ALBERT

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: Many types of oceanic physical phenomena have a wide range in both space and time. In general, simplified models, such as shallow water model, are used to describe these oceanic motions. The shallow water equations are widely applied in various oceanic and atmospheric extents. By using the two-layer shallow water equations, the stratification effects can be considered too. In this research, the sixth-order combined compact method is investigated and numerically implemented as a high-order method to solve the two-layer shallow water equations. The second-order centered, fourth-order compact and sixth-order super compact finite difference methods are also used to spatial differencing of the equations. The first part of the present work is devoted to accuracy assessment of the sixth-order super compact finite difference method (SCFDM) and the sixth-order combined compact finite difference method (CCFDM) for spatial differencing of the linearized two-layer shallow water equations on the Arakawa's A-E and Randall's Z numerical grids. Two general discrete dispersion relations on different numerical grids, for inertia-gravity and Rossby waves, are derived. These general relations can be used for evaluation of the performance of any desired numerical scheme. For both inertia-gravity and Rossby waves, minimum error generally occurs on Z grid using either the sixth-order SCFDM or CCFDM methods. For the Randall's Z grid, the sixth-order CCFDM exhibits a substantial improvement , for the frequency of the barotropic and baroclinic modes of the linear inertia-gravity waves of the two layer shallow water model, over the sixth-order SCFDM. For the Rossby waves, the sixth-order SCFDM shows improvement, for the barotropic and baroclinic modes, over the sixth-order CCFDM method except on Arakawa's C grid.In the second part of the present work, the sixth-order CCFDM method is used to solve the one-layer and two-layer shallow water equations in their nonlinear form. In one-layer model with periodic boundaries, the performance of the methods for mass conservation is compared. The results show high accuracy of the sixth-order CCFDM method to simulate a complex flow field. Furthermore, to evaluate the performance of the method in a non-periodic domain the sixth-order CCFDM is applied to spatial differencing of vorticity-divergence-mass representation of one-layer shallow water equations to solve a wind-driven current problem with no-slip boundary conditions. The results show good agreement with published works. Finally, the performance of different schemes for spatial differencing of two-layer shallow water equations on Z grid with periodic boundaries is investigated. Results illustrate the high accuracy of combined compact method.

Description: PhD

Description: Advisors:Sarmad Ghader,Farhang Ahmadi Givi Counsellors:Abasali Aliakbari Bidokhti

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. Succeeded by the Journal of Diving History with issue no. 55 (2008).

Description: Official publication of the Historical Diving Society U.S.A. and affiliated societies. Formerly Historical Diver Magazine for issues no. 1-54 (1993-2008).

Description: In this research I focused on the propagation of acoustic rays in shallow water areas then I selected the Persian Gulf and described sound transmission in this region with emphasize on physical properties of water masses and of sediments. Finally I studied on the sound speed variations and sound attention with data collected from this area (NE of Farsi Island & 50 kilometers south of Delware). Sound speed deviation in western part of Strait of Hormuz in winter is between 20-30 m/s and it is between 5-20 m/s in the Oman Sea. Minimum sound speed deviation is at 23-24 degree north & 60-62 degree east. In spring, this deviation varies from 25-35 m/s, which is greater than in winter. In winter, at east of 56 degree east, greater speed are in shallow water coastal areas. In summer, sound speeds are greater than in spring and vary from 35 to 55 m/s at western part of Strait of Hormuz and 20 to 40 m/s in Oman Sea. Finally in autumn, sound speed deviation is 30-45 m/s west of 56 degree east and in Oman Sea is the same. The greatest attenuation rate caused by absorption in Bandar Dayer is between 17 to 27 meters depth, which is from water masses with different densities.

Description: PhD

Description: Advisors: Banazadeh, M.; Counsellors: Abedi, A.

