Bed Level Research Articles

Vascularized composite allotransplants as a mechanistic model for allograft rejection - an experimental study.

Vascularized composite allotransplants (VCAs) seem to have several unique features of clinical and experimental importance, including uniquely definable lymphatic drainage that can be easily accessed at the level of ipsilateral regional node beds. Thus, VCA offers a unique opportunity to assess the relative contribution of peripheral and secondary lymphoid tissue to the process of rejection. We transplanted hind limb grafts from C3H donors to six different groups of C57BL/6 recipients: Spleen+ Map3k14-/- ; Spleen- Map3k14-/- ; Spleen+ Node- Map3k14-/- ; and Spleen- Node- Map3k14-/- . As positive controls, we used Map3k14+/- with or without spleen. Map3k14+/- mice demonstrated an average graft survival of 9.6 and 9.2days for Spleen- and Spleen+ Map3k14+/- , respectively. Rejection in the Map3k14-/- group was considerably delayed (28.4days, P=0.002) in all recipients. The Spleen- Map3k14-/- mice rejected their hind limb allografts in an even more delayed fashion compared to Spleen+ Map3k14-/- (54.4days, P=0.02). Histological analysis of skin showed that acute rejection in both Map3k14+/- mice groups was graded as Banff III or Banff IV. In the Map3k14-/- groups, rejection was graded as Banff III. We demonstrated that in the absence of lymph nodes, grafts reject in a delayed fashion. Also, splenectomy in alymphoplastic mice further extends graft survival, but does not eliminate rejection all together.

Association between coronavirus disease 2019 (COVID-19) and long-term exposure to air pollution: Evidence from the first epidemic wave in China.

People with chronic obstructive pulmonary disease, cardiovascular disease, or hypertension have a high risk of developing severe coronavirus disease 2019 (COVID-19) and of COVID-19 mortality. However, the association between long-term exposure to air pollutants, which increases cardiopulmonary damage, and vulnerability to COVID-19 has not yet been fully established. We collected data of confirmed COVID-19 cases during the first wave of the epidemic in mainland China. We fitted a generalized linear model using city-level COVID-19 cases and severe cases as the outcome, and long-term average air pollutant levels as the exposure. Our analysis was adjusted using several variables, including a mobile phone dataset, covering human movement from Wuhan before the travel ban and movements within each city during the period of the emergency response. Other variables included smoking prevalence, climate data, socioeconomic data, education level, and number of hospital beds for 324 cities in China. After adjusting for human mobility and socioeconomic factors, we found an increase of 37.8% (95% confidence interval [CI]: 23.8%–52.0%), 32.3% (95% CI: 22.5%–42.4%), and 14.2% (7.9%–20.5%) in the number of COVID-19 cases for every 10-μg/m3 increase in long-term exposure to NO2, PM2.5, and PM10, respectively. However, when stratifying the data according to population size, the association became non-significant. The present results are derived from a large, newly compiled and geocoded repository of population and epidemiological data relevant to COVID-19. The findings suggested that air pollution may be related to population vulnerability to COVID-19 infection, although the extent to which this relationship is confounded by city population density needs further exploration.

Scour protection around bridge pier and two-piers-in-tandem arrangement

ABSTRACT In the present study, experiments were carried out on circular model bridge piers individually as well as with two-piers-in-tandem arrangement under clear water scour conditions predominantly caused by formation of horseshoe vortex. Independent collar plates around bridge piers and a continuous collar plate covering both the piers were installed as countermeasures against scouring. In case of two piers, efficacy of scour-protection devices for front and rear piers was checked for the overall stability. Performance potential was noted to be about 67% and 100% for continuous collar plates of sizes 2.5D and 3.0D around two piers at average bed level with spacing of 2.0D; where D is the diameter of the pier. During degradation of general bed level, a group of three continuous collar plates was employed around both the piers to ensure considerable reduction of scour. A group of three collar plates of sizes 2.5D and 3.0D having an inter-plate spacing Cs equal to D/4 with the middle plate placed at the average bed level reduced scour by 79 and 82%, respectively, in comparison to the scour depth for an unprotected pier. A mathematical model was developed by multivariate regression analysis to prediction the scour depth for both the pier arrangements.

