مهندسی دریا
Ahmad Hajivand; Aghil Daraie
Abstract
The prediction of ship resistance is the most important part of the ship's hydrodynamic design. Nowadays, computational methods are used as a common tool for this purpose. Ship total resistance calculation by using two phase numerical method based on the Reynolds-averaged Naiver–Stokes solution ...
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The prediction of ship resistance is the most important part of the ship's hydrodynamic design. Nowadays, computational methods are used as a common tool for this purpose. Ship total resistance calculation by using two phase numerical method based on the Reynolds-averaged Naiver–Stokes solution requires high computational power. The idea of total resistance decomposition based on the physical cause is a basic principle in the ship hydrodynamic. In the proposed hybrid method, wave making resistance part is calculated by using Michell Integral and viscous part is computed by numerical solution of one phase viscous flow for double body condition. Computations are performed for 10 velocities from Fn = 0.06-0.62 and at each velocity the percentage of every component calculated. Hybrid method reduce computational time. To investigate the results, tow phase simulations are performed for a SWATH vessel. On average, there are 7% difference between the results obtained from hybrid and two phase method and computational time in hybrid method is 97% less than two phase method.
مهندسی دریا
Hamed Jalil Masir; Rohollah Fattahi; Elham Ghanbari Adivi
Abstract
Sediment transport phenomenon is considered as one of the important and Effective factors in hydraulic performance and morphological structure of the coasts. In addition, stable development, engineering proceedings and the selection of the most appropriate protection method for organization and stabilization ...
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Sediment transport phenomenon is considered as one of the important and Effective factors in hydraulic performance and morphological structure of the coasts. In addition, stable development, engineering proceedings and the selection of the most appropriate protection method for organization and stabilization of the coast, are depends on the quantity of sediment load. Therefore, the focus of this study is generally to estimate sediment transport rate, assess the impact of coastal forest cover (Green Belt) on decreasing sediment transport rate exposed to tsunami wave trend and to obtain the parametric model to each coastal area using SPSS software. Experiments were performed on the effectiveness of a mangrove tree to reduce tsunami energy, by a simulated polyethylene synthetic shrub structure, for two rectangular and triangular tree layouts, 3 input wave height of 6, 9 and 12 cm, constant and horizontal slope of the coast, 0.35 mm sediment diameter and in terms of presence and absence of cover.. The results of this study show that despite forest cover, 41.17% of coastal erosion and scour are prevented and it helps to stabilization and restoration the coasts. Also considering conditions such as triangular layout selection and increasing cover density, 7.57% and 11.20% respectively, leading to the improvement of the coastal condition. Finally, the parametric model and the experimental equation for estimating the sediment transport rate with the correlation coefficient equal to 0.95, proposed as well.
مهندسی دریا
Masih Moore; Ahmad Firouzian-nejad; Saeed Ziaei-Rad; Abdollah Eidany-nejad
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. In this study, the stability characteristics and thermal response of a bistable composite plate with different asymmetric composition were considered. The non-linear finite element method (FEM) was utilized to determine the response of the laminate. Attention was focused on the temperature dependency of laminate mechanical properties, especially on the thermal expansion coefficients of the composite graphite-epoxy plate. Also the effect of including the resin layers on the stability characteristics of the laminate was investigated. The effect of the temperature on the laminate cured configurations in the range of 25°C to 180°C was examined. The results indicate that the coefficient of thermal expansions has a major effect on the cured shapes. Next, optical microscopy was used to characterize the laminate composition and for the first time the effect of including the resin layers on the actuation loads that causes snapping behavior between two stable shapes was studied. The results obtained from the finite element simulations were compared with experimental results and a good correlation was obtained.
مهندسی دریا
Mohammad Hosein Noralah Dezfouli; amir abas kamanbedast; Alireza Masjedi; Mohammad Heidarnejad; Mohammad Hosein Purmohammadi
Abstract
One of the measures to control the hydraulic jump at the downstream of hydraulic structures and to provide required sequent depth is to use a stilling basin with sudden contraction. Previous studies have shown that in this basin the jump length increases compare to the classical jump. On the other hand, ...
