NUMERICAL STUDY ON CABIN INTERIOR NOISE INDUCED BY MUZZLE BLAST WAVES FROM AN AIRCRAFT CANNON FIRING

The muzzle gas blast wave generated during the process of the aircraft cannon firing can induce severe vibration or noise fatigue problems in other components of the aircraft in the vicinity of the structure within or without the gun bay. However, effective numerical simulations or studies on aircraft gun firing process are remain relatively rare of reports. In the present study, the basic approach of a ground firing test for an aircraft gun bay is presented in the beginning, and the vibration response measurement values at different positions of the test section are obtained. Subsequently, based on the equivalent conversion concept between the hot and cold jets for the gas blast wave, the similarity criterion of the conversion is described and the calculation method for the relevant parameters is provided. On this basis, a detailed CFD (Computational Fluid Dynamics) simulation analysis is carried out. After effectively obtaining the distribution characteristics of the blast wave flow field, a computational model of the noise environment inside the gun bay is established, and a hybrid simulation and analysis method combining the structural finite element method and the acoustic boundary element method is proposed. The noise response characteristics at typical measurement points are calculated, and the impulsive dynamic loads imposed on the bay structure during gun firing are compared with the experimental results. The results show that, compared with the experimental data, the overall sound pressure level at the maximum-noise point of the blast wave obtained from the simulation exhibits an error within 1 dB, satisfying the accuracy requirement for engineering simulation. This paper analyzes the influence of the blast wave on the noise environment inside the gun bay, and the relevant methods and conclusions can provide an effective numerical analysis approach for the launch dynamics design and simulation of airborne gun systems and airframe structures.