Dennis A. Lyn

Experimental study of a bimolecular reaction in Poiseuille Flow

A bimolecular chemical reaction (reactantl + reactant2 → products) in laminar Poiseuille flow is experimentally observed using a spectrophotometer. The reaction rate (rm) follows the second-order rate law; that is, rm = кC1C2, where cm(m=1, 2) are the reactant concentrations. The reaction rate constant к is independently estimated by monitoring the reaction kinetics in a completely mixed batch reactor using the stopped-flow technique. In the reactive transport experiments, the reactants are introduced in a tube and are initially separated by a sharp interface. The variation of the fluid velocity over the cross section of the tube causes the concentrations of the reactants to vary around their cross-sectional average values (c¯m). These spatial variations in the concentrations (c′m) influence the overall reaction rate. The cross-sectional average reaction rate is given by , where is the segregation intensity. The experimentally observed breakthrough concentration of the product is in agreement with a numerical model that accounts for the effects of the segregation intensity. On ignoring the influence of the segregation intensity, the predicted product concentration substantially exceeds the experimental observations. This shows that for initially non-overlapping reactants the segregation intensity is negative (s < 0) and that the overall chemical transformation rate in flowing systems can be significantly different from that implied by substituting the mean concentrations in the expression for the reaction rate.

Debris Accumulation at Bridge Crossings: Laboratory and Field Studies

Extensive accumulation of large woody debris at bridge piers poses a chronic and sometimes quite severe problem at several bridge crossings in Indiana. This study, involving both laboratory and field components, examines the factors contributing to the initiation and development of such debris piles. The laboratory study, performed in a rectangular channel with a single model pier (and in some cases with an upstream vertical cylinder modeling a debris deflector, as well as a model sand bar) and both dowels and twigs as model logs, considered the effects of velocity and depth. The experiments point to a stronger than might be expected effect of local depth, with the potential for debris accumulation generally greater when the local depth is smaller. The field study consisted of video monitoring and recording of debris-transporting events at two sites, the SR59 south crossing of the Eel River (in operation since 9/2001), and the SR63 southbound bridge over the Big Vermillion River (in operation since 4/2003). Results (images) during significant flow events have only been obtained at the SR59 site during the 2001/2002 season, and some qualitative conclusions can be drawn regarding the initiation and growth of debris piles in relation to significant flow events.

A FIELD STUDY OF SCOUR-MONITORING DEVICES FOR INDIANA STREAMS

The Indiana Department of Transportation (INDOT) is considering the deployment of fixed scour-monitoring instrumentation as part of a systematic response to the problem of scour around bridge piers. Within a larger study of the efficacy of and the problems to be encountered with such instrumentation, a project was undertaken in which two different types of scour monitoring devices were installed on piers at two different sites near Purdue University. The two devices, one based on a magnetic collar on a rod driven into the streambed, the other based on a sonar or acoustic principle, were developed with funding by the Federal Highway Administration and National Cooperative Highway Research Program, and their use is being actively promoted by these agencies. This report is divided into three main sections. First, in Chapter 2, the devices are described and their principles of operation are briefly outlined. Deviations from the standard configuration are highlighted. In Chapter 3, the installation procedure followed is described, and a report of the important events during the course of the field component of the project is given generally. The procedure for downloading the field data collected is briefly dealt with, together with a description of the format of the data collected. A sample of the data so far obtained forms the basis of the discussion in Chapter 4 of the performance of the scour monitoring devices. The important conclusions gained from the field study as well as the questions still open are summarized in Chapter 5. The devices do show promise as being effective for continuously monitoring the local scour around a bridge pier. The long-term survivability of the monitors in the Indiana stream environment, where woody debris is prevalent with no countermeasures taken, remains still to be proven.

