Papers by Jonathan Pearson
Improved prediction of wave overtopping rates at vertical seawalls with recurve retrofitting
Ocean engineering, Jun 1, 2024
Solute Mixing in the Surf Zone
Journal of waterway, port, coastal, and ocean engineering, Jul 1, 2009
An experimental study has been undertaken within the U.K. Coastal Research Facility (CRF), locate... more An experimental study has been undertaken within the U.K. Coastal Research Facility (CRF), located at HR Wallingford Ltd. Detailed measurements were made to examine the on–off shore spreading of a solute, mostly inside the surf zone, for shore normal waves combined with a longshore current. The results show that the on–off shore mixing is significantly increased by almost 70 times, when compared to current-only conditions. A theoretical advection–dispersion mixing mechanism has been postulated. Using suitable estimates for the turbulent diffusion and on–off shore wave-induced velocity, a theoretical approximation to the overall mixing within the surf zone can be obtained. This theoretical analysis suggests that the on–off shore mixing in the surf zone is proportional to Hb 3∕2 , where Hb is the breaker wave height. It is demonstrated that within the surf zone, the on–off shore mixing is dominated by the effects of the on–off shore velocity. Some previous experimental studies to determine the magnitude of ...
Studio della tracimazione ondosa per diversi tipi di massi frangiflutti. Scritti in onore di Edoardo Benassai
Numerical and Experimental Predictions of Overtopping Volumes for Violent Overtopping Events
Storm waves breaking in the surf zone and crashing over seawalls are a violent natural phenomenon... more Storm waves breaking in the surf zone and crashing over seawalls are a violent natural phenomenon with the potential to cause enormous damage. Much of the existing design guidance for seawalls considers the mean overtopping discharge on the structure. Under impacting conditions, ...
Water Research, Mar 1, 2020
Microplastics are an emerging environmental contaminant. Existing knowledge on the precise transp... more Microplastics are an emerging environmental contaminant. Existing knowledge on the precise transport processes involved in the movement of microplastics in natural water bodies is limited. Microplastic fatetransport models rely on numerical simulations with limited empirical data to support and validate these models. We adopted fluorometric principles to track the movement of both fluorescent dye and florescent stained microplastics (polyethylene) in purpose-built laboratory flumes with standard fibreoptic fluorometers. Neutrally buoyant microplastics behaved in the same manner as a solute (Rhodamine) and more importantly displayed classical fundamental dispersion theory in uniform open channel flow. This suggests Rhodamine, a fluorescent tracer, can be released into the natural environment with the potential to mimic microplastic movement in the water column.
Proceedings of ... Conference on Coastal Engineering, Jun 23, 2017
A weakly compressible smoothed particle hydrodynamics (WCSPH) method is used to simulate the near... more A weakly compressible smoothed particle hydrodynamics (WCSPH) method is used to simulate the nearshore flow hydrodynamics. The wave induced dispersion and diffusion are determined for monochromatic waves with significant wave height of 0.12 m and the wave period of 1.2 sec (Sop=5%) based on WCSPH wave dynamics. The hydrodynamics of WCSPH model are compared to the laboratory results obtained from series of LDA measurements. The overall mixing coefficients across the nearshore are determined from WCSPH hydrodynamics. The mixing coefficients obtained are compared with the values determined from a series of fluorometric studies performed in a large-scale facility in DHI, Denmark. The results show that the wave profiles are in good agreement with the experimental data. The WCSPH model is proven to be well capable of estimating the dispersion across the nearshore.
Proceedings of ... Conference on Coastal Engineering, Dec 30, 2018
This study develops an accurate numerical tool for investigating optimal retrofit configurations ... more This study develops an accurate numerical tool for investigating optimal retrofit configurations in order to minimize wave overtopping from a vertical seawall due to extreme climatic events and under changing climate. A weakly compressible smoothed particle hydrodynamics (WCSPH) model is developed to simulate the wave-structure interactions for coastal retrofit structures in front of a vertical seawall. A range of possible physical configurations of coastal retrofits including re-curve wall and submerged breakwater are modelled with the numerical model to understand their performance under different wave and structural conditions. The numerical model is successfully validated against laboratory data collected in 2D wave flume at Warwick Water Laboratory. The findings of numerical modelling are in good agreement with the laboratory data. The results indicate that recurve wall is more effective in mitigating wave overtopping and provides more resilience to coastal flooding in comparison to base-case (plain vertical wall) and submerged breakwater retrofit.
