Recent Papers on Applied Hydraulics
Content Table
- The role of the flow pattern in wastewater aeration tanks
- Introducing knowledge into learning based on genetic programming
- Effects of different hydraulic models on predicting longitudinal profiles of reactive pollutants in activated sludge reactors
- Reactive tracers reveal hydraulic and control instabilities in full-scale activated sludge plant
- Analysis of a large-scale water supply system of the Byzantine period using modern fluid mechanics
- Modelling of the release of organic compounds from polyethylene pipes to water
- RTD (residence time distribution) predictions in large mechanically aerated lagoons
- Computational fluid dynamics modelling of hydraulics and sedimentation in process reactors during aeration tank settling
- A 3D CFD model analysis of the hydraulics of an outfall structure at a power plant
- Hydraulic considerations in restoring boreal streams
The role of the flow pattern in wastewater aeration tanks
Water Science & Technology—WST Vol 61 No 2 pp 407–414 © IWA Publishing 2010 doi:10.2166/wst.2010.803
M. Gresch, D. Braun and W. Gujer
Swiss Federal Institute of Aquatic Science and Technology, Eawag, Dübendorf 8600, Switzerland
Institute of Environmental Engineering, ETH Zurich, Zurich 8093, Switzerland E-mail: markus.gresch@eawag.ch; willi.gujer@eawag.ch; daniel.braun@stab.baug.ethz.ch
Abstract
Reactor hydraulics is one of the key factors for plant performance and plant control. The residence time distribution is a good but limited indicator of reactor hydraulics. A more detailed view is obtained by direct observations within the reactor. Two different techniques (conservative tracer, reactive tracer) are discussed to detect major anomalies in the flow field of a wastewater aeration tank. Experiments with conservative tracers give valuable information over a very limited period of time making the analysis of the flow field difficult. On the other hand, reactive tracers can be monitored long term which helps identifying the flow pattern provided that a high spatial and temporal resolution of the measurements is applied. Experimental data is used to determine the structure and the parameters of a compartment model that corresponds well with the measurements.
Introducing knowledge into learning based on genetic programming
Journal of Hydroinformatics Vol 11 No 3–4 pp 181–193 © IWA Publishing 2009 doi:10.2166/hydro.2009.041
Vladan Babovic
Faculty of Engineering, National University of Singapore, 1 Engineering Drive 2, 117 576, Singapore E-mail: vladan@nus.edu.sg
Abstract
This work examines various methods for creating empirical equations on the basis of data while taking advantage of knowledge about the problem domain. It is demonstrated that the use of high level concepts aid in evolving equations that are easier to interpret by domain specialists. The application of the approach to real-world problems reveals that the utilization of such concepts results in equations with performance equal or superior to that of human experts. Finally, it is argued that the algorithm is best used as a hypothesis generator assisting scientists in the discovery process.
Effects of different hydraulic models on predicting longitudinal profiles of reactive pollutants in activated sludge reactors
Water Science & Technology—WST Vol 58 No 3 pp 555–561 © IWA Publishing 2008 doi:10.2166/wst.2008.676
P. Zima, J. Makinia, M. Swinarski and K. Czerwionka
Faculty of Civil and Environmental Engineering, Gdansk University of Technology, ul. Narutowicza 11/12, 80-952, Gdansk, Poland E-mail: pzim@pg.gda.pl; jmakinia@pg.gda.pl
Saur Neptun Gda
sk SA, ul. Walowa 46, 80-858, Gdansk, Poland E-mail: mswinars@sng.com.pl
Abstract
This paper presents effects of dispersion on predicting longitudinal ammonia concentration profiles in activated sludge bioreactor located at “Wschod” WWTP in Gdansk. The aim of this study was to use the one-dimensional advection-dispersion Equation (ADE) to simulate the flow conditions (based on the inert tracer concentrations in selected points) and longitudinal profile of reactive pollutant (based on the ammonia concentration profiles in selected points). The simulation results were compared with the predictions obtained using a traditional “tanks-in-series” (TIS) approach, commonly used in designing biological reactors. The use of dispersion coefficient calculated from an empirical formula resulted in substantial differences in the tracer concentration distributions in two sampling points in the bioreactor. Simulations using the one-dimensional ADE and TIS model, with the nitrification rate incorporated as the source term, revealed that the hydraulic model plays a minor role compared to the biochemical transformations in predicting the longitudinal ammonia concentration profiles.
