فهرست مطالب

Maritime Technology - Volume:9 Issue: 15, Autumn-Winter 2021

International Journal of Maritime Technology
Volume:9 Issue: 15, Autumn-Winter 2021

  • تاریخ انتشار: 1400/01/12
  • تعداد عناوین: 12
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  • Homayoun Yousefi* Pages 1-9

    This article aims to determine the main factors affecting the fast and reliable loading and unloading of the dry bulk terminal in the Imam Khomeini Port with an emphasis on reduced rate of loading and unloading in order to improve the performance of the port. In this study, the actual loading and discharging statistics data related to the port used previously as validated databases. A linear regression method used for calculating and final analysis in order to analyze the data and obtain the results by using the econometric method. The overall results of this study indicate that in the first model-independent variables of a technical defect of ship equipment, delay in separation, and displacement of cooling equipment affect the dependent rate of loading variable and this effect is indirect. In the second model, independent quarantine variables, technical defects of ship equipment, and the displacement of the cooling equipment influenced by the rate of unloading the dependent variable and these effects are indirect.

    Keywords: Port performance, Bulk Terminal, Ship equipment, Delay in separation
  • Hassan Sayyaadi*, MohammadSaid Seif, AliAsghar Abniki Pages 11-15

    In this paper, we present experimental results of one optical fiber acoustic sensor in shallow water. Output trend of sensor is investigated primarily comparing with the change of acoustic amplitude of transmitter and then the frequency response of sensor is determined. The results show that, the optical fiber sensor has linear trend comparing with a standard hydrophone and its frequency response is similar to that of hydrophone. The results show that the optical fiber sensor output has equal trend comparing to a standard hydrophone. The results also show that, the frequency response trend of optical fiber sensor at 0.7- 5 kHz range is similar to that of a standard hydrophone.

    Keywords: optical fiber sensor, frequency response, heterodyne method
  • Reza Yousefi*, AmirAbbas Amooei, Masoud Amel Sakhi, Abdolreza Karimi Pages 17-27

    Soil plays an important role in any structure, so soil improvement has become one of the most essential parts of construction projects. This study investigated influence of sawdust admixture on inshore sandy soil stabilized by zeolite and urease enzyme. One of the problems that environmental engineers encounter with is accumulating waste materials ،sawdust is one of these materials. One way for reducing these side products is reusing them, especially for soil improvement. Sandy soil with uniform granulation (SP) due to it’s incoherence is one of the most problematic kind of soils. Therefore, sawdust with zeolite has been used to improve soil engineering properties and the results have been compared with the effect of calcium carbonate precipitation (CaCO3) on the soil. Today, by advancement in various sciences and knowledge boundaries elimination in various fields, new and environmentally friendly materials can be used as an alternative method to traditional materials. One of these substances is urease enzymes, which are obtained from natural sources such as Jack Beans or bacteria’s activity such as Sporosarcina pasteurii. Samples in this study were made with 4, 8 and 12 percent by weight of zeolite and 4, 8 and 12 percent by weight of sawdust and were cured for 7, 14, 28 and 45 days. According to compaction test results, by increasing zeolite and sawdust’s percentage, optimum moisture content has been increased and maximum dry density decreased. The results of unconfined compression strength (UCS) test showed that the samples with 4% sawdust, 8% zeolite and calcite precipitation has about 9% increase in maximum strength compare with the samples without calcite precipitation and with higher zeolite content. Also, the rupture strain of samples with calcite precipitation was higher than the samples without it.

    Keywords: Soil improvement, Urease enzyme, Zeolite, Sawdust, UCS test
  • Samira Babaei*, Rouhollah Amirabadi, Mahdi Sharifi Pages 29-49

