ITTC Dictionary of Hydromechanics Version 2017 Dictionary of Hydromechanics Alphabetic Prepared by the Quality Systems Group of the 28th ITTC • Benedetti L., CNR-INSEAN (Secretary) • Chen W., SSSRI • Clelland D., Strathclyde Univ. • Ferrando M., University of Genova, (Chair) • Johnson B., US Naval Academy (ret.) (senior) • Kobayashi E., Kobe Univ. • Morabito M. G., US Naval Academy • Park J. T., NSWC Carderock Div. • Sena Sales Jr J., LOC UFRJ • Woodward M. D., UTAS Version 2017 12/09/2017 1 ITTC Dictionary of Hydromechanics Version 2017 Table of contents Original INTRODUCTION ................................................................................................................. 1 A ........................................................................................................................................................... 2 B ......................................................................................................................................................... 13 C ......................................................................................................................................................... 24 D ......................................................................................................................................................... 39 E ......................................................................................................................................................... 44 F ......................................................................................................................................................... 48 G ......................................................................................................................................................... 55 H ......................................................................................................................................................... 58 I .......................................................................................................................................................... 62 J .......................................................................................................................................................... 65 K ......................................................................................................................................................... 66 L ......................................................................................................................................................... 68 M ........................................................................................................................................................ 72 N ......................................................................................................................................................... 77 O ......................................................................................................................................................... 79 P ......................................................................................................................................................... 81 Q ......................................................................................................................................................... 94 R ......................................................................................................................................................... 95 S ....................................................................................................................................................... 106 T ....................................................................................................................................................... 128 U ....................................................................................................................................................... 134 V ....................................................................................................................................................... 135 W ...................................................................................................................................................... 137 X ....................................................................................................................................................... 144 Y ....................................................................................................................................................... 145 Z ....................................................................................................................................................... 146 1 ITTC Dictionary of Hydromechanics Version 2017 Original INTRODUCTION This Dictionary is intended for a broad readership including practising naval architects who wish to acquire and apply knowledge of hydrodynamics and also physicists and theoretical hydrodynamicists who wish to apply their particular knowledge to the solution of ship problems. Engineering, physical and nautical terms in common use have not been included when did not require special definition in the context of ship hydrodynamics or when their meanings were self-evident. The work is arranged in the following sections prefaced with a brief reference to the nature if their content: 1. General 2. Vessel Geometry and Stability 3. Resistance 4. Propeller (including propeller geometry) 5. Cavitation 6. Seakeeping 7. Manoeuvrability 8. Performance ( in the context of speed and power) The order of entry for each item is: title, symbol, dimensions, followed by the definition. In each section the titles are arranged in alphabetical order. In this way, having found the item required, pe- rusal of the section will indicate other related items which may be of interest. For general reference, there is an overall alphabetical index of all titles and against each is given the section and page where the item is to be found. The symbols given are in accordance with those in the latest ITTC symbols list which is a comple- mentary document. In a number of instances, the list give alternative symbols and these are generally included except where a definite preference is indicated. Comments on the new Dictionary format: The ITTC QS Group had already started a new Dictionary in A4 paper format in MSWord 2007-10. The current draft is also in .docx format for both the A4 and 81/2 by 11 inch versions. This is because some of the figures do not translate properly back to MSWord 2003. It is distributed for review in Acrobat format to make printing easier. For editing purposes, single column format is much preferred over double column format where en- tries tend to jump around, especially explanatory figures. Since this is to be a web based document, continuously updated (possibly in wiki style), single column format may be preferred even for the current status of the dictionary. Note also that the old Dictionary has the concept on a separate line which increases the size of the dictionary. The new material uses a hanging indent to set off the name of the entry in bold and/or italics. For this draft, blue fonts were initially used to indicate new subjects and definitions. Items needing clarification are those in red fonts. The figure captions need to be made independent of the order in which they appear in each edition. Since the ITTC Dictionary of Hydromechanics will be updated by the QS Group using the wiki approach and other inputs, a numbered set of figures may not be appropriate but are continued for the present. 1 ITTC Dictionary of Hydromechanics Version 2017 A Acceleration zone (cavitation) In the sequence of cavitation erosion, the zone of the curve of weight loss versus time in which a rapid increase in weight loss occurs (the region between the incubation zone and the deceleration zone which see). Formerly called the Accumulation zone. Active rudder (propulsion, propulsor) See: Rudder, active Added mass (seakeeping) [M] The total hydrodynamic force, per unit acceleration, exerted on a ship or other body in phase with and proportional to the acceleration. Added mass coefficient (seakeeping) (Aij) [-] A non-dimensional coefficient expressing added mass (which see) in ith mode due to jth motion. Admiralty coefficient (performance) A quasi-dimensionless coefficient used for assessing or comparing the performance of ship. Admiralty coefficient = / , where ∆ is the displacement, V speed and P any corresponding 2 power. 3 3 Advance (manoeuvring) The distance by which the centre of gravity (CG) of a ship advances in the first quadrant of a turn. It is measured parallel to the approach path, from the CG position at rudder execute to the CG position where the ship has changed heading by 90 degrees (See Figure 1). Maximum advance is the distance, measured parallel to the approach path from the CG position at rudder execute to the tangent to the path of the CG normal to the approach path. The first of these terms is that most commonly used. Figure 1: Geometry of turning circle Advance angle (of propeller blade section) (propulsion, propulsor) 2 ITTC Dictionary of Hydromechanics Version 2017 See: Angle, advance Advance angle, effective (propulsion, propulsor) See: Angle, effective advance Advance coefficient (propulsion, propulsor) (J) [-] A parameter relating the speed of advance of propeller, VA to the rate of rotation, n, given by J VA nD ,