Proceedings of the
International Conference on Mechanical Engineering 2009
(ICME2009) 26- 28 December 2009, Dhaka, Bangladesh

ICME09-FM-08

EXPERIMENTAL INVESTIGATION ON FLUID FLOW SEPARATION
CONTROL

Mohammad Mashud, A. Al Bari and T. P. Bhowmick
Department of Mechanical Engineering
Khulna University of Engineering & Technology
Khulna-9203, Bangladesh

ABSTRACT

The aim of the research is to control the flow separation of an airfoil by providing a partial bumpy on the upper surface. The presence of friction in the flow causes a shear stress at the surface of the body, which in turn contributes to the aerodynamic drag of the body i.e. skin frictions drag. However, friction also causes another phenomenon called flow separation, which in turn creates another source of aerodynamic drag called pressure drag due to separation. From a fluid dynamist’s point of view, the performance of an aircraft is essentially controlled by the development of the boundary layer on its surface and its interaction with the mean flow. This interaction decides the pressure distribution on the airfoil surface, and subsequently the aerodynamic loads on the wing. In order to obtain the highest levels of performance efficiencies for mission varying aircraft, it is necessary to either: (a) alter the boundary layer behavior over the airfoil surface—flow control methods of interest here, and/or (b) change the geometry of the airfoil real time for changing free stream conditions—adaptive wing technology. Geometry of the airfoil can be changed by providing bumpy on the upper surface. The value of the aerodynamic efficiency needs to be maximum i.e. the lift to the drag ratio needs to the maximization. For this case lift should be high and drag should be low, which increases aircraft efficiency. To investigate the effect of introducing large scale surface roughness through static curvature modifications on the low speed flow over an airfoil, two types model are prepared. One is regular surface model another is bumpy surface model. All the models are prepared by wood and the experiments are conducted using 36×36×100 cm subsonic wind tunnel. . From the experimental investigations it has been observed that the flow separation on the airfoil can be delayed by using the bumpy on the upper surface. Flow separation occurs at 8° angle of attack in the smooth surface. But in bumpy surface it occurs at 14° angle of attack. That indicates the bumpy surface successfully controls the flow separation and increases the lift force of an airfoil.

Keywords: Flow Separation Control, Partial Bumpy surface, Airfoil and Aerodynamics.

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