Numerical Analysis of Propeller-induced Low-frequency Modulations in Underwater Electric Potential Signatures of Naval Vessels in the Context of Corrosion Protection Systems

Since October 2009 the laboratory of ATE has carried out collaborative research with the WTD 71 that aims for prediction, reduction and optimization of so-called underwater electric potential (UEP) signatures. COMSOL Multiphysics is used to numerically simulate potential distributions on the vessels hulls in the context of impressed current cathodic protection (ICCP) systems, and also the corresponding UEP signatures. The electrode kinetics is considered by using boundary conditions based on non-linear polarization curves. We demonstrate how the polarization resistance flattens singular peaks of the electric field at sharp edges, and hence reduces the near-field modulation of the UEP signature. The modulation of the total ICCP current by means of shadowing effects in the propeller-rudder configuration is considered, with the focus on frequency components corresponding to the so-called Vernier-/Nonius effect. In addition an interesting estimation is presented, about what ICCP-settings are recommendable in the context of a silent running (stealth operating mode).