Imperial College London

DrIvanStoianov

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 6035ivan.stoianov Website

 
 
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Assistant

 

Miss Judith Barritt +44 (0)20 7594 5967

 
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Location

 

408Skempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

63 results found

Abraham E, Stoianov I, 2015, Efficient preconditioned iterative methods for hydraulic simulation of large scale water distribution networks, 13th International Conference on Computing and Control for the Water Industry, CCWI2015, Publisher: Elsevier: Creative Commons Attribution Non-Commercial No-Derivatives License, ISSN: 1877-7058

Conference paper

Wright R, Herrera M, Parpas P, Stoianov Iet al., 2015, Hydraulic resilience index for the critical link analysis of multi-feed water distribution networks, Computing and Control for the Water Industry (CCWI2015)- Sharing the Best Practice in Water Management, Publisher: ELSEVIER SCIENCE BV, Pages: 1249-1258, ISSN: 1877-7058

Conference paper

Wright R, Parpas P, Stoianov I, 2015, Experimental investigation of resilience and pressure management in water distribution networks, Computing and Control for the Water Industry (CCWI2015)- Sharing the Best Practice in Water Management, Publisher: ELSEVIER SCIENCE BV, Pages: 643-652, ISSN: 1877-7058

Conference paper

Wright R, Stoianov I, Parpas P, Henderson K, King Jet al., 2014, Adaptive Water Distribution Networks with Dynamically Reconfigurable Topology, Journal of Hydroinformatics

This paper presents a novel concept of adaptive water distribution networks withdynamically reconfigurable topology for optimal pressure control, leakage management and improved system resilience. The implementation of District Meter Areas (DMAs) has greatly assisted water utilities in reducing leakage. DMAs segregate water networks into small areas; the flow in and out of each area is monitored and thresholds are derived from the minimum night flow to trigger the leak localisation. A major drawback of the DMA approach is the reduced redundancy in network connectivity which has a severe impact on network resilience, incident management and water quality deterioration. The presented approach for adaptively reconfigurable networks integrates the benefits of DMAs for managing leakage with the advantages of large scale looped networks for increased redundancy in connectivity, reliability and resilience. Self-powered multi-function network controllers are designed and integrated with novel telemetry tools for high-speed time-time synchronised monitoring of the dynamic hydraulic conditions. A robust and computationally efficient optimization method based on sequential convex programming is developed and applied for the dynamic and adaptive reconfiguration of water distribution networks. An investigation is carried out using an operational network to evaluate the benefits of the proposed method for dynamically configurable water supply networks.

Journal article

Aisopou A, Stoianov I, Graham N, Karney Bet al., 2013, Analytical and experimental investigation of chlorine decay in water supply systems under unsteady hydraulic conditions, Journal of Hydroinformatics

This paper investigates the impact of the dynamic hydraulic conditions on the kinetics of chlorine decay in water supply systems. A simulation framework has been developed for the scale-adaptive hydraulic and chlorine decay modelling under steady and unsteady state flows. An unsteady decay coefficient is defined which depends upon the absolute value of shear stress and the rate of change of shear stress for quasi-unsteady and unsteady-state flows. By coupling novel instrumentation technologies for continuous hydraulic monitoring and water quality sensors for in-pipe water quality sensing a pioneering experimental and analytical investigation was carried out in a water transmission main. The results were used to model monochloramine decay and these demonstrate that the dynamic hydraulic conditions have a significant impact on water quality deterioration. The spatial and temporal resolution of experimental data provides new insights for the near real-time modelling and management of water quality as well as highlighting the uncertainty and challenges of accurately modelling the loss of disinfectant in water supply networks.

Journal article

Hoskins A, Stoianov I, 2013, InfraSense: a distributed system for the continuous analysis of hydraulic transients, Computing and Control for the Water Industry (CCWI 2013), Publisher: Elsevier

This paper describes a novel approach for the continuous monitoring and analysis of the dynamic hydraulic conditions in water transmission and distribution systems. The developed InfraSense data logging and management technology extracts static and dynamic indicators which characterise the occurrence of hydraulic instabilities and unsteady-state flows. Computationally e fficient embedded algorithms are described to adaptively derive thresholds for the detection of transient events. A novel algorithm for the representation and classification of transient events in a distributed sensing environment is presented (a stroke-based transient descriptor). One hundred InfraSense systems are currently deployed to facilitate the most thorough investigation to date of the occurrence of hydraulic transients in water supply systems.