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One of the measures to control the hydraulic jump at the downstream of hydraulic structures and to provide required sequent depth is to use a stilling basin with sudden contraction. Previous studies have shown that in this basin the jump length increases compare to the classical jump. On the other hand, it has been shown that roughening the bed is a measure that can be used to decrease the jump length. Therefore, it can bring a question that by roughening the bed of sudden contraction stilling basin how much can decrease the jump length? Therefore, in this study the effect of roughness on jump length at the mentioned stilling basin has been investigated. The tests have performed in a flume of 12-meter-long, 0.8-meter-wide and 0.7-meter height. The contraction ratio was 0.33 and the Froude number ranged between 2 to 10. The results have shown that the roughness can decrease the jump length up to 31% compare to the classic jump and can decrease up to 12% compare to the smooth bed of sudden contraction stilling basin. The jump length is equal to the USBR type II. It was found that the roughness can decrease the roller jump up to 20 percent compare to the sudden contraction of smooth bed.
مهندسی دریا
Mohammad Ahmadnejad; Abbas Fazelinia
Abstract
The ship behavior should be studied with respect to channel width and depth, because of the existence of hydraulic and hydrodynamic effects in navigable channels and waterway. The most important parameters that designer should consider are Squat, resistance, slamming, bow body force and suction. Accurate ...
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The ship behavior should be studied with respect to channel width and depth, because of the existence of hydraulic and hydrodynamic effects in navigable channels and waterway. The most important parameters that designer should consider are Squat, resistance, slamming, bow body force and suction. Accurate prediction of hydrodynamic parameters for operational ships in shallow water are essential to avoid grounding. Hydrodynamic parameters for Series 60 hull Vessel's in shallow waters are experimentally investigated in this thesis using models with coefficient, CB=0.8 and The Experiments were carried out in towing tank in different condition Critical speeds for vessel's can be obtained based on experimental results. This leads to an increase in ship efficiency and reaching the optimal speed and dratht in channels. The results have been compared with those obtained from analytic, numerical and empirical methods. It should be noted that fake walls were designed to carry out this study after designing the floating model. The unique characteristics of the fake walls was adjusting the channel width. It was possible to receive and register the sensors using PLS program. Throughout the experiment all the mechanisms were monitored automatically by the examiner.
مهندسی دریا
Mohammadreza Negahdari; Ruhollah Karimpuor; Iman Khatami; Babak Ahmadpoor
Abstract
Motion control may be effective by reducing the heave and pitch of a high speed vessel especially in planing hull. In order to decrease these motions, the foil was effective technique rather than other methods. High speed crafts are known to have rough water problem is essentially one of compromise between ...
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Motion control may be effective by reducing the heave and pitch of a high speed vessel especially in planing hull. In order to decrease these motions, the foil was effective technique rather than other methods. High speed crafts are known to have rough water problem is essentially one of compromise between speed and seakeeping performance. The objective of this research is to predict the performance of the planing craft M Hull in term of seakeeping before and after incorporating with stern foil. Prototypes of the hull have been modeled in 3D using Rhino and is running at the head sea of the regular wave and its responses are obtained by unsteady RANS simulations using StarCCM+ software. The obtained results of RAO heave and pitch motions are presented at various Speed Cofficient. Basically, there are advantages by incorporating the stern foil at aft of the vessel to achieve the planing mode which it gives significant effect to motion reduction by increase of speed in special region. For example, at speed 40 knots by adapting with Stern foil the heave & pitch RAO trim down by 19.31% and 26.44% respectively.
مهندسی دریا
Ali Asghar Moghaddas Ahangari; Seysd Mojtaba Alavijam
Abstract
One of the important goals of designing of planing boats is to achieve higher speeds, one of the major obstacles to this issue is longitudinal instability.In this research, a new method is proposed to solve the longitudinal instability of steped planing boats. In this method, using the transverse curvature ...
