Simulating a Wave maker in CFX
 

I want to simulate a Wave maker in CFX.
My model:
http://cdn.persiangig.com/download/9nOrkdEsFh/A.png/dl
I dont know why this error occur?
(DP 0) Update of the Solution component in Fluid Flow (CFX) failed: The solver failed with a non-zero exit code of : 2

Please attach your output file and some images of what you are modelling.

CFX Solver give followin error:
(DP 0) Update of the Solution component in Fluid Flow (CFX) failed: The solver failed with a non-zero exit code of : 2
I don't know why this error occur?
Analsis type is transient...
I attach an Image of my proplem model and boundry conditions
Image Link:http://cdn.persiangig.com/download/9nOrkdEsFh/A.png/dl
I define two Domin...One for Water and the other for Air...I define the boundry conditions as Image attached...I define a Experssion for moving wall velocity(=0.001*sin(100*ctstep)).
I think I should Initialize the VOF for the Domains but I don't know how?

1) Attach your files directly to the forum ... people dont like links where they dont know what the target is.


2) Maybe a screenshot will resolve my question, but why do you need two domains? You can have both phases in one domain.


3) Setting up multiphase simulations and initialising the phases (specifically for water and air setup) is covered in the cfx tutorials. E.g. 10. Free-surface flow over a bump.

Wave Maker
 

Thanks for your attention
Attachment 75364

It is a bad idea to make a domain boundary align with a free surface. It means the difficult numerics of the free surface is placed right on the bit where coupling over the domain boundary is difficult (at the interface).

Make your simulation a single domain.

The error messages you report are workbench level error messages which tell you nothing. You need to look in the CFX output file (.out) for the details. That is why I asked for the output file in the first place.

Wave Maker
 

I simulate the piston type wave maker with wall velocity(0.5cos(10*time)).I do it in transient Analysis type and active dynamic mesh in Unspecified.
I think some thin is wrong...because result is not acceptable...
I cant upload the video here...
I upload some pdf and a video about my case in WE transfer:
https://we.tl/t-fpARQ9vS97
https://we.tl/t-MYIlet5TUL

Wave Maker
 

i managed to simulate the wave maker model in cfx . but the desired results were not achieved . in fact , the results do not match with the theory . I did the simulation in accordance with the Article .I attached the paper file and simulation results link below.
https://we.tl/t-1vZ8kX5nql

I don't have time to look at your results file and I don't click on strange links either.

Post images directly on the forum, and attach your output file directly on the forum. If you don't know how to do this have a look at the FAQ: https://www.cfd-online.com/Wiki/Ansy...n_the_forum.3F

thank you...I solve that problem myself...But I ask a quesion...
I want to plot a point's elevation of water free surface According to simulation time.
for example I want to plot free surface elevation in x=20 from t=0 s to t=20 s.
Attachment 76079

To get the average water height on a surface you can work out the wetted area by areaInt(water.volume fraction)@surface. You can calculate the average water height from there.

You can also do a line integral on a vertical line to get height at a point.

Wave Maker
 

Thank you...I have an other problem...
I want to select some particle of water to plot path vs time...how could I define some particle of water?
I want to plot path of 10 particle in some planes with equal span in x direction...
what should I do?
Attachment 76104

I assume you want these particles to follow the transient flow.

In that case you are going to have to rerun the simulation, you cannot do it post-processing. In the solver you have a few options:
* (easy) Add an additional convection variable, initialised to zero everywhere but 1 at your seed points. They will then convect around the flow. The problem with this approach is you are not modelling particles as such and the additional variable will dissipate away eventually.
* (harder) Define a lagrangian particle phase. Define the particles to have almost zero mess and lots of drag. You can then track their motions in the post processor. This will slow the simulation down quite a bit.
* (have not checked if this is possible) I vaguely recall there is a massless particle option in CFX. This would be the best way of doing it, but I am not sure how it is done, or even if it really is possible. I will leave further research of this comment to you :)

thank you...But How I should define particles?...I want to define 10 particles in@some plan to plot particles paths and Velocties...in CFX-Pre how I define these particles?

The only way I know to seed a flow with lagrangian particles at specific locations is with a user fortran routine to set the particle locations.

OK....How I should do that?...I don't know what should I do...There are any tutorial for particle path in VOF Multiphase model?

