Resumo:
This work numerically investigates new interference patterns on flows around two
circular cylinders aligned in tandem at subcritical Reynolds number regime. The origin
of these interference patterns is hitched to surface roughness effects; consequently, the
interactions viscous wake-body and viscous wake-viscous wake establish new vorticity
dynamics for the problem. Overall, the numerical results reveal the potentialities of the
present numerical approach to capture drag reduction accompanied of base pressure
increasing, intermittence of vortex shedding and wake destruction under certain
interference patterns. There is a lack of data published in the literature discussing
roughness interference on flows around cylindrical structures in cross flow, which
motived the present study. The analysis of the main numerical results enables important
conclusions and, mainly, contributes to science evolution. Two contributions of this
work can be highlighted: (i) implementation of an in-house vortex code to include
surface roughness effects from a two-dimensional Lagrangian vortex method with LES
type turbulence modeling, and (ii) implementation and parallel programming of the
vortex code using OpenMP with Fortran. The numerical results confirm that the present
model of surface roughness effects is much more sensitive than a simple two
dimensional turbulence modeling. However, the turbulence modeling provided earlier
the development of the model of surface roughness effects utilized in the present study.
The latter utilizes points set near every solid boundary combining the generation of
vortex elements and instantaneous change in the vorticity field into the boundary layer
by introducing momentum because of roughness protruding out of the surface.
