Calculating moments around body

Using SimScale Fluid Flow / CFD
1

Hello

i know how to calculate total forces acting on body, but i want to know also all 3 momentums acting on body (around each axis X, Y, Z).

I draw model so that each axis i want to calculate around will go through the center. But how to get momentum ?

I know that momentum is force acting on arm. So if we take each cell and get force acting on it, we can also take its distance in each direction to the center and calculate momentum on the cell around my center, if we multiply that for each cell and then sum it together we get momentum for whole body around my axis system.

But how to do that on Simcale or in Parawiev ?

Thank you

2

Hi @AnetaNovak!

Interesting question! As far as I know our PowerUser @1318980 already dealt with such a problem but I am not sure.

Here is an interesting discussion about forces/moments in general: Forces & Moments in SimScale

In my opinion the documentation explains it very precisely: Forces and moments

Is that something you were looking for?

All the best!

Jousef

3

Hi guys, sorry was oblivious to this because my emails weren’t working, Apologies! I think from my initial read of this it’s not clear if you want momentum or moments. From the above you describe moments and that is indeed given by the forces and moments results control item.

if it is momentum you are after this could be calculated in paraview, however, it might just be better calculating analytically presuming solid body, zero deformation.

Kind regards,
Darren

4

Hello … i m sorry for confusion … i would like to calculate moments. I think i can do it in simscale, but can i also do it into parawiev ? And on Simscale if i enter as center of rotation 0;0;0 will the center for moment be origin of model ?

Also another big problem might be when i take some sort of car and i want to simulate in cornering condition and i want axis to be perpendicular to model not domain. But when i import the model with axis perpendicular to model domain will also be perpendicular to those axis. The question is than, how to calculate moments around car on axes which are perpendicular to wheel base (car) and domain is set to lets say 5° or 10° condition ?

Thanks

5

Hi @AnetaNovak, yes indeed 0,0,0 will be geometry origin. i.e. the origin of the model as it was imported from CAD.

I think it should be quite easy to do in paraview, similar calculating forces in axis directions, however, you will need to extract surface centre positions (not sure how to do that off the top of my head, ill look into it).

My advice on cornering would be to set the airflow up to be of different orientation instead of moving the car, this makes setup and analysis much less confusing. This is how I tend to do wings with AoA etc.

Cheers,
Darren