Prediction of acceleration and deceleration performance of a generic submarine model by closed-form solution and CFD

Building specifications of underwater vehicles necessitates the evaluation of acceleration/deceleration performance. Evaluating this performance requires the different methods for each desgn phase. This is mainly due to the maturity level of design and the acceptable computational cost. This study aims to compare three different closed-form solution-based methods, namely, Empirical-Analytic, CFD-Analytic and Experimental-Analytic that can be used to evaluate the acceleration/deceleration performance of a submarine model at different design stages. Derivation of the closed-form solution is demonstrated. The closed-form solution requires the main particulars of the submarine geometry and the hydrodynamic coefficients of added mass and resistance as inputs. Fully-appended DARPA Suboff configuration (AFF-8) without a propeller is utilised. Within the scope of the study, the necessary hydrodynamic coefficients are obtained using both semi-empirical and CFD analyses. Experimental values in the literature are used for the Experimental-Analytic method. These coefficients are later used in closed-form solution methods to obtain the trajectory of the vehicle. Additionally, direct manoeuvring simulations (DMS) are also performed via CFD. All CFD simulations are performed utilising OpenFOAM. An additional study is carried out for determination of the optimum computational parameters for DMS. In order to analyse the depth effects on the trajectories, the proximity of UV to the free surface situation (H = 1.1D) is also investigated. This study demonstrates that, for both depth scenarios, closed-form solution methods, employing semi-empirically determined resistance characteristics, provide reasonably accurate results.