Aqwa-Intro 14.5 L03 Aqwa Suite

© 2012 ANSYS, Inc. May 8, 2013 1 Release 14.5

14.5 Release

Lecture 03

ANSYS Aqwa Suite


A. Core Aqwa Programs

Aqwa-Line • 3-D diffraction & radiation analysis program for wave force

and structure response calculations; hydrostatic analysis

Aqwa-Librium • Structure equilibrium position and force balance

calculations; eigen-mode and dynamic stability analysis

Aqwa-Fer • Spectral analysis of structure motion (wave frequency

or/and drift frequency) and mooring tension in irregular waves


... Core AQWA Programs

Aqwa-Naut • Time domain program for wave frequency structure motion

and mooring tension analyses in regular and irregular waves

Aqwa-Drift • Time domain program for drift frequency and wave

frequency structure motion and mooring tension analysis in irregular waves

Aqwa Graphical Supervisor (AGS) • AQWA pre and post processor; on-line analysis


Librium

ANSYS

Mechanical AGS

Fer Naut Drift

Line

EXCEL

…Core Aqwa Programs


B. AGS AQWA Graphical Interface can be used to;

• Generate Mesh (for ship shape models)


AQWA Graphical Supervisor AQWA Graphical Interface can be used to;

• Post process

• Force & Response Curves

• Shear Force & Bending Moment


AQWA Graphical Supervisor AQWA Graphical Interface can be used to;

• Post process

– Pressure Contours

– Wave Surface Contours

– Diffracted Wave Surface


AQWA Graphical Supervisor

AGS Interface Overview

File - Open/close, and save AQWA models

Edit - Create and edit AQWA models

Run - Perform an AQWA analysis on the presently loaded model

Graphs - Display and manipulate AQWA results graphically

Plots - Display and edit AQWA models visually

Cable Dynamics - Define and analyze problems involving cable dynamics

Help - Access to the online help system


AGS File Handling

The File Menu provides access to open any of the standard AQWA files

These files will be discussed in detail later in this training session


AGS Database Review

Provides access to data and results stored on the AQWA database. Note that, in general, it is NOT recommended to change data using this interface.


AGS Analysis •Allows analyses to be run interactively.


AGS Graphs Allows graphical plotting of frequency and time domain information


AGS Model Visualization

Provides geometry and results presentation



View Centre provides model

shift/pan facilities Position model origin at

center of screen

Enter

coordinates of a

point that will be

positioned at

center of screen.

Select Plot to

update the view

Can also shift/pan

by clicking on the

point on the model

that is required to

be plotted at the

center of the

screen



View angle provides rotation

of model view

Rotations about screen Z

axis Rotations about screen X

axis

Current View Angle

Angle increment

C 30 degrees

M 10 degrees

F 1 degree

Isometric view

Elevations along X, Y, Z axes

Direction of view controlled

by + or – radio button



Zoom buttons provide zoom

in/out facilities Size to screen

Zoom in +/out -

Zoom increment

C Coarse

F Fine Current View Size

Can also zoom

in/out by left

mouse button

“rubber band” on

image



For analyses with multiple structures we can

select/de-select which are visible using the

colored check boxes at the bottom of the

visualization window

These boxes determine which

structures are visible. Red

indicates visible, white is not

visible. Click on box to

change status

Only one of these boxes will be

selected at any time. They

indicate which structure the

position information relates to


AGS Wave Contours

Allows for 2-dimensional wave surface contours to be plotted following an Aqwa-Line analysis

Wave directions and frequencies are accessed using an index number, rather than the specific values required. This index number is specified as part of the input data to Aqwa-Line


AGS Cable Dynamics Allows for additional processing and visualization of mooring line cable dynamics


C. AQWA Suite need to knows

File names

File types

Deck system

Restart stages


...AQWA Suite need to knows

AQWA File Names

• Every AQWA file name has two parts:

• run identifier (should be <= 28 characters) - a name to identify the run

• file extension to identify the type of file (e.g. *.dat, *.lis, *.res)

• A file name typically looks like;

• tanker.dat (input data)

• tanker.lis (output list file) etc...

