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This article provides a method by which the scour and self-burial of spherical bodies, short cylinders, and truncated cones that are induced by bichromatic and bidirectional waves could be derived. The empirical scour and self-burial depth formulas for spherical bodies, short cylinders, and truncated cones are used with a bed shear stress model beneath bichromatic and bidirectional waves. Examples of the results are given for unidirectional bichromatic and bidirectional monochromatic waves. The results appear to agree qualitatively with physical expectations. [ABSTRACT FROM AUTHOR]

Direct numerical simulations have been conducted to investigate a zero-pressure-gradient boundary layer flow over a single shallow dimple. Here, the dimple depth to dimple diameter ratio (d / D) as well as the Reynolds number (based on D and free-stream velocity) are fixed at 0.05 and 20 000, respectively. The effect of inlet boundary layer thickness δ on a given dimple is investigated by considering δ / D ∈ [ 0.023 , 0.1 ]. The flow within the dimple exhibits either a horseshoe vortex (a continuous core line through the two spirals within the dimple) or a tornado-like vortex pair (discontinuous core line). For the given parameter range, four different flow patterns have been identified within the single dimple: (i) a steady symmetric horseshoe vortex pattern for δ / D ∈ [ 0.053 , 0.1 ] , (ii) a steady asymmetric horseshoe vortex pattern for δ / D = 0.04 , (iii) a quasi-periodic asymmetric horseshoe vortex pattern for δ / D = 0.033 , and (iv) a mixed horseshoe and tornado-like vortex pattern for δ / D = 0.023. The growth of the streamwise vorticity, mainly caused by the tilting of the vertical vorticity, plays a key role in the transition between the different flow patterns. Dimple-induced velocity streaks above the single dimple have been investigated in detail for the first time, showing four different streaks: (i) a high-speed streak above the dimple, (ii) two side-low-speed streaks located outside the dimple span, (iii) two side-high-speed streaks, and (iv) a mid-low-speed streak in between them. These are mainly caused by a flow acceleration effect and a flow diffuser effect over the dimple, as well as a "lift-up" mechanism within the downstream part of the dimple, tilting the boundary layer upward. [ABSTRACT FROM AUTHOR]

The spectrum of seabed shear stresses at beds with large roughness beneath ocean surface waves in finite water depth is derived by using the wave friction factor for large roughness. It is expressed in terms of the transfer function between the waves at the surface and the shear stress at the bed, and the wave spectrum in finite water depth, which is obtained by multiplying the deep water wave spectrum with a depth correction factor. The seabed shear stress spectrum for laminar flow, which is of practical interest for flow over muds, is also given in order to compare with the rough turbulent case. Examples are included to illustrate the applicability of the seabed shear stress spectrum for practical purposes using data typical for field conditions, both for ver3, rough beds and mud beds. [DOI: 10.1115/1.4000501] Keywords: random waves, bottom friction, large bed roughness, stability of scour protections, laminar flow, erosion and deposition of mud

The purpose of these comments and discussion has been to demonstrate how wave statistics can be incorporated into future applications of the proposed empirical equations to estimate the maximum relative uplift pressure under positive and negative freeboards on berm revetment with Seabee slope. This is demonstrated by using a joint distribution of significant wave height and surf parameter as well as by giving examples of the results. [ABSTRACT FROM AUTHOR]

A one-dimensional model was applied to investigate the way in which local physical conditions affect the initiation of phytoplankton blooms in nutrition rich waters characterized by wind driven currents and salinity stratification in fjords and coastal waters. It was found that the onset of phytoplankton blooms depends on a nontrivial balance between the wind induced free surface stress and the strength, vertical location and thickness of the initial pycnocline, and the mean sinking velocity of the phytoplankton.