Abraham, Anoop Sam and Banerjee, Raja
(2019)
Development of a Non-Reacting LES
Solver for Unstructured Grid.
Masters thesis, Indian institute of technology Hyderabad.
Abstract
The present thesis consists of development of an LES based explicit solver which could
simulate non reacting flows. The numerical simulation is carried out using Dynamic
k equation subgrid scale model. Along with solving the Navier- Stokes equation a
convection diffusion equation for mass fraction is also solved which would correct
the equivalent density.The length and time scales for the mesh and simulations are
calculated based on the Kolmogorov’s hypothesis and the CFL number is calculated
accordingly.An explicit solver is used because of the fact that the calculated CFL
number is extremely lower than 1.
Two cases were validated using the above developed code, first is the case of an
axisymmetric turbulent jet of air entering a quiscent atmosphere and the second one
is the case where a variable density fluid(here Helium) entering the same quiscent air.
The development of the plumes are captured.The development of the plume structures
of both the cases are discussed. The averaged velocity profiles are also discussed. The
mean velocity , turbulent fluctuations and Reynolds stresses are plotted. A brief study
on the parallelisation technique used in OpenFoam is also done. Finally using the
fluctuating data from both simulations the energy spectrum graphs are plotted which
ensures that the mesh is suitable for the present study.
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