Relative velocity in simpleSRFFoam

miku · November 4, 2008, 09:39

Hi, I have a question to simpleSRFFoam. I cannot find a definition of Urel. Relative to what is Urel? And why does simpleSRFFoam use Urel instead of U absolute?
Thanks in advance!

November 4, 2008, 10:21

Hi Miku,

Urel is the relative velocity in the rotational frame, the absolute velocity would then be:

Uabs = Urel + omega x R

where omega is the angular velocity vector and R the position vectro in rotational frame.

dmoroian · November 4, 2008, 10:35

Hi Miku,
Maybe you will find this answer satisfactory: relative velocity formulation

Dragos

miku · November 4, 2008, 11:26

Thanks for your answers!
If I have not defined a rotational frame and my rotational axis is equivalent to the z-axis of my stationary coordinate system, I am right that my relative velocity is equivalent to my absolute velocity?

miku

dmoroian · November 4, 2008, 11:51

Hi Miku,
The relative velocity is identical to the absolute one, when there is no transport velocity (in your case 0 rotation or 0 rpm).

Dragos

November 4, 2008, 09:39	Hi, I have a question to simpl	#1
miku New Member Miku Join Date: Mar 2009 Posts: 7 Rep Power: 17	Hi, I have a question to simpleSRFFoam. I cannot find a definition of Urel. Relative to what is Urel? And why does simpleSRFFoam use Urel instead of U absolute? Thanks in advance!

November 4, 2008, 10:21	Hi Miku, Urel is the relati	#2
paul_mathis Guest Posts: n/a	Hi Miku, Urel is the relative velocity in the rotational frame, the absolute velocity would then be: Uabs = Urel + omega x R where omega is the angular velocity vector and R the position vectro in rotational frame.

November 4, 2008, 10:35	Hi Miku, Maybe you will find	#3
dmoroian Senior Member Dragos Join Date: Mar 2009 Posts: 648 Rep Power: 20	Hi Miku, Maybe you will find this answer satisfactory: relative velocity formulation Dragos

November 4, 2008, 11:26	Thanks for your answers! If I	#4
miku New Member Miku Join Date: Mar 2009 Posts: 7 Rep Power: 17	Thanks for your answers! If I have not defined a rotational frame and my rotational axis is equivalent to the z-axis of my stationary coordinate system, I am right that my relative velocity is equivalent to my absolute velocity? miku

November 4, 2008, 11:51	Hi Miku, The relative velocit	#5
dmoroian Senior Member Dragos Join Date: Mar 2009 Posts: 648 Rep Power: 20	Hi Miku, The relative velocity is identical to the absolute one, when there is no transport velocity (in your case 0 rotation or 0 rpm). Dragos

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