Modeling sediment transport in the York River : final report

Numerical simulation on the formation of an Estuarine Turbidity Maximum (ETM) is a difficult task because of the incomplete knowledge on cohesive sediment transport. For example, it is difficult to well simulate the erosion process when the bed erosion properties are only poorly known. It is also hard to simulate the settling process when the bulk density and size of suspended sediment flocs are changing with the ambient environments. Despite of the difficulties, some processes can be parametricalized, even not perfectly, to make the simulation results close to observed. In this project, we demonstrated the possibility of using a constant erosion rate and the assumption that erosion only occurs at tidal acceleration phases to simulate the formation of turbidity maximums in the York River

Investigation of isolated sand shoals on the inner shelf of Virginia relative to the potential for aggregate mining : report on task 4, possible physical impact of dredging at Sandbridge Shoal of the 1993-1995 U. S. Minerals Management Service - Commonwealth of Virginia Cooperative Project

The Virginia Institute of Marine Science, together with other state agencies, has a continuing interest in preserving the coastline of Virginia, particularly, the Atlantic coastline in the vicinity of the resort city of Virginia Beach. Because a well maintained beach can serve several purposes, e.g., (1) providing public recreational areas, (2) protecting valuable properties that are located near coastline, and (3) reducing the rate of land loss, a great deal of efforts has been devoted to understand the processes that affect the change of shoreline. Among several erosion forces, waves are especially important elements as they can alter the shoreline significantly. To have a beach properly maintained, one may use several approaches, and perhaps use all available approaches in parallel to obtain the best results. In the coastal sector of Virginia Beach, beach nourishment using material from inland borrow pit have been done constantly during last two decades. The ability to find land sources of good beach-quality sand has become more difficult. The sand loss due to both shore normal and longshore transport creates the need to find a reliable source of good quality sand for future supply

Investigation of isolated sand shoals on the inner shelf of Virginia relative to the potential for aggregate mining : report on study of possible wave force alternations on the proposed dredging at Sandbridge Shoal, VA

The Virginia Institute of Marine Science, together with other state agencies, has a continuing interest in preserving the coastline of Virginia, particularly, the Atlantic coastline in the vicinity of the resort city of Virginia Beach. Because a well maintained beach can serve several purposes , e.g., ( 1) providing public recreational areas, (2) protecting valuable properties that are located near coastline , and (3) reducing the rate of land loss, a great deal of efforts has been devoted to understand the processes that affect the change of shoreline. Among several erosion forces , waves are especially important elements as they can alter the shoreline significantly. One may use any of several approaches to maintain a beach properly, and perhaps may use all available approaches in parallel to obtain the best results. In the coastal sector of Virginia Beach, beach nourishment using_material from inland borrow pits has been done constantly during the last two decades . It has become more difficult to find land sources of good beach-quality sand . Sand loss from the beach due to both shore normal and longshore transport creates the need to find a reliable source of good quality sand for future use. Sandbridge Shoal ( Fig. 1) located approximately 20 miles south of Virginia Beach and 3 miles offshore , has been identified as a potential source of good beach-quality sand (Kimball and Dame , 1989). Use of the sand resources there, however, causes a great deal of concern that dredging may result in severe beach erosion at Sandbridge due to alternation of the wave transformation process

Measurements of the Shape of Sand Ripples

Laboratory experiments have been conductef. for determining what would be the correct selection of acoustic devices for measuring the shape of sand ripples. The results reveal that a toneburst type signal generator with I or 2 watts will be sufficient to drive the transducer. A transducer with focus and reasonable size would be the best choice. While measuring, the ratio of measuring distance (between the transducer and sea floor) and the transducer\u27s focus length should be maintained at a ratio between 90% and II 0% for best results

Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

Background Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI 2 SD above the median). Findings From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesity. Funding UK Medical Research Council, UK Research and Innovation (Research England), UK Research and Innovation (Innovate UK), and European Union

Comparisons of Different Instruments for Measuring Suspended Cohesive Sediment Concentrations

Laboratory experiments were conducted to compare the performances of four different instruments for measuring suspended cohesive sediment concentrations (SSCs). Among these instruments, two were different models of optical backscatter sensor (i.e., OBS3+ and OBS5+), one was an acoustic Doppler velocimeter (MicroADV), and the last was a laser infrared optical sensor developed at Hohai University, China (HHU-LIOS). Sediments collected from the Yangtze River Estuary and a commercially available kaolinite were selected to check the responses of these four instruments. They were placed in an aqueous solution, and the SSCs were changed within a range from about 10 mg/L to 30 g/L to demonstrate the effective measuring ranges for each instrument. For the kaolinite suspension, the results showed that the HHU-LIOS has a much larger linear response range (0.1 to 13 g/L) when compared with other devices (the MicroADV: 0.1 to 1.35 g/L; the OBS3+: 0.1 to 5 g/L; and the OBS5+: 0.1 to 1 g/L). For the sediment sample from the Yangtze River Estuary, the results showed that the HHU-LIOS has a much wider usable range (from 0.1 to 25 g/L), compared with those for the others. It also showed that a combination of using a HHU-LIOS for the quadratic increasing range up to 25 g/L and the OBS5+ for the clear decreasing output are able to measure the SSCs of the estuarine mud up to 50 g/L

Lattice Boltzmann simulations of three-dimensional incompressible flows in a four-sided lid driven cavity

Abstract Numerical study on three-dimensional (3D), incompressible, four-sided lid (FSL) driven cavity flows has been conducted to show the effects of the transverse aspect ratio, K, on the flow field by using a multiple relaxation time lattice Boltzmann equation. The top wall is driven from left to right, the left wall is moved downward, whereas the right wall is driven upward, and the bottom wall is moved from right to left, all the four moving walls have the same speed and the others boundaries are fixed. Numerical computations are performed for several Reynolds numbers for laminar flows, up to 1000, with various transverse aspect ratios. The flow can reach a steady state and the flow pattern is symmetric with respect to the two cavity diagonals (i.e., the center of the cavity). At Reynolds number?=?300, the flow structures of the 3D FSL cavity flow at steady state with various transverse aspect ratio, i.e., 3, 2, 1, 0.75, 0.5 and 0.25 only show the unstable symmetrical flow pattern. The stable asymmetrical flow pattern could be reproduced only by increasing the Reynolds number that is above a critical value which is dependent on the aspect ratio. It is found that an aspect ratio of more than 5 is needed to reproduce flow patterns, both symmetric and asymmetric flows, simulated by using 2D numerical models