ANALYSIS OF THE EFFECTS OF SAIL AND CASING PLACEMENT ON THE HYDRODYNAMIC RESISTANCE OF A U209 SUBMARINE UNDER SUBMERGED CONDITIONS AT VARIOUS SPEEDS USING CFD English Language

Abstract

This study investigates the effects of casing installation and longitudinal sail position on the hydrodynamic resistance of a fully submerged U209/1300 submarine. Eight configurations were numerically evaluated at speeds of 5, 10, and 15 knots using the Reynolds-averaged Navier–Stokes equations coupled with the shear stress transport turbulence model. The numerical framework was validated against experimental data for the DARPA SUBOFF model, showing a difference of 1.4% in the drag coefficient. The results indicate that the casing increased the total resistance by an average of 8.7% compared with the bare-hull configuration. The combined installation of the sail and casing increased the total resistance by 18.6% to 21.6%. Among the investigated longitudinal positions, the standard sail position consistently produced the lowest resistance, both with and without the casing. The differences in resistance were attributed to variations in wetted surface area, pressure distribution, and hydrodynamic interactions among the hull, sail, and casing. These findings highlight the importance of sail positioning and casing configuration in minimizing the hydrodynamic resistance of fully submerged submarines.