Fluid Mechanics 3-Aerofoil Lab Report
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 results in a particular air circulation pattern around it. This air circulation pattern results in the air above the aerofoil to have higher velocities than that below it. This generates higher pressures below the aerofoil and results in a net lift force that varies with the its angle of attack vis a vis airflow. As the angle of incidence increases, the point of flow separation moves forward towards the trailing edge of the aerofoil thus increasing the lift force. However, as the angle of attack increases, the rate of increase of lift force decreases. This pattern continues until the aerofoil reaches a point where the increase in angle of incidence no longer produces increase in lift force, this position is called the Stall. The theory also predicts that up to stall angle, the air circulation around the aerofoil is normal, it travels above and below the aerofoil from front to back. After stall angle however, a wake is formed above the aerofoil causing air above the aerofoil to recirculate to the front.
Apparatus
The apparatus used for this lab experiment consists of two NACA0015 aerofoils placed one in front of the other in a wind tunnel. One of the aerofoils, as seen in Figure 1, was lined with nylon tufts and had force balance
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 results in a particular air circulation pattern around it. This air circulation pattern results in the air above the aerofoil to have higher velocities than that below it. This generates higher pressures below the aerofoil and results in a net lift force that varies with the its angle of attack vis a vis airflow. As the angle of incidence increases, the point of flow separation moves forward towards the trailing edge of the aerofoil thus increasing the lift force. However, as the angle of attack increases, the rate of increase of lift force decreases. This pattern continues until the aerofoil reaches a point where the increase in angle of incidence no longer produces increase in lift force, this position is called the Stall. The theory also predicts that up to stall angle, the air circulation around the aerofoil is normal, it travels above and below the aerofoil from front to back. After stall angle however, a wake is formed above the aerofoil causing air above the aerofoil to recirculate to the front.
Apparatus
The apparatus used for this lab experiment consists of two NACA0015 aerofoils placed one in front of the other in a wind tunnel. One of the aerofoils, as seen in Figure 1, was lined with nylon tufts and had force balance
Bibliography: [1] Greated, C. (2013) Fluid Mechanics 3 Lecture Notes, University of Edinburgh [2] Kinnas, Dynamic Viscosity of Air as a Function of Time, http://www.ce.utexas.edu/prof/kinnas/319lab/Book/CH1/PROPS/GIFS/dynair.gif Accessed on 15/04/2013