Aerodynamic performance and stall characteristics of the NACA4412 airfoil: low Reynolds number

The aerodynamic performance of airfoil blades in various design and off-design situations plays a significant role in developing their designs. The current study aims to obtain and critically examine the performance of the NACA4412 airfoil at discrete Reynolds number (Re) and Angle of Attack (AOA) combination by investigating pressure and velocity field mapping. The thorough analysis uses various experimental instruments to explore the flow phenomena, including particle image velocimetry (PIV), pressure transducers, and hot-wire anemometry. The suction side appears critical, as an unfavorable pressure gradient forced the flow within the laminar boundary layer to decelerate and separate. The AOA = 16° is found to be critical, as the recirculation zone's width and length are considerably large. The AOA = 18° is a stall angle as the flow only separates from the leading edge (LE). The flow separation is wholly suppressed at a low AOA range with an increase in Re for a constant AOA. As Re increases at a constant high AOA, the separation length, width, and recirculation strength rise significantly. The bubble formation is observed on suction side at low Re and lower AOA. The results of our hot wire experiments and pressure transducer agree with the PIV findings. Additionally, the surface flow pattern using smoke flow visualization supports the findings. As the AOA exceeds the critical angle, the lift coefficient reduces, and the drag coefficient increases significantly. Also, the momentum thickness at the trailing edge and the wake survey show high loss above critical AOA.