Description: Observations of Caspian Sea during August - September 1995 are used to develop a three dimensional numerical for calculating temperature and current. This period was chosen because of extensive set of observational data including surface temperature observations. Data from the meteorological buoy network on Caspian Sea are combined with routine observation at first order synoptic station around the lake to obtain hourly values of wind stress and pressure fields. Initial temperature distribution as a function of depth and horizontal coordinates are derived from ship cruises. The model has variable grid resolution and horizontal smoothing which filters out small scale vertical motion. The hydrodynamic model of Caspian Sea has 6 vertical levels and a uniform horizontal grid size of 50 km The model is driven with surface fluxes of heat and momentum derived from observed meteorological. The model was able to reproduce all of the basic feature of the thermal structure in Caspian sea and: larger scale circulation patterns tend to be cyclone, with cyclone circulation with each sub basin. Result has agreement with observations.

Description: PhD

Description: Advisors: Bannazadeh, M.R.; Bidokhti, A.A.; Counsellors: Kherandish, M.

Description: Persian Gulf region is globally of great importance due to its economical and political reasons. The importance lies in oil sources and sea exports. Geophysical phenomena dominated in the water circulation affected this region is called Monsoon it stretches from African coasts to the half way of Red Seal affected all coasts of Persian Gulf and goes toward east to the Indian ocean. Other essential factors in the water circulation in this region are net evaporation (several meters in per year), high density and high salinity. In this article the effects of wind stress and evaporation in the water circulation in the region will be considered and model equations for wind forces, density, pressure, gradient, and bottom friction for Persian Gulf will be discussed.

Description: PhD

Description: Advisors: Banazadeh, M.R.; Counsellors: Dolatshahi

Description: Generally the flow properties of rivers, estuaries and coastal seas are highly dependent on the bed morphology. These include mainly three flow parameters, as bed shear stress, velocity profile and turbulent fluctuations. Here we investigate the effects of permeate of the bed on these flow properties We consider the effects of suction (W0) injection (W0) on these flow properties particularly the bottom stress. Four types of bottom permeability with different size of sand have been tested. The results indicate a substantial reduction and enhancement of the bed stress under respectively injection and suction as has been observed by others on wave motion in shallow seas. We consider 5 waves to shore with this rang of wave steepness ( 0/015 〈 so 〈 0/05 ) . Cr Calculated used of mansard method (1980). We search the stream line of current in bed with a video camera and looking this. Near the surface and the deep of bed and consider V=W (in or su)/ U(ru or rd) and bottom stress for 6 period of this study with Canly and Inman studies (1994). All these results are shown by curves with the effects of permeable bed.

Description: PhD

Description: Advisors: Bedakhti, Ali Akbar, Pouranaraki, Hamid; Counsellors: Alramezan, B.

Description: The effect of swell on wind wave growth has been a topic of active research for many years with inconsistent results. The details are often contradictory among investigations. Further more, there remain a variety of competing theories to explain these phenomena. In this research, we consider waves and wind and temperature data in the Persian Gulf (Busher region) in years 1995, 1996 and 1999. This study provides estimations of wave conditions and the atmosphere stability that has an influence on wind wave. Results are also compared with data that have been recorded by a buoy in Caspian Sea (Neka region) during 1989. In the second part of this work we estimate non- dimensional energy and non-dimensional peak frequencies as a function of the non- dimensional fetch and Bulk Richardson numbers for the Persian Gulf (Busher region).This results also agree well with similar results for the Caspian Sea. The acquired relations can be used to compute the wind wave parameters. Also the results for the Persian Gulf show that the relationship of non-dimensional energy to as a function of wave age is independent of presence of swell. Finally the WAM model was run for the Persian Gulf during 3-8 September of 2002. The results show that swell on the Persian Gulf reduces the energy density of wind waves by up to 10%, but the growth rate at peak frequency is only reduced by up to 4%, and the spectral peak frequency is increased by only 1%.

Description: PhD

Description: Advisors:Shafifar, M., Bidokhti, A.A.

