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Ocean Systems Engineering
  Volume 7, Number 3, September 2017 , pages 275-298
DOI: https://doi.org/10.12989/ose.2017.7.3.275
 

Scour below pipelines due to random waves alone and random waves plus currents on mild slopes
Dag Myrhaug, Ping Fu and Muk Chen Ong

 
Abstract
    This paper provides a practical stochastic method by which the maximum equilibrium scour depth below a pipeline exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Freds e (1996). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases for random waves alone are also suggested.
 
Key Words
    scour depth; pipeline; mild slope; random waves; current; stochastic method
 
Address
Dag Myrhaug and Ping Fu: Department of Marine Technology, Norwegian University of Science and Technology
Trondheim, Norway
Muk Chen Ong: Department of Mechanical and Structural Engineering and Material Science, University of Stavanger
Stavanger, Norway

 

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