• Each AQWA run involves several files

• The names of the run files (input/output) differ only in extension!


...AQWA Suite need to knows Input/Output Files

• *.dat input data file (ASCII, LBDNF) • *.lin input file for AGS mesh generator (ASCII) • *.sfm input mass distribution for splitting forces (ASCII, AGS) • *.wht a wave height time history (ASCII, D) • *.wvt a wind velocity time history, no card needed (ASCII, DN) • *.xft an external force time history, no card needed (ASCII, DN) • *.mor mooring description file (ASCII, BDNF) • *.res restart file (binary, LBDNF) • *.hyd hydrodynamics file (binary, L) • *.eqp equilibrium position file (binary, B) • *.uss source strength file (binary, L) • *.pot potential file (binary, L) • *.mes output message file (ASCII, LBDNF) • *.lis output listing file (ASCII, LBDNF) • *.pos output position file (binary, DN) • *.plt output graphic file (binary, LBDNF) • *.pac pressures at centroids (binary, L) • *.vac velocities at centroids (binary, L)

See Aqwa-Ref 1.3 for details


...AQWA Suite need to knows Input data (*.dat) file

• ASCII text file containing all the input data necessary for the Stages of Analysis about to be executed.

• in FIXED FORMAT and must be entered using a text editor.

• an editor that indicates the column & line no. of the current cursor position is highly recommended !!!

*.dat file format

• Most input data should be typed into the required columns !!!

• See Aqwa-Reference Chapter 4 for details

JOB MESH LINE

TITLE MESH FROM LINES PLANS/SCALING

OPTIONS REST END

RESTART 1 2

4col 4col5cols5cols 10 cols 10 cols 10 cols

01 COOR

01 1 45.000 -45.000 0.000

END01 999 0.000 0.000 -10.620

Column 21

02 ELM1

02QPPL DIFF 0(1)( 1)( 2)( 12)( 11)

06FREQ 1 6 0.10472 0.15708 0.25133 0.41888 0.52360



This is a binary file,

Written by all the AQWA programs

• Contains database associated with all the Stages of analysis which have so far been executed.

Typical information that can be contained on the .res file include:

• model definition

• hydrodynamic database

• main analysis parameters

Restart File (.res)



Comparison of .RES and .HYD (after Aqwa-Line solution)

Hydrodynamic File (.hyd)

• This is a binary file,

• Created by Aqwa-Line after diffraction/radiation analysis

• Contains a copy of the hydrodynamic database that is also stored on the Restart file

• Used in model manipulation (discussed in following workshops)

Restart File (.res) Hydrodynamic File (.hyd)

Data Stored Model definition Hydrodynamic database

Hydrodynamic database

Used For Additional analyses AGS Regenerating .hyd file

Additional analyses Data manipulation



This is a binary file,

Created during a solution stage

Contains either

• Forces and responses as a function of frequency

• Time history of forces and motions

• Positions and forces during iteration towards equilibrium

Used by the AGS

Graphical Plot File (.plt)



Deck system (now referred to as Data Category)

• AQWA Data (.dat) file has a predetermined deck system

• Each deck begins with a header, and terminates with an END statement, with the associated data defined between these statements

01 COOR

01 1 45.000 -45.000 0.000

01 999 0.000 0.000 -10.620

END

• Further explained later and in Workshops!!

