Numerical investigation on the natural transition of boundary layers on an underwater axisymmetric body with heated/cooled walls

Heated/cooed walls serve as an effective method for controlling the transitions of boundary layers. This study investigates the stability and natural transition of the boundary layers on an underwater axisymmetric body with heated/cooled walls by using numerical methods. First, this study develops a stability analysis method for bow boundary layers on such walls, considering the dependence of water viscosity and thermal conductivity on temperature, temperature disturbances, as well as the streamwise and circumferential curvatures of the wall. Based on the results of the stability analyses, the transition positions are predicted using the eN method. The numerical results agree well with the experimental data, verifying the method's reliability. Subsequently, this study investigates the influence of wall temperature and oncoming flow velocity on the transition of boundary layers on heated/cooled walls. The results indicate that heated walls stabilize the boundary layer and significantly delay the transition position, while cooled walls produce the opposite effects. There exists an optimal heated wall temperature, at which the wall exerts the most pronounced effect in delaying the transition. Heated wall temperatures higher than this optimal value weaken the delay effect. The transition position is quite sensitive to variations in wall temperature on heated walls, while the sensitivity is less pronounced on cooled walls. Furthermore, regardless of whether the wall is heated or cooled, an increase in oncoming flow velocity destabilizes the boundary layer and advances the transition.