In 2-D fluent gives an option in the drop down menu for plotting contours of streamlines, but in 3-D how could one get the stream line patterns ( Stream surfaces rather ) Any idea ? Thanks, Ajay

You can't, streamlines (countours of the streamfunction) are only defined/available in 2D. In 3D you'll have to use path-lines.

Incompressible flow - R.L Panton has a section on streamlines and streamsurfaces for 3-D flow Its chapter 12 in my old edition. I tried using Path lines but not getting good results. ( path lines would represent streamlines in 3d only in the steady case ) Regards, Ajay