Browsing by Author "Nawrin, Sumaiya"

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CFD analysis of aerodynamic performance of NACA 0018 airfoil considering suction and internal slot
(Department of Mechanical Engineering, 2021-11-30) Nawrin, Sumaiya; Ali, Dr. Mohammad
The control of flow separation is one of the important ways for the reduction of drag as well as the increase of lift to drag ratio. In the domain of aerospace technology the main focus of this study is the enhancement of lift force, the reduction of drag force and in combination the enhancement of lift to drag ratio. In order to achieve these objectives, both active and passive controls of flow separation on 2D NACA 0018 airfoil are considered and CFD simulation is performed on this configuration. The computational runs are made at Reynolds number 7.12x106 and angles of attack ranges from 0° ~ 25°. This investigation primarily focuses on the flow separation delay by suction with a slot of width 2% of the chord length placed at different locations of the airfoil to find optimum position. Suction pressures are expressed as the percentage of atmospheric pressure and accordingly four different suction pressures: 44%, 54%, 64% and 74% are considered to find out the best suction position based on the aerodynamic performances. As a passive flow control of separation, two different configurations of internal slots are then introduced, one is tangential internal slot and the other is leading edge chordal slot. The result shows that the performance of tangential internal slot is better in comparison to that of leading edge chordal slot. For getting better result, the optimum position of tangential internal slot is sought and considered for further CFD simulation and analysis of the result. Finally, the combined effects of tangential internal slot near the leading edge and suction near the trailing edge are studied. The result shows that the combination of suction and tangential internal slot moves the separation point from 46% to 72% of the chord length while for only tangential internal slot the separation occurs at 68% of the chord length. The detached flow reattaches at 97% of the chord length position for plain airfoil with and without the tangential internal slot and for the combined effect of suction and tangential internal slot the reattachment occurs at 73% of the chord length position. This modified configuration increases lift force, decreases drag force and increases lift to drag ratio significantly. The tangential internal slot increases lift to drag ratio as 9% compared with plain airfoil whereas the combination of tangential internal slot and suction increases 17% lift to drag ratio. The result also shows that the stall angle is increased by this modified configuration in airfoil. The outcome of this investigation might help the airfoil designers to achieve much better aerodynamic performance.
EFFECT OF FIN ON THE PERFORMANCE CHARACTERISTICS OF CLOSE AND OPEN LOOP PULSATING HEAT PIPE
(R&D Wing, MIST, 2015-03) Rahman, Brig Gen Md. Lutfor; Nawrin, Sumaiya; A Sultan, Rasel
Pulsating heat pipe (PHP) is a two-phase thermal control device with arbitrary number of turns which is basically used for the thermal management of microelectronic devices as there is a requirement of miniaturization of heat exchangers. To fulfill today’s increasing demand of power electronic applications PHP is a proven technology which works on principle of oscillation of the working fluid and phase change phenomenon in a capillary tube. An experimental investigation has been done on both close and open loop pulsating heat pipes by using suitable working fluid to observe their thermal performance. It has performed on 2 mm inner diameter and 2.5 mm outer diameter open and close loop pulsating heat pipe with fin added on the condensation section. The overall experiment is done by using methanol with 50% filling ratio at 0⁰ (vertical) inclination angle on close loop pulsating heat pipe (CLPHP) and open loop pulsating heat pipe (OLPHP) with 8 loops. In both the pipe evaporation section is 50mm, adiabatic section is 120 mm and condensation section is 80 mm. The main objective of this experiment is to observe the effect of their thermal performance while using fins and without fin i.e. the basic form. The paper attempt theoretical and experimental investigation on the thermo-physical properties of working fluid and will also show the result regarding the significance of using fin on CLPHP and OLPHP. Keywords: PHP, CLPHP, OLPHP, fin with condensation section. Anaerobic treatment of high strength industrial wastewater is a well established industry in the developed world. Along with the treatment of wastewater requiring no aeration and thus being highly energy efficient the byproducts of anaerobic treatment hydrogen and methane gases are sources of clean renewable energy. This paper evaluates the potential of biogas generation in the Bangladesh Military Savar dairy milk processing facility by detailed characterization of the wastewater discharge flow pattern and characterization of the wastewater. A theoretical methane generation evaluation was conducted based on the wastewater flow and waste characterization. This was then related to the potential high value generation in terms of electricity production to show the potential of anaerobic agro based industry wastewater treatment with simultaneous generation of renewable energy.