Description: The hydro dynamical actions in big Lakes directly influence dynamic, physical and chemical affairs. The circulation's models and temperature have something to do with the movements of fluids, and analysis for circulation in Caspian sea is because of the lack of observation through which the circulations and out comings are determined. Through the studies, three dimensional simulations (Large- Scale) are planned and performed, according to Smolakiewicz and Margolin works. This is a non- hydrostatic and Boussinesq approximation is used in its formulation is used in its formulation on the basis of Lipps (1990) theorem and curve lines, the fluid is constant adiabatic and stratified, and the wind power is considered zero. The profile of speed according to previous depth and before ridge can be drawn on the basis of density available between northern and southern ridges. The circulation field is drawn from 3 cm/s to 13 cm/s on the plate z= 5 cm , the vertical changes of speed on the plate is 0.02 m/s. Vertical profile , horizontal speed in previous on, and after the ridges on are drawn on different spaces. It changes from 0.5 cm/s to 1 cm/s before ridges.

Description: PhD

Description: Advisors: Bannazadeh, M.R.; counsellors: Bidokhti, A.A.

Description: In this thesis, wind wave prediction and analysis in the Southern Caspian Sea are surveyed. Because of very much importance and application of this matter in reducing vital and financial damages or marine activities, such as monitoring marine pollution, designing marine structure, shipping, fishing, offshore industry, tourism and etc, gave attention by some marine activities. In this study are used the Caspian Sea topography data that are extracted from the Caspian Sea Hydrography map of Iran Armed Forces Geographical Organization and the I 0 meter wind field data that are extracted from the transmitted GTS synoptic data of regional centers to Forecasting Center of Iran Meteorological Organization for wave prediction and is used the 20012 wave are recorded by the oil company's buoy that was located at distance 28 Kilometers from Neka shore for wave analysis. The results of this research are as follows: - Because of disagreement between the prediction results of SMB method in the Caspian sea and wave data of the Anzali and Neka buoys. The SMB method isn't able to Predict wave characteristics in the Southern Caspian Sea. - Because of good relativity agreement between the WAM model output in the Caspian Sea and wave data of the Anzali buoy. The WAM model is able to predict wave characteristics in the southern Caspian Sea with high relativity accuracy. The extreme wave height distribution function for fitting to the Southern Caspian Sea wave data is obtained by determining free parameters of Poisson-Gumbel function through moment method. These parameters are as below: A=2.41, B=0.33. The maximum relative error between the estimated 4-year return value of the Southern Caspian Sea significant wave height by above function with the wave data of Neka buoy is about %35. The 100-year return value of the Southern Caspian Sea significant height wave is about 4.97 meter. The maximum relative error between the estimated 4-year return value of the Southern Caspian Sea significant wave height by statistical model of peak over threshold with the wave data of Neka buoy is about %2.28. The parametric relation for fitting to the Southern Caspian Sea frequency spectra is obtained by determining free parameters of the Strekalov, Massel and Krylov etal_ multipeak spectra through mathematical method. These parameters are as below: A = 2.9 B=26.26, C=0.0016 m=0.19 and n=3.69. The maximum relative error between calculated free parameters of the Southern Caspian Sea multipeak spectrum with the proposed free parameters of double-peaked spectrum by Massel and Strekalov on the experimental data from the Caspian Sea is about 36.1 % in spectrum energetic part and is about 74M% in spectrum high frequency part. The peak over threshold waverose of the Southern Caspian Sea shows that maximum occurrence probability of wave height is relevant to waves with 2-2.5 meters wave fhe error sources in the statistical analysis are mainly due to: l) the missing wave data in 2 years duration through battery discharge of Neka buoy. 2) the deportation %15 of significant height annual mean in single year than long period average value that is caused by lack of adequate measurement on oceanic waves, and the error sources in the spectral analysis are mainly due to above- mentioned items and low accurate of the proposed free parameters of double-peaked spectrum on the experimental data from the Caspian Sea.

Description: PhD

Description: Advisors: Chegini, V., Banazadeh, M.; Counselors: Dolatshahi pirouz, M.

