Dr Ignazio Maria Viola

ignazioviola.com

Dr Ignazio Maria Viola

Presentation

Ignazio Maria Viola’s specialist skills and experience are in numerical and

experimental fluid dynamics. His main research focus is high-performance

sailing yachts and, in particular, sail aerodynamics and hull hydrodynamics.

His research portfolio also includes the aerodynamics of trains, cars, longspan

bridges and tall buildings.

In 2008 he successfully completed a CFD simulation with a record breaking

grid of more than one billion cells and in 2010 he performed the world’s

first direct pressure measurements on a full-scale spinnaker.

Ignazio has more than 40 peer reviewed scientific publications on the fluid

dynamics of yachts and super yachts.

Ignazio Maria Viola

MEng, PhD, CEng, EUR ING, MRINA, MSNAME

School of Marine Science and Technology

Newcastle University

Lecturer in Naval Architecture

Chair of the Computational Fluid Dynamics Workgroup

Principal Expertise

Sail Aerodynamics

Hull Hydrodynamics

Background

2010 - present

Lecturer in Naval Architecture

Newcastle University

2009 - 2010

Post Doctoral Fellow

Yacht Research Unit, Auckland, official

scientific advisor of Emirates Team

New Zealand

2008

One-Bllion-Cell project funded by

the European Union

2004 - 2007

PhD granted by Luna Rossa Challenge,

Politecnico di Milano Wind Tunnel (Italy)

2001 - 2003

Project Manager, then

Mass Production Director

MAS yacht yard (Como, Italy)

1995 - 2001

Bachelor’s and master’s degree

in Naval Architecture,

Università degli Studi di Genova (Italy)


Experimental Sail Aerodynamics

Ignazio has 10 years experience in wind tunnel testing and has worked in two of the most prestigious

wind tunnels in the world: the Twisted Flow Wind Tunnel of the Yacht Research Unit (Auckland) and the

Politecnico di Milano Wind Tunnel. He has also investigated pressure distributions on full-scale sails with

on-water tests, which led to important breakthroughs in sail aerodynamics.

Pressure Measurement on Sails

Since 2009 Ignazio has performed

pressure measurements on both

upwind and downwind sails. In 2010

he undertook the world’s first on-water

pressure measurements on a fullscale

downwind sail. These tests

were performed on AC33-class sails

designed for Emirates Team New

Zealand.

Pressures, forces and flying shapes

were simultaneously measured on

mainsails, headsails and asymmetric

spinnakers. All tests were performed

both on-water at full-scale and in a

wind tunnel at model-scale.

The flying shapes were used to

perform numerical analysis which were

validated with the measured pressure

distributions.

Wind Tunnel Tests

for the Luna Rossa

From 2004 to 2007 Ignazio conducted

more than 5,000 wind tunnel tests for

the America’s Cup challenger Luna

Rossa. He tested both upwind and

downwind conditions, collaborating

with some of the world’s top fluid

dynamicists and sail designers.

Pressure measurements are a

very efficient research tool in sail

aerodynamics. Wind-tunnel tests

allow highly-accurate validation of

numerical codes, while full-scale tests

-4

-3

-2

-1

Cp 0

+1

Upwind condition

Headsail

Leading

edge bubble

Trailing edge

separation

Headsail

Mainsail

Leading

edge bubbles

Mast Mainsail

Aerodynamic Models for Velocity Prediction Programs

From 2005 to 2007 Ignazio performed

for the ITTC (ORC) one of the largest

wind-tunnel systematic investigations

on sail aerodynamics, where a wide

range of sails, planforms and sailing

conditions were tested.

The results were used to design the

new aerodynamic model of the IMS

rating system.

Politecnico di Milano Wind Tunnel

allow the sail trim to be optimised

in real-time while also providing

extensive indications for improved

sail design.

-4

-3

-2

-1

Cp 0

+1

Downwind condition

Asymmetric Spinnaker

Trailing edge

separation

Leading edge

bubble

Spinnaker

Leading edge

bubble

Mast Mainsail

IMS and EXP coefficients vs AWA

In 2003 Ignazio designed the Twisted Flow Device for the Politecnico di Milano

Wind Tunnel, the largest of its kind in the world, which he used until 2008 to

perform wind tunnel tests for several yacht and sail designers.


Computational Sail Aerodynamics

Computational Fluid Dynamics (CFD) has become one of the most powerful tools in yacht and sail design.

Ignazio has collaborated widely with major CFD software companies, including ANSYS and CD-adapco,

to significantly extend CFD capabilities.

