Recent experimental investigations have shown that spanwise modulations of thebase flow may delay transition to turbulence. In this paper we explore the possibility togenerate streaks of much larger amplitude than previously reported by using a row of miniaturevortex generators (MVGs). Here, we present the first boundary layer experiment where streakamplitudes exceeding 30% have been produced without having any secondary instability actingon them. Furthermore, the induced drag due to the streaky base flow is quantified and it isdemonstrated that the streaks can be reinforced by placing a second array of MVGs downstreamof the first one. In this way it is possible to make the control more persistent in the downstreamdirection. We conclude that the specially designed set of MVGs, as a boundary layer modulator,is a promising candidate for successfully setting up robust and persistent streamwise streaks,which is a prerequisite for a successful flow control.
QC 20120411