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-   -   Flow 3D for beginners (http://www.cfd-online.com/Forums/flow-3d/67861-flow-3d-beginners.html)

Jim August 28, 2009 11:56

Flow 3D for beginners
 
Hi,

I am a recently graduated mechanical engineer and I'm use to FEM software like SolidWorks to make static study on parts. I'm now on a new project that consist of the design of a new type of hull. I create the hull in SolidWorks and export it in .stl. I would like to import it in flow 3d to simulate the water flow, see the wave created and calculate de drag coefficient or drag force. I am a total beginner on that software so can somebody give me some advice, some tips and procedure on that kind of study.

Thks

stefmascio September 1, 2009 10:42

it will not be so difficult. The basic guidelines can be: you will need the GMO model active, and the turbulence too. In the "meshing and geometry" tab, once loaded the .stl, you have to define it as a moving body, with its mass and CG center. Probably you'll have to use a multi-block mesh, nested eachother, with the inner one quite fine (cell = 1-2% of the length of the hull) and the outside one large. Finally just give the motion to the water, with the speed that you want.

Jim September 1, 2009 11:59

Thks for you information but there is still a lot of things I don't understand.

1)
Moving and deforming obects menu
--> What is the difference between implicit and explicit?

2)
Viscosity and turbulence menu
--> What are the settings of my study?

3)
How can I generate wave and see the effect on the hull?

4)
I'm not sure to understand your meshing advice (large for outer side fine for inner side).

5) How can I generate a model with a water region and an air region?

Thks for all your advices. I did a lot of FEM study on parts before but it is my first CFD project.

stefmascio September 2, 2009 08:18

1. for hull simulations, choose the implicit method. (the explicit is unstable)
2. turbulence RNG
3. I suggest to start with a steady (no wave) simulation. When all is perfect you can change the inlet boundary condition with a wave boundary condition.
4. for example use 3 mesh blocks, one inside the other, centered on the hull: the external mesh block with a large cell, the most inner mesh block with a small cell size.
5. in the 'Initial' tab, set the fluid height as the z-coordinate of your water line. You don't need to define the air, the nice thing of FLOW-3D is that you can completely ignore the air.

anindya September 23, 2009 20:11

I am not sure how you are running a CFD analysis without knowing some of the fundamental and basic stuff. You should first study cfd (there are lots of good books) and then start with the simulation.


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