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One of the important goals of designing of planing boats is to achieve higher speeds, one of the major obstacles to this issue is longitudinal instability.In this research, a new method is proposed to solve the longitudinal instability of steped planing boats. In this method, using the transverse curvature or variable deadrise angle of the body, the instability of boat has been corrected. Two bodies, called Nimala1 and Nimala2, were tested in National Iranian Marine Laboratory. The main difference between the two transverse curvature bodies is that Nimala1 has a constant deadrise angle and nimala2 has a variable deadrise angle in a section. To determine the effect of the variable deadrise angle on the longitudinal instability, each of the models has been tested up to longitudinal instability. Due to the equipment installed during the test of the model in the towing tank, it was not possible to measure the movement and therefore numerical analysis is used as a complement to the exprimental test. The results show that the variation in cross-curvature has a significant effect on longitudinal instability. By shifting the center of pressure to Aft, the delay of the porpoising was changed from 5.89 volumetric Fn in the fixed deadrise angle model, to 8.34 volumetric Fn in Variable deadrise angle model. Also, the resistance of this body is not significantly different from that of a body with constant transverse curvature, especially at high speeds.
مهندسی دریا
masoud hakamifard; Mahmoud Rostami-Varnousfaaderani
Abstract
One of the most prevalent ways for studying the submarine’s hydrodynamic behavior, like maneuvering, is calculating the hydrodynamic coefficients the hydrodynamic coefficients. In this paper calculation of hydrodynamic coefficients (up to third order) of an AUV using Computational Fluid Dynamics ...
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One of the most prevalent ways for studying the submarine’s hydrodynamic behavior, like maneuvering, is calculating the hydrodynamic coefficients the hydrodynamic coefficients. In this paper calculation of hydrodynamic coefficients (up to third order) of an AUV using Computational Fluid Dynamics (CFD) and Finite Volume Method(FVM) was performed. Therefore, a Myring body was chosen to simulate the unsteady maneuvering for surge, sway and yaw motions. The turbulence effects were modeled by k-ω sst turbulent model. The Planar Motion Mechanism (PMM) in two situations has been implemented to calculate the forces and moments for sway and yaw motions. Creating body motions in computational domain, the Overset mesh was used. Furthermore, the grid study was performed for investigating of the simulation accuracy. Then for calculating the coefficients, some six order polynomial equations were interpolated for forces and moments versus velocity and acceleration. The numerical results were compared with the results of (Prestero, 2001) . The relevant error for damping coefficients was between 0.8 to 12 percent. These values for added mass coefficients were between 0.8 to 37 percent.
مهندسی دریا
Amir Zarepour; Mehdi Behdarvandi Askar; Saham-eddin Cheraghi; vahid Zareii
Abstract
The aim of this research is to investigate the hydrodynamic status of Mahshahr export port. Initially, the modeling of tidal streams in the starting point of Khurmousa by the tidal inputs of Rahnamaian station was performed in logical manner and the results obtained from the inner point of Khurmousa ...
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The aim of this research is to investigate the hydrodynamic status of Mahshahr export port. Initially, the modeling of tidal streams in the starting point of Khurmousa by the tidal inputs of Rahnamaian station was performed in logical manner and the results obtained from the inner point of Khurmousa was calibrated with inputs from Imam Khomeini station port and satisfactory results were achieved. During the next stage, by considering the main aim of this research, a model specific to the area of export port of Mahshar was developed. Based on the results from field measurements and the results obtained from the model, the tidal amplitude balance in export port of Mahshahr is 4.25 meters, the maximum annual ebb is 2.25 meters and the annual minimum is 2 meters. The velocity of tidal streams in Mahshahr export port parallel to the channel and during the most part of the year is between 0.5 to 1 meters per second. The pattern of tidal streams is constant throughout the year and experiences no changes
مهندسی دریا
Ataollah Gharechahi; Esmaeil Shafizadeh
Abstract
In this research, the effect of weights that lose their lashing systems and can move freely in line with vessel breadths is investigated on ship roll motions. Therefore, the effect of friction and possible barriers that impeded on free movement of weights are neglected.To study the effects; weights with ...
