Yang X.,University of Minnesota |
Sotiropoulos F.,University of Minnesota |
Conzemius R.J.,WindLogics Inc. |
Wachtler J.N.,Barr Engineering Co. |
Strong M.B.,Barr Engineering Co.
Wind Energy | Year: 2014
A large-eddy simulation framework, dubbed as the Virtual Wind Simulator (VWiS), for simulating turbulent flow over wind turbines and wind farms in complex terrain is developed and validated. The wind turbines are parameterized using the actuator line model. The complex terrain is represented by the curvilinear immersed boundary method. The predictive capability of the present method is evaluated by simulating two available wind tunnel experimental cases: the flow over a stand-alone turbine and an aligned wind turbine array. Systematic grid refinement studies are carried out, for both single turbine and multi-turbine array cases, and the accuracy of the computed results is assessed through detailed comparisons with wind tunnel experiments. The model is further applied to simulate the flow over an operational utility-scale wind farm. The inflow velocities for this case are interpolated from a mesoscale simulation using a Weather Research and Forecasting (WRF) model with and without adding synthetic turbulence to the WRF-computed velocity fields. Improvements on power predictions are obtained when synthetic turbulence is added at the inlet. Finally the VWiS is applied to simulate a yet undeveloped wind farm at a complex terrain site where wind resource measurements have already been obtained. Good agreement with field measurements is obtained in terms of the time-averaged streamwise velocity profiles. To demonstrate the ability of the model to simulate the interactions of terrain-induced turbulence with wind turbines, eight hypothetical turbines are placed in this area. The computed extracted power underscores the significant effect of site-specific topography on turbine performance. © 2014 John Wiley & Sons, Ltd.
Edmonds D.A.,Boston College |
Paola C.,University of Minnesota |
Hoyal D.C.J.D.,ExxonMobil |
Sheets B.A.,Barr Engineering Co.
Journal of Geophysical Research: Earth Surface | Year: 2011
Densely populated river deltas are losing land at an alarming rate and to successfully restore these environments we must understand the details of their morphology. Toward this end we present a set of five metrics that describe delta morphology: (1) the fractal dimension, (2) the distribution of island sizes, (3) the nearest-edge distance, (4) a synthetic distribution of sediment fluxes at the shoreline, and (5) the nourishment area. The nearest-edge distance is the shortest distance to channelized or unchannelized water from a given location on the delta and is analogous to the inverse of drainage density in tributary networks. The nourishment area is the downstream delta area supplied by the sediment coming through a given channel cross section and is analogous to catchment area in tributary networks. As a first step, we apply these metrics to four relatively simple, fluvially dominated delta networks. For all these deltas, the average nearest-edge distances are remarkably constant moving down delta suggesting that the network organizes itself to maintain a consistent distance to the nearest channel. Nourishment area distributions can be predicted from a river mouth bar model of delta growth, and also scale with the width of the channel and with the length of the longest channel, analogous to Hack's law for drainage basins. The four delta channel networks are fractal, but power laws and scale invariance appear to be less pervasive than in tributary networks. Thus, deltas may occupy an advantageous middle ground between complete similarity and complete dissimilarity, where morphologic differences indicate different behavior. Copyright 2011 by the American Geophysical Union.
Walker R.E.D.,University of Minnesota |
Walker R.E.D.,Barr Engineering Co. |
Pastor J.,University of Minnesota |
Dewey B.W.,University of Minnesota
Ecosystems | Year: 2010
Microbial immobilization of nitrogen (N) in litter from one year's production may cause oscillations in biomass production if it delays N availability the following year. We tested whether shoot and root litter and plant density affect biomass and seed production of populations of wild rice (Zizannia palustris L.) grown in 378 l stock tank mesocosms over four consecutive years. Half the tanks were thinned to a uniform seedling density whereas density in the remaining tanks was allowed to fluctuate ad libitum. Litter treatments included both shoot litter removal, leaving only root litter, and retaining shoot litter intact with root litter. A separate greenhouse fertilizer experiment tested whether N and/or phosphorus (P) limited productivity. Responses to N additions were much stronger than to P additions. Annual production and N availability in the tanks were correlated with each other and followed a concurrent cycle from 2004 to 2008. Furthermore, production in tanks with shoot + root litter did not fluctuate more than tanks with only root litter. Root litter immobilized more nitrogen and for a longer period than shoot litter. Neither litter immobilized P. Density did not affect mean seed weight, total seed production, or mean plant weight, but total seed production declined in years following productive years and was high only following years of low litter production. Root litter may therefore be primarily responsible for the delays in N availability that cause cycles in biomass and seed production. Consequently, both wild rice litter quantity and quality play central roles in production and population dynamics of wild rice stands. © 2010 Springer Science+Business Media, LLC.
