In a significant stride towards enhancing underwater vehicle stealth and detection technologies, a recent study led by Yu Lu from the Naval Architecture and Ocean Engineering College at Dalian Maritime University has shed light on the intricate interplay between hydrodynamic and thermal wakes of underwater vehicles. The research, published in the Journal of Marine Science and Engineering, employed advanced numerical simulations to explore how varying speeds, depths, and heat emissions influence wake characteristics.
Lu and his team utilized Delayed Detached Eddy Simulation (DDES) coupled with the Volume of Fluid (VOF) method to simulate the standard SUBOFF model under eight distinct operating conditions. These conditions included speeds of 10, 15, and 20 knots, depths of 10, 20, and 30 meters, and scenarios both with and without thermal discharge. The findings revealed that higher speeds accelerate the decay of wake temperature when heat is emitted, making the thermal wake harder to detect downstream. Conversely, without heat emission, turbulent mixing dominates the temperature field, and the effects of speed are minimal.
One of the most compelling discoveries was the positive correlation between vessel speed and wake vorticity. As speed increased, wake vorticity at a fixed location grew by approximately 30%, free-surface wave height rose from 0.05 to 0.15 meters, and the wavelength remained around 1.8 meters. Interestingly, dive depth was negatively correlated with wave height, decreasing from 0.15 to 0.04 meters as depth increased from 5 to 20 meters, while the wavelength remained largely unchanged.
The study also highlighted the critical role of submergence depth in thermal wake visibility. At a 10-meter submergence depth, the thermal wake was clearly detectable on the surface but became difficult to detect beyond 20 meters. This finding underscores the pronounced depth effect on thermal wake visibility, a factor that could significantly impact stealth navigation and detection technologies.
For maritime professionals, these insights offer valuable opportunities to enhance the design and operation of underwater vehicles. By understanding how speed, depth, and heat emissions influence wake characteristics, naval architects and engineers can develop more effective stealth strategies and improve detection systems. The research provides a quantitative evaluation of wake characteristics under varying conditions, paving the way for advancements in maritime technology.
As Yu Lu noted, “These results not only confirm the positive correlation between vessel speed and wake vorticity reported in earlier studies but also extend those findings by providing the first quantitative evaluation of how submergence depth critically limits thermal wake visibility beyond 20 meters.” This groundbreaking work, published in the Journal of Marine Science and Engineering, is a testament to the ongoing efforts to push the boundaries of maritime science and engineering.