Ketefian G.S.,Resource Management Associates |
Gross E.S.,Resource Management Associates |
Gross E.S.,University of California at Davis |
Stelling G.S.,Stelling Hydraulics
International Journal for Numerical Methods in Fluids | Year: 2016
Summary: A new numerical method for particle tracking (Lagrangian particle advection) on 2-D unstructured grids with triangular cells is presented and tested. This method combines key attributes of published methods, including streamline closure for steady flows and local mass conservation (uniformity preservation). The subgrid-scale velocity reconstruction is linear, and this linear velocity field is integrated analytically to obtain particle trajectories. A complete analytic solution to the 2-D system of ordinary differential equations (ODEs) governing particle trajectories within a grid cell is provided. The analytic solution to the linear system of locally mass-conserving constraints that must be enforced to obtain the coefficients in the ODEs is also provided. Numerical experiments are performed to demonstrate that the new method has substantial advantages in accuracy over previously published methods and that it does not suffer from unphysical particle clustering. The method can be used not only in particle-tracking applications but also as part of a semi-Lagrangian advection scheme. John Wiley & Sons, Ltd.
Kimmerer W.J.,San Francisco State University |
Gross E.S.,Resource Management Associates |
MacWilliams M.L.,Delta odeling Associates
Limnology and Oceanography | Year: 2014
We used hydrodynamic and particle-tracking models to investigate vertical movement of plankton and resulting retention in the San Francisco Estuary. The hydrodynamic model was UnTRIM, a three-dimensional, unstructured grid model, which had been calibrated to historical conditions in this estuary for 1994-1997, a period of widely varying hydrology. Intensive field studies of hydrodynamics and vertical movements of organisms during 1994-1996 provided input data for the models. The particle-tracking model was run with 14 alternative behaviors for three 45 d periods of contrasting hydrology. The behaviors included passive behavior, several simple tidal migration patterns, and several sinking speeds. Vertical positions of migrating and sinking particles resembled those seen in the field studies for copepods and epibenthos, respectively. Passive particles were advected from the estuary at rates that depended on freshwater flow. All of the non-passive behaviors caused retention of the particles in the low-salinity region of the estuary under some flow conditions. Tidal migration was very effective at maintaining position, but model results and a re-examination of the field data suggested that migration speed should increase with increasing freshwater flow. Continuous sinking was also effective at retention, particularly in deep areas of low tidal velocity. We conclude that the vertical distributions observed in the field studies were a result of active patterns of movement, that these patterns can result in retention, and that retention in a bathymetrically complex estuary can be understood only in the context of the full time-varying three-dimensional flow field. © 2014, by the Association for the Sciences of Limnology and Oceanography, Inc.
Foell W.,Resource Management Associates |
Pachauri S.,International Institute For Applied Systems Analysis |
Spreng D.,ETH Zurich |
Zerriffi H.,University of British Columbia
Energy Policy | Year: 2011
A major energy challenge of the 21st century is the health and welfare of 2.7 billion people worldwide, who currently rely on burning biomass in traditional household cooking systems. This Special Issue on Clean Cooking Fuels and Technologies in Developing Economies builds upon an IAEE workshop on this subject, held in Istanbul in 2008 (Foell et al., 2008). It includes several papers from that workshop plus papers commissioned afterwards. The major themes of that workshop and this Special Issue are: Analytical and decision frameworks for analysis and policy development for clean cooking fuels. Making energy provisioning a central component of development strategies. Strategies/business models of suppliers of modern fuels and technologies. Analysis of successes/failures of past policies and programs to improve access to clean cooking.This introductory paper serves as a preamble to the 11 papers in this Special Issue. It provides a brief background on household cooking fuels and technologies, including: (1) their implications for sustainable development, health and welfare, gender impacts, and environment/climate issues; (2) options and scenarios for improved household cooling systems; and (3) discussions of institutions, programs and markets. It closes with "Research and Action Agendas", initially developed during the 2008 workshop. © 2011 Elsevier Ltd.
Hickey J.T.,U.S. Army |
Newbold S.J.,Resource Management Associates |
Warner A.T.,North Park University
River Research and Applications | Year: 2015
The Regime Prescription Tool (RPT) is a software program designed to help groups of scientists, engineers, and water managers access hydrologic data and draft flow recommendations while formulating different ways to manage rivers. It is a communications tool and contributes in the early stages of planning by formalizing ideas and expert knowledge into a structure easily visualized and considered in more detailed analytical tools. Applying RPT helps organize and focus group conversations that seek to create consensus-based alternatives for water management. This paper introduces the software and its role in water resources planning. An RPT application used in the definition of environmental flows for the McKenzie River, Oregon, USA, is presented. © 2014 John Wiley & Sons, Ltd.
Andrews S.W.,Resource Management Associates |
Gross E.S.,Resource Management Associates |
Hutton P.H.,Metropolitan Water District of Southern California
San Francisco Estuary and Watershed Science | Year: 2016
We applied a water balance model to predict tidally averaged (subtidal) flows through the Old River and Middle River corridor in the Sacramento-San Joaquin Delta. We reviewed the dynamics that govern subtidal flows and water levels and adopted a simplified representation. In this water balance approach, we estimated ungaged flows as linear functions of known (or specified) flows. We assumed that subtidal storage within the control volume varies because of fortnightly variation in subtidal water level, Delta inflow, and barometric pressure. The water balance model effectively predicts subtidal flows and approaches the accuracy of a 1-D Delta hydrodynamic model. We explore the potential to improve the approach by representing more complex dynamics and identify possible future improvements. © 2016 by the article author(s).
Kokubu Y.,Tokyo University of Marine Science and Technology |
Yamazaki H.,Tokyo University of Marine Science and Technology |
Nagai T.,Tokyo University of Marine Science and Technology |
Gross E.S.,Resource Management Associates
Continental Shelf Research | Year: 2013
In this study, turbulence and mixing are investigated in a constricted channel at the mouth of Tokyo Bay, using two instruments: a microstructure profiler, TurboMAP-L, and an ADCP. We observed three different stratified conditions, i.e., SSC (Strongly Stratified Condition), MSC (Moderately Stratified Condition) and WSC (Weakly Stratified Condition) over a complete tidal period. The water exchange at the mouth of Tokyo Bay was in the transitional regime between the hydraulic and the diffusive limit with SSC and MSC close to the hydraulic limit and WSC close to the diffusive limit. For SSC and MSC, the enhancement of the stratification and vertical mixing showed asymmetry over a semidiurnal tide cycle. Mixing was stronger during ebb than during flood for SSC. On the other hand, mixing was elevated during flood for MSC. For WSC, weak stratification and strong mixing occurred during both flood and ebb. The SSC asymmetry resembled the strongly stratified condition of Columbia River (Kay and Jay, 2003a, 2003b), and the MSC asymmetry resembled the Strain-Induced Periodic Stratification condition (Simpson et al., 1990). A principle component analysis applied to the observed velocity profiles showed that both barotropic and baroclinic flow played a role during SSC and MSC, and in turn, barotropic flow dominated during WSC. The probability density function of the turbulent kinetic energy dissipation rate is practically expressed as a single lognormal population for all three conditions. © 2013 Elsevier Ltd.