Calculating swirl angular velocity for combustion

  • Last Post 15 January 2019
cehangir posted this 09 August 2018



I am using ANSYS Fluent for combustion problem with swirl in 2D.


At the moment, I know the air going in the system is 15 m/s and the diameter of the duct is 0.3 m with 45 degree fins to generate swirls.


Can someone help me finding the swirl angular velocity (rad/s) that I should input in Fluent. If not, can someone tell me how swirl angular velocity is calculated in rad/s, and what information is generally need.



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Kremella posted this 10 August 2018


Could you please elaborate a little more about your problem? Can you not specify normal velocity and the 45 degree fins will deflect the flow internally when Fluent solves your model? What I don't understand is, I guess, your geometry? Could you please help us understand your problem better?

Thank you.

Best Regards,


klu posted this 10 August 2018


How about switching to magnitude and direction settings? I would think to put 15 m/s as the magnitude. Assume no radial component thus axial and swirl components are equal since the fins turn 45 degrees.

abenhadj posted this 13 August 2018

If you do not know anything about inflow then just stick to what klu said and assume normal inflow direction.

Best regards, Amine

cehangir posted this 13 August 2018

I can use normal flow. Unfortunately, my geometry is 2D. Therefore I dont have physical 45 degree fins in the inlet. 


That is why I want to include the expected swirl in the inlet. 

cehangir posted this 13 August 2018


Can you elaborate how I can do that by switching to direction and magnitude setting. 

Considering I have velocity as 15m/s, what will be the direction components for the axial and swirl component for 45 degree? 

I have an additional information that the swirl No. is 0.79. Can I use it in some way to give direction ?

abenhadj posted this 13 August 2018

Swirl number is the ratio of flow rate of angular momentum to flow rate of axial momentum. 

Velocity in cylindrical coordinate is V= r*e_r+(r*tehta)*e_theta+axial*e_axial with e_r, e_theta and e_axial the main cylindrical direction.

Moreover radial velocity=u cos (theta) + v sin(theta), tangential velocity = -u sin(theta) + v cos(theta) und axial velocity is the velocity into the rotational axis.

Best regards, Amine

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  • SaiKiran
SaiKiran posted this 15 January 2019


Can you please elaborate u and v components in the radial and tangential velocity. i am also working on the similar problem

thanks & regards,