Crest of Clopotis ., . „ „, /a^k;* r^r.*^^ 



^ Mean Level (Orbit Center 



of Clopotis ) 



Incident Wove 



/////////////// 



d = Depth from Stillwater Level 



Hj = Height of Original Free Wave ( In Water of Depth, d ) 



X - Wave Reflection Coefficient 



ho = Height of Clopotis Orbit Center ( Mean Water Level at Wall ) Above 

 the Stillwater Level ( See Figures 7-90 and 7-93 ) 



Vg = Depth from Clopotis Crest = d + ho + ( ^4^ ) Hj 



Vl = Depth from Clopotis Trough = d + ho - (-'^^ ) Hj 



b - Height of Wall 



Figure 7-88. Definition of Terms: nonbreaking wave forces. 



The reflection coefficient, and consequently clapotis height and wave force, 

 depends on the geometry and roughness of the reflecting wall and possibly on 

 wave steepness and the "wave height-to-water depth" ratio. Domzig (1955) and 

 Greslou and Mahe (1954) have shown that the reflection coefficient decreases 

 with both increasing wave steepness and "wave height-to-water depth" ratio. 

 Goda and Abe (1968) indicate that for reflection from smooth vertical walls 

 this effect may be due to measurement techniques and could be only an apparent 

 effect. Until additional research is available, it should be assumed that 

 smooth vertical walls completely reflect incident waves and x = \ . Where 

 wales, tiebacks, or other structural elements increase the surface roughness 

 of the wall by retarding vertical motion of the water, a lower value of x 

 may be used. A lower value of x also may be assumed when the wall is built 

 on a rubble base or when rubble has been placed seaward of the structure 

 toe. Any value of x l&ss than 0.9 should not he used for design purposes. 



Pressure distributions of the crest and trough of a clapotis at a vertical 

 wall are shown in Figure 7-89. When the crest is at the wall, pressure 



7-162 