Reactive tracers reveal hydraulic and control instabilities in full-scale activated sludge plant
Water Science & Technology—WST Vol 57 No 7 pp 1001–1007 © IWA Publishing 2008 doi:10.2166/wst.2008.210
W. Gujer
ETH Zürich, Institute of Environmental Engineering and EAWAG, CH-8600, Dübendorf, Switzerland gujer@eawag.ch
Abstract
The hydraulic characteristics of aeration tanks in WWTPs have a major impact on the degradation of pollutants, as well as on the control of the aeration. In particular in long reactors, which are not separated by baffles, hydraulic shortcuts or large scale recirculation can lead to a loss of performance. This work demonstrates that reactive tracers such as ammonium and oxygen can be used to investigate the hydraulics of aeration tanks in detail. With the use of electrochemical sensors it is possible to investigate effects in a broad range of time scales.
In the present case study a slow oscillation of the aeration control loop was investigated. Large scale recirculation in the aeration tank and fast fluctuations of the ammonium concentrations close to the oxygen sensor were identified as the cause of these oscillations. Both, the recirculation as well as the fluctuation of the ammonium have a substantial influence on the performance of the aeration tank and the aeration control loop.
Analysis of a large-scale water supply system of the Byzantine period using modern fluid mechanics
Water Science & Technology: Water Supply Vol 7 No 1 pp 183–190 © IWA Publishing 2007 doi:10.2166/ws.2007.021
B. Haut* and D. Viviers**
*Univ. Libre de Bruxelles, Chem. Engin., Av. F.D. Roosevelt 50, C.P. 165/67, 1050 , Brussels, Belgium (E-mail: bhaut@ulb.ac.be)
**Univ. Libre de Bruxelles, Arch. Res. Centre (CReA), Av. F.D. Roosevelt 50, C.P. 175/01, 1050 , Brussels, Belgium
Abstract
In this paper, the flow of water in several elements of the water supply system of the city of Apamea is simulated. The studied elements were used at the end of the 6th century AD (Byzantine period). These simulations allow for the analysis of the water supply system from a modern point of view, in terms of water flow rate, energy loss, etc. This analysis provides a quantitative description of the water supply system of the city, supplementing the field observations.
Modelling of the release of organic compounds from polyethylene pipes to water
Journal of Water Supply: Research and Technology—AQUA Vol 56 No 6–7 pp 435–443 © IWA Publishing 2007 doi:10.2166/aqua.2007.020
Martin Denberg, Martin Denberg, Erik Arvin and Ole Hassager
Institute of Environment & Resources, Technical University of Denmark, Bygningstorvet, building 115 2800 Kgs, Lyngby, Denmark Tel.: +45 45251574. Fax: +45 45932850; mad@er.dtu.dk
Department of Chemical Engineering, Technical University of Denmark, Produktionstorvet, building 423, 2800 Kgs, Lyngby, Denmark
Abstract
The use of polyethylene pipes in the distribution network causes contamination of the drinking water. The contaminants are a mixture of phenols, quinones, antioxidants and short polyethylene chains that in general have a functional polar oxygen group. With the use of the film-layer theory and a mass balance for a pipe, an equation is derived to compute the outlet concentration from a given pipe. The equation indicates that if the water in a pipe has a turbulent flow, the water becomes significantly more contaminated by the migrants, compared to water with a laminar flow. The maximum concentration of contaminants is predictable, and is equal to the product of the migrants' concentration in the polymer and its partition coefficient at the polymer and water interface. E.g. the maximum obtainable concentration of a stabilizer, as Irganox® 1010, in drinking water exposed to PE pipes used in Denmark is between 0.2 and 0.3 mg/L if no reaction of the added antioxidant has taken place in the pipe extrusion step.
RTD (residence time distribution) predictions in large mechanically aerated lagoons
Water Science & Technology Vol 55 No 11 pp 29–36 © IWA Publishing 2007 doi:10.2166/wst.2007.346
D. Stropky*, K. Pougatch**, P. Nowak**, M. Salcudean**, P. Pagoria***, I. Gartshore** and J. Yuan*
*Process Simulations Ltd. 206-2386 East Mall Vancouver, BC, Canada , V6T 1Z3, Tel: +1-604-822-1490, Fax: +1-604-822-1934, (E-mail: hank@psl.bc.ca, jwyuan@psl.bc.ca)
**Department of Mechanical Engineering, University of British Columbia, 2054-6050 Applied Science Lane Vancouver, BC, Canada , V6T 1Z4, (E-mail: pougatch@mech.ubc.ca, nowak@mech.ubc.ca, msal@interchange.ubc.ca, gshore@interchange.ubc.ca)
***Wastewater Eng. Team, Weyerhaeuser, 32901 Weyerhaeuser Way South, Federal Way, WA, USA , 98003 (E-mail: phil.pagoria@weyerhaeuser.com)
Abstract
Mechanically aerated lagoons (used for wastewater treatment in the pulp and paper industry) are typically very large (>500,000 m3) and have complex three-dimensional fluid flow patterns due to mechanical agitation, sludge accumulation, internal baffling, and confined inlet/outlet flow channels. RTD data is frequently used for evaluation of hydraulic performance. however, obtaining accurate data with traditional dye measurements is a difficult and time-consuming process. Moreover, the mixing impact of factors such as aerator positions, sludge accumulation, and internal baffles would require a significant and costly number of local field measurements. Recent applications of CFD to mechanically aerated lagoons have helped engineers to understand the complex flow interactions. This paper provides a practical method for the evaluation of the hydraulic performance of large mechanically aerated lagoons using CFD. A method, based on random-walk Lagrangian particle tracking, has been developed to significantly shorten the computational time needed to produce RTD curves for these lagoons. Comparison of the particle method with the more conventional scalar transport yields excellent results. These methods allow wastewater engineers to combine their existing knowledge and expertise with the established power of CFD. The results quantify the hydraulic impact of different inlet/outlet configurations, aerator configurations, influent flow rates, and bottom sludge profiles.
Computational fluid dynamics modelling of hydraulics and sedimentation in process reactors during aeration tank settling
Water Science & Technology Vol 53 No 12 pp 257–264 © IWA Publishing 2006 doi:10.2166/wst.2006.428
M.D. Jensen*, P. Ingildsen*, M.R. Rasmussen** and J. Laursen**
*Krüger A/S, Gladsaxevej 363, DK-2860 Søborg, Denmark (E-mail: mdj@kruger.dk; pei@kruger.dk)
**Aalborg University, Department of Civil Engineering, Hydraulics and Coastal Engineering, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark (E-mail: i5mr@civil.aau.dk; i5jl@civil.aau.dk)
Abstract
Aeration tank settling is a control method allowing settling in the process tank during high hydraulic load. The control method is patented. Aeration tank settling has been applied in several waste water treatment plants using the present design of the process tanks. Some process tank designs have shown to be more effective than others. To improve the design of less effective plants, computational fluid dynamics (CFD) modelling of hydraulics and sedimentation has been applied. This paper discusses the results at one particular plant experiencing problems with partly short-circuiting of the inlet and outlet causing a disruption of the sludge blanket at the outlet and thereby reducing the retention of sludge in the process tank. The model has allowed us to establish a clear picture of the problems arising at the plant during aeration tank settling. Secondly, several process tank design changes have been suggested and tested by means of computational fluid dynamics modelling. The most promising design changes have been found and reported.
A 3D CFD model analysis of the hydraulics of an outfall structure at a power plant
Journal of Hydroinformatics 7 (2005) 283-290
Liaqat A. Khan, Edward A. Wicklein and Mizan Rashid
ENSR International, 9521 Willows Road NE, Redmond, WA, 98052, USA
ENSR International, 9521 Willows Road NE, Redmond, WA, 98052, USA
ENSR International, 9521 Willows Road NE, Redmond, WA, 98052, USA
Abstract
A practical application of a three-dimensional (3D) computational fluid dynamics (CFD) model to an outfall structure of a power plant is presented in this paper. The outfall structure, used for discharging 55 m3/s of cooling water to a reservoir, consists of two inflow pipes, two deflectors and a baffle wall. The computational grid, resolving all the geometric features of the outfall structure consists of 350,660 hexahedral cells. The CFD model was run for two configurations of the outfall structure, with and without a baffle wall. The interactions of two high velocity jets with deflectors and baffle wall create complex velocity distribution and circulation patterns. Initially, both the jets bifurcate and then merge as they propagate downstream. At the outlet, the maximum near-surface velocities are not significantly different for the two configurations of the outfall structure. However, when the baffle wall is used the near-bed velocities, responsible for reservoir bed scouring, are approximately 75% smaller.
Hydraulic considerations in restoring boreal streams
Nordic Hydrology 35 (2004) 223-235
Juha Järvelä and Terhi Helmiö
Helsinki University of Technology, Espoo, PO Box 5300, FI-02015 HUT, Finland
Helsinki University of Technology, Espoo, PO Box 5300, FI-02015 HUT, Finland
Abstract
The physical habitat that controls ecosystem functioning is determined by local hydraulics and channel morphology. Hydraulic field studies were conducted in a boreal stream (1) to test the hypothesis that the local hydraulic conditions are determined by cross-sectional geometry and flow resistance in boreal conditions by analysing the relationship between flow velocities, cross-sectional geometry and flow resistance, and (2) to suggest success criteria for the restoration of local hydraulic conditions. Results suggest that, in the case of small channels, cross-sectional geometry and flow resistance are weakly interconnected and influenced by factors such as local roughness elements and channel forms. The study showed that both flow resistance and cross-sectional geometry are vital factors in determining local hydraulics. In stream restoration, a design based on consideration of only one of these two factors is inadequate and may result in a failure to replicate natural hydraulic conditions. Simple success criteria for the restoration of local hydraulics are developed.
