Manual Drag Calculation.
Altair EmployeeHello everyone.
I am currently running external aerodynamics flow simulations for a truck model. I use HyperMesh to generate the surface mesh and then use Virtual Wind Tunnel to run the flow simulation.
Once the simulation is complete, VWT generates the automatic PDF report with a drag coefficient value. However, after performing design modifications to the geometry of the model, the drag coefficient values seem to be off from expectations. Hence, I am wondering if there is a way to manually calculate the drag force generated by the model in AcuFieldView, AcuConsole or AcuProbe and then the drag coefficient using the frontal area?. I want to check the validity of the drag coefficient values that are automatically generated in the report.
Also, I have noticed that the report calculates the drag for each and every part in the model and then sums it up to give the total drag value. I'm wondering if there is a way to select the entire model (all parts included) and display the drag force created by it rather than doing it for individual parts.
Thanks for the help in advance!
Yatish Chandra
Answers
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There are many things that need to be verified, including mesh dependence studies, to validate the results against tests/expectations. Have you tried different mesh sizes?
Yes its possible to get the drag values manually from the simulations as well. The drag forces are available in AcuProbe for individual surfaces. Since there are many surfaces, you might want to use AcuSumOsi script. Check Program Reference Manual in your installation. That has details on how to use this command.
I would recommend contacting your local Altair Support to help you out with this issue and scripts that you might need.
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ydigit_21275 said:
There are many things that need to be verified, including mesh dependence studies, to validate the results against tests/expectations. Have you tried different mesh sizes?
Yes its possible to get the drag values manually from the simulations as well. The drag forces are available in AcuProbe for individual surfaces. Since there are many surfaces, you might want to use AcuSumOsi script. Check Program Reference Manual in your installation. That has details on how to use this command.
I would recommend contacting your local Altair Support to help you out with this issue and scripts that you might need.
Hello,
I am trying to find the AcuSumOSI scrip in the Program reference manual but I haven't found it. Can you please direct me to it? I am using HW2021.1
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granzer_22210 said:
Hello,
I am trying to find the AcuSumOSI scrip in the Program reference manual but I haven't found it. Can you please direct me to it? I am using HW2021.1
Looks like the Programs Reference Manual does not have a chapter/section on acuSumOsi. You can issue:
acuSumOsi -h
for general usage options.
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Thank you @acupro. Is there a way to extract the traction at at each surface seperately as a array/list/table( Not the sum of traction forces at given surfaces)? I can use acuSumOsi giving individual surface names but o have lot of surfaces and so this becomes a time intensive task. I tried 'export' from acuprobe ..but it exported in XML format which couldn't be imported into Excel. I want the traction at each surface so as to import into Excel.acupro_21778 said:Looks like the Programs Reference Manual does not have a chapter/section on acuSumOsi. You can issue:
acuSumOsi -h
for general usage options.
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granzer_22210 said:
Thank you @acupro. Is there a way to extract the traction at at each surface seperately as a array/list/table( Not the sum of traction forces at given surfaces)? I can use acuSumOsi giving individual surface names but o have lot of surfaces and so this becomes a time intensive task. I tried 'export' from acuprobe ..but it exported in XML format which couldn't be imported into Excel. I want the traction at each surface so as to import into Excel.
With 'Export' from AcuProbe, you also have the option of file type Raw Data File and/or Raw Data File with Label - which you can import to Excel.
You can also put the list of surfaces into the local Acusim.cnf file - to be used with acuSumOsi:
surface_integral_output_sets = Surface1,Surface2
(or maybe use wildcards - like Surface*)
acuTrans itself will also give you the output from all the output surfaces:
acuTrans -osi -osiv traction
(The Programs Reference Manual does have a section dedicated to acuTrans...)
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acupro_21778 said:
With 'Export' from AcuProbe, you also have the option of file type Raw Data File and/or Raw Data File with Label - which you can import to Excel.
You can also put the list of surfaces into the local Acusim.cnf file - to be used with acuSumOsi:
surface_integral_output_sets = Surface1,Surface2
(or maybe use wildcards - like Surface*)
acuTrans itself will also give you the output from all the output surfaces:
acuTrans -osi -osiv traction
(The Programs Reference Manual does have a section dedicated to acuTrans...)
acuProb 'export' option' just has eport in XML format and didn't show export in raw format (2021.1ver). acuTrans command gave me individual file for every surface, so it still is a time consuming process to open every single file manually for the required surfaces. Editing the local acuSim.cnf did not help as it again gave the sum of the traction forces when running the acuSumOsi command same as using
acuSumOsi -osis surface1, surface 2,... .
I just need the list of traction at data for each surface (hopefully showing the surface name so as to easly distinguish and at the latest time step).
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granzer_22210 said:
acuProb 'export' option' just has eport in XML format and didn't show export in raw format (2021.1ver). acuTrans command gave me individual file for every surface, so it still is a time consuming process to open every single file manually for the required surfaces. Editing the local acuSim.cnf did not help as it again gave the sum of the traction forces when running the acuSumOsi command same as using
acuSumOsi -osis surface1, surface 2,... .
I just need the list of traction at data for each surface (hopefully showing the surface name so as to easly distinguish and at the latest time step).
Yes - acuSumOsi gives the total. I guess I misunderstood what you had said regarding that script.
I've just looked at AcuProbe 2021.1 on both Windows and Linux, and see Raw Data File and Raw Data File with Label in the pull-down for Save As file type:
You would then still need to give the appropriate name to each file, and it will give all time steps - same as acuTrans. You could also use the GUI - acuOut - to give a different approach to acuTrans. But still, same data and filename structure as command-line acuTrans.
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acupro_21778 said:
Yes - acuSumOsi gives the total. I guess I misunderstood what you had said regarding that script.
I've just looked at AcuProbe 2021.1 on both Windows and Linux, and see Raw Data File and Raw Data File with Label in the pull-down for Save As file type:
You would then still need to give the appropriate name to each file, and it will give all time steps - same as acuTrans. You could also use the GUI - acuOut - to give a different approach to acuTrans. But still, same data and filename structure as command-line acuTrans.
That is odd as I only have option to export as XML. Are there any additional settings that needs to be activated?
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granzer_22210 said:
That is odd as I only have option to export as XML. Are there any additional settings that needs to be activated?
Yes - that is strange. I don't know what would cause that. My installation is "out-of-the-box" 2021.1, nothing changed from default. Have you tried the acuOut GUI to write the data you want? From the AcuSolve Command Prompt, type acuOut then open the .Log file as you would in AcuProbe. You can write the desired data to Table format to import to Excel.
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acupro_21778 said:
Yes - that is strange. I don't know what would cause that. My installation is "out-of-the-box" 2021.1, nothing changed from default. Have you tried the acuOut GUI to write the data you want? From the AcuSolve Command Prompt, type acuOut then open the .Log file as you would in AcuProbe. You can write the desired data to Table format to import to Excel.
Thank you. I tried the acuOut utility. But trying to write the Surface(Integrated) data:Traction for selected surface again created a bunch of .osi files seperate for each individual surfaces that was selected.
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granzer_22210 said:
Thank you. I tried the acuOut utility. But trying to write the Surface(Integrated) data:Traction for selected surface again created a bunch of .osi files seperate for each individual surfaces that was selected.
Correct - I don't believe there is a way to write data from multiple surfaces into a single file, keeping the surface results separated in that file.
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