University of Thi-Qar Journal for Engineering Sciences

The laminar flow through an obstacled sudden expansion channel is numerically investigated.Rectangular adiabatic inclined obstacles mounted behind the expansion region on the upper and lower wall of the channel were used. The effects of obstacles inclination angle, obstacles length, obstacles thickness and the number of obstacles on the flow and thermal fields for different Reynolds number and expansion ratio were examined. The angle of obstacles inclination was taken in the direction of stream wise flow and ranged from 30° to 90°. Three values of expansion ratio(ER=H/h) equal to 1.5, 1.75 and 2 were used. The choice of values of Reynolds number takes the consideration of symmetry state. The body fitted coordinates system is used to transfer the considered physical problem to computational domain in order to treat the complexity arising from applicable the boundary conditions near the inclined obstacles. The governing stream-vorticity equations expressed in generalized coordinates system were transformed to algebraic equations by using finite difference method. The solution of these equations was done by iteration method. The obtained results showed that there is a significant effect of obstacles angle on the hydrodynamic characteristics. The performed tests of the present results with related published results showed that there is an acceptable agreement.

Power generation by using concentrated solar thermal energy on liquid enclosures is one of the most promising renewable energy technologies. In this work, a developed liquid enclosure fitted with various number and configurations of horizontal metal rings have been analyzed, fabricated and tested. The influence of adding metal rings arrangement is investigated for its potential to enhance radial heat conduction to the center-line of the enclosure from the side-walls. Experiments were carried out for fluid in both static and dynamic modes of operation inside the enclosure that subjected to high heat flux.A developed two-dimensional CFD model to predict the transient flow and thermal fields within liquid enclosure subjected to heat flux has been developed and tested. The developed numerical model takes into consideration energy transport between the liquid inside enclosure and the solid material of the enclosure. The numerical simulations have been compared with experimental measurement. The computational code has been found in a good level of agreement with the experimental data except for liquid at the peak part of the enclosure. The results indicate that adding metal rings produce significant impact on the transient temperature difference inside enclosure during both static and dynamic modes. The six-ring model is found to be more effective for enhancing radial heat transfer than other three models that have been tested. The in-line arrangement is found to provide better thermal effect as compared to the staggered rings.Two new correlations for natural heat transfer inside liquid enclosures subjected to high heat flux have been formulated (one for no-ring model and the other for six-ring model). The natural Nusselt number is found to be around a constant value for Rayleigh number less than (5 x 108). The recommended use of metal rings inside liquid enclosures subjected to heat flux, and the predicted Nusselt number correlation, will add to local knowledge a significant mean to gain more heat in large scale concentrated solar power plants.

A soft core processor system is constructed using embedded design techniques and it is configured on Field Programmable Gate Arrays (FPGAs). The system is accommodated to act with Direct Memory Access (DMA) mode using suitable Xilinx Intellectual Property (IP) core. A dual data rate synchronous dynamic random access memory (DDR_SDRAM) with 64 Mbyte capacity is introduced to the system and accessed by the DMA controller.The controller is performed to transfer programmable quantity of data from source address to destination address without intervention of the processor. Spartan-3E slice is used and programmed using Xilinx Platform Studio (XPS)which is provided by Xilinx integrated software environment at (ISE 10.1). The system performance is tested by transferring data from matlab media to the DDR_SDRAM and vice-versa, mat lab 2012a version software is used for this type of data transfer.

The film cooling effectiveness and local heat transfer coefficient for coolant jet holes direction (orientation angle), have been investigated. Experimental investigations were done on a flat plate by using a single test transient IR thermograph technique.Evaluation of the cooling performance is obtained by estimated both film cooling effectiveness and heat flux ratios. Three models of coolant jet holes are investigated,each model consists of two rows of holes arranged in a staggered way with different orientation angles. Model (1) downstream row with acute angle and the upstream row with obtuse angle; model (2) both rows with obtuse angles, while model (3) both rows with acute angles. The holes diameter is 4mm, the longitudinal distance between the upstream and downstream rows (X/D) is 4D, and the span distance between two neighboring holes (S/D) is 3D. Three blowing ratios of (BR= 0.5, 1.0, and 1.5) were used in the investigation program.In order to predict the flow behavior numerically for the cases under investigation CFD code is introduced.The numerical investigation shows two large vortices, pair of counter rotating vortex and horseshoe vortices,both vortices have major effects on cooling performance.The experimental results showed that the film cooling effectiveness increases as blowing ratio increases for models (1 and 2), while decreases for model (3), and model (1) provide better performance than the others a thigh blowing ratios.

Simulation of Heat transfer and laminar Sio2/water and Sio2/oil-engine flow over backward facing step with and without obstacle numerically studied in this paper. The finite volume method adopted to solve continuity,momentum and energy equations in two dimensions. The aspect ratio of triangular obstaclew/e= 0.5 presented.The step height and expansion ratio of channel were 4.8mm and 2 respectively, the range of Reynolds number varied from 100 to 250, constant heat flux subjected on downstream of wall was 2000W/m2.Two types of base fluid used in this simulation the water and oil-engine with constant properties at T = 300K°, The Sio2nanoparticles used with nanoparticles diameter 30nm and volume friction 4%. The average nusselt number noticed increase with increase Reynolds number withobstaclefor two basefluid and also noticed that the nanofluid of Sio2-oil engine has higher nusselt number compared with other nonofluid. The result shows increase of local nusselt numberfor backward facing step with obstacle in compared to those without obstacle. The maximum enhancement of heat transfer observed at obstacle due to increase recirculation flow after the obstacle. Streamline showing the increase of recirculation region with used obstacle in compared without obstacle and highest recirculation region observed at obstacle.

In this work, the bearing capacity of soil is evaluated for a substation of residential compound in Amarah city by plate loading test. The study consists of two parts, the first part is the field work which includes soil tests in the field for the locations of two rectangular foundations of transformers with dimensions (for each foundation) of (3.5 m x 2.5 m), called (Point 1 and Point 2).Results showed that the settlements in the locations of points 1 and 2 are within the permitted settlement, and the allowable bearing capacity of soil in these locations is (9.1) T/m2. In the second part of the study, the tested soils by plate loading test are analyzed using nonlinear three dimensional finite element models. ANSYS (11.0) program is used to analyze the three dimensional model. The adopted finite element models are found to give results in an excellent agreement with the field results. For the same applied load, it is found that the ratio of theoretical to field values of settlement is 0.99 for the both points (1) and (2).The effect of size of plate of loading has been carried out to investigate its effect on the predicted finite element results. It is found that the settlement is increased with increasing the size of the loading surface.

A finite rectangular plate with double edge crack under uniaxial tension depends on the assumptions of Linear Elastic Fracture Mechanics LEFM and plane strain problem are studied in the present paper. The effect of crack position, crack oblique and the kinked crack orientation are investigated to predict if a crack starts to grow. These problems are solved by calculating the Stress Intensity Factor SIF for mode I (KI) and II (KII) near the crack tip theoretically using mathematical equations and numerically using finite element software ANSYS R15. A good agreement is observed between the theoretical and numerical solutions. The results show that the KI increases with increasing the relative crack length and tensile stress and these values are increased when the crack position draws near the plate edge while in case of parallel cracks the mutual shielding effect reduces KI in each crack.In mixed mode, it is shown that the maximum values of KI and KII occur at crack angle β=0o and 45o, respectively and the orientation of the kinked crack have significant effects on the KI and KII.