Deck # Description

0 Overall administration parameters

1 Node coordinates

2 Element definitions

3 Material properties

4 Geometric properties

5 Global constants

6 Wave frequency and directions

7 Hydrodynamic properties

8 Drift force coefficients

9 Drift motion parameters

10 Hull drag coefficients

11 Environmental parameters

12 Constraints

13 Spectral/Regular wave parameters

14 Mooring line definitions

15 Starting conditions

16 Time integration/Iteration parameters

17 Additional hydro parameters for tubes

18 Printing options

19/20 Reserved for future use

21 Element and nodal loads

Deck header

Deck terminator

Data


...AQWA Suite need to knows RESTART Stages

• Categorize analysis procedures

• Can be run individually or in combination with each other

• Data transfer is done between stages

* Calculation Stage Only

STAGE # FUNCTION/DEFINITION RELEVANT DECKS

1 Model Definition 1 to 5

2 Hydrodynamic coefficient database 6 to 8

3 Diffraction/Radiation analysis (L)* -

4 Main analysis parameters 9 to 20

5 Main analysis (BFDN)* -


D. Aqwa-Line

Introduction

• Aqwa-Line is a 3D diffraction and radiation analysis program

• Frequency domain

• Structures are described by a number of panels

• Source distribution approach (boundary integration method)

• A source is placed at the centre of each panel and then the program solves for the source strengths, subject to the boundary conditions (details are addressed in Lecture 2 and AQWA Theory Manual)


...Aqwa-Line

Features

• Removal of irregular frequencies by auto-generated lid

• Multi-body hydrodynamic interactions (lid to suppress standing waves)

• Forward speed

• Second order forces

• Mean drift forces:

• Far field momentum theory

• Near field pressure-motion integration method

• Full QTF matrix (difference & sum frequency components)

Aqwa-Line provides hydrodynamic coefficients for use in other programs in the AQWA suite


...Aqwa-Line

General Warnings

Requirements Reason

Number of diffracting elements should be no more than 12k

Solution time

Maximum number of total elements is 18k

Solution time

Normals point out Modelling Convention

No gaps in between panels Force balance

Facets cannot cut surface Solution requirement


...Aqwa-Line

Geometric Property Warnings

• Area ratio of adjacent elements < 3

• Aspect ratio (AR) > 1/3, where

(C = 1 for quadrilateral elements,

C = 2.3 for triangular elements)

• Element centres must be at least one facet radius (rf) apart,

• Shape factor (parameter for regularity of panel)

• <0.2 = warning

• <0.02 = fatal error

• See AQWA Theory Manual for more detail

Csidelongest

areaAR .

2

arear f


...Aqwa-Line Hydrodynamic warnings

• Minimum wave frequency (rad/s) >

• Distance above sea bed must be > 0.5 rf

• Longest side < 1/7 wavelength

– Fatal error if more than %5 fail

• Nodes are not connected to another element = warning

dg /05.0


...Aqwa-Line

Aqwa-Intro_14.5_WS03.1_Aqwa-Line.pptx

AQWA-Intro_13.0_WS03.1_AQWA-LINE.pptx






E. Aqwa-Librium

Introduction • Equilibrium position, Static and Dynamic (oscillatory) stability

• Complex ship/offshore structure systems;

• Various mooring, fender, pulley, winch, constraints configuration;

• Equilibrium estimation under wave, wind and current combination;

• Database approach for static catenary mooring line;

• Finite element approach for dynamic cable (drag force);

• Iteration approach for determining equilibrium position;

• Calculate the eigenvalues of linearized stiffness matrix to obtain static stability;

• Eigenvalues of the impedance matrix to give dynamic (oscillatory) stability.

• Series of wave spectrums


...Aqwa-Librium Theory in Aqwa-Librium

• Equation for determining static equilibrium position

• K is the stiffness matrix of the system,

• F is the force matrix.

• The program iterates until X=|Xj+1-Xj| is less than a defined tolerance

• Static stability

• Eigenvalue λ (<0, unstable; =0, neutral; >0, stable)

• Dynamic stability

• Eigenvalue λ

• f<0, stable (converging oscillations);

• f>0 and g=0, unstable (steady oscillations);

• f>0 and g≠0, unstable (oscillatory divergence)

