Now showing 1 - 4 of 4
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    Numerical study on the hydrodynamic performance of integrated interceptor-flap fitted to the transom of a planing vessel
    (01-01-2018)
    Jangam, Suneela
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    Subramanian, Anantha
    Depending on the type of support, vessels are classified as displacement, semi-displacement and planing. But all types of vessels are in the displacement mode when they operate at low speed. In planing, due to the supportive hydrodynamic pressure, the hull wetted surface area reduces leading to low frictional resistance and consequent increase in speed for the same power input. Planing vessels are used for different purposes such as for fast patrol, sport activities, service, ambulance, rescue and recreation. The use of stern flaps, both fixed or controllable, interceptors and integrated interceptor-flap in high speed boats has become an acceptable option to control the running trim of the vessel to enhance its speed and powering performance. The interceptor-flap changes the pressure distribution underneath the hull which in turn causes reduced resistance acting on ships aftbody. The integrated stern interceptor-flap effect on planing craft performance depends on its parameters and also on those of the craft. So, an in depth study on the hydrodynamic behaviour of integrated interceptor-flap is essential, before it is adapted to a vessel, to get the best performance during the craft operation. In recent years, the computational fluid dynamics (CFD) technique has proved to be accurate and robust for hydrodynamic calculation of high-speed planing hulls. The aim of this paper is to study numerically on the performance of planing hull fitted with integrated stern interceptor-flap configuration. These studies help in understanding the flow field and other parameters on resistance of planing hulls with different flap angles. The study shows that the interceptor-flap performs well compared to bare hull. The guidelines that could be derived from these studies help in improving the interceptor-flap design for a high speed planing craft.
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    Experimental and numerical study on trim and sinkage of a high speed catamaran vessel in shallow waterways
    (01-12-2009)
    Krishna, B.
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    Many areas of seas, harbours and channels that were considered deep and safe for vessel navigation have been changed into dangerous shallow water regions for the new generation vessels due to their drastic increase in size and speed. Hence, the understanding of the safe speed of a vessel to prevent it from grounding when it operates in restricted waterways is gaining more importance. A catamaran vessel, being one of the new generation vessel configurations, is considered here to study the effect of its under-keel clearance of water and also its demi-hull spacing in the determination of a safe vessel speed. The numerical study using RANSE based CFD solver Fluent has been complemented by results obtained from experiments carried out in the towing tank of IIT Madras using the newly commissioned floating false bottom facility. © 2010 - IOS Press and the authors. All rights reserved.
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    Publication
    Computational study on the hydrodynamic effects of interceptors fitted to transom of planing vessel
    (01-01-2019)
    Jangam, Suneela
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    Anantha Subramanian, V.
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    The use of stern flaps, either fixed or controllable and interceptors in high-speed boats, has become an acceptable option to control the running trim of the vessel to enhance its speed and powering performance. The interceptor changes the pressure distribution underneath the hull over a certain distance forward of the transom. The stern interceptor effect on planing craft performance depends on its parameters and also on those of the craft. The aim to improve the performance on already built high-speed crafts has become an important issue for ecological and economic aspects. So, an in-depth study of the hydrodynamic behaviour of interceptor is essential, before it is adapted to a vessel, to get the best performance during the craft operation. Computational fluid dynamics (CFD) is being used for modelling ship flows due to the advances in computational methods. The aim of this paper is to predict the pressures and resistance characteristics of a high-speed planing craft equipped with an interceptor. The data regarding trim and resistance is generated for a planing hull with interceptor using CFD. In view of the above, an interceptor with 1mm height is used to study the performance of a planing hull and compared with the experimental studies of Savitsky, Steen, and Srikanth. The numerical model predicts favourable trim and reduced drag for the planing hull with an interceptor.
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    Publication
    Hydrodynamic performance of planing craft with interceptor-flap hybrid combination
    Different innovative ideas on simple stern fixtures such as stern wedges, flaps, interceptors have evolved over the past few years to improve the hydrodynamic performance of high-speed vessels, including planing crafts. This paper examines the hydrodynamic performance of a planing craft fitted with an interceptor alone and also an interceptor-flap combination at its stern, and the results are compared with the case where the craft uses the interceptor alone. An interceptor-flap combination is the one where an interceptor extends vertically downward at the transom with a flap attached to its end. Different angular orientations of the flap attached to interceptor bottom end and project towards aft are considered in the present study. The effectiveness of the integrated interceptor-flap system on the hydrodynamic performance of the vessel is influenced by the angular orientation of flap to the interceptor. Experiments were carried out on a planing hull with and without interceptor in the towing tank, Department of Ocean Engineering, Indian Institute of Technology Madras. Computational fluid dynamics (CFD) simulations are performed for the planing hull fitted with an integrated interceptor and flap. The investigations look into the aspects of vessel resistance, trim and bottom pressure distribution while it operates in calm water condition and at different speeds. The results show that trim and resistance of the vessel reduce with the use of integrated interceptor-flap at the stern with the flap angle at about 4° to the horizontal and they are less compared with a case where the only interceptor is used.