Recommendations for Computational-Fluid-Dynamics Procedures for Predicting Abrupt Wing Stall

Abstract

This paper summarizes the lessons learned from the computational-fluid-dynamics effort of the joint NASA/Navy/Air Force Abrupt Wing Stall Program, discusses the results, and makes recommendations for approaches to be used in future aircraft programs to identify uncommanded lateral characteristics early in the design phase of an aircraft development program. The discussion also suggests procedures and figures of merit for use in predicting and quantifying rapid and severe wing-stall tendencies and vulnerabilities of the proposed designs. Topics addressed include critical parameters that can be used to identify uncommanded lateral activity in the transonic flow regime and the geometric parameters that were the primary contributors to the adverse lateral activity observed on preproduction F/A-18E/F aircraft. In addition, differences in steady-state and averaged time-accurate computational solutions for the F/A-18E in the abrupt-wing-stall region of interest are analyzed and compared with existing unsteady experimental data to determine the utility and accuracy of the unsteady approach. Lastly, proposed computational figures of merit are critically evaluated as indicators of possible abrupt separation tendencies, and screening procedures for the identification of those tendencies are suggested.