Indian Journal of Geo-Marine Sciences Vol. 45(1), January 2016, pp. 44-53 Wave making system in submarines at surface condition * Mohammad Moonesun 1,2 , Yuri Mikhailovich Korol 1 , Seyyed Hosein Moosavizadegan 3 ,Hosein Dalayeli 2 , Asghar Mahdian 2 , Mehran Javadi 4 & Anna Brazhko 1 1 National University of Shipbuilding Admiral Makarov (NUOS), Faculty of Ship Design, Ukraine 2 MUT, Department of mechanical engineering, Isfahan, Iran 3 Amirkabir University of Technology (AUT), Department of maritime engineering, Iran 4 Isfahan University of Technology, Marine Laboratory, Isfahan, Iran *[E-mail: m.moonesun@gmail.com] Received 27 November 2014; revised 19 January 2015 In this paper the critical Froude numbers of the wave making system of submarines are evaluated at surface condition.. Focus of this paper is on finding out the hump and hollow of the wave making diagram, and related critical Froude number. Range of maximum Froude number in submarines is extracted statistically. For the study of this phenomenon, three methods are employed; CFD method, Experimental method and Analytical formulas. CFD analysis is performed for a bare hull of a submarine by Flow Vision (V.2.3) software, which is based on the solution of RANS equations. Experiments are conducted in the towing tank of Isfahan University of Technology (IUT) on two models with appendages and different bows (Tango and DREA). [Key world: submarine, wave making, resistance, Froude number, hump, hollow] Introduction Ship waves are believed to be due to Lord Kelvin idea (1904). He considered a single pressure point traveling in a straight line over the surface of the water, sending out waves. This consists of a system of transverse waves following behind the point, together with a series of divergent waves radiating from the point, the whole pattern being contained within two straight lines starting from the pressure point and making angles of 19 degrees and 28 minutes on each side of the line of motion 1 . The Kelvin wave pattern illustrates and explains many features of the wave system of ship or submarine. Near the bow of a ship or submarine, the most noticeable waves are a series of divergent waves that starts with a large wave at the bow and followed by others arranged on each side along a diagonal line. Between the divergent waves on each side of the body, transverse waves are formed having their crest lines normal to the direction of motion near the hull, bending back as they approach the divergent-system waves and finally coalescing with them. These transverse waves are most easily seen along the middle portion of a ship or submarine with parallel body or just behind a vehicle running at high speed. It is easy to see the general Kelvin pattern in such a bow system. Similar wave systems are formed at the shoulders, if any, and at the stern, with separate divergent and transverse patterns, but these are not always so clearly distinguishable because of the general disturbance already present from the bow system 1 . Since the wave pattern as a whole moves with the ship, the transverse waves are moving in the same direction as the ship at the same speed V, and might be expected to have the length appropriate to free waves running on the surface at that speed, . Conventional naval submarines are periodically obliged to transit near the surface or, at the surface of water for surveillance and recovery affairs such as: intake fresh air, charge the high pressure air capsules and starting the diesel-generators for recharging the batteries. The process of charging the batteries is the most time-consuming task at near- surface depth or snorkel depth for usually 6 to 10 hours. This time depends on the specification of the electric power system and the battery storage system. Submarines have usually 220 to 440 battery cells that should be charged in the period of snorkeling. Minimizing the resistance of a submarine, moving close to the ocean surface, is very important, because a submarine must save the energy for earlier charging