A high fidelity CFD methodology has been developed to accurately predict the flow around a complex geometry modeling UHBR powerplant-equipped aircraft, for low speed/moderate-to-high incidence flight conditions. In this context, the original geometry is the DLR F15 UHBR powerplant-equipped model. Flow incidences were varied from -4° to +24°, with a chord-based Reynolds number equal to 21.5M and a Mach number Ma=0.23.
So far, the project members have
• Identified the unsteadiness of the flow in regard to the most effective excitation frequency of the piezoelectric-based actuators, considering various flow control parameters (actuators position, momentum, amplitude modulation, frequency)
• Performed a large set of unsteady RANS computations on the DLR F15 geometry, first with/without pulsed jet-based flow forcing, (i.e. 169 ZNMF SJA) using predefined locations and actuation parameters.
• Developed an innovative body force source term-based ROM approach to model ZNMF pulsed-jet based actuators, that they have applied to 2 well-referenced test cases: the flat plate and the NASA CFDVAL2004 workshop bump cases, comparison with 3 other strategies, then to the Fraunhofer actuator implemented on the baseline. This approach has been fully validated, both with a steady and unsteady approach
• Complemented the study with a comprehensive analysis of 2 alternative geometries, referred to as variant 1 and variant 2 to secure the profitability of the project. Variant 2 reveals to be the most effective configuration in restoring a relevant flow in the region of the UHBR powerplant/pylon/wing interaction, similar to the one referenced in the few available previous studies.
Based on this study, geometry "variant 2" is now considered as the baseline geometry for the upcoming multi-parametric flow control optimization study.
Besides, control-off, unsteady simulations have revealed characteristic frequencies one order of magnitude lower than the ones required to produce significant pulsed jet velocities using the ZNMF actuators. The unsteady approach is thus not appropriate in the context of a multi-parametric optimization approach for obvious cost reasons. The proposed strategy is to apply the optimization process completed on the basis of a steady approach, while a reverse engineering approach will determine maximum pulsed velocity for a given frequency of the ZNMF Fraunhöfer SJA-based pulsed jets.
The project members have then conducted research to optimize both the location on the wing, the momentum, the blowing angles of a large series of ZNMF actuators, and finally, the blowing frequency, to mitigate the flow separation induced by the UHBR powerplant/wing integration effects.
A noticeable improvement of the flow has been achieved, with up to 87% reduction of the flow separation induced by the UHBR powerplant/wing integration effects.
