Simulation by ansys cfx for a ceilng fan balde

wai325 · March 11, 2015, 06:27

I wan simulating a ceiling fan for my final year project.
I using ansys cfx for it.
Is it correct that i using Immersed solid as the fan when setting up my simulation? and how can I set the rotational direction? I only able to set the rotating axis but i not sure either it was rotating in clockwise or anticlockwise.
And how can i plot a velocity graph to calculate the flow rate under the fan?
Hope some experts can help me...thx

monkey1 · March 11, 2015, 06:35

Immersed solid has some serious constraints as to the applicable cases.
I would solve this problem by putting the fan in a cylindrical domain, that is connected to the rest by interfaces. Then I would define the cylindrical domain with the fan as rotating domain with the desired rotational speed.

wai325 · March 11, 2015, 06:54

Quote:

Originally Posted by monkey1

Immersed solid has some serious constraints as to the applicable cases.
I would solve this problem by putting the fan in a cylindrical domain, that is connected to the rest by interfaces. Then I would define the cylindrical domain with the fan as rotating domain with the desired rotational speed.

What u mean by using a cylindrical domain? I have enclosed my fan with a cylinder and setting it as the fluid domain. I was new in ansys simulation, and I was following this tutorial.
https://www.youtube.com/watch?v=l5IJEpPDyxs
how can i set my rotational direction? or any other advise? thx for ur info.

monkey1 · March 11, 2015, 08:50

I Mean that ur fan is included in a (small) cylindrical domain that covers just the fan geometry. That cylindrical (and rotating) domain is then included in a bigger static domain representig your fluid that should be set in motion by the fan (maybe the picture attached shows better what I mean.

And to define a rotation you have to define the cylindrical part as separate domain. There under the basic settings tab you have the ioption "DOmain Motion" where you can define a rotational axis as well as a rotation speed.

The Direction of the rotation is according to the right hand rule, meaning:
if Z is the rotation axis then a positive roattion speed makes the whole thing rotate from the postitive x-axis to the positive y axis anticlockwise
if y is the rotation axis then its from the z to the x anticlockwise
and for x as axis its from y to z anticlockwise.

Was this what you wanted to know?

wai325 · March 11, 2015, 15:47

Quote:

Originally Posted by monkey1

I Mean that ur fan is included in a (small) cylindrical domain that covers just the fan geometry. That cylindrical (and rotating) domain is then included in a bigger static domain representig your fluid that should be set in motion by the fan (maybe the picture attached shows better what I mean.

And to define a rotation you have to define the cylindrical part as separate domain. There under the basic settings tab you have the ioption "DOmain Motion" where you can define a rotational axis as well as a rotation speed.

The Direction of the rotation is according to the right hand rule, meaning:
if Z is the rotation axis then a positive roattion speed makes the whole thing rotate from the postitive x-axis to the positive y axis anticlockwise
if y is the rotation axis then its from the z to the x anticlockwise
and for x as axis its from y to z anticlockwise.

Was this what you wanted to know?

i have set it to rotate anticlockwise as wat i wan. and nw the result showing me hw the airflow. May i know hw can i obtain the velocity graph or table to show me the volume flow rate of the ceiling fan that i designed?

ghorrocks · March 11, 2015, 18:45

Monkey is right, this should be done using rotating frames of reference; not an immersed solid model (this seems to be a common mistake on the forum, several people make this mistake it appears....)

Do the CFX tutorials on rotating machinery, for instance the rotor/stator models. They show how to model turbomachinery. That will give you the basic idea of how to model your fan.

wai325 · March 12, 2015, 00:34

Quote:

Originally Posted by ghorrocks

Monkey is right, this should be done using rotating frames of reference; not an immersed solid model (this seems to be a common mistake on the forum, several people make this mistake it appears....)

