138 



ops comparatively large corrections to the velocit}^, the computations 

 should be repeated with the corrected velocities derived from the first 

 computation. 



277. The relatively small distortions of the tides needed to prociiice 

 a large distortion of the surface head and currents is illustrated in 

 figure 44. The current there shown has the equation: 



?;=sin m2i+sin 3m2^ 



Neglecting the velocity head, the equation of motion becomes: 

 d2//dx+(m2/fif)(cos m2t-\-3 cos 3m20±(sin mg^ + sin dm2ty/C^r=0 



Whence: 



h,= {ldy/bx) 

 = — {Ivci-ilg) (cos m2^ + 3 cos 3m20 ± {IjCh) (sin m2/+sin 3m20^- 



O 



-2 



^ 0.2 

 S O 



HEAD 



Lunar Hour 



Tide at initial end 



at other end 



Figure 41.— Comparative di&tortions of current and tides. 



The surface head, hs, in a section 10,000 feet long, when r=20 

 and C=90, is plotted in the figure. Taking the tide at the initial end 

 of the section as a simple harmonic fluctuation with an amplitude of 



