ANSYS Offshore Products 14.0 Update · PDF fileVessel Loading Transfer from ... Wave-Wind...

© 2011 ANSYS, Inc. September 8, 2011 1

ANSYS Offshore Products 14.0 Update

Paul Schofield [email protected]

+1 281-676-7001

mailto:[email protected]


• Introduction

• What are the ANSYS Products for Offshore?

• Historical Perspective

• On-going Development Themes

• 14.0 Specifics

• Case Studies

• Conclusions

ANSYS Products for Offshore - 14.0 Update


• Reliable and Safe Product and Processes - Drilling and Production

– Deep-waters, high pressures

– Temperature variation

– Hurricane, waves,

– Dense areas, combustible and hazardous products

– Drilling through complex geology, long distances

– Many production and processing equipment : Topside, subsea

Key Market Problems


• Cost of Failure

– Human life

– Environmental concerns

– Delays and fines

– Loss of capital, time and equipment

Key Market Problems


• Structural Integrity

– Huge established inventory of fixed steel platforms

– Requirement for on-going structural integrity and re-assessment

– Assessment carried out at the global (system) level

– Additional need for component level detailed design

Assessment of Fixed Offshore Structures


• Transportation

• Installation

• Wave loading

• Pile/soil modelling

• Beam joint fatigue assessment

• Member and joint code checking

• Decommissioning

Fixed Structures - Design Solutions Joint Check

Member Check

Jacket Launch


• Remaining new Oil & Gas fields largely offshore, and in ever deeper water

• One off designs

• High capital investment

• Failure consequences high

• Extreme environmental conditions

• Ultra deep water

• Hurricanes

• Difficult to physically prototype given the design requirements

Assessment of Floaters


• Stability

• Integrity of mooring/tether systems

• Dynamic positioning (station keeping)

• Fatigue of moorings/risers

• Wave slamming

• VIM/VIV

• Structural integrity

• Human factors

Assessment of Floaters


• General Products

– DesignModeler/SCDM

– ANSYS Mechanical

– Explicit

– CFX/FLUENT

– ANSOFT

– EKM

• Vertical Applications

– AQWA

– ASAS?

What are the ANSYS Offshore Products?

EKM


• ANSYS Mechanical has been traditionally used for component analysis.

– We will look at capabilities specific to global analysis.

– Will discuss what are the plans for ASAS.

• ANSYS AQWA will be looked at in more detail here as largely offshore/marine related product.

ANSYS Offshore Update Scope


• For almost 40 years, ANSYS ASAS has been successfully used for analyzing a large variety of offshore structures subjected to wave, current and wind loading

– Many North Sea jacket structures have been designed with the aid of ASAS

• But

– Utilization outside of Europe limited

– Much duplication with mainstream Mechanical/MAPDL model

• Resulting in transfer of ANSYS ASAS unique solver technology to ANSYS Structural Mechanics products

– Never any long term scope for developing/supporting multiple FE products

– Recognition of ANSYS ASAS key features

Historical Perspective – ANSYS ASAS


• CAE requirements for Fixed Offshore structures:

‒ Variety of foundations ranging from concrete gravity-based to steel jackets

‒ Combined wave, current and wind loading

‒ Variety of local joint flexibility for tubular joints

‒ Seismic loading

‒ Soil-pile-structure and soil-pile interaction

‒ Range from shallow to deep water conditions

‒ Member and Joint Code Checking (e.g., API RP2A, AISC, ISO 19902.)

‒ Deterministic, spectral and time history fatigue

ANSYS ASAS Migration


• Software development is structured to reflect solutions to market problems

– Some solutions are common to all markets

– Others reflect specific application areas to a given market

• The major themes covering the development strategy for this presentation are:

– Safety of offshore structures.

– Alternative energy devices (specifically here offshore wind and wave energy systems).

– Workbench migration of existing technologies (specifically here ANSYS AQWA).

– Migration of global analysis capabilities to ANSYS Mechanical and MAPDL.

– Physics coupling.

