How does the free surface affect the hydrodynamics of a shallowly submerged submarine?. (July 2018)

• Record Type: Journal Article
• Authors: Amiri, Mojtaba Maali; Esperança, Paulo T.; Vitola, Marcelo A.; Sphaier, Sergio H.
• Is Part Of: Applied ocean research. Volume 76(2018)
• Page Start: 34
• Page End: 50
• Publication Date: 2018-07
• Subjects: Free surface effect -- Wave interference effect -- Hydrodynamic behavior -- Resistance force -- Lift force -- Pitch moment -- SUBOFF submarine geometry -- URANS equations; Ocean engineering -- Periodicals; 620.416205
• DOI: 10.1016/j.apor.2018.04.008
• Languages: English
• ISSNs: 0141-1187

Abstract

Highlights: The interaction between the bow and aft shoulder waves appears to play a significant role in the hydrodynamic behavior of a shallowly submerged submarine. The humps and hollows in the resistance force curve are a consequence of the interference effects between the bow and aft shoulder waves. The presence or absence of the interaction between the bow wave trough and the aft shoulder low-pressure region has a crucial effect on the lift force and pitch moment. Abstract: It has long been recognized that a shallowly submerged submarine traveling beneath the free surface experiences a larger resistance force in conjunction with a lift force and a pitch moment, which all vary periodically with respect to Froude number. As is well known, the periodic behavior of the forces and moment mainly has to do with the interference effects between the dominant wave systems inside the submarine wake, which predominantly originate from the bow, stern and shoulders. In naval architecture, the principal type of interference is typically considered between the bow and stern waves, where the geometry undergoes abrupt changes. However, as the aft shoulder of a shallowly submerged submarine operates in a closer proximity to the free surface compared to the stern, it is surmised that interference between the bow and aft shoulder waves may have a more significant effect on the behavior of the forces and moments. Accordingly, the main purpose of the present study is to investigate whether the interaction between the bow and aft shoulder waves or the interaction between the bow and stern waves has a more dominant effect on the hydrodynamic behavior of a shallowly submerged submarine. In this regard, the straight-ahead simulations of a generic submarine with constant forward velocities are performed in commercial code STARCCM+ using URANS equations with a Reynolds stress turbulence model at submergence depths and Froude numbers ranging from h = 1.1 D to h =∞ ( D : submarine diameter) and from Fn = 0.205 to Fn = 0.512, respectively. The numerical model is partially validated against the existing experimental resistance force data. The analysis of the obtained results demonstrates that in case of the shallowly submerged submarines, the interaction between the bow and aft shoulder waves has a dominant effect on the behavior of the resistance force, lift force and pitch moment.