Investigation of payload fill effect on a large launch vehicle fairing

For the problem of local SPL (Sound Pressure Level) increasing caused by the payload filled in the launch vehicle fairing (fill effect problem), the equivalent models of the fairing and payloads are established using the sandwich plate theory. The interior acoustic characteristic of the fairing is simulated through FE-BEM (Finite Element-Boundary Element Method) and SEA (Statistical Energy Analysis) method, and then the influence of the payloads with different volume ratio and different shape on the fill effects is investigated. Besides, the mechanism and distribution characteristic of fill effect are studied from the point of view of mode frequency shift. The simulation and test results show that fill effect is associated with acoustic mode frequency shift caused by sound-vibration coupling. The shift ratio is greater at low frequencies than at high frequencies, which makes the fill effect more obvious. In that the payload fill factor can influence the shift ratio, fill effect will increase as the fill factor increases. Numerical computation based on FE-BEM and SEA provides an effective way to predict the payload fill effect.