topmost pipe row r 1 farthermost from the fourdrinier wire are last in the flow direction fig3 shows a turbulence generator for a gap former according to another embodiment of the invention in this instance the stepped expansion 16 located between the narrow initial part 15 of the turbulence pipe 14 c 1 14 c 4 and the wide latter part 17 thereof is in all four superimposed rows r 1 r 4 of turbulence pipes in the flow direction at one and same distance from the slice opening 13 of the headbox instead the superimposed turbulence pipes 14 c 1 14 c 4 have different cross sections so that the cross section areas of the topmost and the lowermost turbulence pipes 14 c 1 and 14 c 3 are smaller than the cross section areas of the two centermost turbulence pipes 14 c 2 and 14 c 3 the greater the cross section of the flow duct the greater in dimension is the turbulence generated in the pipe a turbulence of a greater dimension also slows down more slowly than a turbulence of a smaller dimension a turbulence generator as in fig3 comprises further three trailing elements 20 a 1 20 a 3 fastened as extensions to necks 18 separating the three superimposed.