EXPERIMENTAL AND CFD STUDY OF THE SURFACE THERMAL SIGNATURES AND BUOYANT TRAJECTORY OF THE SUBMERGED THERMAL WAKES

The temperature characteristics of the thermal wakes are important signals for the infrared remote sensing detection of underwater vehicles. In this work, the surface thermal signatures and buoyancy law of submerged thermal wakes were studied. The influence of the exit speed and underwater depth on the surface temperature distribution is investigated, and the correlations of exit Froude numbers (Fr)-buoyant trajectory-surface thermal signatures are analyzed. The research demonstrates that the temperature profile on the free surface of the thermal wake consists of two parts, a high-temperature core region and a weaker outer region. With the increase of Fr, the inertial force along the flow direction is enhanced, resulting in the location (x*), where the wakes first reach the free surface, increasing linearly, whereas the spread angle decreases. The thermal wake undergoes five stages during the underwater buoyant process, consisting of 1) near wake region, 2) first transition region, 3) stable rising region, 4) second transition region, and 5) far wake region. There is a direct influence for the submerged buoyancy trajectory on surface thermal signatures: the x* increases linearly with the length of the near wake region and decreases exponentially with a stable buoyancy angle.