Turbulent flow control

Forskningsprojekt, 2018 – 2019

The energy consumption in an aircraft is mainly due to the aerodynamic drag
force that opposes an aircraft’s motion through the air. Almost 50% of total
drag is due to the viscous drag, which is directly related to the friction drag
of the aircraft caused by the interaction of the turbulent boundary layer flow
with the aircraft surface. Studies on the aircraft and turbulent boundary layer
interactions, together with developments of advanced flow control technologies,
can effectively reduce more than 40% of the viscous drag, which is equivalent
to about 15% of the total drag, and has, therefore major implications to energy
consumption of commercial aircraft. Saving 1% of fuel on a Boeing 737-800
would result in a 100 metric tons yearly fuel reduction. It would also decrease
the emission of pollutants by 318.7 tons of CO
2 , 123.9 tons of H
2
O, 2.122 tons
of NO
x , 98 kg of SO
2 and 56 kg of CO. Hence, even a small drag reduction
gives significant benefits 1 .
Since September 2016, my post-doc Atilla Altintas has been working in the
EU project DRAGY (“Drag Reduction via Turbulent Boundary Layer Flow
Control”). This project approaches the problem of turbulent drag reduction
through the investigation of active/passive flow-control techniques in turbu-
lent boundary layers. Turbulent Boundary Layer Control (TBLC) for drag
reduction is a relatively new technology made possible through the advances in
computational-simulation capabilities, which has improved our understanding
of the turbulence. Advances in micro-electronic technology have enabled the
fabrication of actuation systems capable of manipulating the turbulent fluctu-
ations. In order to achieve these goals the following objectives are defined in
DRAGY:
• To identify the characteristics of the flow perturbations that can be intro-
duced into the inner and/or outer regions of the boundary layer to inhibit
the drag-generating mechanisms.
• To develop advanced simulation tools and methods to analyze and study
turbulent boundary layers at large aircrafts.
• To enable the various concepts to be evaluated at an aircraft level, such
that an overall net energy saving can be achieved.