152 لكش 4 - 12 يقرش ياه هفلؤم نيگنايم يعطقم ياه شرب : - بونج و يبرغ - دادتما رد تعرس ناديم لامش ريسم IJ .تسوگآ و سرام ياههام يارب ( لكش 4 - 13 رد تسوگآ و سرام ياه هام يارب ار يروش و[r]

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Abstract In the present paper **simulation** of tidal **currents** on **three**-**dimensional** geometry of the **Persian** **Gulf** is performed by the solution of the depth averaged hydrodynamics equations. The **numerical** solution was applied on two types of discritized **simulation** domain (**Persian** **Gulf**); with and without major islands. The hydrodynamic model utilized in this work is formed by equations of continuity and motion in two-**dimensional** horizontal plane. The effects evaporation and rainfall are considered in the source term of the continuity equation. The effects of bed slopes in x and y directions are considered in the partial differential terms representing the variation of hydrostatic pressure and the effects of bed friction, as well as the Coriolis effects are considered in algebraic terms of two equations of motion. The unstructured finite volume method is applied for solving the governing equations on overlapping control volumes formed by triangular cells. Using unstructured triangular meshes provides modeling of the geometrically complex flow domains, such as the **Persian** **Gulf** region. The results of the developed model for fluctuating flow on the variable bed elevation are compared with an available analytical solution of flow in a quadrant variable bed slope and Parshall flume. The accuracy of the finite volume flow solver is assessed by comparison between **numerical** results and the analytical solution and experimental measurements reported in the literature. The performance of the computer model to simulate tidal flow in the **Persian** **Gulf** domain is examined by imposing tidal fluctuations to the main flow boundary during a limited period of time and comparison of the computed results in an arbitrary location with available data from admiralty tide tables. Finally, a comparison was made between the model results of the two types of discritized **simulation** domain.

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Records of weather stations at Qeshm airport (N: 26º45’- E: 55º54’) and synoptic stations located south of Qeshm city (N: 26º57’– E: 56º16’) were used as meteorological data in the **simulation**. Since the direction of prevailing wind was north-south, perpendicular to the channel, the effect of wind on **currents** was considered not to be intensive. Climate of this region is usually warm and humid. In summer, heat reaches up to 45 ºC and in winter, temperature rarely falls below 12 ºC. The average number of rainy days per annum is about 12 days and the annual precipitation is less than 175 mm. Salinity of water in this region is influenced by **currents** from the **Persian** **Gulf** and the Sea of Oman (Johns, 1998). Local variation of salinity is poor due to narrow width and shallow depth of the channel. Average salinity is 38 PSU and seasonal fluctuation is about 4 PSU. Average seasonal water temperature fluctuates between 22 ºC in winter up to 32 ºC in summer with a diurnal fluctution of about 0.2 ºC to 1.2 ºC (Hajizade Zaker, 2005).

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that the standing wave and the travelling wave models correspond to two consecutive transitions of the Marangoni flow. In particular, for large Prandtl number liquids, the flow exhibits a first transition from the axi-symmetric steady to the **three**-**dimensional** oscillatory state, characterized by the standing wave instability and, after a certain time, a second transition from the standing wave to the travelling wave. These results, for a liquid bridge with a fixed aspect ratio (A=1), have been also validated by experimental results on ground (Monti, Savino, Lappa 21 ) where, for

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the chairmanship of Amir Faisal, and the others were chaired by Sir Rupert Hay, the British Political Resident in the G u lf. Much of the discussion was concentrated on the historical allegiance of various tribes which roamed the borderland between Abu Dhabi and Saudi Arabia. Collection of Zalcat (alms tax) was also frequently invoked as evidence by the rulers to support their respective claims to sovereignty. Thus, on 29th January, Sir Rupert Hay presented the boundary claimed by the Shaikh of Q a ta r. The line began at Ghar al-Buraid on DauhafSalwa, and then ran eastward through **three** points to Hamz Sauda N a th il, and from there through Aglat Manasir to a point on the west shore of Khor a l-U d a id . A section of land 25 miles wide a t the base of the Peninsula would be regained by Q atar if this frontier was accepted, as the Saudis had claimed it in 1949. Then Sir Rupert advanced the boundary claimed by the Shaikh of Abu Dhabi. This line started at Hamz Sauda N a th il, and ran in a straight line to the most southern part of Sabkhat M a tfi. From there if ran roughly south-east to al-Q u rain i then east-north-east to Umm a l- Zam ul.