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In this research, the effect of weights that lose their lashing systems and can move freely in line with vessel breadths is investigated on ship roll motions. Therefore, the effect of friction and possible barriers that impeded on free movement of weights are neglected.To study the effects; weights with different masses are hung on pendulum which is installed on an ocean going trawler model and vessel roll motions is being experimentally tested.The results show that whoever hanging weights can increase the center of gravity of vessel and decrease the vessel stability; but caused increase the period of roll motions. The findings of research also can be used in design of damping systems of roll motions.In addition, the experimental results are compared with numerical results based on the Strip Theory. The results show that the damping coefficient has important role in the accuracy of numerical results.
مهندسی دریا
mohammad ghanbar dezfouli; masoud dehghani; adel asakereh; behzad kalantari
Abstract
In the coastal areas and especially in the harbors, due to the presence of loose sandy sediments and structures under high lateral and vertical loads, the use of pile raft is a suitable choice for the foundation of these infrastructures. In this system, raft and piles are separated and a cushion is used ...
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In the coastal areas and especially in the harbors, due to the presence of loose sandy sediments and structures under high lateral and vertical loads, the use of pile raft is a suitable choice for the foundation of these infrastructures. In this system, raft and piles are separated and a cushion is used in the distance between the raft and the piles. The existence of reinforcement layers in the cushion such as the geogrid changes the behavior of the pile raft system. In this paper, the behavior of reinforced nonconnected pile raft with geogrid under vertical loading in sandy soils has been investigated by a laboratory studies. An automatic hydraulic jack were used in the load application and LVDT is used to measuring the settlement. The strain gages are installed at the tip of the piles to calculate the force applied to the piles. Tests were carried out under reinforced and non-reinforced condition. In non-reinforced case, the optimum thickness and pile spacing of the cushion and in the reinforced case, the optimal location of the first and second layer of the geogrid and the effect of the geogrid layers length on the load-settlement behavior and the share of the piles from the total load were evaluated. The results shows that the thickness of the cushion and the pile spacing have a significant effect on the behavior of the pile raft. The presence of geogrid layers in the cushion increases the bearing pressure and the share of piles from loads.
مهندسی دریا
Alireza Abdikian
Abstract
In this article, spectrum of the reflection, transmission and absorption of the thin metal nano-layer by using quantum hydrodynamic equations is studied. The thin metal nano-layer can be used to cover the equipment and devices to avoid detection which coated the outer surface of the submarines, ships, ...
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In this article, spectrum of the reflection, transmission and absorption of the thin metal nano-layer by using quantum hydrodynamic equations is studied. The thin metal nano-layer can be used to cover the equipment and devices to avoid detection which coated the outer surface of the submarines, ships, planes. It is also used the nano-layers to cover the various devices such as solar cells, glass reflex. In some devices, for example the solar cells, the more increase the absorption ratio, the more increase the efficiency and in some other devices, for example the reflex glasses, it is better to be high the reflection ratio. Hence, the study of the reflection, transmission and absorption ratio of electromagnetic waves are important in quantum plasma slabs. By combining the quantum hydrodynamic equations and the Maxwell's equations in the presence of a magnetic field can be obtained the coefficients of the reflection, transmission and absorption of electromagnetic waves in thin metal nano-layer in which we have taken the slab as quantum plasma. Clearly, it is shown that by taking term of the quantum Bohm's potential cause to appearance of the quantum refractive index for the Langmuir wave that this new refractive index does not have any similar relation in the classical plasma. Using the numerical values and the Mathematica software, the absorption coefficients have drawn in various conditions. This proposed method enables us practically to control the reflection or absorption power of electromagnetic waves in quantum plasma slab by adjusting a uniform external magnetic field.
