Optimization and Computational Fluid Dynamics - Department of ...

22 Gábor Janiga
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Symmetry
Primary inlet Secondary inlet
Fig. 2.2 General configuration of the laminar burner (Case B). A methane/air mixture
enters through the primary and secondary inlets with a varying composition
and chemical reactions, and this within a reasonable computing time, even
for configurations close to practical ones.
2.1.4 Determination of Turbulence Model Parameters
Based on Optimization (Case C)
Turbulent flows are essential for a wealth of practical applications. Predictive
numerical tools are of course deeply needed to improve existing devices and
develop new configurations in the turbulent regime. The broad range of problems
underlying turbulent flows cannot be solved with a unique method. It is
therefore useful to identify different levels of modeling, describe their domain
of application and some characteristic features. Direct Numerical Simulations
(DNS) are only possible for simple configurations and low-Reynolds number
flows. Large-Eddy Simulations (LES) resolve the large structures of the flow
while the small scales are modeled. LES modeling becomes now feasible in
many situations due to the increase of computing power but remains an expensive
solution for industrial problems. In the RANS modeling, the balance
equations are averaged in time with respect to the turbulent fluctuations of
the flow variables. This averaging introduces higher-order moments which
cannot be computed without approximate closure schemes. Nevertheless, nu-
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