Abstract: Airlift pumps provide reliable means of artificially lifting of liquids or liquid-solid mixtures from deep wells or vessels. This paper presents a numerical investigation into the effects of air injection strategy, single-stage vs. multistage air injection, on the airlift pump performance. A numerical model of airlift pump, based on the concept of momentum balance, was developed and validated against available experimental data. Predictive studies on model airlift pump with different arrangements of injected compressed air were numerically carried out. Numerical results showed that applying the commonly used single-stage air injection causes a steep change in the pump output-input characteristic curve followed by a fast decay after the optimum point. Injecting the compressed air in a number of air injection stages, on the other hand, was shown to increase the range of bubbly-slug flow regime as well as the pump operating window close to the optimum conditions. Improvement in the pump performance at higher degrees of air input mass flow rates is expected when employing multistage air injection.

Abstract: In recent years, there has been more attention to predict the behavior of vessel in the sea (sea keeping). The more the speed of vessel increases in the high speed and light vessels, the more calculations are necessary. In this paper, a BP (back propagation) neural network is presented that keeps sea keeping indexes under the categories of input and output of the network. Evaluation is based on a corvette model, and the stability parameter of wave has been evaluated by using MATLAB software. Comparison between the network output values and the expected values represent the amount of error, which is negligible, indicating that assessing the wave’s stability values is possible via using (BP) back propagation neural network.

Abstract: In this work, a numerical method was developed, by a reliability mechanical coupling, in order to define the reliability index and probability of failure evolutions for pipelines under corrosion effect. The chosen model, takes into account uniform and localized corrosion. Thus, the hardness and tensile tests were worked out to characterize the mechanical properties of pipelines material. Once the model was defined, a simulation was carried out by the software Phemica. The importance factors were also estimated. A methodology has been presented for the reliability analysis of pipelines subjected to localized corrosion. The variables influencing the reliability are treated as random variables and represented by suitable statistical distributions. An approximate limit state function was developed. Advanced first-order second moment reliability theory was employed for the estimation of the probability of pipeline failure by Phimeca software logiciel. From a numerical investigation, it was found that both defect depth and fluid pressure have significant influences on pipeline reliability.

Abstract: Nowadays, high strength steels are getting very popular all over the world for various applications such as in auto body making, machine parts manufacturing, steel structure buildings, concrete reinforcement, etc. In Bangladesh, use of high strength TMT steels bars has got a momentum in the construction of flyovers, bridges and high rise buildings because of its good combination of the required mechanical properties. In this research work, locally produced high strength TMT reinforcing steel bars (20 mm dia.) of two different companies have been investigated. As a part of this research work, at first, details microstructural morphologies of hardened case, transition zone and core of both steels were investigated by optical microscope and they were then photographed. After that, Rockwell hardness was measured on different zones. Tensile tests were also carried by a Universal Testing Machine at room temperature. After tensile tests, details of the fracture modes of the steel bars were studied carefully. The fracture modes were then discussed in terms of chemical compositions and carbon equivalents, resulted microstructures, case and core hardness, depths of hardened case and transition zone of the steel bars.

Abstract: The FEM analysis of ultrasonic tool has been done in addition to surface roughness of machined samples using ultrasonic machining process have been presented. The experimental conditions were designed by using DOE approach. The analysis of results has been done using the MINITAB 14.0 software and results obtained are validated by conducting the confirmation experiments. The F-test and P-value has been applied to determine the significant parameters.