[OpenFOAM] Extract data in paraview in one output file

saeed jamshidi · January 9, 2024, 14:28

Hello Foamers,

I'm going to extract my data fields such as U and P via paraview. As far as I know, in paraview it is possible to extract data with Save data as I've attached in .csv format.

However, I have come across a questions;

How can I extract all of the data over time in one file, because when I choose Write Time Step option it gives me seperate files for each time step!!!

Thank you for your time.

AtoHM · January 12, 2024, 10:37

Grab ChatGPT and let it build you a helper script to merge these individual files together. Shouldn't take too long.

saeed jamshidi · January 12, 2024, 11:40

Ohhh,
Chatgpt does not perform this action for large amounts of data, unless it suggests a way or method.
Isn't it?

AtoHM · January 14, 2024, 12:08

I too do not think gpt would process data directly, but it will help build you a script for a language like python which you can install in like 2 mins. Technically, you have Python already since you are using PV.

Two ways come to mind: [easy] tell GPT to write a script that loops over all the files that were exported. Then assuming you have a structure like this in there:

Code:

x, y, z, <your value>

You tell it to take column x, y, z from the first file & loop over all files and add the <your value> column, while adding the timestep which is given in the filename by "_%d" in the header. This should give you a big file with your variable to each spatial coordinate and timestep in a separate column.

[More advanced] dig into how to access the vtk objects of Paraview e.g. from the Python shell or within a Programmable Filter. Then you can easily loop over the timesteps and write the data out in whatever form you like.

saeed jamshidi · January 14, 2024, 12:12

Yeahh, sounds good

saeed jamshidi · January 22, 2024, 11:09

Hi again with another question,

I would like to extract my field data such as U and P for cell centers in the computational domain. Is there any way to do that?

As far as I'm concerned when I choose cell data it gives just valuse of the filed data without the coordinates!

This is a part of typical output for velocity with the following procedure: Screenshot (266).jpg

Code:

Cell Type	U:0	U:1	U:2
12	0.01	        -4.58E-07	0
12	0.01	        -4.58E-07	0
12	0.010001	-6.43E-07	0
12	0.010002	-9.69E-07	0
12	0.010002	-9.69E-07	0
12	0.010003	-1.07E-06	0
12	0.010004	-1.09E-06	0
12	0.010004	-1.10E-06	0
12	0.010006	-1.12E-06	0
12	0.010006	-1.12E-06	0
12	0.010008	-1.14E-06	0
12	0.010008	-1.14E-06	0
12	0.010009	-1.15E-06	0
12	 0.01001	  -1.16E-06 	0
12	0.010011	-1.16E-06	0
12	0.010012	-1.18E-06	0
12	0.010012	-1.18E-06	0
12	0.010014	-1.20E-06	0
12	0.010014	-1.20E-06	0
12	0.010016	-1.23E-06	0
12	0.010016	-1.23E-06	0

However I would like to have something like this:

Code:

x  y  z  Ux  Uy  Uz

. . . .........

So, to put it in a nutshell, data of the cell centers as well as their coordinates are welcome.

regards

AtoHM · January 23, 2024, 02:43

Yes, just create 3 calculators: here for X: expression will be coordsX, output will be "X". This way you get it as an actual coordinate (scalar value) to plot for each cell. Once you have done this for Y and Z similarly, you can use the Filter PointToCellData which gives them as Cell Data. Then you can include them in your output.

saeed jamshidi · January 23, 2024, 03:51

Dear AtoHM,

I really appreciate your help, that's what I need.

Best

saeed jamshidi · January 25, 2024, 05:05

Hello AtoHM,

Based on your advice I got my desired output results. However, there is an issue with them. Let me share some data and the procedures of extracting it:
Screenshot (281).jpg & Screenshot (280).jpg

Code:

