Executive summaries of Action Groups of Group of Responsables in Aerodynamics

• AD(AG37) ‘Pressure sensitive paint, phase II’

Quantitative pressure distribution measurements on a complete model surface - mainly in the wind tunnel – obtained by an optical system (PSP) without disturbances like conventional probes gives a wide additional knowledge about aerodynamic understanding.

Also transition, loads and forces as well as attachments and re-attachments can be measured. The underlying objective is to reduce the number of the models to be manufactured (one equipped with balances, the other with pressure taps, etc.) and therefore the design costs as well as wind tunnel occupation time.

All members of AD(AG37) possess now their own PSP system and have developed more or less their own hard- and software. So still the future goals since 2003 are mainly the same, but accuracy is the most important point since force and moment measurement using PSP is possible.

The main activities have been defined and work packages created. The special items of very high interest to more or less experienced researchers created a wide basis of knowledge. In detail, these subtasks are:

· Light sources;

· Paint characterisation;

· Roughness and waviness;

· Response time measurements and paint for unsteady application;

· Camera types, properties and problems;

· Pixel by pixel correction;

· Filter leakage;

· Calibration in wind tunnel;

· Productivity.

The decision to create practical work packages was an eminent step for the co-operative work between all the members. Tests were realized by different members in different countries.

In detail, the following actions took place:

1. DNW organized PSP measurements in the HST using different evaluation software and image processing systems. The following comparison of the PSP results guided developers to new strategies and ideas. An active exchange of information and practical help was the result;

2. DLR invited INTA for filter leakage tests in their laboratories because the measurement techniques were not available at INTA. All filters from the different members were collected and investigated. The result is a wide new knowledge about the actually used fluorescence filters and their position in relation to the location of the camera CCD-chip. INTA developed a software package for filter leakage effects in dependence on different excitation wavelengths. This package is available to all members;

3. CIRA performed measurements in co-operation with Emmen (Switzerland) and tested new paints and software. The results and ideas were presented in a GARTEUR meeting in May 2004 in Göttingen;

4. DLR continued camera investigation and illumination distribution and was mainly active with FOI to solve illumination problems;

Figure 2 Illumination of the test-section of the FOI T1500 wind tunnel with 20 000 blue LEDs for PSP measurements purposes

5. SAAB was very active with Airbus-Bremen into roughness and waviness investigation. The co-operative work was excellently shared between them since Airbus was able to measure the physical parameters using new measurement techniques and SAAB calculated and predicted theoretically results;

Measurement direction:

Figure 3 Measurement of the roughness profile

6. ONERA continued unsteady PSP tests in the laboratory and developed a test generator mainly for sinus signal stimulation. Results from DLR’s shock tube tests were compared and the effect of high/low amplitude influence from the different constructions/facilities have been discussed to determine future strategies.

Figure 4 360° PSP measurement in the DNW-HST wind tunnel

A quite new aspect for civil and military application is the possibility to be able to measure forces and moments through the application of PSP. Therefore, after DLR’s basic tests on models from EADS in the HST wind tunnel, additional tests were performed to obtain highest accuracy of the performance with relation to the camera position and to the extent of zooming in on a part of the aircraft – such as a horizontal tail, flaps, etc.

High-accuracy results could be shown using a zoom in function on a component of an aircraft. The difference between PSP-based performance and balance-measured performance amounts to only 3-5 per cent.

In conclusion, it can be stated that a large exchange of knowledge has been achieved. It has been decided by all members to continue the relation generated over the last 5-6 years. Further co-operative research was discussed as continuation of the GARTEUR activities. Therefore, a PSP-NET like the already existing PIV-NET will be pursued in future. The proposal for PSP-NET is already prepared and submitted to all members of the group and also to universities as well as industry. It will be filed in 2005 to the last call of the 6th Framework Programme of the EC.

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