To evaluate theinfluence of dof on manoeuvring predictions by direct CFD zig-zag simulations

In this paper, direct CFD zig-zag simulations of 10°/10° and 20°/20° are performed in deep water condition under the consideration of different degrees of freedom, namely 3 DOF, 4 DOF, and 6 DOF, to evaluate their influence on manoeuvring predictions. A modern container ship KCS with a slightly simplified semi-balanced rudder is chosen as the benchmark model. All simulations are conducted in the numerical environment FINETM/Marine with the ISIS-CFD code as the flow solver. It solves impressible unsteady RANS equations in full hexahedral unstructured meshes and implicitly couples the flow field with motion equations of a rigid body in 6 DOF. Current direct manoeuvring simulations are achieved by means of the overlapping grid technique. To reduce the computational effort, propeller effect is modelled by a simple prescribed body force model. Trajectories are straightforward recorded without any further treatment to extract hydrodynamic derivatives. The prediction accuracy is evaluated by comparing derived parameters, i.e. overshoot angles and times, peak yaw rates, drift angles, etc. against experimental data. In conclusion, 4 DOF and 6 DOF concept present similar results for current ship type. The tiny changes in pitch and heave motion indicate they can be neglectable to simplify the complex mesh strategy. In addition, the large roll angle over zig-zag manoeuvres implies that 4 DOF concept should be more reasonable for container ships to obtain roll-motion-related data. Meanwhile, 3 DOF concept underestimates all overshoot angles in each simulation. This also highlights the reasonability of 4 DOF concept

CFD Simulation of PMM Motion in Shallow Water for the DTC Container Ship

International audienceThis paper is devoted to the validation exercises with the ISIS-CFD code conducted for the test cases proposed for the MASHCON conference. CFD simulations have been performed for the 4 different pure yaw and pure sway test cases under shallow water condition. Predicted results are compared with the measurement data provided by FHR

Divergence-Free Extended Hybridizable Discontinuous Galerkin Method (X-HDG) For Laminar Incompressible Two-Phase Flow

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Towards automated computation with uncertainty estimation for industrial simulation of ship flow

Adaptive grid refinement is tested for routine, automated simulations of ship resistance in calm water. A simulation protocol for these computations is fine-tuned on one test case and then applied unchanged to three different cases. The solutions are numerically accurate and compare well with experiments. Effective numerical uncertainty estimation increases the trustworthiness of the solutions

TOWARDS UNSTEADY APPROACH FOR FUTURE FLUTTER CALCULATIONS

International audienc

Errors and uncertainties in CFD validation for non-equilibrium turbulent boundary layer flows at high Reynolds numbers

NATO AVT-RTG-349 was dedicated to the validation of computational fluid dynamics (CFD) methods based on the Reynolds-Averaged Navier-Stokes (RANS) equations and statistical turbulence models for non-equilibrium turbulent-boundary-layer flows at high Reynolds numbers. This paper describes and discusses the errors and uncertainties arising in the comparison of RANS simulation results with experimental data from wind-tunnel experiments. These errors and uncertainties are associated with the CFD grid and the discretization, the physical modelling, the measurement accuracy, and the differences in the flow conditions between the experimental facility and the computational set-up. The results show the need for a grid-convergence study using systematically refined families of CFD grids. The two major sources of errors are the RANS turbulence model and the uncertainty originating from the differences between the computational set-up and the wind-tunnel. Then two possible paths for future research are described: future CFD mesh generation, and future validation experiments at high Reynolds numbers

Ship-scale CFD benchmark study of a pre-swirl duct on KVLCC2

Installing an energy saving device such as a pre-swirl duct (PSD) is a major investment for a ship owner and prior to an order a reliable prediction of the energy savings is required. Currently there is no standard for how such a prediction is to be carried out, possible alternatives are both model-scale tests in towing tanks with associated scaling procedures, as well as methods based on computational fluid dynamics (CFD). This paper summarizes a CFD benchmark study comparing industrial state-of-the-art ship-scale CFD predictions of the power reduction through installation of a PSD, where the objective was to both obtain an indication on the reliability in this kind of prediction and to gain insight into how the computational procedure affects the results. It is a blind study, the KVLCC2, which the PSD is mounted on, has never been built and hence there is no ship-scale data available. The 10 participants conducted in total 22 different predictions of the power reduction with respect to a baseline case without PSD. The predicted power reductions are both positive and negative, on average 0.4%, with a standard deviation of 1.6%-units, when not considering two predictions based on model-scale CFD and two outliers associated with large uncertainties in the results. Among the variations present in computational procedure, two were found to significantly influence the predictions. First, a geometrically resolved propeller model applying sliding mesh interfaces is in average predicting a higher power reduction with the PSD compared to simplified propeller models. The second factor with notable influence on the power reduction prediction is the wake field prediction, which, besides numerical configuration, is affected by how hull roughness is considered

Resolution des equations de Navier-Stokes tridimensionnelles : applications au calcul d'un raccord plaque plane-aile

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc