Abstract
In this study, the effect of cutting the end of a thick airfoil and adding a cavity on its flow pattern is studied experimentally using PIV technique. First, by cutting 30% chord length of the Riso airfoil, a thick blunt trialing-edge airfoil is generated. The velocity field around the original airfoil and the new airfoil is measured by PIV technique and compared with each other. Then, adding two parallel plates to the end of the new airfoil forms the desired cavity. Continuous measurement of unsteady flow velocity over the Riso airfoil with thick blunt trailing edge and base cavity is the most important innovation of this research. The results show that cutting off the end of the airfoil decreases the wake region behind the airfoil, when separation occurs. Moreover, adding a cavity to the end of the thickened airfoil causes an increase in momentum and a further decrease in the wake behind the trailing edge that leads to a drag reduction in comparison with the thickened airfoil without cavity. Furthermore, using cavity decreases the Strouhal number and vortex shedding frequency.Graphical abstract
Highlights
Airfoils with thickened edges are used in subsonic flow to resolve many of the problems encountered in the conventional airfoils
The velocity field around the original airfoil and the new airfoil is measured by particle image velocimetry (PIV) technique and compared with each other
The PIV method is implemented via a laser-wave company continuous green light laser and a high-speed PCO camera used for measuring the flow velocity
Summary
Airfoils with thickened edges are used in subsonic flow to resolve many of the problems encountered in the conventional airfoils. Baker and Dam (2008) numerically and experimentally studied the FB-3500-1750 airfoil with blunt trailing-edge and used certain instruments to reduce the drag and increase the lift for improving the performance of this airfoil. They used a pyramidal balance for the measurement of the lift and drag at Davis aeronautical wind tunnel. By measuring pressure on the upper surface of an airfoil and implementing the particle image velocimetry (PIV) technique, Aravind and Al-Garni (2009) studied the flow behavior over a two-dimensional bluff body combined to a base cavity with various shapes. A base cavity is added to the back of the thick blunt trailing-edged airfoil and its effects on the relevant flow parameters are obtained
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