A, fig. 192, ntd_o cosec [phi]
B, fig. 192, ntd cosec [phi] (15)
C, fig. 192, nt(r2 - r1) cosec [phi].
Call this area occupied by the vanes [omega]. Then the true value of
the clear discharging outlet of the wheel is [Omega]_o - [omega], and
the true value of u_o is Q/([Omega]_o - [omega]). The corrected value
of the angle of the vanes will be
[phi] = tan [Q/V_o ([Omega]_o - [omega]) ]. (16)
§ 193. _Head producing Velocity with which the Water enters the
Wheel._--Consider the variation of pressure in a wheel passage, which
satisfies the condition that the sections change so gradually that
there is no loss of head in shock. When the flow is in a horizontal
plane, there is no work done by gravity on the water passing through
the wheel. In the case of an axial flow turbine, in which the flow is
vertical, the fall d between the inlet and outlet surfaces should be
taken into account.