    Probabilistic seismic demand models (PSDMs) for typical South Pars fixed pile-founded offshore platforms, utilizing probabilistic seismic demand analysis (PSDA) have been presented in this study. It expresses the probability that a system experiences a certain level of engineering demand parameter (EDP) for a given intensity measure (IM) level. Utilizing Bin approach, 80 ground motion records have been selected. A three dimensional (3D) nonlinear model has been generated considering the effects of soil-pile-structure interaction (SPSI) and analyzed for each ground motion. The process involves a modal analysis to determine natural frequency as well as a static pushover analysis to establish yield values, and mode shape information, and finally 80 dynamic time-history analyses to determine demand, given IMs. With the probabilistic models being traditionally conditioned on a single seismic IM and single EDP, the degree of uncertainty in the models is dependent on the IM and EDP used. The present study evaluated optimal PSDMs build from 16 IMs against a wide range of EDPs in levels of local, intermediate and global. From a large combination of IM-EDP pairs, a selection of the optimal pairs has been made owing to the criteria of practicality, effectiveness, efficiency, and sufficiency. Results indicate the absolute superiority of velocity-related IMs compared to acceleration, displacement and time-related ones for most of EDP types. In particular, Housner Intensity-Global Drift and Specific Energy Density-Global Ductility (in global level), Housner Intensity-Jacket Drift (in intermediate level) and Housner Intensity- TopDeck Differential Settlement (in local level) result in optimal pairs. Conversely, Sa(T1, 5%), the widely used IM in probabilistic assessment of fixed pile-founded offshore platforms, demonstrates relatively poor performance in predicting the demand parameters.

    Keywords: Probabilistic Seismic Demand Model, Probabilistic Seismic Demand Analysis, Intensity Measure, Engineering Demand Parameter, Fixed Pile-Founded Offshore Platform
  • Pedram Eedalat*, Esmaeil Hasanvand Pages 51-65

    Offshore oil terminals are a cheaper and safer solution than conventional shore terminals for unloading and loading tankers. There are several types of offshore terminals, including Catenary Anchor Leg Mooring (CALM) and Single Anchor Leg Mooring (SALM). Safety is crucially important for offshore terminals. However, over the past few decades, mooring accidents of permanent floating structures have occurred quite frequently in the last few decades. Most of these failures have been caused by fatigue load. T-N curves-based mooring system fatigue analyses for a CALM and SALM oil terminal are presented. Stress amplitudes are calculated based on the tension amplitudes of the mooring lines under the combined loading process due to wave frequency (WF) and low frequency (LF) motion. A comparison is made between CALM and SALM mooring fatigue designs based on the conditions of the Persian Gulf region. For simulation, the hydrodynamic response characteristics of terminals and tankers are first calculated using ANSYS AQWA software, and then the outputs are imported into ORCAFLEX software for fatigue analysis. The results show that under the same environmental conditions with the same tanker tonnage, the SALM terminal mooring system shows a greater fatigue life. The minimum fatigue life of the mooring system for CALM and SALM terminals occurs at near the touch-down position (TDP) and the near of connection to the seabed, respectively. It is revealed that by changing the value of minimum breaking strength (MBS) the fatigue life of the CALM and SALM terminals changes by 119% and 100%, respectively. It is also observed that by changing the amount of K value (the value for platted T-N curve), the fatigue life of the CALM and SALM terminals changes by the same amount. In all cases, the value of R (the ratio of tension range to reference breaking strength), in the mooring line of SALM terminal, although more tension is generated, the ratio of R is less and will improve the life of fatigue.

    Keywords: Mooring system, Fatigue analysis, T-N curve, Oil terminal, OrcaFlex
  • Yasaman Rezaie, Seyed MohammadHossein Sharifi*, Gholamreza Rashed Pages 67-78

    A common solution for oil and gas transportation in offshore fields is long distance pipelines. Flowing of High Pressure/ High Temperature (HP/HT) fluid may cause uncontrolled buckling because of material or geometry defects. In order to reduce damages and avoid buckling in unpredictable places, the controlled buckling concept is introduced. In order to trigger buckling in predetermined location, pipeline can be placed in snaked lay configuration. In this article, it is aimed to investigate the effect of geometrical parameters, i.e., laying wavelength, laying radius and offset angle of snaked lay configuration on the displacement of offshore pipelines, axial force and bending moment in post buckling stage under HP/HT condition. Then, these results are used to evaluate the global buckling failure. This work is performed by using nonlinear finite element analysis and pipe-soil interaction of as-laid pipelines is modeled by employing spring elements. The results of investigation show that different ranges of the mentioned parameters may cause the maximum difference in displacement, bending moment and axial force about 133.6%, 155%, and 30%, respectively. Investigation of global buckling failure determine the most critical section of pipelines and it is observed that as the curved section of pipeline shrinks, the possibility of global buckling failure will increase but the effect of laying wavelength is contrary and the failure will be decreased about 8.3%.

