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Our customer is a reputed shipbuilder engaged in construction of commercial vessels and warships for the navy. They were carrying out design and manufacturing of launcher tube system of a submerged vessel. A common issue with tube launch is initiation of cavitation, which will retard the “plug” being launched. Before prototype testing, the client sought CFD simulations to understand the extent of cavitation and ways to mitigate it.

Zeus Numerix used its proprietary software CFDExpert™ to simulate tube launch hydrodynamics. CFD was conducted at different time instances with corresponding “plug” location, velocity and acceleration. Flow parameters ahead and behind the plug were noted. As expected, cavitation was predicted near the tail end of “plug”. Initiation of cavitation was found to be a function of submerged depth as well as internal bore profile of tube.

(top) Schematic of Tube Launch; (bottom) Time History of Pressure Drop                                                            and Plug Tail Pressure.

For each design of tube internal profile, the client was supplied with a detailed analysis report covering the onset and duration of cavitation. Accordingly, the client selected the most optimum tube profile. The study report was used to get sufficient confidence level on the tube design and hence move ahead with building the prototype.