HYDROPHYSICS
Year:2019 | Volume:5 | Issue:1 |Papers Count:12

Tidal asymmetry in the south-east of the Kish Island (Persian Gulf) is investigated in this study using water-level and velocity profile (3 layers) data recorded by an ADCP for a period of 35 days at a station with the depth of 12m. In the whole water column, the dominant current is forced by tide which periodically alters velocities in east (in high tide) and west (during low tide) directions. The weak residual current diverts current field as partially southward especially in two deep layers. Due to atmospheric forces, residual current partially disperse observed current from east-west direction in the upper layer. Tide is mixed mainly semidiurnal at the study area and principal triad tides K1-O1-M2 produce 13. 66-day periodic asymmetries including an ebb-dominance and a flood-dominance during spring and neap tides respectively. Although, the contribution of the ebb-dominance asymmetry induced by this triad is dominant in all 35 days. During the whole period, shallow water components induce a flood-dominance asymmetry condition.

With identification of monthly surface currents in an ocean area, one can detect accumulation of pollutants, sea fronts and ocean eddies. Surface currents are derived from two components; Ekman component (current due to wind) and geostrophic current (current due to change in sea surface height). Since measurement of oceanic currents is difficult and time consuming, OSCAR satellite data is used in this paper to look at the current vectors in the Indian Ocean using Arcmap software. After plotting the vectors of these streams, the path of each current flow and its characteristics are noted and the average surface waters of the North Indian Ocean are surveyed in different sections of the study. The results show six sustained and significant flow patterns in the north of the Indian Ocean along with their ivy. The strongest current in the north of the Indian Ocean, the Somali stream, and the eastern Arabic flow are weaker than all the streams of this region. The average flow velocity is 0/12 m/s. Typical velocity varies from 0. 001 m/s to 1. 37 m/s is this ocean. Currents with measo-scale eddies have also a typical velocity of 0. 7 m/s.

Increasing water and soil pollution causes a lot of environmental problems. Meanwhile, different methods of controlling and decontamination of pollution with modern technologies have arisen, and these methods generally bring a lot of costs in a way that is not economical at times. One of the methods used to treat water and soil pollution is the use of plants, which is called purification plant. Identification of active and important plants in this field improves the efficiency and protection of the environment. The purpose of this study is to cultivate two aquatic species (bamboo and straw) in a laboratory environment to determine their ability to remove nitrate, salt and chlorine from raw water. For this purpose, NaCl and potassium nitrate with different concentrations in raw water and the absorption of the elements by the leaves of bamboo leaves and straw and the remaining amount of elements in raw water were measured on days 1 and 14. The results show that most bamboo plants are able to remove elements in raw water. So that at the highest concentration, removal of nitrate, sodium, potassium and chlorine are 46. 28%, 32. 62%, 24. 73% and 27. 98%, respectively.

Wind-induced waves are the most complex waves among sea waves. In special circumstances such as extreme winds and storms however, it is essential to estimate and predict them correctly. In this research, the height and period of waves was investigated during winter Shamal wind using SPM method and a numerical simulation employing Coupled Ocean-Atmosphere-Wave Sediment Transport COAWST, in the northwest of the Persian Gulf in January 2015. The beginning of the winter Shamal wind coincides with the passage of a cold front over the Persian Gulf, when the wind speed increases and the direction of wind changes to north and northwest. According to the results simulated wave height and period from COAWST show better agreement with field data compared with those of SPM method. This conclusion is also verified with statistical methods such as RMSE. In both methods, the frequency spectrum of the region is single-peak. Besides, the peak of the spectrum of SPM and COAWST, shows under-prediction in comparison with the field data. According to the standard spectrums, the JONSWAP represents the closest wave spectrum of the area under investigation.