Relating millimeter‐scale turbulence to meter‐scale subtidal erosion and accretion across the fringe of a coastal mangrove forest

AbstractWithin a wave‐exposed mangrove forest, novel field observations are presented, comparing millimeter‐scale turbulent water velocity fluctuations with contemporaneous subtidal bed elevation changes. High‐resolution velocity and bed level measurements were collected from the unvegetated mudflat, at the mangrove forest fringe, and within the forest interior over multiple tidal cycles (flood–ebb) during a 2‐week period. Measurements demonstrated that the spatial variability in vegetation density is a control on sediment transport at sub‐meter scales. Scour around single and dense clusters of pneumatophores was predicted by a standard hydraulic engineering equation for wave‐induced scour around regular cylinders, when the cylinder diameter in the equations was replaced with the representative diameter of the dense pneumatophore clusters. Waves were dissipated as they propagated into the forest, but dissipation at infragravity periods (> 30 s) was observed to be less than dissipation at shorter periods (< 30 s), consistent with the predictions of a simple model. Cross‐wavelet analysis revealed that infragravity‐frequency fluctuations in the bed level were occasionally coherent with velocity, possibly indicating scour upstream of dense pneumatophore patches when infragravity waves reinforced tidal currents. Consequently, infragravity waves were a likely driver of sediment transport within the mangrove forest. Near‐bed turbulent kinetic energy, estimated from the turbulent dissipation rate, was also correlated with bed level changes. Specifically, within the mangrove forest and over the unvegetated mudflat, high‐energy events were associated with erosion or near‐zero bed level change, whereas low‐energy events were associated with accretion. In contrast, no single relationship between bed level changes and mean current velocity was applicable across both vegetated and unvegetated regions. These observations support the theory that sediment mobilization scales with turbulent energy, rather than mean velocity, a distinction that becomes important when vegetation controls the development of turbulence.

Thousands of Potholes in the Mekong River and Giant Pedestal Rock from North-eastern Thailand: Introduction to a Future Geological Heritage Site

A site with thousands of potholes, locally named “Samphunbok (SPB),” and a giant pedestal (mushroom) rock possess a very high geological value. The potholes are being formed on the riverbed of the Mekong River; whereas the giant pedestal rock is the largest on the Khorat Plateau, and is located in Ubon Ratchathani province, north-eastern Thailand. Based on detailed geological, geomorphological, and sedimentological perspectives, this paper presents the geological history of both erosional features for the future promotion of the Global Geopark Network. The giant pedestal rock is likely to be a remnant of degradation and weathering after a regional tectonic event. It is sculptured in the fracture zone of thick sandstone beds after uplifting and folding. No evidence of abrasion by wind was found. The formation of potholes is limited inside the Mekong River bankfull elevation. The appearance of potholes in different levels of the sandstone beds infers their formation in relation to the vertical evolution of the Mekong River. All geological data shown in this paper confirm the rareness of potholes and the giant pedestal rock in terms of how they were sculptured and preserved through time. These erosional features at SPB are discussed and introduced in this paper as a global geological heritage site.

Fine particle flow pattern and region delimitation in fountain confined conical spouted beds

