Evaluating the Performance of Wall-Modelled Large-Eddy Simulation on Unstructured Grids
Typ
Examensarbete för masterexamen
Program
Naval architecture and ocean engineering (MPNAV), MSc
Publicerad
2020
Författare
Javadi, Mehran
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Large Eddy Simulation (LES) has become a promising CFD method for flows in
which turbulence plays a dominant role such as many complex engineering systems.
To contribute to further advances, in this work, the performance of Wall-Modelled
LES on unstructured grids is evaluated. Periodically arranged hills geometry is a
frequent experimental and numerical test case because of the possibility of studying
important fluid phenomena. The importance of study of this flow arise from separation
and reattachment points, and hence the whole flow is sensitive to the separation
process. In this work, WMLES is used to investigate the properties of a separated
flow in a periodic hill channel flow. The principal idea is to evaluate the sensitivity of
the predicting accuracy to grid resolutions. To do that, three mesh types including
triangle, polygon, and square prism meshes are employed in the study. Grid resolution
has also been considered by using four grid sizes - different cell-to-cell distance
- for each type of mesh. Twelve grids are used for the simulations and the results
are judged by existing reference data. The results are included for skin friction and
pressure coefficients, mean and vertical velocity, and kinetic energy profiles. The
results illustrate that WMLES predict the flow features accurately. The statistical
data elicited from the study illustrate a noticeable influence of grid topology on
the results and prove that meshing strategy plays a key role in accurate prediction.
Also, results illustrated a noticeable distinction in sensitivity between separation
and reattachment points. Regarding this, the reattachment point is highly sensitive
to the grid size.
Beskrivning
Ämne/nyckelord
Computational Fluid Dynamics , WMLES , Unstructured grids , Accuracy , OpenFOAM