The paper "Aircraft Wing Airfoils" is a great example of an article on engineering and construction. Airfoils are important inventions in the aircraft industry. Airfoils have found their way into several uses within the aeronautical industry with various adjustments to suit any given nee at a particular time. This article seeks to uncover the misconceptions that are associated with the airfoil and its ability to generate lift. Further, the shape of the airfoil is also covered accordingly with the related equations and their dependents being listed. At the end of this article, the NACA 4418 airfoil is analyzed using the XFLR5 software package to generate plots of CL and CD in order to create further knowledge on the topic. Discussion The common explanation for lift is centered on the immersion of an airfoil in streamlines of flowing particles.
Those backing this school of thought have indicated that based on the diagram below, where the distance from stagnation point S to the edge T which is referred as the trailing edge is greater at the upper surface as compared to that of the lower surface.
The misconception on this theory is quoted as in the distance argument which is not a mandatory condition for generation of lift. This is compared to the schematic analysis of a sail whose lower distance is a complete inverse or even equal in some areas and yet lift is generated. This offers an explanation that the distance theory is wrong and does not, therefore, achieve the integrity desired as a self-explanatory theory (Babinsky, 2003). Figure 1: Smoke streamlines surrounding the airfoil (Babinsky, 2003). It is also argued that fluid particles are bound to meet at the trailing edge T shown in diagram 1 above.
Real-life observations on why these particles take the same time in order to cover the distance ST are wrong. In an experiment to demonstrate that this is actually a misconception, simultaneously injection of smoke particles in an upstream manner usually generates a line of smoke whose particles scatter below and above the airfoil. The particles on the upper surface reach the trailing edge before those of the lower surface thus the equal time argument does not hold water (Babinsky, 2003). Bernoulli’ s principle has also been wrongly applied in coming up with a demonstration of lift in airfoils.
Application of high-velocity air on a curved paper generates lift and it is believed that the high difference in velocity of air particles flowing in the opposite direction generates differential pressure. This is actually wrong according to Babinsky (2003) who gives an affirmation that the connection between the two sides of the paper cannot be demonstrated using Bernoulli’ s principle. In doing this he establishes the argument that if pressure along with an airfoil increases then it is definite that the velocity reduces and vices versa. Generating lift in an airfoil is strictly dependent on Newtonian’ s laws of motion and Bernoulli’ s principle.
Newtonian’ s law poses the idea of airfoil lift being a reaction force since there must be the exertion of force in order for direction to change. The exertion force achieves an equivalent of equal magnitude but in a different direction. This is simply put as; while the airfoil exerts a downward force against the air planar, the air exerts force upwardly thus achieving a lift.
This argument is derived from Newton’ s second law of motion which states that for every action there is an equal reaction force in the opposite direction. Pressure differences have also been used to describe this contentious issue in that the net force is compared to the pressure differences that are demonstrable in equation (1) below. A slight pressure difference on the upper surface of an airfoil poses a reaction on the underside pressure which eventually triggers lift in a bid to generate a balance between the two (Langley Flying School, Inc. , 2013).