Initial Assessment of a CFD Application for Predicting Jet Fighter Aircraft Cavity Bay Acoustics for Subsonic and Supersonic Aircraft States

Abstract

In an effort to reduce cost associated with flight test and certification of new weapon systems/stores for the F-22 Advanced Tactical fighter, Lockheed Martin Aeronautics has conducted a study to assess the capability of several commercial computational fluid dynamics (CFD) codes to predict cavity bay acoustics. Initially a literature survey was conducted to identify commercial, in-house, and research computer codes which have been or are presently being used to simulate cavity flows and the resultant acoustic environment. Four CFD/CAA codes were down-selected for evaluation. Code evaluations were based on comparison of predicted results with experimental data. For this purpose, four wind tunnel test cases based on the V10 1/15-scale F-22 main weapon bay (MWB) model were selected. The cases selected include both subsonic and supersonic test conditions, with both an empty MWB configuration and an inboard stowed AIM-120 configuration. This paper discusses in detail the process, application, and results using the Falcon v4 CFD code which was determined to be the best performer in predicting both subsonic and supersonic TOBSPL frequencies above 100 Hz. Results indicate Falcon v4 predictions compare very favorably for the subsonic test conditions and configurations analyzed, and tends to slightly over predict the response for the supersonic test conditions at some locations. The results of this study have proved favorable enough that correlation using a full scale CFD model with actual F-22 flight test data is proceeding.

The effect of angle of attack on the aeroacoustic environment within the weapons bay of a generic UCAV

“…Despite this knowledge, it is difficult to extrapolate simple experimental results to the design of weapons bays installed in real-life combat aircraft because the bays are generally not rectangular and the surrounding environment is complex. Some work has been published in the open literature concerning the analysis of existing manned combat aircraft designs [9][10][11] and unmanned combat air vehicle (UCAV) platforms with a weapons bay installed [12][13][14]. Further studies have addressed some of the geometric features of current designs, such as bay doors, indented leading and trailing edges, and contoured surfaces in front of the cavity [15][16][17].…”

Simulating the Response of External Stores on Aircraft Using Linear and Nonlinear Vibroacoustics

“…The first study was to determine if the acoustic mesh would provide a diffuse field with no structure inside the mesh. The mesh was scaled to 1 10 th the original size. A 150 dB magnitude input was provided that ranged from 40 to 315 Hz.…”

“…The first method uses a computational fluid dynamics (CFD) code coupled to a computational structural dynamics (CSD) code. 1,2 This is computationally intensive, and is being reserved for internal captive carry (inside a bomb bay), where the flow field is complex, highly nonlinear, and unsteady. It is possible to capture the unsteady pressure loading beneath a turbulent boundary layer of a free store using statistical models which account for the magnitude, temporal, and spatial correlation of large coherent structures within the boundary layer.…”