Basrah Journal for Engineering Sciences

An experimental investigation was conducted on a low-speed wind tunnel with (50 mm × l00 mm) rectangular working section. Five smooth circular cylinders, as bluff bodies were applied. Cylinders diameters are 12.5, 15, 17, 35, and 37 mm, which experience a blockage ratio of 12.5%, 15%, 17%, 35%, and 37%, respectively. The range of Reynolds No. and air velocity for the present study is 0.7 × 104 - 5 × 104 and l0-20 m/s respectively, which are more applicable in the engineering field. The experiments were carried out in the fluid mechanics laboratory, Faculty of Engineering and Technology, Sebha University, Libya. Results indicate that cylinders of a blockage ratio of 35% and 37% experience lower pressure coefficients around bodies, lower velocity distribution in the wake, and higher drag coefficients. Drag coefficient correction is agreed with the unconfined flow for a blockage ratio of less than 17%. Wake and buoyancy blockages may affect models of higher blockage ratios.

In this paper, the influence of thermal residual stress on the strength and fracture rotating speed of composite discs is studied and analyzed using the finite difference method and laminated plate theory for two types of reinforced composite discs (radial fiber reinforced disc and circumferential fiber reinforced disc). As a result, the thermal residual stress will reduce radial and tangential stresses in radial fiber-reinforced discs, while it shall increase radial stresses and decrease tangential stresses in circumferential fiber-reinforced discs. The existence of residual stresses in the composite discs will lead to the initiation of cracks and begin to propagate near the inner diameter compared to cases when neglecting residual stress for cases taken in the analysis. It is also verified that the finite difference method is a good tool for the stress analysis of composite discs under the residual stress effect.

In this paper, depending on the finite element method, the J-integral program is developed for a stationary circumferential crack problem in elastic-plastic fracture mechanics in pipes under static loading and pure bending moment conditions. The program developed is applied to ductile cast-iron pipes (DCIP) to analyze the integrity assessment, i.e., the significance of crack growth by drawing both a failure assessment diagram (FAD) and a crack driving force diagram (CDF). A numerical procedure is used for elastic-plastic analysis, depending on the special equation to predict J-values taking account of the crack geometry and load condition. It is clear that the results obtained from the failure assessment diagram and crack driving force diagram are identical and the J-integral method can be used for the onset of crack growth in (DCIP) under bending moment conditions.

Electromagnetic flowmeters measure the flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations, the pipe may be partially filled. In this case, the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper, we have established a new numerical formulation, based on the finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations on the polar axis of the solution domain (cylindrical cut from the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one-half mesh width from the polar axis. The number of iterations that give convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy, i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.

A new model of bubble dynamics is constructed using a linear wave equation, including the effects of variation of the gas temperature inside the bubble and the liquid temperature near the bubble, and the effects of evaporation-condensation of the liquid vapour at the bubble wall. The liquid is assumed water and the gas inside the bubble is only vapour (neglecting non-condensable gas). The temperature inside the bubble and the liquid temperature is numerically calculated by solving the energy equation both inside (vapour-phase) and outside (liquid-phase) the bubble (using the finite difference method). The pressure inside the bubble is obtained numerically without assuming that it follows any assumed relation. The results reveal that the bubble radius, the liquid temperature, and the pressure and temperature inside the bubble change with time periodically. Both the pressure and temperature become higher when the radius becomes minimum. The present theoretical result is compared with data from other references and with another theoretical model to check the validity of the present model. The calculated result approximately fits with the data of the previous studies.

The goal is how to estimate the video quality of MPEG TCP-Friendly video streaming over a robust wireless channel against frequent packet loss. In this paper, a Forward-Error-Correction (FEC) scheme is used as an intra-protection control over an Additive White Gaussian Noise (AWGN) wireless channel behind wired links. For this purpose, we propose a Variable Frame Rate based on the TCP-Friendly Rate Control (VFR-TCP) algorithm to evaluate the predicted frame rate of MPEG-4 video streaming. Quality of Service (QoS) is also evaluated by the predicted quantizer scale Q for the case that the network throughput is assumed to be equal to the required bandwidth. As a result, we obtained a good and reasonable perceived video quality over a noisy wireless channel, by varying the channel error rate or the channel SNR where AWGN and a coded BPSK scheme are dominated.

This paper describes a study of traffic behavior at AL-Jumhoryia Street in Baghdad city. The objective is to use the simulation program OSPSM to evaluate the performance of on-street parking. The first stage of this research project takes the basic measurements carried out using a video camera. The basic measurements are traffic flow, operating speed; parking time, unparking time, gap, and average duration. The second stage of the simulation program OSPSM was to run it using all the observed input parameters to obtain some measures of effectiveness such as the delays caused to through vehicles, the delays caused to parked vehicles, reduction in capacity, turnover rate, Parking Index, and Parking accumulation. The main conclusion to the performance of on-street parking is that it is reasonable, the average delay of parked vehicles and through vehicles at AL-Jmahory Street is an accepted value.

The present work investigates the effects of drinking water on the erosion-corrosion rate and Vickers hardness of (Al-Si) and (Al-Mg-Si). Al-Si alloy is well-known as a casting alloy with high wear resistance, low thermal expansion coefficient, good corrosion resistance, and improved hardness at a wide range of temperatures. While Al-Mg-Si alloys have good formability, weldability, machinability, and corrosion resistance. The alloy specimens that are used for piping and containing water and carbonated water were exposed in erosion-corrosion systems in factories by using drinking water type AQUAFINA as exposure media for different exposure times (l-30) h to measure the erosion-corrosion rate. The results show that there is a small difference in the rate of corrosion, moreover, (Al-Mg-Si) alloys have high resistance to erosion-corrosion in drinking water due to the consisting of (Mg2Si) phase which precipitates as fine particles due to resist dislocations movement lead to high corrosion strength and the (Al-Si) alloy have high Vickers hardness at natural aging due to the present of high ratio hardening silicon element.