This paper presents the results of heat transfer measurement and analysis for two 5*5 cm porous channels. the channels were made of bronze beads with two different mean diameters, dp=0.72 and 1.59 mm. the local wall temperature distribution and heat transfer coefficients were measured for heat flux of 8000 and 16000 watt/m2 with coolant fluid velocity ranging from 0.16 to 5 m/s and inlet fluid pressure of 1~3 atm. the flow of fluid in porous channels is modeled with using Darcy-forcheheimer-brinkman model. By using FLUENT software, simulation is done that the geometry figure with gambit is generated.

This paper proposed a new methodology which was based on computational fluid dynamics for predicting the scouring process of underwater pipeline. By redeveloping a commercial CFD computer code, the governing equations for the flow model was solved by finite volume method and wall shear stress which acted as the key parameter to judge the incipient motion of sediment was firstly calculated. Then the morphological change of the sandy bed was simulated by dynamic mesh technology. Based on the comparisons between experimental results and numerical results, it was confirmed that present numerical modeling method can simulate the flow field and scouring process around underwater pipeline accurately. Besides, the influence of gap ratios on the scour behaviors was investigated by the present simulation.

Emitter is the key component in drip irrigation system. It is necessary to have a comprehensive understanding of the flow mechanisms within drip irrigation emitters to design emitters that have a high performance. The use of computational fluid dynamics (CFD) to research the flow characteristics is appropriate because the labyrinth flow path is narrow and its boundary is complex. In this study, the flow in labyrinth channels was simulated by using the method of computational fluid dynamics (CFD) to calculate the distributions of pressure and velocity of the flow, and to calculate the relationship between pressure and rate of discharge for three sample of one type emitter. The emitters were destroyed and sizes of those channels were calculated by photography with Scanning Electronic Microscope (SEM). To calculate the relationship between pressure and rate of discharge as well as simulation of flow in emitters' channels, laminar flow model and turbulence model were applied. Verification of the results obtained from the CFD simulation was conducted in laboratory, according to the ISO9261 standard.The results of simulation for the labyrinth channel well matched the measured data in laboratory Computational fluid dynamics provides a promising tool to help in the design of labyrinth channels used in drip emitters.

Introduction: Drip irrigation in which water is only available to the plant, is increasingly used in recent years. Since the flow behavior inside the emitter is difficult due to their complex structure and small size, in present study an attempt was made to assess the flow behavior of the emitters using mathematical and physical models. It needs to be mentioned that analysis of flow behavior of water in labyrinth channels is difficult because of micro-characteristics of the emitter. In this context Zhang et al. (2007) modeled the emitter’ s flow path using FLUENT software. In this investigation two physical models namely: laminar and turbulent were used to simulate the flow. Also numerical models that have been tested in experimental conditions, were used in the hydraulic analysis of Emitters. Next, FLUENT software was used to simulate the behavior of the flow inside the two long-path emitters for calculating the discharge-pressure relationship of the models and results were compared with results obtained from experimental results...

In this subsection, a simulation model of underground pipeline leaks was created. Modeling the flow fields of overhead pipelines and underground pipelines with different soil porosity was conducted. The influence of the underground environment and soil porosity on the pipeline leakage field was analyzed. The influence of changes in the underground environment and soil porosity on the loss of kinetic energy at gas leakage was defined. Thus, the law of change in the characteristics of the sound signal of a leak on the pipe wall was obtained. Based on the results of study, it was determined the area of damage to a gas pipeline which is depended on proportionality of the diameter of the gas jet. As the gas is released from a crack in the gas pipeline and with different porosity of the pipe material, the gas diffusion occurred. As a result, the explosion zone increased which ultimately the release of gases into the environment under the influence of pressure increased.

In this paper, the 3-D flow pattern around the pier with different sections is simulated using FLUENT software. The pier sections modeled in this study included circular, spindle, oval, rectangular, square, and combined (rectangle - circle) sections. The software solves the flow equations using finite volume and pattern of cell centralism. Prismatic networks were used for computational lattice field. These networks were produced using the pre-processor Gambit. The computational field was then analyzed using the FLUENT software. The Fluid Volume Method (VOF) is used to involve the free surface in three-dimensional modeling. Flow turbulence has been entered in the calculations using k-e model. In three-dimensional models, the effect of changes in water surface profiles and piers shape were investigated on decreasing shear stress and thus reducing scouring. The results indicated that spindle and elliptical cross sections have the largest effect in reducing shear stress and thus scouring around piers. The low velocity flow is formed around these piers and no large disturbance and no return flow, as important factors in scouring, are observed for spindle shaped piers.