Howard A.,Barr Engineering Co. |
Mohseni O.,Barr Engineering Co. |
Gulliver J.,University of Minnesota |
Stefan H.,University of Minnesota
Water Research | Year: 2011
Standard sumps (manholes) provide a location for pipe junctions and maintenance access in stormwater drainage systems. Standard sumps can also remove sand and silt particles from stormwater, but have a high propensity for washout of the collected sediment. With appropriate maintenance these sumps may qualify as a stormwater best management practice (BMP) device for the removal of suspended sediment from stormwater runoff. To decrease the maintenance frequency and prevent standard sumps from becoming a source of suspended sediment under high flow conditions, a porous baffle, named the SAFL Baffle, has been designed and tested as a retrofit to the sump. Multiple configurations with varying percent open area and different angles of attack were evaluated in scale models. An optimum configuration was then constructed at the prototype scale and evaluated for both removal efficiency and washout. Results obtained with the retrofit indicate that with the right baffle dimensions and porosity, sediment washout from the sump at high flow rates can be almost eliminated, and removal efficiency can be significantly increased at low flow rates. Removal efficiency and washout functions have been developed for standard sumps retrofitted with the SAFL Baffle. The results of this research provide a new, versatile stormwater treatment device and implemented new washout and removal efficiency testing procedures that will improve research and development of stormwater treatment devices. © 2011 Elsevier Ltd.
Yavno S.,Trent University |
Fox M.G.,Trent University |
Vila-Gispert A.,University of Girona |
Bhagat Y.,Barr Engineering Co.
Environmental Biology of Fishes | Year: 2013
Adaptive strategies in morphology can significantly influence the successful invasion and establishment of non-native species. Since its introduction, the pumpkinseed (Lepomis gibbosus), a sunfish of North American origin, has spread throughout most of Europe, including the Iberian Peninsula. We hypothesized that 12 morphological traits, functionally significant for locomotion, would differ according to geographic origin (native/non-native) and habitat type (fluvial/lacustrine). Using flow-through raceways, we simultaneously reared F1 young-of-the-year pumpkinseed from two native and two non-native populations, produced from adults kept in a common environment. Morphometric measurements were recorded at the beginning and end of the 90-day rearing period. Median-fin size and placement differed significantly between native and non-native populations, whereas paired fin size differed between fluvial and lacustrine populations. Other functionally significant traits, such as body width, also differed between native and non-native populations. Spanish populations were considered to have acquired these adaptive external morphologies through successive generations, following the species' range expansion through the variable environments of the Iberian Peninsula. © 2012 Springer Science+Business Media B.V.
Huser B.J.,Swedish University of Agricultural Sciences |
Pilgrim K.M.,Barr Engineering Co.
Water Research | Year: 2014
The conversion of mobile phosphorus (P) to aluminum bound P (Al-P) after addition of Al to over 300 sub-samples from 35 sediment cores collected from 20 lakes in the upper Midwest, United States was investigated in this study. Consistent relationships between mobile P reduction and Al-P formation were detected across a broad range of mobile sediment P contents (0.04-2.8gPm-2cm-1 or 0.083-2.8mgPg-1DW) and lake types. The conversion of mobile P to Al-P was dependent on the initial mobile sediment P content and the amount of Al added to the sediment. An empirical model was then developed to predict the formation of Al-P based on the amount of Al added relative to the initial mass of mobile P in the sediment. The results were compared to sediment collected from an Al treated lake and good agreement was found between the model and in-situ changes to sediment P fractions caused by Al treatment. The model developed in this study, unlike previous models with extreme, singular endpoints, allows for a continuum of estimates for mobile P conversion to Al-P, along with efficiency of P binding by Al, as Al dose varies. Model results can be used in conjunction with mobile sediment P based predictions for internal P loading to calculate an Al dose required to meet internal phosphorus loading goals for lake management and restoration without the need for expensive, time consuming Al additions to sediment. © 2014 Elsevier Ltd.
