A flexible composite sheet (FCS) comprising a membrane, a substrate coupled to the membrane, and a plurality of ridges coupled between the membrane and the substrate, wherein a vibratory motion is induced from the flow to at least one segment of membrane spanning a distances, wherein a favorable pressure gradient aids the flow and an adverse pressure gradient opposes the flow; wherein the vibratory motion is reflected from at least one segment of the membrane to the flow, and wherein a reduction in fluctuations is caused in the flow pressure gradient and freestream velocity U except where the frequency is approximately equal to =U/s. The FCS has other flow control applications, such as a drag reduction when coupled to an aircraft wing.