The structure of electrohydrodynamic (EHD) flows in a variable electric field has been investigated based on computer simulation of EHD flows in a needle-plane electrode system. The characteristic frequency interval of a feed sine-wave voltage with an amplitude of 5 kV has been considered. Changes in the charge and velocity structures of EHD flows are described, and the characteristic features of the flows versus feed voltage frequency are presented. The periodicity of such EHD flows is demonstrated.