    Keywords: Offshore Pipelines, Snake Lay Configuration, High Pressure, High Temperature, Global Buckling Failure, Lateral Buckling
  • Mojtaba Pakian Bushehri, MohammadReza Golbahar Haghighi* Pages 79-91

    Surface piercing propellers are widely employed in high-speed crafts due to having many favorable features. These propellers operate at both submerged and semi-submerged states. In submerged state, to enhance the propeller hydrodynamic performance, the blades are usually manipulated through artificial ventilation by adding the air duct which is located at the propeller suction side. In current study, a 5-blade propeller proficiency has been studied under different operational conditions of 16 m catamaran vessel experimentally, the sea trial, and numerically using Computational Fluid Dynamics (CFD). The propeller behavior has been investigated under four sea trials while the propeller torque has been sampled at different engine states and vessel speed. The numerical study through CFD has been done to analyze the propeller behavior under different conditions, submerged and semi-submerged states. The numerical results have been validated by experimental observations. The propeller proficiency has been studied in two vessel motion stages which are pre-planing and post-planing. The results depict that the maximum torque is observed in submerged state at the last step of pre-planing mode while the engine speed is 2300 rpm. The propeller torque is reduced 10 to 16% at 2500 rpm in post-planning stage. In submerged state, the propeller proficiency is negligible at pre-planing mode.

    Keywords: Surface Piercing Propeller, Propeller Torque, Thrust, Submerged State, Semi- Submerged State, Computational Fluid Dynamics
  • Ehsan Taheri*, Ali Adeli Pages 93-105

    Considering both kinematic and dynamic constraints (kinodynamic constraints) of an autonomous underwater vehicle in a Kinodynamic path planning algorithm in a dynamic large-scale workspace is an NP-Hard problem. Computational and time complexity of the kinodynamic path planning problem increase in the order O (n2) by increasing numbers of moving obstacles, AUV Kinodynamic constraints, degrees of freedoms, and workspace dimensions. This paper proposes a Randomized Kinodynamic Sub-optimal Planning (RKSP) algorithm for a man-portable class AUV. The proposed algorithm solves the path planning problem by applying a randomized sampling-based method to exploring and expanding in the workspace. RKSP re-plans the path to avoid collision with moving obstacles in a cluttered environment through a behavior-based method.  RKSP consists of three main components that tightly coupled together. The first component is a Randomized kinodynamic Planning (RKP) module that generates the random offspring waypoints and plans a feasible path by considering the AUV kinodynamic constraints. The second component is a Numerical Path Optimization (NPO) module that prunes the inappropriate edges of the path and reduces the computational complexity. The third component is a Local-Reactive kinodynamic (LRK) module that re-plans the local path through the neighborhood waypoints to avoid collision with moving obstacles in an unknown environment. RKSP path planning method is evaluated through the three different scenarios in a narrow passage, maze-like space and complex space. Results demonstrate the planned path by the proposed method is feasible and the AUV tracks the path appropriately and avoids collision with moving obstacles. Also, the total numbers of waypoints reduce in comparison to the conventional randomized methods and the planned path is near to the optimal.

    Keywords: Autonomous underwater vehicle (AUV), Kinodynamic constraints, Randomized sampling-based path planning, Collision avoidance with moving obstacle
  • Saleh Taleshamiri, Rouzbeh Shafaghat*, Mostafa Mohebbi, MohammadAli Mahdipour, Mahdi Esmaeili Pages 107-118

    One of the important features of the heavy-duty internal combustion engine is power density in such a way that the limitations created by the engine's features and accessories are the main challenges in evaluating the performance and power enhancement of advanced diesel engines. In other words, the complexity and limited performance of some of these devices do not allow the use of different power enhancement methods. Among these limitations, temperature constraints are one of the main challenges in the power enhancement process. In this study, the feasibility of increasing the power of the R43L MTU4000 heavy rail diesel engine has been considered. In this regard, the limitations of turbocharger inlet temperature as one of the basic performance challenges of the engine have been investigated using a one-dimensional simulation. For validation, the simulation results from the GT-SUITE software are compared with the experimental results. In the results section, the influence of increasing fuel mass, decreasing the compression ratio (CR), and the start of injection timing (SOI) has been investigated. The results show that by raising the fuel quantity by 5%, the power increases by about 7.6%; however, this increase in power leads to an increase in the turbocharger inlet temperature by 20K. Due to the operating limitations of various engine systems, attempts were made to control the rise of exhaust gas temperature by reducing the CR. On the other hand, reducing the CR from 18 to 15 increases the BSFC by 2.5%, but these changes in the CR do not have a significant effect on the output power. Finally, to examine the SOI timing in the enhanced engine at the maximum speed and power, different SOIs are tested and the optimal point is determined.