High Grid Resolution CFD

In 2008 Ignazio undertook a research

project to investigate CFD capabilities

with high grid resolution, funded by the

EU. He performed the largest grid used

so far with more than one-billion cells,

modelling a yacht sailing downwind.

The research allowed investigation

of the advantages of using very high

grid resolution CFD in yacht design

process.

Running on 512 CPUs, the job occupied

2 terabytes of RAM for just over a week

to complete the calculation of flow

velocities and pressures.

Reliable CFD Validation using Pressure Distributions

The unique pressure measurements

performed by Ignazio on model-scale

and full-scale sails allowed numerical

simulations to be accurately validated.

When the pressure distribution

is correctly modelled, numerical/

experimental differences in the

aerodynamic forces are below 1%.

While Reynolds Averaged Navier

Stokes (RANS) techniques are used to

compute global aerodynamic forces,

more time-consuming and more

Yacht Research Unit Twisted Flow Wind Tunnel

accurate techniques such as Large

Eddy Simulations (LES) and Detached

Eddy Simulations (DES) are used to

investigate the local flow behaviour.

For instance, the interaction between

the atmospheric boundary layer

turbulence and the laminar-to-turbulent

transition in the leading edge bubble,

which has a significant effect on the

maximum drive force achievable, can

be investigated using LES.

In 2009 and 2010 Ignazio continued his research on sail aerodynamics at the

Twisted Flow Wind Tunnel of the Yacht Research Unit (Auckland), which is the

scientific advisor of Emirates Team New Zealand.

ANSYS news release (SOUTHPOINTE, PA, November 17th , 2008):

“ANSYS BREAKS 1 BILLION CELL BARRIER”

“ANSYS [...] today announced the first engineering group that worked with

commercial simulation of more than the Luna Rossa Challenge team for

1 billion computational cells using the 2007 America’s Cup yacht racing

software from ANSYS — A significant competition, conducted the landmark

milestone for the Company and the simulation during August 2008 to

industry.

investigate the aerodynamics of an

An Italian research team headed by

Ignazio Maria Viola, a member of the

America’s Cup yacht.”

Virtual Wind Tunnel

From 2003 to 2007 Ignazio worked with

the Luna Rossa to develop the sails

which were used by the team in the

32 nd America’s Cup. RANS simulations

with more than 30 million cells were

performed on up to 512 CPUs.


Hull Hydrodynamics

Ignazio has expertise in numerical hydrodynamics, modelling a wide

range of yacht types: from IACC-V5 to Volvo Ocean Race yachts,

from maxi racers to luxury power yachts, towards skiffs and light

displacement powerboats.

Virtual Towing Tank

In a joint project with CD-adapco and an

America’s Cup team, Ignazio showed

that CFD can be used to predict

hydrodynamic resistance, sink and trim

of a fully appended yacht with the same

accuracy as towing tank tests.

Two IACC-V5 class yachts were

modelled with appendages in a free to

sink and trim condition.

TH04

[metres]

TH06

[metres]

TH04 TH06

The numerical/experimental comparison

showed differences in the resistance

of the order of 1%. The sink and trim

variation with the boat speed have been

computed with an accuracy of ±0.03

deg and ±0.04% of the water length,

respectively.

Cutting Edge Applications in Numerical Fluid Dynamics

CFD allows quantitative measurements

of yacht performance in sailing

conditions which are difficult to analyse

with physical experiments.

CFD can model yacht motion with

6 degree of freedom, resistance in

regular and random waves, dynamic

loads due to breaking waves and

waves flushing the deck and slamming

loads.

Ignazio works to improve the state of

the art of CFD applications. Highly

reliable CFD modelling of these

dynamic effects is therefore one of his

key research goals.

CD-adapco press room (New York

and London. September 30 th , 2010):

“Research project demonstrates

accuracy of CFD prediction for

America’s Cup Yacht Design”

“A research project, recently

completed by Dr. Ignazio Maria

Viola at the Yacht Research Unit

of the University of Auckland, New

Zealand, has demonstrated that the

resistance of America’s Cup Yachts

can be predicted with a high level

of accuracy using CD-adapco’s

engineering simulation tool STAR-

CCM+.”

Hull resistance [N] of TH04

versus boat speed [Knots]

IACC-V5 class yacht modelled with 3 degree of

freedom: sink, trim and roll.

Both the upwind and the downwind conditions

have been modelled for several wave conditions.

Contact details

School of Marine Science

and Technology,

Newcastle University

Armstrong Bld, Queen Victoria Rd

Newcastle upon Tyne

NE1 7RU, United Kingdom

+44 (0) 191 222 8101

ignazio.viola@ncl.ac.uk

www.ncl.ac.uk/marine

www.ignazioviola.com

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