Effect of submerged body shape upon its movement pattern near free surface

Object and purpose of research. This paper discusses the tests with submerged models of different shape moving near the free surface in the test tank. The purpose of the study was to determine how relative vertical displacement and crosssection shape lift of submerged body depend on the speed of its movement at different immersion depths. Materials and methods. Model test procedure, techniques and results of model. Numerical simulation was performed in ANSYS software package. Main results. Experimental and theoretical study on cross-section shape effect of submerged body upon its wave generation, vertical lift and movement pattern near free surface. Conclusion. The results of this research will be useful for further work towards greater horizontal movement stability of submerged body at various speeds depending on its hull shape and immersion depth.

Comparison of Different Modeling Techniques for Solid-Fluid Interface for Wave Loading

Computational fluid dynamics (CFD) has been used to estimate the wave loading applied to a fully submerged body near the surface. The Navier-Stokes equations were used for the present study. In terms of modeling the fluid-solid interface, two different techniques are available in ANSYS CFX. One is the Rigid Body Method (RBM) and the other is the Immersed Solid Method (ISM). This paper compares the two modeling techniques in terms of accuracy and modeling flexibility. For this study, a CFD model of the NPS tow tank with wave generation and a submerged body was created to investigate different methods of solid body modeling. A comparison of the RBM and ISM was performed modeling a submerged rectangular body at different depths. The models produced similar results when the body was lower beneath the wave surface with limited fluid-solid interaction. As the amount of fluid-solid interaction increased, the RBM showed increased amounts of wave energy dissipation as compared to the ISM. This disruption of the wave energy resulted in the RBM showing smaller body forces and moments when compared to the ISM solid model. The increased wave energy dissipation in the RBM is likely caused by the different mechanism for modeling body-solid interaction. The numerical results were also compared to the experimental data.

Vertical shift of submerged body moving near the free surface

Object and purpose of research. The object of the research is model tests of the submerged body motions near the free surface in test basin. The purpose of the study is to determine how the magnitude of the relative vertical shift of the submerged body depends on its speed. Materials and methods. The material for research is the modeling technique, technology and the results of model experiments in the test basin. Numerical modeling was performed using the ANSYS software package. Main results. Model tests and numerical experiments were carried out to determine the magnitude of the vertical displacement of the submerged body moving near the free surface and the forces acting on it. Conclusion. The results obtained are useful for horizontal stabilization of submerged body moving near free surface at different speeds.