THE TURBULENT WAKE OF A SUBMARINE MODEL IN PITCH AND YAW

Abstract

Introduction We aim to improve our understanding of the high Reynolds number wakes formed by maneuvering submarines. When the submarine is pitched or yawed, a complex, three-dimensional separation occurs over the body which results in a non-axisymmetric wake. Studies on wakes have typically been confined to planar or axisymmetric wakes generated by disks, spheres, and other bodies-of-revolution (see, for example, Johannsson and George (2006) and Jimenez et al. (2010)). In contrast, the downstream development of the nonaxisymmetric wake has been much less well studied. Lloyd and Campbell (1986), in a study of submarine wakes noted that the azimuthual adverse pressure gradient on a pitched, body-of-revolution causes boundary layer separation, and the separated shear layers then roll up in to streamwise vortices, which increase in strength as more fluid is entrained into the vortex cores until they are shed into the wake with a fixed circulation (see Figure 1). They found that at high angles of incidence asymmetric vortex patterns may be visible but that these angles of incidence are not generally encountered by submarines. As we shall see, such asymmetric wake patterns appear to be characteristic of pitched or yawed bodies of revolution at sufficiently high Reynolds number even at lower angles which may well be encountered by maneuvering submarines. In another important study, Chesnakas and Simpson (1997) investigated the three-dimensional flow