Conference paper

Stoianov I, Aisopou A, 2013, Chlorine Decay under Steady and Unsteady-State Hydraulic Conditions, Computing and Control for the Water Industry (CCWI 2013), Publisher: Elsevier

This paper describes a simulation framework for the scale-adaptive hydraulic and chlorine decay modelling under steady and unsteady-state flows. Bulk flow and pipe wall reaction coefficients are replaced with steady and unsteady-state reactioncoefficients. An unsteady decay coefficient is defined which depends upon the absolute value of shear stress and the rate of change of shear stress for quasi-unsteady and unsteady-state flows. A preliminary experimental and analytical investigation was carried out in a water transmission main. The results were used to model monochloramine decay and these demonstrate that the dynamic hydraulic conditions have a significant impact on water quality deterioration and the rapid loss of disinfectant residual.

Conference paper

Wright R, Stoianov I, Parpas P, 2013, Dynamic topology in water distribution networks, Computing and Control for the Water Industry (CCWI 2013), Publisher: Elsevier

A new approach for the operational management of water distribution networks is herein presented, which introduces district metered areas (DMA) with dynamic topology. The approach facilitates the operation of an open and adaptive network thatreverts back to the original DMA structure only at night for leakage detection purposes, therefore eliminating the disadvantages of a closed network structure such as reduced resilience to failure and suboptimal pressure management. The concept and technology have been implemented on a water distribution network in the UK, and a novel optimization method used for its control has been derived that is fast and reliable.

Conference paper

Dicken J, Mitcheson PD, Stoianov I, Yeatman EMet al., 2012, Power-Extraction Circuits for Piezoelectric Energy Harvesters in Miniature and Low-Power Applications, IEEE Transactions on Power Electronics, Vol: 27, Pages: 4514-4529, ISSN: 0885-8993

Journal article

Aisopou A, Stoianov I, Graham NJD, 2012, In-pipe Water Quality Monitoring in Water Supply Systems under Steady and Unsteady State Flow Conditions: A Quantitative Assessment, Water Research, Vol: 46, Pages: 235-246, ISSN: 0043-1354

Monitoring the quality of drinking water from the treatment plant to the consumers tap is critical to ensure compliance with national standards and/or WHO guideline levels. There are a number of processes and factors affecting the water quality during transmission and distribution which are little understood. A significant obstacle for gaining a detailed knowledge of various physical and chemical processes and the effect of the hydraulic conditions on the water quality deterioration within water supply systems is the lack of reliable and low-cost (both capital and O & M) water quality sensors for continuous monitoring. This paper has two objectives. The first one is to present a detailed evaluation of the performance of a novel in-pipe multi-parameter sensor probe for reagent- and membrane-free continuous water quality monitoring in water supply systems. The second objective is to describe the results from experimental research which was conducted to acquire continuous water quality and high-frequency hydraulic data for the quantitative assessment of the water quality changes occurring under steady and unsteady-state flow conditions. The laboratory and field evaluation of the multi-parameter sensor probe showed that the sensors have a rapid dynamic response, average repeatability and unreliable accuracy. The uncertainties in the sensor data present significant challenges for the analysis and interpretation of the acquired data and their use for water quality modelling, decision support and control in operational systems. Notwithstanding these uncertainties, the unique data sets acquired from transmission and distribution systems demonstrated the deleterious effect of unsteady state flow conditions on various water quality parameters. These studies demonstrate: (i) the significant impact of the unsteady-state hydraulic conditions on the disinfectant residual, turbidity and colour caused by the re-suspension of sediments, scouring of biofilms and tubercles from th

Journal article

Aisopou A, Stoianov I, Arora A, O'Hare D, Graham Net al., 2010, Multi-parameter water quality sensors for water supply systems, 10th International Conference on Computing and Control for the Water Industry, Publisher: CRC PRESS-TAYLOR & FRANCIS GROUP, Pages: 349-355

