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-   -   sediment scour (https://www.cfd-online.com/Forums/flow-3d/108400-sediment-scour.html)

 pyxbird October 22, 2012 20:28

sediment scour

All dears,
Hi, I am trying to use sediment scour model to simulate the scour patter around a vertical cylinder under steady flow. And here are my quetions:
1. I know the meaning of critical and cohesive sediment fration, but I don't know how to define the values of them.
2. As we all know, we can define the seabed by--initial--fluid region--the sediment concentration--packed, here the value of packed=density of the sand(for example 2.65)*solid fraction of the sediment? And if it is true, so how to define the value of solid fraction of sediment(1? or 0.9?and so on).
3.In the fluid region, we also need to define the fraction of the fluid, if the solid fraction I input is 0.9, so the fraction of the fluid should be 0.1 of 1? When I choose 0.1, after the simulation is run the fluid above the seabed drops straightly down to the "seabed", but when I choose fraction of fluid=1,there is no problem, but I don't think it is reasonable(can there be such large amout of water in "seabed"?), so how to define the value of "fraction of fluid"?
4.After the simulation is done, how can I see the flow pattern in the tab "Analyze"? Is it like this: iso-surface--packed sediment concentration; color variable--strain rate? But I can't find more detailed information, for example the scour depth.
I will be grateful is someone can help me.

 JBurnham October 23, 2012 10:59

FLOW-3D v9.4.x includes packed sediment depth and rate of change in depth as output variables that can be used as the color variable when plotting packed fraction as the iso-surface. If you have an earlier version than that, you may have to experiment to find a good way to plot.

 JBurnham October 23, 2012 11:02

The solid fraction of the initial regions is the same as the 'maximum packing fraction' defined on the Physics dialog for the scour model. The different proportions of sediment are used to calculate the fractions of each species in that already-known solid fraction. Always set the fluid fraction = 1.0; even in the initial fluid regions: the sediment (both suspended and packed) is considered a two-phase mixture fluid, and that fluid must be 100% present (F = 1) in all submerged cells, otherwise there will be many pressure failures and collapse of the fluid.

 pyxbird October 23, 2012 20:00

Quote:
 Originally Posted by JBurnham (Post 388136) The solid fraction of the initial regions is the same as the 'maximum packing fraction' defined on the Physics dialog for the scour model. The different proportions of sediment are used to calculate the fractions of each species in that already-known solid fraction. Always set the fluid fraction = 1.0; even in the initial fluid regions: the sediment (both suspended and packed) is considered a two-phase mixture fluid, and that fluid must be 100% present (F = 1) in all submerged cells, otherwise there will be many pressure failures and collapse of the fluid.
Thank you JBurnham, you have helped me many times.:)

 mahdi1 April 25, 2013 05:49

Hello pyxbird & JBurnham

I simulated a channel with movable bed by v10.
Could you please tell me that how can I take a plot of bed deformation and also How can I obtain maximum depth score in results file?

I would be thankful if you help me.

 mahdi1 May 2, 2013 15:20

Quote:
 Originally Posted by pyxbird (Post 387999) All dears, Hi, I am trying to use sediment scour model to simulate the scour patter around a vertical cylinder under steady flow. And here are my quetions: 1. I know the meaning of critical and cohesive sediment fration, but I don't know how to define the values of them. 2. As we all know, we can define the seabed by--initial--fluid region--the sediment concentration--packed, here the value of packed=density of the sand(for example 2.65)*solid fraction of the sediment? And if it is true, so how to define the value of solid fraction of sediment(1? or 0.9?and so on). 3.In the fluid region, we also need to define the fraction of the fluid, if the solid fraction I input is 0.9, so the fraction of the fluid should be 0.1 of 1? When I choose 0.1, after the simulation is run the fluid above the seabed drops straightly down to the "seabed", but when I choose fraction of fluid=1,there is no problem, but I don't think it is reasonable(can there be such large amout of water in "seabed"?), so how to define the value of "fraction of fluid"? 4.After the simulation is done, how can I see the flow pattern in the tab "Analyze"? Is it like this: iso-surface--packed sediment concentration; color variable--strain rate? But I can't find more detailed information, for example the scour depth. I will be grateful is someone can help me.

Hello pyxbird
Because I want to do same study.
I would be thankful, if you can help me.

 pyxbird May 8, 2013 02:59

Quote:
 Originally Posted by mahdi1 (Post 424801) Hello pyxbird Could you please send me your prepin file. Because I want to do same study. I would be thankful, if you can help me.
Sorry I didn't surf the Internet in the past days, I simulated that case last year and the prepin file is lost. And I will continue the work few months later.

 pyxbird May 8, 2013 03:07

Quote:
 Originally Posted by mahdi1 (Post 423051) Hello pyxbird & JBurnham I simulated a channel with movable bed by v10. Could you please tell me that how can I take a plot of bed deformation and also How can I obtain maximum depth score in results file? I would be thankful if you help me.
Firstly you should define a bed in Meshing&Geometry, and after the simulation is done, in Analyze Tab, 3D, you can find the bed height directly.

 elite1989 May 15, 2013 11:30

A case caused by stokes wave acting on a mobile bed

Hello everyone,
I am a Flow-3d 10.0 user.

I am simulating a scour case caused by stokes wave.
The simulation is no error and warning, i want to show the mobile bed in the same way with the figure.2 ( from this address: http://www.flow3d.com/resources/news...our-model.html )
I have already tried the Packed sediment height and the Total sediment solid fraction, but it didn't work.

In Physics-the sediment scour, i only changed the quality of Diameter and Density, is it right?
In output, i only choose the Fluid velocity, Hydraulic data and Sediment concentration. Is there anything i didn't notice?

