Wave-Current Impact on Shear Stress Patterns around 3D Shallow Bedforms

Observations from wave basin experiments and wave-resolving numerical simulations demonstrate the effect of wave-current interaction on shear stress around a sandy mound. Observations from the wave basin show that the mound deformation rate and morphological patterns depend on the mixture of waves and currents in the incident flow conditions....

Erosion Behavior of Sand-Silt Mixtures: Revisiting the Erosion Threshold

The erosion threshold, beyond which bed sediments start to move, is a key parameter describing sediment transport processes. For silt-dominated mixtures, in which the grain size is between sand and clay, existing experimental studies exhibit contradictory observations. That is, the erosion was either sand-like or clay-like, suggesting...

Estimating the roughness of muddy beds: A study based on in-site measurements and numerical modeling

Bed roughness is an important parameter for the prediction of sediment transport as well as calculating flow conditions near the bed. Numerical models are extensively used to make these predictions. In these models it is fundamental to have proper values for bed roughness. The bed roughness is being estimated using a dataset from an ongoing...

A new modelling method for representing the effect of spiral flow on the bed shear stress

This thesis presents a new methodology for representing the effect of spiral flow on the bed shear stress magnitude and direction, using a low-vertical-resolution three-dimensional model. Furthermore, it discusses the performance of the new methodology in comparison with conventional high-vertical-resolution three-dimensional and depth-averaged...

Modelling effects of an asphalt road at a dike crest on dike cover erosion onset during wave overtopping

Structures integrated in a grass-covered dike may increase erosion development. Currently, safety assessment methods for flood defences are only applicable for a conventional grass-covered dike and the effects of structures on dike cover erosion are poorly understood. Since many dikes have a road on top, it is important to study the effect of...

Gravity Based Foundation: Scour and design optimisation

Within Royal HaskoningDHV an innovative concept is thought to be feasible as a new foundation for larger wind turbines in deeper waters. In this thesis the development of this innovative offshore wind turbine foundation was aided. The research focused on two topics: - Scour at this gravity based foundations. - Possible design optimisations with...

Modelling and parameterizing the hydro- and morphodynamics of curved open channels

Meandering rivers are interesting features of the landscape due to their aesthetically pleasing forms. There is an abundance of scientific studies on meandering rivers, however, their behaviour is still not fully understood. The complexity of the flow, bed morphodynamics and bank stability, the related uncertainties in water and sediment motion,...

Decelerating open-channel flow in a gradual expansion

The velocity and turbulence distributions of decelerating open-channel flow in a gradual expansion were measured using LDV equipment. The results show that the logarithmic law can describe the mean velocity in the bottom region well while the Coles’ law can be applied to the outer region. The shear velocity can be determined both by the...

Modelling Floodplain Biogeomorphology

Understanding the interactions between the ecosystem and the morphology of river floodplains, i.e. floodplain biogeomorphology, is becoming increasingly important in view of modern river management and climate change. There is a need for predictive models for the natural response of river floodplains to hydraulic measures and river...

Coarse particles' threshold of motion under shoaling waves

The threshold of motion of coarse particles under regular shoaling waves is studied. Experiments are performed to investigate the effects of bed fluid acceleration on coarse particle stability. By varying wave height, wave period and water depth, combinations of similar peak orbital velocities and weak to strong intra-wave accelerations were...

Grain size influence on sediment transport in sheet flow conditions for combined wave-current flow

Especially during storms the coast-profile can change dramatically. During storms large waves cause high oscillatory water velocities near the bottom and the bed becomes plane and sheet flow becomes the dominant sediment transport mode. Because field measurements are difficult to perform in-situ, laboratory experiments concerning these processes...

Flow Equations for River Bends Derived by Tensor Calculus and Flow Acceleration in Depth-Averaged Models

Flow equations for application in river bends are derived. Coordinate transformations are achieved by tensor calculus. The momentum equations are formulated in a cylindrical coordinate system and in a cylindrical bed-following coordinate system. The depth-averaged momentum equations in a cylindrical bed-following coordinate system are derived....

Streamline curvature and bed resistance in shallow water flow

The relationship between streamline curvature and bed resistance in shallow water flow with little side constraint, as derived in 1970 by H.J. Schoemaker, is reconsidered. Schoemaker concluded that the bed resistance causes the curvature of a free streamline to grow exponentially with the distance along this streamline, thus giving rise to a...

Shear-Stress and Sediment Distribution in a Meander Bend

A one-meter wide, meandering flume with movable sand bed was utilized in these experiments. Uniform flow was established at discharges of 20, 35, and 50 l/sec. Velocities near the bed, the distribution of sediment in transport, bed geometry, and strength of secondary flow were determined at each discharge . Bed shear stress was assumed to be...

Littoral drift computations on mutual wave and current influence

11th Conference on Coastal Engineering in London 1968, the author presented a method for computing the littoral drift starting from the longshore current velocity as this is generated by the waves and with the assumption that the material is stirred up by the waves. In this paper measurements in a model basin are described by which the procedure...

Anwendung der Aehnlichkeitsmechanik und der Turbulenzforschung auf die Geschiebebewegung

Ph.D thesis of Shields, original version in German. This document is the basis of all modern sediment transport formulae, and develops the concept of bed shear stress.

Application of similarity principles and turbulence research to bed-load movement

Translation of the Ph.D. thesis of A. Shields "Anwendung der Aehnlichkeitsmechanik und der Turbulenzforschung auf die Geschiebebewegung".