Computation of high-lift aerodynamics using unstructured grids and Reynolds-stress turbulence models

Marques, SP

Abstract

The computation of high-lift flows poses considerable challenges to the aerodynamicist.
The work presented in this thesis describes the development of
an efficient unstructured grid generation method for high lift flows and the
application of Differential Reynolds Stress Models (DRSM).
The method described in this thesis, separates the grid generation process
into two steps: generation of the anisotropic regions and isotropic grid generation.
All surfaces are triangulated as part of the anisotropic grid generation
process. The user can also specify the wake regions. Using surfaces or wakes,
the algorithm computes the normals to the surfaces and distributes new points
along those directions. This initial grid is connected to the outer boundaries.
The cells connecting the anisotropic grid with the outer boundaries are continuously
refined using an edge-splitting algorithm that creates new computational
cells, grid points and cell connectivities simultaneously.
The second part of this research involves the assessment of two DRSM
against a k — e model. The validation study included the Launder-Rodi-Reece
(LRR) DRSM and the Speziale-Sarkar-Gatski (SSG) DRSM. The Reynoldsaverage
Navier-Stokes (RANS), are solved explicitly using a cell centred finitevolume
scheme.
The focus of the validation study, are high-lift configurations tested as part
of the U.K. National High-Lift Programme. The aerofoils considered include a
3, 4 and 5-element configuration, designated NHLP L1/T2, NHLP L1/T7 and
NHLP L1/T8 respectively.
The results for the L1/T2 and L1/T7 aerofoils show only marginal differences
on the predicted aerodynamic loads. The results for the L1/T8 show
significant differences between both types of models, with the LRR exhibiting
the closest agreement with experimental data. Results indicate that only in these extreme cases, the advantages of a Differential Reynolds Stress Model
influence the aerodynamic loads results. However in most cases the DRSMs
produced a better representation of the flow physics.

Citation

Marques, S. Computation of high-lift aerodynamics using unstructured grids and Reynolds-stress turbulence models. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Aug 18, 2021
• Additional Information: Funders : Engineering and Physical Sciences Research Council (EPSRC)
• Award Date: Jan 1, 2008