UNCLASSIFIED 



SECURITY CLASSIFICATION OF THIS PAGE(TWl«n Dmim Bntand) 



The experimental results of this investigation, however, show that this 

 steady-flow lift model is inadequate for wave-induced oscillatory flows. 

 For pipelines at small clearances above the bottom, viscous effects near 

 the bottom clearance constriction may result in lift forces acting in both 

 the upward and downward directions during different parts of the wave cycle. 

 In addition, the maximum positive and negative lift forces may not correspond 

 to the positions of maximum horizontal velocities in the wave cycle. 



A modified lift force model of the form, Fl = 1/2 Cl p A u^ax^ 

 [cos^ (e-(t>) - k] , is proposed where the parameters, Cl, 9, and k, may vary 

 accordingly to allow adequate description of all characteristics of the lift 

 force phenomenon. Quantitative relationships between these unknown lift 

 force parameters and various dimensionless parameters defining the wave and 

 pipe conditions were found. These relationships exhibited good correlation 

 for all wave conditions, bottom clearances, pipe diameters, and orientation 

 angles. 



UNCLASSIFIED 



SECURITY CLASSIFICATION OF THIS PAGEfHTion Dale Entered) 



