Validation of a non-linear reduced hydrodynamic model for curved open-channel flow

River morphodynamics and sediment transportRiver morphology and morphodynamic

Quasi-3D modelling of bed shear stresses at high curvature

Single thread meandering rivers exhibit complex planformpatterns in their floodplains, resulting from a complex interaction between flow, bed and bank morphology. The flow through meander bends may be characterized by primary flow in streamwise direction and secondary flow in transverse direction. The secondary flow plays an important role in the redistribution of streamwise momentum and also affects the bed shear stress, which is important for the shaping of the bed topography. Presently, most depth-averaged morphodynamic models adopt a secondary flow parameterization, based on mild curvature assumptions. This yields a linear relation between curvature and secondary flow strength. However, in strongly curved river bends, the secondary flow strength weakens considerably, due to the non-linear interaction of the streamwise and transverse velocity profiles. This interaction does not only affect the redistribution of streamwise momentum, but it is also important for the direction and magnitude of the bed shear stresses. A non-linear quasi-3D hydrodynamic model (i.e. depth averaged plus 3D parameterizations) is presented and used to simulate two sharply curved flume experiments over a horizontal and fully developed bed. The hydrodynamics results are compared to measurements, a three-dimensional hydrodynamic model, a three-dimensional hydrodynamic model with few layers, a linear hydrodynamic model based on mild curvature assumptions, and a depth-averaged model without secondary flow. The non-linear quasi-3D model results show a qualitatively good agreement with measurements and the three dimensional model. The linear quasi-3D model overestimates the angle between the bed shear stress and the depth averaged velocity direction through the bend. Furthermore the linear model fails to capture the increase of bed shear stress magnitude correctly. The depth-averaged model without secondary flow shows no increase of bed shear stress magnitude and no angle between the bed shear stress and the depth averaged velocity direction. Over the horizontal bed the 3D model with a small number of vertical layers underestimates the bed shear stress angle as well as the increase of bed shear stress magnitude. Over the fully developed bed the 3D model with a small number of vertical layers shows an underestimation of the increase of bed shear stress, but shows good agreement for the bed shear stress angle

Validation of a non-linear reduced hydrodynamic model for curved open-channel flow

The flow through meander bends is inherently three dimensional and may be characterized by primary flow in streamwise direction and secondary flow in transverse direction. Although, three dimensional simulations of meander bends are feasible for laboratory scale experiments, temporal and spatial scales of naturally occurring meandering rivers are much larger than those found in laboratory experiments. Therefore, computationally less expensive (reduced) flow models are necessary. Reduced hydrodynamic models are depth-integrated models and therefore require a closure model to resolve the effect of secondary flow. At present, most reduced flow models are linear as they neglect the feedback between the primary and secondary flow, which limits their validity to mild curvature. A non-linear reduced flow model, including this feedback, is compared to experimental data from the laboratory and the field which are both sharply and moderately curved. The model predictions compare well to the global flow structure in the high curvature Kinoshita flume and the moderate curvature Tollense River bend (with extra complicating factors of vegetation and horizontal recirculation zones). A linear model is also used to model the selected cases, showing good agreement for moderate curvature but not for sharp curvature. An analysis of the driving mechanisms reveals the reason for the difference in the model predictions

Processes governing the flow redistribution in sharp river bends

Insight is provided in hydrodynamic processes governing the velocity redistribution in sharp river bends based on simulations of three recent experiments by means of Blanckaert and de Vriend's (2003, 2010) reduced-order nonlinear model without curvature restrictions. This model successfully simulated the flow redistribution and the secondary flow in all three experiments. The results indicate that the flow redistribution is primarily governed by topographic steering, curvature variations and secondary flow, in a broad range of different configurations, including mildly to sharply curved bends, narrow to shallow bends, smooth to rough bends, bends with additional complexities such as horizontal recirculation zones or patches of riverbed vegetation. The relative importance of these three dominant processes is case dependent, and controlled by the parameters Cf −1H/B, R/B and streamwise curvature variations. The first parameter characterizes a river reach, whereas the second and third parameters are characteristics of individual bends. Major differences exist between the hydrodynamic processes in mildly and sharply curved bends. First, velocity redistribution induced by curvature variations is negligible in mildly curved bends, but the dominant process in sharp bends. This result is relevant, because most meander models are based on the assumption of weak-curvature variations. Second, nonlinear hydrodynamic interactions play a dominant role in sharp bends, where mild-curvature models overpredict the secondary flow and in some cases even falsely identify it as the dominant process governing the velocity redistribution, which leads to unsatisfactory flow predictions. The reduction in secondary flow strength provoked by the nonlinear hydrodynamic interactions is accompanied by a reduction in the transverse bed slope, which reduces the effect of topographic steerin

Ethnic disparities in tuberculosis incidence and related factors among indigenous and other communities in ethnically diverse Suriname

