Lab 11 - MAE309 Aerospace Engineering Laboratory II Year...

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MAE309 Aerospace Engineering Laboratory II Martin Suhartono - 20106182 Page 1 Year 2010 Month 12 Day 9 LIFT AND DRAG OF AIRFOIL MAE309 AEROSPACE ENGINEERING LABORATORY II Name: Martin Suhartono Student Id: 20106182

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MAE309 Aerospace Engineering Laboratory II Martin Suhartono - 20106182 Page 2 1. Objective The study of lift and drag of a 2 dimensional airfoil provides very important data used in the design of airplanes. In this experiment, pressure distribution on the surface of the airfoil will be investigated. From the pressure distribution, changes in lift can be determined as the angle of attack changes. 2. Experimental Equipment 2.1 Subsonic Wind Tunnel A subsonic wind tunnel is an open circuit wind tunnel with low turbulence. The air is sucked in through a centrifugal fan and passes through the diffusion section, screen, contraction section and test section before being discharged into the atmosphere. The test section has a width, height and length of 300mm, 300mm and 1000mm respectively. The wind tunnel used has a variable velocity range of 1 to 10m/s. 2.2 NACA0012 Airfoil The NAC0012 airfoil is symmetrical and has a thickness ratio of 12%. In this experiment the airfoil has a chord length of 150mm. 2.3 Pressure Sensors To obtain the lift, surface pressure of the airfoil has to be measured. There are a total of 25 pressure holes on the top and bottom side of the central part of the airfoil. Pressure sensors fixed to the under sides of these holes measure the pressure and feed the data to the computer. 3. Experimental Procedure 1. Measure the velocity in the wind tunnel using an anemometer. 2. Change the airfoil angles of attack from -20° to 20° at 2° intervals. 3. Measure the pressure distribution on the wing surface at 2° intervals. 4. Change the flow velocity and repeat steps 2 and 3.
MAE309 Aerospace Engineering Laboratory II Martin Suhartono - 20106182 Page 3 4. Results and Discussion The equations used in this experiment are as follow: The first equation basically tells us that we need to deduct all the values recorded from the pressure gauge by the base values which are recorded beforehand. Furthermore, the pressure at channel 13 for 0 0 angle of attack is actually the stagnation pressure, P o while the dynamic pressure can be calculated correspondingly by knowing the free stream velocity (5, 10, 15, 20 and 25 m/s). This will yield us the free stream pressure, P that will be used to calculate the pressure coefficient using the third equation. Lastly, we use the fourth equation to calculate the corresponding lift coefficient, Cl, where, the term Cpl is the pressure coefficient of lower surface and Cpu is pressure coefficient of the upper surface. Nevertheless, as integration is relatively difficult for our discrete data, hence we can actually multiply the small change in length d(x/c) with the average values of (Cpl Cpu) for each particular length directly for an approximate result. The method to calculate Cl will be explored further after the presentation of the Cp graphs.

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