Do the CFX tutorials on rotating machinery, for instance the rotor/stator models. They show how to model turbomachinery. That will give you the basic idea of how to model your fan.

where can i get the tutorial for RFR? and is it the cylindrical fluid volume enclose the fan is rotating or the fan domain is rotating?

wai325 · March 12, 2015, 00:38

Quote:

Originally Posted by monkey1

I Mean that ur fan is included in a (small) cylindrical domain that covers just the fan geometry. That cylindrical (and rotating) domain is then included in a bigger static domain representig your fluid that should be set in motion by the fan (maybe the picture attached shows better what I mean.

And to define a rotation you have to define the cylindrical part as separate domain. There under the basic settings tab you have the ioption "DOmain Motion" where you can define a rotational axis as well as a rotation speed.

The Direction of the rotation is according to the right hand rule, meaning:
if Z is the rotation axis then a positive roattion speed makes the whole thing rotate from the postitive x-axis to the positive y axis anticlockwise
if y is the rotation axis then its from the z to the x anticlockwise
and for x as axis its from y to z anticlockwise.

Was this what you wanted to know?

Is it mean that i have to create a cylinder jz enclose my geometry and follow by a box enclose all of them to be the static fluid domain?

monkey1 · March 12, 2015, 02:37

Yes you have the Fan cylinder and around ambient air in a box (or whatever shape desired) domain, if you want to model the effect of the fan on the sourrounding atmosphere.

wai325 · March 12, 2015, 03:39

Quote:

Originally Posted by monkey1

Yes you have the Fan cylinder and around ambient air in a box (or whatever shape desired) domain, if you want to model the effect of the fan on the sourrounding atmosphere.

Do you have any tutorial on setting the cylinder to be rotating frame? then i have to set the fan to be solid domain?

monkey1 · March 12, 2015, 04:08

Got not tutorial sorry.
You do not need to model the fan. Just model fuid domains, where the fan is "empty space" and the surfaces representing the fan are then marked as Wall Boundaries.
As I told you to define the fan domain you just have to define the "Domain Motion" on the basic settings atb of the domain definition where you can define a rotational axis as well as a rotation speed.

March 11, 2015, 06:27	Simulation by ansys cfx for a ceilng fan balde	#1
wai325 New Member Pang Chun Wai Join Date: Mar 2015 Posts: 6 Rep Power: 11	I wan simulating a ceiling fan for my final year project. I using ansys cfx for it. Is it correct that i using Immersed solid as the fan when setting up my simulation? and how can I set the rotational direction? I only able to set the rotating axis but i not sure either it was rotating in clockwise or anticlockwise. And how can i plot a velocity graph to calculate the flow rate under the fan? Hope some experts can help me...thx

March 11, 2015, 06:35		#2
monkey1 Senior Member Join Date: Jul 2011 Location: Berlin, Germany Posts: 173 Rep Power: 15	Immersed solid has some serious constraints as to the applicable cases. I would solve this problem by putting the fan in a cylindrical domain, that is connected to the rest by interfaces. Then I would define the cylindrical domain with the fan as rotating domain with the desired rotational speed. wai325 and boloko like this.

March 11, 2015, 18:45		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	Monkey is right, this should be done using rotating frames of reference; not an immersed solid model (this seems to be a common mistake on the forum, several people make this mistake it appears....) Do the CFX tutorials on rotating machinery, for instance the rotor/stator models. They show how to model turbomachinery. That will give you the basic idea of how to model your fan. boloko likes this.

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March 12, 2015, 02:37		#9
monkey1 Senior Member Join Date: Jul 2011 Location: Berlin, Germany Posts: 173 Rep Power: 15	Yes you have the Fan cylinder and around ambient air in a box (or whatever shape desired) domain, if you want to model the effect of the fan on the sourrounding atmosphere.

March 12, 2015, 04:08		#11
monkey1 Senior Member Join Date: Jul 2011 Location: Berlin, Germany Posts: 173 Rep Power: 15	Got not tutorial sorry. You do not need to model the fan. Just model fuid domains, where the fan is "empty space" and the surfaces representing the fan are then marked as Wall Boundaries. As I told you to define the fan domain you just have to define the "Domain Motion" on the basic settings atb of the domain definition where you can define a rotational axis as well as a rotation speed.