)()(1

1 jjjj XFXXX

K

0 XX K

),,0from(

,0

igfeXXXX

X

X

X

X

t

KCM

0I

KMCM11


...Aqwa-Librium Analysis procedure

A common method of analysis

• run Stages 1 to 3 in Aqwa-Line

• run Stages 4 to 5 in another program, e.g. Aqwa-Librium

Aqwa-Line Run Stages 1 to 3

Aqwa-Librium Run Stages 4 to 5

Input Files Output Files Input Files Output Files

Tanker.dat Tanker.lis Tanker.res Libtank.lis

Tanker.hyd Libtank.dat Libtank.eqp

Tanker.plt Libtank.res

Tanker.res

Referenced in RESTART

command starting from

Column 21



Stage 4 in Aqwa-Librium

• Model definition restart file

• Hydrodynamic database restart file

• Main analysis parameters input data file

Note

• Decks 1 to 8 data is read from the restart file

• Decks 9 to 20 are required in the input data file

• Decks 1 to 8 must be omitted

Stage 5 in Aqwa-Librium (Solution, no extra input)


...Aqwa-Librium Alternative analysis

This approach allows for model changes directly within a mooring analysis

• run Stages 1 to 3 in Aqwa-Line

• run Stages 1 to 5 in another program, e.g. Aqwa-Librium

Aqwa-Line Run Stages 1 to 3

Aqwa-Librium Run Stages 1 to 5

Input Files Output Files Input Files Output Files

Tanker.dat Tanker.lis Tanker.hyd Libtank.lis

Tanker.hyd Libtank.dat Libtank.eqp

Tanker.plt Libtank.res

Tanker.res

Referenced in FILE

command in deck 6



Stage 1-3 in Aqwa-Librium

• Model definition input data file

• Hydrodynamic database hyd file


Stage 4 in Aqwa-Librium


Note • Decks 1 to 20 data is read from the data file, but the

hydrodynamic database is not recomputed, it is copied from the previous Aqwa-Line run

• Decks 1 to 8 must be included

Stage 5 in Aqwa-Librium (Solution, no extra input)


...Aqwa-Librium Data Requirements JOB TANK LIBR

TITLE SINGLE BOX WITH LINEAR MOORING

OPTIONS REST PBIS END

RESTART 4 5 Tanker

09 NONE

10 NONE

11 NONE

12 NONE

13 SPEC

13SPDN 315.0

END13PSMZ 0.3000 2.0000 4.000 8.000

14 MOOR

14LINE 1 5001 0 6001 1.50E6 99.5

14LINE 1 5002 0 6002 1.50E6 99.5

14LINE 1 5003 0 6003 1.50E6 99.5

14LINE 1 5004 0 6004 1.50E6 99.5

END14

15 STRT

15POS1 100.00 0.000 0.000 0.000 0.000 0.000

END

16 LMTS

END16MXNI 200

17 NONE

18 NONE

19 NONE

20 NONE

JOB card

Read database

Deck 9: drift motion parameters

Deck 10: wind and current drag

Deck 11: environment

Deck 12: constraints

Deck 13: spectrum

Deck 14: Mooring system

NB new nodes needed

Deck 15: Initial position of COG in global frame


… Aqwa-Librium Options

Following Option cards can be used in Deck 0:

Option Function

STAT Static stability only (in JOB Card)

DYNA Dynamic stability only (in JOB Card)

PBIS Print Both Iteration Steps (prints full results at each step, in OPTION card)

PRAF Print all freedoms (in spite of DACF cards on DECK12, in OPTION card)


… Drag in AQWA

Current and Wind Force Coefficients (Deck 10) DIRN Dir#1 Dir#n 1 …. n (optional)

SYMX (optional)

CUFX Dir#1 Dir#n C1 …. Cn

WIFX Dir#1 Dir#n C1 …. Cn

– Dir: direction number – directions default to Aqwa-Line wave directions;

– C: Drag Force Coefficients

• For relative current velocity V in direction

– force in X direction = CUFX.V2

– force in Y direction = CUFY.V2

– yaw moment = CURZ.V2

If DIRN is not present in Deck 10,

the default directions are those

defined on the DIRN cards in Deck 6


... Drag in AQWA

Morison Drag Coefficients (for Ship Hull)

• Hull drag force on a diffracting structure to be calculated in a similar way to that for Morison element (velocity squared dependency)

MDIN Nrow Ncol C1 …. C6

– Nrow: Row number in drag matrix

– Ncol: Column number in drag matrix

– C1 – C6: Drag Force Coefficients

.