The main feature of the Arabian Sea is the monsoon reversing winds during the summer and winter monsoon. The seasonal variations of hydrophysical parameters of Arabian Sea surface are strongly influenced by seasonal monsoon winds. In this study, the distribution of sea surface temperature (SST), sea surface salinity (SSS) and the mixed layer depth (MLD in the region between 56E-73. 4E and 18N-25N are investigated using MITgcm model with a spatial resolution of 2 arc-minutes during Monsoon. Temperature, salinity, wind, net heat flux and evaporation minus precipitation rate are applied to the model as initial data. The model has been steady after 20 years. The results of modeling show that the average SST during the summer monsoon is 2. 1º C more than the winter monsoon. The model predicted the summer cooling of Arabian Sea well, so that in the southwestern region and during the winter monsoon SST is about 0. 5° C more than the summer monsoon. On the other hand, the difference SSS between two monsoons is about 0. 1PSU. The MLD is deeper during the winter monsoon than summer monsoon. The shallowest MLDs occur during the summer monsoon and on the southern coasts of Iran specially in the coast of Chabahar, while during the Winter Monsoon, The deepest MLDs are found in the western coast of India and also the shallowest in the coast of Oman.

The tide is an essential information in conducting studies on sedimentation, morphological changes and flooding of coasts, erosion as well as coastal strip management. Due to lack of measurement information in many coastal and marine areas, wave characteristics are estimated using different methods. Marine wave forecasting projects are often performed by numerical models or empirical methods. In the present study, the tidal flow velocity in Bushehr Bay is modeled using the numerical model TELEMAC-2D and the dominant flow direction in the area is analyzed. Model settings include irregular trigonometric grid in x and y with the ratio of one to three from the smallest 30m grid to the largest 810m grid, a time step of 30 seconds, the bed friction law using Stickler Theory 50 m1/2s-1 used. The model ran for one month on 2011/07/12 in the Bushehr Bay. After running the model, the current velocity data are compared with the corresponding measurement data and the TPXO Global Database, the results showed an increase of correlation from 41/86% to 91/41% indicating that the model is suitable for flow rate modeling in Bushehr Bay. At the end, the dominant flow in the northwest is presented.

Today, many schemes are being considered for using renewable sources of energy such as ocean wave energy. While the Caspian Sea, for example, has waves that do not hold much energy for extraction purposes, if waves energy of the sea could be augmented, a greater amount of energy could be possible. In our research, we model the natural phenomenon of rip currents to achieve this objective. We used MATLAB for simulations and MIKE for meshing and topography in modeling rip currents, while considering different variables including: significant wave height and period of incident waves, sea bottom slope, height of rip channel, and channel gap. From the data, we calculated the amount of extractable power. Our results show the rate of water flow in the channel at different depths at 36 different points. We used a program written in MATLAB to show the flow rate and power generated from the simulated channel. Our findings indicate that the optimum condition can be achieved when the significant wave height is 1. 5m, period is 5sec, sea bottom slope is 7. 5%, height of channel is 4. 95m, distance from channel to beach is 75m, and channel gap is 10m. When these conditions are applied to a width of 100m, 30kW power can be expected and in 23test cases, we found a reasonable outcome. The variables with the most important effects on changes in power extraction were wave height and channel height. Moreover, in the cases we investigated, power ranged from approximately zero to 29. 2Kw, and in four cases, it was greater than 17Kw.

The signs and symptoms of the water crisis in Iran appear to lead to the decline in groundwater levels, land subsidence, soil erosion, dust storms, and the drying of wetlands, rivers and lakes. In this situation, the accurate identification and conservation of water resources is essential to reduce the effects of water scarcity. This research was conducted to better identify the water areas and assess the accuracy of aqueous clearances from non-aquatic environments using spectral measurements of distance from the Lar dam in the southwest of Damavand Peak. Four NDVI, NDWI Gao, NDWI McFeeters and MNDWI spectral indices were used to identify the water mass and distinguish it from other natural and artificial effects on Landsat 8 and Sentinel2 images. The results show the highest overall accuracy is related to the MNDWI index and the lowest overall accuracy is related to the NDWI Gao index. The kappa coefficient also represents a better separation of water zones from land in the MNDWI index. It is suggested that similar investigations be carried out in different areas of the country simultaneously to identify the aquifers so that the spectral indexes can be studied and evaluated more appropriately due to changing environmental conditions.

