Abstract:
The main function of a wing of an aircraft is to generate lift force to make the flight possible in the air. This force is generated by a special wing cross section which is called areofoil. and the silhouette of the wing when viewed from above or below is known as wing planform. In this research, NACA 4412 aerofoil planform is used due to have good stall properties and low roughness effect. As the aerodynamic characteristics of aerofoils play a pivotal role to develop an aircraft, it is wanted to explore aerodynamic characteristics from five planforms (wooden-plastic) models. All the models are prepared keeping the overall surface area alike with changing the aspect ratio (AR) of wings. The rectangular planform (Model-1: AR- 1.929) is considered as reference model to compare with the other models which are incorporating curvature at the leading edge for two models (Model- 2: AR- 2.96 and Model- 3: AR- 2.57) and at the trailing edge for two models (Model- 4: AR- 3.11 and Model- 5: AR- 2.96).
All the models are tested at air speed of 79.20 kph (0.06 Mach) i.e. at Reynolds Number 1.74 x 105 in the closed circuit wind tunnel. The static pressure at -4˚, 0˚, 4˚, 8˚, 12˚, 16˚, 20˚ and 24˚ angle of attack are measured from both upper and lower surfaces of models by using a multi-tube manometer. After analyzing the data, it is found that the curved trailing edge wing planforms. have better lift coefficient, lower drag coefficient and better lift to drag ratio than other planforms whereas the curved leading edge planforms have better performance than rectangular planform. It is found that a wing of high AR (Model- 4) is produced less induced drag than a wing of low AR due to the less air disturbance at the tip of a longer and thinner wing.
It is observed that the critical angle of attack of all the five planforms remain around 16˚ beyond which the stall occurs. So, to obtain maximum lift from NACA 4412 aerofoil, the wing needs to be positioned at around 16 degrees with respect to the flight path whereas curved trailing edge planforms of NACA 4412 shows the better result. Therefore, this type of models may be considered to design a wing of aircraft.
