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Lab3-Exercise_Note

# Lab3-Exercise_Note - 57:020 Mechanics of Fluids and...

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Unformatted text preview: 57:020 Mechanics of Fluids and Transfer Processes Laboratory Experiment #3 Measurement of Pressure Distribution and Forces Acting on an Airfoil S. Ghosh, M. Muste, S. Breczinski, J. Johnson, S. Cook, and F. Stern 1. Purpose The purpose of this investigation is to measure the surface pressure distribution, wake axial velocity profile, and lift and drag forces on a Clark-Y airfoil set at two angles of attack (0 and 16 degrees), and to compare the results, including their uncertainties, with benchmark data. The experiment will also introduce students to concepts related to digital acquisition systems: calibration, noise, settling time, and sampling time. Additionally, this laboratory will provide students with further analysis using an image-based system (ePIV/FlowCoach) with two Clark-Y airfoil models at angles of attack 0 and 16 degrees. 2. Experiment Design 2.1. Part 1: Wind Tunnel The geometry of and forces acting on a generic airfoil in a constant flow field (U ∞ ) are shown in Figures 1a and 1b. These experiments are conducted using a Clark-Y airfoil mounted in the test section of a closed circuit, open test section, vertical return wind tunnel (Figure 2). The tunnel enables measurements for turbulent flows up to Re = 300,000. ( Re = U ∞ c/ ν , where U ∞ is the free-stream velocity in the tunnel, c is the airfoil chord length, and ν is the kinematic viscosity of air). It has four 90 o corners equipped with turning vanes, two diffusers, a contraction section, test section and fan. The vanes, settling chamber and contraction section help in achieving a uniform flow in the test section. (a) Geometry (b) Hydrodynamics Figure 1. (a)-(b): Airfoil characteristics (a) Layout of the open test section wind tunnel (b) Airfoil schematic showing measurement system components Figure 2 (a)-(b): Wind tunnel layout The tunnel’s closed circuit is approximately 18.3 m long. The test section is a 0.76 m by 0.76 m square, 1.52 m long. A resistance temperature detector and a Pitot tube are placed upstream in the upper half of the test section to monitor and control the temperature and free stream velocity, respectively. The Pitot tube is connected to 1 a pressure transducer along with a digital display for visualization of experimental conditions. A Clark-Y airfoil was selected for the experiment because it exhibits good aerodynamic performance over a wide range of Reynolds numbers and also because there is abundant benchmark data available for comparison. The geometry of the Clark-Y airfoil and the positioning of the pressure taps used in the experiment are illustrated in Figure 3b. Positioning of the airfoil at various angles of attack is made with a hand wheel connected to a digital display. The airfoil is set on a pair of load cells that measure the overall forces (lift and drag) acting on the airfoil (see Figure 3a and 3c). An overall view of the system is provided in Figure 3a....
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Lab3-Exercise_Note - 57:020 Mechanics of Fluids and...

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