Undergraduate thesis

lahi1993 · May 9, 2018, 09:20

Hi everyone,

My undergraduate thesis topic is numerical simulation of deflectors in open channels and I'm doing it using openFOAM. I've watched alot of videos on youtube and done the icoFoam tutorials but i can't seem to figure out what to do next.

A brief description of my project.

I have to model the laboratory flume and place 3 deflectors in it with varying distances between them. For validation purposes I have data from a physically conducted experiment. the flume is 5 m long, 150mm wide and 500mm tall. What i cant figure out is, how to get the water to flow at an initial height of 30mm, at a flow rate of 3.3e-3m3/s. When I set the boundary conditions of the inlet to said velocity, the velocity just disspates before it even gets close to the outlet. And it always interacts with the volume above the 30mm water section.

Zigec · May 10, 2018, 05:44

"And it always interacts with the volume above the 30mm water section" .. You sure you set the gravity right?

Post some pics. It would be easier to help you.

Ziga

lahi1993 · May 10, 2018, 05:51

Hey,

Okay so I figured out the issue and ran a successful simulation. But to replicate the laboratory experiment, I have to start with a the water flowing through the flume at a homogeneous 0.4m/s at a depth of 30mm. I used setFields to fill the flume upto 30mm but I dont know how I can start the simulation with all this water moving.

What i'm doing now is using an empty flume and running the simulation for a while until it reaches a steady state.

Also, in the laboratory experiment, the deflectors are placed into the flume while the water is flowing. Is there anyway I can change the boundary condition of the deflectors from allowing water to pass through to being a wall?

Thanks.

Zigec · May 10, 2018, 06:02

not sure if I understand you... but if you want to initialize the simulation so that the water will have some specific velocity before the first time step, then you just need to specify the velocity in the \0 folder. Or you can do one simulation to achieve steady state and then put the last time step data in the \0 folder of the new case.?

Regarding changing the type of the BC, I don't think it's possible what you want to achieve. You could maybe achieve it with some moving mesh, but without a deep knowledge of OF and C++, it'll be a hard one.

lahi1993 · May 10, 2018, 06:07

Thank you,

I will give it a try and update you.

May 9, 2018, 09:20	Undergraduate thesis	#1
lahi1993 New Member Lahiru Egodawatta Join Date: Apr 2018 Posts: 3 Rep Power: 8	Hi everyone, My undergraduate thesis topic is numerical simulation of deflectors in open channels and I'm doing it using openFOAM. I've watched alot of videos on youtube and done the icoFoam tutorials but i can't seem to figure out what to do next. A brief description of my project. I have to model the laboratory flume and place 3 deflectors in it with varying distances between them. For validation purposes I have data from a physically conducted experiment. the flume is 5 m long, 150mm wide and 500mm tall. What i cant figure out is, how to get the water to flow at an initial height of 30mm, at a flow rate of 3.3e-3m3/s. When I set the boundary conditions of the inlet to said velocity, the velocity just disspates before it even gets close to the outlet. And it always interacts with the volume above the 30mm water section.

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May 10, 2018, 05:44		#2
Zigec New Member Ziga Join Date: Feb 2016 Location: Maribor, Slovenia Posts: 27 Rep Power: 10	"And it always interacts with the volume above the 30mm water section" .. You sure you set the gravity right? Post some pics. It would be easier to help you. Ziga

May 10, 2018, 05:51		#3
lahi1993 New Member Lahiru Egodawatta Join Date: Apr 2018 Posts: 3 Rep Power: 8	Hey, Okay so I figured out the issue and ran a successful simulation. But to replicate the laboratory experiment, I have to start with a the water flowing through the flume at a homogeneous 0.4m/s at a depth of 30mm. I used setFields to fill the flume upto 30mm but I dont know how I can start the simulation with all this water moving. What i'm doing now is using an empty flume and running the simulation for a while until it reaches a steady state. Also, in the laboratory experiment, the deflectors are placed into the flume while the water is flowing. Is there anyway I can change the boundary condition of the deflectors from allowing water to pass through to being a wall? Thanks.

May 10, 2018, 06:02		#4
Zigec New Member Ziga Join Date: Feb 2016 Location: Maribor, Slovenia Posts: 27 Rep Power: 10	not sure if I understand you... but if you want to initialize the simulation so that the water will have some specific velocity before the first time step, then you just need to specify the velocity in the \0 folder. Or you can do one simulation to achieve steady state and then put the last time step data in the \0 folder of the new case.? Regarding changing the type of the BC, I don't think it's possible what you want to achieve. You could maybe achieve it with some moving mesh, but without a deep knowledge of OF and C++, it'll be a hard one.

May 10, 2018, 06:07		#5
lahi1993 New Member Lahiru Egodawatta Join Date: Apr 2018 Posts: 3 Rep Power: 8	Thank you, I will give it a try and update you.