Flooding and Inundation Modeling in the Great Bay Estuary

As part of this research, FVCOM, a finite-volume coastal ocean numerical hydrodynamic model (Chen, et al., 2003), was implemented into the Great Bay estuary. FVCOM is one of several community models that have been developed for coastal regions, and was selected because it utilizes an unstructured grid to discretize the model domain. The unstructured grid provides the ability to have fine scale resolution near the boundary or coastline and decreased resolution away from the boundary where the flow field is less complicated, resulting in greatly reduced computational expense in less dynamic regions allowing model runs to be completed in much shorter time periods. Grid development also requires that bathymetric data is accurately assigned to grid nodes in such a way that the model itself will be numerically stable. This requires significant development time implementing an appropriate grid mesh (Persson and Strang, 2004) with bathymetry data that has been smoothed to limit inherent numerical noise in the computations. FVCOM was implemented on a grid with finest resolution equaling 30 m, and then tested on a 10 day run with offshore forcing determined analytically by the 8 most energetic semi-diurnal (M2, N2, S2, K2) and diurnal (K1, O1, P1, Q1) tidal constituents at Fort Pt., NH (https://tidesandcurrents.noaa.gov/harcon.html?id=8423898), and including fresh water river fluxes from 6 rivers equivalent to 5 times the average daily discharge (Ward and Bub, 2007). The model was further tested utilizing the 100 year tropical storm event estimated from the North Atlantic Coast Comprehensive Study (NACCS; USACE, 2015), and the highest projected sea level rise scenario for year 2100 estimated by NOAA (http://www.corpsclimate.us/ccaceslcurves.cfm). The numerically stable model indicates that the grid can be used to simulate tidal forcing with maximum projected year storm surge and sea level rise in the Great Bay, and – with further development to include finer (10 m) mesh resolution and inclusion of surface waves and wind forcing – may be able to predict future flooding scenarios based on forecasted storm events and sea level rise

Large water-hammer pressure for column separation in pipelines

Water-hammer pressures in a pipeline due to the collapse of a vapor cavity adjacent to a valve are investigated. A water-hammer event is initiated by the closure of a valve in a simple reservoir-pipeline-valve system. The sequence of events following an instantaneous valve closure leading to the formation and collapse of a vapor cavity and the resultant occurrence of a short-duration pressure pulse are described. Short-duration pressure pulses result from the superposition of the valve-closure water-hammer wave and the wave generated by the collapse of the vapor cavity. The resulting maximum pressure may exceed the Joukowsky pressure generated from the initial valve closure. A series of numerical model analyses exhibiting short-duration pressure pulses are presented. In addition, experimental results supporting the findings of the numerical studies are also presented. Experimental plots of hydraulic grade line versus time exhibit short-duration pressure pulses of different shape and characteristics.Angus R. Simpson and E. Benjamin Wyli

Correcting mean-field approximations for spatially-dependent advection-diffusion-reaction processes

On the microscale, migration, proliferation and death are crucial in the development, homeostasis and repair of an organism; on the macroscale, such effects are important in the sustainability of a population in its environment. Dependent on the relative rates of migration, proliferation and death, spatial heterogeneity may arise within an initially uniform field; this leads to the formation of spatial correlations and can have a negative impact upon population growth. Usually, such effects are neglected in modeling studies and simple phenomenological descriptions, such as the logistic model, are used to model population growth. In this work we outline some methods for analyzing exclusion processes which include agent proliferation, death and motility in two and three spatial dimensions with spatially homogeneous initial conditions. The mean-field description for these types of processes is of logistic form; we show that, under certain parameter conditions, such systems may display large deviations from the mean field, and suggest computationally tractable methods to correct the logistic-type description

Cooper pair correlations and energetic knock-out reactions

Two-nucleon removal (or knock-out) reactions at intermediate energies are a developing tool for both nuclear spectroscopy and for the study of certain nucleon correlations in very exotic and some stable nuclei. We present an overview of these reactions with specific emphasis on the nature of the two-nucleon correlations that can be probed. We outline future possibilities and tests needed to fully establish these sensitivities.Comment: 12 pages, 3 figures: Contribution to the Volume 50 years of Nuclear BCS edited by World Scientifi

Models of collective cell motion for cell populations with different aspect ratio: diffusion, proliferation & travelling waves

Continuum, partial differential equation models are often used to describe the collective motion of cell populations, with various types of motility represented by the choice of diffusion coefficient, and cell proliferation captured by the source terms. Previously, the choice of diffusion coefficient has been largely arbitrary, with the decision to choose a particular linear or nonlinear form generally based on calibration arguments rather than making any physical connection with the underlying individual-level properties of the cell motility mechanism. In this work we provide a new link between individual-level models, which account for important cell properties such as varying cell shape and volume exclusion, and population-level partial differential equation models. We work in an exclusion process framework, considering aligned, elongated cells that may occupy more than one lattice site, in order to represent populations of agents with different sizes. Three different idealisations of the individual-level mechanism are proposed, and these are connected to three different partial differential equations, each with a different diffusion coefficient; one linear, one nonlinear and degenerate and one nonlinear and nondegenerate. We test the ability of these three models to predict the population-level response of a cell spreading problem for both proliferative and nonproliferative cases. We also explore the potential of our models to predict long time travelling wave invasion rates and extend our results to two-dimensional spreading and invasion. Our results show that each model can accurately predict density data for nonproliferative systems, but that only one does so for proliferative systems. Hence great care must be taken to predict density data with varying cell shape

Radiator deployment actuator Patent

Hydraulic actuator design for space deployment of heat radiator

Constituent Loads and Trends in the Upper Illinois River Watershed and Upper White River Basin

Water chemistry can greatly influence the quality of surface waters and affect the ability for streams and rivers to meet their designated use(s). In Arkansas, many streams and rivers were placed on the 2008 303(d) list of impaired water bodies due to excess levels of nutrients, chlorides, sulfates, and sediments (ADEQ, 2008). These constituents continue to be listed as the potential cause for water‐quality impairments through the most recent draft 303(d) list (ADEQ, 2014). The Arkansas Non‐Point Source (NPS) Management Program wants to reduce poll‐ utant loading from the landscape and improve water quality, where funding for projects is targeted to priority watersheds throughout the State

Constituent Load Estimation in the Lower Ouachita-Smackover Watershed

Water quality was monitored at 21 sites in the Lower Ouachita‐Smackover Watershed from 2013 November through 2014 September. The U.S. Geological Survey maintains discharge monitoring stations at two of these sites, Moro Creek (USGS 07362500) and Smackover Creek (USGS 07362100), which were sampled during base flow and storm event conditions, whereas the other sites were only sampled during baseflow. The Arkansas Water Resources Center (AWRC) estimated constituent loads for nitrate‐N (NO₃‐–N), total nitrogen (TN), soluble reactive phosphorus (SRP), total phosphorus (TP) and total suspended solids (TSS) using the U.S. Geological Survey LOADEST software. LOADEST creates regression models between constituent concentrations and discharge, as well as time. The resulting models were applied to daily discharge throughout calendar years 2013 and 2014 to estimate loads. Annual and monthly loads and flow volumes for each site are summarized in this report