help how to simulate the velocity in the rotary atomizer

xjm659 · October 23, 2011, 10:00

,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, 18:03

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

xjm659 · October 24, 2011, 00:32

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, 01:28

I do not give my email out on the forum.

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

xjm659 · October 24, 2011, 02:26

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, 02:31

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, 03:20

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, 06:28

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.

October 23, 2011, 10:00	help how to simulate the velocity in the rotary atomizer	#1
xjm659 New Member GMXiao Join Date: Oct 2011 Posts: 4 Rep Power: 15	,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?

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October 23, 2011, 18:03		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	Can you show a drawing of the device and more description of how it works. I have no experience in rotary atomisers.

October 24, 2011, 00:32		#3
xjm659 New Member GMXiao Join Date: Oct 2011 Posts: 4 Rep Power: 15	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 ?

October 24, 2011, 01:28		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	I do not give my email out on the forum. Post a message, click "go advanced" then attach the image.

October 24, 2011, 02:31		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	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?

October 24, 2011, 03:20		#7
xjm659 New Member GMXiao Join Date: Oct 2011 Posts: 4 Rep Power: 15	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 .