CAE NAVAL & OFFSHORE 2010

Why Consider a Multiphysics

Solution from ANSYS?

Ricardo Damian, M.Sc.

Account Manager

May 18th 2010

• The real world is a multiphysics world!

• Designs depend on multiphysics phenomena

• Designs require small error margins

• Physical testing is too costly

RF MEMS SwitchImage courtesy EPCOS NL and Philips Applied Technology

SSwiittchh

����� ������ ���������������

The power of MultiphysicsMultiphysics

Simulating under realreal--worldworld

multiphysics conditions!

The power of MultiphysicsMultiphysics

Simulating under realreal--worldworld

multiphysics conditions!

����� ������ ���������������

THE PROBLEM:THE PROBLEM:

• Offshore operations can loose a significant

revenue for even few days of down time;

• Gas turbine powers electrical generators

and NG compressors;

• The gas turbine exhaust stack is a 10 m

high welded sheet metal structure;

• It conducts the exhaust hot gases flow at

540� C up to 180 m/s;

• Field measurements indicated extreme

vibrations of 20 Hz;

• Occurrence of fatigue cracks at the lower

cone;

• Tears could shut down the operation, due to

safety reasons;

����� ������ ���������������

THE SOLUTIONTHE SOLUTION:

• Pre-stressed model analysis:

– First natural frequencies 15-25 Hz

– Maximum amplitude at the lower cone

• Transient CFD Study, testing turbulence models:

– U-RANS, LES, DES;

– Low frequencies: U-RANS chosen, time efficient;

• Low deflections, 1-way FSI Study:

– ANSYS CFX: transient pressure field;

– ANSYS Mechanical: dynamic vibration & fatigue

– Time step: 1 ms;

– 1000 time steps;

– Run time ~12hs, 8 cores workstation;

• Final design (D1):

– Reduced flow recirculation zone;

– New shape increased the first natural frequencies;

– Thermal insulation damping increased;

– Total vibration level reduced by 80%;

����� ������ ���������������

����� ������ ���������������

FINAL REMARKSFINAL REMARKS:

• Real-World representation: The FSI study

correctly represented the VIV allowing the

engineers to understand this multiphysic

problem and to test new scenarios;

• Knowledge capture: Quick and reliable

procedure to evaluate future stack designs;

• Single environment:

ANSYS Workbench

+ ANSYS CFX

+ ANSYS Mechanical

• Comprehensive Multiphysics: Easy to

setup, no need to write transfer routines,

predefined defaults, design process

compression & automation;

Only ANSYS provides comprehensive multiphysics!Only ANSYS provides comprehensive multiphysics!

Sinaval

�������������������������������