Abstract: The effects of stimulated g-jitter which come together with heat and mass transfer by mixed convection in microgravity situation on MHD flow of Oldroyd - B fluid in porous space is investigated for a particular system. The system comprises of a pair of heated up perpendicular parallel infinite plates maintained at constant although various concentrations and temperatures. By using modified Darcy’s law, the equations governing the flow are modelled. These equations are solved exactly for the distributions of stimulated velocity, temperature and concentration. Interestingly the solutions for second grade and Maxwell fluids are recovered as new limiting cases of the present general results. Similar result in the relevant literature relating to Newtonian fluid is also obtained as a special case of the present solution. Finally particular attention is given to the graphical results for the velocity profiles of the oscillating flow in the channel. The analysis on the variations of embedded flow parameters in the solution expressions are presented and discussed.
Abstract: This computational study is aimed at studying the effects of flap deflection angle on aerodynamic coefficients of NACA 2412 airfoil and thus predicting the suitability of using the airfoil with flap at various phases of flight. The change in airflow over the airfoil at different angles of attack (0, 4, 8 and 12 degrees) and at different flap deflections give a clear understanding for the use of right combination of these two parameters. A full package of pictorial description for visualizing the changes in flow with and without the flap is provided through pressure and velocity contours.
Abstract: The oil transportation among the Middle East Countries and especially in Bahrain is extended and demands high performance and quality, reducing the leakages as well as the resistance to the flow simultaneously. Due to this reason in the present paper the crude oil dynamic behavior in a channel is studied in order to present valuable information for the flow variables and the separation zones according to various discharge or aspect ratios. The numerical approach is developed for T-junction channels due to the high oil and gas applications in the region, in order to transfer the oil from the source to the refinery. The most important aspect is the specification of the recirculation zones and stagnation points according to the flow velocity. The flow is steady, laminar and incompressible, while uniform, un-uniform and adaptive grids of various sizes have been generated in order to produce the desire accuracy even in high aspect ratio geometries. The results presents satisfied accuracy concerning the literature, while these are valuable data for the oil and gas companies in pipelines construction as well as to control operation issues.
Abstract: H-Darrieus wind turbines, due to their simple design and relatively low manufacturing costs have recently received much attention particularly for standalone applications. However start-up issues associated with their operation restricted their operation in areas of low average wind speed and encourages engineers to develop novel design. Several design proposed in this way but in most cases design came up with complex sensing mechanisms and mechanical actuators or high cost manufacturing parts. A recent rotor design called double Darrieus rotor proposed as a German patent case bridged these complexities appropriately. The aim of present study is to investigate this innovative design from aerodynamic point of view by means of validated CFD techniques. A flow-driven simulation setup based on 6DOF calculations employed in order to study rotor operation from stand still until peak performance obtained. Results from these precise modeling reveal the superiority of the proposed double-stage design in compare with the original H-Darrieus rotors in terms of start-up behavior and optimum performance.
Abstract: A novel micropump is proposed comprising a PMMA-based rotor, a circular PDMS micro-chamber, and a semi-circular PDMS microchannel connecting the inlet and outlet reservoirs as the rotor spins, a plug of sample fluid is trapped within the microchannel between neighboring blades of the rotor and is driven through the channel toward the outlet. Meanwhile, the rotors periodically compress and release the inlet and outlet regions of the microchannel. Thus, as the rotor turns, one plug of sample fluid is drawn into the microchannel as another is ejected into the outlet reservoir. In other words, a peristaltic pumping effect is achieved. It is shown that the flow rate in the proposed device can be controlled simply by adjusting the rotational velocity of the rotor. A maximum flow rate of 1.22 ml/min is obtained given de-ionized water as the working fluid and a rotational velocity of 232 rpm. Moreover, given the same rotational velocity, flow rates of 0.724 ml/min and 0.336 ml/min are obtained for salad oil and engine oil, respectively.
Abstract: In rotary ultrasonic machining (RUM), the traditional power transfer method was achieved by slip ring that cannot cope with high-speed rotary of the tool, which limits the machine potential of RUM. Based on the principle of electromagnetic mutual inductance and the technology of loosely coupled inductively power transfer (LCIPT), a contactless power transfer system (rotary transformer) is built for RUM to achieve its power transfer goal. Resonant Compensation technology is used to enhance the efficiency of the rotary transformer. And the performance of the rotary transformer is validated on Maxwell platform.
Abstract: In this work, 2-D/3-D forming problems (extrusion and deep drawing) are numerically simulated by extended finite element method (XFEM). The updated Lagrangian formulation is used to model the large deformation. The von-Mises yield criterion is used to model the elasto-plastic behavior assuming isotropic hardening. Penalty approach is employed to impose the contact constraints and non–penetration condition at the material interfaces. The level set approach is used for locating the material interfaces. The numerical simulations of two forming problems are presented using developed nonlinear XFEM code.
Abstract: Vapour compression heat pump will have good prospects in future large-scale spacecraft thermal control technology. Its environmental reliability and safety needs to be tested on the ground before being carried with the spacecraft launch. Vibration test is used to assess the anti-vibration capability in its transport and use. It is essential to build a performance test system of vapour compression heat pump to explore its operating characteristics at a given random vibration conditions. The results shows that the vapour compression heat pump is normal operation after the vibration and the cooling performance (COP) of 3.09 is achieved. Vibration test is equipped to provide a guarantee for future success carrying. The performance of vapour compression heat pump at high and low temperature and vacuum environment will be carried out.
Abstract: In this paper, the low cycle fatigue crack initiation life was regarded as a process of damage accumulation and a damage accumulation model was established based on the Continuum Damage Mechanics. By the model, we analyzed how the variable amplitude applied at the crack initiation stage influenced the low cycle fatigue life of high temperature materials. With the parameters of GQGH4169 alloy at room temperature, we determined the specific values of damage parameters by finite element method and numerical analysis method. Then, the crack initiation life predictions were carried out. The results show that using this approach can not only predict the crack initiation life of CT specimen accurately, but also reflect a definite influence of variable amplitude on the crack propagation life combining with the Paris Law, and the test costs reduced consequently.