Investigation of vortex development on accelerating spanwise-flexible wings

Circulation Redistribution in Leading-Edge Vortices with Spanwise Flow

“…Both the spanwise advection of vorticity and the annihilation of vorticity are critical circulation-regulating mechanisms [9,16]. The spanwise advection of vorticity is especially difficult to account for because most models for LEV growth are explicitly two-dimensional, such as the strip-theory approaches [17].…”

Understanding and controlling vorticity transport in unsteady, separated flows

“…However, the results also showed the total circulation of the control region was substantially reduced by the vorticity diffusing from the surface beneath the LEV, which is in accordance with the limited number of studies available in which the diffusive flux was properly characterized[32,1,96,85]. Demonstrating the relevance of this source has served to identify a major deficit within our understanding of leading-edge vortex formation on unsteady profiles, as many examples within the literature overlook the effects of the diffusive flux of vorticity from the surface of the airfoil[59,25,50,120]. Cursory attempts-to great effect-have been made to correct this oversight by relating the major trends within the diffusive flux to the evolution of the LEV.…”

“…This conclusion highlights a major deficit within our understanding of unsteady airfoils and their interaction with vortex dominated flows, as it provides evidence that the critical dynamics for stabilizing an LEV are associated with a term from the Navier-Stoke equation (i.e. viscous diffusion) that is almost always neglected within experimental studies [59,25,50,120].…”

“…However, Figure 5.4 shows that the magnitude of the diffusive flux is approximately half that of the shear-layer flux. The importance of this result is accentuated by the fact that the majority of existing studies tend to neglect the effects of vorticity diffusing from the surface [59,25,50,120]. This trend is particularly surprising given that the few studies which have characterized the diffusive flux properly have shown it to take a prominent role in the development of a vortex.…”

The effect of dynamic twisting on the flow field and the unsteady forces of a heaving flat plate

“…Several researchers have shown that the lift response improves due to flexibility during such LEV formation. This improvement was attributed to the increased stability of LEV [27,28]. Kim and Gharib showed that a flexible plate oriented at a 90 • angle of attack experienced a lower initial peak force, although later, the same plate generated higher forces compared to a rigid plate due to slower development of vortices [29].…”