Publications

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Event Detection Systems (EDS) performance is hindered by false alarms that cause unnecessary resource expenditure by the utility and undermine confidence in the EDS operation. Changes in water quality due to operational changes in the utility hydraulics can cause a significant number of false alarms. These changes may occur daily and each instance produces similar changes in the multivariate water quality pattern. Recognizing that patterns of water quality change must be identified, we adapt trajectory clustering as a means of classifying these multivariate patterns. We develop a general approach for dealing with changes in utility operations that impact water quality. This approach uses historical data water quality data from the utility to identify recurring patterns and retains those patterns in a library that can be accessed during online operation. We have implemented this pattern matching capability within CANARY and describe several example applications that demonstrate a decrease in false alarms. ©2009 ASCE.

Investigation of turbulent mixing in pipe joints has been a topic of recent research interest. These investigations have relied on experimental results with downstream sensors to determine the bulk characteristics of mixing in pipe joints. High fidelity computational fluid dynamics models have also been employed to examine the fine scale physics of the mixing within the joint geometry. To date, high resolution imaging of experimental conditions within the pipe joint has not been reported. Here, we introduce high speed photography as a tool to accomplish this goal. Cross joints with four pipes coming together in a single junction are the focus of this investigation. All pipes entering the junction are the same diameter and made of clear PVC. The cross joint was milled from clear acrylic material to allow for high resolution imaging of the mixing processes within the joint. Two pipes carry water into the joint, one with clear water and the other inlet with water containing dye and a salt tracer. Two outlet pipes are carry water away from the joint. A high-speed digital camera was used to image mixing within the joint at an imaging rate of 30 Hz. Each grey-scale (8-bit) image is 1280 x 1024 pixels in a roughly 17.8 x 14.5 cm image containing the cross joint. The pixel size is approximately 0.13 x 0.14 mm. Four experiments using the clear cross-joint have been visualized. The Reynolds number (Re) for the tracer inlet pipe is held constant at 1500, while a different Re in the clear inlet pipe is used for each experiment. The Re value in the outlets are held equal to each other at the average Re of the inlets. Re values in the clear inlet pipe values are: 500, 1000, 2000 and 5000. Visual examination of the images provides information on the mixing behavior including tracer transport along the walls of the pipe, transient variation in the amount of tracer entering each outlet, the sharpness of the clear-tracer interface and variation in the concentration of the tracer throughout the joint geometry. A sharp tracer-clear interface is visible for the clear inlet Re values of 500, 1000 and 2000, but decays to a broad gradual transition zone at a clear inlet Re of 5000. There are no visible instabilities in the clear-tracer interface at the lowest clear water Re (500), but regular periodic instabilities occur for the Re=1000 experiment and these become irregular, but still periodic at clear inlet Re = 2000 and then lose all regular structure in the Re = 5000 experiment. High speed photography applied to clear pipe joints with the necessary image processing can provide qualitative and quantitative insights into mixing processes. A limitation of this approach is that it provides two-dimensional images of a three-dimensional process. ©ASCE 2009.

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This report summarizes the experimental and modeling effort undertaken to understand solute mixing in a water distribution network conducted during the last year of a 3-year project. The experimental effort involves measurement of extent of mixing within different configurations of pipe networks, measurement of dynamic mixing in a single mixing tank, and measurement of dynamic solute mixing in a combined network-tank configuration. High resolution analysis of turbulence mixing is carried out via high speed photography as well as 3D finite-volume based Large Eddy Simulation turbulence models. Macroscopic mixing rules based on flow momentum balance are also explored, and in some cases, implemented in EPANET. A new version EPANET code was developed to yield better mixing predictions. The impact of a storage tank on pipe mixing in a combined pipe-tank network during diurnal fill-and-drain cycles is assessed. Preliminary comparison between dynamic pilot data and EPANET-BAM is also reported.

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While connectivity is an important aspect of heterogeneous media, methods to measure and simulate connectivity are limited. For this study, we use natural aquifer analogs developed through lidar imagery to track the importance of connectivity on dispersion characteristics. A 221.8 cm by 50 cm section of a braided sand and gravel deposit of the Ceja Formation in Bernalillo County, New Mexico is selected for the study. The use of two-point (SISIM) and multipoint (Snesim and Filtersim) stochastic simulation methods are then compared based on their ability to replicate dispersion characteristics using the aquifer analog. Detailed particle tracking simulations are used to explore the streamline-based connectivity that is preserved using each method. Connectivity analysis suggests a strong relationship between the length distribution of sand and gravel facies along streamlines and dispersion characteristics.

This paper investigates the use of strip transect sampling to estimate object abundance when the underlying spatial distribution is assumed to be Poisson. A design-rather than model-based approach to estimation is investigated through computer simulation, with both homogeneous and non-homogeneous fields representing individual realizations of spatial point processes being considered. Of particular interest are the effects of changing the number of transects and transect width (or alternatively, coverage percent or fraction) on the quality of the estimate. A specific application to the characterization of unexploded ordnance (UXO) in the subsurface at former military firing ranges is discussed. The results may be extended to the investigation of outcrop characteristics as well as subsurface geological features. © 2008 Springer-Verlag Berlin Heidelberg.

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To protect drinking water systems, a contamination warning system can use in-line sensors to detect accidental and deliberate contamination. Currently, detection of an incident occurs when data from a single station detects an anomaly. This paper considers the possibility of combining data from multiple locations to reduce false alarms and help determine the contaminant's injection source and time. If we consider the location and time of individual detections as points resulting from a random space-time point process, we can use Kulldorff's scan test to find statistically significant clusters of detections. Using EPANET, we simulate a contaminant moving through a water network and detect significant clusters of events. We show these significant clusters can distinguish true events from random false alarms and the clusters help identify the time and source of the contaminant. Fusion results show reduced errors with only 25% more sensors needed over a nonfusion approach. © 2008 ASCE.

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