However, it has some demerits such as limitation of facilities, high cost of performance and scale effects. Out of the many methods available to determine the hydrodynamics of a submarine, the captive model testing approach is considered as the most accurate method to determine all linear and nonlinear derivatives used for mathematical modelling of forces and moment. To obtain these data, the submarine at design speeds is subjected to various modes of motion such as straight forward, drift, angle of attack, rudder deflection, circular and combined motion. In order to evaluate the manoeuvrability of a submarine, the prediction of hydrodynamic forces and moments acting on the vehicle along with their derivatives in various modes of motion is essential. Unlike ships, submarines must be controlled in six degrees of freedom and require a complex set of control surfaces to meet the demands of its controllability. Manoeuvrability plays a key role in the safe navigation and efficient service of a submarine. Later, in the advanced design phase, CFD runs are further made for transition location studies, analysis of propeller-hull interaction and scaling effects.Īnimation 1: Different modes of ship motion. Further, standard manoeuvres like zig-zag tests, turning circles and depth changes are also simulated to explore the effects of increase in control surface area, positional shift of sail in the longitudinal direction, inclination of the forward planes, etc.
In the early stages of design, investigations are made on the effect of change in size of control surfaces and sail, the effect of lengthening the hull by inserting new sections on the overall submarine manoeuvring characteristics, resistance and speed-power performance. Other characteristics that the designer needs to pay attention to, like, the cavitation properties and the propeller noise radiation in deeply submerged, periscope and surface conditions. Whether its change in the contour of hull, sail, control surfaces or even the propulsion arrangement, the design decision-making process revolves around these two fundamental parameters. In submarines and AUVs, any design thought is pivoted around two critical aspects of manoeuvring and speed-power performance. However, with the advent of higher computing power and robust algorithms, CFD is rapidly emerging as a quick, reliable and economical design tool. Though the areas of application of AUV’s have increased with time, their design and development cycle relying on traditional methods of model testing has been slow and expensive.
They are capable of performing a plethora of missions, including, under ice exploration, mapping and cable laying, pipeline and cable route survey and inspection, coastal survey and mapping, mine countermeasures, search and submarine hunting, hydrographic surveys, physical and chemical oceanographic survey, fish counting and environmental monitoring. While submarines predominantly are meant for military applications, AUV’s (visually looking like miniature submarines) have a wider range of applications. Submarines and Autonomous Underwater Vehicles (AUVs) have been in use for decades. Figure 1: Structured multiblock grid for DARPA Suboff submarine CFD simulationĢ159 words / 10 minutes read Introduction
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