# Sailboat physics simulation

Discussion in 'Hydrodynamics and Aerodynamics' started by omarreis, Nov 23, 2016.

1. Joined: Nov 2016
Posts: 2
Likes: 0, Points: 0, Legacy Rep: 10
Location: Sao Paulo

### omarreisNew Member

Hi. I'm not a boat designer, but a computer programmer and sailor.
I wrote code that simulates some physical aspects
of sailboats. It uses box2d library (physics in 2D)

The SailboatBox2D project can be found at:

https://github.com/omarreis/SailboatBox2d/wiki
https://github.com/omarreis/SailboatBox2d/

also a video at:

https://youtu.be/50Omdka_yx8

The sails in this code are simulated by a bunch of flat plates,
connected by revolute joints, forming a chain.
This gives them a movement that is about right.

The force the wind applies to the sail is trough these plates.
I calculated lift and drag for each plate as if they were slender,
flat plates, free standing in undisturbed flow of air.

I understand this is not a good model, as the fact that sail segments
are disposed together in a single, curved shape is obviously important,
and it is not currently taken into account.

The bad side of this unrealistic model is that the sails
have large drag even when they are flapping.

My question is: Is there a way to calculate the forces on a sail,
based on the wind conditions and the shape of the sail ?
I mean, a loose sail, with more draft, is supposed to
receive a larger force than a flat one, but how
can I quantify that ?

Omar

2. Joined: Oct 2008
Posts: 7,766
Likes: 1,658, Points: 113, Legacy Rep: 2488
Location: Japan

Omar

Welcome to the forum.

Before you go any further, you should have a read of this first, to give you an idea of the task ahead:

#### Attached Files:

• ###### JMST sailing paper.pdf
File size:
2.5 MB
Views:
715
3. Joined: Nov 2016
Posts: 2
Likes: 0, Points: 0, Legacy Rep: 10
Location: Sao Paulo

### omarreisNew Member

Wow. Lots of information in this PDF.
I hope I can understand it !

Thanks

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