Flow Observations and Analysis of Flat Plate----no Leading Edge Vortex
In Figure 1, for all angles of attack, the flow separates at the leading edge and reattaches in the middle of the aerofoil surface. The flow moves backward in the region between the separation and reattachment and forms the vortex. This vortex then sheds downstream, after which the new one is formed on the leading edge. The flow shows the similar characteristics for the flat plate at all angles of attack. At the angle of attack 2 degrees, the flow reattaches at 82% of the chord length (see Figure 3). This can be considered as that the vortex exists over the plate surface from the leading edge to 82% of the chord length.
The vortex shedding can also be inferred from Figure 2.where the positions of separation and reattachment (the points where =0) are shown randomly. Generally, the peaks and valleys of the curves are convecting to the downstream, which corresponds to the observations of vortex shedding in velocity vector scenes. |
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