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engineering ows. Since ow at the out ow boundaries depends on the unknown ow outside the computa- tional domain, an exact out ow boundary condition can not be implemented, but an approximation must be made. In the self similar region of plane wake ow, the application of periodic boundary conditions in the self similar coordinates is permitted. In more general cases, however, boundary conditions which are to be nonre ective in nature must be specied. In this work direct **numerical** **simulation** of **three** **dimensional** spatially{developing plane wake ow is performed to solve momentum and mass conservation equations.

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It appears that if a Detaining Power elects to try a prisoner of war pursuant to its national law, for a war crime committed prior to capture, it must do so "by the same co[r]

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highly regulated international trade and smaller, traditional forms of dhow-borne commerce may provide an opportunity for illicit entry into the global supply chain, however.
Iraq’s ports and maritime infrastructure are key sources of wealth and serve as vital connections to the global economy. Since 2003 both Iraqi and coalition leaders have realized that the restoration of Iraqi port facilities to their full capability (they have been the victims of neglect and targets of military attack since the Iran-Iraq War) is critical to Iraq’s reconstruction, and attempts have been made to bring them up to international standards. However, the opportunities for patronage, graft, and smuggling available to those who control them have made ports such as Umm Qasr and Abu Flus, as well as the offshore oil terminals, the objects of much inter-party competition (and violence). The manner in which Iraq’s ports become either a tool supporting national economic regeneration (by full incorporation into the global maritime economy) or simply fiefdoms for competing militias, can demonstrate whether international initiatives such as ISPS make the world’s ports safer, or actually create a two-tiered maritime economy by excluding states incapable of ISPS compliance. To date, despite not complying with ISPS, Iraqi ports have implemented a variety of improvements to port security, primarily as part of wider coalition reconstruction efforts. Despite the 2004 attack against an Iraqi oil platform in the northern **Persian** **Gulf**, pervasive violence in Iraq since the 2003 coalition invasion, and widespread militia infiltration of the ports and Iraqi security services tasked with protecting them, maritime trade in Iraq has been brisk, likely reflecting Iraq's opening to the world after being shut out of the global marketplace by war and sanctions for so long. Iraq's ports retain several vulnerabilities to terrorism, but the success of Iraqi ports in spite of widespread chaos seems to reflect that at least some shippers will sail into danger when potential profits outweigh the risks.

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Kuhlmann [5], Kuhlmann and Rath [6], Wanschura et al. [7] investigated the linear stability of steady axisymmetric thermocapillary flow in cylindrical liquid bridges. Their results predicted the critical Marangoni numbers and the form of the most typical disturbances, characterized by the appropriate value of the critical wave number, in the neighbourhood of the neutral stability point (i.e., close to the onset). Comparison of the theoretical results with the **numerical** available data have confirmed some features of the observed instabilities, e.g., for low Prandtl numbers the instability breaks the spatial axisymmetry (but the flow regime is still steady) prior to the onset of time dependent flow field, whereas for high Prandtl numbers the instability is oscillatory (Hopf bifurcation).

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of current are the semi-diurnal streams and the surge component, and these two are in roughly similar directions, an estimate of the extreme current has been obtained by adding the value[r]

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The Symbols p ; and v,· denote, respectively, the average size and average number of vertices of the grains adjoin- ing 29 grain / (which itself has size R-, and «,· vertices).. The ne[r]