Conference paper

Aisopou A, Stoianov I, Graham N, 2010, Modelling Discolouration in Water Distribution Systems Caused by Hydraulic Transient Events, Water Distribution Systems Analysis 2010. Proceedings of the 12th International Conference, Publisher: ASCE

The occurrence of hydraulic transients in water transmission and distribution systems and their impact on the deterioration of water quality is a topic which is beginning to attract a significant interest among scientists and system operators. Hydraulic transients are traditionally associated with large scale system failures. However, experimental studies carried out by the authors of this paper demonstrate that the hydraulic conditions are rarely steady‐state and various fast and gradual transient events are frequently occurring due to the operation of pumps, control valves and stochastic demand. Furthermore, an analysis of the shape of acquired turbidity traces and field based experience have illustrated that it is the rate of flow change, represented by the unsteady‐state shear stress, rather than the change in the magnitude of the flow (represented by the steady‐state shear) that is responsible for particle mobilisation from the material layer in the pipe and the resulting discolouration events. Despite their importance, transient flow and the resulting unsteady‐state forces are neglected by existing discolouration models, frequently resulting in incorrect turbidity predictions. This paper describes the development of a 1‐D transient simulation model to describe discolouration caused by hydraulic transient events, by which the turbidity of the water is modelled with a transport equation which is coupled to a comprehensive hydraulic transient model. The hydraulic model estimates the unsteady shear stress generated during the transient using the Vardy Brown equation. A previously proposed approach (Boxall et al. 2001) is used to model the release of the discolouration material from the pipe wall into the flow, due to the excess shear stress applied at the wall. The presented transient discoloration model was assessed using hydraulic and discolouration data provided in the literature. Simulation results of the hydraulic transient model demonstrate that the magnitud

Conference paper

Aisopou A, Stoianov I, Graham N, 2010, Modelling Chlorine Transport under Unsteady‐State Hydraulic Conditions, Water Distribution Systems Analysis 2010, Proceedings of the 12th International Conference, Publisher: ASCE

The occurrence of hydraulic transient events in water supply systems may adversely affect the quality of drinking water. Sudden changes in the flow and pressure may cause sediment and biofilm detachment leading to discoloration and loss of residual chlorine. This paper presents the development and evaluation of a 1‐D model that describes the chlorine transport during steady and unsteady‐state (transient) flow conditions. The main objectives for the model development are accuracy, robustness and computational efficiency as it is intended to be used for operational management. The model was developed by coupling the mass transport equation with a comprehensive hydraulic transient solver which accounts for changes in flow, compressibility and inertia effects. The main contribution has been the inclusion of the unsteady shear stress during transient flow conditions with modelling the chlorine transport. This approach differs from existing 1‐D water quality models which use steady state formulas and which fail to explain sudden changes in residual chlorine. In the model, the unsteady shear stress is determined and its significance to chlorine propagation is evaluated. The value of the unsteady shear stress is used to evaluate the fluctuations of the velocity profile, which are neglected in 1‐D transport modelling. The effect of the transient velocity profile on chlorine decay is taken into account by using a chlorine decay coefficient which varies for steady and unsteady‐state (transient) flows. The validity of the modeling approach is evaluated by benchmarking its performance with a 2‐D transient model which explicitly considers the 2‐D velocity profile.

Conference paper

Ikram W, Stoianov I, Thornhill NF, 2010, Towards a Radio-Controlled Time Synchronized Wireless Sensor Network, IEEE Emerging Technologies and Factory Automation (ETFA 2010), ISSN: 1946-0740

Wireless sensor networks are deployed to monitor real-world phenomena, and are seeing growing demand in commerce and industry. These networks can benefit from time synchronized clocks on distributed nodes. The precision of time synchronization depends on error elimination or reliable estimation of errors associated with synchronization message delays. This paper examines an approach to time synchronize motes using onboard radio-controlled clocks. The advantage will be the minimisation of non-deterministic sources of errors in time synchronization amongst receivers. This approach of synchronization using out-of-band and dedicated time source is aimed to achieve network-wide, scalable, topology-independent, fast-convergent and less application-dependent solutions.

