In the present study, the vortex dynamics associated with flapping wing motion is reviewed. Smoke flow visualization and phase-locked PIV measurement of velocity flow field generated by the simple flapping motion of the rigid wings of different planform shapes is reported in this paper. To understand the effect of flexibility on the strength of the leading edge vortex (LEV), one flexible wing of rectangular shape was also investigated. The LEV formed due to flapping motion is captured and quantified. The relative strength of the LEV in terms of circulation and averaged vorticity distribution is presented for different rigid wing planforms and one flexible rectangular wing. @en