In recent years, underwater acoustic (UWA) communications have received much attention as their applica- tions have begun to shift from military toward commercial. Digital communications through UWA channels differ substantially from those in other media, such as radio channels, due to severe signal degradations caused by multipath propagation and high temporal and spatial variability of the channel conditions. This paper describes a project designed, based on the results obtained from extensive laboratory and field experi- ments on sound speed profile in different depths of the **Persian** **Gulf**, to investigate and demonstrate an un- derwater acoustic communication system. Transmitted data are acoustic signals to which for more safety in transmission and low frequency bandwidth, Rivest cipher cryptography algorithm and linear prediction cod- ing are applied, respectively. In transmitter, Quadrature Phase Shift Keying (QPSK) signaling is employed to make efficient use of the available channel bandwidth. In the channel, a comprehensive model for short-range shallow water multipath acoustic channel is presented. The mathematical modeling of the multi- path effects is based on the ray tracing and the image method. Also, the attenuations due to wave scatterings at the surface and their bottom reflections are accounted for. In addition, we consider the loss due to the fre- quency absorption of different materials and the presence of ambient noises such as the sea state noise, ship- ping noise, thermal noise and turbulences. In the receiver, to overcome the difficulties of inter symbol inter- ference, adaptive equalization using Decision Feedback Equalizer (DFE) is applied.

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Discretization process has been achieved to discretize the geometrical model with unstructured tetrahedral elements and prism layers near the walls. In this study, 3D discretization has been utilized with the finite volume method (FVM) provided by the ANSYS CFX software. In order to accurately simulate the flow in a turbine passage, further mesh refinement around the vanes and runner blades’ edges is required, which is locally zoomed up in Fig. 7 (b). With mesh refinement an improvement of the results can be expected. In **numerical** simulations, a mesh dependence test is important in order to check the convergence of the computation. It must ensure that the residuals of the computed equations and the continuity error are small. The test is performed by refining the mesh to its final configuration shown in Fig. 7 (a) and that has been

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Likewise, **three**-**dimensional** experimental data is fairly limited but several re- searchers have reported observations of **three**-dimensionality in cavity flows. Ahuja & Mendoza (1995) conducted an extensive set of experiments on the effect of cav- ity dimensions, boundary layer, and temperature on cavity noise for subsonic flows with turbulent boundary layer upstream of the cavity. They determined that the parameter L/W , the cavity length to width ratio, provided a transition between two- and **three**-**dimensional** flow. For L/W < 1, the cavity is classified as two- **dimensional**, as the flow was found to be uniform over much of the span, with a coherent shear layer spanning most of the cavity width. The cavity is said to be **three**-**dimensional** for L/W > 1, as the flow cannot maintain a coherent shear layer across its width because of the end-effects that cause significant spillage of flow over the cavity side into the cavity. In that case, they reported **three**-dimensionality in the mean flow, and much lower (about 15 dB) acoustic loads than the pre- dominately two-**dimensional** flow. However, Ahuja and Mendoza’s classification of wide cavities as two-**dimensional** is based on a time-averaged view of the flow field, and the **three**-dimensionality is not related to the 3D instability we identify in our present work.

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It is therefore timely to apply a more complex analytical procedure, such as a 3-D Computational Fluid Dynamics (CFD) method to determine the effects of changes in the compressor geometry on internal heat and fluid flow. Such an approach can produce reliable predictions only if calculated over a substantial number of grid points. Hence, a high computer potential and capacity is needed in order to use such procedures to analyse a screw compressor. If an inadequate **numerical** grid is used, or the solver parameters are not selected carefully, a convergent **numerical** solution may not be obtained. Calculation results must therefore be monitored closely and compared with the experimental data in order to avoid obtaining results which do not accord with real flow conditions. Apart from the authors' publications [1]-[3] and [4], there is hardly any reported activity in the use of CFD for screw compressor studies. This is mainly because the existing grid generators and the majority of solvers are still too weak to cope with the problems associated with both the screw compressor geometry and physics of the compressor process. Since a screw compressor comprises both moving rotors and a stationary housing, any **numerical** grid applied must move, slide and deform. Moreover, if flow is to be calculated through the compressor clearances, the geometric length scale ratio of the working chamber may rise to 1000:1. Despite this, the grid aspect ratio should be kept very low. This cannot be done with the majority of existing CFD grid generators. Compressor flow, even in its simplest form, is further complicated by sharp pressure changes and high accelerations, which may drastically affect the flow structure. If, in addition, the working fluid is a real gas or a two-phase fluid or it contains particles, then there is hardly any CFD solver which can produce a straightforward solution. Therefore, special care is needed to blend the grid generation procedure with an adequate **numerical** solver to obtain a useful **numerical** solution of screw compressor processes.

