DES-based computation of the flow around the DARPA suboff

Abstract

Flow modelling is a key issue not only for the correct prediction of hull-propeller interactions, manoeuvring characteristics and the flow field in the stern region of any marine vehicle, but also for the correct estimation of the fuel consumption. The paper describes a thorough investigation of the hydrodynamic performances of the DARPA suboff hull. The flow is numerically simulated by integrating in time the unsteady Navier-Stokes equations in which closure to the turbulence is achieved by means of a modified detached eddy simulation (DES hereafter) technique. The solver used for the purpose is the ISIS-CFD, part of the Numeca FineTM/Marine suite, which employs the finite volume of fluid technique. A comparative analysis between the numerical solutions based on the DES and explicit algebraic stress model (EASM hereafter) are provided in an attempt to sustain the choice for the turbulence model in the present study. Extensive parallel computations are carried out on 120 processors for which comparisons with the experimental data prove the accuracy of the chosen investigation methodology. A grid convergence test is performed for verification and validation purposes.

Large Flow Separations around a Generic Submarine in Static Drift Motion Resolved by Various Turbulence Closure Models

“…As mentioned above, the flow starts from rest and is accelerated for 5 s on a halfsinusoidal ramp for numerical stability. Solutions converge rather fast after the acceleration period, regardless of the incoming flow velocity, as shown in A former study carried out by the author [12] for the same hull moving in a straight course was entirely based on the hybrid SST-DES model of the turbulence closure, which revealed its advantages over the classic RANS approach. The IDDES model is proposed herein as an alternative aimed at describing better the local flow features.…”

“…The speed interval corresponded to a range of Reynolds numbers between 5.9•10 6 and 1.8•10 7 , where Re is based on the hull length, the oncoming flow velocity and the dynamic viscosity of the fresh water at 15 °C. The numerical solutions computed by using the 𝑘 − 𝜔 SST and hybrid DES SST were previously compared by the author in [12] with the experimental data reported by Crook [54] and Liu et al [55] who measured the resistance in a deep water towing tank for running speeds between 4.5 and 18 knots.…”

“…The Reynolds averaged Navier-Stokes (RANS hereafter) method has been commonly used for predicting the resistance [12,13], self-propulsion [14][15][16][17], maneuvering [18], and near-surface performance [19][20][21]. Aside from that, DES, DDES, large eddy simulation (LES), and direct numerical simulation (DNS) methods have also been used in the studies of hydrodynamic performances [14,22,23], boundary layer [24], and vortex structures [25,26], respectively.…”

Numerical Flow Characterization around a Type 209 Submarine Using OpenFOAM

“…On the other hand, if the submarine propeller [9,17], self-propulsion problem [12][13][14]18,26], or maneuvering characteristics [27,29] are numerically assessed; then a full-domain approach must be used. The present work focus on the forward hull region below the free surface interface, where the flow is expected to be axisymmetric when fully submerged as reported by Lungu [6], that is slightly perturbed by the occurrence of breaking wave in front of the bow due to vertical, cylindrical bow that is symmetric around centerline when operating at surface depth, as reported by Jasak et al [33]. Thus, half-domain approach is chosen in this work and decreasing the required time per simulation.…”

“…They confirmed the presence of streamwise vortices on the leeward side at large angles of attack and identified a laminar separation near the submarine stern at low Reynolds number. A thorough investigation of a more complex geometry configuration was performed by Lungu [6], who analyzed the hydrodynamic performance of SUBOFF hull including the sail and four stern appendages using a modified Detached Eddy Simulation (DES) approach. In this work, the streamwise velocity, the pressure distribution and turbulent structures of the nose of the SUBOFF bow and sail confirmed the expected flow physics and showed that the wake at the propeller plane has significant velocity defects, which suggest that special attention is required when modeling the propeller performance.…”