Conclusion
The flow fields have been simulated around a NACA 0012 aerofoil, a flat plate and a curved plate at angle of attack 2°-7° with an interval of 1°. The simulation flow is the unsteady-state two-dimensional laminar flow at the Reynolds number of 4,000.
- Among the three aerofoils, leading edge vortex is proved to exist over the leading edge of the curved plate at the angle of attack 2°, 3° and 4°. It is a steady feature attached over the leading edge and covers 10%, 22% and 40% of the chord length respectively for the angle of attack 2°, 3° and 4°. The increasing of angle of attack (2°-4°) leads to augment of the size of the leading edge vortex and subsequently after 4° the increasing of angle of attack can result in the vortex shedding.
- The curved plate at the angle of attack 2°, 3° and 4° where the leading edge vortex exists, shows lower lift coefficient and higher drag coefficient. It is not evident that the leading edge vortex is able to enhance the fly performance as found from the previous research in literature review.
- The vorticity in the flow is generated above the leading edge and then convected to the surroundings. The leading edge vortex which exists as a thin layer over the leading edge has low vorticity and plays a minor role in the vorticity production and convection.