A novel borescopic technique together with the monitoring of pressure fluctuation signals (power spectral distribution, PSD) has been used to track fine particles and characterize solid flow dynamics in fountain confined conical spouted beds. Radial and axial particle velocity profiles have been obtained for different configurations, and spout-annulus and fountain core-periphery interfaces have been delineated. The downward particle velocities in the annulus peak at intermediate positions in this zone, whereas the upward velocities in the dilute zones (spout and fountain core) peak at the axis or close to this position. Among the different configurations analysed in this work, the system without draft tube shows the greatest vertical particle velocities in almost all the different radial and axial positions. The evolution of the spout size along the bed depends on the configuration used, but all of them differ from those commonly reported in the literature. Thus, the spout expands from the bed bottom to the surface, without any neck at an intermediate bed level. Furthermore, the cross-sectional spout shape has been delineated in the systems with open-sided draft tube, and significant spout expansion is observed due to air percolation from the spout into the annulus through the opened faces. Finally, the average spout diameters of the systems without draft tube and with open-sided draft tubes have been compared with those predicted by literature correlations. Those proposed by San José et al. and Volpicelli et al. provide the best fit for the configurations without draft tube and with open-sided draft tube, with their relative errors being 9.83% and 8.88%, respectively.

An eco-parametric method to derive sedimentation rates for coastal saltmarshes

The saltmarsh plant Spartina alterniflora was introduced to the Jiangsu coasts, China and serves as an ecological engineer to reduce near-bed shear stress, trap fine-grained sediments and protect the coast from wave-induced erosion. The saltmarshes thus could record the Spartina colonization-driven changes within the sedimentary layers. Based on these ecological and sedimentological changes in sediments, we present a new eco-parametric method to estimate the sedimentation rate for the newly-formed wetlands in the Yancheng Wetland Nature Reserve for Rare Birds, Jiangsu. Sediment cores and satellite imagery were used to identify the thickness of accumulated sediment layers and the time since the Spartina colonization. We defined the original ground on which Spartina alterniflora initially colonized using pigment concentrations, grain size and stable carbon isotopic compositions of organic matter (δ13C) in sediments. We also determined the time mark of the Spartina colonization by examining the Landsat images over 1982–2018 to discriminate the Spartina alterniflora from other native plants and geomorphological features. These two datasets yielded a sedimentation rate of 3.3 cm/yr for Core A and of 9.6 cm/yr for Core B, the latter evidenced by an increase of ~ 0.51 m in the bed level from 2008 to 2014. Combining the 210Pb dating method, we further estimated the sedimentation rate for the layers beneath the original ground, which was comparable to that of the bare flats in the Jiangsu coast. Even though this new method is only applicable to newly-formed saltmarshes, it helps identify the recent sedimentation events as well as reveal the environmental changes and the evolution of saltmarsh-bare flat systems due to the interplay between vegetation, hydrodynamics and sediment dynamics. It thus could be an efficient and cost-effective tool for an improved understanding of the response of coastal wetlands to a changing climate/environment.

Simulation of the Hydrodynamic Functioning of the Cavally River Using a Coupled 1D-2D Model in the Ity Area (Zouan-Hounien in Côte d’Ivoire)

In recent years, the Cavally River has been subject to multiple activities, including the construction of diversion channels and a bridge that makes it vulnerable to flooding. In order to assess the impact of these hydraulic structures on the river hydrodynamic functioning, a 1D-2D model was realized. The implementation of the 1D-2D model consisted of first running the 1D model, then the 2D model, and finally in coupling them. The 1D-2D model was designed with the 1988 flood hydrograph, a Manning’s coefficient of 0.052 m1/3/s for the minor bed and 0.06 m1/3/s for the major bed. The results of the hydraulic model show that the velocities are almost identical to those of the Cavally in natural operation. The values of the velocities are included between 0.4 m/s and 1.3 m/s at the level of the minor bed of the river and between 0.06 m/s and 0.71 m/s at the level of the floodplains. The average water level for flood propagation is 262.37 ± 0.44 m before construction of the structures and 262.23 ± 0.85 m after construction of the structures. The 0.41 m reduction in water level due to the diversion canal and bridge is negligible compared to the total fluctuations of the Cavally River, which vary from 6 to 7 m over the year.

