The Equivalent Depth of Wave-Induced Scour Around Offshore Pipelines

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Mir Emad Mousavi ◽  
Abbas Yeganeh Bakhtiary ◽  
Nastaran Enshaei
Keyword(s):  
Deep Water ◽  
Wave Motion ◽  
Scour Depth ◽  
Offshore Pipelines ◽  
Equivalent Depth ◽  
Physical Experiments ◽  
Water Conditions ◽  
Installation Depth ◽  
New Equation ◽  
Wave Induced

Physical experiments have been conducted to study the scouring around a pipe over an erodible bed under wave motion. The results show that the depth of the wave-induced scour is reduced when the pipe is installed in a primary depth. It is also indicated that when the primary installation depth of the pipe, |e|, exceeds a specified depth, no scouring occurs underneath the pipe. This specific depth is called the equivalent depth of wave-induced scour, Se. The equivalent depth of wave-induced scour is estimated as a function of pipe diameter and the Keulegan–Carpenter number. With respect to the primary installation depth of the pipe, a new equation is suggested to predict the scour depth before installation of the pipe. And the scour width is predicted in two other new equations. The proposed equations are then simplified in the form of diagrams. The experiments cover small KC numbers (KC<6) that represent deep water conditions.

The Equivalent Depth of Wave-Induced Scour Around Offshore Pipelines

2006 ◽  
Author(s):  
Mir Emad Mousavi ◽  
Abbas Yeganeh Bakhtiary ◽  
Nastaran Enshaei
Keyword(s):  
Deep Water ◽  
Numerical Models ◽  
Scour Depth ◽  
Offshore Pipelines ◽  
Equivalent Depth ◽  
Physical Experiments ◽  
Water Conditions ◽  
Installation Depth ◽  
New Equation ◽  
Wave Induced

Physical experiments have been conducted to study the scouring around a pipe over an erodible bed under waves motion. The results show that the depth of the wave-induced scour is reduced when the pipe is installed in a primary depth. It is also indicated that when the primary installation depth of the pipe, |e|, exceeds a specified depth, no scouring occurs underneath the pipe. This specific depth is called the Equivalent Depth of Wave-Induced scour, Se. The equivalent depth of wave-induced scour is estimated as a function of pipe diameter and the Keulegan Carpenter number. Also for prediction of the scour depth with respect to the primary installation depth of the pipe, a new equation is proposed. In addition, new equations are proposed for prediction of the scour width before the pipe is installed. The results and proposed equations are next simplified in the form of diagrams to be used in practice. The experiments cover small KC numbers (KC < 6) that represent deep water conditions. The results can be used either for the design purposes or for calibration of the numerical models.

Time Scale of Scouring Around Submarine Pipelines Induced by Wave and Current

2006 ◽  
Author(s):  
Abbas Yeganeh Bakhtiary ◽  
Mir Emad Mousavi ◽  
Amin Tohidi Vahdat
Keyword(s):  
Time Scale ◽  
Total Duration ◽  
Experimental Results ◽  
Scour Depth ◽  
Duration Time ◽  
Physical Experiments ◽  
New Equation

Physical experiments have been conducted to explore the time scale of the wave- and current- induced local scouring around submarine pipelines as well as the development of the scour profile versus the elapsing time. The experimental results have been used to examine the recommended equations of Fredsoe et al. (1992) and/or to derive new equations for prediction of scour depth/width during the process with respect to the equilibrium scour properties. In addition, the total duration (time scale) of scouring is studied and a new equation is proposed for the case of current motion. The results of this equation are then simplified in the form of diagrams for estimation of the scouring duration in practice.

