The flow induced motion (FIM) and energy conversion of cylinders with different cross sections are investigated using two-dimensional unsteady Reynolds-Averaged Navier-Stokes simulations in the Reynolds number range of 10,000 < Re < 130,000. The model for energy harvesting in FIM is established and verified by experimental measurements. For the PTC-cylinder (circular cylinder with passive turbulence control), square cylinder, Q-trapezoid I (quasi-trapezoid cylinder with the long edge as the windward side), and triangular prism, energy can be obviously harvested when Re > 30,000. The initial and upper branches of vortex induced vibration (VIV), transition from VIV to galloping, and galloping branch are clearly observed in the amplitude and frequency responses. The FIM responses of PTC-cylinder and Q-trapezoid I are stronger than the other cylinders. The maximum amplitude of 3.5D is achieved and 16 vortices are captured in one cycle in the fully-developed galloping branch. The optimum regime for energy harvesting is the VIV upper branch. And the PTC-cylinder and Q-trapezoid I have better performance on energy harvesting in FIM than other cylinders. The maximum energy efficiencies of 45.7% and 37.9% are achieved for Q-trapezoid I and PTC-cylinder respectively. Contrarily, the vibration of Q-trapezoid II (quasi-trapezoid cylinder with the short edge as the windward side) displays a quite different character with low amplitude and high frequency, and the vortex pattern is a constant 2S in the test Re range. (C) 2014 Elsevier Ltd. All rights reserved.