It is well documented that the introduction of certain polymer substances into a turbulent boundary layer results in a significant reduction in flow noise. This means that the detectability of the submarine is reduced in those frequencies where the flow noise is reduced. Further, the reduction of flow noises permits the submarine to move at increased speed while maintaining its listening ability. This increase in quiet speed, as it is called, results in an increased search rate. The search rate, which is the product of the forward speed of the submarine and twice the detection range, may be increased by use of polymers through a combination of two factors. First, because the detection range is increased by the reduction in self-noise, the search rate is increased with no increase in platform speed. Secondly, the reduction in self-noise at the original search speed allows the submarine to search at a higher speed at the same limiting self-noise level previously experienced at the lower speed. In both cases the search rate is increased. The maximum search rate will occur at an intermediate speed between the two.
Although a linearized model is not exact, if the actual variation of detection range with platform is a monotonically decreasing function, then the qualitative conclusions drawn will pertain.
The importance of the foregoing discussion is that the utilization of polymer additives to a submarine’s boundary layer not only affords enhanced search capability but also affords that capability in a range of speed options, thus enabling the listening platform to adjust its listening capability at or above the maximum level achievable without polymer.
W.J.R.
