Abstract: Autonomous underwater vehicles (AUV) depend on acoustic instruments to realize navigation, locating and orientation, task operation. Acoustic communication modem (ACM) is the only data path to ensure the normal underwater operation of AUV in deepwater area. Interference of the vortex noise on the signal of the ACM cannot be ignored. Aiming to reduce the interference of vortex noise on the signal of ACM, the installation structure of the ACM is designed. Based on the structure of the ACM mounted on the AUV, a geometric model, i.e. the cavity–appendage composite structure, is extracted. The large eddy simulation (LES) –Lighthill equivalent source method is used to investigate the unsteady flow mechanism and vortex noise of the composite structure. Factors influencing the vortex noise generated by the composite structure are analyzed. Aiming to decrease the vortex noise induced by the composite structure, parameters of the composite structure are optimized by designing an orthogonal test with four factors three levels. Results show that effect of velocity of the AUV on the vortex noise induced by the composite structure is less significant than that of parameters of the composite structure. For the three structure factors, the influence of the height–depth ratio on the vortex noise is most significant, followed by the diameter–diameter ratio, and finally the depth–diameter ratio. The present research provides scientific guidance for designing the installation structure for acoustic sensors mounted on AUVs.

Key words: autonomous underwater vehicle, cavity–appendage composite structure, large eddy simulation–Lighthill equivalent source method, orthogonal test, vortex noise