فهرست مطالب

International Journal of Coastal, Offshore and Environmental Engineering
Volume:5 Issue: 1, Winter 2020

  • تاریخ انتشار: 1398/11/23
  • تعداد عناوین: 6
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  • Hengameh Motamedi, Maryam Rahbani *, Abbas Harifi, Danial Ghaderi Pages 1-9
    Possessing precise water level data in any coastal area is crucial, for any coastal engineering or managements. One of the main processes responsible for a regular water level changes is tide. Due to its nature, tidal prediction is relatively easily accessible. However, the precision of the results depends on the number of constituents have been considered for the prediction. The aim of this paper is to identify the most relevant tidal constituents and their relevant amplitudes for tidal prediction in the Beris port, south of Iran, using artificial neural network (ANN). The main constituents in the area is obtained as M_2, K_1, S_2, N_2 and O_1. To regenerate the tidal condition considering these constituents two ANN methods has been applied including Feed Forward, and Radial Basis Functions (RBF). For the training and network test tidal data of the year 2017 has been considered. For the training a variety of months and constructions has been applied. For the Feed-Forward the Levenberg-Marquardt learning method has been considered. After executing different structures in terms of the number of neurons in the hidden layer and taking into account the minimum error and run time, the network with 5 neurons in the hidden layer and two months training was qualified. For the RBF, the radius of 2.5 has been qualified. The evaluated network of both Feed-Forward and RBF has been employed to reproduce tidal water level of the whole year 2018, and the results were compared with both field data and those derived from harmonic analysis. It was found that the three layers Feed-Forward network shows the best performance in tidal prediction with the correlation coefficient of 0.85, which is followed by RBF, with the correlation coefficient of 0.81.
    Keywords: Feed forward neural network, Radial Basis Functions, Tidal prediction, Beris port
  • Majid Ehsani, MohammadNavid Moghim *, Mehdi Shafieefar, Amir Mostaghiman Pages 11-23

    One of the issues that emerge from an efficacious design of berm breakwaters is an estimation of wave reflection. In the present study, the wave reflection of a multi-layer berm breakwater (MLBB) has been studied based on model experimentation. To gain this goal, two-dimensional model tests have been carried out in a wave flume at Tarbiat Modares University. Irregular waves were generated using the JONSWAP spectrum, under which the effect of various parameters like wave height, wave period, water depth, and berm elevation from still water level is investigated on the wave reflection. Achieved outcomes of this study propose a new formula estimating MLBBs wave reflection. Ultimately, the performance of the derived formula against the existing formulae proposed by other researchers is checked thoroughly. The results of the statistical evaluation indices divulge that the predicted wave reflection using the new formula is more accurate than the existing ones. Thus, it would be obvious that the present formula can provide a well-founded estimation of wave reflection on the MLBBs. Moreover, the new formula and those estimated by existing ones are validated by employing the data set exclusively used in drawing the comparison. This fair validation illustrates that the current formula is more accurate than the existing formulae.

    Keywords: Wave Reflection, Multi-layer berm breakwater, experimental study, Prediction formula
  • Rouhollah Amirabadi, Ahmad Rezaee Mazyak, Ali Ghasemi *, MohammadReza Khosravi Pages 25-30

    The Karun River is considered to be the longest Iranian river with 855 km length. The river is divided into two branches, 4 km away from the Arvand River, which is a branch of the Bahmanshir River in the north of Abadan, and another branch of the Namkarun River (the Azodi Channel) that flows into the Arvand River. The intersection of the Karun River and the Arvand River is important. Also, measuring and investigating of hydrodynamic phenomena have a vital role in recognizing and prediction the hydrodynamic changes in the region. Therefore, CTD and hydrographic studies were carried out for the Azodi Channel, which is the intersection of the Karun River and the Arvand River. These studies include measurements of marine phenomena such as tidal observations, water level changes, hydrography, topography, CTD and sedimentation. Studies have shown that floods of the Karun River have caused significant changes in the intersection of the rivers Karun and Arvand. Also, the sediment of the study area is fine-grained, but at the intersection of the rivers Arvand and Karun, it is coarse-grained. Sediment concentration is increased in depth, and the lowest and highest sediment concentrations are related to Karun station and Arvand Karun intersection respectively. Regarding the alignment survey, it was found that the current of the study area is mixed current, but mostly meridian. The flow of the Karun River is one of the parameters affecting the water level. So that if the current of the river is noticeable, it will prevent the tidal wave from spreading into the river.

