Wind Tunnel Aerodynamics Testing

Overview

This was an analysis of the aerodynamic characteristics of the Cessna 210 model using wind tunnel experimentation and theoretical principles. The wind tunnel tests, conducted under controlled conditions, examined the aircraft's performance at various angles of attack. Theoretical considerations, including clean aircraft conditions and steady airflow, guided the experimental setup. Results highlight the aircraft's lift, drag, and pitching moment behaviors. This contributed to insights of the Cessna 210's aerodynamics, aiding in aircraft design and performance optimization. 

Process

The Cessna 210 model used for the experiment was tested in an open circuit subsonic wind tunnel. The tunnel allows a scale model of the aircraft to be tested at different wind speeds that mimic the aircraft's actual speed within the atmosphere. Data can then be retrieved from the tunnel about the aircraft and discussed further below. The tunnel has a 21x30 inch test section that can reach speeds of up to 120 mph or 176 ft/s. The angles of attack at which the aircraft was tested are as follows: -5°, 0°, 5°, 10°, 15°, and 20°. During the wind tunnel test, the aircraft was subjected to a direct wind with a constant speed of 40 mph or 58.89 ft/s. 

Results

The Cessna model’s angle of attack was increased in 5-degree increments, starting at -5 degrees. The air temperature, density, and velocity as well as aircraft lift, drag, and pitching moment were all recorded at each angle. The results are displayed in the table below.

Analysis

To analyze this data, the coefficients of lift, drag, and pitching moment must first be calculated. These are determined algebraically through the lift, drag, and pitching moment equations while ensuring that units match correctly as follows.

It is now possible to calculate the coefficients of lift, drag and pitching moment for each angle of attack. This is summarized in the table below. 

Conclusion

 Scaled model testing provides one with a reasonable glimpse into the performance of a full-scale aircraft, while additionally being very affordable. Minute changes can be made to the model to see the observed aerodynamic effects, which can influence decision-making when it comes to the manufacturing of an aircraft. Wind tunnel testing is not without certain drawbacks and considerations, however. Slight defects in the tunnel can lead to undesirable flow conditions around the scaled model, potentially leading to unusable data.

The data contained many suspect pieces of data that led to the questioning of the entire dataset. These problematic entries could have been the result of any number of problems, from incorrect settings in the tunnel’s controlling software up to an including the controlling computer restarting in the middle of testing due to an unfortunately timed Windows update. To combat this issue in the future, the team would collect data at more angles of attack and would repeat this collection multiple times to even out errors. More data allows ease in identifying issues in the data and making plans to correct them. Furthermore, testing the scaled model at different airspeeds would be an excellent idea, as this would allow the team to observe how aerodynamic properties change with speed. Afterwards, the team could compare the model’s data from the wind tunnel to actual aerodynamic data from the full-scale Cessna 210.

References 

1. Advanced Airplane Analysis 3.12.  DAR Corporation. 

2. Selig, Michael, “UIUC Airfoil Data Site.” University of Illinois at Urbana-Champaign, [http://www.ae.uiuc.edu/m-selig/ads/coord_database.html]. 

3. Jane's Information Group. Jane's Aircraft Recognition Guide. 4th ed., Collins, 2005. 

4. Aircraft Owners and Pilots Association (AOPA). “Cessna 210.” Aircraft Fact Sheets. Accessed March 18, 2024. URL: https://www.aopa.org/go-fly/aircraft-andownership/aircraftfactsheets/cessna210#:~:text=The%20210%20is%20an%20all,permitted%20in%20normal%20c ategory%20airplanes. 

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