How to specify the swirl velocity condition ?

[jason_min]

I'm recently working on the simulation of a swirl burner configuration. And I would like to know how to specify a swirl velocity condition at boundary surface by using surfbo function ?
Does anyone have related information?
can we switch to a cylindrical coordinate system in Code_Saturne?

[Yvan Fournier]

Hello,

No, there are no cylindrical coordinates in Code_Saturne (and they would not be of much helpp in burners with multiple inlets, fro example).

Last time I needed a swirl, I used both surfbo and cdgfbo, using the following stages:

• - compute the center of the inlet (could be given as data if not subject to frequent change, or coded by computing the mean of face centers, weighted by the face surfaces for a more atomated version);
  -compute the (mean) normal to the inlet (may also be given if oriented in a simple manner);
  - for each face on the inlet, add a rotation term based on the cross product of the vector representing the distance between the face's center and the inlet's center and the normal to the inlet.

The term to be added can be either a velocity (simplest, but not optimal as is ignores wall friction), or a source term for cells just after the inlet (in which case you need to be careful in case multiple faces might contribute to the same cell, and "measure" the effective swirl in that area so as to adjust the swirl).

Regards,

Yvan