.

.

.

.

.

.

666564636261

565554535251

464544434241

363534333231

262524232221

161514131211

zz

yy

xx

CCCCCC

CCCCCC

CCCCCC

CCCCCC

CCCCCC

CCCCCC

DragForce


… Static Environmental Conditions

Define current and wind conditions

Provides for slab (CURR) and profiled (CPRF) currents

CURR 0.75 120.0 CPRF -300.0 0.50 120.0

CPRF -150.0 0.70 120.0

CPRF 0.0 0.85 120.0

CURR velocity direction CPRF zpos velocity direction

Wrt FRA


… Dynamic Environmental Loading

Regular (Naut only) or irregular wave information

Wind spectra

Constant current and wind (but only slab currents may be defined)

Cross swell spectrum

Note that Drift and Naut also permit import of pre-defined time histories of the following:

Wind speed and direction

External forces

Wave surface elevation

and also permits “on the fly” external force calculation through a dll interface



Wave spectrum definition

• Jonswap

• JONH startfreq finfreq gamma Hs Fp

• Pierson Moskowitz

• PSMZ startfreq finfreq Hs T0

• User defined

• UDEF freq ordinate



Wind spectrum definition

• Ochi and Shin wind spectrum

• OCIN

• API wind spectrum

• APIR

• NPD wind spectrum

• NPDW

• User defined

• UDWD cf cs I(z)

For wind spectrum the wind definition includes a reference height

• WIND velocity direction refHeight

• Note that if reference height is given, but no wind spectrum data is defined, AQWA will default to Ochi and Shin


… Mooring Lines

Mooring Lines are defined in Deck 14 and can be used for Librium, Fer, Drift & Naut

• Linear Elastic Line (weightless)

LINE Ns1 Nd1 Ns2 Nd2 K L

Ns1, Ns2 structure numbers

Nd1, Nd2 node numbers

K stiffness

L unstretched length

• Polynomial Elastic Line (weightless)

POLY K1 K2 K3 K4 K5

NLIN Ns1 Nd1 Ns2 Nd2 (Ts) L (Fw) (Fp)

K1, .., K5 tension coefficients

Ts winch tension

Fw winch winding in friction factor

Fp winch paying out friction factor

Ts, Fw and Fp are only needed when the POLY line is used as a winch


... Mooring Lines • Composite Elastic Catenary (with weight)

COMP Nz Nx Ne Zmin Zmax Slope

ECAT M1 A1 EA1 Tmax1 L1



NLIN Ns1 Nd1 Ns2 Nd2

Nz, Nx number of database points within z and x ranges (see next slide)

Ne number of ECAT in this COMP line.

Zmin/Zmax Z range (measured from the anchor) for the attachment node.

Slope sea bed slope (in degrees; positive for slope going up from anchor towards attachment point).

M1/2/3 mass per unit length for ECAT 1,2,3.

A1/2/3 equivalent cross section area.

EA1/2/3 Young’s modulus x area.

Tmax1/2/3 maximum tension.

L1/2/3 length of ECAT 1,2,3.

Ns/Nd structure and associated node numbers (Ns1: fairlead structure).

Start from anchor point


... Mooring Lines Quasi-Static Mooring Line Database

ZRMAX

ZRMIN

XRMIN XRMAX

Max. tension point

Slack point


… Other Mooring Data

Fenders 14POLY K1 K2 K3 K4 K5

14FEND Size Kf Kc

14FLIN Type Ns1 Nd1 Nd2 Ns2 Nd3 Nd4

K1 – K5 non-linear stiffness coefficients

Size uncompressed size of fender (normal direction)

