Aerodynamic_Forces_Lab.docx

UNIV-EN 1131 Student Success Aerodynamic Forces Lab Learning Objectives In this lab, you will learn about the following concepts: - The concept of aerodynamic force in airfoils - Some basic terminology of wings and propellers - Basics of wind energy production - Measuring the aerodynamic lift of a wing section - Measure the electrical output of a wind generator - Using a spreadsheet to compile, calculate, and visualize data sets. - Calculating the statistics of the data taken by all the teams in your section Deliverables - Day A and Day B worksheet filled out as a TEAM but ALL team members must upload a copy - A filled-out Word document of the reflection report (last page), worked on INDIVIDUALLY and uploaded by INDIVIDUALLY by all team members Introduction Aerodynamic forces play an important role in many of the conveniences in modern life, in such areas as airplane propellers and wings, automotive design, wind generation, and the design of building. In this lab, we will seek to explore of aerodynamic forces in a wing section and a propeller. Figure 1. Photo credit: quora.com

In courses such as MAE 3182 (Aerodynamics and Fluids Lab), MAE 3305 Flight Performance, Stability, and Control), CE 3305 (Basic Fluid Mechanics), these concepts as explored in more detail. Wing Airfoils The general shape of symmetric and cambered airfoil types are shown in the Figure 1. Symmetric designs are suited to higher-speed operation and cambered designed work well at lower speeds. The airfoil creates force called lift due the different path taken by the air above and below the wing as shown in Figure 2. The air travels faster on the top (covering a longer distance in the same time) and slower on the bottom causing a higher pressure on the bottom than the top of the wing, pushing the wing up. When looking at the wing, the following figure shows several important parameters. The chord line is drawn from the leading edge of the wing to the trailing edge. The angle between the chord line and the air stream is called the angle of attack. A cambered design can even produce lift at a zero degree angle of attack, whereas a symmetric design requires a positive angle of attack to produce positive lift. Figure 2. Photo credit: uaf.edu Figure 3. Photo credit: aerospaceweb.org

In our lab, we will evaluate a symmetric airfoil section. Each team in the lab will evaluate a custom made airfoil, each with varying properties. Propellers Another application of the airfoil is in the design of propellers. The propeller uses a different set of parameters to describe it, with the concept of angle of attack being replaced by the pitch of the propeller. A way of thinking about pitch is to consider the amount of forward progress a propeller will make for every revolution. For instance, Figure 4 shows a typical RC plane propeller sized 12x6 which indicates a tip to tip distance of 12” and a forward movement of 6” for every rotation: One interesting thing to consider is that there is often a twist in a propeller so that the angle of attack remains constant along the blade from the root to the tips. In other words, the circumferential path taken by a point on the propeller near the root is less a point at the tip so the angle changes from tip to the root. This can be seen in Figure 5: Figure 4. Photo credit: rc-airplane-world.com Figure 5. Photo credit: pilotfriend.com

In our lab, we will test a small model wind generator using 3 propeller blades which allow the pitch to be changed. Materials For this lab, you will need the following materials: Table 1 Component Count Wing airfoil platform (per team) 1 Wind generator platform (per team) 1 Scale (with 1g resolution to measure wing lift) 1 Voltmeter (to measure wind generator output) 1 Protractor (to measure angle of attack) 1 Fan (per table – per team pair) 1 Letter size paper for 11” separation (one per team) 1 More Information This course was developed by the College of Engineering PI (Program Initiative for New Students) team, with members from each department in the College. The lab was designed by Dr. Jason Losh (CSE Department) and Dr. David Ewing (MAE Department). All members of the Engineering PI group hope that you find this lab interesting and insightful. Please feel to contact your instructor, jlosh@uta.edu , or david.ewing@uta.edu if you have feedback or further questions about this lab. Setup for Wing Airfoil Measurement (Day A)

You will start with an airfoil platform assigned to your group, such as the one shown in Figure 6. The airflow will approach the airfoil from the left. Figure 6 Using the box fan on your table (shared between 2 teams), position the edge of the airfoil platform on a scale approximately 11” (the length of a standard sheet of copy paper) from the front edge of the fan (the length of a piece of letter size paper. The best airflow from the fan is often best when not aligned with the center of the fan. An example setup is shown in Figure 7. Figure 7 One of the key parameters to be measured is the angle of attack. While the angle of attack is defined as the angle between the chord and the airflow. Figure 8 shows a protractor measuring

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