مهندسی دریا
Mousa Damavandi; Rouzbeh Shafaghat; Morteza Dardel
Abstract
Anti-Rolling Gyro (ARG) is one of the useful equipment which is used for enhancing stability of vessels. ARG produces a moment against wave torque and reduces undesirable vessel roll based on gyroscopic concepts and using flywheel moment. The first step in designing ARG is flywheel design which exerts ...
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Anti-Rolling Gyro (ARG) is one of the useful equipment which is used for enhancing stability of vessels. ARG produces a moment against wave torque and reduces undesirable vessel roll based on gyroscopic concepts and using flywheel moment. The first step in designing ARG is flywheel design which exerts appropriate moment in order to reduce rolling of vessel with attention to the sea wave moments and angular velocity of the waves. According to direct relation of righting moment of gyro with mass moment inertia, in order to increase righting moment, it should be chosen a flywheel with high moment inertia, in the contrary, increasing moment inertia also leads to increasing mass of flywheel. In this study, with regards to conditions of waves of Persian Gulf, for optimizing of mass and moment inertia, non-dominated sorting multi objective genetic algorithm (NAGA-II) is used, in a way that minimum mass and maximum moment inertia will be gained. Finally, the dimension of all the flywheel optimal options are demonstrated in the form of pareto diagram, in order that performance conditions regarding parameters including mass and the number of gyros in a vessel based on gained results, are being investigated.
مهندسی دریا
Shahrzad Nikbakht; Ahmad Hajivand; Mostafa Jafarzadeh Khatibani
Abstract
Power requirements increase severely in rough weather because of added resistance induced by water wave. Amplitude of this additional resistance is between 15 to 30 percent of the ship calm water total resistance. Nowadays, one of the important issue in naval architect is to design a ship hull with minimum ...
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Power requirements increase severely in rough weather because of added resistance induced by water wave. Amplitude of this additional resistance is between 15 to 30 percent of the ship calm water total resistance. Nowadays, one of the important issue in naval architect is to design a ship hull with minimum added resistance that produce less greenhouse gas. There are several numerical viscous and non-viscous method like strip theory, panel method and RANS method. With respect to accuracy and cost calculations, 3-D panel method is the best choice for analysis ship behavior in wave. By using frequency domain Green's function 3-D panel method added resistance of S-175 containership is computed by far filed and near field approaches. To investigate the effect of wave incident and wavelength, calculations are performed in different incident angle and wavelength. Also by using an accurate and fast empirical validated method that have recently been proposed, added resistance in head sea are calculated for different wavelength and ship speed. Far field and near field results are consistent with good accuracy. Numerical and empirical results are compared with experimental that shows high accuracy results.
مهندسی دریا
m y; Ehsan Gharibreza
Abstract
The ultimate goal of the electrical industry is to supply reliable energy. Therefore, accurate and on time detection of faults have always been the main concern of electricical utility users. In recent years, the use of cables has grown steadily and has made it difficult to detect faults and locations. ...
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The ultimate goal of the electrical industry is to supply reliable energy. Therefore, accurate and on time detection of faults have always been the main concern of electricical utility users. In recent years, the use of cables has grown steadily and has made it difficult to detect faults and locations. If the cable network is intended for a particular application, such as a generator connection cable to industrial power grid, its importance will be increased, and the Lack of timely performance of the protection system will cause irreparable damage. In this paper, a novel method is proposed for detecting and determining the location of faults in cable using a combined wavelet transform algorithm and an optimized MLP network with a bee algorithm. In the proposed algorithm, two initialization modules and prediction analyzes are proposed to increase the selection capability. The algorithm is done by the DigSILENT and MATLAB software and implemented on the ship industrial cable network. The simulation results indicate an accuracy of 93% for the considered algorithm in determining the correct location of the fault.
مهندسی دریا
amin ghaemian; mohsen sadeghian kerdabadi; Manuchehr Manouchehr Fadavi Ardestani
Abstract
In this study ahead to solve the equations of the boundary layer on a plate Mthrkprdakhth is steady. It takes into account the energy equation, heat transfer components also be considered. The solution method used to solve nonlinear equations, the method is Lie group. The initial conditions using an ...
