Let the actual velocity U = Uq + U^ sin 9 where Ug and U^, are constants (fig. 23). 

 Since the meter output, e, can be made linear with F, 



where 



e = K2KsU\U\ 

 /V3 = constant. 



(27) 



Figure 23. Ac + dc flow throughout one wave cycle where inertial term may be 

 neglected and drag coefficient is constant; drag force current meter. 



Now this actual output could be converted to the corresponding U for every value 

 of 9 before any filtering is done. Thus the indicated velocity, U;, would simply be 



U, 



K2K3 



± U 



\-ifU 



>0 



<0 



(28) 



The mean value Uj over one wave cycle would then be 



2tt 



11,=— f u, 



' 2-n J ' 



de = u, 



(29) 



Therefore, for this case, the correct mean velocity Uq would be found. 



Next consider the case where the inertia terra is still assumed negligible 

 when solving for L/j (when in fact it is not). The drag coefficient is still 



35 



