Electrowetting-induced microwater droplet transports in parallel-plate and open-plate electrowetting-on-dielectrode (EWOD) have been studied numerically. The governing equations for three-dimensional transient microfluidic flow are solved by a finite volume scheme with a two-step projection method on a fixed computational domain. The free surface of the droplet is tracked by the coupled level set and volume-of-fluid (CLSVOF) method with the surface tension force determined by the continuum surface force (CSF) model. The results of the numerical model have been validated with published experimental data and the physics of droplet transport have been investigated. A parametric study has been performed in which the effects of voltage amplitude, channel gap, and electrode size have been examined.