Vegetated open channel.

mchith · May 12, 2011, 06:19

Hey everyone. Alright, I am going to start working on a 3D model of a vegetated open channel for my Dissertation, I dont know much about modeling, I will be using Ansys Icem CFD and Asys Fluet, I have 1 and a half moths to produce the model. I attached a Picture of the vegetation i have to model, and i have to best represent it in the model. Would i be able to do that in a short time? any tips, advice I would be greatful for the help. thank you

Thomas_L · May 12, 2011, 18:31

Have you done a research in the literature?

Reynolds stress modeling of vegetated open-channel flows
Journal of Hydraulic Research
Volume 42, Issue 1, 2004, Pages 3 - 11
Authors: Sung-Uk Choia; Hyeongsik Kanga

But it seems you're going to play with the turbulence model of Fluent for the Flow.

Tell us more about the vegetation. Do you want an approximation like simple cylinder or a structure more complex .

mchith · May 12, 2011, 18:35

hey, the purpose of my study is to explore the suitability of numerical models in estimation of velocity and flow resistance (Manning n) in open channels with submerged vegetation. and what i am trying to do is best represent the vegetation so it should be as close as i can get to the real thing, so i guess that makes it complex.

meangreen · May 12, 2011, 18:45

I have two suggestions:
1. Since you know what solver you will be using you should really open a thread on the Ansys forum. You will get more specific help from people familiar with the solver.

2. It is really hard to understand what you want to do. If you just want to model the vegitation... that doesn't really mean very much from a flow perspective. What is vegitation? Is that the roots of the plant? Do you want to see them move around in the flow? Do you want to see the water flow around starionary roots? Are you modeling the dirt flowing in the water? Please provide more information on teh flow perspective of your project so people can better help.

Casey

meangreen · May 12, 2011, 18:47

do you just mean flow in a channel with roots? like a hole bunch of "poles" in the middle of the channel? You need to make a mesh with a meshing program that can handle all of the aspects of your geometry... if that is what you mean.

mchith · May 12, 2011, 19:16

yeah man briefly, I want to model the channel with the vegetation submerged in it and see how this vegetation affects to flow of water, I will not do any moving mesh, I will look at them still.

meangreen · May 13, 2011, 10:31

I would say in a month and a half it is going to be difficult to learn enough about CFD to do it well. You should start by reasearching different mesh types and figure out how to make a stable mesh that accurately describes your flow. Do you NEED to model in 3D? Or will 2D be ok? If it is in 2D, then can you use rectangles to approximate the vegitation. These are all questions that *should* come up during your mesh generation. Once you make the mesh you need to make sure it isn't grid dependent. Make the mesh size smaller (the dimensions of each cell) and see if your solution changes.

If you have no experience modeling a month and a half is a very short period of time to understand how to do numerical modeling. Check out a book (like Patankars Numerical heat transfer and fluid flow) and get some basic knowledge before you start.

Casey

mchith · May 13, 2011, 10:42

Thanks a lot for the advice I will have a look at that book. I cant do anything about the time I have so i will have to live with it. I cant do a 2d model because someone else will be doing that. sooooooooo I have this goes well or else i am **********...

May 12, 2011, 18:31		#2
Thomas_L New Member lemee.thomas@gmail.com Join Date: Apr 2011 Posts: 9 Rep Power: 15	Have you done a research in the literature? Reynolds stress modeling of vegetated open-channel flows Journal of Hydraulic Research Volume 42, Issue 1, 2004, Pages 3 - 11 Authors: Sung-Uk Choia; Hyeongsik Kanga But it seems you're going to play with the turbulence model of Fluent for the Flow. Tell us more about the vegetation. Do you want an approximation like simple cylinder or a structure more complex . celera likes this.

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May 12, 2011, 18:35		#3
mchith New Member mchith Join Date: Apr 2011 Posts: 18 Rep Power: 15	hey, the purpose of my study is to explore the suitability of numerical models in estimation of velocity and flow resistance (Manning n) in open channels with submerged vegetation. and what i am trying to do is best represent the vegetation so it should be as close as i can get to the real thing, so i guess that makes it complex.

May 12, 2011, 18:45		#4
meangreen Member Casey Join Date: Jun 2009 Posts: 98 Rep Power: 16	I have two suggestions: 1. Since you know what solver you will be using you should really open a thread on the Ansys forum. You will get more specific help from people familiar with the solver. 2. It is really hard to understand what you want to do. If you just want to model the vegitation... that doesn't really mean very much from a flow perspective. What is vegitation? Is that the roots of the plant? Do you want to see them move around in the flow? Do you want to see the water flow around starionary roots? Are you modeling the dirt flowing in the water? Please provide more information on teh flow perspective of your project so people can better help. Casey

May 12, 2011, 18:47		#5
meangreen Member Casey Join Date: Jun 2009 Posts: 98 Rep Power: 16	do you just mean flow in a channel with roots? like a hole bunch of "poles" in the middle of the channel? You need to make a mesh with a meshing program that can handle all of the aspects of your geometry... if that is what you mean.

May 12, 2011, 19:16		#6
mchith New Member mchith Join Date: Apr 2011 Posts: 18 Rep Power: 15	yeah man briefly, I want to model the channel with the vegetation submerged in it and see how this vegetation affects to flow of water, I will not do any moving mesh, I will look at them still.

May 13, 2011, 10:31		#7
meangreen Member Casey Join Date: Jun 2009 Posts: 98 Rep Power: 16	I would say in a month and a half it is going to be difficult to learn enough about CFD to do it well. You should start by reasearching different mesh types and figure out how to make a stable mesh that accurately describes your flow. Do you NEED to model in 3D? Or will 2D be ok? If it is in 2D, then can you use rectangles to approximate the vegitation. These are all questions that should come up during your mesh generation. Once you make the mesh you need to make sure it isn't grid dependent. Make the mesh size smaller (the dimensions of each cell) and see if your solution changes. If you have no experience modeling a month and a half is a very short period of time to understand how to do numerical modeling. Check out a book (like Patankars Numerical heat transfer and fluid flow) and get some basic knowledge before you start. Casey

May 13, 2011, 10:42		#8
mchith New Member mchith Join Date: Apr 2011 Posts: 18 Rep Power: 15	Thanks a lot for the advice I will have a look at that book. I cant do anything about the time I have so i will have to live with it. I cant do a 2d model because someone else will be doing that. sooooooooo I have this goes well or else i am **********...