Flow Observations and Analysis of Curved Plate ----Leading Edge Vortex Observed at Angle of Attack 2°-4°
In Figure 1, for all angles of attack, the flow separates at the leading edge of the curved plate and circulates, reattaching at the middle of the surface by which the vortex is formed.
For angle of attack 5°-7°, the vortex sheds away with time when the flow goes downward. The situations are similar to what happen over the flat plate. Figure 2 (d)-(f) in the below also infer that the vortex sheds downstream as the peaks and valleys of the curves are moving.
The leading edge vortex is observed over the curved plate at angle of attack 2°-4°, which are stably attached over the leading edge (the detailed figures will be shown in leading edge vortex analysis part). This is also illustrated in Figure (a)-(c) that the reattachment points ( wall shear stress coefficient=0) appear at approximately 10%, 22% and 40% respectively for 2°-4° and the variations are so small that could be neglected.
For angle of attack 5°-7°, the vortex sheds away with time when the flow goes downward. The situations are similar to what happen over the flat plate. Figure 2 (d)-(f) in the below also infer that the vortex sheds downstream as the peaks and valleys of the curves are moving.
The leading edge vortex is observed over the curved plate at angle of attack 2°-4°, which are stably attached over the leading edge (the detailed figures will be shown in leading edge vortex analysis part). This is also illustrated in Figure (a)-(c) that the reattachment points ( wall shear stress coefficient=0) appear at approximately 10%, 22% and 40% respectively for 2°-4° and the variations are so small that could be neglected.
Figure 2:Wall Shear Stress Coefficient against Chord in One Period for Curved Plate at Angle of Attack (a) 2° (b) 3° (c) 4° (d) 5° (e) 6° (f) 7°
It is worth noticing that the y axis ranges from -0.03 to 0.03 for angles of attack 2°-4° (Figure 2 (a)-(c)) while for 5°-7° (Figure 2 (d)-(f)), the range becomes -0.15 to 0.15. So the wall shear stress coefficients are observably low for those where the leading edge vortex occurs. The variations are almost negligible which proves that the leading edge vortex is the steady feature.