Flow over a circular cylinder with a flexible splitter plate

In the present work, we study the flow field around, and forces acting on, a circular cylinder with an attached flexible splitter plate/flap. Two cases of flap length , namely, and have been investigated focusing on the effect of variations in flap flexural rigidity,. We find that for a range of and Reynolds numbers, a non-dimensional bending stiffness collapses flap motion and forces on the system well, as long as 5000$]]>. In the flap case, two periodic flap deformation regimes in the form of travelling waves are identified (modes I and II), with mode I occurring at and mode II at lower values (<![CDATA[$K^{\ast }). In the flap case, we find a richer set of flapping modes (modes A, B, C and D) that are differentiated by their flapping characteristics (symmetric/asymmetric and amplitude). Force measurements show that the largest drag reduction occurs in mode I and mode C , which also correspond to the lowest lift and wake fluctuations, with the mode C wake fluctuations being lower than even the rigid splitter plate case. In contrast, the highest fluctuating lift, in both cases, occurs at higher, when the wake frequency is close to the first structural bending mode frequency of the flap. The observed rich range of flap/splitter plate dynamics could be useful for applications such as drag reduction, vibration suppression, reduction of wake fluctuations and energy harvesting.