Cell Type	U:0	U:1	U:2	X	Y
12	0.0049559	-3.36E-05	-5.75E-33	-0.0985	-0.099
12	0.0049554	-3.54E-05	-7.71E-33	-0.0955	-0.099
12	0.0049548	-3.83E-05	-9.53E-33	-0.0925	-0.099
12	0.0049542	-4.13E-05	-1.89E-32	-0.0895	-0.099
12	0.0049538	-4.44E-05	-8.14E-32	-0.0865	-0.099
12	0.0049534	-4.78E-05	-1.76E-31	-0.0835	-0.099
12	0.0049532	-5.12E-05	-1.59E-31	-0.0805	-0.099
12	0.0049532	-5.49E-05	-5.21E-32	-0.0775	-0.099
12	0.0049533	-5.86E-05	-7.21E-33	-0.0745	-0.099
12	0.0049536	-6.25E-05	-1.43E-32	-0.0715	-0.099
12	0.0049541	-6.64E-05	-1.90E-33	-0.0685	-0.099
12	0.0049548	-7.05E-05	1.63E-32	-0.0655	-0.099
12	0.0049557	-7.46E-05	8.95E-33	-0.0625	-0.099
12	0.0049569	-7.87E-05	-2.26E-33	-0.0595	-0.099
12	0.0049584	-8.32E-05	5.87E-33	-0.0565	-0.099
12	0.00496	 -8.74E-05	1.06E-32	-0.0535	-0.099
12	0.0049621	-9.20E-05	3.85E-33	-0.0505	-0.099
12	0.0049644	-9.64E-05	0	-0.0475	-0.099
12	0.0049669	-0.0001005	0	-0.0445	-0.099
12	0.0049699	-0.00010513	0	-0.0415	-0.099
12	0.004973	-0.00010948	1.55E-25	-0.0385	-0.099
12	0.0049762	-0.00011348	5.22E-25	-0.0355	-0.099
12	0.0049799	-0.00011811	5.61E-25	-0.0325	-0.099
12	0.0049843	-0.00012234	2.04E-25	-0.0295	-0.099
12	0.0049892	-0.00012571	1.26E-25	-0.0265	-0.099
12	0.004994	-0.00012949	3.04E-25	-0.0235	-0.099
12	0.0049988	-0.00013327	2.62E-25	-0.0205	-0.099
12	0.0050044	-0.00013594	7.18E-26	-0.0175	-0.099
12	0.0050105	-0.00013789	5.60E-26	-0.0145	-0.099
12	0.0050165	-0.00013982	1.15E-25	-0.0115	-0.099
12	0.0050225	-0.00014188	8.37E-26	-0.0085	-0.099
12	0.0050287	-0.00014381	3.11E-26	-0.0055	-0.099
12	0.005035	-0.00014523	2.53E-27	-0.0025	-0.099
12	0.0050414	-0.00014604	-9.30E-27	0.0005	-0.099
12	0.005048	-0.00014621	-1.45E-26	0.0035	-0.099
12	0.0050545	-0.00014574	-1.32E-26	0.0065	-0.099
12	0.0050609	-0.00014485	-8.22E-27	0.0095	-0.099
12	0.0050674	-0.00014394	3.45E-26	0.0125	-0.099
12	0.0050738	-0.00014314	1.10E-25	0.0155	-0.099
12	0.0050801	-0.00014208	1.07E-25	0.0185	-0.099
12	0.0050861	-0.00013992	4.41E-26	0.0215	-0.099
12	0.0050916	-0.00013675	2.54E-26	0.0245	-0.099
12	0.0050972	-0.00013401	1.01E-26	0.0275	-0.099
12	0.0051027	-0.00013129	-5.77E-27	0.0305	-0.099
12	0.0051074	-0.00012744	-6.79E-27	0.0335	-0.099
12	0.0051118	-0.00012333	-6.92E-27	0.0365	-0.099
12	0.0051162	-0.00011947	-1.59E-27	0.0395	-0.099
12	0.0051202	-0.0001155	8.96E-35	0.0425	-0.099
