Surface temperature characteristics of underwater thermal jet based on thermal skin

In this study, the effect of underwater thermal jet on the thermal skin of water surface were conducted by ex-periments. The parameters, such as the Reynolds number, underwater depth, disturbance degree of the propeller, and the temperature difference between the thermal jet and ambient water, on the temperature distribution of the water thermal skin were analyzed. The results demonstrate that the infrared signal of the water surface is mainly caused by the destruction of thermal skin structure but not the direct thermal signal generated by the buoyancy of the thermal wake. Moreover, the damage of the thermal skin is closely related to the flow field of the lower water column. As the depth of the underwater jet increases, the greater the temperature difference be-tween the jet and ambient water, the larger is the area of temperature signal generated by the water surface, with a positive correlation between them. When the depth of the hot jet under the action of the thruster is small (d/D < 0.36Fr), the structure of cooling water is unstable during its rising due to the inhibition of water surface. This, has a random effect on the infrared signal of the water surface. This study could provide experimental support for revealing the mechanism of infrared characteristics at water surface caused by the buoyancy of underwater thermal jet.