Airfoil in a Wind Tunnel Experiment #6 Ruben Colon #75199

Outline Introduction Experimental Procedure Experimental Result Discussion Conclusion Recommandations

Introduction An experiment was conducted to test an airfoil to evaluate the lift and drag forces under different angles of attack. The data were taken at different rpm and angles of attack of the airfoil. The value of coefficient of lift, the coefficient of drag. This experiment illustrates the principle of flying by testing a scaled airfoil (NACA2415) in a wind tunnel.

Experimental Procedure Task No 1: Pressure distribution along the airfoil surface Turn ON the wind tunnel and all the complementary devices. Set the angle of attack to zero degrees. This will remain constant during the experiment. Set the value of the tunnel velocity to 10 m/s and wait until computer shows steady values. Record pressure for all tapings along the airfoil. Repeat all steps for wind tunnel velocities of 18 and 25 m/s.

Experimental Procedure Task No 2: Pressure coefficient along the airfoil surface Turn ON the wind tunnel and all complementary devices. Set the tunnel velocity to 25 m/s. This will be kept constant during the experiment. Set the angle of attack to -2 and wait until computer shows steady values. Record pressure for all tapings along the airfoil. Repeat all steps for angles of attack of 0, 8.

Experimental Procedure Task No 3: Lift on the airfoil Turn ON the wind tunnel and all complementary devices. Set the the angle of attack to 0. Set the wind tunnel velocity at 10 m/s, and then let the system get steady. Record pressure for all tapings along the airfoil. Change wind velocity at 15 m/s, 20 m/s, and 25 m/s and repeat steps c and d. After you finish with the last velocity, repeat all steps for the angle of attack of 8o.

Experimental Procedure Task No 4: Stalling on the airfoil Turn ON the wind tunnel and all complementary devices. Set the tunnel velocity to 25 m/s. This will be kept constant during the experiment. Set the angle of attack to 10o (starting point) and wait until computer shows steady values of pressures on the upper surface of the airfoil. Then increase the angle of attack by 1o and observe if there is sudden change of pressure on the upper surface. If not, repeat this step. If there is a sudden change on pressure distribution, then record the previous distribution and the following one.

Experimental Result Pressure Distribution

Experimental Result Pressure Coefficient

Experimental Result Lift vs Wind

Discussion Initially, during the experiment collected all data from the NACA 2415 wind tunnel. The pressure coefficient describe el behavior of the relative pressure in a dynamics flow, this value is non-dimensional. The lower airfoil surface show a consistent pattern at the increasing pressure coefficient and in the upper surface decrease the coefficient along the airfoil. As the previous figures, the upper side has the lower pressure, and the pressure magnitudes for this case are higher. As expected, keeping the angle of attack constant and increasing the wind speed, one can increase the pressure differential in the airfoil, creating Lift.

Conclusion In this experiment we can conclude that the way that air flow moves affects how the pressure distribution and lift is manifested in an airfoil. We must also add that decreasing the angle of attack results in a negative or downward lift and that increasing it results in a positive or upward lift. One also has to take into consideration that while you increase lift by increasing the angle of attack if you reach stall conditions the aircraft will loss lift and will plummet making this a very dangerous state but one very important and necessary to know when designing for airfoils.

Recommandations Having a larger space for the wind tunnel.