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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

Measurement of Pressure Distribution and Lift for an Airfoil

Purpose

Test design

Measurement system and Procedures

Uncertainty Analysis

Data Analysis and Discussions

purpose
Purpose
  • Examine the surface pressure distribution
  • Compute the lift force acting on the airfoil
test design
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

lift force
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

pressure distribution on the airfoil
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 .

data acquisition system
Protractor – angle of attack

Resistance temperature detectors (RTD)

Pitot static probe

Scanning valve

Pressure transducer (Validyne)

Digital Voltmeter (DVM)

Data Acquisition system
slide9
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
reference data
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