Natural Laminar Flow Optimization of Transonic Nacelle Based on Differential Evolution Algorithm

Abstract

Natural laminar flow (NLF) design is widely used to reduce skin friction drag to improve aircraft aerodynamic performance. In this paper, a differential evolution (DE) algorithm was applied to a NLF-designed transonic nacelle. The class shape transformation (CST) method was tested in terms of accuracy before being adopted as the geometry parameterization method that describes three longitudinal profiles constructing the nacelle surface. The purpose of this optimization is to extend the laminar length of each longitudinal profile of the nacelle while maintaining pressure drag under a preset limit. A high-fidelity computational fluid dynamics (CFD) solver was used for accurate laminar/turbulence transition prediction. It was tested in terms of pressure distribution and particularly laminar transition prediction. The whole process was executed via a Python version 3 script automatically. The laminar length was extended on longitudinal profiles after DE operation. The laminar area of the optimized nacelle surface was increased by 16.64% and total drag coefficient was decreased by 11.6 counts.