Hybrid Airfoil Design Method to Simulate Full-Scale
Ice Accretion Throughout a Given a Range
F. Saeed, M.S. Selig and M.B. Bragg
University of Illinois, Urbana, Illinois 61801
ABSTRACT
A design procedure is presented for hybrid airfoils with
full-scale leading edges and redesigned aft sections
that exhibit full-scale airfoil water droplet-impingement
characteristics throughout a given angle of attack
or a range. The design procedure
is an extension of a previously published method in that
it not only allows for subcritical and viscouls-flow analysis
in the design but is also capable of off-design
droplet-impingement simulation through the use of a flap
system. The limitations of the flap-system-based design for
simulating both on- and off-design full-scale
droplet-impingement characteristics and surface velocity
distribution are discussed with the help of specific design
examples. In particular, this paper present sthe design of two hybrid airfoils at two different angles of attack, such that
they simulate both the full-scale velocity distribution as well
as droplet-impingement characteristics at the respective design
angles of attack. Both of the hybrid arifoils are half-scale
airfoil models with the nose section matching the full-scale
coordinates of the Learjet 305 airfoil back to 5% chord on the
upper surface and 20 chord on the lower surface. The effect
of flap deflection and droplet size on droplet-impingement
characteristics is also presented to highlight the important
limitations of the present method both on- and off- design.
This paper also discusses important compromises that must be
made to achieve full-scale ice accretion simulation throughout
a desired a range and suggests
alternatives such as applying a multipoint design approach.