TR No. 22 
equation for the time varying component of the impeller angular velocity 
as a function of the time varying component of the water velocity. The 
general solution is is 
US qe Ge! 
Ge) a DA zt / 
L (18) 
0 
q/ Ct) = 
From equation (18) the theoretical response time of the current meter 
can be determined. The response time is defined, for a step function change 
in water velocity, as the time required for the change in angular velocity 
of the impeller to achieve 1 -l/e of its final value. If the step function 
change in water velocity is 
Ont. G0 
uf (t) = 
u' = constant, t > 0 (19) 
f : LE 
then the corresponding motion of the impeller is, from equation (18), 
OF tio 
/ Piel CV 
COE) Se G1 me 
=p Wes 
(20) 
From equations (10) and (11) 
F(T) 
Gy st 2p Je Z biles th tice 
Cs DATES a0 LATS ay ee 
Za Cp J, ae D) 
° G23) 
