• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.405-414
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• 2010

In the study, experiments are performed in the mixing region combined wave and current to investigate the characteristics of local scour around a slender pile. Wave generator and current generator are used for the experiments and currents are co-directions with the waves. The local scour depths around the pipeline are obtained according to the various pipe diameters, wave periods, wave heights, and current velocities. The experiments show that the maximum equilibrium local scour depth increases with pipe diameter, wave period, wave height, and current velocity. Using the experimental results, the correlations of scour depth and parameters such as Shields parameter ($\theta$), Froude number (Fr), Keulegan-Carpenter number (KC), Ursell number ($U_R$), modified Ursell number ($U_{RP}$) and ratio of velocities ($U_c/U_c+U_m$) are analyzed. In the mixing region combined with waves and currents, The Froude number of single parameters is the main parameter to cause the local scour around a slender pile due to waves and current and this means that current governs the scour within any limits of the currents.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.5
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• pp.510-521
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• 2008

In the study, experiments are performed in the interaction region combined with wave and current to investigate the characteristics of local scour around submarine pipelines. Wave generator and current generator are used for the experiments and two current directions were used; co-direction and counter direction to the wave. The local scour depths around the pipeline are obtained according to the various pipe diameters(D), wave periods(T), wave heights(H), and current velocities(V). The experiments show that the maximum equilibrium local scour depth increases with pipe diameter, wave period, wave height, and current velocity. Using the experimental results, the correlations of scour depth and parameters such as Shields parameter($\theta$), Froude number(Fr), period parameter, Keulegan-Carpenter number(KC), Ursell number($U_R$), modified Ursell number($U_{RP}$) and ratio of velocities($U_{c}/(U_{c}+U_{m})$) are analyzed. In the interaction region combined with waves and currents, Froude number and Shields parameter are found the main parameters to cause the local scour around the submarine pipelines and this means that current governs the scour within any limits of the currents.

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.61-67
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• 2018

Scour protection methods can be categorized as two types: The first is to reduce the horseshoe and wake vortices which are the main reasons for local scour. Either small cylindrical structures or separated vertical deflectors can be placed in front of the pier or the horizontal deflector (or collar) can be attached to the pier like the spoiler to reduce the dynamics of vortical structures. The second is to employ the protection layer to keep the bed material in place, which is a common method with a merit of immediate effect by using block mat or tetrapod. This study examined the effect of scour reduction using the former method. The relationship between the reflector interval and reduction of scour was not clear. It is assumed that the width of the reflector is somewhat correlated with the reduction of the scour. As the KC numbers increases, the Effect of Scour reduction rate is shown to decrease. Also, Scour reduction rate showed a rapid change at $U_R=25$ or KC = 8.