Essay about Fluid Mechanics 3-Aerofoil Lab Report

1572 Words Oct 26th, 2013 7 Pages
Fluid Mechanics 3-Aerofoil Lab Report

Introduction
This report aims to investigate the effect the angle of attack of an aerofoil has on the air flow around it. This was done by recording the lift and drag forces the aerofoil experienced when positioned at different angles of attack. The experimental lift force the aerofoil experienced when positioned at different angles of attack was then compared with theoretical values. An attempt was made to explain any discrepancies between experimental and theoretical values.
Theory
When air is blown over an aerofoil, it separates into two distinct sets of streamlines above and below it separated by a dividing streamline. The shape of the aerofoil
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This is dues to the fact that the point of airflow separation is starting to reach the trailing edge of the aerofoil. The geometry of the trailing edge causes lift to be transmitted less efficiently. The line representing the theoretical value of the lift coefficient does not show any change in the rate of increase of lift because it assumes the object experiencing lift force is an infinite flat plate. Thus, it assumes that there is no change in geometry.
After 13° the lift force experienced by the aerofoil decreases while the drag force increases dramatically. This is due to the fact that at stall, the point of separation of the airflow streamlines travels beyond the part of the trailing edge that allows it to produce lift. Thus the lift force exerted on the aerofoil decreases. The more the angle of attack increases, the bigger the perpendicular area of the aerofoil to the airflow and the larger the drag force .The total resultant force applied on the aerofoil is composed of lift and drag. Therefore, if the resultant force on the aerofoil stays relatively constant, drag force will increase as lift decreases.
The way by which the data from which the lift and drag coefficient lines are plotted has certain sources of inaccuracy. Errors could come from the inaccuracy of measurements taken to calculate the pressure head and the angles. Furthermore, major sources of inaccuracy are the voltmeters used as the values displayed

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