Predicting surface wakes using LES and RANS-SST analysis

Conventional submarines are required to approach and pierce the surface with vertically mounted appendages such as a periscope or a snorkelling mast. These appendages are typically bluff bodies which can generate a significant wake profile which is susceptible to detection either by radar, sound, or visual sighting. Therefore, more details about the wake profile are required to understand the aspects of it which can be detected and identify any operational and design methods to reduce the risk of detection. This project includes the investigation into the capability of the Large Eddy Simulation (LES) and RANS-SST models within OpenFOAM to accurately replicate such operations. Thus, simulations using LES and RANS-SST were carried out to model the wake profile and fountain height generated by a cylinder under flow rates between 2 to 8 knots, ranging from subcritical to supercritical flow regimes (Re=2.7×104 to Re=4×105). The results were validated against published experimental and numerical data comparing the fountain height, free-surface contours, and variation in velocity signals in the wake. This study has shown the possibility to use LES to model and examine the wake generated by a cylinder allowing further study to be conducted in methods of reducing the risk of detection.