Surface thermal characteristics induced by momentum wakes of submerged vehicles

Momentum wakes from a submerged vehicle can generate detectable thermal signatures on the water surface and reveal the vehicle trajectory. An outdoor facility measured wake induced surface thermal responses, and numerical simulations related propeller speed to the excess momentum coefficient γ. Two signature types were observed: a strong continuous signature with a continuous thermal region and a weak discrete signature composed of intermittent vortical structures. For near surface sailing, γ has little effect on peak intensity, with variations within 10%, but both positive and negative momentum accelerate signal decay. At greater depths, increasing γ first reduces the peak surface signal and then enhances it beyond a threshold. The minimum peak intensity occurs at γ ≈ 35%. No large scale vortices were observed when γ < 260%, which suggests that vortex formation during acceleration can be suppressed by controlling γ.