Ocean Systems Engineering, Vol. 10, No. 3 (2020) 000-000 DOI: https:// doi.org/10.12989/ose.2020.10.3.000 000 Copyright © 2020 Techno-Press, Ltd. http://www.techno-press.org/?journal=ose&subpage=7 ISSN: 2093-6702 (Print), 2093-677X (Online) Numerical investigation of the effect of the location of stern planes on submarine wake flow Shokrallah M. Beigi 1 , Alireza Shateri *1 and Mojtaba D. Manshadi 2b 1 Department of Mechanical Engineering, Engineering Faculty of Shahrekord University, Shahrekord, Iran 2 Department of Mechanical Engineering, Malek Ashtar University, Esfahan, Iran (Received January 15, 2020, Revised March 19, 2020, Accepted July 21, 2020) Abstract. In the present paper, the effect of the location of stern planes on the flow entering the submarine propeller is studied numerically. These planes are mounted on three longitudinal positions on the submarine stern. The results are presented considering the flow field characteristics such as non-dimensional pressure coefficient, effective drag and lift forces on the stern plane, and the wake flow formed at the rear of the submarine where the propeller is located. In the present study, the submarine is studied at fully immersed condition without considering the free surface effects. The numerical results are verified with the experimental data. It is concluded that as the number of planes installed at the end of the stern section along the submarine model increases, the average velocity, width of the wake flow and its turbulence intensity formed at the end of the submarine enhance. This leads to a reduction in the non-uniformity of the inlet flow to the propulsion system. Keywords: numerical simulation; submarine model; stern planes; displacement; wake flow 1. Introduction Submarine is an underwater vehicle that includes the main hull and various appendages. The flow field around its main hull with no angle of attack does not show flow separation and vortex formation. However, when other appendage parts are mounted on the hull, the shape of the streamlines is greatly influenced by the shape of the hull, leading to the formation of a complex flow field around it. Wake flow behind the submarine hull has a significant effect on its performance. The fluid flow passes over the submarine model comprises a horseshoe vortex at the sail junction to the hull, a pair of sail tip vortices, sail wake flow, and a complex flow structure resulting from the interaction between wake flows and vortex structures generated by fins. Horseshoe vortex is a vortex system that creates a complex flow in encountering with the boundary layer flow and reaches the propeller. Just before the propeller, both horseshoe and stern planes tip vortices are produced at the stern for each fin. This thick wake is created by the reverse pressure gradient induced by surface change at the submarine’s heel. Fig. 1 shows the schematic of the vortex structures formed on the submarine body due to the presence of appendages. These vortex structures are created by the Corresponding author, Associate professor, E-mail: shateri@eng.sku.ac.ir a Ph.D. Student, E-mail: shbeigi.2478@gmail.com b Associate Professor, E-mail: dehghanmanshadi@gmail.com