Optimization of aerodynamics plays an important role in the development process of aircraft: Doing so, it is possible to increase efficiency and reduce emissions. Because of a remaining lack of knowledge in terms of fluid physics/ air flow mechanisms, it is necessary to test and validate new ideas in a wind tunnel.
The European Transonic Wind Tunnel (ETW) is besides the NTF (NASA, Langley) the only wind tunnel in the world which can correctly simulate the air flow of transport aircraft: using the correct Mach- and Reynolds numbers, temperatures of -170 degree Celsius and pressures of 4,5 bar are possible.
It is the objective to implement the optical flow measurement method of the Particle Image Velocimetry (PIV) into the European transonic wind tunnel (ETW). This will be the first opportunity to carry out quantitative analysis on air flow for transport aircraft in a wind tunnel under realistic conditions: It is possible to simulate real Mach- and Reynolds numbers at the same time. Therefore, some developments in the PIV-measurement methods and the ETW-settings are necessary.
At the end of the project, a demonstration experiment is planned to prove the results.
In the first two years, the project focused on the development of the PIV-measurement method: there was a need for some adaptation for the use in the ETW wind tunnel. Further, the ETW itself had to undergo some adjustments. The project was organized with several work packages:
- WP1: Generation and supply of particles
- WP2: Laser pulse in the ETW
- WP3: Light sheet optics
- WP4: Camera recording
- WP5: Simulate the construction for the optical components at the ETW
- WP6: Software for data collection
In the third year, the applicability was proved:
- WP7: PIV-measurements at the ETW
- WP8: Evaluation of the results
The usage of the PIV-measurement method under the extreme conditions in the ETW wind tunnel required some adjustments. Within this project, it was possible to solve these problems and achieve the following:
- Creation of flow tracers in the ETW
- Powerful laser beam to the test-section
- Placement of optical components in a cryogenic environment
- Compensation of optical and mechanical effects caused by temperature and air pressure
- Systems working reliably avoiding extra costs
- Automation for industrial applications
Findings of the study are published by a final report (German only), which is available online via the Technical Information Library (TIB) of the Hannover University: