 ## Fluids

• cehangir
Subscriber
Hi,

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.

Thanks
• Karthik R

Hello,

Thank you.

Best Regards,

Karthik

• klu
Ansys Employee

Hi,

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.

• DrAmine
Ansys Employee

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

• cehangir
Subscriber

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
Subscriber

Hi,

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 ?

• DrAmine
Ansys Employee

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.

• SaiKiran
Subscriber

Hi,

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

thanks & regards,

saikiran 