FLOOD EVENTS AS GEOMORPHIC THRESHOLDS FOR CHANNEL BED LEVEL CHANGE

Channel bed levels are highly dynamic in time and across space, constantly adjusting under the influence of natural and anthropogenic controls. The aim of this study was to assess the role of flood events recorded between 1994 and 2018 in the bed elevation changes documented on the major tributaries of Trotuș River (Eastern Carpathians). To this purpose, the data from fifteen gauging stations was used, based on which the evolution trends of channel bed levels were determined for the investigated channel reaches. The role of geomorphic threshold was assigned to stream power. The daily maximum and total values of this parameter were used to explain the bed elevation shifts. The average channel bed deepening rate was 2.2 cm/yr. Depending on the variation trend of channel bed levels, three evolution patterns could be distinguished in relation to the reference year: (i) a category where channel degradation was nearly continuous; (ii) another one where initial aggradation of the channel bed occurred, ensued by continuous degradation, without reverting to the initial state, and (iii) a group with oscillating aggradation-degradation evolution resulting in the eventual recovery of the initial state. The recovery time for changes triggered by major flood events ranged between one and nearly 10 years, whereas in the case of shifts generated by high frequency, low magnitude events, the recovery time was maximum one year. Over short term flood events drive the direction and intensity of channel bed elevation adjustments.

Improving the carrying capacity of irrigation canals: Al-Tawfiky diversion

ABSTRACT The morphological changes in the irrigation channel cross-section affect its hydraulic efficiency and carrying capacity with time. Periodic maintenance activities are applied to reach maximum carrying capacity. In many cases, removing the total amount of deposit inside canal cross-section above the design bed level is not the optimum maintenance solution hydraulically and economically. Additional discharge must be applied to canal intake to achieve the design water level. Al-Tawfiky Diversion is one of the main irrigation canals in the Delta region. It extended with a length of 175 km to serve 716,540 feddan. The study encloses the first reach from intake to km 36.400 upstream Jamjara regulator. This research aims to detect the most inefficient reaches along the selected study canal reach based on the actual characteristics of the surveyed canal cross-sections, and identifying the most proper maintenance scenario hydraulically and economically. Three hundred and fifty-one cross-sections along the study reach were surveyed. The different hydraulic parameters of these cross-sections were calculated. The data was analyzed and criterion for detecting the most inefficient sub-reaches was introduced. An empirical equation connecting the applied maintenance activities with channel conveyance was deduced. A mathematical model for the study reach was built and calibrated using (SOBEK-1D) to evaluate the proposed four maintenance scenarios.

ALLOWANCE FOR FORMATION OF MEGA SAND WAVES ON THE SEABED IN THE DESIGN OF FAIRWAYS IN ESTUARIES WITH STRONG CURRENTS

The declared depth in port access channels is often maintained by dredging and monitored by regular bathymetric surveys. However, at remote sites these activities are not cost-effective and the channel depth would need to be defined based on the surveyed depth plus an allowance for sedimentation and variability in bed levels. This allowance can especially be significant in estuaries with strong tidal currents, where mega bedforms, including sand waves, develop on the seabed due to the prevailing strong current flows. The mega sand waves are highly mobile and fluctuate in height as they migrate over the seabed. Mega sand waves and mega ripples with a height up to approx. 3.2 m were observed in multi-beam bathymetric survey undertaken in the offshore entrance to the Geba River estuary in Guinea Bissau. Supramax bulk carriers with a draft of 11-12 m are planned to transit this area on departure from a proposed phosphate export terminal located further upstream in the estuary.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5Gmy9yQkfno

DATA-MODEL COMPARISONS OF STORM PROCESSES DURING HURRICANE HARVEY

During tropical cyclones, processes including dune erosion, overwash, inundation, and storm-surge ebb can rapidly reshape barrier islands, thereby increasing coastal hazards and flood exposure inland. Relatively few measurements are available to evaluate the physical processes shaping coastal systems close to shore during these extreme events as it is inherently challenging to obtain reliable field data due to energetic waves and rapid bed level changes which can damage or shift instrumentation. However, such observations are critical toward improving and validating model forecasts of coastal storm hazards. To address these data and knowledge gaps, this study links hydrodynamic and meteorological observations with numerical modeling to 1) perform data-model inter-comparisons of relevant storm processes, namely infragravity (IG) waves, storm surge, and meteotsunamis; and 2) better understand the relative importance of each of these processes during hurricane impact.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/kUizy8nK3TU