Kf tangential friction coefficient

Kc normal damping coefficient

Type 1 = fixed fender, 2 = floating fender

Ns1 Structure to which fender is nominally attached

Nd1, Nd2 Nodes defining attachment point and contact plane on 1st structure

Ns2 Structure which fender contacts

Nd3, Nd4 Nodes defining contact plane on 2nd structure

Note: Be aware of valid range of force – extension/compression relationship

5)(5

4)(4

3)(3

2)(21

XKXKXKXKXKT


... Other Mooring Data

Refer to AQWA Reference Manual for more details

CARD Definition

BUOY/CLMP A buoy or clump weight

TELM Tether element. (for installed or towed stiff tethers)

WNCH Constant tension winch line

FORC A constant force in a constant direction

LINE/PULY Linear elastic pulley line

LE2D User defined tension/extension data base

SWIR Steel wire with non-linear stiffness

DWT0/LNDW A line winding in or out on a winch

LBRK Line breaking

FILE Read in mooring definition from an external file *.MOR

With weight

(COMP/ECAT,NLIN,

NLID)

Without weight

(LINE,NLIN)


… Initial Conditions

Define starting vessel positions (and velocities) • Librium and Fer

POSn xpos ypos zpos rxpos rypos rzpos

• Naut


VELn xvel yvel zvel rxvel ryvel rzvel

• Drift


VELn xvel yvel zvel rxvel ryvel rzvel

SLPn xpos ypos zpos rxpos rypos rzpos

SLVn xvel yvel zvel rxvel ryvel rzvel

Can use RDEP option to automatically utilize results from a previous Aqwa-Librium run


… Printing Options By default, not all results are output to limit file size

Additional data can be output by including specific commands

Can also be used to reduce the amount of data output

Command Definition

ALLM Output the velocity, acceleration and position of a user specified node defined in the NODE command

NODE Output the motion of a user specified node or the relative motion between two user specified nodes

PREV Write into *.LIS file every N time steps to reduce the size

PRNT Print a force not in the output by default (See Aqwa-ref 4.18.6)

PTEN Output mooring tension, anchor uplift, laid length etc for mooring line

ZRON Output the z position of a node relative to the incident wave surface

PMST Output mooring sectional tensions for cable dynamic case


...Aqwa-Librium

Aqwa-Intro_14.5_WS03.2_Aqwa-Librium.pptx

AQWA-Intro_13.0_WS03.2_AQWA-LIBRIUM.pptx






F. Aqwa-Fer

Introduction

• Principally for calculating the significant response of amplitudes in irregular waves.

• Frequency domain program

• Linearized stiffness matrix / damping to obtain the transfer function and response spectrum

• Simple, inexpensive approach to make systematic parameter study

• Series of wave spectrums and mooring configurations


...Aqwa-Fer

Typical applications:

• Calculation of wave frequency RAOs for uncoupled/coupled moored structures.

• Calculation of significant motions and tensions for the system due to wave frequency (high frequency) excitation.

• Calculation of significant motions and tensions for the system due to drift frequency (low frequency) excitation.

• Calculation of significant motions and tensions for the system due to wave frequency and drift frequency excitation combined.


...Aqwa-Fer

Theory in Aqwa-Fer

• Response spectrum in irregular waves

Sxixi(ω): response spectrum in i-th degree of freedom,

Hij (ω) : receptance matrix defined as:

Fj(ω): frequency dependent force (in j-th degree of freedom) on the

structure

S(ω): the wave spectrum

)())]()(([mod)( 2 SFHS jij

j

xx ii

12 ])())(([)( CBiMMH asij


...Aqwa-Fer

Linearization in Fer

• Stiffness: stiffness (hydrostatic, mooring etc. ) at the initial position

( = the static equilibrium position with RDEP option)

• Damping:

cable drag is linearized using the RMS velocity, when NLID used

FD = (CD. |VRMS|) .V

wind drag is linearized,

1st order hydrodynamic damping

any other input damping (fender, constraints)

• Forces: 1st and 2nd order wave forces


Typical Force-Extension curve for catenary mooring

Extension Initial position

Force

Working range

Aqwa-Fer uses stiffness (i.e. slope) at initial position

Aqwa-Drift/Naut uses changing stiffness over working range

...Aqwa-Fer Linearization


… Aqwa-Fer Options


Option Function

DRFT Drift frequency only (in JOB Card)

