Size ration in a 2D analysis

Marcus.filho · October 22, 2013, 09:16

Dear all,

I´m conducting a 2D analysis of a spillway to have some preliminary results and I ran into a doubt.

When we ahave a 3d mesh there are certain size ratio relationships we must follow in order to have good results. How does that work in a 2D mesh? For example, if I have a 2D analysis in the XZ plane with cels with 0.25m by 0.25m, can I have one cell in the Y direction 1m wide or is is better to have a 0.25m cell in the Y direction as well? Does the size ratio matter in this case?

I hope I made myself clear. Thank you in advance.

Marcus

JBurnham · October 22, 2013, 11:41

The size of the cell in the 2-D direction doesn't matter. FLOW-3D tracks volume of flow, so if the y-direction cell size is 1 m, then it makes converting 3-D volumes and 2-D areas easier.

Marcus.filho · October 22, 2013, 20:27

Thank you Jeff. So it is actually a good practice in 2D analysis always to have a 1 meter size cell in the dimension which is not beeing modeled?

JBurnham · October 27, 2013, 23:38

Yeah. It's a good thing, at least for interpreting the results. If it's a 3-D model, cubic cells are better, but 2-D it doesn't matter.

October 22, 2013, 09:16	Size ration in a 2D analysis	#1
Marcus.filho New Member Marcus Fernandes Araujo Filho Join Date: Sep 2013 Posts: 10 Rep Power: 13	Dear all, I´m conducting a 2D analysis of a spillway to have some preliminary results and I ran into a doubt. When we ahave a 3d mesh there are certain size ratio relationships we must follow in order to have good results. How does that work in a 2D mesh? For example, if I have a 2D analysis in the XZ plane with cels with 0.25m by 0.25m, can I have one cell in the Y direction 1m wide or is is better to have a 0.25m cell in the Y direction as well? Does the size ratio matter in this case? I hope I made myself clear. Thank you in advance. Marcus

October 22, 2013, 11:41		#2
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	The size of the cell in the 2-D direction doesn't matter. FLOW-3D tracks volume of flow, so if the y-direction cell size is 1 m, then it makes converting 3-D volumes and 2-D areas easier. Marcus.filho likes this.

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October 22, 2013, 20:27		#3
Marcus.filho New Member Marcus Fernandes Araujo Filho Join Date: Sep 2013 Posts: 10 Rep Power: 13	Thank you Jeff. So it is actually a good practice in 2D analysis always to have a 1 meter size cell in the dimension which is not beeing modeled?

October 27, 2013, 23:38		#4
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	Yeah. It's a good thing, at least for interpreting the results. If it's a 3-D model, cubic cells are better, but 2-D it doesn't matter.