I also want to take the data of bed height, what option should i take?

Please do me a favor, i appreciated!!!

 mahdi1 May 15, 2013 13:50

Hello elite
I have same problem too.
But you can see bed deformation as follows:
Specify a name for sediment species,
after that, you can find this name in Analyze, 2-D, Counter variable ,.......... choose it
no velocity vector for vector type
Render
This is a way to see bed deformation.
If you could find another method, please inform me.

you can do a sensitive analysis according to below paper:
http://www.flow3d.com/pdfs/tp/wat_en...ions-07-13.pdf

 elite1989 May 16, 2013 05:35

2 Attachment(s)
Thank you, Mahdi.

but the results don't look like the pics from the website i posted last time.

Why can't it be as clearly as the fig.2?
I would like to make my mobile bed showed in one color with boundary line.

Whether the failure reason is that i didn't choose the enough items in output data before simulate?
If yes, what should i take?

It do me a big favor!!!

 mahdi1 May 16, 2013 16:46

Quote:
 Originally Posted by elite1989 (Post 427954) Thank you, Mahdi. I took your advice to analyze the simulation, but the results don't look like the pics from the website i posted last time. Why can't it be as clearly as the fig.2? I would like to make my mobile bed showed in one color with boundary line. Whether the failure reason is that i didn't choose the enough items in output data before simulate? If yes, what should i take? Thanks a lot for your paper about the density and diameter. It do me a big favor!!!
Hi
As I told you before, I have same problem too.
If you could find a solution, let me know.

Regards,
Mahdi

 mahdi1 May 16, 2013 17:31

2 Attachment(s)
Quote:
 Originally Posted by pyxbird (Post 426017) Firstly you should define a bed in Meshing&Geometry, and after the simulation is done, in Analyze Tab, 3D, you can find the bed height directly.
Hello

I have a big problem yet.
I simulated local scour around pier. But my results don't seem to be correct. (please see attached picture).
I also attached my prepin file. I would be thankful if you tell me what my mistake is.

 mahdi1 May 21, 2013 08:46

Hello elite

Do you have experience about local scour around pier?

 mahdi1 May 21, 2013 16:05

Quote:
 Originally Posted by pyxbird (Post 387999) All dears, Hi, I am trying to use sediment scour model to simulate the scour patter around a vertical cylinder under steady flow. And here are my quetions: 1. I know the meaning of critical and cohesive sediment fration, but I don't know how to define the values of them. 2. As we all know, we can define the seabed by--initial--fluid region--the sediment concentration--packed, here the value of packed=density of the sand(for example 2.65)*solid fraction of the sediment? And if it is true, so how to define the value of solid fraction of sediment(1? or 0.9?and so on). 3.In the fluid region, we also need to define the fraction of the fluid, if the solid fraction I input is 0.9, so the fraction of the fluid should be 0.1 of 1? When I choose 0.1, after the simulation is run the fluid above the seabed drops straightly down to the "seabed", but when I choose fraction of fluid=1,there is no problem, but I don't think it is reasonable(can there be such large amout of water in "seabed"?), so how to define the value of "fraction of fluid"? 4.After the simulation is done, how can I see the flow pattern in the tab "Analyze"? Is it like this: iso-surface--packed sediment concentration; color variable--strain rate? But I can't find more detailed information, for example the scour depth. I will be grateful is someone can help me.

Hello pyxbird

Because I am also working on that. I need your experience to create my model.

 elite1989 May 25, 2013 02:06

hi Mahdi

1 Attachment(s)
Quote:
 Originally Posted by mahdi1 (Post 428890) Hello elite Do you have experience about local scour around pier?
I am sorry, Mahdi.
My lab just have some experiences about the scouring on seawall.
I have a prepin file from my friend, it's about the scouring around pier.
Do hope it will give you a hand.

Have a wonderful weekend.

 mahdi1 May 27, 2013 07:21

Quote:
 Originally Posted by elite1989 (Post 429915) I am sorry, Mahdi. My lab just have some experiences about the scouring on seawall. I have a prepin file from my friend, it's about the scouring around pier. Do hope it will give you a hand. Have a wonderful weekend.

Hello elite

Did you see results of that file?
That file is according to below paper and its results are different with results of this paper.
http://www.flow3d.com/pdfs/tp/wat_en...flow-23-09.pdf

Do you know that what is because of this difference?

Also Do you know that how I can obtain maximum scour depth exactly?

Thanks

 pyxbird June 1, 2013 23:26

Quote:
 Originally Posted by mahdi1 (Post 428987) Hello pyxbird Could you please post your prepin file about local scour around pier. Because I am also working on that. I need your experience to create my model. I really appreciate any help you can privide.
Sorry, my prepin file is deleted. Because I ran the simulation last year, and the result was bad. And I am not good at this part, I am sorry. But later maybe in July I will focus on sediment scour, after I learn more about it, and t I can discuss it with you.
Bird
June 2nd, 2013

 hossein_sml August 10, 2013 15:12

sediment Hight

Quote:
 Originally Posted by JBurnham (Post 388135) FLOW-3D v9.4.x includes packed sediment depth and rate of change in depth as output variables that can be used as the color variable when plotting packed fraction as the iso-surface. If you have an earlier version than that, you may have to experiment to find a good way to plot.
Dear Sir,
I am using Flow3d V9.3.2 for simulating scouring. How can I measure sediment height and scour profile at Flow3d V9.3.2?

Thank You

 miss miti December 10, 2013 10:22

scour under submarine pipeline

I Model a submarine pipeline in flow3d, but it doesnt show any scour under pipeline, it will appreciate if you could help me to find out whats wrong with my model. & also which out put is useful in scour models?

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