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The thermal discharge studies are classified into **three** categories, namely theoretical analysis, computational analysis and experimental work. In this paper the experimental and theoretical analyses were undertaken to investigate the behaviour of the thermal discharge plume. Enormous literatures of thermal discharge studies are available; all aiming to minimize the impact of the thermal discharge by reducing its temperature before entering the receiving water. Abramovich (1963) mentioned that the first attempt of computing the jet trajectory in cross flow was made by Baturin and Shepelev in 1934. They obtained the velocity along the centreline of the jet geometrically using velocity vector for the ambient and the jet. The mathematical modelling of **three** **dimensional** heated surface jets by McGuirk and Rodi (1978) is a broad study carried out in the late seventies on discharge heated water into stagnant and deep water. The paper solved the five governing equations: continuity equation, two momentum equations in x, y directions, thermal energy equation and the equation of state. The authors made several assumptions to simplify the elliptic equations to parabolic form to

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________________________________________________________________________________________________________ Abstract - The ceramic heat exchanger is studied to find the performance of heat transfer and pressure drop by **numerical** computation. The **numerical** computation was performed throughout the domain including fluid region in exhaust gas side rectangular ducts, ceramic core and fluid region in air side rectangular duct with the air and exhaust in cross flow direction. The main aim is to reduce the hot side temperature from 1100 o c to 600 o c and later it passes through the metallic heat exchanger temperature ranges less than 600 o c. By increasing the Reynolds number on the cold air side this increase the velocity of the cold fluid Increase the heat transfer rate also increase the velocity by using nuzzling effect on cold air slot. The main purpose using the ceramic is to withstand with high temperature than metal.

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Abstract. Shanghai city has been suffering land subsidence caused by overly exploitation of ground water since 1921, which is a serious problem for this coastal city with altitude of 2.2–4.8 m above mean sea level. The largest cumulative land subsidence amounted to 2.6 m in the downtown area. Measures to decrease the ground water exploitation, change the pumping aquifers, and increase aquifer artificial recharge have been used to mitigate land subsidence since 1961. It is necessary to develop a proper **numerical** model to simulate and predict land subsidence. In this study, a decoupled **three**-**dimensional** (3-D) finite element land subsidence model including a 3-D ground water flow model and a 3-D geo-mechanical model was developed to simulate the 3-D deformation of the aquifer systems in the center area of Shanghai. The area of downtown Shanghai is 660 km 2 , with 10 million inhabitants, dense high buildings, and 11 metro lines. The **simulation** spans the period from 1979 to 1995. Two different assumptions have been tested on the side boundary, i.e., precluding the **three** components of the displacement, or assuming a free-displacement condition. The distribution of calculated land subsidence and horizontal displacements in different aquifers was analyzed. The computed vertical displacement fitted well with the available observations. It has been verified that the two different assumptions on the lateral boundaries in the geo-mechanical model caused different results just limited on nodes close to boundary. The developed 3-D land subsidence model is reasonable and can be used to simulate and predict 3-D movement of aquifer systems in the center area of Shanghai, which could provide scientific support to local government in controlling land subsidence and differential movements of the land surface.

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As one of the mesoscopic approaches, the discrete (dis- tinct) element method (DEM) was developed by Cundall and Strack (1979). The fundamental concept of this method is simple: An object is considered to consist of elements, a discrete unit of material, and the equation of motion for each element is solved. The DEM has been employed in the analyses of geological structures, the movement of soil, and others (Donz´e et al., 1994; Iwashita and Oda, 1998; Mora and Place, 1998; Place and Mora, 1999) to show good agree- ments with observations and experimental results. Most of those simulations are, however, required to introduce com- plex mathematics due to the nature of elements or mecha- nisms of phenomena (Iwashita and Oda, 1998; Mora and Place, 1998; Place and Mora, 1999), furthermore are done under two-**dimensional** condition.

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