A Laboratory Study of Bendway Weirs as a Bank Erosion Countermeasure

AbstractBendway weirs are linear structures similar to spurs but designed to be overtopped by typical streamflows, and have recently attracted attention as an environmentally sensitive means of protecting the outer banks of stream bends. A laboratory study was conducted to examine the effectiveness of these type of structures, constructed following FHWA (U.S. Federal Highway Administration) design-manual guidelines, in protecting the outer bank of a 90° bend in a narrow channel with both erodible bed and banks. Experiments were performed at a single nominal (initial) depth, and so characterized by a single (initial) ratio of radius of curvature to top width of 3.3, with and without a field of five weirs. Measurements of erodible boundary elevations as well as the magnitudes of the time-averaged point horizontal velocities at various cross sections were taken. Although a definite overall deflective effect by the weirs was observed, the outer bank remained susceptible to significant erosion even in the pres...

Application of Relevance Vector Machine for Sediment Transport Estimation

Estimation of sediment concentrations in streams and rivers is important for water resources management and projects. Sediment concentration is generally determined from direct measurements, or estimated from sediment transport equations that require detailed information about the flow and sediment characteristics. However, there is often a large discrepancy between these models and observations. The complexity of sediment transport processes presents an opportunity for the application of alternate methods. As a fairly recent computing tool, relevance vector machines (RVMs) are gaining popularity in the fields of machine learning and pattern recognition. The objective of this study is to develop an RVM approach for estimation of sediment concentrations. The resulting RVM model is then trained and tested on a large data set and the performance of the RVM approach is compared with more conventional transport formulae.

Final Control Volume Analysis

The tenure of an editor is, from a variety of viewpoints, mercifully limited. With high hopes and prodigious plans begun, the editorship soon becomes immersed in a rising tide of submissions requiring reviews and decisions in a timely manner. Toward the end of the tenure, a clearer, more balanced view emerges, motivating this stocktaking or control volume analysis, as it were, on the flow of manuscripts. The transition to an Internet-based system of submission/ review/publication was undoubtedly the major milestone defining the last four years. As the first large monthly ASCE journal to dip our toes in digital waters, we contributed our share to working out the bugs of the system. Improvements can still be made, and innovations will be added, but very few, if any, in the hydraulic research community are nostalgic for paper-based submissions. The greater degree of security, transparency, accountability, even convenience, is welcome; but the problem of overly long reviews remains resistant. In an increasingly fragmented and competitive research publishing environment emphasizing citation metrics with real consequences for research careers, the appropriate balance between review time and review quality needs to be struck. While review time can be readily quantified, a corresponding metric of review quality is not available. Even so, a positive correlation between review time and review quality may be as weak or nonexistent? , particularly beyond a certain time, as any found in sediment transport or hydrology. Some relevant data and statistics for the 40-month period 1 May 2006 to 28 Aug. 2009, covering the period of operation of the Internet system, which allows convenient compilation of such data are given in Table 1. As is often the case with flow problems, data are limited, and a stationary state may not have been established, but the analysis may still be of interest. Over 1,200 manuscripts were handled, corresponding to an inflow manuscript velocity of 1 ms/day with final decisions accept or reject, or withdrawn rendered on 74%, the remainder being at various stages of the review process. The globalization of the authorship is seen in that only 25% of the submissions originate in North America, and only about a third from English-speaking countries. The latter has particular repercussions because poor English usage or, more broadly speaking, poor presentation, can adversely affect the evaluation of a manuscript, or unduly prolong the review process. Almost 4,400 reviews were solicited, but only 3,000 reviews were submitted by over 1,000 different reviewers. Finding good reviewers and maintaining uniformly high standards continue to present challenges to the editorial board. Interestingly, once a reviewer has agreed to perform a review, the average time taken for the review is only 50 days. The contributions of all reviewers should be acknowledged, but those of Giuseppe Oliveto, Nian-Sheng Cheng, Brett Sanders, and Jochen Aberle, who each performed 12 or more reviews including rereviews during the 40-month period, merit special mention.

