The proposal tackled the CfP JTI-CS-2012-1-GRA-02-019. Within the project a Wind-Tunnel-Model was designed, built and tested that is capable of being tested with two main purposes:
- access the extend of laminarity on the wing;
- evaluate the performance of LC&A system in the trailing edge of the wing.
In order to do this, the project tackled different points:
- a model design was performed that creates a wind-tunnel model with an elastic behaviour comparable to the full-scale wing. This model was as big as possible, although fulfilling all specifications in terms of wind-tunnel restrictions (size, maximum force) in order to allow a hig Reynolds-Number and therefore allow to assess the laminar extend on the wing during the tests in a way that the results are comparable to the full-scale tests.
- a first possible LC&A solution which is input to the project was evaluated and optimised and compared with a solution, that was newly designed and optimised LC&A within the project. The best solution was scaled down to model scale and implemented into the model.
Within the test's step/ gaps and contaminates were introduced to the model in order to evaluate the stability of the laminar behaviour of the wing with respect to this parameters. In the second test-phase the LC&A devices were used in order to modify the load-distribution on the wing. Before testing the model-wing a ground-vibration test was performed in order to show that the model can be operated safely in the wind-tunnel.
The project tackled the CfP JTI-CS-2012-1-GRA-02-019. Within the project a Wind-Tunnel-Model was designed, built and tested that is capable of being tested with two main purposes:
- Assess the extent of laminarity on the wing
- Evaluate the performance of LC&A system in the trailing edge of the wing
The geometry of the full-size laminar flow wing geometry, the scaled wind tunnel model wing was optimised to delay the onset of Laminar - Turbulent transition for a range of angles of attack, including the effects of aeroelastic deformations. CFD computations were undertaken using Euler, full Navier-Stokes and stability analysis. Further work then considered the optimisation of trailing-edge ailerons positioned along the entire semi-span of the wing to reduce the drag at off-design conditions.
A statically aeroelastic scaled structural model had to be designed in order to ensure that the deflections (twist, bending) were representative in the wind tunnel tests. This objective proved to be challenging as the stiffness of the scaled wing was difficult to achieve, particularly as it is impossible to simply shrink all of the dimensions; in particular the skin thicknesses are constrained by what is possible to manufacture. There were also considerable challenges provided by the requirements to move the control surfaces and also to enable all of the required testing instrumentation. A further constraint was the surface roughness.
Validation of the structural modelling was provided by a series of static and dynamic tests applied to the wing in a vertical configuration. Static loads were applied via a specially designed collar at the top of the model and the deflections measured at 15 positions. From these tests it was possible to determine the bending and torsional stiffness and to update the Finite Element model. Following to these tests a vibration test was performed to measure the natural frequencies, damping ratios and mode shapes of the wing.
Finally, a wind tunnel test campaign was performed in the S1 ONERA tunnel at Modane. The test was used to demonstrate the laminarity extent for different cruise and off-design conditions, to assess the performance of the trailing edge loads alleviation devices, and to evaluate the effectiveness of the modelling. Global force and moments, Infra-Red, model deformation and accelerometer measurements were made.