Background: In Suriname, a country home to many ethnic groups, a high incidence of tuberculosis (TB) has been found among Indigenous Trio Amerindians. However, whether wider ethnic disparities in TB incidence and its associated risk factors (e.g., diabetes mellitus and HIV) exist in Suriname, is not known. We sought to investigate disparities in TB incidence and its risk factors on ethnicity in Suriname, as this could give way to targeted TB intervention programs. Methods: Anonymized patient data from 2011 to 2015 was extracted from the National TB Registry and analyzed. Differences in the five-year incidence rates of TB for the six largest ethnic groups-Creole, Hindustani, Indigenous, Javanese, Maroon, and Mixed-were assessed using a chi-square goodness-of-fit test, and TB patient differences regarding ethnicity were evaluated for selected factors using a multinomial logistic regression with Creole patients as reference. Results: 662 Patients were eligible for analyses with the following ethnic makeup: Creole (36.4%), Hindustani (15.6%), Indigenous (8.6%), Javanese (10.6%), Maroon (15.1%), and Mixed ethnicity (13.7%). Differences in five-year incidence rates for TB were significant, chi(2)(5, N = 662) = 244.42, p Conclusions: Our study has demonstrated that ethnic disparities in tuberculosis incidence exist in Suriname and that they are associated with specific, known risk factors such as HIV (especially for Creole people). For Indigenous people, risk factors may include diminished access to health care facilities and low socioeconomic status. However, direct data on these factors was unavailable. These findings call for targeted national intervention programs-with special attention given to the vulnerabilities of susceptible ethnic groups-and improved data collection

Anemia in young children living in the Surinamese interior:The influence of age, nutritional status and ethnicity

Purpose: This study investigates the prevalence of anemia in young children living in the interior of Suriname and the influence of the associated factors age, nutritional status and ethnicity. Patients and methods: In this cross-sectional observational study, 606 children aged 1-5 years from three different regions of Suriname's interior were included, and hemoglobin levels and anthropometric measurements were collected. Logistic regression models were computed to examine independent associations between anemic and nonanemic groups and to measure the influence of age, nutritional status and ethnicity. Results: A total of 606 children were included, of whom 330 (55%) were aged 1-3 years and 276 were aged 4-5 years. The overall prevalence of anemia was 63%. Younger age was associated with anemia (odds ratio [OR]= 1.78; 95% confidence interval [CI]: 1.27-2.51). Anemia was less prevalent in Amerindian than in Maroon children (OR=0.51; 95% CI: 0.34-0.76). Hemoglobin level was not influenced by nutritional status nor by sex. Conclusion: The prevalence of anemia in children aged 1-5 years living in Suriname's interior is high (63%) compared to that in similar aged children in Latin America and the Caribbean (4-45%). Children aged 1-3 years were more affected than those aged 4-5 years as were Maroon children compared to Amerindian children. Nutritional status and sex were not of influence

Research on eco-hydro-morphological river processes by combining field investigations, physical modeling and numerical simulations

Hydrodynamical, morphodynamical and ecological river processes and their multiple linkages occur in an infinity of different configurations and over a wide range of spatial and temporal scales. This paper illustrates a research methodology that consists in combining field investigations, physical modeling in the laboratory, and numerical simulations in order to develop generic insight and tools for engineering and management of the river environment. This combined methodology is illustrated in research on (i) the macroscale characteristics of the velocity distribution and their relation to long-term and large-scale planimetric river processes, (ii) the flow field in the vicinity of the river bank and its importance with respect to bank erosion and, (iii) linkages between the characteristics of the mean flow and the turbulence on the one hand, and the behavior of invertebrates on the other. The reported research strongly relies on the use of state-of-the-art measuring instruments as well as numerical techniques

Patterns of recurrence in the randomised PORTEC-3 trial of chemoradiotherapy for endometrial cancer

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Outcome and Predictors for Mortality in Patients with Cardiogenic Shock:A Dutch Nationwide Registry-Based Study of 75,407 Patients with Acute Coronary Syndrome Treated by PCI

It is important to gain more insight into the cardiogenic shock (CS) population, as currently, little is known on how to improve outcomes. Therefore, we assessed clinical outcome in acute coronary syndrome (ACS) patients treated by percutaneous coronary intervention (PCI) with and without CS at admission. Furthermore, the incidence of CS and predictors for mortality in CS patients were evaluated. The Netherlands Heart Registration (NHR) is a nationwide registry on all cardiac interventions. We used NHR data of ACS patients treated with PCI between 2015 and 2019. Among 75,407 ACS patients treated with PCI, 3028 patients (4.1%) were identified with CS, respectively 4.3%, 3.9%, 3.5%, and 4.3% per year. Factors associated with mortality in CS were age (HR 1.02, 95%CI 1.02-1.03), eGFR (HR 0.98, 95%CI 0.98-0.99), diabetes mellitus (DM) (HR 1.25, 95%CI 1.08-1.45), multivessel disease (HR 1.22, 95%CI 1.06-1.39), prior myocardial infarction (MI) (HR 1.24, 95%CI 1.06-1.45), and out-of-hospital cardiac arrest (OHCA) (HR 1.71, 95%CI 1.50-1.94). In conclusion, in this Dutch nationwide registry-based study of ACS patients treated by PCI, the incidence of CS was 4.1% over the 4-year study period. Predictors for mortality in CS were higher age, renal insufficiency, presence of DM, multivessel disease, prior MI, and OHCA