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In this study ahead to solve the equations of the boundary layer on a plate Mthrkprdakhth is steady. It takes into account the energy equation, heat transfer components also be considered. The solution method used to solve nonlinear equations, the method is Lie group. The initial conditions using an iterative algorithm for solving differential equations with relatively good accuracy estimates. Then, the fourth-order Runge-Kutta method to solve environmental values across functions to be obtained. Using the results of the numerical solution of the boundary layer heating speed and simulate the effects of radiation coefficient, the speed and suction factor to be considered in the boundary layer. Finally, to assess the results of the numerical solution methods Lie group, the results of earlier shooting method is used. A comparison of numerical solution methods and techniques shooting show Lie group Lie group method convergence addition to high speed, good accuracy as well.
مهندسی دریا
m b; m b; Nassim Ale Ali; m s
Abstract
Nowadays demand for renewable and reliable energy sources due to the global warming, environment pollution and global energy crisis is of utmost importance in offshore engineering. As a result of recent developments in wind industries extracting energy from offshore wind resources has a growth. A number ...
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Nowadays demand for renewable and reliable energy sources due to the global warming, environment pollution and global energy crisis is of utmost importance in offshore engineering. As a result of recent developments in wind industries extracting energy from offshore wind resources has a growth. A number of researches are carried out in the field of land based wind turbines but investigations about floating wind turbines as a consequent of their dynamic behavior complexity are still limited and further more detailed surveys are required. This paper presents an open source and public simulation code for the analysis and design of floating offshore wind turbines. The dynamic behavior due to environmental and inertial loads is obtained using a fully coupled comprehensive numerical tool implemented in MATLAB. blade element momentum theory used to determination of aerodynamic loads on wind turbine as well as Panel method and Morison's equation to calculate the hydrodynamic loads considering the instantaneous position of wind turbine system. The results show the domination of aerodynamic loads on wind turbine dynamic behavior as well as stability of structure due to the great difference between values of dominate aerodynamic excitation frequency and system natural frequencies.
مهندسی دریا
Moloud Ariyan; Ahmad Hajivand; Etemadodin Rabei Gholami
Abstract
Maneuverability is an important quality of marine vehicles. Hydrodynamic coefficients of ship and rudder should be derived to simulate maneuvering tests. These coefficients can be obtained by using captive model test and empirical formula. Accuracy of rudder hydrodynamic coefficients is important to ...
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Maneuverability is an important quality of marine vehicles. Hydrodynamic coefficients of ship and rudder should be derived to simulate maneuvering tests. These coefficients can be obtained by using captive model test and empirical formula. Accuracy of rudder hydrodynamic coefficients is important to calculate rudder force as the most influence force in ship maneuver, precisely. Empirical formula usually are correspond to single rudder ships and for twin rudder ships numerical or experimental method are used. In this paper, by using numerical method and simulation of static towing test in computational fluid hydrodynamic environment for different angles, linear and nonlinear rudder hydrodynamic coefficients are calculated. Also, fluid velocity field around rudder is obtained to investigate separation for high rudder angle. The comparison of simulated results with the available experimental shows a very good agreement among them.
مهندسی دریا
Masoumeh beitabdollah; Mohammad Esmaeildoust; Amer Kaabi
Abstract
With growth of Technology, With growth of technology, the needs for data and information security over communication channels are necessary. Providing information security in marine environment includes communication between ships and also ships with ground station are one of the most important issues ...
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With growth of Technology, With growth of technology, the needs for data and information security over communication channels are necessary. Providing information security in marine environment includes communication between ships and also ships with ground station are one of the most important issues in information security. In order to provide Confidentiality, symmetric key cryptography algorithms such DES, 3DES, IDEA, RC6, Serpent and AES are presented by researchers. Different reports in literature are presented by researchers in order to compare the performance of these algorithms. Despite various considerations, the needs for deep comparison of these algorithms are needed. Therefore in this paper, deep consideration and comparison in the points of architecture, flexibility, security and speed of these algorithms are done. Based on the achieved results, the appropriate algorithm can be employed based on required flexibility, speed or desired levels of security. The result of implementation and comparison shows the advantages of AES algorithm in provided security and RC6 in speed of execution.