Description: Determining of beach states and study of manner sediment transmission in beach profile, involves the evaluating the actions of hydrodynamic forces dominated over the beaches, in this research through determining the beach states by the help of Hanson and short method, different reactions of Mazandaran’s shoreline against wind waves was studied and investigated. For this reason, First, the kind of hydrodynamic forces dominated over the beaches of this province was studied and beaches of the this province was distinguished as wave–dominated beaches, afterwards eight stations are chosen throughout the shoreline and the waves qualities and the sediments regarding to different depth was evaluated in these stations by using software and laboratory actions. In this way the parameter of dimensionless fall velocity each station was calculated and the beach states and their changes according to time was studied. Finally, the gained information is located in the software area of Arc GIS, and the waves dynamics and the way of erosion and accretion was evaluated in each station. In this research by study of air photographs during a thirty years period we found that was no remarkable changes at shoreline in western and central parts and each type of change depends upon the delta, while eastern part of coast at the location of breakwaters in neighbouring of Farahabad Station, accretion features is quiet evident. In the main results of this research, it became obvious that the beach state in the stations Neca, Farahabad, Larim, Naftchal, Mazandaran university, Babolsar, Noor is dissipative and the beach in Nashtarood station is in intermediate (ridge and runnel) state to the extend that in the dissipation beaches from east to west, the degree of dissipation of the beaches is decreased continuously.

Description: PhD

Description: Advisors: Chegini, Vahid; Counsellors: Torabiazad, Masoud

Description: This thesis considers a three- dimensional numerical model based on 3-D Navier— Stokes and continuity equations involving various wind speeds (North west), water surface levels, horizontal shier stresses, eddy viscosity, densities of oil and gas condensate- water mixture flows. The model is used to simulate the prediction of the surface movement of oil and gas condensate slicks from spill accident in the north coasts of Persian Gulf.

Description: PhD

Description: Advisor:M., Torabi Azad; Counsellors: A.A., Bidokhti

Description: The Persian Gulf (PG) is a semi-enclosed shallow sea which is connected to open ocean through the Strait of Hormuz. Thermocline as a suddenly decrease of temperature in subsurface layer in water column leading to stratification happens in the PG seasonally. The forcing comprise tide, river inflow, solar radiation, evaporation, northwesterly wind and water exchange with the Oman Sea that influence on this process. In this research, analysis of the field data and a numerical (Princeton Ocean Model, POM) study on the summer thermocline development in the PG are presented. The Mt. Mitchell cruise 1992 salinity and temperature observations show that the thermocline is effectively removed due to strong wind mixing and lower solar radiation in winter but is gradually formed and developed during spring and summer; in fact as a result of an increase in vertical convection through the water in winter, vertical gradient of temperature is decreased and thermocline is effectively removed. Thermocline development that evolves from east to west is studied using numerical simulation and some existing observations. Results show that as the northwesterly wind in winter, at summer transition period, weakens the fresher inflow from Oman Sea, solar radiation increases in this time interval; such these factors have been caused the thermocline to be formed and developed from winter to summer even over the northwestern part of the PG. The model results show that for the more realistic monthly averaged wind experiments the thermocline develops as is indicated by summer observations. The formation of thermocline also seems to decrease the dissolved oxygen in water column due to lack of mixing as a result of induced stratification. Over most of PG the temperature difference between surface and subsurface increases exponentially from March until May. Similar variations for salinity differences are also predicted, although with smaller values than observed. Indeed thermocline development happens more rapidly in the Persian Gulf from spring to summer. Vertical difference of temperature increases to 9 centigrade degrees in some parts of the case study zone from surface to bottom in summer. Correlation coefficients of temperature and salinity between the model results and measurements have been obtained 0.85 and 0.8 respectively. The rate of thermcline development was found to be between 0.1 to 0.2 meter per day in the Persian Gulf during the 6 months from winter to early summer. Also it is resulted from the used model that turbulence kinetic energy increases in the northwestern part of the PG from winter to early summer that could be due to increase in internal waves activities and stability intensified through water column during this time.

