SimTank is a CFD tool chain that has been developped and perfected at CRAIN for years. It allows a quick and efficient evaluation of drag and efforts for sailing yachts and so is an efficient decision tool for hull design.

SimTank is :

Reliable : results have been compared with tank test for many projects
Fast : specific solutions allow to reduce computationnal time
Affordable : it has been optimized over the years to reduce study time
Proven : it has been already used for many different projects

Method

Bare hull

We use a RANS CFD code for bare hull effort calculation. This code has been designed specifically to compute flow around vessels going though the free surface and is so particularly efficient for yacht calculations.

It offers a fully coupled velocity-pressure algorithm that speed up calculation time and an enhanced method for friction drag evaluation that allows to dramatically reduce mesh size.

We have been using this software since 2000 and comparison with tank test results have shown good results over a wide range of hull shape.

This code offers many improvements on panel code, and is able to compute :

Viscous drag
Overhang effects
Turbulent wake
Immersed transom drag

Appended hull

Since RANS CFD codes have not yet proven to be efficient for appended hull, due to their inhability to compute accurately the lift and drag components of appendages, we use a panel code to evaluate the appendage wave drag interaction.

The appendages parasit drag is then estimated with XFoil from MIT, depending on Reynolds number and ambiant turbulence level.

Yacht total drag is then calculated using bare and appended hull result to lead to the complete drag and lift matrix.

Already tested

IACC
IMS
Transpac 52'
Superyacht
Open 60' monohull (ORMA class)
Open 60' multihull (IMOCA class)
Maxi multihull

Our customers

Andrieu Yacht Design, Marc Lombard Architecture Navale, Luca Brenta Yacht Design, Van Pethegem Lauriot Prevost Yacht Design, Berret Racoupeau Yacht Design, Briand Yacht Design, Felci Yacht Design, Multiplast, Gilles Ollier Design Team, International Technical Commitee (ITC),

All of them have already trusted our office.

America's Cup Project

We have been involved in the following projects :

2007 : China Team
2003 : Areva Challenge
2000 : 6th Sens - Défi Bouygue Telecom - Transiciel
1995 : France America 95
1992 : Le Défi Français

Typical studies

The following table shows some typical services that we can offer, using a 80 000 point mesh for bare hull RANS calculation. The study include meshing, calculations, extrapolation and report.

Study	Speed	Heel	Lift	Delivery time
Bare hull - Upright drag	x8	x1	No	3 days
Bare hull - Drag matrix ⁽¹⁾	x8	x6	No	5 days
Appended hull - Drag matrix	x8	x1	Yes	4 days
Appended hull - Drag matrix⁽¹⁾	x8	x1	Yes	7 days

(1) : This matrix requires around 30 runs, other data are extrapolated.

Refined mesh

In case of very demanding flow calculation (such as flow separation, huge pressure gradient,...), we can use a 400 000 point mesh for RANS calculation.

This kind of mesh can offer better results in difficult cases but calculation time is much longer.

Study	Speed	Heel	Lift	Delivery time
Bare hull - Upright drag	x8	x1	No	5 days
Bare hull - Drag matrix ⁽¹⁾	x8	x6	No	15 days

(1) : This matrix requires around 30 runs, other data are extrapolated.

Other services

We are also able to carry out the following studies : evaluation and influence of sailing trim, yaw balance under sails, appendages efficiency and optimization, VPP works...

Information and contact

For further informations or quotation, visit our performance page

Contact us

Jérôme Védrenne

CRAIN, 52 rue Sénac de Meilhan, F-17000, La Rochelle

Tel : +33 (0)5 46 44 87 17