Variability in surface and deep water conditions in the nordic seas during the last interglacial period

1998 ◽  
Vol 17 (9-10) ◽  
pp. 963-985 ◽  
Author(s):  
Torben Fronval ◽  
Eystein Jansen ◽  
Haflidi Haflidason ◽  
Hans Petter Sejrup
Keyword(s):  
Deep Water ◽  
Interglacial Period ◽  
Last Interglacial ◽  
Nordic Seas ◽  
Last Interglacial Period ◽  
Water Conditions

Wave action on currents with vorticity

1999 ◽  
Vol 386 ◽  
pp. 329-344 ◽  
Author(s):  
BENJAMIN S. WHITE
Keyword(s):  
Phase Shift ◽  
Deep Water ◽  
Current Velocity ◽  
Wave Action ◽  
Ray Theory ◽  
Wkb Method ◽  
Interaction Of Waves ◽  
New Equation ◽  
Spatially Varying

The interaction of waves on deep water with spatially varying currents may be described by a ray theory, with the wave amplitudes determined by the principle of conservation of wave action (CWA). However, all previous deep water derivations of CWA are restricted to the case of an irrotational current. In this paper, both the ray theory and CWA are derived by a WKB method without the assumption of irrotationality. Also derived is a new equation for a spatially varying phase shift which is not predicted by the usual ray theory, and which, in general, displaces the positions of the wave crests by a distance on the order of a wavelength. This phase shift, which is caused by variations of the current velocity with depth, vanishes in the irrotational case, and so is in accord with the irrotational theory.

Two-Dimensional Model for Wave-Induced Pore Pressure Accumulation in Marine Sediments

2013 ◽  
Author(s):  
Hongyi Zhao ◽  
Dong-Sheng Jeng ◽  
Huijie Zhang ◽  
Jisheng Zhang
Keyword(s):  
Pore Pressure ◽  
Marine Sediments ◽  
Wave Motion ◽  
Present Model ◽  
Two Dimensional ◽  
New Model ◽  
One Dimensional ◽  
Wave Cycle ◽  
Previous Solution ◽  
Wave Induced

In this paper, a two-dimensional (2D) porous model is established to investigate the predication of the wave-induced pore pressure accumulations in marine sediments. In the new model, the VARANS equation is used as the governing equation for the wave motion, while the Biot’s consolidation theory is used for porous seabed. The present model is verified with the previous experimental data [1] and provides a better prediction of pore pressure accumulation than the previous solution [2]. With the new model, a 2D liquefied zone is formed at the beginning of the process, and then gradually move down. After a certain wave cycle (for example, 30 wave cycles in the numerical example), the liquefaction zone will become one-dimensional (1D) and continuously move down and eventually approaches to a constant. Numerical results also conclude the maximum liquefaction depth increases as wave height increases and in shallow water.

Local scour of cohesive beds downstream of a rigid apron

2017 ◽  
Vol 44 (11) ◽  
pp. 935-944 ◽  
Author(s):  
Hossein Hamidifar ◽  
Mohammad Hossein Omid
Keyword(s):  
Grain Size ◽  
Empirical Equation ◽  
Scour Depth ◽  
Removal Mechanism ◽  
Sediment Grain Size ◽  
Scour Hole ◽  
Hole Profile ◽  
The Mean ◽  
New Equation ◽  
Individual Particles

In this paper, the physics of scour hole in a mixed sand–clay bed downstream of an apron is studied experimentally. Seven combinations of sand–clay mixtures including clay contents, Cc, ranging from 0 to 0.4 were used. The results show that Cc = 0.4 can reduce the maximum scour depth, εm, up to about 80% for all the densimetric Froude numbers in the range of the present study. An empirical equation has been proposed for calculation of εm in sand–clay mixtures with the mean error of 0.12. The removal mechanism of sediments from the bed was different based on the Cc. For low clay contents, i.e., Cc ≤ 15%, individual particles were detached from the bed. At higher Cc, clusters of particles were separated and moved downstream with the flow. A new equation has been proposed to predict the dimensionless scour hole profile in mixed sand–clay sediments. Dimensionless graphs have been presented for incorporating the effect of tailwater depth and sediment grain size on the main characteristics lengths in sand–clay mixtures.

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