مهندسی دریا
mohammad pour amiran; mohammad yousefikia
Abstract
: In this research, reactive power compensation in the ship is considered as an auxiliary factor for improving generator conditions and improving the ship efficiency in terms of fuel consumption and emissions. To accomplish this purpose, a simplified electrical network is modeled for an all-electric ...
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: In this research, reactive power compensation in the ship is considered as an auxiliary factor for improving generator conditions and improving the ship efficiency in terms of fuel consumption and emissions. To accomplish this purpose, a simplified electrical network is modeled for an all-electric military marine vessel, including propulsion load, distribution loads, sensors, emergency loads and pulse loads (rail guns, aircraft launchers, etc.) Among these loads, pulsed loads have a more damaging effect on the voltage profile of power quality in the ship distribution system. Such loads often require high energy over a short period of time, which mainly causes problems in system power quality and in some cases leads to the destruction of the entire electrical system.In the following, the compensation effect of static capacitors is investigated on voltage profile improvement of a navy ship during a pulse load. The obtained result show that using their kind of compensating has a great impact on decreasing voltage sag and, on the other hand, the speed and torque curves of the propulsion motors will be more stable. All simulation is done in Matlab/Simulink environment and for various situation (different pulse load and static capacitors). Suggested method is robust and improve the parameters of power quality in all proposed scenarios.
مهندسی دریا
kazem sadati; hamid zeratgar
Abstract
In past few years two-dimensional theories in numerical, analytical and experimental solution have contributed in seakeeping and maneuverability of vessels specially planing crafts. Analysis of wedge water entry as a basic problem has wide application. Till now much research in different methods has ...
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In past few years two-dimensional theories in numerical, analytical and experimental solution have contributed in seakeeping and maneuverability of vessels specially planing crafts. Analysis of wedge water entry as a basic problem has wide application. Till now much research in different methods has been done on the symmetric and asymmetric of wedge water entry. in this study wedge water entry with transverse velocity (or oblique water entry) will be studied. Model testing is a powerful means to deal with the said problem, in this study oblique water entry of wedge has been conducted. In this regard for oblique water entry of wedge a setup has been designed and fabricated. using by the fabricated setup a set of oblique water entry tests on wedge of 40 degree deadrise angle in different vertical and transverse velocity are examined and the pressure distribution on the plates of wedge due to impact of water are recorded. The results are illustrated the importance of transverse velocity on the pressure distribution and magnitude of vertical and transverse forces on the wedge. The pressure distribution due to oblique water entry on left and right side of the wedge are not symmetry; owing to increasing of transverse velocity the difference pressure on two sides of wedge is increased, so the transverse force is increased and the vertical force is decreased.
مهندسی دریا
gholam abbas Boroujerdi; Amir Abbas kamanbedast
Abstract
One of the most important issues related to arc ducts is the erosion of the river bank in the outer arc, which is largely due to the existence of secondary currents, in which the mechanism of these currents was elaborated in the previous section. Protecting and fixing the river walls generally involves ...