Conference paper

Hoult N, Bennett PJ, Stoianov I, Fidler P, Maksimovic C, Middleton C, Graham N, Soga Ket al., 2009, Wireless Sensor Networks: Creating Smart Infrastructure [Awarded the ICE 2010 Telford Gold Medal], Proceedings of the ICE - Civil Engineering, Vol: 162, Pages: 136-143

The deterioration of civil infrastructure is a significant issue throughout the world. To manage infrastructure in a way that ensures safe and efficient operation, managers and engineers require data about its short- and long-term performance. This paper reports on the trial installations of wireless sensor networks in a suspension bridge, slab bridge, rail tunnel and water supply pipeline. Each installation is introduced in terms of hardware, measured parameters, sensors, sampling regimes and installationand operational challenges. Preliminary results from each system are discussed to illustrate the variety of information that can be made available to managers and engineers, and how this information canbe utilised and presented.

Journal article

Aisopou A, Stoianov I, Arora A, O'Hare D, Graham Net al., 2009, Multi-Parameter Water Quality Sensors for Water Supply Systems, International Conference on Computing and Control for the Water Industry; Integrating Water Systems, Publisher: CRC PRESS-TAYLOR & FRANCIS GROUP, Pages: 349-356

Conference paper

Dicken J, Mitcheson PD, Stoianov I, Yeatman EMet al., 2009, Increased Power Output from Piezoelectric Energy Harvesters by Pre-Biasing, PowerMEMS 2009, Pages: 75-78, ISSN: 2151-3155

This paper presents, for the first time, experimental results demonstrating a new approach to increasing the power output of piezoelectric energy harvesters by applying a bias charge at the beginning of each half cycle of motion. Ultimate power limits of inertial energy harvesters depend only on the device size and nature of the excitation, rather than on the transduction mechanism. However, practical devices generally perform well below the theoretical limit, often because a sufficiently high transducer damping force cannot be achieved. For suchcases, we show that the generator effectiveness is improved by a pre-biasing technique, and present simulationresults with experimental verification. These results show that the effectiveness of the piezoelectric generator isimproved by more than 10 times compared to an optimised purely resistive load. In practice our gains were limited by the voltage breakdown of the components used.

Conference paper

Stoianov I, Maksimovic C, Nachman L, Whittle A, Madden S, Kling Ret al., 2007, Wireless Sensor Network for Monitoring Large Scale Infrastructure Systems in Boston, USA., Data requirements for integrated urban water management, Editors: Fletcher, Deletic, Publisher: Taylor & Francis, ISBN: 9780415453448

The first part of this volume describes general principles for developing a monitoring programme in support of sustainable urban water management. The second part examines in detail the monitoring of individual water cycle components.

Book chapter

Stoianov I, Nachman L, Madden S, Tokmouline Tet al., 2007, PIPENET: A Wireless Sensor Network for Pipeline Monitoring, Information Processing in Sensor Networks: IPSN 2007. 6th International Symposium., Pages: 264-273

US water utilities are faced with mounting operational and maintenance costs as a result of aging pipeline infrastructures. Leaks and ruptures in water supply pipelines and blockages and overflow events in sewer collectors cost millions of dollars a year, and monitoring and repairing this underground infrastructure presents a severe challenge. In this paper, we discuss how wireless sensor networks (WSNs) can increase the spatial and temporal resolution of operational data from pipeline infrastructures and thus address the challenge of near real-time monitoring and eventually control. We focus on the use of WSNs for monitoring large diameter bulk-water transmission pipelines. We outline a system, PipeNet, we have been developing for collecting hydraulic and acoustic/vibration data at high sampling rates as well as algorithms for analyzing this data to detect and locate leaks. Challenges include sampling at high data rates, maintaining aggressive duty cycles, and ensuring tightly time- synchronized data collection, all under a strict power budget. We have carried out an extensive field trial with Boston Water and Sewer Commission in order to evaluate some of the critical components of PipeNet. Along with the results of this preliminary trial, we describe the results of extensive laboratory experiments which are used to evaluate our analysis and data processing solutions. Our prototype deployment has led to the development of a reusable, field-reprogrammable software infrastructure for distributed high-rate signal processing in wireless sensor networks, which we also describe.

