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In present study numerical investigation of two kinds of fluids namely air and water flow on flat surface have been performed to investigate the boundary layer. Computational fluid dynamics has been used as a numerical technique to solve continuity equation and momentum equation. The air has been used in this study due to its wide importance in aerodynamics applications. In addition water has been used for comparison. A 1 m length flat surface has been used as a base for boundary layer fluid flow. The altitude of the computational domain which includes the free stream fluid flow was 0.1 m. The fluid velocity at the leading edge of the surface was 10 m/s for both air and water. Flow on smooth surface has been considered. Viscous fluid flow was used and hence no-slip condition has been adopted for both air and water. The Reynolds number (Re) was based upon the distance x from the leading edge as a characteristic length. The boundary layer thickness () has been calculated. In addition wall shear stress () has been studied for both air and water. Also some other parameters have been calculated such as displacement thickness (*), momentum thickness ( ) and the coefficient of drag (CD). The results showed that the Reynolds number of water is bigger than the Reynolds number of air based on the conditions of the current study. The boundary layer of air is laminar from leading edge until 0.8 m. Beyond 0.8 m up to the surface end, the boundary layer is in the transition region. Also the boundary layer of water transited to turbulent region at 0.2 m while the air boundary layer is still laminar. As expected, the momentum thickness () showed similar behavior as boundary layer thickness ().The displacement thickness of air is higher than the displacement thickness of water.The results also showed that the air drag coefficient has less value than water drag coefficient from approximately 0.2 m up to the downstream. The results showed that water flow affected the flat surface by bigger wall shear stress than air.

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The effect on aerodynamic drag of a truck by controlling the boundary layer separation using a rotating cylinder on leading edge of the truck-trailer is investigated numerically. The flow was assumed to be steady, incompressible, turbulent, and two-dimensional passing over the top surface of the truck. The boundary condition for all the boundaries of the truck was set as well as the cylinder was treated as a moving wall with a specific rotational velocity. The developed computational algorithm is tested for the flow over a flat plate (8m) long with various free stream inlet relative velocity (U∞) which are considered the same as truck velocity and has the values (40, 60, 90, and 120) km/h. The effect of cylinder diameter (10,20,30,and 40) , rotational speed (1000-5000 r.p.m) and free stream velocity on the aerodynamic drag and pressure distribution of the flow field were investigated. The governing equations which used are the continuity, momentum, and the (K-ε) turbulence model. These equations are approximated by using a finite volume method, with staggered grid and modified SIMPLE algorithm. A computer program in FORTRAN 90 is built to perform the numerical solution.The numerical results show that, the optimum cases for inlet free stream relative velocity (U∞) values( 40,60) km/h, a significant reduction of drag coefficient equal to 80% and 77% respectively was obtained by useing a speed of rotation and diameter size equal to 5000 r.p.m and 40 cm , for (U∞) value( 90 )km/h a reduction equal to76%, and for (U∞) equal to (120) km/h a reduction equal to 60% was obtained . These optimum results lade to reduce the effect of the aerodynamic drag on the vehicle by delaying the separation zone of boundary layer and enhancing the pressure gradient of the flow field. Comparison of the results with the available previous published experimental and fluent program results was investigated.

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Determining the aerodynamic characteristics of iced airfoil is an important step in aircraft design. The goal of this work is to study experimentally and numerically an iced airfoil to assess the aerodynamic penalties associated with presence of ice on the airfoil surface. Three iced shapes were tested on NACA 0012 straight wing at zero and non-zero angles of attack, at Reynolds No. equal to (3.36*105). The 2-D steady state continuity and momentum equations have been solved utilizing finite volume method to analyze the turbulent flow over a clean and iced airfoil. The results show that the ice shapes affected the aerodynamic characteristics due to the change in airfoil shape. The experimental results show that the horn iced airfoil consumes more power than the other shapes of ice, its value was (44.4W). The horn iced shape has the worst effect on the airfoil than the other shapes. The present results are compared with previously reported results; it is found there is a very good agreement between them. A comparison between the experimental and computational results of the presented work were pursing the same behavior.

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In this paper, the problem of developing turbulent flow in rectangular duct is investigated by obtaining numerical results of the velocity profiles in duct by using large eddy simulation model in two dimensions with different Reynolds numbers, filter equations and mesh sizes. Reynolds numbers range from (11,000) to (110,000) for velocities (1 m/sec) to (50 m/sec) with (56×56), (76×76) and (96×96) mesh sizes with different filter equations. The numerical results of the large eddy simulation model are compared with k-ε model and analytic velocity distribution and validated with experimental data of other researcher. The large eddy simulation model has a good agreement with experimental data for high Reynolds number with the first, second and third mesh sizes and the agreement increase near the wall of the duct. The percentage error for the large eddy simulation model with experimental data of the (56×56) mesh size is less than 18 % and for the (76×76) mesh size is also less than 17% and for the (96×96) mesh size is less than 16 %. The large eddy simulation model show high stability and do not need extra differential equation like the k-ε model and a great saving in time and computer memory was achieved.

