In order to reduce fuel consumption and thus environmental pollution of modern jet engines either the internal flow has to be improved or the weight has to be decreased by reduction of stage or blade numbers. Both ways demand the massive use of computational fluid dynamics (CFD). The models used in the simulation have to be evaluated by comparison with experimental data. Although CFD codes are well established there are still uncertainties in the modeling of turbulence and especially of the boundary layer processes. The change of the boundary layer flow from laminar to turbulent and vice versa cannot be predicted reliably, although it can have a large impact on friction and thus efficiency. Especially the understanding and modeling of reverse flow transition, the so-called relaminarization, which can be found at compressor and turbine blades, is poor. Therefore the project RELAM has set the goal to investigate relaminarization, but also transition, at flow conditions relevant for jet engines. Since there are only few data for relaminarization at higher velocities, at first test cases for an experimental investigation shall be found and designed. They shall be investigated with the innovative method of laser vibrometry, which allows the frequency resolved recording of density fluctuations and thus of transition. The experimental data will be used for the determination of strengths and weaknesses of existing transition models currently used in commercial CFD codes. Based on the results new approaches for the prediction of relaminarization will be developed and validated. They should allow the design of improved and thus more environmentally friendly jet engines in the future.
|Effective start/end date||1/04/14 → 31/03/17|
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