying concentrated or distributed loads are calculated at the intersections of the longitudinal and transverse members, relieving the need to complicated numerical calculations.