Adaptation of STAR-CCM+ NumericalAdaptation of STAR-CCM+ NumericalWave Tank to an Offshore FloaterDesign Tool

STAR Global Conference 2013STAR Global Conference 2013

18 MARCH 2013

Agenda

Introduction

Design Spiral

Requirements Requirements

Technology Readiness / Gap

Euler Overlay Method

Success Stories

Three Generations of Spar Platforms

CLASSIC TRUSS CELL TRUSS

Technip has delivered 14 out of the 19 spars worldwide, in a water depthrange of 590 – 2,382 meters using both dry and wet tree completions.

Technip Presentation3

range of 590 – 2,382 meters using both dry and wet tree completions.Four more spars are under design/construction by Technip

Offshore Floaters

WindFPSO/FLNGSparSemi-submersibleUnideck®TPG 500 TLP

Supporting subsea system

Technip Slide Library4

Supporting subsea systemOperations in harsh environmentSurvive and protect crew / equipments in extreme environmentsSmall Motion

Design Spiral of Offshore Floater Design

GlobalGlobalPerformance

WAMIT / MLTSIMMotion Solver

Model Test6 month afterproject start

Hull Sizing Calibration

Air gap / green water / Slamming

Design Spiral of Offshore Floater Design with CFD

GlobalGlobalPerformance

Hull SizingHull Sizing

CFD

Validation

CFD

ValidationModel Test

before project

Less uncertainties

Shorter design period

More design optimization

Expectations on Design Tools

Accuracy

Tolerance < 10%

Preferably conservative side Preferably conservative side

Robustness

No crash

No surprise

Predictable schedule

Speed (Screening Tool)

Less than 10 min for a short-term (3-hr) simulation

Runtime (Final Evaluation Tool)

One run < 12 hr for diagnostic runs

One run < 24 hr for production runs

Existing Design Tools

Nonlinear Time-Domain Motion (MLTSIM)

Hydrodynamic coeff. From WAMIT

Morison drag Morison drag

Nonlinear Froude-Krylov force

Large amplitude formulation

Mooring / SCR Modeling

Quasi-Static Analysis (FMOOR)

Catenary model Catenary model

5-10 min for 3-hr simulation

Screening Tool

Model Test

MLTSIM Calibration

Run up / Air Gap / Green Water

8

Ringing

Design Tools with Numerical Wave Tank

Nonlinear Time-Domain Motion (MLTSIM)

Hydrodynamic coeff. From WAMIT

Morison drag Morison drag

Nonlinear Froude-Krylov force

Large amplitude formulation

Mooring / SCR Modeling

Quasi-Static Analysis (FMOOR)

Catenary model Catenary model

5-10 min for 3-hr simulation

Screening Tool

Numerical Wave Tank

MLTSIM Calibration

Run up / Air Gap / Green Water

9

Ringing

Technology Readiness

STAR-CCM+ Features

Free-surface capturing

Moving mesh technique Moving mesh technique

DFBI

Embedded DFBI X

Overset X

Powerful built-in pre/post processors

Hardware Hardware

In-house cluster (144 cores)

TACC Stampede ( > 10,000 cores)

1-hr simulation in one day (Semi-submersible) 1-hr simulation in one day (Semi-submersible)

Technology Gap / Solution

Wave Input

5th-Order Stokes Wave

Good for deep waterFully-nonlinear wave models Not good for shallow water extreme waves

Random wave input does not meet industry best practice

Random seeding

Wheeler stretching

Fully-nonlinear wave models

In-house wave codes Wheeler stretching

Many users were using customized user functions

Far-Field Closure

No wave-absorbing mechanism in up-wave side

Larger domain required

Numerical damping sometimes help

Euler-Overlay Method

Mooring / Riser Modeling

Built-in catenary model

Good for tendon and taut mooringIn-house Catenary / Rod

Good for tendon and taut mooring

Not good for SCRs and non-taut mooring

No dynamics

In-house Catenary / Rodmodels

Euler Overlay Method

History

Bai & Yeung (1974): Matching FE/BE solution with analytic solution

Kim & Bai (1991): Nonlinear radiation problem (Matching)

Kim, Kyoung, Ertekin & Bai (2003): Nonlinear diffraction (Overlaying)

Kim, Rajeev & O’Sullivan (2011): Nonlinear diffraction (CFD, Overlaying)

Kim, Read & O’Sullivan (2012): Nonlinear diffraction (STAR-CCM+, Overlaying)

Far-Field Solution

Euler solution

Overlaying

Boundary condition Boundary condition

Momentum and volume fraction

source / sink term in blending zone

12

Long-Crested Wave and a Vertical Column

2D Euler Wave Flume 2D Euler Wave Flume

Length: 105 m

CFD Domain

Length: 2 m

13

Ringing Analysis of a GBS (Short-CrestedIrregular Wave)

Dynamic amplification of structural load due toresonant response of structure to higher-harmonicload

Ringing Response of TLP Tendons

Animation of simulated TLP motion and wave elevation(left).

Time history (lower left) and power spectrum (lowerright) of tendon tension. Blue curve is from model testright) of tendon tension. Blue curve is from model testand red curve is from CFD simulation. Leeside tendontension is mostly from wave frequency response (wavemodal frequency = 0.061 Hz). Weather-side tendontension shows strong ringing response at aroundheave and pitch natural frequency of the TLP (0.22 Hzand 0.23 Hz).

Leeside tendon tension

Weather-side tendon tension

Semi-Submersible Motion Simulation

Mooring and Riser Model

Look-up table for SCR and Mooring Force

Heave RAO from White-Noise Wave Test

1-hr simulation

16 hours with 640 cores

WAMIT

Conclusions / Path Forward

NWT Technology Readiness

STAR-CCM+

Euler Overlay Method

Success Stories

Air Gap / Green Water Analysis for Spar Air Gap / Green Water Analysis for Spar

Ringing Analysis for GBS and TLP

Motion Analysis for Semi-Submersible

Improvements

Wave models

Mooring / riser modeling Mooring / riser modeling

Building the Future

Validation and Improvements through JIP Validation and Improvements through JIP

Recommended Practice