Resistance Characteristics of a Trimaran for different Side Hull Configurations
- Md. Kareem Khan, Shiju John, Sunny Verma, P.C. Praveen, Manu Korulla and P.K. Panigrahi
Abstract :Trimaran platforms have gained increasing importance in the recent past and over a decade because of their superiority over monohulls in several hydrodynamic aspects like stability, powering andsea keeping. Trimarans also offer numerous benefits such as larger payload and deck area, flexible layout, shallow draft operability and efficient fuel consumption in terms of weight to power relationships. Commercially trimarans seen today are used as passenger ferries, Ro-Ro vessels and pleasure boats where as naval applications focus on multirole and littoral combat vessels. Presently a research program is underway at High Speed Towing Tank, Naval Science and Technological Laboratory (NSTL) to evaluate the resistance characteristics of a 3000 tonne trimaran configuration through a series model tests and optimization studies in 0.1 - 0.7 Froude no. range. Present paper deals with the overall effect on trimaran resistance subjected to variation in side hull configuration in terms of its position, length and displacement. Comprehensive comparisons for the series of model test cases are also presented in this paper.

Energy Saving Device Evaluation in Full Scale Using Computational Fluid Dynamics
- L. Broberg and M. Orych, Flowtech
Abstract: The recent rush towards application of energy saving devices caused by increased demands on ship efficiency lead to installation of ESD on a wide variety of ship types. The evaluation of performance is still to a large extent based solely on the towing tank measurements while the experience in full scale gathered from sea trials is scarce. The significant differences in boundary layer development and wake field at the propeller position between model and full scale are often not taken into account in the ESD design. Therefore, the gains in required power are often severely overestimated. In the present work SHIPFLOW CFD code is used to evaluate power requirement changes in model and full scale conditions for a selected energy saving device. The stern flow determining the propeller working condition is analysed. The evaluation is performed using both the resistance and the self propulsion simulations for better understanding of the scale effects.

Development of Trial Ship for Naval Systems
- V. Srinivasa Rao, P. Ashok Kumar, V.B.S. Ayyangar, Manu Korulla and P.K. Panigrahi
Contact: bharatwaja.srinivasan@nstl.drdo.in
Abstract: Recent technology developments of systems for use at sea require extensive sea trials for characterization of the system performance. Naval Science and Technological Laboratory (NSTL), a premier research organization under DRDO is engaged in the development of naval systems. The sea trials of systems require ships as trial platforms. However, most of the vessels do not have facility for handling, launching and recovering the systems and hence their capabilities are limited. A preliminary design was undertaken by NSTL to draw the requirements of a trial ship with launch and recovery capabilities. The qualitative and operative requirements of the ship were evolved to finalize the layout of the operating area. A feasibility study on the possible hull forms (monohull and catamaran) to satisfy the requirements was carried out. Based on the study, the specifications of the vessel were finalized. This paper presents the details on the development of qualitative requirements and leading to the final specifications of the trial ship.

Failure Mode of Damage Analysis in Composite Material
Ashlesh R. Walke and Shailesh V. Deshpande
Abstract: The defence Naval vessels are using composite materials to weight reduction and corrosion resistance. These materials are most likely to experience high transient loads from ballistic impacts and are also exposed to cyclic loading during use in the field. Impact in structures made from composites, may not cause immediate failure. However, this damage may give rise to subsequent failure under service loads. The focus of this paper is to gain a fundamental understanding of the behaviour of composites when subjected to different loading conditions. Damage can occur in several layers of a composite, in multiple locations throughout its volume and develops through several internal mechanisms. By evaluating the distribution of stresses around the damaged regions, predictions of the progression of damage in the structure can help to determine the ultimate strength of the composite against conventional materials like aluminium.

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