The rise of fully turbulent flow

Letter
Over a century of research into the origin of turbulence in wall-bounded
shear flows has resulted in a puzzling picture in which turbulence appears
in a variety of different states competing with laminar background flow1, 2,
3, 4, 5, 6. At moderate flow speeds, turbulence is confined to localized
patches; it is only at higher speeds that the entire flow becomes turbulent.
The origin of the different states encountered during this transition, the
front dynamics of the turbulent regions and the transformation to full
turbulence have yet to be explained. By combining experiments, theory and
computer simulations, here we uncover a bifurcation scenario that explains
the transformation to fully turbulent pipe flow and describe the front
dynamics of the different states encountered in the process. Key to
resolving this problem is the interpretation of the flow as a bistable
system with nonlinear propagation (advection) of turbulent fronts. These
findings bridge the gap between our understanding of the onset of
turbulence7 and fully turbulent flows8, 9.

http://www.nature.com/nature/journal/v526/n7574/full/nature15701.html?WT.ec_
id=NATURE-20151022&spMailingID=49830413&spUserID=ODcyMDUxMzY4NDES1&spJobID=7
82923215&spReportId=NzgyOTIzMjE1S0#affil-auth

view
A simple model captures the key features of the transition from smooth to
turbulent flow for a fluid in a pipe. The findings pave the way for
more-complex models and may have engineering ramifications.

http://www.nature.com/nature/journal/v526/n7574/full/526508a.html?WT.ec_id=N
ATURE-20151022&spMailingID=49830413&spUserID=ODcyMDUxMzY4NDES1&spJobID=78292
3215&spReportId=NzgyOTIzMjE1S0