u, 



The indicated values of U; were lower than the correct value Uq, and quite sizable 

 errors resulted. The values through the wave cycle for the case where Uq/U = 0.2 

 are plotted in figure 24. 



Other shapes can be used instead of cylinders; however, the same type 

 of problem still exists. The inertial term cannot be neglected for flat plates except 

 at very small values of period parameter. ^^ Adding to this is that quite large changes 

 in Cj^ and C^ throughout the wave cycle exist for all values of period parameter. 

 Although spheres were not studied, ^^ the results would probably be similar to those 

 with cylinders. 



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 



t/T 



Figure 24. Drag force meter example. 



ADVANTAGES 



The good features of the drag force meter from a hydrodynamic standpoint 

 are as follows: 



1. The meter is small and has few moving parts. 



2. The directional response can be made a cosine function. 



3. The output will indicate both the magnitude and direction of a given 

 velocity component. 



37 