Experimental study of local scour around submerged compound piles in steady current

Many subsea structures have non-uniform geometries, which extend only a finite distance above the seabed. To better understand local scour at these structures, this paper presents scour measurements from an experimental study of submerged compound piles comprised of a circular superstructure supported by a circular foundation. The experiments were conducted in the clear-water regime and considered the effect of three different ratios describing the structural geometry: (i) the overall height of the compound structure above the initial bed level to the diameter of the super-structure h1/D1; (ii) the height of the foundation exposed above the initial bed level relative to the overall height of the superstructure h2/h1; and (iii) the diameter of the foundation to that of the superstructure D2/D1. In all cases D2≥D1 and h1≥h2≥0 (i.e. the foundation and superstructure where never buried). The experimental results indicate that, if all other parameters are held constant, the non-dimensional equilibrium scour depth S0/D2 increases with both h1/D1 and h2/h1, and decreases as D2/D1 increases. To quantitatively explain these trends the experimental results are compared with a range of existing methods to predict scour depth for non-uniform (or complex) surface piercing piles. Of these methods it is found that an effective pile height and an effective pile diameter, computed using simple geometric arguments, give good agreement. The concept of effective height is also shown to collapse time-scale measurements of the scour process convincingly across the full range of experimental results and to explain the extent and shape of the local scour hole reasonably well. Collectively, these findings suggest that the calculation of an effective height may be used to provide a reasonable first approximation to estimate the rate and extent of local scour around submerged compound structures.

Comprehensive assessment of clinical and immune disorders in patients with acute concussion

Introduction. Craniocerebral trauma remains one of the most common forms of brain pathology. Its relevance is determined by both, high prevalence and significant financial costs associated with the treatment, and rehabilitation of injured. Mild forms predominate in the general structure of injury. Immune response is one of the manifestations characteristic for a complex of biochemical and pathophysiological reactions triggered in the brain in response to injury. At the same time, the subtle mechanisms of its functioning and their role in pathogenesis of diseases remain the subject of discussion. Our research was aimed to study the role of immune reactions in the pathogenesis of mild brain injury. Materials and methods. 22 patients with concussion (aged from 20 to 45) were examined. The control group included 37 healthy individuals aged 20 to 46. The examination included the collection of complaints, medical history, assessment of somatic and neurological status, neuropsychological testing. The object of laboratory research was venous blood. Attention was mainly paid to the T-helpers of central (CM, CD45RA–CD62L+) and effector (EM, CD45RA–CD62L–) memory, which were evaluated using multicolored cytometric analysis. Results. Patients presented complaints of general and cognitive nature upon admission to the hospital. Cerebellar lesion symptoms dominated while neurological status evaluation. Neuropsychological examination allowed us to detect neuro-dynamic and regulatory disorders predominance. While conducting the analysis of the main stages of cell maturation in the blood of patients with concussion, it was noted that there was a significant increase in both, relative and absolute content of central memory T-helpers compared to the control group. At the same time, the percentage of EM Th in those with injury was slightly reduced. Also, in patients with injured Th cells of central memory, the relative content of Th1 cells decreased and the relative content of Th17 cells increased. In addition, within the CM Th pool, there was an increase in the proportion of three types of Th17 — CCR6+DN Th17, Th17.1 and «classic» CCR4+CXCR3– Th17. Conclusion. Changes in T-helpers of central memory and T-helpers of peripheral memory subpopulation among CD3+CD4+ cells can be considered as a predictor of the course of concussion in the acute period. However, T cells involved in autoimmunity, do not necessarily reflect the immune system disorders. It is possible that the basis for the decrease in the Th1 level in the circulatory bed in patients with brain injury is the recruitment of immune cells. An increase in the proportion of Th17 was also detected among T-helpers of central memory patrolling the lymphoid tissue the other day after the brain injury. This circumstance may indicate the fact that in the early stages after the nervous tissue damage, processes leading to the formation of «pro-inflammatory» cells are triggered. It allows us to consider these lymphocytes as one of the main populations of immunocompetent cells possessing a neuro-destructive effect.