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The aim of this study is to improve the operation and performance Water Treatment Plant by improving circular sedimentation tanks of Al-Gazaer Water Treatment Plants in Al-Dewanyia city in Iraq which have been identified as operating poorly. A developed model of the circular settling tanks for the Water Treatment Plant of Al-Gazaer was prepared using Computational Fluid Dynamics (CFD). A three dimensional, multi-phase simulations with solids transport and removal included is used, and reflected the state of the art in settling modeling. Computational Fluid Dynamics simulations are employed to assess the effect of adding a vertical baffle at the feed section of a full-scale sedimentation tank for the improvement of solids settling in potable water treatment. Special attention was paid to the inlet baffle in the model setup. Apparently, there is a good agreement between measured and predicted values. Results show, the overall solids removal efficiency increased when using the baffle from 50 to 90.5% leading to a reduction of the effluent solids concentration of approximately 86%.

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Chilled ceilings systems offer potential for overall capital savings. The main aim of the present research is to investigate the thermal performance of the indirect contact closed circuit cooling tower, ICCCCT used with chilled ceiling, to gain a deeper knowledge in this important field of engineering which has been traditionally used in various industrial & HVAC systems. To achieve this study, experimental work were implemented for the ICCCCT use with chilled ceiling. In this study the thermal performances of closed wet cooling tower use with chilled ceiling is experimentally and theoretically investigated. Different experimental tests were conducted by varying the controlling parameters to investigate their effects on the ICCCCT characteristics such as tower cooling capacity, chilled ceiling cooling capacity, tower saturation efficiency, mass transfer coefficient and heat transfer coefficient. The following controlling parameters are varied during experiments: spray water flow rate (90 to 150 kg/hr), ambient air wet bulb temperature (12 to 18 oC), and also changing chilled ceiling flow rate (2 to 6 l/min).

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Swimming performance underlies the biomechanical properties and functional morphology of fish fins. In this article, a pair of concave fin has been suggested, which is inspired from Labriform-mode Swimming fish. First, three concave fins with different sizes are proposed in order to choose the optimum size. All three fins have the same length but with different surface areas, such that each fin has an aspect ratio different from the others. Next, the complete design of the robot is suggested, the complete design of the body and pectoral fins were subjected to computational fluid dynamics (CFD) analysis to show the validity of the proposed model. Finally, the physical model is suggested and provided with 3D printer of Polylactic Acid (PLA) with a density of 1240 kg/ m3. The swimming robot fins have been examined by CFD analysis provided by Solidworks® to evaluate the highest thrust and lowest drag forces. The result showed that the optimum fin is the one with the lowest aspect ratio fin produces the highest drag, whereas the highest aspect ratio fin gives the lowest drag and thrust, therefore; a value of aspect ratio in between these two cases is chosen. While other types of examinations are based on motion analysis of the 3D design, the required motor torque is calculated in order to select a suitable servomotor for this purpose, which a HS-5086WP waterproof servomotor can achieve the calculated torque.

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The purpose of this study is determined values of Mach Number (Ma) for Subsonic flow around NACA4412 which is begun shock wave and known the location it. A 2-dimensional triangular C-type grid is used to match the reference measurements at an airfoil cross-section was taken from NACA 4412 from leading edge to trailing edge. The Mach numbers which used are (0.1 to 0.9) respectively and angles of attack (2.31° and 0.0°)for three cases inviscid and viscous flow with choose two cases (K epsilon RNG and Spalart-Allmaras turbulent models).
The numerical results show that the inviscid and two turbulence models well predict the shock wave location and size as well as flow properties along the airfoil surface. The Lift Force Coefficient (CL) decrease and the Drag Force Coefficient (CD) increase with using viscous term as well as pressure coefficient (CP) give fit location for the shock wave

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This study investigated numerically and experimentally fluid flow and heat transfer in the desktop PC. Three patterns of the positions of air inlet and outlet were tested to find the best one for cooling. The computer components in the present study are CPU, finned heat sink, power supply, motherboard, CD, HDD and fans. Three components which were generate heat are CPU, motherboard and power supply and there were two openings for air inlet and two for air outlet. The air inlet velocities were 1.2, 1.8, 2.4 m/s with constant CPU fan velocity. The studied parameters were the changed of inlet air velocity, powers of CPU, motherboard and PSU and the positions of inlet air. The numerical results obtained are found in a good agreement with the experimental results. The experimental results show that the maximum temperature was 81℃ at 16.5 W and 1.2 m/s. Numerical results showed that the CPU temperature reaches 89.6 ℃ at 18.5 W and 1.2 m/s. From the results, it was found that; the temperatures of the main components (PSU and motherboard) affected little by CPU power and vice versa, the finned heat sink has higher cooling efficiency and the pattern 1 was the best pattern for CPU cooling.

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