An axisymmetric underwater vehicle-free surface interaction: A numerical study

Nematollahi, Ali; Dadvand, Abdolrahman; Dawoodian, Mazyar

doi:10.1016/j.oceaneng.2014.12.028

Cited by 39 publications

(15 citation statements)

References 21 publications

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“…Additional CFD studies on the free surface effect on underwater vehicles with different submarines types, other than SUB-OFF, have been performed. For example, the total drag and wake of an axisymmetric UWV model were studied at different depths and speeds using ANSYS CFX [20]. Numerical predictions showed good agreement with the experimental data, where drag coefficient is inversely proportional to Reynolds number for all submergence depths and it is inversely proportional to submergence depth form constant Reynolds number due to the wave-making resistance.…”

Section: Introductionmentioning

confidence: 93%

Numerical Flow Characterization around a Type 209 Submarine Using OpenFOAM

Paredes

Quintuña

Arias-Hidalgo

et al. 2021

Fluids

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The safety of underwater operation depends on the accuracy of its speed logs which depends on the location of its probe and the calibration thoroughness. Thus, probes are placed in areas where the flow of water is smooth, continuous, without high velocity gradients, air bubbles, or vortical structures. In the present work, the flow around two different submarines is numerically described in deep-water and near-surface conditions to identify hull zones where probes could be installed. First, the numerical setup of a multiphase solver supplied with OpenFOAM v7 was verified and validated using the DARPA SUBOFF-5470 submarine at scaled model including the hull and sail configuration at H/D=5.4 and Fr=0.466. Later, the grid sensitivity of the resistance was assessed for the full-scale Type 209/1300 submarine at H/D=0.347 and Fr=0.194. Free-surface effect on resistance and flow characteristics was evaluated by comparing different operational conditions. Results shows that the bow and near free-surface regions should be avoided due to high flow velocity gradient, pressure fluctuations, and large turbulent vortical structures. Moreover, free-surface effect is stronger close to the bow nose. In conclusion, the probe could be installed in the acceleration region where the local flow velocity is 15% higher than the navigation speed at surface condition. A 4% correction factor should be applied to the probe readings to compensate free-surface effect.

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Section: Introductionmentioning

confidence: 93%

Numerical Flow Characterization around a Type 209 Submarine Using OpenFOAM

Paredes

Quintuña

Arias-Hidalgo

et al. 2021

Fluids

View full text Add to dashboard Cite

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“…A conservation equation was solved to transport the volume fraction of one of the phases in this study. The density, ρ, and viscosity, µ, at any point are acquired by averaging volume phases as follows [25]:…”

Section: N-s Governing Equations and Turbulence Modelsmentioning

confidence: 99%

Computational Fluid Dynamics Study of Water Entry Impact Forces of an Airborne-Launched, Axisymmetric, Disk-Type Autonomous Underwater Hovering Vehicle

Chen

2019

Symmetry

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An autonomous underwater hovering vehicle (AUH) is a novel, dish-shaped, axisymmetric, multi-functional, ultra-mobile submersible in the autonomous underwater vehicle (AUV) family. Numerical studies of nonlinear, asymmetric water entry impact forces on symmetrical, airborne-launched AUVs from conventional single-arm cranes on a research vessel, or helicopters or planes, is significant for the fast and safe launching of low-speed AUVs into the target sea area in the overall design. Moreover, a single-arm crane is one of the important ways to launch AUVs with high expertise and security. However, AUVs are still subject to a huge load upon impact during water entry, causing damage to the body, malfunction of electronic components, and other serious accidents. This paper analyses the water entry impact forces of an airborne-launched AUH as a feasibility study for flight- or helicopter-launched AUHs in the future. The computational fluid dynamics (CFD) analysis software STAR-CCM+ solver was adopted to simulate AUH motions with different water entry speeds and immersion angles using overlapping grid technology and user-defined functions (UDFs). In the computational domain for a steady, incompressible, two-dimensional flow of water with identified boundary conditions, two components (two-phase flow) were modeled in the flow field: Liquid water and free surface air. The variations of stress and velocity versus time of the AUH and fluid structure deformation in the whole water entry process were obtained, which provides a reference for future structural designs of an AUH and appropriate working conditions for an airborne-launched AUH. This research will be conducive to smoothly carrying out the complex tasks of AUHs on the seabed.

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“…It is reported that at an immersion ratio of h/D=2 flow characteristics were similar to uniform flow conditions. Nematollahi et al [10] numerically examined the influence of free-surface on the flow around an underwater vehicle using VOF multiphase model at different immersion ratios and found that the VOF model was sufficient to simulate the interaction between geometry and free-surface. Goktepeli et al [11] carried out experimental studies using PIV measurements to investigate the flow structure around torpedo-like geometry under the influence of free-surface.…”

Section: Introductionmentioning

confidence: 99%