Learning Forum

[mmohaqeqf]

Hello Everyone,

A laminar steady-state 3-D rectangular pipe flow has been simulated with a velocity inlet and a pressure outlet, with some known fluid properties. The flow results are found to be agreeing with the typical flow behavior (velocity and pressure values agree with theoretical results). We are using Ansys 18.1 academic version.

We need to generate streamlines, starting at center of each element on the inlet (this part is easy) and export the data out. Therefore, if we have n elements (cells) on the inlet, n number of streamlines need to be generated. Then, we need to trace each streamline separately and export the relevant information (i.e. velocity magnitude, pressure, or any other user defined variable) out for further analysis in MATLAB/EXCEL.

We already created the streamlines at the center of each cell on the inlet in CFD-Post. Then, we exported the streamlines information out as csv file. However, when we open the file in excel, it is almost impossible for us to see which points (nodes) are related to which streamline. We need to be able to distinguish the streamlines from each other. Note that in our case (steady state), streamlines are the same as pathlines.

In another word, we need an excel file, which has a format similar to the following:

Streamline 1

x  y  z  variable1 variable 2 ...... variable m

(number of rows here depends on the number of nodes forming this particular streamline)

 

Streamline 2

x  y  z  variable1 variable 2 ...... variable m

 (number of rows here depends on the number of nodes forming this particular streamline)

 .

.

.

.

up to the n-th streamline.

 

Any help is appreciated.

[Syamak]

Hi;

 

I have faced same problem as you had previously. I need to assign each cell in domain zone for each streamline in order to solve additional equations along the streamline. Did you get your answer? I appreciate it if you kindly share your updated ideas with regards to this matter.

 

Best regards,

Syamak

[mmohaqeqf]

Hi Syamak;

I have posted my question in several online threads/websites, with no replies!!! I also contacted Ansys help center on the phone, which they also were not really helpful.

Anyway, I am still a beginner in Fluent. But, I managed to solve my problem by using the Pathline function in the Fluent result section. When doing the pathline (which is the same as streamline for steady state flow), you can either select your inlet as the seeding plane for particle release (in which case the Fluent release one particle at the center of your cell/element) or make your own plane with any arbitrary number of seeding particles. Also, you can have your outlet as the source plane and check the "reverse" option in the pathline dialogue box and trace the particles back from the outlet to the inlet. Furthermore, if you check the "write to file" option and then "Fieldview" from the drop down list, you can save the data for all the pathlines in a .fvp file (CSV) which is in ASCII format and very easy and convenient for post processing in MATLAB. If the output file is not very large, Excel can also handle it.

I hope this helps you move in the right direction. Please let me know if I can be of any further help.

Regards,

[mmohaqeqf]

By the way, the .fvp file has the following format (it has five columns):

 

(Here is a few line with a bunch of info, which was not useful for my case)

n (this is the number of steps in the corresponding pathline)

x     y     z   time  variable

 

There goes the next pathline up to the last one.

Regards,

[Amine Ben Hadj Ali]

You can manage that by exporting a pathline or massless particle track from Fluent into the Format you want to post-process. Each track would have its own ID.

[yg327]

Hi, mmohaqeqf ,

 

Many thanks for your solution. But I found that the exported data is from interested cross section plane to the downstream outlet plane rather than going backward to upstream inlets. Did you find that problem, please?

 

Regards,

Yunhu

[yg327]

Hi, mmohaqeqf ,

 

Many thanks for your solution. But I found that the exported data is from interested cross section plane to the downstream outlet plane rather than going backward to upstream inlets. Did you find that problem, please?

 

Regards,

Yunhu

 

 

 

Hi Syamak;

I have posted my question in several online threads/websites, with no replies!!! I also contacted Ansys help center on the phone, which they also were not really helpful.

Anyway, I am still a beginner in Fluent. But, I managed to solve my problem by using the Pathline function in the Fluent result section. When doing the pathline (which is the same as streamline for steady state flow), you can either select your inlet as the seeding plane for particle release (in which case the Fluent release one particle at the center of your cell/element) or make your own plane with any arbitrary number of seeding particles. Also, you can have your outlet as the source plane and check the "reverse" option in the pathline dialogue box and trace the particles back from the outlet to the inlet. Furthermore, if you check the "write to file" option and then "Fieldview" from the drop down list, you can save the data for all the pathlines in a .fvp file (CSV) which is in ASCII format and very easy and convenient for post processing in MATLAB. If the output file is not very large, Excel can also handle it.

I hope this helps you move in the right direction. Please let me know if I can be of any further help.

Regards,