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Measurement of Pressure Distribution and Lift for an Airfoil

Measurement of Pressure Distribution and Lift for an Airfoil. Purpose Test design Measurement system and Procedures Uncertainty Analysis Data Analysis and Discussions . Purpose. Examine the surface pressure distribution Compute the lift force acting on the airfoil. Test Design.

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Measurement of Pressure Distribution and Lift for an Airfoil

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  1. Measurement of Pressure Distribution and Lift for an Airfoil Purpose Test design Measurement system and Procedures Uncertainty Analysis Data Analysis and Discussions

  2. Purpose • Examine the surface pressure distribution • Compute the lift force acting on the airfoil

  3. Test Design Airfoil(=airplane surface: as wing) is placed in test section of a wind tunnel where a flowing fluid (air) is operating. This airfoil is exposed to: • Forces acting normal to free stream = Lift • Forces acting parallel to free stream = Drag Only two dimensional airfoils are considered: Top of Airfoil: • The velocity of the flow is greater than the free-stream. • The pressure is negative Underside of Airfoil: • Velocity of the flow is less than the the free-stream. • The pressure is positive This pressure distribution contribute to the lift

  4. AOA, and Pr Taps Positions

  5. Lift force The lift force L is determined by integration of the measured pressure distribution over the airfoil’s surface. It is expressed in a dimensionless form by the pressure coefficient Cp where pi = surface pressure measured, p = pressure in the free-stream U = free-stream velocity where r = air density ( temperature), pstagnation stagnation pr measured at the tip of pitot tube L = Lift force b = airfoil span c = airfoil chord

  6. Pressure Distribution on the Airfoil In this experiment, the lift force, L on the Airfoil will be determined by integration of the measured pressure distribution over the Airfoil’s surface. The figure shows a typical pressure distribution on an Airfoil and its projection .

  7. Protractor – angle of attack Resistance temperature detectors (RTD) Pitot static probe Scanning valve Pressure transducer (Validyne) Digital Voltmeter (DVM) Data Acquisition system

  8. Measurement System and data reduction

  9. A virtual instrument(VI) = Lift is an ADAS is used to calculate the lift coefficient Data needed: Total # of points considered Observation point list Sampling Rate Settling Time Length of each Sample Conversion Coefficients Angle of attack ADAS

  10. References plots with 6 different angles of attack: = 0 Group 1,2 = 4 Group 3,4 = 6 Group 5,6 = 8 Group 7,8 = 12 Group 9,10 = 14 Group 11 Reference Data

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