Master Thesis 2015-2016
Title: “Fluid-structure interaction simulations of separated
flows through Detached Eddy Simulations”
Laboratory: ULg-MTFC, ULg-AEA
Location: ULg
Date: February - June 2016 (early start recommended)
Target sections: Aerospace Engineering, Engineering Physics
Contacts: Vincent Terrapon
Advisors: Vincent Terrapon, Greg Dimitriadis
BACKGROUND
When flexible structures are subjected to a flow, small deformations due to aero-
dynamic forces can be amplified by the interaction between the structure motion
and the flow. This phenomenon is called flutter. If the flow speed is large enough,
structural damping might be insufficient to damp out the motion, which can lead
to catastrophic failure of the structure. Therefore, it is critical to account for flut-
ter in the design of those structures.
In the case of aircraft wings, a general type of flutter is characterized by the in-
teraction of pitch and plunge dynamics. In particular, small rotations of the wing
along its axis change the angle of attack and correspondingly the lift on the sur-
face. This is then accompanied by a simultaneous vertical bending of the wing.
Dynamic stall is a phenomenon characterized by periodic flow separation and reat-
tachment along the airfoil. The flow separation can be either partial or complete.
When dynamic stall takes place around flexible structures, a strong coupling be-
tween the flow and the structure can lead to stall flutter, i.e., large oscillations,
in particular along the pitching direction. Stall flutter plays an important role in
helicopter blades, wind turbine blades, and low stiffness wings operating at high
angle of attack. Despite numerous studies of the phenomenon, it is still very hard
to predict.
In applications of interest, the Reynolds number is typically large and the flow is
thus turbulent. Modeling turbulence is one of the major challenges in flow simula-
tions. To limit the computational cost, unsteady Reynolds-Averaged Navier-Stokes
simulations (URANS) are typically used. However, the RANS models are in gen-
eral inaccurate for separated flows that are created by large structure displacement
and/or deformation. A more accurate but also computationally more expensive
approach is required. Detached eddy simulations (DES) offer a good compromise
between accuracy and computational cost. The use of DES has proven quite suc-
