
Research Axis: Nonlinear Effects in Fluid-Structure Interaction
Many fluid-structure interaction phenomena involve separated flows and,
therefore, a significant degree of nonlinearity. Furthermore, there can be
additional nonlinearity coming from structure, e.g. large deformations or
freeplay. As a consequence, nonlinear fluid-structure interaction is becoming a
research topic of increasing importance both for academia and for industry. The
Aeroelasticity and Experimental Aerodynamics Research Group of the University
of Liège carries out research on several areas involving nonlinear fluid-structure
interaction such as stall flutter and buffeting.
 Stall flutter
Stall flutter is an aeroelastic instability that can affect several types of aeroelastic
systems, such as helicopter and wind turbine blades. It is a Limit Cycle
Oscillation (LCO) that can cause significant vibration amplitudes, efficiency drops,
control difficulties, decrease in fatigue life and even failure.
The purpose of the present research is to investigate several different stall flutter
mechanisms that can occur simple aeroelastic systems, such as a rectangular
wing with two degrees of freedom in pitch and plunge.
A wing undergoing stall flutter in the ULg Wind tunnel, with PIV visualization
 Delta wing aeroelasticity
Limit cycle oscillations involving Delta wings are an important area of research
in modern aeroelasticity. Such phenomena can be the result of geometric nonlin
earity, aerodynamic nonlinearity or under-wing store nonlinearity. A series of
investigations of Delta Wing aeroelasticity by several researchers have
demonstrated that low speed LCOs can be obtained as a result of the interaction
of structural geometric nonlinearity with attached flow aerodynamics.
The purpose of the present research is to determine experimentally to what
extent structural and/or aerodynamic nonlinearities are important in causing
Limit Cycle Oscillations of a Delta wing at different steady angles of attack.
Delta wing undergoing Limit Cycle Oscillations in the ULg Wind Tunnel
 Future research
Further experiments are planned in the ULg Wind Tunnel in order to improve
the understanding of the aeroelastic behavior of bluff bodies, such as rectangular
and circular cylinders. Such research will also have application in civil
engineering.