# Q. How does one specify a swirl velocity component at a CFX Inlet?A.To specify swirl at an inlet, one can make a local cylindrical coordinate system with its center at the center of the inlet. The Z axis of this coordinate system should be normal to the boundary surface. In the basic settings of the inlet, make sure of the reference to this new coordinate system. Then in boundary details, the velocity component in the Z direction will determine the mass flow. The radial component will most likely be zero.Create an expression for the azimuthal (theta) component if the swirl velocity is a function of the distance from the center of the inlet. This will use the variable "r" which is measured from the Axial direction (the Z axis) in the new coordinate system.The setup provides additional flexibility in setting the axes. Therefore one must, in Analysis Details, go to the Axis Definition and as the option choose Coordinate system. For the Rotation axis choose the third direction (i.e. "Coord 1.3").

 Q. How does one specify a swirl velocity component at a CFX Inlet?A.To specify swirl at an inlet, one can make a local cylindrical coordinate system with its center at the center of the inlet. The Z axis of this coordinate system should be normal to the boundary surface. In the basic settings of the inlet, make sure of the reference to this new coordinate system. Then in boundary details, the velocity component in the Z direction will determine the mass flow. The radial component will most likely be zero.Create an expression for the azimuthal (theta) component if the swirl velocity is a function of the distance from the center of the inlet. This will use the variable "r" which is measured from the Axial direction (the Z axis) in the new coordinate system.The setup provides additional flexibility in setting the axes. Therefore one must, in Analysis Details, go to the Axis Definition and as the option choose Coordinate system. For the Rotation axis choose the third direction (i.e. "Coord 1.3").