FIGURE 7 The influence of three parameters on aerodynamic
performance of the TWA model. The designed parameters include: the
number of corrugations, the
corrugation
angles, and the
flapping
frequency. (a) When the number of corrugations is 3, Three models of
different corrugation angles are designed. These models are named acute
angle
airfoil
(AAA-3),
right angle
airfoil
(RAA-3) and obtuse angle airfoil (OAA-3), respectively. (b)
Thel and (c) \(\overset{\overline{}}{C_{l}/C_{d}}\)diagram affected by three parameters. (d) The velocity contour diagram
of TWA model during upstroke and downstroke with too many corrugations.
To get the optimal parameters of
TWA model, multiple linear regression analysis was used. Because the
change of l and\(\overset{\overline{}}{C_{l}/C_{d}}\) are positively correlating, the
following analysis and calculations are only forCl . The details are shown in Table 3-5. The
multiple linear regression analysis was performed on the 3 parameters
mentioned above: number of corrugations, the flapping frequency, and the
corrugation angle. We set the number of corrugations =8; flapping
frequency =75 Hz and the corrugation angle = obtuse angle (135°) as
benchmark, the benchmark value set as constant value =0. In other word,
if other parameter data is great than benchmark data, this indicates
that this value is better.
The results showed that a number of corrugations of 5, a right
corrugation angle and the flapping frequency of 75 Hz to be optimal
(Table 4). In Table 5, the variance analysis result is shown. At a
significance level of 0.05, the Cl has a strong
correlation with the number of corrugations as well as with the
corrugation angle and flapping frequency. From Table 6, the results of
the regression coefficient were shown.
Based on the test results, if the Cl is assumed
to be defined as y, the number of corrugations, the corrugation angle
and the flapping frequency
defined
as x1 , x2 andx3 respectively, the approximate linear
regression equation can be obtained by SPSS software package. The
regression equation can be expressed as
\begin{equation}
y=0.210-0.002x_{1}-0.038x_{2}+0.022x_{3}\nonumber \\
\end{equation}Where the value of x1 is 1-8, the value ofx2 is 1-3 (which represents acute angle, right
angle and obtuse angle, respectively), and the value ofx3 is 1-3 (which represent 55 Hz, 65 Hz and 75
Hz, respectively).
Table 4 Parameter Estimates