Flow pattern around the bridge piers includes water surface profile, velocity profile, shear velocity, shear stress distribution, etc. In this research, the effects of the base shape along with scale effects on the flow pattern around the rectangular bridge piers were numerically calculated through "FLUENT software", using Horizontal Velocity Distribution (Vx) and Vertical Velocity Distribution (Vy) criteria. The results showed that in studying the horizontal component of velocity (Vx) for the rectangular bridge piers, the vortices activity radius was 8 times of the length of the pier, and the minimum channel width for vortices activity was 16 times of the length of the Bridge pier; also, the minimum channel length in front of the pier was 4 times of the length of the pier and behind which, it was 25 times more than the bridge pier. Finally, the minimum channel length for the vortexes activity was calculated to be 29 times more than the bridge pier length. Furthermore, for the vertical component of velocity, the flow pattern around the base of the bridge cannot be an appropriate parameter for checking the effects of the length and width of the channel.

In this paper, laser beam welding of a rectangular piece of steel was simulated using FLUENT software. Physical properties of analytical field was constant and its changes with temperature was ignored. In the present work, effect of tool speed and laser power on temperature distribution of workpiece surface and different deeps in the plane of symmetry and also maximum of temperature and depth of penetration were investigated. Using a macro code, geometry generation and meshing of the analytical field by helping required geometric parameters were provided for software. Moreover, laser radiation power was exerted by writing an UDF in the FLUENT software. In this case, it was assumed that the workpiece is stationary and gaussian thermal source model defined in UDF moves with the intended speed. Results show that at a constant power, maximum temperature of the workpiece decreases with increasing heat source speed, moreover, in this case, gradient of temperature in front of the workpiece and behind of it, increases and decreases respectively. It is found that the temperature in the depth of the workpiece increases with increasing the power.

Stilling basins are one of the most common structures for energy dissipation of flow with high velocity and among different sections and types of these basins, diverging basins have better performance and lower constructional costs. In this research, the feasibility of 3D numerical simulation of diverging hydraulic jump in rectangular basins was investigated using standard k- e and RNG k-e turbulence models using FLUENT software. The free surface was determined using the VOF method. The outputs of numerical model in comparison with the results of physical model of hydraulic jump in diverging rectangular basins with diverging angels of 50and 100showed that the standard k-e turbulence model evaluated the free surface of water, jump length and maximum velocity in defined sections better than RNG k-e turbulence model. this model show that the efficiency of diverging basins in decreasing length of jump is more better than the classic basins. So this model is recommended for simulating hydraulic jump in diverging sections. Results showed that the mean relative error of water surface obtained from numerical model and measured values is about 7 percent. Modeled Velocity profiles were in good agreement with measured data. Also the numerical model showed the vortices that were accrued because of diverging walls as well as experiment investigations. These vortices accrued near the right side of diverging wall in high Froude numbers and in lower values of Froude numbers, accrued in both two sides of walls. The intensity of vortices was increased by increasing the angle of diverging walls.

Water scarcity is today’s world biggest challenge which requires different countries to manage their water resources in the most efficient way. Sprinkler irrigation increases water consumption efficiency due to more uniform distribution of water across the field. Precision farming is based on the site-specific use of inputs according to soil characteristics and plant needs. One of the main inputs for agricultural production is water.Thus, efficient use of water resources based on variable rate irrigation is considered to be a basic approach of precision irrigation. The main purpose of this study was to simulate and fabricate a variable flow sprinkler, applicable in solid set sprinkler irrigation system. The preliminary drawing of the proposed sprinkler, which equipped with a flow and pressure control plunger, was simulated using FLUENT software. The actual sprinkler was then fabricated and evaluated in a field. The performance of the sprinkler was evaluated at three pressure levels, three plunger positions (at the points of the least and biggest sprinkler’s cross section for water passage) and three diameters of outlet nozzle opening. Results showed that the plunger had the capability of varying outlet flow and pressure in the sprinkler and trends in flow and pressure variation as affected by the plunger position was very complicated. The FLUENT model for conditions with fully open of the plunger and half opened was effectively efficient. However, as the plunger closed the water passage more than the half of cross section, the model did not show an acceptable efficiency.