Optimization and Computational Fluid Dynamics - Department of ...

2 A Few Illustrative Examples of CFD-based Optimization 19
maximal while keeping a minimal pressure loss. A set of automatized numerical
tools are used together to solve this problem involving mesh generation,
CFD, an in-house C++ implementation of EAs, a shell-script and complementary
C programs for automatization and parallelization (Sect. 2.3).
Case B introduces the optimization of the flame shape of a laminar burner.
The fuel/air ratio in a primary and a secondary inlet vary and the objectives
are to reduce the pollutant (CO) emission at a prescribed distance from the
injection plane and to obtain the most homogeneous temperature at the same
location (Sect. 2.4).
In Case C, the model parameters of the k–ω engineering turbulence model
from Wilcox [79] are studied for Reynolds-Averaged Navier-Stokes (RANS)
computation. The objective in this work is to fit the parameters of the model
using optimization, in order to better predict the time-averaged turbulent
velocity profiles in channel flows (Sect. 2.5).
The applied multi-objective Evolutionary Algorithm (MOEA), based on
the concept of Pareto dominance, is described next. In the following sections,
the model problems are introduced first, putting into evidence the requirements
for the choice of an adequate optimization strategy. The practical
computational methodology for mesh generation, CFD solution and parallelization
are presented afterwards. Results are then shown and discussed
followed by concluding remarks.
2.1.2 Heat Exchanger Optimization (Case A)
Improving the performance of an existing configuration often involves optimization.
The optimal placement of the heat sources or sinks in a channel,
a cavity or a heat exchanger may affect dramatically the performance of the
device. In these circumstances, CFD have a high potential to easily explore a
large number of different configurations. As a whole, optimization of configurations
involving the coupled simulation of flow and heat transfer remains
a fairly new field of research.
Heat exchange through smooth and corrugated walls has been for example
investigated in [22]. Shape improvement of a cylinder with heat transfer was
carried out in [15]. The optimal shapes of fins and pins inside heat exchangers
have been examined by various authors [3, 12, 21, 23, 49]. Tiwari et al. [75]
have studied different angles of attack for the delta winglets mounted on the
fin-surface on top of oval-shaped tubes. Heat transfer of finned and non-finned
circular and elliptic tubular arrangements are investigated numerically in [57]
to maximize the total heat transfer rate. The flow through a heated pipe with
an inserted twisted tape was examined in [46] for different slopes. This analysis
is based on the entropy production minimization [9]. Multi-parameter
optimization coupled with CFD was investigated in [76] to maximize the performance
of a heat sink. Foli et al. [31] and Okabe et al. [66] have obtained