Experimental and Numerical Study of Swirling ... - Solid Mechanics

Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke
Marine Diesel Engines
Chapter 6
Numerical Modeling
This chapter presents the results from the numerical modeling of the swirling flow
test case. Unsteady simulations are conducted using two RANS based approaches
and the results are compared with the experimental data. The simulations results
only represent the case with fully open cylinder intake port and at Reynolds
number of 65,000. A discussion has also been made on the possible approaches for
improving the simulation results.
The results of the numerical models included in this chapter are those
obtained until the time of writing this thesis. For mesh generation, Ansys ®
GAMBIT v2.4 is used and for CFD processing Ansys ® FLUENT v12.1 is used.
The post processing of the numerical data is done in Fieldview ® v 12.
The computational domain does not include the guide vanes and the inlet to
the domain is defined at a radial distance of 200 mm from the axis of
rotation (Figure 6.1). In the experimental setup the inlet to the setup is at a
radial distance of 300 mm with guide vanes mounted at 250mm radial
distance from the cylinder axis/ axis of rotation (Figure 4.1). This is adopted
to avoid the inlet to be in the region with large wake effects behind the guide
vanes and also not close to the contraction section. The LDA measurements
in section 4.1 show a very small wake effect at this radial distance. Another
purpose is to see if it is possible to achieve good results by neglecting the
guide vanes region in the computational mesh and defining the magnitude
of radial and tangential velocity components at some radial position after the
guide vanes region. The computational mesh has Y-axis as its rotational axis,
therefore, the velocity component along Y-axis represents the axial
component and for velocity component along Z-axis it is vice versa.
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Numerical Modeling