Evaluation of Scour and Stream Stability by Using CAESAR

The performance of an expert system (CAESAR for Catalog and Expert Evaluation of Scour Risk and River Stability) for an initial evaluation of scour and stream stability was assessed. Three alternative scour indices are used to compare with the evaluation results of CAESAR. These scour indices include the Observed Streambed Scour Index, the Indiana Department of Transportation (INDOT) Potential Streambed Scour Index, and the Simon Potential Streambed Scour Index. Ten bridges in Indiana are selected for evaluation in this study. The scour indices and the field inspection information required by CAESAR are retrieved from the U.S. Geological Survey data base. In general, the results show that CAESAR is able to reflect current scour risks as well as the Observed Streambed Scour Index, and the results from CAESAR identify more bridges as scour critical than the INDOT Potential Streambed Scour Index and the Simon Potential Streambed Scour Index. Because the INDOT Potential Streambed Scour Index and the Simon Potential Streambed Scour Index do not take into account the overall stream geometry, bank materials, channel and floodplain widths, and other considerations required by CAESAR, the results of these two indices are not as conservative as those given by CAESAR. It is concluded that the results from CAESAR may be used to estimate the scour risk of bridge piers.

A Truck-Mounted Scour Inspection System for INDOT

Scour monitoring may be a useful tool for the Indiana Department of Transportation (INDOT) in dealing with local scour problems at bridge sites, and a truck-mounted scour-monitoring system is an attractive option offering flexibility in deployment and cost-effectiveness. This report deals with two aspects related to the further development of such a system: i) a web application that combines the latest available information regarding streamflow with relevant information regarding bridges considered susceptible to bridge scour, thereby assisting in truck-deployment decisions, and ii) development of an acoustic positioning system as a replacement of the original mechanical positioning in order to improve the ease of use.The web application, written in Macromedia (now Adobe) Flash 7, provides a graphical (map) display of stream gaging sites and bridges, and the relevant information. The report discusses briefly its use and the software implementation.The acoustic positioning system is based on acoustically measuring distances from transmitters attached to the scour sonar housing to an array of receivers of known fixed positions, and is intended for use in determining reproducibly the position being probed by a scour sonar. Laboratory tests were performed with the system in isolation, and results were compared with locations determined from a Total station. It was found that, under relatively ideal laboratory conditions, the system could locate the transmitters within 1-ft in the horizontal and 1-ft in the vertical. For the more demanding location of a probed point on a hypothetical streambed, the system errors often exceeded this specification. Field tests, undertaken for both stationary-truck and moving-truck applications, but with the positions of transmitters nominally fixed with respect to the receivers, showed that the results were noisier, but appropriate pre-screening and post-processing yielded useful data.

Modeling and Design of an Ultraviolet Water Disinfection System

The goal of this research is to design an ultraviolet (UV) disinfection reactor that will inactivate pathogenic microorganisms present in the wastewater generated during long-term space missions, such that complete reuse (i.e., direct potabilization) can be accomplished. This design must ensure microbial inactivation efficacy, as well as minimize volume, mass, power and maintenance requirements. The means to achieve this design goal is a numerical modeling tool developed in this research, which is based on Computational Fluid Dynamics (CFD), UV radiation intensity field models and microbial inactivation kinetics. The inputs to this numerical model are the desired reactor size and geometry, the inlet velocity and boundary conditions, the UV lamp output power and radiation intensity profile, as well as the characteristics of the aqueous media. The outputs of the model are the UV dose distribution delivered to the microorganisms traversing the reactor and the degree of microbial inactivation achieved. Based on these outputs, the performance of the UV reactor can be assessed for the entire range of practical operating conditions. The validity of the numerical model was assessed with biodosimetry experiments employing Bacillus subtilis spores as the target microorganism and a commercially available UV disinfection reactor. The numerical model is used to investigate alternative UV reactor geometries which can be incorporated into an Advanced Life Support (ALS) water purification system for long-term space missions. The simulation input flow rate is based on the daily water output from six crewmembers and the biomass production chamber, which is included in the ALS closed-loop water system. UV reactor designs are evaluated based on dual criteria: process efficiency expressed as the degree of achieved microbial inactivation, as predicted by the numerical model, and Equivalent System Mass (ESM) values.