TRANSIENT ANALYSIS OF HYDRODYNAMIC INTERACTION EFFECTS ON AN AUTONOMOUS UNDERWATER VEHICLE IN PROXIMITY OF A MOVING SUBMARINE

When an Autonomous Underwater Vehicle (AUV) is operating close to a moving submarine, the hydrodynamic interaction between the two vehicles can prevent the AUV from maintaining its desired trajectory. This can lead to mission failure and, in extreme cases, collision with the submarine. This paper outlines the transient interaction influence on the hydrodynamic coefficients of an AUV operating in close proximity and in relative motion to a larger moving submarine. The effects of relative motion on the interaction behaviour were investigated via two manoeuvres, i.e. the AUV overtaking and being overtaken by the submarine at different relative forward velocities and lateral distances. The results presented are from a series of Computational Fluid Dynamics (CFD) simulations on axisymmetric AUV and submarine hull forms, with validation of the CFD model carried out through scaled captive model experiments. The results showed that an AUV becomes less susceptible to the interaction influence when overtaking at speeds higher than the submarine. The implications of the interaction influence on the AUV’s ability to safely manoeuvre around the submarine are also discussed.

Buckling Load Predictions of Panel and Shell using Vibration Correlation Technique

Prediction of buckling loads is a very important phenomenon for aerospace and marine industry. In this paper buckling predictions of a submarine hull is considered by using a shell element and a rectangular panel is considered by using a plate element. The buckling load of a submarine hull can be predicted by using vibration correlation technique. Determination of these buckling loads can be carried out based on the boundary conditions of the submarine hull structure. The technique will be carried by considering both surface conditions and to determine the crippling load of a hull. This paper aims to use VCT for a submarine hull structure used in marine, ocean and can compare the results to aerospace industry by considering a rectangular panel for which buckling is predicted using vibration correlation technique . VCT is not very extensively used in case of thermal buckling. However in this paper, VCT is applied to verify the thermal buckling of a simple thin rectangular panel subjected to parabolic loading.

Coupled vibration characteristics of a submarine propeller-shaft-hull system at low frequency

The coupled longitudinal and transverse vibration characteristics of a submarine propeller-shaft-hull system at low frequency are studied in this paper. Two substructures, which are the propeller-shaft subsystem and the submarine hull, are first modelled using the finite element method. The two substructures are then connected through bearings, which are simplified as longitudinal and lateral springs and dampers. The modes, the natural frequencies and the coupled vibration characteristics of the two substructures and their synthesized system are simulated. An experiment studying the dynamic characteristics of a large-scale submarine test-rig is proceeded and compared with the numerical results, showing great consistency. Finally, transfer path analysis of the low frequency excitation forces using power flow method is discussed.

Multi-objective shape optimization of submarine hull using genetic algorithm integrated with computational fluid dynamics

A multi-objective optimization framework is developed for design of submarine hull shape. Internal volume of the vehicle and its hydrodynamic drag are optimized by seamlessly integrating non-dominated sorting genetic algorithm and Reynolds averaged Navier–Stokes solver in a single code. The methodology seeks a geometric shape with minimum drag and maximum volume satisfying the constraints on the geometric design parameters given by a 5-parameter formula that describes the submarine hull. The shape of the sail is not a part of the optimization process, and only its longitudinal location over the submarine hull is optimized. Two design optimization approaches are proposed, solved and compared. In the first approach, the combined hull–sail location is optimized, and in the second, the hull shape without sail is optimized first, and for this optimized hull shape, the sail location is optimized next. Our reported results show that the former approach yields significantly lower drag.

Simulation of the impact resistance of Kilo type submarine loaded with non-contact mine explosion

The paper presents simulations of the state of stress and deformation of the Kilo class submarine hull loaded from pressure wave of non-contact mine explosion. To accomplish the task the finite element method was used. Pressure wave was described by T. L. Geers’a and K. S. Hunter model. The way of modeling the pressure wave using the acoustic medium implemented to CAE programs was shown. To describe the material an elastic-plastic model of Jonson-Cook which takes into account the speed of deformation was used. The paper presents pressure distribution on the Kilo type submarine hull exposed on 100 kg of TNT explosion load in front of the bow of the ship.