Description: PhD

Description: Advisors: Abbasali, Akbari Bidokhti; Hooshang, Bassirparsa; counsellors: Farhang, Ahmadi Givi; Ali, Karami Khaniki

Description: Observational data and a three dimensional numerical model (POM) are used to investigate the Persian Gulf outflow structure and its spreading pathway into the Oman Sea. The model is based on orthogonal curvilinear coordinate system in horizontal and train following coordinate (sigma coordinate) system in vertical. In the simulation, the horizontal diffusivity coefficients are calculated form Smogorinsky diffusivity formula and the eddy vertical diffusivities are obtained from a second turbulence closure model (namely Mellor-Yamada level 2.5 model of turbulence). The modeling area includes the east of the Persian Gulf, the Oman Sea and a part of the north-east of the Indian Ocean. In the model, the horizontal grid spacing was assumed to be about 3.5 km and the number of vertical levels was set to 32. The simulations show that the mean salinity of the PG outflow does not change substantially during the year and is about 39 psu, while its temperature exhibits seasonal variations. These lead to variations in outflow density in a way that is has its maximum density in late winter (March) and its minimum in mid-summer (August). At the entrance to the Oman Sea, the PG outflow turns to the right due to Coriolis Effect and falls down on the continental slope until it gains its equilibrium depth. The highest density of the outflow during March causes it to sink more into the deeper depths in contrast to that of August which the density is the lowest one. Hence, the neutral buoyancy depths of the outflow are about 500 m and 250 m for March and August respectively. Then, the outflow spreads in its equilibrium depths in the Oman Sea in vicinity of western and southern boundaries until it approach the Ras al Hamra Cape where the water depth suddenly begins to increase. Therefore, during March, the outflow that is deeper and wider relative to August, is more affected by the steep slope topography and as a result of vortex stretching mechanism and conservation of potential vorticity it separates from the lateral boundaries and finally forms an anti-cyclonic eddy in the Oman Sea. But during August the outflow moves as before in vicinity of lateral boundaries. In addition, the interaction of the PG outflow with tide in the Strait of Hormuz leads to intermittency in outflow movement into the Oman Sea and it could be the major reason for generations of Peddy (Peddies) in the Oman Sea.

Description: PhD

Description: Advisors: A.و Bidokhti; A., Javid; Counsellors: A., Karami khaniki; V., Chegini

Description: During the transformation of the low tide to the high tide, an exactly inverse phenomenon is occurred and the high tidal delta is formed at the mouth upstream. Increasing the tidal range does not affect the nature of this phenomenon and just change its intensity. In this situation, the inlet will be balance over time. A new relationship between equilibrium cross section and tidal prism for different tidal levels as well as sediment grading has been provided which its results are corresponded with results of numerical modeling. In the combination state, the wave height significantly affects the current and sedimentary pattern such that the wave height dimensionless index (Hw/Ht) determines the dominant parameter (the short period wave or tide) in the inlet. It is notable that in this state, the inlet will be balanced over the time. In order to calculate sedimentary phenomena, each of which are individually determined under solely wave and only tide conditions and then they are added. Estimated values are similar to numerical modeling results of the combination state considering nonlinear terms. Also, it is clear that the wave and tide performance is of meaning in the direct relationship with the water level. The water level change causes variations of the position of the breaking line and sedimentary active area. It changes the current and sedimentary pattern coastward while does not change anything seaward. Based on modeling results of sediment transport due to the wave, tide and their combination, it could be said that the erosion at the mouth due to the wave is less than that due to the wave and tide combination. In these situations, tide and wave-tide combination increase the low tidal and high tidal delta volume, respectively. Hence, tide plays an effective role in changing sedimentary phenomena at the channel and mouth downstream. Whereas, short period and combined waves have a crucial role in varying the morphology and sediment transport coast ward.

