Pq = atmospheric pressure outside of pneumatic chamber, 

 lb/ft2 



U2 = wave particle velocity at nozzle mouth, ft/s 



V = wave velocity, £t/s 



f^air^ = initial volume of air in pneumatic chamber per foot of 

 ° chamber length = Jl(hT - hw) x 1.0, ft^ 



Y = ratio of specific heats, for air y = 1.40 



Ap = suction pressure in pneumatic chamber during the subse- 

 quent wave motion, Ib/ft^ 



Apj^ = suction pressure in pneumatic chamber at the beginning 

 of wave motion, poundals/ft^ 



Apo = initial suction pressure in pneumatic chamber to 



raise water to height h,^, Ib/ft^ (^Po ^^ ^ posi- 

 tive quantity) 



6 = fall of water surface in pneumatic chamber, ft 

 p = density of water, lb/ft ^ 



Application of the above equations to the design of a pneumatic gen- 

 erator for use in a three-dimensional tsunami model of Hilo Bay, Hawaii, 

 is discussed by Keulegan (1966). The generator actually used in the Hilo 

 Bay model study is described by Palmer, Mulvihill, and Funasaki (1967). 

 The use of equations (6-25) to (6-37) in the design of the pneumatic gen- 

 erator for a two-dimensional, wave flume study concerning the stability 

 of a proposed rubble-mound tsunami barrier for the protection of Hilo 

 Harbor (with details on the use and calibration of the generator and 

 wave flume) is presented by Kamel (1967). 



c. Construction of Model Structures . 



(1) Rubble-Mound Structures . Rubble-mound breakwaters, jetties, 

 seawalls, and wave absorbers in nature are usually constructed with a 

 core material consisting of quarry- run stones, two outer layers of se- 

 lected armor stones and enough intermediate underlayers to provide pro- 

 tection to the core material, and good bedding for the armor stones. The 

 armor stones are of sufficient weight to withstand the forces of the se- 

 lected design wave, the first underlayer stones are^ slightly larger than 

 that required to prevent leaching of the underlayer material through the 

 voids in the armor stones (usually about one-tenth the weight of the 

 armor stones) , and the quarry- run core material is composed of that part 

 of the blasted rock not used in the underlayers or for armor stones. 

 Quarry- run stones usually vary from 10 pounds or less to about 4 tons, 

 depending on the type of rock, method of blasting, and the design wave 



355 



