Hi I'm having trouble getting the UDF DEFINE_GEOM to work properly. I would like to use the UDF to make the bottom of a rectangular duct with air blowing deform into a different shape over time. I have compiled the UDF properly and have hooked it into fluent as outlined in the UDF user's manual. However, when I view the mesh motion, the bottom does not deform.

I would really appreciate your help. My e-mail is sxy_hit@163.com

My project is shown as follow. I will give you some file about my problem. Thank you!

The bottom of the duct is from (-5,-2.5) to (-5,2.5). the new position is defined by a parabola through (-5,-2.5), (0,-1) and (-5,2.5). The parabola is .

/************************************************** *********** * * defining parabola through points (-5,-2.5),(0,-1),(5,-2.5) * ************************************************** ***********/ #include "udf.h"

DEFINE_GEOM(parabola,domain,dt,position) { /*set y=-0.06x^2-1*/ position[1]=-0.06*position[0]*position[0]-1; }

Hi, im not sure it will work this way...are you sure that define_geom can be uses to move nodes? I know it is used to introduce an algebric constain but not to move nodes. I would try using grid_motion and update your nodes cordinates form the rectangular to parabola edge.Luca