A note on turbulence calculations in the wave boundary layer

Justesen, Peter

doi:10.1080/00221689109498985

Cited by 45 publications

(22 citation statements)

References 9 publications

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“…The measured profiles are calculated from the two available measured fluctuating components according to k = 0.65 u ′ 2 + v ′ 2 (Justesen, 1991). While not perfect, the computed profiles are generally consistent with the experimental data and are particularly accurate during the acceleration stage.…”

Section: Rough-turbulent Wave Boundary Layermentioning

confidence: 93%

Numerical simulation of tsunami-scale wave boundary layers

Williams

Fuhrman

2016

Coastal Engineering

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This paper presents a numerical study of the boundary layer flow and properties induced by tsunami-scale waves. For this purpose, an existing onedimensional vertical (1DV) boundary layer model, based on the horizontal component of the incompressible Reynolds-averaged Navier-Stokes (RANS) equations, is newly extended to incorporate a transitional variant of the standard two-equation k-ω turbulence closure. The developed numerical model is successfully validated against recent experimental measurements involving transient solitary wave boundary layers as well as for oscillatory flows, collectively demonstrating the ability to reproduce accurate velocity profiles, turbulence, and bed shear stresses on both smooth and rough beds. The validated model is then employed for the study of transient wave boundary layers at full tsunami scales, covering a wide and realistic geophysical range in terms of the flow duration, bottom roughness, and associated Reynolds numbers. For this purpose, three different "synthetic" (idealised) tsunami wave descriptions are considered i.e. invoking: (1) single wave (solitary-like, but with independent period and wave height), (2) sinusoidal, and (3) N-wave descriptions. The flow, boundary layer thickness, turbulence, and bed shear stresses induced are systematically monitored and parameterised, under both hydraulically smooth and rough bed conditions. The results generally support a notion that the boundary layers induced by * Corresponding author Email addresses: i.a.williams@utwente.nl (Isaac A. Williams ), drf@mek.dtu.dk (David R. Fuhrman ) Preprint submitted to Coastal EngineeringDecember 28, 2015 tsunami-scale waves are both current-like, due to their long durations, but also wave-like in the sense that the boundary layer will not necessarily span the entirety of the water column. The results likewise suggest that there is a continuum connecting wind-wave and tsunami-wave scales, as existing expressions commonly used for characterising boundary layer properties beneath wind waves maintain reasonable accuracy when extrapolated to full tsunami scales. Boundary layers driven by actual field-measured tsunami signals are likewise simulated, stemming from both the 2004 Indian Ocean as well as the 2011 Tohoku events. These results are reconciled with the various synthetic tsunami signals considered, generally confirming their usefulness as idealised tsunami waves.

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Section: Rough-turbulent Wave Boundary Layermentioning

confidence: 93%

Numerical simulation of tsunami-scale wave boundary layers

Williams

Fuhrman

2016

Coastal Engineering

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“…3 compares TKE profiles at four phases of the wave cycle for the k, k -, and k -models to the data for Test 13. TKE was estimated from laboratory measurements as 0.65 times the sum of the mean square velocity fluctuations in the flow-parallel and flow-normal directions (Justesen 1991). It is clear from the simulations that the k -model has difficulty reproducing the measured TKE near the bed regardless of the phase of the free surface flow.…”

Section: Shear Stressmentioning

confidence: 99%

One-Dimensional Wave Bottom Boundary Layer Model Comparison: Specific Eddy Viscosity and Turbulence Closure Models

Puleo

Mouraenko

Hanes

2004

J. Waterway, Port, Coastal, Ocean Eng.

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Six one-dimensional-vertical wave bottom boundary layer models are analyzed based on different methods for estimating the turbulent eddy viscosity: Laminar, linear, parabolic, k-one equation turbulence closure, k --two equation turbulence closure, and k --two equation turbulence closure. Resultant velocity profiles, bed shear stresses, and turbulent kinetic energy are compared to laboratory data of oscillatory flow over smooth and rough beds. Bed shear stress estimates for the smooth bed case were most closely predicted by the k -model. Normalized errors between model predictions and measurements of velocity profiles over the entire computational domain collected at 15°intervals for one-half a wave cycle show that overall the linear model was most accurate. The least accurate were the laminar and k -models. Normalized errors between model predictions and turbulence kinetic energy profiles showed that the k -model was most accurate. Based on these findings, when the smallest overall velocity profile prediction error is required, the processing requirements and error analysis suggest that the linear eddy viscosity model is adequate. However, if accurate estimates of bed shear stress and TKE are required then, of the models tested, the k -model should be used.

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“…While experimentalists have analyzed wave boundary layers over immobile beds (e.g., Jensen et al 1989;Justesen 1991) and over mobile sand beds (e.g., Arnott and Southard 1990), to our knowledge we present the first experimental study to produce turbulent wave boundary layers over a fine-grained sediment bed where large concentrations (Ͼ10 g/l) of sediment were suspended. In this paper we focus on (1) what wave conditions produce HDS, (2) what parameters set the height, concentration, and grain size of HDS, and (3) what bed morphology and depositional stratigraphy result from HDS.…”

Section: Introductionmentioning

confidence: 99%

High-Density Suspensions Formed Under Waves

Lamb¹,

Parsons²

2005

Journal of Sedimentary Research

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We performed a series of laboratory experiments to investigate the interactions of a turbulent wave boundary layer with a predominantly silt-size sediment bed. Quasi-steady, turbulent, highdensity suspensions (HDS) formed over a wide range of wave conditions and had near-bed (ϳ1 mm above bed) concentrations ranging from 17 to 81 g/l scaling roughly with the wave orbital velocity. HDS were defined by the presence of a lutocline, an abrupt change in vertical concentration gradient. Despite the initial bed being 70% silt and 20% sand, HDS had significant near-bed sand fractions ranging from 27 to 78%. Winnowing of the bed caused more concentrated HDS to be coarser grained, which in turn caused the suspensions to be thinner because of the greater settling velocity of the sediment. Our experiments are consistent with a dynamic feedback model where suspended sediment is limited through sediment-induced stratification expressed with a bulk Richardson number. However, our computed values of the bulk Richardson number converge to a value that is an order of magnitude less than the critical value of 0.25 that is typically assumed. The experimental wave orbital velocities (15-60 cm/s) and periods (3-8 s), as well as the characteristics of the HDS and the bed in our experiments, were comparable to observations made on the Eel shelf, California, during storm conditions when fluid mud has been observed.

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A note on turbulence calculations in the wave boundary layer

Cited by 45 publications

References 9 publications

Numerical simulation of tsunami-scale wave boundary layers

Numerical simulation of tsunami-scale wave boundary layers

One-Dimensional Wave Bottom Boundary Layer Model Comparison: Specific Eddy Viscosity and Turbulence Closure Models

High-Density Suspensions Formed Under Waves

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