Flow 3D for beginners

Jim · August 28, 2009, 11:56

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.

August 28, 2009, 11:56	Flow 3D for beginners	#1
Jim New Member Jim Join Date: Aug 2009 Posts: 2 Rep Power: 0	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

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September 1, 2009, 10:42		#2
stefmascio Member Stefano Join Date: Mar 2009 Posts: 59 Rep Power: 17	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.

September 1, 2009, 11:59		#3
Jim New Member Jim Join Date: Aug 2009 Posts: 2 Rep Power: 0	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.

September 2, 2009, 08:18		#4
stefmascio Member Stefano Join Date: Mar 2009 Posts: 59 Rep Power: 17	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.

September 23, 2009, 20:11		#5
anindya New Member Anindya Sengupta Join Date: Apr 2009 Posts: 2 Rep Power: 0	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.