High-fidelity aeroelastic simulation of flexible wings inseparated flows

An efficient high-fidelity FSI method is developed for aeroelastic simulations of highly deformable streamlined
structures in separated flows with a non-constant cross-section over the structure span. The method is the further
development of our Nektar++/SHARPy FSI solver [1] to support non-constant sectional geometry over the
structural span as well as introducing correction factor for tip loss effect. The FSI solver has implemented in
Nektar++ [2] framework where the Navier-Stokes equation is discretized and solved using the high-order
spectral/hp element method. Large-Eddy Simulation (LES) method is used to resolve the turbulent structures in
highly separated flow condition and accurately predict the fluid forces on the structure. To reduce the
computational cost of LES simulation over the slender structure, the thick-strip method [3] is adopted where the
full 3D fluid domain is represented with series of separated smaller domains, each of which has a finite thickness
in the spanwise direction. Having the finite thickness for the strips enables capturing local 3D wake turbulent
while representing the full 3D domain with a finite number of smaller domains reduces the overall computational
cost of LES simulation over the slender structure. The thick strips are separated domains that implicitly connected
via the structural dynamics. Hence, a correction factor based on the calculated circulation in each strip is
introduced to take into account the tip-loss effect. To support independent geometry and meshes for each strip,
the hybrid parallelism approach [4] of Nektar++ is further modified which enable having non-constant cross-
sections over the span. Large-deformation dynamics of the structure is modelled using a geometrically-exact
composite beam finite-element model [5]. Simulation results of deformation of NREL5 MW reference wind
turbine blade [6] in high angle of attack with large separating flow over the blade is presented and the
computational challenges and requirements for such simulations are discussed in the present research.
REFERENCES
[1] M. Lahooti and R. Palacios and S.J. Sherwin, “Thick Strip Method for Efficient Large-Eddy Simulations of Flexible
Wings in Stall”. In AIAA Scitech 2021 Forum,p. 0363 (2021).
[2] D. Moxey and C.D. Cantwell and Y. Bao and A. Cassinelli and G. Castiglioni and S. Chun and E. Juda and E. Kazemi,
and K. Lackhove and J. Marcon and G.Mengaldo, “Nektar++: Enhancing the capability and application of high-fidelity
spectral/hp element methods”. Compu. Phys. Commu., 249, p.107110 (2020).
[3] Y. Bao and R. Palacios and M. Graham and S. Sherwin, “Generalized thick strip modelling for vortex-induced
vibration of long flexible cylinders”. J Comput. Phys, 321, pp.1079-1097. (2016).
[4] A. Bolis, Fourier spectral/hp element method: investigation of time-stepping and parallelisation strategies, PhD
dissertation, Imperial College London, (2012).
[5] A. del Carre and A. Muñoz-Simón and N. Goizueta and R. Palacios, “SHARPy: A dynamic aeroelastic simulation
toolbox for very flexible aircraft and wind turbines.”, J. Open Source Softw., 4(44), p.1885. (2019)
[6] J. Jonkman and S. Butterfield and W. Musial and G. Scott., “Definition of a 5-MW reference wind turbine for offshore
system development (No. NREL/TP-500-38060).”, National Renewable Energy Lab.(NREL), Golden, CO, United States,
(2009)