Description: PhD

Description: Advisors: A., Karami Khaniki; Aliakbari, Bidokhti; counsellors: S., Ghader

Description: In this study, numerical simulation of the Caspian Sea circulation was performed using COHERENS three-dimensional numerical model and field data. The COHERENS three-dimensional model and FVCOM were performed under the effect of the wind driven force, and then the simulation results obtained were compared. Simulation modeling was performed at the Caspian Sea. Its horizontal grid size is approximately equal to 5 Km and 30 sigma levels were considered. The numerical simulation results indicate that the winds' driven-forces and temperature gradient are the most important driving force factors of the Caspian circulation pattern. One of the effects of wind-driven currents was the upwelling phenomenon that was formed in the eastern shores of the Caspian Sea in the summer. The simulation results also indicate that this phenomenon occurred at a depth less than 40 meters, and the vertical velocity in July and August was 10 meters and 7 meters respectively. During the upwelling phenomenon period the temperatures on the east coast compared to the west coast were about 5°C lower. In autumn and winter, the warm waters moved from the south east coast to the north and the cold waters moved from the west coast of the central Caspian toward the south. In the subsurface and deep layers, these movements were much more structured and caused strengthening of the anti-clockwise circulation in the area, especially in the central area of Caspian. The obtained results of the two models COHERENS and FVCOM performed under wind driven-force show a high coordination of the two models, and so the wind current circulation pattern for both models is almost identical.

Description: PhD

Description: Advisors: V., Chegini; A.A., Bidokhti; counsellors: F., Ahmadi-Givi

Description: The purpose of this research is to study sedimentation mechanism by mathematical modeling in access channels which are affected by tidal currents. The most important factor for recognizing sedimentation process in every water environment is the flow pattern of that environment. It is noteworthy that the flow pattern is affected by the geometry and the shape of the environment as well as the type of existing affects in area. The area under the study in this thesis is located in Bushehr Gulf and the access channels (inner and outer). The study utilizes the hydrodynamic modeling with unstructured triangular and non-overlapping grids, using the finite volume, From method analysis in two scale sizes: large scale (200 m to 7.5km) and small scale (50m to 7.5km) in two different time durations of 15 days and 3.5 days to obtain the flow patterns. The 2D governing equations used in the model are the Depth-Averaged Shallow Water Equations. Turbulence Modeling is required to calculate the Eddy Viscosity Coefficient using the Smagorinsky Model with coefficient of 0.3. In addition to the flow modeling in two different scales and the use of the data of 3.5 day tidal current modeling have been considered to study the effects of the sediments equilibrium in the area and the channels. This model is capable of covering the area which is being settled and eroded and to identify the effects of tidal current of these processes. The required data of the above mentioned models such as current and sediments data have been obtained by the measurements in Bushehr Gulf and the access channels which was one of the PSO's (Port and Shipping Organization) project-titled, "The Sedimentation Modeling in Bushehr Port" in 1379. Hydrographic data have been obtained from Admiralty maps (2003) and Cartography Organization (1378, 1379). The results of the modeling includes: cross shore currents in northern and north western coasts of Bushehr Gulf during the neap tide and also the same current in northern and north eastern coasts of the Gulf during the spring tide. These currents wash and carry fine particles (silt, clay, and mud) from the coastal bed of which are generally made of mud and clay with some silts. In this regard, the role of sediments in the islands of this area and the islands made of depot of dredged sediments should not be ignored. The result of using 3.5 day modeling is that the cross channels currents leads to settlement places in inner and outer channels in tidal period. In neap tide the current enters the channel from upside bend of the two channels and outer channel. Then it crosses the channel oblique in some places of the outer channel. Also the oblique currents or even almost perpendicular current from up slope of inner channel between No. 15 and No. 18 buoys interact between the parallel currents in the channel and made secondary oblique currents which exit as a down-slope current in the channel and causes deposit of sediments as well as settling the suspended sediments carried by these currents. In addition in outer channel the speed of parallel currents in the bend of the channel which is naturally deeper increases. Therefore, it leads to erosion and suspension of sediments in this area. The speed of suspended sediments carried by this current which is parallel to the channel axis decreases when they pass through the shallower part of the channel where it is in the buoys No.7 and 8 to 5 and 6 are located. Therefore, the suspended sediment settles and because of this process these places will be even shallower. Furthermore, the passing of oblique upstream leads to settlement of the sediments in the up-slope and has an additional effect on the process of decreasing the depth of these locations. On the contrary, in the down-slope channel, as the results of sediments and current modeling indicates the speed of current increases and the currents make the particles of down-slope channel suspended and be carried away. Thus, in a vast area of downstream of both channels, the sediments have settled. At the end of the neap tide, the process along with circulations in this area produces eddies which causes sedimentation in the area. During spring some parts of this active location for sedimentation will enter both channels in a reverse process. The above mentioned processes and the places of sedimentation and erosion in inner and outer channels are validated by the sediments equilibrium modeling. This model will be able to estimate the suspended, bed load and the boundary layer thickness in each point of both channels and in the modeled area.

