Fluid Mechanics 3-Aerofoil Lab Report Essay

1572 Words Oct 22nd, 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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-The protractor of the aerofoil connected to the lift and drag voltmeters was then used to vary the aerofoil’s angle of attack from 0° to 20°. Lift and Drag voltage values measured for each angle were recorded and calibration coefficients of 6.7 and 6.4 were used to obtain force Newton values for lift and drag. The lift and drag forces obtained for each angle were then plugged into equations (3) and (4) to obtain lift and drag coefficients. Equation (5) was used to calculate a theoretical value for the lift coefficient. (3) A represents the area of the aerofoil (4) (5)
The values obtained were then tabulated, graphed and compared.
-The Reynolds number of this experiment was then calculated using equation (4) where c is the length of the aerofoil chord and is the dynamic viscosity of air. (6)
Results
-Equation (6) was used to calculate the Reynolds Number which equated to 119366.

Discussion
The graph in Figure 3 confirms the theory stating that as the angle of attack of an aerofoil increases, the lift force it experiences also increases until it reaches stall position. The graph clearly shows the lift coefficient steadily increasing with angle of attack. This is due to the fact that as that as angle of attack increases, the point at which the airflow separates into streamlines going above and below the aerofoil moves forward thus providing more lift force. Lift force continues to increase until the angle of attack reaches 13° marking the angle

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