Circulatory condition in kidney patients with purulent pyelonephritis

Relevance. Urinary tract infections are among the most common infectiousdiseases encountered in the practice of doctors of various specialties, both at the outpatient and hospital stages. In recent years, there has been an increase in the incidence of acute pyelonephritis. The management of patients with acute complicated pyelonephritis requires further study aimed at optimizing the diagnostic algorithm and treatment methods. Objective. Studying the state of blood circulation in the kidney in patients with purulent pyelonephritis and improving the quality of treatment of these patients by introducing our own developed methodology. Materials and methods. In the Regional clinical hospital (Barnaul city, Russia), in the conditions of the urological department, the author personally examined and operated on 30 patients with purulent pyelonephritis according to his own method with an established diagnosis of purulent pyelonephritis. On the first day, all patients underwent retroperitoneoscopic decapsulation of the kidney on the affected side in combination with regional arterial infusion of alprostadil for 3 days. All patients underwent general clinical examination, multispiral computed tomography (MSCT) of the kidneys with bolus contrast enhancement, duplex scanning of renal vessels, and morphological examination of the material before and after the operation. Results. In all cases, the postoperative period proceeded favorably with a shorter treatment time. On the first day after surgery, patients noted a decrease in the intensity of pain in the area of the affected kidney. When comping the data of MSCT of the kidneys with bolus contrast, obtained in patients before treatment, the disappearance of foci of destruction in the kidney and a pronounced restoration of the previously lost blood flow of the kidney on the side of the lesion in the early stages are determined. Nephrectomy was not performed in any case. Conclusion. Each of the stages of the proposed method for the treatment of acute purulent pyelonephritis is an integral part of the technique as a whole; each stage is necessary to influence its level of the vascular bed and parenchyma in the area of its microabscesses and zones of infection. The method allows to achieve restoration of blood circulation in the kidney with the opening of antibiotics access to the organ parenchyma.

The Impact of Wind on Flow and Sediment Transport over Intertidal Flats

Sediment transport over intertidal flats is driven by a combination of waves, tides, and wind-driven flow. In this study we aimed at identifying and quantifying the interactions between these processes. A five week long dataset consisting of flow velocities, waves, water depths, suspended sediment concentrations, and bed level changes was collected at two locations across a tidal flat in the Wadden Sea (The Netherlands). A momentum balance was evaluated, based on field data, for windy and non-windy conditions. The results show that wind speed and direction have large impacts on the net flow, and that even moderate wind can reverse the tidal flow. A simple analytical tide–wind interaction model shows that the wind-induced reversal can be predicted as a function of tidal flow amplitude and wind forcing. Asymmetries in sediment transport are not only related to the tide–wind interaction, but also to the intratidal asymmetries in sediment concentration. These asymmetries are influenced by wind-induced circulation interacting with the large scale topography. An analysis of the shear stresses induced by waves and currents revealed the relative contributions of local processes (resuspension) and large-scale processes (advection) at different tidal flat elevations.

A Numerical Model for Tsunami-Induced Morphology Change

We describe the development of a time-resolved model for tsunami-induced morphology change, based on an existing Boussinesq model for weakly-dispersive free-surface waves coupled to a depth-integrated model for sediment concentration and an equation for bed level change. The model allows for spatial variability in bottom friction coefficients and accounts for the presence of non-erodible beds or finite depths of available sediment. The model is verified using one laboratory data set and against field observations of morphology change in the Crescent City, CA harbor during the 2011 Tohoku tsunami event. The model is then applied to a hypothetical example illustrating the impact of tsunami inundation on an undeveloped barrier island.

