A combination of numeric hydrodynamic models, a large-clast inverse sediment-transport model, and extensive field measurements were used to discriminate between a tsunami and a storm striking Anegada, BVI a few centuries ago. In total, 161 cobbles and boulders were measured ranging from 1.5 to 830 kg at distances of up to 1 km from the shoreline and 2 km from the crest of a fringing coral reef. Transported clasts are composed of low porosity limestone and were derived from outcrops in the low lying interior of Anegada. Estimates of the near-bed flow velocities required to transport the observed boulders were calculated using a simple sediment-transport model, which accounts for fluid drag, inertia, buoyancy, and lift forces on boulders and includes both sliding and overturning transport mechanisms. Estimated near-bed flow velocities are converted to depth-averaged velocities using a linear eddy viscosity model and compared with water level and depth-averaged velocity time series from high-resolution coastal inundation models. Coastal inundation models simulate overwash by the storm surge and waves of a category 5 hurricane and tsunamis from a Lisbon earthquake of M 9.0 and two hypothetical earthquakes along the North America Caribbean Plate boundary. A modeled category 5 hurricane and three simulated tsunamis were all capable of inundating the boulder fields and transporting a portion of the observed clasts, but only an earthquake of M 8.0 on a normal fault of the outer rise along the Puerto Rico Trench was found to be capable of transporting the largest clasts at their current locations. Model results show that while both storm waves and tsunamis are capable of generating velocities and temporal acceleration necessary to transport large boulders near the reef crest, attenuation of wave energy due to wave breaking and bottom friction limits the capacity of storm waves to transport large clast at great inland distances. Through sensitivity analysis, we show that even when using coefficients in the sediment-transport model which yield the lowest estimated minimum velocities for boulder transport, storm waves from a category 5 hurricane are not capable of transporting the largest boulders in the interior of Anegada. Because of the uncertainties in the modeling approach, extensive sensitivity analyses are included and limitations are discussed.

Inverse modeling of velocities and inferred cause of overwash that emplaced inland fields of boulders at Anegada, British Virgin Islands

Advances in swash-zone research: Small-scale hydrodynamic and sediment transport processes

[1] A numerical model solving incompressible Reynolds-averaged Navier-Stokes equations, combined with a two-equation k-ω turbulence closure, is used to study converging-diverging effects from a sloping bed on turbulent (oscillatory) wave boundary layers. Bed shear stresses from the numerical model are first validated against hydraulically smooth and rough data from flat bed experiments in the form of wave friction factor diagrams. The results show that the model provides acceptable accuracy for wave orbital amplitude to roughness length ratios a/kN ≥ 20. Validation against experimental measurements for steady streaming induced by a skewed free stream velocity signal is also provided. We then simulate a series of experiments involving oscillatory flow in a convergent-divergent smooth tunnel, and a good match with respect to bed shear stresses and streaming velocities is achieved. The streaming is conceptually explained using analogies from steady converging and diffuser flows. A parametric study is undertaken to assess both the peak and time-averaged bed shear stresses in converging and diverging half periods under rough-turbulent conditions. The results are presented as friction factor diagrams. A local similarity condition is derived for relating oscillatory flow in a convergent-divergent tunnel, as considered herein, to shoaling shallow-water waves by matching spatial gradients in the free stream orbital length.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008JC005045

Bed slope effects on turbulent wave boundary layers: 1. Model validation and quantification of rough‐turbulent results

https://nottingham-repository.worktribe.com/preview/859081/Manuscript-SE-2016.pdf

Prediction of the surface temperature of building-integrated photovoltaics: Development of a high accuracy correlation using computational fluid dynamics

Six one-dimensional-vertical wave bottom boundary layer models are analyzed based on different methods for estimating the turbulent eddy viscosity: Laminar, linear, parabolic, \Ik\N—one equation turbulence closure, \Ik\N–e—two equation turbulence closure, and \Ik\N-ω—tw 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 \Ik\N–ω 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 \Ik\N–e models. Normalized errors between model predictions and turbulence kinetic energy profiles showed that the \Ik\N–ω 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 \Ik\N–ω model should be used.

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

: Seven one-dimensional wave bottom boundary layer models have been analyzed based on different methods for estimating the turbulent eddy viscosity (laminar, linear, linear-exponential, parabolic. k-one-equation turbulence closure, k-epsilon-two-equation turbulence closure, and k-omega-two-equation turbulence closure). Two generic test cases displayed similar velocity profiles for all (he models with the exception of the laminar model. Boundary layer and sheer stress estimates, however, did show some differences. The linear and parabolic models predicted bed shear stress twice as large as the k-omega model and 25 percent larger than the k or k-epsilon models. Phase leads between the predicted bed shear stress and the free-stream velocity matched expectations with the laminar case leading by 45 degrees and the other models predicting a phase lead of the shear stress maxima between 12 and 18 degrees with respect to the free-stream velocity maximum. Comparisons to laboratory data on smooth and rough beds showed that overall the linear model was slightly more accurate than the parabolic linear-exponential. k, and k-omega models. The least accurate were the laminar and k-epsilon models. Based on the two laboratory simulations (forced by a 9.72-s sinusoidal wave form with an amplitude of 2 m s(-1)). it is shown that the extra computational effort required for the turbulence closure schemes does not afford an improvement in predictive capability in a one-dimensional boundary layer model. Therefore. it is recommended that the linear or parabolic model be used to rapidly determine flow characteristics for one-dimensional studies of the wave bottom boundary layer.

/pdf/wave-bottom-boundary-layer-models-for-smooth-and-rough-beds-cwcmtpg00t.pdf

Wave Bottom Boundary Layer Models for Smooth and Rough Beds

https://ascelibrary.org/doi/pdf/10.1061/%28ASCE%290733-950X%282006%29132%3A2%28141%29

Closure to “One-Dimensional Wave Bottom Boundary Layer Model Comparison: Specific Eddy Viscosity and Turbulence Closure Models” by Jack A. Puleo, Oleg Mouraenko, and Daniel M. Hanes

Oleg Mouraenko

Papers

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

Wave Bottom Boundary Layer Models for Smooth and Rough Beds

Closure to “One-Dimensional Wave Bottom Boundary Layer Model Comparison: Specific Eddy Viscosity and Turbulence Closure Models” by Jack A. Puleo, Oleg Mouraenko, and Daniel M. Hanes