The effect of aft-control-surface deflection at angles of incidence for the BB2 generic submarine

The effectiveness of the Aft-Control-Surfaces (ACS) of a submarine is influenced by the angle of incidence of the boat and the resulting cross-flow. This paper quantifies the rudder and sternplate control derivatives for a generic submarine geometry having an X-plane ACS arrangement using computational Fluid Dynamics. For the boat running straight-ahead, the rudder and sternplate control force derivatives are nearly identical and are linear functions of ACS deflection. However, with the boat at an angle of drift or attack, the control derivatives for small control deflections are found to increase non-linearly with incidence. Further deflection reduces the control force to similar levels obtained when running straight-ahead. The paper discusses the control forces at different angles of boat incidence and ACS deflection, in order to improve the effective ACS deflection range and to limit undesired forces orthogonal to the control force.