Journal of the Persian Gulf (Marine Science)
Volume:8 Issue: 30, Winter 2017

In this study, an alternative approach for recording water level fluctuation in a two-dimensional wave flume based on using pressure transducers is investigated. Two sets of simultaneous measurements were carried out at the same place using a water level meter and a pressure sensor. Spectral analysis is applied to find conversion coefficient between these sets of data. The conversion coefficients attained by this method are found to be considerably different from those obtained from linear wave theory.  It is also concluded that the deployed sensors are accurate to record the oscillation amplitude of harmonics with maximum 2 Hz frequencies. These sensors can record the simulated natural young seas with periods greater than 3s in full scale, supposing a length scale of 25 would be applied. It is revealed that the maximum frequencies dependent to depth attenuation correction were greater than theoretical values. In the accomplished laboratory data acquisition, the resulted relative error was diminished from approximately from 20% to about 1.5% by using the proposed method.

The present study focused on generation of representative waves of tsunamis using GPU-based SPH numerical method. In this regard, solitary waves, as traditional representative of leading waves of tsunamis, were firstly generated in SPH model by a piston wave-maker moving based on an implicit equation solved by numerical code. Since it was proved that solitary waves are remarkably shorter and steeper than real-world tsunami waves, a new approach was also presented to reproduce the very long wave of a real tsunami. In this method, the tsunami time series was approximated by a theoretical relation based on the combination of several solitons. The relation was then used to solve the linearized trajectory equation of a wave-maker for generation of the intended time series of tsunami wave in the SPH model. The generation of solitary wave in SPH model was evaluated by comparing different simulated waves with analytical ones and it was seen that the solitary waves are successfully generated. In order to consider the accuracy of SPH formulation for simulation of the solitary wave evolution, an experimental case of breaking solitary wave propagation over a composite beach was also simulated. Although numerical results demonstrated a slight spurious wave-height decay, the SPH model satisfactorily reproduced the entire evolution phases of the solitary wave including wave propagation over a flat bottom, wave shoaling on a slope and wave breaking. For verification of the proposed approach in reproduction of real-world tsunami measurements, the time series of surface elevation record of the 2004 Indian Ocean tsunami was generated in SPH model. The results demonstrated that the tsunami record is successfully generated using the piston wave-maker. Thus, the presented approach can be regarded as a suitable method for representing the very long wave of the tsunami instead of the traditional options.

The effect of marine species attached on rock mass breakwaters was evaluated on the durability of breakwaters against erosion in the Gulf of Oman, Iran. A suit of erosion indicators in rock boulders (i.e., chemical dissolution, full deterioration, roundness, exfoliation, lamination, fracture) were assessed qualitatively and visually between those materials with biota and those with no biota. The results showed that rock boulders with no biota were largely eroded than those boulders with attached biota. A significant difference was detected in all erosion indicators between rocks with attached biota and those with no biota suggesting that rocks with biota were significantly more durable against erosion than those with no biota. The conclusion from this study suggests that marine organisms attached to the rock mass breakwaters play a key role in the durability of these structures even if they are morphologically less qualified for breakwater construction according to the international standards. The findings also suggest that Lumachel rock boulders followed by sandstone boulders in the second place are more durable and therefore are a better choice for the construction of stable jetties.

The Lake Uremia experiences high evaporation rate and low inflow recently due to local meteorological changes and the agricultural water use in its corresponding watershed. Since, late 2017, the salinity exceeded 550 g/l in most of the northern part of the Lake. In such a hypersaline condition, the estimated values from the oceanic equation of state are not accurate anymore. In this study, similar relations for the Aral Sea and the Dead Sea are studied first and then retuned based on new set of measurements provided by dedicated instruments for high salinity environment. The formulae were assessed based on measurements and it was shown that the new formula introduced in this study significantly outperforms the available equations of state for the contemporary condition of the Lake Uremia.

The environmental characteristics of seawater affect acoustic wave propagation. Physical phenomena such as wind, tides, internal waves, temperature, and salinity variations, temperature and hydrodynamic fronts, and sea currents affect some of the acoustic wave frequencies. In order to simulate sound speed, Mackenzie empirical equation is employed and added to the MITgcm model to calculate sound speed in the domain as a function of temperature, salinity and depth. The model domain is in the range of 7° N-19°N and 44°E-57.1°E. Initial data (temperature, salinity, wind, net heat flux, evaporation and precipitation) were introduced to the model and numerical model was performed for 20 years. Comparison of temperature and salinity results with the measured data shows good agreement. Seasonal profiles of temperature, salinity and speed of sound were also investigated. The results showed that variations in the speed of sound are subject to temperature variations. Moreover, three water masses i.e. surface water mass, middle water mass, and Red Sea water mass are observed in the Gulf of Aden. The saline water of the Red Sea is at a depth of 300 to 800 meters, leading to inversion in the temperature and salinity profiles, resulting in the inversion of the speed of sound profile. In the range of 11.9°N and 44° E to 50°E, the rate of variations in the speed of sound from the surface to the depth of 250 m follow the temperature variations. Also, at depths of 300 to 800 m, due to the presence of the Red Sea water mass, the rate of variations in the speed of sound is due to temperature and salinity. Likewise, in the range of 45.8°E and from 12.8°N to 11°N, from the depth of 300 meters to the seabed, temperature variations were uniform, therefore the speed of sound is a function of temperature variation and salinity. At 11.9 °N latitude, two sound channels and at 45.8°E longitude, one sound channel was observed in spring.

Tiger-toothed croaker (Otolithes ruber) is one of the most important species that currently catch in the Northwest of Persian Gulf. A Generalized Additive Model (GAM) was fitted to Tiger-toothed croaker, Otolithes ruber, CPUE data (kg  per hour) from gillnet based in Northwest of Persian Gulf, Iran, between 2013 and 2018, with the aim to observe their relationship with environmental, spatial and temporal information. GAM model accounted for 36.4% of the variance in nominal CPUE. Stepwise GAM revealed the relative importance of two variables by decreasing magnitude, namely kd490 and month. The maximum and least CPUE rate occurred in Feb 2013 (42.62 kg/h) in Boseif station and November and December 2013 (1.13 kg/h) in Darvish station. This study considered the possible relationship of spatial, temporal and some satellite derived environmental variables on Otolithes ruber CPUE to finally help implementing of ecosystem based fisheries management for stock recovery program and management of this species. Results of this research revealed that latitude and longitude and year sampling have the greatest impact on Otolithes ruber CPUE. Since, the early step in ecosystem management is the sufficient knowledge on ecosystem and distribution of target species in relationship to environmental variables, therefore this research could help to implementing of ecosystem based management in this region.