An investigation of free surface effects on drag and lift coefficients of an autonomous underwater vehicle (AUV) using computational and experimental fluid dynamics methods

In the present paper, in order to investigate the effect of free surface on drag and lift coefficients of an Autonomous Underwater vehicle,11 hase flow Reynolds Averaged Navier–Stokes (RANS) equations were solved using computational fluid dynamics. The numerical results were compared with those obtained from both numerical single phase flow simulations and the experiments conducted in the towing tank of the Subsea R&D Center at Isfahan University of Technology, using a 1:1 scale model of AUV developed in this center. The study was conducted at various submergence depths ranging from 0.87 to 5.22 of the AUV diameter and at the speeds of 1.5 and 2.5 m/s (corresponding to Reynolds numbers of 1.9 and 3.17 million, respectively). The variation of drag and lift coefficients of the AUV with the submergence depth were shown to be very sensitive to the AUV speed.