Reservoir sedimentation and estimating dam storage capacity using bathymetry survey: a case study of Abrajit Dam, Upper Blue Nile basin, Ethiopia

This specific study was conducted on the Abrajit reservoir in east Gojjam, Amhara region, Ethiopia. The general objective of the study was to investigate reservoir siltation and determination of the remaining valuable life span of the reservoir using ArcGIS 10.5 version and Golden surfer 16 latest version. A bathymetric survey using echo-sounding equipment (Garmin GPSMAP421s) was conducted and a topo map of reservoir data was used for assessment of the sediment volume. The accumulated sediment volume was estimated by subtracting the triangular interconnected network (TIN) map of the initial bed level from the currently measured bed level. The result of the research revealed that to date, 343,700.1 m3 bulk of sediment was accumulated in the reservoir that reduces 20% of the total reservoir capacity. In the results from the bathymetric investigation and software analysis, annually 28,641.675 m3 year−1 amount of sediment is coming from the catchments to the reservoir that contributed 1.66% of annual reservoir volume reduction. The measured recent storing capacity for the Abrajit Dam was 1,388,870 m3. From a comparison of remaining reservoir storage and annual sediment load, the reservoir will not serve more than 12 years. The estimated specific sediment yield (SSy) was found to be 4733.387 ton km−2 year−1. Therefore, to improve the estimated life span of the reservoir, watershed management is very important and further study is required to identify the area where watershed conservation will focus in the future. Upon the findings, the reservoir volume is running to reduce and it cannot serve all the demand what it designed for during the dry season. As a result, operation curves should be mandatory to give water service for the critical water needs, and regular monitoring of sediment accumulation in the reservoir is recommended.

Experimental Study on the Effect of Thickness and Level of the Collar on the Scour Pattern in 180° Sharp Bend with Bridge Pier

Scouring around the bridge's piers is one of the major causes of serious damage to the bridge pier. A laboratory modelling method has been utilized in this research to study the effect of level and thickness of collar on scouring around the pier. The experiments were carried out in a channel with a 180° bend and a relative curvature radius equal to 2. This channel is composed by the straight upstream- and downstream-directed paths, respectively, 6.5 and 5.1 m long and 1 m wide. All experiments were conducted with a constant discharge capacity equal to 0.07 m3⁄s. The obtained results indicated that the installation of the collar at the initial bed surface and 0.4 pier width under the initial bed level with thickness of 0.12 and 0.06 pier width helped gain the best results in reducing the amount of scouring when placing the pier at 90° of the bend. It also decreased 70% of the maximum depth of the scour hole in comparison with when the collar was not implemented. In the positions of 60° and 120°, the thickness parameter has no appreciable effect on scouring, and the best level of collar in this positions is same as the pier located at 90° of bend.

Sediment Morphology and the Flow Velocity Field in a Gully Pot: An Experimental Study

Urban runoff (re)mobilises solids present on the street surface and transport them to urban drainage systems. The solids reduce the hydraulic capacity of the drainage system due to sedimentation and on the quality of receiving water bodies due to discharges via outfalls and combined sewer overflows (CSOs) of solids and associated pollutants. To reduce these impacts, gully pots, the entry points of the drainage system, are typically equipped with a sand trap, which acts as a small settling tank to remove suspended solids. This study presents data obtained using Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) measurements in a scale 1:1 gully to quantify the relation between parameters such as the gully pot geometry, discharge, sand trap depth, and sediment bed level on the flow field and subsequently the settling and erosion processes. The results show that the dynamics of the morphology of the sediment bed influences the flow pattern and the removal efficiency in a significant manner, prohibiting the conceptualization of a gully pot as a completely mixed reactor. Resuspension is initiated by the combination of both high turbulent fluctuations and high mean flow, which is present when a substantial bed level is present. In case of low bed levels, the overlaying water protects the sediment bed from erosion.