    Keywords: Power density, Power enhancement, Exhaust Gas Temperature, Compression Ratio, Start of Injection Timing (SOI)
  • Seyed MohammadHossein Sharifi*, Abdolrahim Taheri, Ehsan Karimi Pur Pages 119-129

    Today, Iran's oil and gas industry requires maintenance, repair, renovation, and reconstruction methods for the existing platforms. It is essential to discuss the repair of offshore platforms since they mostly have been in service beyond their design lives and subjected to damages mentioned in the following. Furthermore, offshore platforms' increased number and service lives add to the need for the in-situ repair of offshore platforms. The most important reasons for the structural repair of offshore platforms include corrosion, fatigue, the collision of floating objects (e.g., vessels), the fall of heavy objects, and intensive storms. By considering the dent damage of platform members, which typically arise from the fall of heavy objects and the collision of floating objects, the present study investigates the damages resulting from such incidents during the operation of platforms and proposes the required repair methods. The repair methods include grouting, member replacement, mechanical clamps, and doubler plates. Once the experimental model of a dent-damaged member was validated, the repair methods were applied to the models, examining the strength of the members. The results indicated that the member strength reduced by up to nearly 40% at a dent depth as large as 0.3 of the member diameter (d=0.3D). However, the reduced strength could be compensated from 12% to about 125%, by applying the repair methods.

    Keywords: Fixed Steel Platforms, Dent Damage, Repair Methods
  • Mehdi Adjami*, Elham Zakeri Anarak, Amir Jabari Khameneh, Ahmad Rezaee Mazyak Pages 131-146

    Beach cusps are shoreline formations made up of various grades of sediment in an arc pattern. Many works are carried out to determine forming theories and effective parameters on cusps, and the standing edge wave and the self-organization theories are more acceptable. This study aims to investigate theories affecting cusps of Roudic port, located on Makoran coasts of Iran. The DHI MIKE software is used for modeling and the Madsen laboratory model is applied for the numerical-model calibration. A new method as Edge Wave and Run-up Comparison (EWRUC) is introduced, working by extracting the edge wave from energy density spectrum and comparing with run up, subsequently. This is a fast and simple (one dimensional) method for determining theory of cusp formation. Many scenarios adapted to the Roudic coast waves are based on monsoon and ocean waves. The results from EWRUC indicate that the theories of edge wave and self-organization are dominant in seasons of ocean-waves and monsoon-waves, respectively. EWRUC responses correctly to beaches that are similar to Roudic beach.

    Keywords: Beach Cusps, Edge Wave Theory, Self-Organization Theory, Mike 21 BW Module, Roudic Coasts
  • Ali Ghasemi*, Rouhollah Amirabadi, Ulrich Reza Kamalin, Ahmad Rezaee Mazyak Pages 147-155

    The wave overtopping phenomenon at rubble mound breakwaters is one of the most important issues during the past few years and always plays a unique role in the design process of such structures. Most modeling studies in the overtopping measurment have been based on experimental methods and numerical modeling of wave overtopping from porous breakwater with pre-fabricated armour layer, under irregular waves has been less investigated. In this study, FLOW-3D software was used to calculate overtopping discharge. To assess the accuracy of software results, first, for three of modeled wave heights in the laboratory, numerical modeling was performed and the comparison between numerical and experimental overtopping results showed about 15% error which is acceptable considering the differences between numerical and experimental modeling characteristics, errors and uncertainty in numerical modeling. In the following, numerical modeling for concrete pre-fabricated Xbloc, Antifer, and Tetrapad armour units with different arrangements has been performed. The comparison between results shows that the Antifer armours have the least overtopping and the regular arrangement of Xbloc has the most.

    Keywords: Rubble mound breakwater, pre-fabricated armour units, overtopping, FLOW-3D software