  Vortex-Induced Vibrations (VIV) offer a safe, renewable, and environmentally
friendly energy source for energy harvesting. To enhance the energy harvesting
capability of the circular cylinder-based devices, the authors explore the
placement of the normal slit by determining the most effective slit offset
location from the cylinder's center. Using the open-source Computational Fluid
Dynamics (CFD) program OpenFOAM, a series of numerical simulations are
conducted to determine the utility of the slit placement on the circular
cylinder and how it influences (positively/negatively) the harvester's
performance for a 1-degree-of-freedom (1-DOF) VIV system. The study shows that
the slit-cylinder displays the three-branch VIV response (i.e. initial branch
(IB), upper branch (UB), and lower branch (LB)). At a Reynolds number of 150,
the cylinder with no slit exhibits the two-branch VIV response (i.e. IB and LB)
but lacks the upper branch. This is the first time the Upper Branch has been
acquired for such low Re flows. The results indicate that adding a normal slit
to the middle of the cylinder improves the alternating suction and blowing
phenomena. Offsetting it from the center towards the back stagnation point
suppresses the VIV and makes it unsuitable for energy harvesting applications.
While positioning the slit toward the front stagnation point improves
aerodynamic lift, and the cylinder sheds vortex closer to each other. It
enhances the amplitude of transverse oscillation and, consequently, the power
extraction. In addition, the peak energy transfer ratio for these scenarios is
comparable to that of the no-slit case but with a larger range of peak energy
transfer ratio values. It makes it suitable for energy harvesting applications.
