Community Research and Development Information Service - CORDIS

Laminar flow technology

The European laminar flow investigation (ELFIN) project focuses on laminar flow research for aircraft wing and nacelle applications. ELFIN research focuses on basic flow investigation. Large scale wind tunnel tests with hybrid laminar flow (HLF) wings and nacelles and flight tests are performed to generate experimental data for the validation of numerical stability codes.

The wind tunnel tests have given a first insight into hybrid laminar flow stability. They have shown the potential of this technology.

Most important for the design of a laminar wing is an accurate transition prediction of the flow. N-factor envelopes calculated from wind tunnel test data were compared with flight test N-factors. Only natural laminar flow (NLF) data are considered. This comparison shows that there is no generally valid calibration procedure for transition prediction based on the N-factor method.

A flight test was performed to test the limits of NLF. After a first set of data was accumulated it was recommended that the surface quality of the test glove should be improved. The glove surface was refinished and flights continued. In total 15 flight test hours were logged producing 2 complete sets of data marking the limits of NLF.

Numerical work is completely related to laminar flow with heavy emphasis on stability analysis for transition prediction. Boundary layer data generated from surface pressure distributions supply the input for stability calculations.
Existing boundary layer codes were modified and curvature terms were included in the stability codes. For the considered laminar profile the N-factor calculated is reduced by approximately 30%. This result makes the comparison of results more reliable.

To ease design engineers work a 2-dimensional database method was established. This database is not just a set of experimental data but is a set of precalculated stability data.

Reported by

Daimler-Benz Aerospace Airbus
21111 Hamburg
Germany
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