Bridson-Pateman E.,Barr Engineering Co. |
Jamieson R.,Dalhousie University |
Lake C.,Dalhousie University
Geotextiles and Geomembranes | Year: 2016
Wastewater stabilization ponds (WSPs) are common for wastewater treatment in remote Canadian Arctic communities. In this paper, two geotextiles of different mass/unit areas are examined as a potential biofiltration upgrade to existing WSPs in arctic summer conditions. The intended role of the geotextile is to provide additional treatment of municipal wastewater seeping from these WSPs. Column filtration experiments were performed using municipal wastewater in a controlled laboratory environment at either 10 °C or 2 °C. The columns contained one of two different nonwoven geotextiles over 10 cm of gravel, simulating a WSP berm in contact with exfiltrating wastewater. Weekly wastewater samples were taken upstream and downstream of the geotextile/gravel filter and were analyzed for a suite of water quality parameters; the hydraulic conductivity of the columns was also measured weekly. Results showed that it is possible to accumulate biomass on geotextile material over a 3 month period at these temperatures, which corresponded with 1–2 log reductions in hydraulic conductivity. Significant removal of total suspended solids, 5-day biochemical oxygen demand, total nitrogen, and total phosphorus was observed; however, removal efficiencies for most parameters were reduced at the lower temperature. This study demonstrates that geotextiles could be used to enhance the performance of WSP systems operating in arctic climates. © 2016 Elsevier Ltd
Kowalsky N.,Barr Engineering Co.
NPRA Environmental Conference Papers | Year: 2011
Since the summer of 2009, petroleum refineries have been diligently working to achieve and maintain compliance with EPA's Greenhouse Gas Mandatory Reporting Rule (MRR), codified in 40 CFR Part 98. The MRR requires both environmental and instrumentation staff to be familiar with fuel- and process-flow meters, including GC in laboratories or online. A discussion on the instrumentation and analytical requirements in Subparts A, C, and Y of the MRR covers the initial flow-meter calibration requirements; ongoing flow-meter calibration requirements; pressure- and temperature-correction requirements; analytical measurements for carbon content, molecular weight, and higher heating values; and estimated accuracy and technical basis for the estimate. This is an abstract of a paper presented at the NPRA Environmental Conference 2011 (New Orleans, LA 10/24-25/2011).
Trinkle J.,Barr Engineering Co.
American Fuel and Petrochemical Manufacturers, AFPM - Environmental Conference 2012 | Year: 2012
Notwithstanding the subsequent removal of the stipulations for pollution control and prevention projects and for clean units, the New Source Review (NSR) Reform rules offered existing petroleum refineries a number of options to streamline the applicability determination process, e.g., accepting a plantwide applicability limitation (PAL) or to refine the emissions increase from project-affected existing units by using the new definitions of baseline actual emissions, projected actual emissions and, as applicable, replacement units. It is generally accepted that the use of the NSR Reform provisions at petroleum refineries and petrochemical facilities has not been as widespread as originally expected, especially the PAL program. The retrospective benefits and risks of both using the refined emissions calculation test methodologies and applying for a PAL are discussed. This is an abstract of a paper presented at the 2012 Environmental Conference (Denver, CO 10/14-16/2012).
Kowalsky N.,Barr Engineering Co.
American Fuel and Petrochemical Manufacturers, AFPM - Environmental Conference 2012 | Year: 2012
dP flow meters are most common in refinery fuel gas service, however at times, other instrumentation technologies, e.g., vortex or Corolis meters, are used in fuel flow applications. These alternative meter technologies are referred to as "all-in-one" meters due to the fact that a single instrument measures flow with an output reading for volumetric flow rate as compared to many additional measurements and calculations needed to obtain the same volumetric flow data for a dP meter. A discussion covers the variables that impact dP flow measurement accuracy and proper estimation of accuracy; a strategic approach to better understand installed accuracy and to provide a cradle-to-grave approach for improving the installed measurement accuracy using a refinery case study as an example; the cradle-to-grave approach for improving accuracy; and a case study, illustrating the cradle to grave approach. This is an abstract of a paper presented at the 2012 Environmental Conference (Denver, CO 10/14-16/2012).