Vertical zigzag maneuver of a generic submarine

Abstract

A study of a 10/10 vertical zigzag maneuver of the generic submarine Joubert BB2 is presented. CFD simulations, involving moving planes and rotating propeller using a dynamic overset technique, are performed at constant propeller rotational speed in model scale on four systematically refined grids and compared against experimental data for depth, pitch, pitch rate, vertical drift, vertical velocity, absolute velocity, and propeller thrust and torque coefficients. A grid study is also performed for the self-propelled approach condition before starting the maneuver, used to obtain the propeller rotational speed, controller vertical and horizontal commands, and boat attitude. The maneuver is also analyzed in full scale at 6, 10 and 15 knots. Results indicate that CFD matches very well the experimental data, even for the coarsest grid, with the propeller RPS converging slowest in grid. By comparing model and full scale results, it can be concluded that model scale simulations are a good surrogate for full scale for parameters related to motions, but as expected forces are strongly affected by scale and the propeller operational point changes considerably. Analysis of forces and moments affecting vertical control from hull, sail and stern planes, propeller and hull help understand the response of the vehicle.