Purpose <p>The vortex-induced vibration (VIV) responses of the bladeless hydro-turbine with an aspect ratio (<i>L/D</i>) of 200 for different mass ratios were investigated numerically using the wake oscillator model. The hydro-bladeless turbine is modelled as an Euler-Bernoulli beam with a fixed-free boundary condition.</p> Methods <p>The RMS crossflow displacement, time and frequency domain responses of the crossflow tip displacement are presented for two different materials (CFRP and mild Steel) having different mass ratios at three uniform flow velocities of 0.6 <i>m/s</i>, 0.8 <i>m/s</i>, and 1 <i>m/s</i>.</p> Results <p>The contour plots on the evolution of displacement with time and space revealed the existence of a standing wave response pattern for all the cases in the present study. The increase in the response and fluid-structure interaction increases the energy transfer from the fluid to the bladeless turbines, which entirely depends on mechanical vibrations for energy extraction. The type of energy extraction mechanism from the VIV of a structure depends on the area of the structure with the maximum amount of energy transferred from the fluid to the structure.</p> Conclusions <p>For steel and CFRP, piezoelectric and electromagnetic induction are most effective at flow velocities of 0.6 m/s and 1 m/s, respectively, where more energy transfer occurs. On the other hand, the power take-off system modelled as a linear damper mechanism, which is best suited for energy extraction from the location with maximum vibration (free end), performs best at flow speeds of 0.8 m/s for steel and 0.6 m/s for CFRP, where the energy transfer is maximum at the tip.</p>