12	0.0051238	-0.00011141	8.94E-35	0.0455	-0.099
12	0.0051271	-0.00010719	0	0.0485	-0.099
12	0.0051302	-0.00010282	0	0.0515	-0.099
12	0.0051328	-9.84E-05	0	0.0545	-0.099
12	0.0051352	-9.41E-05	0	0.0575	-0.099
12	0.0051372	-8.97E-05	0	0.0605	-0.099
12	0.0051389	-8.53E-05	0	0.0635	-0.099
12	0.0051403	-8.10E-05	0	0.0665	-0.099
12	0.0051414	-7.69E-05	0	0.0695	-0.099
12	0.0051423	-7.28E-05	0	0.0725	-0.099
12	0.0051429	-6.87E-05	0	0.0755	-0.099
12	0.0051433	-6.48E-05	0	0.0785	-0.099
12	0.0051435	-6.12E-05	0	0.0815	-0.099
12	0.0051435	-5.77E-05	0	0.0845	-0.099
12	0.0051433	-5.43E-05	0	0.0875	-0.099
12	0.005143	-5.11E-05	0	0.0905	-0.099
12	0.0051426	-4.80E-05	0	0.0935	-0.099
12	0.0051421	-4.51E-05	0	0.0965	-0.099
12	0.0051415	-4.24E-05	0	0.0995	-0.099
12	0.004954	-3.31E-05	-2.32E-32	-0.0985	-0.097
12	0.0049534	-3.49E-05	-2.32E-32	-0.0955	-0.097
12	0.0049527	-3.78E-05	2.21E-33	-0.0925	-0.097
12	0.004952	-4.09E-05	2.98E-32	-0.0895	-0.097
12	0.0049515	-4.41E-05	-2.67E-32	-0.0865	-0.097
12	0.004951	-4.76E-05	-1.37E-31	-0.0835	-0.097
12	0.0049507	-5.11E-05	-1.37E-31	-0.0805	-0.097
12	0.0049506	-5.49E-05	-4.34E-32	-0.0775	-0.097
12	0.0049506	-5.87E-05	7.03E-33	-0.0745	-0.097
12	0.0049509	-6.27E-05	1.66E-32	-0.0715	-0.097
12	0.0049513	-6.68E-05	1.73E-32	-0.0685	-0.097
12	0.0049519	-7.10E-05	1.07E-32	-0.0655	-0.097
12	0.0049527	-7.52E-05	5.21E-33	-0.0625	-0.097
12	0.0049539	-7.96E-05	4.01E-33	-0.0595	-0.097
12	0.0049553	-8.42E-05	6.80E-33	-0.0565	-0.097
12	0.0049569	-8.86E-05	6.58E-33	-0.0535	-0.097
12	0.004959	-9.34E-05	2.21E-33	-0.0505	-0.097
12	0.0049613	-9.80E-05	0	-0.0475	-0.097
12	0.0049638	-0.00010229	0	-0.0445	-0.097
12	0.0049668	-0.00010714	0	-0.0415	-0.097
12	0.00497	-0.00011176	-5.72E-26	-0.0385	-0.097
12	0.0049733	-0.00011586	2.44E-26	-0.0355	-0.097
12	0.0049777	-0.0001202	2.54E-25	-0.0325	-0.097
12	0.0049823	-0.00012448	2.91E-25	-0.0295	-0.097
12	0.004987	-0.00012841	3.18E-25	-0.0265	-0.097
12	0.0049921	-0.00013211	3.80E-25	-0.0235	-0.097
12	0.0049974	-0.00013547	2.33E-25	-0.0205	-0.097
12	0.005003	-0.00013851	2.01E-26	-0.0175	-0.097
12	0.0050089	-0.00014134	-5.19E-26	-0.0145	-0.097
12	0.0050149	-0.0001438	3.70E-26	-0.0115	-0.097
12	0.0050213	-0.00014576	9.53E-26	-0.0085	-0.097
12	0.0050277	-0.00014736	1.18E-26	-0.0055	-0.097
..................
................
.............

