(a) 



LA 



WAVE 

 PROFILE 



PIPELINE ON 

 BOTTOM 



(b) 



L i 

 



/ 



"X 



/ 



N 



-y 



\ 



s^ 



\ 



SMALL 

 CLEARANCE 



(C) 



•^L ♦ 

 d) 



L 1 

 



i 



^N, 





^^. 



W 



\ 



V/ 



\ 



INCREASING 

 CLEARANCE 



NO CHOKING 

 EFFECT 



(e) 



L I 

 



I 















^ 



LARGER 

 CLEARANCE 



Figure 4. Change in lift force record for increasing bottom clearance, 



27 



