Use of CFD in Developing the JSF F-35 Outer Mold Lines

Abstract

The Air Force, Navy, and Marine variants of the Joint Strike Fighter (JSF) must each meet specified Key Performance Parameters (KPPs) and Performance Specification (SPEC) requirements. A significant number of these requirements pertain to Mission Performance, which are driven by the flight principles of thrust, weight, lift, and drag. To ensure high quality aerodynamic performance data, the JSF Program has placed emphasis on gathering these data using high-fidelity, large-scale wind tunnel models. To maximize the efficiency of wind tunnel test schedules, the Program has been committed to performing extensive Computational Fluid Dynamic (CFD) analyses to pre-screen potential Outer Mold Line (OML) changes prior to testing. As with all aircraft programs, increased design maturity resulted in increased drag levels and decreased performance. To mitigate these issues and maintain adequate performance margins, CFD was used to assist in the redesign of the aircraft OML. The goal of the CFD analyses was to decrease trimmed drag, and in some cases added internal volume, which improved routing and increased fuel capacity. This resulted in highly-optimized, well-balanced fighter designs that meet or exceed their performance requirements. This paper describes the CFD-based design process and techniques used to predict drag increments and validate them with wind tunnel tests for use in aircraft performance predictions. CFD analyses on the JSF Program have shown that it can be used as a viable tool in predicting drag increments.