Experiments Concerning the Creation of Streaky Structures Inside a Plane Water Jet, 1997 Engineering Conference Proceedings

In modern paper manufacturing free liquid jets are used to distribute the fibre suspension to the paper machine. It is believed that the homogeneity of the jet flow is of vital importance to obtain a good quality paper. The present investigation has been undertaken in order to better un-derstand the development of free, plane liquid jets.

Experiments have been made with water emanating from two different nozzles, a plane channel flow nozzle giving a nearly parabolic outflow velocity distribution and a slit nozzle which closely approximates an inviscid jet. Both types of flow have been visualized. The visualization of the jet emanating from a channel showed that a strong streamwise streaky structure was created inside the jet a distance downstream the nozzle. These streaks do not orig-inate from the nozzle but instead from the break-up of two-dimensional waves on the jet travelling in the streamwise direction. This streaky structure could not be found at any velocity (<15 m/s)="" in="" the="" jet="" emanating="" from="" the="" slit="" nozzle,="" and="" is="" therefore="" believed="" to="" be="" a="" result="" of="" the="" ve-locity="" profile="" relaxation,="" which="" only="" occurs="" in="" the="" channel="">