Tidal EcoMorphodynamics (EGH)
We will design and build a fully instrumented facility for the physical modeling of biota-sediment-flow interactions and morphodynamics of tidal channels, estuaries and deltas. This one-of-a-kind experimental facility will provide high temporal and spatial resolution of the flow field and bed morphology to study the morphodynamic evolution at the riverine/tidal interface.
Effects of mean grain size on ripple formation (GH)
Prediction of equilibrium ripple size rely on a single grain size, but the seabed is made up of grains of different sizes, shapes and geometries. We will conduct a series of laboratory experiments on an oscillatory tunnel to address the role of heterogeneous sediment mixtures on ripple morphology. We will: a) determine conditions for which using median grain size results in accurate predictions and b) examine near bed sorting with grain size mixtures.
Forces on aquatic vegetation under oscillatory flow (EH)
We will conduct experiments on an oscillatory tunnel at the Ven Te Chow Hydrosystems Lab to directly measure forces exerted by oscillatory flow on arrays of rigid and flexible vegetation. A detailed analysis of the flow using PIV and direct drag measurements from a newly developed drag plate on different array configurations (random vs staggered, submerged vs emergent arrays) will help us characterize the drag forces in terms of a drag coefficient, Cd, dependent of the plant and array characteristics, as well as the mean and turbulent flow statistics.
Unified drag coefficient characterization for unidirectional vegetated flows (EH)
While several research groups have dealt with unidirectional flow through aquatic vegetation, characterization of the flow still depends strongly on a drag coefficient which is not known a priori, and is left as a fitting or calibration parameter for laboratory and computational models. We utilize results from experiments at Cornell University and IH-Cantabria, coupled with published data on vegetated flows, to obtain a more general parameterization of Cd for rigid and flexible, emergent and submerged vegetation, using a combination of physical analysis and machine learning tools.
Effect of spectral width on the onset and evolution of sand bedforms (GH)
Research groups have studied formation and evolution of sand bedroom under waves and combined flows (waves and currents). We’ll use data collected on large-scale experiments at the IH-Cantabria to explore the differences between regular, monochromatic waves (optimal for laboratory studies) and irregular, random waves (more representative of conditions in nature) on the resulting bedforms characteristics as a function of the spectral width of the lab-generated waves.
Effects of vegetation on bed morphology (EGH)
Using data from large-scale experiments conducted at the IH-Cantabria, we’ll investigate the effect of vegetation on the appearance and evolution of sand ripples up- and downstream of an array of rigid cylinders. Synchronous records of velocity, suspended sediment concentration and free surface elevation are coupled with time lapsed photographs and mappings with a 3D laser scanner to characterize the effect of vegetation on bed morphology, erosion and deposition patterns at the up- and downstream edges of the patch.
PAST PROJECTS
Machine Learning applications on vegetated flow
We used genetic programming to find a predictor of mean flow speed on
vegetated flows. Using experimental data published from several
research groups, we apply a genetic programming algorithm to obtain a
predictor that matches the performance of “physics-based” models. The
resulting predictor shows a similar structure with a simpler
coefficient that provides further insight into the dependencies of the
considered variables.
Sediment dynamics within aquatic ecosystems
We explore the effects of submerged arrays of living organisms (SALOs, both vegetation and benthic populations) on sediment dynamics. The presence of SALOs alter the mean and turbulent flow conditions, effectively altering the impact of flow structures on the bed. Both physical (e.g., damped mean velocities, generation of stem-, leaf- and array-scale turbulence) and biological (e.g., rooting systems, biofilms, mucus) effects must be considered for a proper characterization of the bed stabilizing/destabilizing effects of SALOs. Through laboratory experiments, we monitored the flow field and concentrations of suspended sediment within an array of rigid cylinders to determine resuspension thresholds under waves, currents, and combined flows.
Hydrodynamics of aquatic vegetation
We conducted laboratory experiments on arrays of rigid cylinders and flexible, live vegetation, to study the mean and turbulent characteristics of the flow. Using particle image velocimetry (PIV) and synchronous direct drag measurements we characterized the drag exerted by the obstructions in terms of a drag coefficient that depends on both properties of the flow (Re) and the array (diameter, frontal area and solid volume fraction). The relationship for Cd obtained from experiments on arrays of emergent rigid cylinders successfully predicts drag on arrays of flexible, live vegetation.