1 ITTC Symbols and Terminology List Version 2021 June 2021 Supersedes all previous versions Updated by the 29th ITTC Quality Systems Group ITTC Symbols and Terminology List, Version 2021 Table of Contents: 1.3.3.2 Flow angles etc ........................... 26 1. GENERAL ............................................. 5 1.3.3.3 Forces ..................................... 27 1.1 Fundamental Concepts ..................... 5 1.3.3.4 Sectional coefficients ................. 27 1.1.1 Uncertainty ................................... 5 1.3.4 Boundary Layers ........................ 28 1.1.2 Coordinates and Space Related 1.3.4.1 Two-dimensional Boundary Layers Quantities ...................................... 9 ..................................... 28 1.1.2.1 Basic Quantities .......................... 12 1.3.5 Cavitation ................................... 29 1.1.3 Time and Frequency Domain 1.3.5.1 Flow parameters ......................... 29 Quantities .................................... 13 1.3.5.2 Flow fields .................................. 29 1.1.3.1 Basic Quantities .......................... 13 1.3.5.3 Pumps ..................................... 29 1.1.3.2 Complex Transforms .................. 14 1.4 Environmental Mechanics .............. 30 1.1.3.3 Complex Quantities .................... 14 1.4.1 Waves ......................................... 30 1.1.4 Random Quantities and Stochastic Processes .................................... 15 1.4.1.1 Periodic waves ............................ 30 1.1.4.1 Random Quantities ..................... 15 1.4.1.2 Irregular waves ........................... 30 1.1.4.2 Stochastic Processes ................... 15 1.4.1.3 Time Domain Analysis ............... 31 1.1.4.3 Probability Operators 1.4.1.4 Frequency Domain Analysis ...... 31 (Superscripts) .............................. 16 1.4.1.5 Directional Waves ...................... 32 1.1.5 Balances and System Related 1.4.2 Wind ........................................... 33 Concepts ..................................... 17 1.4.2.1 Basic Quantities .......................... 33 1.2 Solid Body Mechanics ..................... 18 1.4.3 Ice Mechanics ............................. 34 1.2.1 Inertial and Hydrodynamic 1.4.3.1 Basic Quantities .......................... 34 Properties .................................... 18 1.5 Noise .................................................. 35 1.2.1.1 Basic Quantities .......................... 18 1.5.1 Underwater Noise ....................... 35 1.2.2 Loads .......................................... 19 1.2.2.1 External Loads ............................ 19 2. SHIPS IN GENERAL ......................... 36 1.2.2.2 Sectional Loads .......................... 20 2.1 Basic Quantities ............................... 36 1.2.3 Rigid Body Motions ................... 21 2.2 Geometry and Hydrostatics ............ 38 1.2.3.1 Motions ...................................... 21 2.2.1 Hull Geometry ............................ 38 1.2.3.2 Attitudes ..................................... 22 2.2.1.1 Basic Quantities .......................... 38 1.3 Fluid Mechanics ............................... 23 2.2.1.2 Derived Quantities ...................... 39 1.3.1 Flow Parameters ......................... 23 2.2.1.3 Symbols for Attributes and 1.3.1.1 Fluid Properties .......................... 23 Subscripts ................................... 40 1.3.1.2 Flow parameters ......................... 23 2.2.2 Propulsor Geometry ................... 42 1.3.1.3 Boundary conditions................... 24 2.2.2.1 Screw Propellers ......................... 42 1.3.2 Flow Fields ................................. 25 2.2.2.2 Ducts ..................................... 44 1.3.2.1 Velocities etc. ............................. 25 2.2.2.3 Waterjets (see also section 1.3.5)44 1.3.2.2 Circulation etc. ........................... 25 2.2.2.4 Pods ..................................... 44 1.3.3 Lifting Surfaces .......................... 26 2.2.2.5 Operators and identifiers ............ 44 1.3.3.1 Geometry .................................... 26 2.2.3 Appendage Geometry ................. 45 3 2.2.3.1 Basic Quantities .......................... 45 2.4.3 Large Amplitude Motions 2.2.3.2 Identifiers for Appendages Capsizing .................................... 70 (Subscripts) ................................. 45 2.4.4 Symbols for Attributes and 2.2.4 Hydrostatics and Stability .......... 47 Subscripts ................................... 75 2.2.4.1 Points and Centres (Still under 3. SPECIAL CRAFT ............................... 76 construction) ............................... 47 2.2.4.2 Static Stability levers .................. 47 3.1 Planing and Semi-Displacement Vessels ............................................... 76 2.2.4.3 Derived Quantities ...................... 