International Journal of Innovative Research and Development

R. Vijayakumar , S. K. Rao , R. V. Shashank Shankar

Abstract

The near field flow and drag estimation on cylindrical bodies moving concentrically inside tubes in an incompressible medium always fascinated Naval Platform designers while designing large projectile launchers. This paper presents the flow field numerical simulation on the published experimental work by Naval Underwater System Center, Newport, using the commercially available CFD software FLUENT based on the Reynolds averaged Navier Stokes Equations and k-epsilon turbulence model. Axisymmetric model was used in the simulation without considering appendages such as fins, rudders and propeller. Numerical analysis of such complex confined flows involving relative motion of the bodies is a challenging task. Dynamic mesh was used to solve the relative movement problem of the projectile and tube using user define programme to update the mesh. The results presented include, the characteristics of flow field in the annulus gap, pressure distribution on the moving object and the relation between increased drag and the annulus gap. The simulation results can be employed as reference in designing of such projectiles.

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Danio Joe , R. V. Shashank Shankar , R. Vijayakumar , Arnab Das

Abstract

Underwater gliders are Autonomous Underwater Vehicles propelled by buoyancy change to follow a "Saw-tooth" pattern of motion in sea. They are characterised by long endurance, low speed and low cost. Unlike propeller-driven AUVs, Underwater Gliders use buoyancy for altitude change and wings to produce forward motion. They find applications in areas like underwater surveillance and oceanographic research/survey. Various technologies/methods are presently in use to produce the buoyancy change, which is the primary means of propulsion. This paper aims to review existing gliders and methods of buoyancy control in use, like piston driven buoyancy tanks, hydraulic fluid operated expandable bladders, methods under research like chemical propulsion etc. This paper also enumerates the methods adopted in designing a 1000 m diving underwater glider. The glider, designed in a modular concept where in the buoyancy engine, roll-pitch motion engine and sensors package are divided into modules which can be changed for repair/up gradation purpose.

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S. K. Rao , R. Vijayakumar

Abstract

The study of underwater explosions (UNDEX) on ship/submarines became of interest during World War II when torpedo explosions near a ship created more damage than a direct hit. Following the war, many full scale ship shock trials were conducted by various countries providing the empirical data that is widely employed. The biggest threat to any marine platform is due to underwater weapons and hence understanding the phenomenon is essential. The sequence of events involved in an UNDEX starting from the detonation, shock wave, bubble pulses and cavitation have been introduced and the dynamics of the process including governing laws have been enumerated in the paper. The associated aspects of loading and method of analyzing the fluid structure interaction have also been highlighted. The development of such numerical methods to analyze the explosion and its effect on the fluid-structure can lead to design of safer ships and submarines. Moreover, the numerical simulation will eliminate the need for conducting expensive shock tests and trials.

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