On-going Development Themes


• Global Offshore Structures

– AQWA Workbench Integration

– AQWA Enhanced Environmental Conditions

– AQWA Frequency Domain Drag Linearization

– Extended Wave Loading in Mechanical

– Coupling of Mechanical with Third Party Aeroelastic Tools

– Design Assessment

14.0 Specifics


• Hydrodynamic Time Response system enhancements include – Fenders (similar to contact)

• Allows connections between 2 structures or between a structure and a fixed point

– Articulations (similar to joints)

– Connection points on structures now defined in AQWA, not in original geometry

Enhanced Productivity with Continuing AQWA Integration in Workbench

Offloading arm represented with series of typical articulations


AQWA Enhanced Environmental Conditions

• Introduction of multi-directional wave spectra allows more realistic modelling of real wave conditions, and is important for the accurate simulation of moored vessels and offshore platforms

– Almost any combination of wave spectra to be modelled in the solver modules LIBRIUM, DRIFT and the Hydrodynamic Time Response system in Workbench

• Gaussian formulated wave spectrum now available in the core solver and the Hydrodynamic Time Response system


• Inclusion of linearized drag on Morison elements in Diffraction/Radiation analysis

– Determined using a user specified wave spectrum.

– Computation of modified RAOs using the additional drag.

– SF/BM plots can now be made on models including Morison elements (and not just ship shaped).

– Used in design wave calculations for mixed models e.g. truss spar.

AQWA Frequency Domain Drag Linearization

Courtesy of Technip Offshore Finland


• Diffracted wave loading

– Provides simplified pressure loading from Hydrodynamics Diffraction systems (AQWA) onto MAPDL system

• Harmonic Wave Loading

– Regular wave loading now available for harmonic response analyses

– ANSYS FATJACK (for beam joint fatigue of framed structures) automatically reads the RST file data for harmonic load cases

Extended Wave Loading in Mechanical

Vessel Loading Transfer from AQWA to Mechanical Courtesy of Vuyk Engineering Rotterdam


• Aeroelastic coupling (for wind turbine support structures)

– Sequential • Allowing structural (ANSYS) and aeroelastic (3rd

party) analyses to be run independently

• Just use a provided MAPDL macro to write out input data for the aeroelastic analysis

– Fully coupled • Co-simulation of structural and aeroelastic tools

• Custom build of MAPDL required, with a macro to manage the data availability from and to MAPDL

Coupling Mechanical with 3rd Party Aeroelastic Tools for Offshore Wind Turbine Modeling

Images Courtesy of REpower Systems AG


Sequential Solution Example

MAPDL Substructure analysis to generate

matrices and load history for aeroelastic code

Aeroelastic software Wave-Wind Analysis

MAPDL Analysis of foundation structure

FATJACK Fatigue calculations

Beamcheck Strength calculations

Mass matrix Damping matrix Stiffness matrix External force time series

Top node force or displacement time series


Fully Coupled Solution

• Aeroelastic interface to MAPDL using the USER300 element. This element allows user defined stiffness, damping and mass data. This utilizes a shared memory dynamic link library, so requires modification to the aeroelastic code to facilitate the interface.


Design Assessment

• Design Assessment is a framework for post-processing of Mechanical results

• Provides out-of-the-box

– Load combinations

• Regulatory compliance for frame structures

• Joint fatigue

• User defined functionality allows access to external processing similar to MAPDL – customizable

• ANSYS BEAMCHECK (for member checks on framed structures) and ANSYS FATJACK now delivered with Mechanical installation (licensed separately)


Updates to Design Assessment

• Extended upstream capabilities permits wider application range

• Modal

• Harmonic Response

• Random Vibration

• Response Spectrum

• Explicit Dynamics


Expanded Result Access

Filtering of potentially invalid combinations can be suppressed to enable greater user control. This allows the user to access results not typically available in the base analysis.

Modal=No Beam Results

DA + “Allow all Available Results” allows beam results


Design Assessment for Advanced “User Defined Results”

• Design Assessment enables users to extend user defined results capabilities with:

• Expressions, including mathematical operators

• Coordinate systems, Units Systems

• Nodal, Element-Nodal & Elemental result types

• Units support for input parameters

• Results may be presented as contours, vectors or stress tensor form


• Previous slides have shown some of the developments undertaken to couple wave loading with structural applications

• Following are example case studies that show how ANSYS technology can be coupled to good effect to solve complex problems – system level solutions.

– Storage Vessel Design, combining CFD, Hydrodynamics and Structural aspects in one application.

– Riser Design, showing how various aspects of the riser problem can be solved using the ANSYS toolset.

Case Studies


Case Study Storage Vessel Design


Storage Vessel Design Effects of FPSO Movement

• Liquid-gas interface unstable

• Need to reduce sloshing to maintain separation efficiency

• What stresses are seen by components?