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One of the most important issues related to arc ducts is the erosion of the river bank in the outer arc, which is largely due to the existence of secondary currents, in which the mechanism of these currents was elaborated in the previous section. Protecting and fixing the river walls generally involves both direct and indirect methods (relaxants and deviators). One of the most important diversion protection structures is river flows. In this research, hexapod materials were evaluated for scouring in permeable spills. The results obtained from the simulation show that the use of Hexapod spray with 12, 20, 27 and 35% permeability reduced scours by 17, 27.9, 38 and 45.3%, respectively, compared to the control without permeability. Increasing the permeability of the hexapod spoil reduces scouring around the spillway. Increasing the permeability of Hexapod spray guns from 12 to 35 percent resulted in a reduction of sputum by 34.1 percent. This phenomenon is due to the easier flow of water through the hexapod sprayer and creates less pollen, which reduces scouring. Also, with an increase in the landing value from 0.2 to 0.36, the scour is 11.8 times higher. Of course, it should be noted that increasing the landing number increases the permeability of the spillway to increase scouring. So that with the installation of permeable sprinkler 35% in the number of 0.2 and 0.36, respectively, we saw a decrease of 20 and 61% scouring compared to the control model, respectively.
مهندسی دریا
Morteza Bakhtiari; Ehsan Kamal pour asl; Javad Ahadiyan
Abstract
There is a different method for increasing the resistance and quality of engineering of soils, one of the most suitable ones is dynamic compaction. In this method, weights are released from the specified height and, as a result of collision with the ground, the soil will be compacted. In this research, ...
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There is a different method for increasing the resistance and quality of engineering of soils, one of the most suitable ones is dynamic compaction. In this method, weights are released from the specified height and, as a result of collision with the ground, the soil will be compacted. In this research, field experiments were initially initiated. Then using the results obtained in this section, the soil dynamic compaction was modeled. In order to do the modeling, the present study was conducted using FLAC two-dimensional software. Due to the implementation of various designs in the city of Abadan, the area was selected as the site of the project After field experiments, mechanical properties of the soil were extracted and then modeled with the definition of test patterns. The result of this research show that For all conditions of modeling, the maximum deformation of soil was observed in the hammer Cutoff area, which decreased in depth of soil. Also, the results indicate that effective stress in soil under dynamic density decreases with increasing depth.
مهندسی دریا
Reza Dezvareh; Parisa Mohammadi; Mohammad Hajitabar
Abstract
Wind-induced waves due to their high energy are one of the most important hydrodynamic phenomena in the sea, which are of particular importance in marine engineering. Considering the importance of prediction of wind-induced waveforms, in this study, the efficiency of the third-wave waveguide model in ...
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Wind-induced waves due to their high energy are one of the most important hydrodynamic phenomena in the sea, which are of particular importance in marine engineering. Considering the importance of prediction of wind-induced waveforms, in this study, the efficiency of the third-wave waveguide model in wave prediction (WaveWatch-III) has been investigated and the results of this model have been compared with the wave height obtained from the SW module software MIKE Is. In other words, in this paper, the prediction of wave characteristics is provided by the WW3 and SW models. To better compare the results of these two models, the environment and wind speed are considered to be the same. The results show that the WW3 conforms well to the results of the SW model, which will decrease with increasing water depth and distance from the coast, so that in deep water (approximate depth of water 500 m) and at intervals Offshore (50 km off the coast), the SW model provides more and more conservative data for wave characteristics. Also, the results of this study showed that the WW3 model would take more time to reach a steady state.
مهندسی دریا
hossein bahrami; Mehdi Ghomshi; Seyed Mahmoud kashefi por; Seyed Ali Akbar Salehi Neyshabouri
Abstract
It is well known that the shortage of water is one of the most serious problems that faces the mankind. Therefore the study and search for the phenomenon that have impact on the water reservoirs and other natural resources of water, is essential. One of the most fundamental phenomenons relating to water ...
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It is well known that the shortage of water is one of the most serious problems that faces the mankind. Therefore the study and search for the phenomenon that have impact on the water reservoirs and other natural resources of water, is essential. One of the most fundamental phenomenons relating to water reservoirs is the density currents. The importance of the investigation and analysis of the hydraulic behavior of density currents will be apparent when we consider the consequences of the occurrence of these currents and its effects on the erosion of water reservoirs and also the sediments that they cause to be deposited in these reservoirs. For example the incoming of these currents in water reservoirs will effect the biological activities, it may cause sediments in these water reservoirs or it might press down these sediments to the bottom of water reservoirs.