...... Now incorporating Computational Aerodynamics...
Free subscription
- Home
- Advertise
- Register for free subscription
- Supplier Spotlight
- Wind Tunnel e-News 2010
- Global Wind Tunnel Symposium 2010
- GWTS 2010 - Program Abstracts and Bios
- Contact Us
- Readership Circulation
- Industry-wide feedback......
- Information Request
SESSION 6 - Evaluation and Control of Wind Tunnel Measurement Processes
Dr Michael Hemsch, Aerospace Technologist
SESSION 6 - NASA Langley
In 1998-2000, NASA Langley adopted a new framework for statistical evaluation and control of its wind tunnel measurement processes over time. The framework was implemented in five major tunnels at Langley:
(1) the National Transonic Facility,
(2) the Unitary Plan Wind Tunnel,
(3) the 14-ft x 22-ft Subsonic Wind Tunnel, the
(4) Transonic Dynamics Tunnel and
(5) the 16-Foot Transonic Tunnel (now closed).
The methodology is adapted from elements of the Measurement Assurance Plans developed by the National Bureau of Standards (now the National Institute of Standards and Technology) for standards and calibration laboratories. The methodology is based on the notions of statistical quality control (SQC) from manufacturing and metrology together with check standard testing. The results over time of the check standard repeat-run sets are analyzed using the statistical control chart methods of Walter A. Shewhart long familiar to the SQC community.
Each tunnel’s check standards typically consist of a suitable wind tunnel model and a calibration probe, among others. Using control charts, the output from the check standards is monitored for back-to-back repeatability, within-test repeatability and across-test repeatability.
Our experience suggests that back-to-back repeatability is essentially a function of the instrument chosen and the test section used. However, the subgroup-to-subgroup variation, i.e. within-test and across-test, can include significant effects of test personnel decisions and facility activities, making it important to monitor such variations.
In the presentation, the details of the SQC methods used in the NASA Langley wind tunnels are described and force balance and calibration probe control charts obtained over the past decade are presented. In addition, SQC methods and control charts results are presented for various other measurement processes as well. Those processes include test section flow angularity measurements, instrument calibration, and tracking of balance zeros during a test.
|
Dr Michael Hemsch, Aerospace Technologist |
Dr. Michael Hemsch – Aero Uncertainty Lead at NASA Langley Research Center, USA, since 1998. Currently, Uncertainty Lead for the aero databases generated at Langley for the Constellation Ares I project. This job entails determining and quantifying all significant error sources for the input to and construction of the databases. The inputs consist of results from various wind tunnels as well as output from simulations using computational fluid mechanics codes.
Dr. Hemsch has been lead or co¬-author for over 80 publications. He was co¬-editor of the AIAA Progress Series books entitled “Tactical Missile Aerodynamics”. He was Technical Chairman for the 1987 AIAA Atmospheric Flight Mechanics Conference and he supported the first three AIAA Drag Prediction Workshops with statistical analyses. Dr. Hemsch has been active in wind tunnel testing for 36 years having participated in tests in 12 different low-speed, subsonic, transonic and supersonic wind tunnels at NASA’s Langley, Ames and Glenn Research Centers as well as AEDC. Dr. Hemsch received his bachelor’s degree in mechanical engineering in 1962 from Santa Clara University and his Masters and Ph.D. degrees from Stanford University in 1966 and 1971 respectively. |
