Free surface features of submarines moving underwater: Study of Bernoulli Hump

Submarines are known to produce certain surface manifestations, primary among them being a feature known as Bernoulli Hump (BH). BH is a rise and fall of sea surface height above the submarine, when the vessel cruises close to surface. This feature has been noted by many researchers but scant information is publically available on the same due to the classified nature of the data. A major part of the Wide Area Surveillance program for submarines of the world navies uses the detection of this BH. In this work, our objective is to detect and establish the presence of BH characteristics. After calibrating a known CFD code using experimental data, we make model simulations which clearly depict the BH and its features. We then show the path ahead for submarine detection using BH from observations of sea surface heights. Value of BH height for a submarine at 10m depth moving at 5 knots is about 20cm which falls within the 2 cm vertical resolution of altimeters. Though most of the studies were for calm waters, an introduction to the presence of regular wind waves is given at the end. •Wide Area Surveillance of submarines is a topic of national interest and requires the detection of submarines.•Bernoulli Hump is a manifestation on the free surface that can be detected.•We predict the Bernoulli Hump for different velocities and depths of operations of various classes of submarines.•The way forward for detection of Bernoulli Hump in the presence of wind waves is briefly mentioned.