Nonlinear Processes in Geophysics, Dec 14, 2011
Runup of long irregular waves on a plane beach is studied experimentally in the water flume at th... more Runup of long irregular waves on a plane beach is studied experimentally in the water flume at the University of Warwick. Statistics of wave runup (displacement and velocity of the moving shoreline and their extreme values) is analyzed for the incident wave field with the narrow band spectrum for different amplitudes of incident waves (different values of the breaking parameter Br σ ). It is shown experimentally that the distribution of the shoreline velocity does not depend on Br σ and coincides with the distribution of the vertical velocity in the incident wave field as it is predicted in the statistical theory of nonlinear long wave runup. Statistics of runup amplitudes shows the same behavior as that of the incident wave amplitudes. However, the distribution of the wave runup on a beach differs from the statistics of the incident wave elevation. The mean sea level at the coast rises with an increase in Br σ , causing wave set-up on a beach, which agrees with the theoretical predictions. At the same time values of skewness and kurtosis for wave runup are similar to those for the incident wave field and they might be used for the forecast of sea floods at the coast.
Experimental study of the runup of long nonlinear regular and irregular waves
EGU General Assembly Conference Abstracts, May 1, 2014
Seasonal effects of vegetation and flow rate on mixing and pollutant transport in constructed wetlands
Numerical modelling of hydraulic efficiency and pollution transport in waste stabilization ponds
Ecological Engineering, Sep 1, 2022
This paper reports results of small scale physical tests on vertical walls describing the probabi... more This paper reports results of small scale physical tests on vertical walls describing the probability distribution of wave by wave overtopping volumes at a plain vertical structure with a shingle foreshore slope. The present paper contributes to the existing knowledge on the distribution of overtopping volumes by analyzing the acquired Weibull shape parameter from the experiments consisted of a matrix of 180 test conditions (wave steepnesses, crest freeboards, water depths, shingle sizes) and, by comparing the test results with the empirical prediction. Alongside the outputs of this study, the measured Weibull b values under the VOWS project are also analyzed in the present paper. The results of this study showed that there is no apparent relationship between Weibull shape parameter and incident wave steepness, relative freeboard or, relative discharge.
Mixing Processes due to Breaking Wave Activity in the Coastal Zone
Coastal dynamics, 1998
Laboratory Investigation of Mixing in the Nearshore
ABSTRACT This paper describes an experimental study undertaken at DHI Water & Environment... more ABSTRACT This paper describes an experimental study undertaken at DHI Water & Environment, Denmark to investigate the solute mixing processes in the nearshore region. The mechanisms responsible for the mixing are shown to be dependant upon the interaction of the periodic orbital motions of the waves, the variable depth, wave induced vertical and lateral shear effects, the effects of Stokes drift and the bed and free surface boundary sources of turbulence. This study quantifies these processes through a series of direct detailed hydrodynamic measurements and by quantifying their integrated effects on a fluorescent solute tracer. This has lead directly to the determination of dispersion coefficients, an understanding of their dependence on the underlying processes and to new improved techniques for predicting pollutant dispersion coefficients.
