Hydrodynamic Optimization of the Submarine with a Fully Parametric CAD Model

Abstract

This study was conducted to compare the performance of four different optimization studies that can be done to reduce the drag force that a submarine is exposed to in fully submerged conditions. The submarine used in the study is DARPA SUBOFF AFF-1, which aims to improve this design's hydrodynamic performance with drag reduction in fully submerged condition First of all, to obtain close results with the hydrodynamic experiment of this submarine design in the literature, a mesh independence study was carried out, and the most suitable mesh structure was found. Afterwards, the most used design variables and constraints were investigated by examining the submarine optimization studies in the literature, divided into four different optimization studies. After that, the design was fully parametrically modelled in the CAESES environment. During this modelling, changes were made in the parametric model according to each optimization study's design limits and design constraints. In all optimization studies, the buoyancy centres of the new designs derived using the Lackenby method were ensured to remain the same as the DARPA SUBOFF AFF-1. In this way, only the derived designs' hydrodynamic characteristics were changed, keeping the manoeuvrability constant. Optimization studies were carried out in two steps. Design of Experiment Methodology was used in the first step, and Tangent Search Algorithm was used in the second step. In these steps, a total of 1044, 532, 347 and 532 different designs were derived by CAESES, respectively. For these designs, solutions were obtained with the CFD simulation model verified by experiment in ANSYS Fluent environment and the results were evaluated over the drag force. After the study, approximately 13%, 8%, 9% and 10% lower drag forces were obtained, respectively, compared to DARPA SUBOFF AFF-1 in the optimum designs obtained in each optimization study. In addition, the optimization study that will reduce the drag force the most according to the design limits that should be considered when optimizing any submarine design and the relationship of the optimum design obtained as a result of this study with the initial design was learned. On the other hand, if there is no design limit before the optimization, an optimization study that will reduce the drag force at the maximum level without changing the manoeuvrability of the existing design has also been learned.