sin αst

And
ROTOR THEORY
In the above F refers to a correction factor that takes into account tip losses, according to
Prandtl’s theory. Tip losses occur when air flows around the tip from the lower to upper
surface due to pressure difference.
Cx and Cy are the components of the lift and drag coefficients:
�’ in (B.3) and (B.4) is the solidity ratio, defined as
In case a of (B.3) becomes greater than ac = 0.2 it is no longer valid and the axial interfer-
ence factor is then recalculated by
Where
�
a' =
a =
(B.3)
(B.4)
(B.5)
(B.6)
(B.7)
(B.8)
(B.9)
(B.10)
Combining the above geometric and aerodynamic relations with element theory, it is pos-
sible to calculate the differential axial force and torque acting on a blade element. Using
this theory, the following assumptions are made:
F
1
4F sin ( �)
2
�' C y
1
� 1
4F sin ( �)
cos( �)
�' C x
�
� B R�r �
2 � �
2 r sin( �)
= acos e
�
�
�
� 1
�
��
��
�
Cx = Cl sin ( �)
� Cd cos( �)
Cy = Cl cos( �)
� Cd sin ( �)
�'
c B
=
2� r
1
a
2 2 K 1 2a = � � � � c�
� �� K 1 � 2ac K =
� � � 2
4F sin ( �)
2
�' C y
� �
�� 2
2
� 4 K ac � 1
�
�
133