3. Since the restricted flow through the narrow bottom clearance 

 constriction is the critical part of the lift force phenomenon, the 

 effect of pipeline roughness and bottom roughness on the wave-induced 

 lift forces should be studied. This has practical significance, since 

 the ocean floor is not necessarily smooth, and pipelines installed in 

 marine waters may soon become encrusted with marine organisms, thus 

 increasing their surface roughness. 



4. The effect on the lift force phenomenon of a horizontal bottom 

 current superimposed on the oscillatory motions of the wave action 

 should be investigated. 



5. The effect of porosity of the bottom on lift forces should also 

 be investigated. 



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