Dam break problem

sega · April 19, 2008, 11:32

I have some questions regarding the dam break problem in general.

I want to simulate the basic dam break problem.
It's similar to the one used in the tutorials, but without the barrier.

I have data to compare from experiments (Martin & Moyce, 1951) and two numerical calculations (Griebel et al., 1995 and Ramaswamy, 1987).

The numerical soultions are both caluclatet for different Reynolds-Numbers.
The Reynolds-Number for this problem is known as
Re = H*sqrt(g*H) / nu
Therin H equals the initial High of the water column, g gravity and nu the dynamic vicosity.

And now my first question.
Which dynamic vicosity is meant to play a role in this problem. I suppose it must be the one for the water. So to compare the solutions obtained at a specific Re-Number I can calculate the appropriate nu and define it in OpenFOAM for the water-phase.

Now I have TWO problems left.

1. What Do I with the second nu?
I don't think it's free to chose for the second phase.
2. What about the surface-tension?
I have no idea about what to specify. Is it possible to derive it from the Re-Number? Or from the combination of phases?

Thanks in advance!

fugu · April 19, 2008, 16:44

I never got the chance to get the original Martin & Moyce paper... but I read a description of the
experiment somewhere else and I believe they used water and air. Then they just adimensionalized their results.
If I remember correctly the size of the experimental setup was quite big. I believe you can omit surface tension and give it a shot.
Hope this helps

sega · April 20, 2008, 09:54

Ok, I used the properties for air and water at constant temperature and zero surface tension (sigma).

The movement of the water columns looks familiar.

But to compare it with the experiment there is some post-processing to do.
I have posted my questions in the post-processing-forum:
http://www.cfd-online.com/OpenFOAM_D...tml?1208699365

sega · April 20, 2008, 10:03

The experimental data in the original Martin & Moyce is found here:
http://www.jstor.org/sici?sici=0080-4614(19520304)244%3A882%3C325%3APVAESO%3E2.0.CO%3B2-7

I'm able to access the paper trough my university account.

April 19, 2008, 11:32	I have some questions regardin	#1
sega Senior Member Sebastian Gatzka Join Date: Mar 2009 Location: Frankfurt, Germany Posts: 729 Rep Power: 20	I have some questions regarding the dam break problem in general. I want to simulate the basic dam break problem. It's similar to the one used in the tutorials, but without the barrier. I have data to compare from experiments (Martin & Moyce, 1951) and two numerical calculations (Griebel et al., 1995 and Ramaswamy, 1987). The numerical soultions are both caluclatet for different Reynolds-Numbers. The Reynolds-Number for this problem is known as Re = Hsqrt(gH) / nu Therin H equals the initial High of the water column, g gravity and nu the dynamic vicosity. And now my first question. Which dynamic vicosity is meant to play a role in this problem. I suppose it must be the one for the water. So to compare the solutions obtained at a specific Re-Number I can calculate the appropriate nu and define it in OpenFOAM for the water-phase. Now I have TWO problems left. 1. What Do I with the second nu? I don't think it's free to chose for the second phase. 2. What about the surface-tension? I have no idea about what to specify. Is it possible to derive it from the Re-Number? Or from the combination of phases? Thanks in advance! __________________ Schrödingers wife: "What did you do to the cat? It's half dead!"

April 19, 2008, 16:44	I never got the chance to get	#2
fugu New Member Luca Liberti Join Date: Mar 2009 Location: Rome, Italy Posts: 22 Rep Power: 17	I never got the chance to get the original Martin & Moyce paper... but I read a description of the experiment somewhere else and I believe they used water and air. Then they just adimensionalized their results. If I remember correctly the size of the experimental setup was quite big. I believe you can omit surface tension and give it a shot. Hope this helps

April 20, 2008, 09:54	Ok, I used the properties for	#3
sega Senior Member Sebastian Gatzka Join Date: Mar 2009 Location: Frankfurt, Germany Posts: 729 Rep Power: 20	Ok, I used the properties for air and water at constant temperature and zero surface tension (sigma). The movement of the water columns looks familiar. But to compare it with the experiment there is some post-processing to do. I have posted my questions in the post-processing-forum: http://www.cfd-online.com/OpenFOAM_D...tml?1208699365 __________________ Schrödingers wife: "What did you do to the cat? It's half dead!"

April 20, 2008, 10:03	The experimental data in the o	#4
sega Senior Member Sebastian Gatzka Join Date: Mar 2009 Location: Frankfurt, Germany Posts: 729 Rep Power: 20	The experimental data in the original Martin & Moyce is found here: http://www.jstor.org/sici?sici=0080-4614(19520304)244%3A882%3C325%3APVAESO%3E2.0.CO%3B2-7 I'm able to access the paper trough my university account. __________________ Schrödingers wife: "What did you do to the cat? It's half dead!"

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