Ecological Engineering, Nov 1, 2019
A field-based experimental study has been undertaken within a full-scale constructed wetland, des... more A field-based experimental study has been undertaken within a full-scale constructed wetland, designed to treat runoff from agricultural land in Knapwell, Cambridgeshire, UK. The effects of flow rate variation and natural vegetation ageing on the mixing characteristics are investigated over a eight month period. Detailed fluorometric measurements were made to examine the longitudinal spreading of a solute within the wetland. Between a UK November winter period, and June summer period, 125 tracer tests were undertaken for a range of dry weather and storm flow conditions, using an automated daily injection tracer system. The longitudinal dispersion results show that the dispersion is influenced by the flow rate for low discharge conditions, however, for higher discharges, the longitudinal dispersion becomes independent of discharge. Residence Time Distribution (RTD) curves are examined through a series of flow conditions for each testing month, ranging from transitional (Re~2000) to turbulent (Re~7000) flow conditions. For the conditions measured, differing flow rates produce changes in the RTD, demonstrating that higher flow rates induce shorter mean residence times, generating predominantly an advective flow regime. The effects of plant age are prominent on the mixing pattern. Towards the end of the plant annual cycle, in February/March, mixing pattern approaches complete mixing, longitudinal mixing increases significantly due to long tails on the RTDs, and mean flow velocity is retarded. This indicates that the dormant plant ABBREVIATIONS
Environmental Processes, Jun 23, 2018
The efficiency of pond and constructed wetland (CW) treatment systems, is influenced by the inter... more The efficiency of pond and constructed wetland (CW) treatment systems, is influenced by the internal hydrodynamics and mixing interactions between water and aquatic vegetation. In order to contribute to current knowledge of how emergent real vegetation affects solute mixing, and on what the shape and size effects are on the mixing characteristics, an understanding and quantification of those physical processes and interactions was evaluated. This paper presents results from tracer tests conducted during 2015-2016 in six full-scale systems in the UK under different flow regimes, operational depths, shapes and sizes, and in-/outlet configurations. The aim is to quantify the hydraulic performance and mixing characteristics of the treatment units, and to investigate the effect of size and shape on the mixing processes. Relative comparison of outlet configuration, inflow conditions, and internal features between the six different treatment units showed variations in residence times of up to a factor of 3. A key outcome of this study, demonstrated that the width is a more important dimension for the efficiency of the unit compared to the depth. Results underlined the importance of investigating hydrodynamics and physics of flow in full-size units to enhance treatment efficiency and predictions of water quality models.
Water Resources Research, May 1, 2016
River ecosystems are influenced by contaminants in the water column, in the pore water and adsorb... more River ecosystems are influenced by contaminants in the water column, in the pore water and adsorbed to sediment particles. When exchange across the sediment-water interface (hyporheic exchange) is included in modeling, the mixing coefficient is often assumed to be constant with depth below the interface. Novel fiber-optic fluorometers have been developed and combined with a modified EROSIMESS system to quantify the vertical variation in mixing coefficient with depth below the sediment-water interface. The study considered a range of particle diameters and bed shear velocities, with the permeability P eclet number, Pe K between 1000 and 77,000 and the shear Reynolds number, Re à ; between 5 and 600. Different parameterization of both an interface exchange coefficient and a spatially variable in-sediment mixing coefficient are explored. The variation of in-sediment mixing is described by an exponential function applicable over the full range of parameter combinations tested. The empirical relationship enables estimates of the depth to which concentrations of pollutants will penetrate into the bed sediment, allowing the region where exchange will occur faster than molecular diffusion to be determined.
Quantifying Microplastic Dispersion Due to Density Effects
Water
The presence of dense submerged vegetation alters mixing characteristics in open channel flows as... more The presence of dense submerged vegetation alters mixing characteristics in open channel flows as they cause differential velocities inside and above canopies. The prediction models for longitudinal mixing in the presence of submerged canopies often use the drag coefficient to represent the canopy, which limits the usability of the models when the canopy properties are not fully understood. Here, attempts were made to present a methodology which can be used for deriving the coefficient of longitudinal dispersion in the presence of submerged vegetation based on velocity measurements, using a mixing length approach to model turbulence. An experimental study was conducted in a large-scale laboratory facility to investigate the longitudinal dispersion characteristics in open channel flow with submerged aquatic vegetation canopies. Detailed velocity and solute tracer measurements were undertaken for a representative range of flow velocities. The velocity measurements were used for derivi...
Microplastic Transport Dynamics in Surcharging and Overflowing Manholes
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Papers by Jonathan Pearson