Study Of Infrared Radiative Characteristics Of Nuclear-powered Submarine's Thermal Wake

The nuclear powered submarine releases a large amount of cooling water to the ocean when sailing underwater.Then the thermal wake is formed and rises to the sea surface under the action of buoyancy,which results in an abnormal temperature distribution.The important information of submarine,such as the model,orientation,etc.,could be obtained.On this basis,it is theoretically possible to track,locate and attack submarine.As a result,it is of great military significance to study the buoyancy law of the thermal wake.In this paper,the navigation process of submarine in the 3-D sea environment is studied numerically based on the dynamic meshing technique.Both of single-phase flow method and VOF method are used to simulate the buoyant process of thermal wake.The buoyant trajectory of the thermal wake,the corresponding temperature distribution and infrared characteristics on sea surface are obtained.The influences of sea-air interface,air flow over the sea and discharging plan of cooling water on the simulation results are analyzed.Furthermore,in order to compare the differences of numerical simulations with different CFD software,a solver based on the free-source CFD package Open FOAM is developed to study the thermal wake.Finally,the buoyant trajectory of the thermal wake and the infrared characteristics of water surface are studied experimentally in the water tank in order to validate the numerical simulation methods and the corresponding results.The results obtained in this work are summarized as follows.1.After discharged from submarine,thermal wake undergoes three stages,including near-wake,transition and far-wake.Finally a teardrop-shaped temperature abnormal area is generated on the sea surface;It presents obvious infrared outline when ?T>0.06 K,and the identification effect is better in the waveband of 8-12?m.2.The air flow over the sea and sea-air interface could suppress the buoyancy of thermal wake,which leads a decrease of the area of the region with ?T>0.06 K about 55%;The infrared signal is weaken as the temperature of cooling water reduces.The area with ?T>0.06 K decreases about 45% when the temperature is reduced by 20 K.This can be achieved by increasing the discharge rate.Therefore,it is an effective way of reducing the infrared signal and improve the stealth of submarine.3.The solver based on OpenFOAM gives reasonable results in the simulation of thermal wake.But it needs to be further extended to the real 3D case and validated by experiments,because there is a gap between the 2D simulation results and the real navigation process of submarine.4.The numerical results agree well with the experimental data.Compared with single-phase flow method,the VOF method is more accurate and suitable for the simulation of thermal wake.The results of this study have important theoretical value and broad application prospects.They could provide theoretical basis for the research and development of infrared detection of submarine.