Multidisciplinary analysis of aero-propulsive coupling for the OWN concept

The Over Wing Nacelle (OWN) concept enables the installation of turbofans with high bypass ratios for improved efficiency in commercial transport vehicles, in addition to offering other advantages in the form of (i) mitigation of jet noise, (ii) foreign object damage avoidance and (iii) jet-powered lift. While these benefits can be offset by the large transonic drag rise, aerodynamic shape optimization of the wing and nacelle outer mold lines can help realize the full aerodynamic potential of the OWN concept. However, if coupling between the airframe aerodynamics and the propulsion system is strong, multidisciplinary optimization may need to be conducted. In this paper, the aerodynamics-propulsion coupling in the OWN concept is studied. A high fidelity Reynolds Averaged Navier Stokes (RANS) model along with a low fidelity engine thermodynamic cycle analysis model are used to represent the aerodynamic and propulsion systems respectively. The necessary coupling variables are identified and the coupled system is solved for disciplinary feasibility using the Fixed Point Iteration technique. The Common Research Model (CRM) wing and nacelle are used as the baseline geometry to carry out the study. The study reveals that for the OWN concept, aerodynamics-propulsion coupling is not significant enough to warrant multi-disciplinary shape optimization. While airframe aerodynamics has a strong effect on the propulsion system, the reverse interaction is weaker.