[pary07]

Hello,

I am trying to calculate the Tumble using star ccm+ and I am new to it. Basically, my model has an extension on the port as well as the cylinder. Extensions are around half a meter. There is a single intake valve which is inclined, and exhaust is closed (so no symmetry). As a extensions are long I do not see vortex for the tumble. It is steady state simulation with no piston as an assumption. Now I am not sure how exactly to calculate the tumble. So I am trying to manually extract the coordinates and their velocities to find the summation of the angular velocity. I have made derived parts located across the valve and then using XYZ internal table I extract the coordinates and the Velocity(i,j,k) on this plane. Then, I create a user field function(UFF) to interpolate the table values . My formula for tumble(y axis) velocity is summation(Zi.Ux,i - Xi.Uz,i)/summation(Zi^2 +Xi^2)
where Xi,Zi, Ux,i, and Uz,i are the coordinates and the velocities on the plane. But I do not know how to use the XYZ table values to put into this formula.
if I have to use this syntax, then what is the scalar expression here ?
interpolateTable(@Table("<tablename>"), "<x-column>", {LINEAR | STEP | SPLINE}, "<phi-column>", <scalar_expression>)

Thank you in advance.

[pary07]

Could anybody please help me out here?

[ping]

why are you not using the inbuilt tumble and swirl reports since they are designed for exactly your requirement
see the user guide Post-Processing > Reporting Results > Specific Reports > Tumble/Swirl Ratio

[pary07]

Hi ping,

Thank you so much for replying. Yes, I did try to use the inbuilt Tumble/Swirl report. I did use a lot of combinations inputs into the report but then the answer it shows in something like 10^-3, which is not true. Also, this report allows us to choose the whole body as the part and not a plane. So in my case, I have an extended cylinder with no piston, so then I guess the report is calculating the sum or average of the entire region and maybe that's why such an answer. Therefore, I was perhaps trying to manually calculate the omega by extracting data from the plane which is located at half the stroke.
So I am not sure why the report is not giving an appropriate value. Have you personally used the report?

Thanks.

[ping]

i have tried these reports and know they give answers and dont know how accurate they are but knowing that star-cd is the industry standard for engine cfd it is hard to believe there is something wrong with the method in ccm+.
it is normal to have a long cylinder extension when doing such studies but i suggest you need to make the extension a separate region using extrusion for example and then only run the report on the chamber region

[pary07]

Well, creating a separate region for the extrusion would imply to redo all the simulations and that would be cumbersome considering the time and the number of simulation hours I have left. But I believe there should be a way to do it. Also, I do not think that the report results are wrong, just that it is being taken on the whole region that just the cylinder.
And, I wanted to know, if you could provide me information on the details you had entered into the tumble/swirl report so that I can have an idea about it.

Thank you.

[ping]

if you dont want to run the cases again your could map the results onto a mesh of just the chamber using the mapping feature or via table export and import and initialize.
when i tested i just followed the help for settings so nothing special

[Mikemon]

Can you explain more pls? How can I export data from a plain?, just in the chamber zone, and calculate Tumble Ratio?

[ping]

place all the required fields into a table and then export this table to a csv text file. open or prepare the other sim file then import your csv result fields as a table. use this table as the initial field settings in the initialise area of physics settings then do an initialisation. check that the field looks correct in a few scalar and vector scenes.