Development and validation of a simple approach to model aerodynamic loads on a military jet intake structure

摘要

A stress analysis was carried out on the F-111 FS496 former and surrounding intake structure, considering both the regular flight loads and the engine intake pressure loads. The original Internal Load Model (ILM) Finite Element (FE) Model was modified. A stress analysis used the updated ILM and a Fine Grid FS 496 model. In order to consider the intake pressure loads, a Computational Fluid Dynamics (CFD) model has been created to model the pressure loads along the engine intake, and the CFD analysis was carried out. An "envelope" approach has also been developed to estimate the pressure loads. This simplified approach assumes that the distribution of the air pressure along the wall of the intake structure is within an envelope. The contribution from the aerodynamic intake loading to the stress in the critical region of the FS496 former is significant, and was found to be greater than that due to regular flight loading. Previous stress analyses for the region ignored this intake pressure loading. The stress analysis using the CFD data was very similar to that using the simplified envelope method, thereby validating the simplified method. This will enable such problems in the future to be nodelled without the need for expensive and time consuming CFD.