© 2012 ANSYS, Inc. March 21, 2013 1 Release 14.5
14.5 Release
Lecture 05
ANSYS Aqwa/Mechanical Load mapping
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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
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...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
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...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
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...Structural Analysis
AQWA-Intro_14.5_WS05.1_Load_Mapping.pptx