Numerical investigation of flow structures around the DARPA SUBOFF model

A large eddy simulation (LES) of a fully appended SUBOFF model was performed by the Boundary Data Immersion Method (BDIM) with the Reynolds number of 1.2 × 10⁷. Numerical simulation is carried out through Fortran-based code and the geometric structure used in this paper is an idealized submarine (DARPA SUBOFF, with appendages). The computational uniformly distributed orthogonal grids consist of approximately 108 million nodes and are used to capture all essential flow structures. The pressure coefficients and streamwise velocity distribution obtained by the large-eddy simulation (LES) are in good agreement with the experimental data. The objective of this paper is to evaluate the ability of BDIM to predict the flow over axisymmetric hull, to investigate the evolution of the junction and tip flows on the body of the SUBOFF. Three different types of large-scale vortex structures were found around the sail, including horseshoe vortex, hairpin vortex and necklace vortex. The different vortex identification methods, namely, ω criterion, Q criterion and Liutex method, are used to capture and analyze the formation mechanism of various vortex structures. Meanwhile, by extracting the rotation and shear relative parameter ε around the sail, it can be found that the rotation is dominant in the vortex distribution profile.