    Keywords: The Arvand River, The Karun River, CTD, Tidal current, Sediment, Field data
  • Sirous Yasseri * Pages 31-43
    Subsea rigid steel spools (spool) are used to connect subsea equipment using diver-less connectors. Spools must meet functional requirements such as pressure, temperature, thermal expansion, environmental load, installation loads, lack of fit (misalignments), etc., yielding numerous loading conditions.  The installation accuracy that the installation contractor can achieve is another issue.  Thus, it is inevitable that numerous geometries to be investigated and perform several iterations in search of a suitable configuration.  The no-burst concept, in conjunction with a High Integrity Pressure Protection (HIPP) system, leads to heavier spool wall thickness, hence less structural flexibility which in turn increases reactions on the subsea connectors, which in turn is transferred to the adjoining equipment. Add to this complexity, the seismic qualification requirement if a jumper is in an earthquake-prone area.
    Keywords: Subsea Spools, Soil- spool interaction, ISO 19901, ISO 19902, Geohazard, ALE, ELE
  • Ehsan Sarhadizadeh *, Mehrnaz Farzingohar, Niusha Mostoli Pages 45-54
    In this study, the performance and efficiency of 12 ports in the Persian Gulf, Oman and Caspian seas in Iran is evaluated using data envelopment analysis (DEA) method. DEA allows comparing the efficiency in revenue generation of ports with different economies. Two different modeling approaches were presented in this study; based on relating earnings to port operational capability and activity, and based on land indicators, infrastructure, and equipment. The results of this study showed that most of the ports in the Persian Gulf region had a relative efficiency in the field of petroleum products. On the other hand, a significant difference was observed between the nominal capacity of acceptance of petroleum products of ports and the volume of oil product exchanges.
    Keywords: Data Envelopment Analysis, Port Efficiency, Output Oriented CCR model
  • Mehri Hashemi Devin, Abbas Ranjbar Saadat Abadi *, Ebrahim Fattahi, Sara Karami, Saviz Sehat Kashani Pages 55-66

    A strong low level jet (LLJ) in the northern region of the Persian Gulf (PG) observed on 5th Jun 2020 that sank the Behbahan cargo vessel. In this article, we have used the WRF-V3 model and reanalysis ERA5 data to study the vertical structure, diurnal variation and intensity of the LLJs. The aimed topography’s region, the pressure gradient and the land-sea breeze are the essential key factors in analyzing the diurnal variation of the LLJ over the PG that is known as the Shamal wind. The low terrain height in the northern of the PG and Zagros Mountains channelized the northwest winds and increased the pressure gradient that increased the wind speed. The decreasing friction over the PG during nighttime and the differences in temperature and specific heat capacity between water and land cause an increase in the LLJ intensity. The LLJ’s core 22-24 ms-1 was located over the study region in 925hPa on 4th and 5th June at 18 and 00 UTC respectively. Thereafter core’s wind speed decreased to 10-14 ms-1at 12UTC on 5th June. The mix-down of momentum from the LLJ level to the surface caused an increase in wind speed and wave height over the PG which sank the Behbahan cargo vessel at early morning of 5th June.  The LLJ at some regions like Kuwait formed at lower heights (under 950 hPa) and at the other points LLJ formed at levels upper than 950 hPa during nighttime of 4th Jun to afternoon of 5th Jun.

    Keywords: Low Level Jet, Persian Gulf, Speed, Behbahan cargo vessel, WRF-ARW model, wind vertical profile