No, the VOF Multiphase model is a Eularian model. You don't want that one. You want the Lagrangian particle tracking model.

It has been a while since I looked, but I think there is an example fortran file in the CFX installation somewhere. Have a look in the CFX documentation for user fortran for particles.

Just a short warning: the particle tracking model gives you HUGE result files depending on how many particles you have inside the domain. Easily reaches 10 GB an more for a .res file. Make sure you have the resources to handle this as well.

The huge result files are when you have zillions of particles. From what I understand of this application there should only be a handful of particles, so file size increase should be minimal.

I just need some particles path...If I don't use VOF Model then How I simulate the free surface tank?...How I define materials and simulation setup?...I search Web,papers and every thing to learn but I can't...I'm confused
Attachment 76163

Sorry, I forgot that this was applied to a VOF model. Yes, you need a VOF model for the free surface and Lagrangian particles for your particles to track.

How I can imlplement the lagrangian particles to VOF Model?

Look at the tutorial examples to see how to set up a particle tracking simulation.

Don't ignore the convection only additional variable suggestion I made right at the start. This approach is MUCH easier to implement and might be good enough for you.

I didn't find any tutorial about particle tracking...I'm really confused...
I tried some thing but didn't get result....What should I do?
Attachment 76175

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You only defined how particle look like and their interaction with air.
But where do you inject them?

I don't want do Inject them...I want some particle to plot their path vs simulation time...If I define Inection region I should more than 100 region...let's assume I create region...I define mass flow rate and injection velocity and then what happen?...I get the desire result?...How I plot the particle path?

First of all, let me repeat this for the third time:

If you are having problems with the Lagrangian particle approach you should do this approach as it is much simpler.

And regarding Lagrangian particle tracking - all the basics are covered in the CFX tutorials available in the CFX documentation and the ANSYS Customer webpage. This includes how to set them up and how to visualise them.

I also recall saying previously that you cannot use an injection region to place your particles. The ONLY way to place particles in specific locations is using a user fortran routine.

Thank you ghorrocks;
I want to learn Fortran for cfx...I'm looking for a Tutorial...a proper one...

Wave Maker
 

I define a material with Water at 25 properties.
I define a injection region.
Simulation time:0.02 [s],Step:0.01 [s]
But error occur and the result is unacceptable...
Attachment 76325

Attachment 76326

Attachment 76327

Attachment 76328

Attachment 76329

We are wasting our time here. Can you please try the additional variable approach I have suggested? The Lagrangian particle approach is not simple and you will need a lot more experience in CFD before you will get that working.

I am not going to help you further on this thread if you persist with the Lagrangian particle tracking. I will only assist you with the additional variable approach.

thank you for your attention...
How I can create velocity vector,start from end point of previous step Vectors?

I don't understand your question, can you ask it again please? I also do not understand what relevance it has to this thread.

Sorry...I made it hard...I want to plot velocity vectors in each step in same figure...what should I do in each step plot vector from same seeds...
I have 3 new Question?...
1-what do int() and sum() functions do?
2-How I can define a expression with algebraic equations?
3-I want to plot acceleration,I should use differential equation or I want use Integral to obtain displacement of a particle from velocity...I can use Integral or differential to define variable or expression?
thanks for your attention

Plotting velocity vectors is a basic post-processing task. The vectors are drawn at seed points. This is all covered in the CFX tutorials. You really should do the tutorials so you understand the basics.

1) I assume you are asking about the CEL expressions. These are all described in the CFX reference guide.

2) This is covered in the CFX tutorials. Please do them, you are wasting everybody's time unless you know the basics.

3) Acceleration of what?

Thank you...
I'm sorry... I search tutorial but I couldn't understand something and sometimes I ask simple Questions.. I'm really sorry...
I want to create a point that It's position is function of a variable...
I explain more... I want to plot a particle path...
Let's assume Initiall position is (X, Y) ...
Then Next step Position will be as follow:
x=X+U*t
y=Y+V*t
t: constant time step
U:Velocity x direction
V:Velocity y direction
If I can define the point with (x, y) then I can plot the particle path...
Even I can make animation of trajectory...
It is possible to define point like this?

This question was long ago, but it is worth saying that I plotted particle paths using Ansys's Ensight. It is a post-processing module in Ansys Workbench. It calculates particle path in a few simple steps and illustrates particle movement as animation. It offers various visual options you can customize for the desired results.