As you can see from the attached figure, I have rectangular domain of -0.1<X<0.5 & -0.1<Y<0.1 with a staggered mesh of 200*100.
You know data for cell centers shoud be sweept row by row (I don't know you got it what I'm saying!), but there isn't such a way here! So, data extracting starts with bottom left corner and ends to the bottom right corner and so on.

The problem line of data is highlited. By the way it gives me right total number of data, exactly 20000. Screenshot (284).jpg
Furthermore, because of this issue when I make a plt file for tecplot it shows weird contour!
Best

saeed jamshidi · January 25, 2024, 07:58

Is it because of decomposition?!!!

saeed jamshidi · January 25, 2024, 08:04

Yeahh it was. I should reconstruct the field.

Screenshot (286).jpg

January 14, 2024, 12:08		#4
AtoHM Senior Member M Join Date: Dec 2017 Posts: 703 Rep Power: 13	I too do not think gpt would process data directly, but it will help build you a script for a language like python which you can install in like 2 mins. Technically, you have Python already since you are using PV. Two ways come to mind: [easy] tell GPT to write a script that loops over all the files that were exported. Then assuming you have a structure like this in there: Code: x, y, z, <your value> You tell it to take column x, y, z from the first file & loop over all files and add the <your value> column, while adding the timestep which is given in the filename by "_%d" in the header. This should give you a big file with your variable to each spatial coordinate and timestep in a separate column. [More advanced] dig into how to access the vtk objects of Paraview e.g. from the Python shell or within a Programmable Filter. Then you can easily loop over the timesteps and write the data out in whatever form you like. saeed jamshidi likes this.

January 22, 2024, 11:09		#6
saeed jamshidi Senior Member Saeed Jamshidi Join Date: Aug 2019 Posts: 214 Rep Power: 8	Hi again with another question, I would like to extract my field data such as U and P for cell centers in the computational domain. Is there any way to do that? As far as I'm concerned when I choose cell data it gives just valuse of the filed data without the coordinates! This is a part of typical output for velocity with the following procedure: Screenshot (266).jpg Code: Cell Type U:0 U:1 U:2 12 0.01 -4.58E-07 0 12 0.01 -4.58E-07 0 12 0.010001 -6.43E-07 0 12 0.010002 -9.69E-07 0 12 0.010002 -9.69E-07 0 12 0.010003 -1.07E-06 0 12 0.010004 -1.09E-06 0 12 0.010004 -1.10E-06 0 12 0.010006 -1.12E-06 0 12 0.010006 -1.12E-06 0 12 0.010008 -1.14E-06 0 12 0.010008 -1.14E-06 0 12 0.010009 -1.15E-06 0 12 0.01001 -1.16E-06 0 12 0.010011 -1.16E-06 0 12 0.010012 -1.18E-06 0 12 0.010012 -1.18E-06 0 12 0.010014 -1.20E-06 0 12 0.010014 -1.20E-06 0 12 0.010016 -1.23E-06 0 12 0.010016 -1.23E-06 0 However I would like to have something like this: Code: x y z Ux Uy Uz . . . ......... So, to put it in a nutshell, data of the cell centers as well as their coordinates are welcome. regards

January 23, 2024, 02:43		#7
AtoHM Senior Member M Join Date: Dec 2017 Posts: 703 Rep Power: 13	Yes, just create 3 calculators: here for X: expression will be coordsX, output will be "X". This way you get it as an actual coordinate (scalar value) to plot for each cell. Once you have done this for Y and Z similarly, you can use the Filter PointToCellData which gives them as Cell Data. Then you can include them in your output. saeed jamshidi likes this.

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January 12, 2024, 10:37		#2
AtoHM Senior Member M Join Date: Dec 2017 Posts: 703 Rep Power: 13	Grab ChatGPT and let it build you a helper script to merge these individual files together. Shouldn't take too long.

January 12, 2024, 11:40		#3
saeed jamshidi Senior Member Saeed Jamshidi Join Date: Aug 2019 Posts: 214 Rep Power: 8	Ohhh, Chatgpt does not perform this action for large amounts of data, unless it suggests a way or method. Isn't it?

January 14, 2024, 12:12		#5
saeed jamshidi Senior Member Saeed Jamshidi Join Date: Aug 2019 Posts: 214 Rep Power: 8	Yeahh, sounds good

January 23, 2024, 03:51		#8
saeed jamshidi Senior Member Saeed Jamshidi Join Date: Aug 2019 Posts: 214 Rep Power: 8	Dear AtoHM, I really appreciate your help, that's what I need. Best

January 25, 2024, 07:58		#10
saeed jamshidi Senior Member Saeed Jamshidi Join Date: Aug 2019 Posts: 214 Rep Power: 8	Is it because of decomposition?!!!

January 25, 2024, 08:04		#11
saeed jamshidi Senior Member Saeed Jamshidi Join Date: Aug 2019 Posts: 214 Rep Power: 8	Yeahh it was. I should reconstruct the field. Screenshot (286).jpg