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How to generate a wave in Fluent?

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Old   July 18, 2011, 05:21
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You can sample results along the line using 'Probe' option in one of the menus. Then, you are allowed to select a point, line or rake. Line and rake is essentially the same, if I remember well the only think which separates line and rake is sample point distribution along the sample line. Check in the documentation, I am not using Fluent anymore.
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Old   July 18, 2011, 07:56
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Quote:
Originally Posted by paka View Post
You can sample results along the line using 'Probe' option in one of the menus. Then, you are allowed to select a point, line or rake. Line and rake is essentially the same, if I remember well the only think which separates line and rake is sample point distribution along the sample line. Check in the documentation, I am not using Fluent anymore.
Hi Paka,

Thanks for your response.
What do you mean for "Probe' option in one of the menus? Can you describe more detailed your ideas in FLUENT S/W?

Best regard
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Old   May 28, 2012, 16:32
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hi
i wane udf file for wave too or wave.msh
help me ( ali.3863@gmail.com )
tnx
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Old   October 22, 2012, 13:35
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Any help would be appreciated:

I am using FLUENT to model a regular wave tank with linear theory and dynamic mesh in 2D. I am using a VOF multiphase model (water and air), with transitory regime. The length of the water tank is 200m, from th mobile wall, with 16 m depth. I want to measure the magnitude (amplitude) of the wave at at position x = 20 m from the mobile wall, through of the time, in the free surface (depth= 0m), . How to measure the magnitude (amplitude) in that distance?.
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Old   October 22, 2012, 14:18
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You have an option in Fluent to sample data using LINE or RAKE option with specified sampling point density along the chosen sampling path.

Unfortunately, to my knowledge, Fluent doesn't allow you to sample your data by default with such a detail as to track free-surface movement. If anyone thinks I'm mistaken, please correct me.

The other option is your own UDF.
Try to google. Maybe by some chance someone posted a similar solution.

Regards and good luck.
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Old   October 22, 2012, 14:19
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The other observation, Fluent is not the most efficient tool to use with VoF, i.e. computation time is much more significant than other available open-source software.
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Old   October 22, 2012, 14:31
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Maybe you can use a monitor.
Create a line at the x-location that you need. Then set the monitor for a liquid phase volume fraction. You might be able to get the (approximate) highest point of the wave at a certain time on that line.
This might do the trick.
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Old   October 22, 2012, 14:33
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This is nothing different from what I wrote. Same tool/option.
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Old   October 22, 2012, 15:27
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Thanks you. I will consider your suggestions. I have tried using a line, but not in the same way. With UDF it could get the magnitud of the wave, although in this moment, I dont have much knowledge how to create the file. Regards!!!
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Old   October 22, 2012, 15:29
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What do you mean by 'magnitude of the wave'?

Do you mean velocity? Wave height?

You can extract all this data using line/rake option.
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Old   October 22, 2012, 15:39
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It is the height of the wave, the sinusoidal movement. I cant to extract the data but I will try
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Old   October 22, 2012, 15:49
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AFAIK, you set a rake/line to a Volume of Fluid. This way it will output the 0/1 volume of fluid with the line location on x-axis versus the height of the flow on y-axis. The tool unfortunately is not perfect and I am afraid you can only get visual representation. In order to dump actual data in form of numbers I'm afraid you will need to write your own UDFs. It is quite a bit of time I used Fluent, but I don't expect they added this kind of functionality.

(again, for UDF, Google might be your best friend here)

BTW. If you have your own wave paddle routine (must be UDF), you know the function you are using. Assuming your wave generating function (UDF) is coded correctly and your mesh resolution is appropriate for the problem you are trying to solve, for the same boundary conditions along the path of wave travel, the results should be the same as input values. In short, wave generating function should equal generated wave characteristics at location along the travel path, i.e. smooth flow bedding, constant depth, the same BC, gravity, etc.
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Old   October 22, 2012, 16:20
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Ok. In the simulations, the sinusoidal movement only Its seen in X=0, from the mobile wall, but with X>0, the movement is zero, there is not height of the wave. I will try with both methods and I will view the results. Thanks you for your suggestions. Best Regards!!
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Old   October 22, 2012, 16:27
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Note that when you read the data at x=0 you read it for the function you provided at BC. You cannot expect this output will give you full domain answer.
From what you said, I understand you did not apply/use line/rake, therefore you cannot read any data for your domian.

For X>0 you must use line/rake tool.

For the moving BC, i.e. moving wall, the function which drives the wall must be a displacement or velocity function (this is how UDF is defined). Whatever you are going to read AT the wall MUST be EXACTLY the same as the function you provide. Take also a note that if you define a rake/line close to the moving boundary i.e. in the first column of finite volume elements, i.e. along the height of moving boundary, you might not get exactly the same readings since the values are approximated. The smaller the cells and closer to the wall the more accurate answer you will get.
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Old   October 22, 2012, 16:34
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This is the UDF file of the mobile wall:

#include "udf.h"

DEFINE_CG_MOTION(wave, dt, vel, omega, time, dtime)
{
vel[0]=(0.30823)*((1 - exp(-0.417*time))*1.0472*cos(1.0472*time) + ((0.417*exp(-0.417*time))*sin(1.0472*time)));
}
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Old   October 23, 2012, 09:05
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Hi Pedrin
My problem is to introduce a moving wall with sinusoidal motion in a channel,
did I have to write your udf or just I define the velocity like vel[0]= 2 sin (0.5 t) for example.
thank you.
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Old   October 23, 2012, 15:45
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The movement of mobile wall is made according to the characteristics of the wave (sinusoidal motion). The velocity condition to the piston (mobile wall) is a function of the time, period and frequency of the wave, according with the Wave Linear Theory.
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Old   October 24, 2012, 03:02
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thank you for your response.
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Old   October 24, 2012, 12:24
Default Hi, WSWGg, Can you help me to send your UDF profile, I am in trouble with waves now
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Quote:
Originally Posted by WSWGg View Post
Arampath and Ekakavand, check your e-mails, I've just sent my UDF file, like had promised.
Novice, excuse me, but I don't understand you post. You simulated wave using linear wave theory making boundary conditions on velocity components on enter border, am I right? So, what's the problem?



Thank you in advance!
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Old   October 24, 2012, 12:34
Default Hi, Elahe, can you send me the UDF profile from WSWGg, I appreciate your help.
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Quote:
Originally Posted by ekakavand View Post
Hi

can you send me your email?
my email is here... you can see it.

best
elahe


Thank you in advance!
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