Kinematics and Shear Stresses from Combined Waves and Longshore Currents in the UK Coastal Research Facility

Simons, Richard R.; MacIver, Ruairi D.; Saleh, Wameidh M.

doi:10.1061/9780784402429.269

Cited by 5 publications

(6 citation statements)

References 8 publications

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“…In order to simulate an oscillatory motion orthogonal to a current, [ Sleath , 1990] used an oscillating plate in a flume and found that, over a smooth bed, the oscillations of the plate have an insignificant effect on the current velocity profiles. Simons et al [1992, 1994, 1996] carried out a series of experiments to study the wave‐current interaction over a rough bed; they found that the wave presence induces a significant reduction of the mean velocity in the upper part of the flow coupled, in most cases, with an increase close to the bottom. This effect is more pronounced for waves with long periods and large heights.…”

Section: Introductionmentioning

confidence: 99%

Waves plus currents crossing at a right angle: Experimental investigation

et al. 2006

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[1] The hydrodynamics generated by a regular wave field perpendicularly superimposed to a steady current is investigated by means of laboratory experiments. The flow structure is analyzed by measuring the velocity profiles using a micro Acoustic Doppler Velocimeter. Three cases are considered: current only, waves only and waves plus current. Different bottom roughnesses are used, and the apparent roughness k s is estimated for each condition. In the presence of a small roughness, the superposition of the waves on the current causes an increase of the current velocities close to the bottom, thus generating a decrease of the apparent roughness with respect to the case of the current only. On the other hand, when a large bottom roughness is present, the waves force a decrease of the current velocity close to the bottom and, in turn, an increase of the apparent bottom roughness. Such a behavior seems related not only to the roughness but also to the flow regime (i.e., laminar or turbulent) within the wave bottom boundary layer.

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Section: Introductionmentioning

confidence: 99%

Waves plus currents crossing at a right angle: Experimental investigation

et al. 2006

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“…Sleath [1990] through an oscillating plate inside a flume, observed negligible effects of the plate oscillation on the velocity profiles. Simons and coworkers [Simons et al, 1992[Simons et al, , 1994[Simons et al, , 1996, studying the wavecurrent interaction over a rough bed, found that waves, especially when they are characterized by long periods and large heights, induce a significant reduction of the mean velocity in the upper part of the flow often coupled with an increase close to the bottom. Arnskov et al [1993] performed bed shear stress measurements in a wave plus current environment over a smooth boundary and found no significant nonlinear enhancement of the maximum shear stress in the presence of the current.…”

Section: Introductionmentioning

confidence: 99%

Waves plus currents at a right angle: The rippled bed case

2008

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[1] The present paper deals with wave plus current flow over a fixed rippled bed. More precisely, modifications of the current profiles due to the superimposition of orthogonal cylindrical waves have been investigated experimentally. Since the experimental setup permitted only the wave dominated regime to be investigated (i.e., the regime where orbital velocity is larger than current velocity), also a numerical k-e turbulence closure model has been developed in order to study a wider range of parameters, thus including the current dominated regime (i.e., where current velocity is larger than wave orbital one). In both cases a different response with respect to the flat bed case has been found. Indeed, in the flat bed case laminar wave boundary layers in a wave dominated regime induce a decrease in bottom shear stresses, while the presence of a rippled bed behaves as a macroroughness, which causes the wave boundary layer to become turbulent and therefore the current velocity near the bottom to be smaller than the one in the case of current only, with a consequent increase in the current bottom roughness.

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“…On the other hand, many efforts have been carried out by the scientific community with the purpose of analyzing wave-current non linear interactions in the simplest case of an unvegetated bottom. Laboratory experiments [Kemp and Simons (1982), Kemp and Simons (1983), Visser (1986), Klopman (1994), Klopman (1997), Umeyama (2005); Musumeci et al (2006); Simons et al (1996) among others] showed that when waves and currents coexist, the steady profile of longitudinal velocity changes the logarithmic shape observed for pure current conditions. In particular, Kemp and Simons (1982) showed that mean longitudinal velocities close to a smooth bed increase in the presence of waves, whereas they reduce near a rough bed.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of the impact of macroalgal mats on the wave and current dynamics

Tambroni

Silva

Duck

et al. 2016

Advances in Water Resources

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Macroalgal mats of Ulva intestinalis are becoming increasingly common in many coastal and estuarine intertidal habitats, thus it is important to determine whether they increase flow resistance, promote bed stability and therefore reduce the risk of erosion favoring tidal flooding or degradation of coastal lagoons. Venier et al. (2012) [6] studied the impact of macroalgal mats of Ulva intestinalis on flow dynamics and sediment stability for uniform flow. Here we extend their experimental work to the case of vegetation under the combined action of waves and currents. These hydrodynamic conditions are very common in many shallow coastal environments and lagoons. The experimental facility employed in the present study and the series of flow runs are the same as that used by Venier et al. (2012)[6]. However, waves have been superposed to uniform current flowing firstly over a mobile sediment bed covered with U. intestinalis, then over a bare sediment surface. For the depth, wave and current conditions considered in the experiments, the time-averaged vertical profile of horizontal velocity for the case of coexisting waves and current turns out to be very close to that observed for a pure current, both with and without vegetation. However, contrary to what was observed in the case of a unidirectional current, in the presence of waves the time averaged velocity profile is only weakly influenced by the vegetation, whose main effect is to attenuate velocity oscillations induced by waves and to slightly increase the overall bed roughness

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Kinematics and Shear Stresses from Combined Waves and Longshore Currents in the UK Coastal Research Facility

Cited by 5 publications

References 8 publications

Waves plus currents crossing at a right angle: Experimental investigation

Waves plus currents crossing at a right angle: Experimental investigation

Waves plus currents at a right angle: The rippled bed case

Experimental investigation of the impact of macroalgal mats on the wave and current dynamics

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