Description: PhD

Description: Advisors: A.A., Bidokhti; counsellors: M.M., Namin; M., Torabi

Description: The catastrophic event of red tide has happened in the Strait of Hormuz, the Persian Gulf and Gulf of Oman from late summer 2008 to spring 2009. With its devastating effects, the phenomenon shocked all the countries located in the margin of the Persian Gulf and the Gulf of Oman and caused considerable losses to fishery industries, tourism, and tourist and trade economy of the region. In the maritime cruise carried out by the Persian Gulf and Gulf of Oman Ecological Research Institute, field data, including temperature, salinity, chlorophyll-a, dissolved oxygen and algal density were obtained for this research. Satellite information was received from MODIS and MERIS and SeaWiFS sensors. Temperature and surface chlorophyll images were obtained and compared with the field data and data of PROBE model. The results obtained from the present research indicated that with the occurrence of harmful algal blooms (HAB), the Chlorophyll-a and the dissolved oxygen contents increased in the surface water. Maximum algal density was seen in the northern coasts of the Strait of Hormuz. Less concentration of algal density was detected in deep and surface offshore water. Our results show that the occurred algal bloom was the result of seawater temperature drop, water circulation and the adverse environmental pollutions caused by industrial and urban sewages entering the coastal waters in this region of the Persian Gulf ,This red tide phenomenon was started in the Strait of Hormuz and eventually covered about 140,000 km2 of the Persian Gulf and total area of Strait of Hormuz and it survived for 10 months which is a record amongst the occurred algal blooms across the world. Temperature and chlorophyll satellite images were proportionate to the measured values obtained by the field method. This indicates that satellite measurements have acceptable precisions and they can be used in sea monitoring and modeling.

Description: PhD

Description: Advisors: A.A.,Bidokhti; M.S.,Mortazavi; Counsellors: A.,Gheibi

Description: In this thesis, producing ability of electricity by horizontal tidal current turbines and installing possibility of these turbines on bridge's piers in the marine environments has been studied to reduce primary implementation costs and make the plan, economical. To do this and to study its feasibility, the exerted forces from installing horizontal tidal current turbines were compared with the forces applied to the bridge structure during designing process (given in the Standards). Then, the allowable ranges of the overloading which is tolerable by the piers of the bridge were obtained. Accordingly, it is resulted that for installing these turbines, the piers of the existing bridges are required to be strengthened. Because of increasing usage of renewable powers and as a suggestion, the exerted forces from installing turbine for loading coefficients of different Standards are given. Finally as an example, preliminary designing of a horizontal tidal current turbine was carried out for Gesham Channel and the forces exerted from turbine to the bridge's pier were calculated for the future usage in order to create a test site of real dimensions.

Description: Masters

Description: Advisers: M., Ghodsi Hasanabad; Counsellors: M., Ezam