An inverse aero design method is used by NLR to obtain a pressure distribution representative of the pressure distribution of a CROR front blade section at 87.5% of blade span in take-off condition, which is sufficiently thick to install the requested pressure sensors in the near trailing edge region and also strong enough to be used as a 2D airfoil section in DNW-TWG wind tunnel.
NLR has performed the structural design (engineering) and manufacture of two 2D wind tunnel models:
1. The CROR like 2D airfoil based on the inverse design
2. The baseline airfoil, i.e. the ValeoCD as requested by the topic manager at T0.
The structural design and manufacturing included the integration of unsteady sensors selected, the static pressure orifices (50 by profile) and the installation of an additional accelerometer sensor in the airfoils. The most optimal type and layout of the unsteady pressure sensors was determined for the unsteady pressure measurements. The use of interchangeable instrumentation pads on both models was considered in order to reduce sensor procurement costs for the two instrumented 2D models, but proved infeasible. Flush mounted sensors were selected.
The selected DNW-TWG wind tunnel allowed profiles with a chord length of up to 0.4 m to be tested in the requested alpha, Mach and Reynolds range, without significant side wall effects. This larger chord length of 0.40 m (compared to the target chord length of 0.3 m) was preferred, because it facilitates the installation of closely packed unsteady pressure sensors in the trailing edge region.
Details on mounting of the model in DNW-TWG, strength requirements (safety factors) and instrumentation cable routing from the model to the data acquisition systems and possibility to install an inflow-microphone near the profile trailing edge were discussed with the WT operator. Efficient solutions were sought to mount and dismount the models, in order to allow an easy model exchange. Solutions for optical access to the wind tunnel with the PIV camera’s, the infrared camera and laser light sheet as well as the PIV flow seeding were found.
The WT operator DNW-TWG executed the tests in accordance with the test matrix of the Test Plan in five productive testing days. During the week before the actual test preparations were performed, e.g. the wind tunnel model was shipped to the wind tunnel, the PIV, IR and pressure measurements were setup and the PIV/IR foil and tripping were applied to the models. This resulted in optimal use of wind tunnel time during the tests themselves.
At the end of the project, NLR will collect and store all aerodynamic and aero-acoustic test data together. Two copies of the database were delivered to the Topic Manager, i.e. one at Airbus Lyon and one at Airbus Bremen. NLR will also preserve it to enable further analysis when needed. Both original and processed data will be stored to allow re-processing of original data if needed.
