CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   CFX (http://www.cfd-online.com/Forums/cfx/)
-   -   help how to simulate the velocity in the rotary atomizer (http://www.cfd-online.com/Forums/cfx/93667-help-how-simulate-velocity-rotary-atomizer.html)

xjm659 October 23, 2011 09:00

help how to simulate the velocity in the rotary atomizer
 
,I have a rotary atomizer whell (disc atomizer) with 36 channels and 5500rpm, I want to calculate the volecity in the outlet of the disc(the tip of the channels).

I used the mutilphase molde(air and water,standard freesurface model,homogenous model),3d rotary domain(just including the channel in the disc),steady flow in CFX, but the result is so different from the result by exprience fomula, it is much large(about 40% of the radial velocity).

If I just want to calculate the velocity in the tips of the channels ,does this model have any fetal error?
If have,what is it?
Then I want to calculate the diameter of the droplets and it's distribution near the channels,what should I do? If I add a stationary annual domain (water-air domain)outside the rotary domain to simulate the air outside the atomizer,is it right?

ghorrocks October 23, 2011 17:03

Can you show a drawing of the device and more description of how it works. I have no experience in rotary atomisers.

xjm659 October 23, 2011 23:32

i do not kown how to handout a picture in this forum, it is just a plain rotary atomizer with 36 channels , and 5500rpm, it's diameter is 420mm ,can you give me your email ?

ghorrocks October 24, 2011 00:28

I do not give my email out on the forum.

Post a message, click "go advanced" then attach the image.

xjm659 October 24, 2011 01:26

the drawing
 
1 Attachment(s)
rotary atomizer 5500rmp the max diameter is 420mm, the liquid is water , the pic is in the attchement, ,my model just include the flow domain (the empty partion of the wheel,from the center to the tips of the channels) thank you

ghorrocks October 24, 2011 01:31

You say it is steady state. Do you know it is steady state? There is a good chance that on the fluid time scales this flow is transient. You need to keep your mind open to this being transient.

You might be able to get a good estimate of the flow rate through this thing with careful simulation. Simulating the droplet generation in this device would be next to impossible in any CFD code.

What are you trying to learn with your model?

xjm659 October 24, 2011 02:20

thank you for your advice. I will try it later with transiant model. you said ''Simulating the droplet generation in this device would be next to impossible in any CFD code" Are you sure? What a pity. My boss demand it , as you know, only result ,no process and reason.
appreciate for you help and best wishes for you .

ghorrocks October 24, 2011 05:28

Quote:

Are you sure? What a pity. My boss demand it
Your boss only asks for the impossible? Looks like he his being generous to you :)

Have a look in the CFX documentation and literature about primary and secondary droplet breakup. When you understand all that you will see why your task is just about impossible.

But as I said you might be able to get the flow rate about right. Maybe that will be a good start.


All times are GMT -4. The time now is 14:22.