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A Study on the Functionality of a Fluid-filled Core Model in Warship Panels Subjected to Underwater Explosion: A Proposed Alternative to Classical Air-backed Plates Debashis Wadadar and Asokendu Samanta Research and Rule development division Indian Register of Shipping Powai, Mumbai, India [email protected] ; [email protected] Abstract: In war-ship design, the response of side-shell to non-contact underwater explosion is of major concern. The impact of a torpedo fired from a distant submarine or the blast produced by an underwater mine may cause serious damage to the ship- hull and can pose a serious challenge to ship designers and constructors; thereby underpinning the necessity of doing a comprehensive UNDEX (Underwater Explosion) analysis of ship structural components. Although much study has already been devoted to air-backed plates (that being a natural representation of a ship panel), relatively less attention is paid to water-backed plates. In this paper, both air-backed (AB) and water-backed (WB) plate subjected to underwater explosion (UNDEX) are analysed numerically using a nonlinear explicit solver Dytran with Patran as pre-processor and post- processor. The present study is carried out based on the General Lagrangian–Eulerian (GLE) coupling technique, a fluid- structure interaction (FSI) approach, which is used to simulate the interaction between structure and surrounding fluid (air or water). Strain rate sensitivity effects are also considered by Cowper-Symonds relation. Deflection of water- backed plate is compared and correlated with the deflection of

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A Study on the Functionality of a Fluid-filled Core Model in Warship Panels Subjected to Underwater Explosion: A Proposed

Alternative to Classical Air-backed Plates

Debashis Wadadar and Asokendu SamantaResearch and Rule development division

Indian Register of ShippingPowai, Mumbai, India

[email protected] ; [email protected]

Abstract:In war-ship design, the response of side-shell to non-contact underwater explosion is of major concern. The impact of a torpedo fired from a distant submarine or the blast produced by an underwater mine may cause serious damage to the ship-hull and can pose a serious challenge to ship designers and constructors; thereby underpinning the necessity of doing a comprehensive UNDEX (Underwater Explosion) analysis of ship structural components. Although much study has already been devoted to air-backed plates (that being a natural representation of a ship panel), relatively less attention is paid to water-backed plates. In this paper, both air-backed (AB) and water-backed (WB) plate subjected to underwater explosion (UNDEX) are analysed numerically using a nonlinear explicit solver Dytran with Patran as pre-processor and post-processor. The present study is carried out based on the General Lagrangian–Eulerian (GLE) coupling technique, a fluid-structure interaction (FSI) approach, which is used to simulate the interaction between structure and surrounding fluid (air or water). Strain rate sensitivity effects are also considered by Cowper-Symonds relation. Deflection of water-backed plate is compared and correlated with the deflection of air-backed plate and validated with published results. Considering the consequence of less damage in water-backed condition, a new model is proposed as a suitable replacement of air-backed ship hull panel, with two parallel plates separated by water filled core. The influence of depth of water filled core on plate response is studied. Other damaging parameters like cavitation and reloading effects are also investigated for the proposed model and compared with similar plate in air-backed condition.

Key word: Under water explosion, Ship panel, Air-backed plate, Water-backed plate, Cavitation, Reloading.

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