Numerical optimization of transonic natural laminar flow nacelles

Natural laminar flow nacelle is a promising technology for drag reduction. In this paper,an optimization platform is established for the design of transonic axisymmetric and threedimensional natural laminar flow nacelles for large civil aircraft. The platform adopts the class/shape transformation method for geometric parameterization, a four-equation transition model for transition prediction, and the differential evolution algorithm combined with the radial basis function surrogate model as the...

Numerical optimization of transonic natural laminar flow nacelles

Natural laminar flow nacelle is a promising technology for drag reduction. In this paper, an optimization platform is established for the design of transonic axisymmetric and three-dimensional natural laminar flow nacelles for large civil aircraft. The platform adopts the class/shape transformation method for geometric parameterization, a four-equation transition model for transition prediction, and the differential evolution algorithm combined with the radial basis function surrogate model as the optimization algorithm. The optimized axisymmetric nacelle demonstrates approximately 31% chord length of laminar flow, with the drag reduction of 13.3%. The influence of the Reynolds number and inlet mass flow rate on the optimization result is also investigated. The axis-symmetric nacelle optimization method is further used for the section profile design of a non-axisymmetric nacelle. An equivalent method is used to simulate the different local flow angles at different sections in the circumferential direction of the non-axisymmetric nacelle by using different inlet mass flow rates of the axisymmetric nacelle. The optimized natural laminar flow nacelle maintains over 30% chord length of laminar flow with robustness to the change of the freestream angle of attack. The total drag of the non-axisymmetric nacelle is reduced by 5.4% under cruise conditions.