Test Case 5
This test case is for the same airfoil of the previous test case subject, this time to a ramp-type
harmonic motion. The boundary-layer calculations employing quasi-steady and unsteady flow
assumptions are performed for constant pitch rates A of 0.0001 (Fig. 10.13a), 0.01 (Fig. 10.13b),
0.05 (Fig. 10.13c), and 0.1 (Fig. 10.13d) at a chord Reynolds number Rc of 6  106 with 1  5 ,
   12 and  T S  30 . The results indicate that at the lowest pitch rate, viscous effects have a
strong effect with significant differences from those computed with the panel method. While at
low to modest angles of attack, there is practically no difference between the lift coefficients
computed with quassi-steady or full unsteady flow assumptions, at higher angles there is a
difference; the quasi-steady flow assumption shows a stronger viscous effect.
As the pitch rate increases the differences between the inviscid and viscous lift coefficients
become less, with quassi-steady flow assumption again indicating a stronger viscous effect.
Figure 10.13. Variation of lift coefficient cl for ramp-type harmonic motion for constant pitch
rates of A (a) 0.0001 (b) 0.01 (c) 0.05 and (d) 0.1
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