WFRQ Wave frequency only (in JOB Card)

RDEP Read Equilibrium Position (in OPTION card)

FQTF Use full matrix of difference frequency QTF’s (in OPTION card)

PRRI Printing RAO’s at spectrum integration points (in OPTION card)

GLAM Output significant motions in GLOBAL axis (in OPTION card)


G. Aqwa-Drift & Naut

Introduction

• Aqwa-Naut and Drift are time-domain simulation programs

• For a series of time-steps they:

• calculate the total force on the structure

• calculate the acceleration

• find the new position of the structure

• A two stage predictor/corrector integration scheme is used


...Aqwa-Drift & Naut Equations of motion in time domain

• F(t) is the total force on the structure, including

• Incident wave force

• Diffraction force

• Drift force

• Mooring force

• Radiation force (damping)

• ...

• The equations of motion are solved in convolution integral form;

F(t)(t)XΜ..

s

)()()()()()]([ 1

0

tFdXttKXtX

t

as hMM


...Aqwa-Drift & Naut Simulation of irregular waves

• Wave spectra processing:

• Spectrum is split into sections of equal area for integration

• Wave components are defined with frequency at the centre of the section (Max. 200)

• Wave components are added together with random phase angles

iii

N

iiiiii Satykxkatyx

)(2),sincoscos(),,(1

ω

Wave component: equal areas

S(ω)


...Aqwa-Drift & Naut

Drift vs. Naut

Drift Naut

Irregular waves only Regular or Irregular waves

Linear hydrostatic stiffness (mean water surface)

Non-linear hydrostatics and incident wave forces (instantaneous wave surface)

2nd order drift forces 2nd order incident wave (omits drift forces but some 2nd order effects)


H. Summary

Linearity in Aqwa Programs

Hydro-

Statics

Diff /

Radiation

Froude-

Krylov

Drift

Force

Mooring

Force Drag

Line LIN LIN LIN 2nd order - -

Librium

eqm NON LIN LIN 2nd order NON Linearised

Librium

stability LIN LIN LIN 2nd order LIN Linearised

Fer LIN LIN LIN 2nd order LIN Linearised

Drift LIN LIN LIN 2nd order NON NON

Naut NON LIN NON - NON NON


… Aqwa-Drift Options


Option Function

WFRQ Include wave frequency effects (in JOB Card). By default only drift effects are computed.

CONV Use Convolution (in OPTION card)

PBIS Print both integration steps (in OPTION card)

RDEP Read equilibrium position (in OPTION card)

FQTF Use full matrix of difference frequency QTF’s (CQTF OPTION in Line calculation is a prerequisite, in OPTION card)


… Aqwa-Naut Options


Option Function

IRRE Irregular wave analysis (in JOB Card, CONV mandatory)

CONV Use Convolution (in OPTION card)

LSTF Linear stiffness. Uses hydrostatics from Line without modification (in OPTION card)

RDEP Read equilibrium position (in OPTION card)


… Time integration data for Drift and Naut

Provides time step and duration for a simulation

TIME number timestep start

number number of time steps

timestep time step interval

start optional start time (default is 0.0)

Aqwa also provides for restarting from a previous analysis - HOTS


...Aqwa-Fer

Aqwa-Intro_14.5_WS03.3_Aqwa-Fer.pptx

AQWA-Intro_13.0_WS03.3_AQWA-FER.pptx






...Aqwa-Drift & Naut

Aqwa-Intro_14.5_WS03.4_Aqwa-Drift.pptx

Aqwa-Intro_14.5_WS03.5_Aqwa-Naut.pptx

AQWA-Intro_13.0_WS03.4_AQWA-DRIFT.pptx





AQWA-Intro_13.0_WS03.5_AQWA-NAUT.pptx





Aqwa-Intro 14.5 L03 Aqwa Suite

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