– Can we still use standard baffle configurations?

– Bolts and welds

– Fatigue loading

• Not something that’s easy to do experimentally!

– Potentially dangerous

– Significant cost of rig & instrumentation


Objectives

• Design study for a 12m long storage tank on board an FPSO

• Design considerations:

– Internal baffle arrangement to reduce sloshing

– Operational load characteristics

• Sloshing loading

• Fatigue

• Welds and bolts


Vessel Motion

x’ y’

z’

Non-accelerating motion

• Ship moving at fixed speed

• No waves or swell

• No acceleration force

• No sloshing!

Free motion

• Bow of the ship in a storm

• 3 Rotations

– Roll, Pitch & Yaw

• 3 Linear Accelerations

– Surge, Sway & Heave

• Sloshing expected!

x

y

z


• Hydrodynamic analysis with a given sea state provides motion profile for CFD and FEA

• Velocity motion profiles applied using Six Degree Of Freedom model in CFD solve

• accelerations could be applied directly to momentum equations

– Volume of Fluid model used to model gas-liquid interface in CFD solver

– Transient one-way FSI, surface pressures mapped from CFD analysis to FEA model

– Displacement profiles from Hydrodynamic solver applied to FEA model to account for inertia of solid structure

Methodology


Simulation Process

Step Solver Design Consideration Output Data

1 Hydrodynamic Asses ship hydrodynamic response to different sea states

Motion Profiles: Velocities for CFD Displacements for FEA

2 Computational Fluid Dynamics

Analyse baffle design to assess sloshing

Surface Pressure Profiles

3 Structural Finite Element

Analyse stresses to look at welds and bolt arrangements and fatigue loading

Velocity Profiles

Pressures & Displacements

Hydrodynamics CFD FEA


ANSYS Workbench Project


Hydrodynamic Analysis

• Motion Profile Output for all six motions, used for CFD and Structural FE models

• Displacements, Velocities and Accelerations


Computational Fluid Dynamics Analysis

Surface Pressure Profile used for Structural model


Structural FEA

• Pressure Loading ONLY

• Fluid inertia considered

• Fixed constraints to feet

• Inertia of solid structure ignored


Structural FEA with CFD Free Surface


Case Study Risers


Riser Systems

• Risers are the physical connectors between an oil and gas wellhead and the drilling or production platform (fixed or floating)

• Many different types

– Drilling, production

– Rigid, flexible, steel catenary, etc

– Attached, top tensioned, riser towers, etc

• Failure costs are high, both financially and environmentally


Riser Systems

• Floating systems are operating in deeper waters. Mooring and riser systems are a bigger proportion of the total system

• Vessel, mooring system and risers act as an integrated dynamic system

• Vessel motions coupled with slender structural members motions (mooring and riser)

• For physical model test very deep tank required


Riser Issues

• The analysis of risers represents a major technical challenge

• Extremely long

• Highly flexible

• Multi-physics requirements

– Mechanical (connections and welds)

– External hydrodynamic loads

– Internal flow assurance

• Usually in groups and subject to interaction effects

• Risers are subject to vortex- induced-vibrations (VIV) among one of the the most complex of fluid-structure interaction problems


How We Can Solve Riser Problems

The ANSYS product range provides the toolkit for solving riser design requirements

• Mechanical model for looking at connections (detailed), riser string behavior (global), tensioning systems, etc.

• Hydrodynamic model for investigating effects of riser bundles on floating vessel response.

• Fluids model for flow assurance, VIV, interference effects.

But, at the moment they do not all act in an integrated manner for this type of application. Further work is necessary to enable best in class capabilities in this important area.


Umbilical, Risers & Flexible Piping

• Geometry built in DesignModeler:

– Core tubing

– 6 helical tubes wrapped around core

– External insulation

• Loads:

– Bent to 36’ radius

– Hydrostatic loads

– End tension

– Gravity


• Release 14.0 represents the continuing development of capabilities and technologies to solve problems commonly encountered in the Offshore Oil & Gas sector.

• The range of physical models enables differing levels of simulation, offering analyses from the macro to the system level.

• Improved productivity through continuing integration of AQWA technology into Workbench

• Greater exposure of offshore specific structural applications through the integration of ANSYS ASAS technology into ANSYS Mechanical and MAPDL

Conclusions

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ANSYS Offshore Products 14.0 Update · PDF fileVessel Loading Transfer from ... Wave-Wind...

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