By the continued trend of decreasing water level the only connecting way of the bay to the mother sea will be possible in the Chapaghli area in the future. Accordingly, finding a solution to link Gorgan Bay to the Caspian Sea through construction of a new channel can guarantee the survival of this ecosystem. This paper addresses water change status in the Gorgan Bay via new communication channels and dredging old channels under the scenarios of declining water levels. In this research, two modules from two dimensional Mike21 model including advection-dispersion and Hydrodynamic under water reducing level scenarios were coupled together. Galogah channel by having the exchange time of 106, 87, 70. 5 and 71. 5 days and Anzan channel by having the exchange time of 117, 108. 6, 64. 6 and 79. 5 days at levels 27, 27. 5, 28. 5 and 29. 5 meters respectively were the priority of research and implementation. The maximum length of the Galogah and Anzan channels in Gorgan Bay were calculated 2 and 2. 7 km, respectively. The Ismailsai, Ashurada, and Khozini channels had the highest water exchange time and also had the greatest need for dredging at any considered decreasing level. In view of connecting the Anzan Canal to the deepest part of the Gorgan Bay and preventing future destructive ecological succession, it is recommended that the Canal be considered as the connecting channel of the Gorgan Bay with the Caspian Sea by the research community and authorities.

In this research, the analytical solution to bi-dimensional Advection-Dispersion-Equation was obtained in the finite domain at the open channels using Generalized Integral Transform Technique (GITT). The upstream boundary condition was considered Dirichlet type with arbitrary and irregular time pattern of the entrance concentration. The downstream, right and left bank boundary condition was considered zero gradient. The initial condition function was assumed in the general form. The Evaluation of the derived solution was performed using two hypothetical examples and by comparing the results with the analytical solution resulting from the Green’ s Function Method (GFM). In this way, in the first example, the entrance concentration from the upstream boundary was assumed zero and the initial condition function was considered impulsive at the specific point at the domain. At the second example, the irregular time pattern function of the entrance concentration from the upstream boundary and impulsive initial condition function was considered simultaneously. The results of both examples were compared with the results of GFM and the concentration contours at different times were presented. The results show good agreement between the proposed solution and the GFM solution and report the performance of the proposed solutions is satisfactory and accurate. The proposed analytical solution has high flexibility in adopting the various functions as the initial and boundary conditions. So it is very applicable and useful for verification of the two-dimensional complex numerical models.

In this paper sound generation by laser pulse irradiated on a solid block is investigated. After an introduction to known mechanisms and main equation of laser acoustics, the laser pulse profile of NdYAG laser by straight radiation on a photo-resistor was recorded and the profile was substituted as an optoacoustic source in related equation of sound evolution. Finally the solution of numerically solved equation and measured generated sound were compared. Results show that there exists direct relationship between generated sound pulse width and laser pulse width. Furthermore there exists reverse relationship between generated sound pulse width and solid block thickness. In addition, results of simulation and experimental data measured by laser microphone with photo-resistor detector are compared by obtained sound spectrum from Spectrogram which confirm previous theoretical and experimental data. Finally general rule of the similarity of sound pulse profile and sound generator laser pulse profile are observed in this experiment.

The importance of identifying underwater acoustic channels and their effects on signals is increasing due to its widespread use in various fields such as environmental monitoring, explorations in oceans and military operations. In this paper, we simulate the multi-path effect in underwater environment based on near-real-world models and by analyzing the received signal equations in a multi-sensor array. The results are expressed in terms of probability density, kurtosis, skewness, cepstrum and reflection volume in the channel. Based on received signal modeling, the signal behavior in a linear array is investigated and analyzed in a few depths relative to a fixed source. Moreover, to investigate the multi-path phenomenon, actual measurements were made in the sea and measurement scenario, signal analysis, results of the impulse response and its statistical behavior are presented. The results of real data analysis show that the magnitude of the acoustic signal transmitted by sea has a Nakagami distribution.