Forces Exerted by Waves on a Pipeline at or Near the Ocean Bottom
CALIFORNIA UNIV BERKELEY HYDRAULIC ENGINEERING LAB
Pagination or Media Count:
The Wave-induced forces on a submarine pipeline near the ocean floor consist of several components--inertial forces, drag forces, lift forces, and under some conditions, eddy-induced forces. For a pipeline touching the bottom, or at a small clearance above the bottom, the lift force is the predominant force in the vertical direction. This force is generally expressed as F sub L 12 C sub L RHO A USQ and is added as a lift term to the Morison equation. 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 life forces may not correspond to the positions of maximum horizontal velocities in the wave cycle. A modified lift force model of the form, F sub L 12 C sub L RHO A u sub max sq COs sq theta-phi - k, is proposed where the parameters, C sub l, Ph1 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.
- Physical and Dynamic Oceanography
- Pumps, Filters, Pipes, Tubing, Fittings and Valves