Signature Сontrol & Ocean Physical Field Division

HYDROPHYSICAL FIELDS RELATED TO WAKE AND SEA ENVIRONMENT

The Krylov Institute performs complete set of theoretical and experimental studies for reducing hydrophysical signatures related to ship wake to ensure ship stealth below and above water.

For investigating the wake-related and sea environment hydrophysical fields the Krylov Institute offers:

• Development of methods and software for calculation of characteristics of hydrophysical fields generated by ship motion in stratified sea environment;
• Development of methods and equipment for laboratory modeling of hydrophysical processes generated by interaction between ships and stratified sea environment;
• Laboratory and sea experimental studies of hydrophysical processes generated by interaction between ships and stratified sea environment;
• Development of methods for hydrophysical measurements in laboratory test basins and sea areas, and methods for processing and analysing of experimental data;
• Measurements of temperature, salinity and sea current velocity in various sea areas and data analysis for investigations of environmental hydrophysical processes.

The Krylov Institute has unique experimental facilities for investigating the processes in the medium of non-uniform density and interaction of objects with stratified marine environment including stratification basin.

Controlled parameters of the water density stratification:
temperature gradient – 0 to 1°C/сm;
salinity gradient – 0 to 10‰/сm.
Self-propelled model speed – 0.4 to 1.4 m/s.

The available instrumentation and visualisation equipment are able to record hydrophysical processes in the density stratified medium.

Propagation of internal waves in the body wake observed in horizontal plane by means of colored temperature measurement data

Generation pattern of the internal waves in stratified medium by body (1), by vortex zones (2) and by wake area after body (3)

Wake stages visualized with schlieren method: model (1), wake (2)

Wake flow at initial stage: developed turbulent disturbances (1), generation of the near-wake zone (2) – attached vortex and wake disturbances in the boundary area

For acquisition of hydrophysical data the Krylov Institute is using a multi-level instrumentation complex intended for measurement of current temperature and velocity at sea. This complex is based on towed and drifting thermistor chains as well as current velocity profile recorders.

Multi-level temperature field measurements in the marine environment

Towing of thermistor chain during temperature measurements

Measured temperature fluctuation field obtained during ship movement

Based on R&D work the Krylov Institute has developed:

• guidelines on simulation of the hydrophysical processes in 3D stratified sea environment;
• guidelines on registration and prediction of the spatial-temporal characteristics of hydrophysical fields in the non-uniform marine environment;
• guidelines on calculations of the spatial-temporal characteristics of ship wake taking into consideration density stratification and initial turbulence of the sea environment.