Implicit Large Eddy Simulation (ILES) with high-resolution and high-order computational
modelling has been applied to flows with turbulent mixing and combustion.
Due to the turbulent nature, mixing of fuel and air and the subsequent combustion
still remain challenging for computational fluid dynamics. However, recently ILES, an
advanced numerical approach in Large Eddy Simulation methods, has shown encouraging
results in prediction of turbulent flows. In this thesis the governing equations
for single phase compressible flow were solved with an ILES approach using a finite
volume Godunov-type method without explicit modelling of the subgrid scales. Up to
ninth-order limiters were used to achieve high order spatial accuracy.
When simulating non chemical reactive flows, the mean flow of a fuel burner was compared
with the experimental results and showed good agreement in regions of strong
turbulence and recirculation. The one dimensional kinetic energy spectrum was also
examined and an ideal k−5/
3
decay of energy could be seen in a certain range, which
increased with grid resolution and order of the limiter. The cut-off wavenumbers are
larger than the estimated maximum wavenumbers on the grid, therefore, the numerical
dissipation sufficiently accounted for the energy transportation between large and
small eddies. The effect of density differences between fuel and air was investigated
for a wide range of Atwood number. The mean flow showed that when fuel momentum
fluxes are identical the flow structure and the velocity fields were unchanged by
Atwood number except for near fuel jet regions. The results also show that the effects
of Atwood number on the flow structure can be described with a mixing parameter.
In combustion flows simulation, a non filtered Arrhenius model was applied for the
chemical source term, which corresponds to the case of the large chemical time scale
compared to the turbulent time scale. A methane and air shear flow simulation was
performed and the methane reaction rate showed non zero values against all temperature
ranges. Small reaction rates were observed in the low temperature range due to
the lack of subgrid scale modelling of the chemical source term. Simulation was also
performed with fast chemistry approach representing the case of the large turbulent
time scale compared to the chemical time scale. The mean flow of burner flames were
compared with experimental data and a fair agreement was observed
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