Strange axial velocity distribution in swirling flow
 

Hi all,
I am simulating swirl flow burner. The burner has central fuel jet and an swirling air which comes from the annulus. The central jet has velocity of 32.7 m/s in the axial direction. The swirling air has bulk axial and tangential velocity of 38.2 and 19.1 m/s. I use velocity inlet boundary for both fuel and swirling air flow. I use cylindrical component to specify swirling air boundary condition. I specify axial and tangential velocity while giving radial and angular velocity =0.00. When I perform calculation, I strangely get regions of high axial velocity and low velocity regions which are diametrically opposite as shown in the figure. I don't know why this happens, I believe axial velocity should be uniform for the entire annulus. If someone could tell me where I am wrong or explain this strange distribution it will be very useful for me

Thank you