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EN8000 Aqwa Tutorial

Evan Martin April 9th, 2009

Aqwa Suite   AQWA-LINE

  Diffraction & Radiation

  AQWA-FER   Frequency domain with irregular waves

  AQWA-LIBRIUM   Static and dynamic initial stability including mooring lines

  AQWA-DRIFT   time domain with irregular waves including slow drift

  AQWA-NAUT   non-linear time domain with regular or irregular waves

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Example Analysis Types   Irregular Wave Motions

  AQWA-LINE   RAO’s

  AQWA-FER   Spectral analysis   Statistical prediction of body motions

  Coupled Body Analysis   AQWA-LINE

  Added Mass & Damping   AQWA-FER

  Coupling constraints

  Regular and Irregular Wave Motion in Time Domain   AQWA-LINE

  Added Mass & Damping   AQWA-NAUT or AQWA-DRIFT

  Motion time history

Aqwa Line Assumptions   First order motions

  Harmonic

  Small amplitude

  Regular incident wave train   Small amplitude compared to its length (i.e. small slope).

  Potential Flow   Inviscid & Irrotational

  No viscous damping

  Zero or small forward speed (Fn < 0.3)

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Input Files   File name convention: AL<id>.dat

  AL – indicates Aqwa-Line analysis   <id> – arbitrary file identifier

  limited to six characters

  .dat – Required file extension   ie: Alfrygm.dat

  Structure   Decks – Sections of the input file corresponding to a

specified input type   Cards – Lines of the input file corresponding to a

specific input

Card Descriptions   Card Descriptions

Column Numbers

Examples

Input Description

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Restart Stages   Specify analysis to perform

  Allow analysis to be ran in parts   Allow different programs to be used in one analysis

  Aqwa-Line Stages   Stage 1 (Deck 1 – 5)

  Geometry definitions   Global parameters

  Stage 2 (Decks 6 & 7)   Analysis Parameters

  Stage 3 (No Inputs)   Radiation & Diffraction analysis

Aqwa-Line Inputs   Hull Geometry (Decks 1 to 4)

  Panels   Description

  Node Coordinates (Deck 1)

  Connectivity (Deck 2)

  3 or 4 node panels permitted (TPPL or QPPL)

  Guidelines   No gaps between panels

  Normal must point outwards from the body surface into the fluid

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Aqwa-Line Inputs   Hull Geometry

  Panels   Guidelines (Con’t)

  Longest edge of plate shorter than 1/7th of the wave length

  Elements should have an aspect ratio of greater than 1/3

  Distance from the center of panel to water surface (zs)

  zs > 0.000273 * (water depth)

  zs > 0.0000132 * (wave length)

  Ratio of areas of adjacent plates should be greater than 1/3

Aqwa-Line Inputs   Hull Geometry

  Masses   Hull mass composed of one or more point masses

  One Point Mass – Entire ship (CoG)

  Multiple Point Masses – Lightship (CoG) & Cargo

  Etc.

  Point Mass Description   Location (Deck 1)

  Associated Structure (Deck 2)

  Mass (Deck 3)

  Mass moment of inertia (Deck 4)

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Aqwa-Line Inputs   Global Parameters (Deck 5)

  Water Depth   Water Density   Acceleration Due to Gravity

  Wave Frequency (Deck 6)   Range selected to represent region where RAO’s and

wave spectra have significant energy   Sufficient spacing to adequately describe variation of

hydrodynamic coefficients   AQWA-FER will interpolate between specified values if

required

Aqwa-Line Inputs   Wave Direction (Deck 6)

  All possible directions of subsequent analysis   Negative frequency of encounters not premitted

  Additional Stiffness (Deck 7)   Mooring Lines

  Additional Damping (Deck 7)   Viscous Roll Damping

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Ferry Example   Displacement: 5,760

Tonnes

  Design Speed: 8.474 m/s

  Center of Gravity   47.93 m aft of FP

  4.987 above waterplane

  Viscous Roll Damping: 5.85×106 Ns/m

  Moments of Inertia   Roll: 3.56×108 kgŸm2

  Pitch: 4.84×109

  Yaw: 4.84×109

  Water Depth: 1000 m

  Frequencies: 0.25 to 2.2 rad/s

Input File Header   Deck 0 – Preliminary Deck

  Job Card   User ID

  Program – (Aqwa Line)

  Title   User description of the file

  Options   REST – Indicates a restart

  GOON – Ignore modeling rule violations

  END – Required at end of options

  Restart Stages

JOB 0001 LINE TITLE LABRADOR FERRY OPTIONS LDOP REST END RESTART 1 1

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Geometry Limitations   Wave Lengths: 12.7 to 1530m

  Longest Edge:   < 1/7th of the wave length = 1.82m

  Depth below surface (zs):   > 0.000273 * (water depth) = 0.546m   > 0.0000132 * (wave length) = 0.0202m

  For rectangular panel, minimum angle with surface   asin(2*0546/1.82) = 37˚

Panel Layout

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Hull Geometry   Deck 1 – Coordinate Positions

01 COOR 01 1 0.000 0.000 0.000 01 2 -2.000 0.000 -0.970

... 01 969 -100.320 3.302 0.000 END019999 -47.932 0.000 4.987

02 ELM1 02SYMX 02TPPL DIFF (1)(1,1)(2,1)(3,1)

... 02QPPL DIFF (1)(11,1)(16,1)(17,1)(12,1)

... END02PMAS (1)(9999)(1)(1) 02 FINI

  Deck 2 – Coordinate Positions

Student Activity   Based on printouts from the Aqwa reference

manual “AQWA Reference.chm”, write the input for the selected deck.   Use the inputs given below

  Pay attention to the number of spaces required

  Displacement: 5,760 Tonnes

  Design Speed: 8.474 m/s

  Center of Gravity   47.93 m aft of FP   4.987 above waterplane

  Viscous Roll Damping: 5.85×106 Ns/m

  Moments of Inertia   Roll: 3.56×108 kgŸm2   Pitch: 4.84×109   Yaw: 4.84×109

  Water Depth: 1000 m

  Frequencies: 0.25 to 2.2 rad/s

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Student Activity   Deck 3 – Material Properties

  Ships Displacement 03 MATE END03 1 575.876E4

04 GEOM END04PMAS 1 3.5625E8 0.0 0.0 4.8440E9 0.0 4.8440E9

  Deck 4 – Geometric Properities   Mass Moments of Inertia

Student Activity   Deck 5 – Global Parameters

  Water Depth   Water Density   Acceleration Due to Gravity

05 GLOB 05DPTH 1000.0 05DENS 1025.0 END05ACCG 9.806

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Student Activity   Deck 6 – Frequencies and Directions

  Wave Frequencies   Wave Heading

  Forward Speed

06 FDR1 06FREQ 1 3 0.250 0.300 0.350 06FREQ 4 6 0.400 0.450 0.500

... 06FREQ 28 30 2.100 2.150 2.200 06DIRN 1 1 180.0 END06FWDS 8.474

  Note: Aqwa only allows one direction to be used when a forward speed is given

Student Activity   Deck 7 – Frequency Dependent Parameters

  Roll Damping   Position of COG relative to waterline

07 WFS1 07FIDD 5.85E6 END07ZCGE 4.987

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Analysis   Completed Input Files

  alfrygm.dat   alfryhd.dat

  Run Commands   C:\aqwa\utils\aqwa57a LINE frygm

  copy alfrygm.res alfryhd.res   C:\aqwa\utils\aqwa57a LINE fryhd

  Example Output File   Alfryh2d180.lis

Plot of RAOs

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Plot of Phase Angles