in the foot-pound-second system of units, or 



h l/6 

 h n 



(334) 



in the meter-kilogram-second system of units, and n is Manning's rough- 

 ness coefficient. 



Substituting equations (330) , (332) , and (334) into equation (329) 

 for metric units and collecting terms 



F = - pgh 2 + 

 2 



mr * '] - 2h 



(335) 



It must be remembered that many approximations have been used in this 

 solution. 



The coefficient Cp accounts for both inertial forces and drag 

 forces. It may be noted that when 6=0, and the velocity remains con- 

 stant, the force F is simply the hydrostatic force plus a drag force 

 (per meter width) where Cp = 2. 



************** EXAMPLE PROBLEM 23************* 



GIVEN : A surge with a maximum height of 2.5 meters impacts normally 

 against the vertical side of a building. The Manning roughness 

 coefficient, n = 0.1, and it is assumed that the surge velocity, 

 u = 2/gh~, remains relatively constant and that the surge profile 

 remains constant. 



FIND : The surge force per meter of building width as a function of 

 surge height . 



SOLUTION : The surge velocity is determined from the maximum surge 

 height," so that 



u = 2v / gh = 2/9.81(2.5) =9.9 meters per second 

 The surge force is given by equation (335) as 



F = - pgh 2 + 

 2 



.2\1.2 



pu 2 h 



- I [1,026) (9.81)1,2 * |( 4(9.81H0.1)2y - 2 ♦ l] 1,026(9.9)2 h 



h2 * w * : ] ioo - 56 ° h 



F = 5,033 



176 



