hi every one� i have some
 

hi every one�
i have some question about MRFZones.C
in void Foam::MRFZone::addCoriolis(fvVectorMatrix& UEqn) const:

thanks
wayne

Hi Wayne, I think that in an
 

Hi Wayne,
I think that in an absolute velocity formulation, the Coriolis force (2rwxU_relative) and centripet force (rwxwxr) can be written as: rwxU

I hope this is helpful,
Dragos

...and mesh_.V() retuns the ce
 

...and mesh_.V() retuns the cell volume

Hi Dragos： i don` think so.
 

Hi Dragos：
i don` think so.if we write the moment equ in rotating frame, the velocity is relative velocity (W),and in the absolute frame the equation is without the coriolis force and centrifugal force.
in MRF:

rho*D(W_relative)/Dt=F(total,including pressure,viscosity)+omega×(omega×r)-2* omega × u


in absolute frame:
rho*D(U_absolute)/Dt =F

according to you should be

rho*D(U_aboslute)/dt= F+ * omega × U

i dont think it will be
rho*D(W_aboslute)/dt= F+ * omega × U

for the solver just treat one velocity not two

thanks alot
yours wayne

i am sorry, there is a "*" be
 

i am sorry, there is a "*" before "omega × U" for last two equ.it is typing error of mine

thanks
wayne

I had a vague memory in the ba
 

I had a vague memory in the back of my mind when I wrote the above post, but I've just dug for it and here it is...

In the absolute velocity formulation and for a steadily rotating frame the flow equations can be written as follows:

- continuity:

- momentum:

- energy:

where the relative velocity is:
and the transport velocity is:

You can also check the fluent user manual for it.

I hope this is helpful,
Dragos

Hi Dragos thanks a lot! i
 

Hi Dragos
thanks a lot!
i could understand it now�
the relative velocity is as calculating in the memeber function relativeflux,so moment eqution should be div(phi,u),is that right?

thanks
waye

Hi Wayne, This is exactly wha
 

Hi Wayne,
This is exactly what it is written in the momentum predictor:

tmp<fvvectormatrix> UEqn
(
<blockquote>fvm::div(phi, U)
+ turbulence->divR(U)

);
</blockquote>

Dragos

Hi Dragos but why the flow p
 

Hi Dragos
but why the flow pattern of the result looks like U is relative velocity

wayne

well Wayne, if it is like that
 

well Wayne, if it is like that I agree with you: it is strange.
Can you post a picture with an example?

Dragos

Hi dragos the result of mixv
 

Hi dragos
the result of mixvessl2D in tut looks likes the U is absolute velocity
http://www.cfd-online.com/OpenFOAM_D...your_image.gif

http://www.cfd-online.com/Open
 

http://www.cfd-online.com/OpenFOAM_D...your_image.gif

 

http://www.cfd-online.com/Open
 

http://www.cfd-online.com/OpenFOAM_D...ges/1/7177.jpg

Hi sorry i try a lot here i
 

Hi sorry
i try a lot
here is the result of mixvessl2D(vector on the rotor),you can see clearly the velocity profile relative to the omega
http://www.cfd-online.com/OpenFOAM_D...your_image.gif
and then is my case a 3d centrifugal impeller
a vector plot of U in the impeller z=1/2thick
http://www.cfd-online.com/OpenFOAM_D...your_image.gif
b vector plot on the blade
http://www.cfd-online.com/OpenFOAM_D...your_image.gif

mix2d http://www.cfd-online.c
 

mix2d
http://www.cfd-online.com/OpenFOAM_D...ges/1/7180.jpg

http://www.cfd-online.com/Open
 

http://www.cfd-online.com/OpenFOAM_D...part/happy.gif Lots of tries!
Well in the picture I can see, the vectors look ok to me!
Be careful to have pictures with dimensions of less than 50kb.

Dragos

a vector plot of U in the impe
 

a vector plot of U in the impeller z=1/2thick
http://www.cfd-online.com/OpenFOAM_D...ges/1/7182.jpg

b vector plot on the blade ht
 

b vector plot on the blade
http://www.cfd-online.com/OpenFOAM_D...ges/1/7184.jpg

c relative velocity (at the s
 

c relative velocity (at the same conditon) calculated by CFX
http://www.cfd-online.com/OpenFOAM_D...your_image.gif