© 2012 ANSYS, Inc. March 21, 2013 1 Release 14.5

14.5 Release

Lecture 05

ANSYS Aqwa/Mechanical Load mapping

© 2012 ANSYS, Inc. March 21, 2013 2 Release 14.5

A. ANSYS Offshore

Geometry modelling

AQWA CFX/Fluent Mechanical

HYDRO-STRUCTURAL DESIGN

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•Design Integration

...ANSYS Offshore Products

Geometry

Structural

CFD Motions/

Moorings

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B. Load Mapping Process

3D Hydrodynamic Panel

Model

Yielding, Buckling and Fatigue

Code Checks

Hydrodynamic Analysis Program

FEA Solver

Global FE Analysis Input with Coarse Mesh and

Locally Refined Mesh for Each Load Case

Global Structural FE Model

(Coarse Mesh for Yielding and Buckling

Check)

Motion and Load Response

RAOs

End

Structural Responses

(Stress, Strain and Displacement)

Geometry Modeler

Load Cases with Various Combinations of

Hydrostatic Pressures and

Hydrodynamic Pressures/Accelerations

Load Transfer and

Balancing Program

© 2012 ANSYS, Inc. March 21, 2013 5 Release 14.5

...Load Mapping Process

3D Hydrodynamic Panel

Model Global Structural FE Model

(Coarse Mesh for Yielding and Buckling Check)

Geometry Modeler

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...Load Mapping Process

3D Hydrodynamic Panel

Model

Hydrodynamic Analysis Program

Motion and Load Response

RAOs

Load Cases with Various

Combinations of

Hydrostatic Pressures and

Hydrodynamic

Pressures/Accelerations

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...Load Mapping Process

AQWA WAVE

• Calculation and transfer of loads to Mechanical

Load Cases with Various Combinations of

Hydrostatic Pressures and

Hydrodynamic Pressures/Accelerations

Load Transfer and

Balancing Program

A.K.A. AQWA WAVE

AQWA-LINE

Model

ANSYS

Model

Motions & Pressures

AQWA

WAVE

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C. Load Transfer Requirements

Hydrodynamic database of pressures due to:

• Hydrostatics

• Incident wave

• Diffracted wave

• Radiation effects

Structural mesh

• Define hull components

Steering information

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...Load Transfer Requirements Pressure Mapping

• Free floating body, therefore no explicit boundary conditions

• Wave pressure should be balanced by inertial loading

• AQWA-WAVE computed inertial load based upon AQWA model mass and inertia matrix

• Inertial load may not exactly balance pressures due to differences between structural and hydrodynamic models

• Mass inertia information may be checked from the structural model

*********** PRECISE MASS SUMMARY ***********

TOTAL MASS (X,Y,Z)= 0.30039E+08 0.30039E+08 0.30039E+08

MOMENTS AND PRODUCTS OF INERTIA TENSOR (I) ABOUT ORIGIN (GLOBAL CARTESIAN)

0.10717E+10-0.81854E+07-0.11227E+06

-0.81854E+08 0.24025E+10 -49530.

-0.11227E+06 -49530. 0.14226E+10

CENTER OF MASS (X,Y,Z)= 0.91020 0.95273 26.619

MOMENTS AND PRODUCTS OF INERTIA TENSOR (I) ABOUT CENTER OF MASS (GLOBAL CARTESIAN)

0.45005E+10-0.80984E+07 0.24211E+07

-0.80984E+07 0.36903E+10 0.25410E+07

0.24211E+07 0.25410E+07 0.34224E+10

PRINCIPAL CENTROIDAL MOMENTS OF INERTIA= 0.45010E+10 0.36852E+10 0.34224E+10

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...Load Transfer Requirements Panel pressures are extracted from database

Nodal values are computed from weighted averaging of pressures of connected panels

Finite element nodal pressures computed from weighted averaging of hydrodynamic nodal values

P1 P5

P2

P3

P4

P6

P7

N1

N2

N1

N2

N3

N4

© 2012 ANSYS, Inc. March 21, 2013 11 Release 14.5

...Load Transfer Requirements Hull definition

• Pressure mapping is for outer hull only, therefore we need to define this

We make use of

named selections, or

groups, to define the

outer hull

A dummy pressure

load is applied to the

outer hull for transfer

to the mapping

interface file

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D. Structural Analysis Free floating body analysis

• ANSYS offers two facilities to help with free floating model analysis

– Inertial relief; Computes accelerations based upon structural model

– Weak springs; Automatically removes free body singularities

Structural Responses

(Stress, Strain and Displacement)

Yielding, Buckling and Fatigue

Code Checks

FEA Solver

Global FE Analysis Input with Coarse Mesh and

Locally Refined Mesh for Each Load Case

End

AQWA WAVE

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...Structural Analysis

Structural Mesh

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...Structural Analysis

Stress Results

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...Load Transfer Requirements

ANSYS DM

Geometry

Hydrodynamic

Mesh

Structural Mesh

AQWAWB Solve

Hyd Database

Control Data

Structural Data

ANSTOASAS

AQWA WAVE

Pressure and

Acceleration

Data

/TITLE, CASE 1001 'H = 2.0 T = 62.8 D = 0.0 P = 0.0'

! COMPONENT ANSY

SFEDELE,ALL,ALL,PRES

FDELE,ALL

LSCLEAR,INER

SFE, 2409, 2,PRES,0, 0.0000E+00, -1.9740E+02, -1.9576E+02, 0.0000E+00

SFE, 2411, 2,PRES,0, 0.0000E+00, 0.0000E+00, -2.0081E+02, -1.9777E+02

SFE, 2412, 2,PRES,0, -1.9558E+02, -1.9503E+02, 0.0000E+00, 0.0000E+00

SFE, 2416, 2,PRES,0, 0.0000E+00, 0.0000E+00, -2.8120E+01, 0.0000E+00

SFE, 41361, 2,PRES,0, -3.9148E+02, -3.8728E+02, -3.8728E+02, -3.9161E+02

SFE, 41362, 2,PRES,0, -3.9092E+02, -3.8734E+02, -3.8728E+02, -3.9148E+02

SFE, 41363, 2,PRES,0, -3.9490E+02, -3.9511E+02, -3.8924E+02, -3.9014E+02

SFE, 41364, 2,PRES,0, -3.9014E+02, -3.8543E+02, -3.8734E+02, -3.9092E+02

ACEL, 1.9891E-07, 4.2397E-07, -1.0044E-02

CGLOC, 0.0000E+00, 0.0000E+00, 2.5400E+01

DCGOMG, 3.0279E-08, -2.4966E-08, 3.1457E-10

© 2012 ANSYS, Inc. March 21, 2013 16 Release 14.5

...Structural Analysis

AQWA-Intro_14.5_WS05.1_Load_Mapping.pptx