49 3.1.1 Geometry and Hydrostatics ........ 76 2.2.4.4 Intact and Damage (Flooded) Stability ...................................... 49 3.1.2 Geometry and Levers, Underway ... .................................................... 77 2.2.4.5 Symbols for Attributes and Subscripts (under construction) .. 50 3.1.2.1 Geometry, Underway ................. 77 3.1.2.2 Levers, Underway ...................... 78 2.3 Resistance and Propulsion .............. 51 3.1.3 Resistance and Propulsion .......... 79 2.3.1 Hull Resistance (see also Section 1.4.1 on Waves) .......................... 51 3.2 Multi-Hull Vessels ........................... 80 2.3.1.1 Basic Quantities .......................... 51 3.2.1 Geometry and Hydrostatics ........ 80 2.3.1.2 Derived Quantities ...................... 52 3.2.2 Resistance and Propulsion .......... 81 2.3.1.3 Symbols for Attributes and 3.2.2.1 Resistance Components .............. 81 Subscripts ................................... 53 3.3 Hydrofoil Boats ................................ 82 2.3.2 Ship Performance ....................... 54 3.3.1 Geometry and Hydrostatics ........ 82 2.3.2.1 Basic Quantities .......................... 54 3.3.1.1 Geometry, Underway ................. 82 2.3.2.2 Derived Quantities ...................... 54 3.3.2 Resistance and Propulsion .......... 84 2.3.2.3 Efficiencies etc. .......................... 55 3.3.2.1 Basic Quantities .......................... 84 2.3.3 Propulsor Performance ............... 57 3.3.2.2 Derived Quantities ...................... 85 2.3.3.1 Basic Quantities .......................... 57 3.4 ACV and SES ................................... 86 2.3.3.2 Derived Quantities ...................... 57 3.4.1 Geometry and Hydrostatics ........ 86 2.3.3.3 Induced Velocities etc. ............... 59 3.4.2 Resistance and Propulsion .......... 87 2.3.4 Unsteady Propeller Forces .......... 60 3.5 Ice Going Vessels ............................. 88 2.3.4.1 Basic Quantities .......................... 60 3.5.1 Resistance and Propulsion .......... 88 2.3.5 Water Jets ................................... 61 3.6 Sailing Vessels .................................. 89 2.4 Manoeuvrability and Seakeeping ... 64 3.6.1 Geometry and Hydrostatics ........ 89 2.4.1 Manoeuvrability ......................... 64 3.6.2 Resistance and Propulsion .......... 90 2.4.1.1 Geometrical Quantities ............... 64 2.4.1.2 Motions and Attitudes ................ 64 4. BACKGROUND AND REFERENCES 2.4.1.3 Flow Angles etc. ......................... 65 ............................................................... 91 2.4.1.4 Forces and Derivatives ............... 65 4.1 Symbols and Terminology Group .. 91 2.4.1.5 Linear Models ............................. 66 4.2 Description of the List of Symbols . 91 2.4.1.6 Turning Circles ........................... 66 4.2.1 Classification .............................. 91 2.4.1.7 Zig-Zag Manoeuvres .................. 67 4.2.2 Structure of the Lists .................. 91 2.4.1.8 Stopping Manoeuvres ................. 67 4.2.3 Organization of the matrix 2.4.2 Seakeeping .................................. 68 structured list .............................. 91 2.4.2.1 Basic Quantities .......................... 68 5. PRINCIPLES OF NOTATION ......... 92 4 5.1 Excerpts of ISO 31 ........................... 93 5.3.2 Translations ............................ 103 5.2 Computer Symbols ........................ 102 5.3.3 Other References ...................... 103 5.3 Documentation ............................... 103 5.3.1 ITTC Documents ...................... 103 NOTE: bold letters are used to denote vectors Red colour identifies the additions/modifications of this ver4sion of the List ITTC Symbols 1 General 1.1 Fundamental Concepts Version 2021 1.1.1 Uncertainty 5 ITTC Computer Definition or SI- Name Symbol Symbol Explanation Unit 1. GENERAL 1.1 Fundamental Concepts 1.1.1 Uncertainty (The following table follows ISO/IEC Guide 98-3:2008 – Annex J) Half-width of a rectangular dis- Half-width of a rectangular dis- tribution of possible values of in- a tribution put quantity Xi: a = (a+– a_) / 2 Upper bound, or upper limit, of a+ Upper bound input quantity Xi: Lower bound, or lower limit, of a_ Lower bound input quantity Xi: Upper bound, or upper limit, of b+ Upper bound of the deviation the deviation of input quantity Xi from its estimate xi: b+ = a+ - xi Lower bound, or lower limit, of b_ Lower bound of the deviation the deviation of input quantity Xi from its estimate xi: b_ = xi – a_ ci Sensitivity coefficient ci f/xi . 1 Functional relationship between measurand Y and input quantities X on which Y depends, and be- f Function i 1 tween output estimate y and in- put estimates xi on which y de- pends. Partial derivative of f with re- f/xi Partial derivative