Conference paper

Stoianov I, Graham N, Madden S, Odenwald T, Stein Met al., 2007, WaterSense : Integrating Sensor Nets with Enterprise Decision Support, London, International Conference of Computing and Control for the Water Industry; Water Management Challenges in Global Change, Publisher: Taylor & Francis, Pages: 123-130

Conference paper

Aw ES, Stoianov I, Whittle AJ, Germaine JTet al., 2007, A Wireless Remote Monitoring System: Application in the Northeast Corridor Railtrack, The Seventh International Symposium On Field Measurements in Geomechanics, Publisher: American Society of Civil Engineers, Pages: 1115-1124, ISSN: 0895-0563

Conference paper

Stoianov I, Nachman L, Whittle A, Madden S, Kling Ret al., 2006, Sensor Networks for Monitoring Water Supply and Sewer Systems: Lessons from Boston, Water Distribution Systems Analysis Symposium 2006,Proceedings of the 8th Annual Water Distribution Systems Analysis Symposium, Publisher: ASCE

In recent years, research in wireless sensor networks (WSN) has been undergoing a quiet revolution, promising to have significant impact on a broad range of applications relating to environmental monitoring, structural health monitoring, security and water safety. The convergence of the Internet, telecommunications, and novel information technologies with techniques for miniaturisation now provides vast opportunities for the development and application of low‐cost monitoring solutions which could drastically increase the spatial and temporal resolution of environmental data. The paper describes the development of a prototype monitoring system which bridges advances in wireless sensor networks with advances in hydraulic and water quality modeling. The prototype monitoring system was deployed at Boston Water and Sewer Commission (BWSC) in December 2004, and it has been successfully collecting and charting near‐real time hydraulic and water quality data as well as data from combined sewer outflows (CSO). The remote monitoring system has unique functionalities in terms of sampling rates (up to 1000 S/s), time synchronization (up to 1 ms) and in‐network processing. These features create novel opportunities for wirelessly collecting data for applications such as hydraulic pressure transients, remote acoustic leak detection together with low‐duty cycle applications such as monitoring water quality parameters and water levels in CSOs. The trial with BWSC has been tremendously useful to prototype hardware and software tools, and to identify deployment and operational challenges in using sensor networks for monitoring and management of large scale water supply systems.

Conference paper

Covas D, Stoianov I, Mano JF, Ramos H, Graham N, Maksimovic Cet al., 2005, The Dynamic Effect of Pipe-Wall Viscoelasticity in Hydraulic Transients. Part II-Model Development, Calibration and Verification, Journal of Hydraulic Research, Vol: 43, Pages: 56-70, ISSN: 0022-1686

A state-of-the-art mathematical model has been developed to calculate hydraulic transients in pressurized polyethylene (PE) pipe systems. This hydraulic transient solver (HTS) incorporates additional terms to take into account unsteady friction and pipe-wall viscoelasticity. Numerical resultsobtained were compared with the classic waterhammer solution and with experimental data collected from a PE pipe-rig at Imperial College (London, UK). Unlike the classical model, the developed HTS is capable of accurately predicting transient pressure fluctuations in PE pipes, as well ascircumferential strains in the pipe-wall. The major challenge was the distinction between frictional and mechanical dynamic effects. First, the HTS was calibrated and tested considering these two effects separately: if only unsteady friction was considered, a major disagreement between collecteddata and numerical results was observed; when only the viscoelastic effect was considered, despite the good agreement between data and numerical results, the calibrated creep function depended on the initial flow rate. In a second stage, the combination of these dynamic effects was analysed: creepwas calibrated for laminar flow and used to test the solver for turbulent conditions, and a good agreement was observed. Finally, the HTS was tested using creep measured in a mechanical test, neglecting unsteady friction, and a good agreement was obtained.

Journal article

Covas D, Stoianov I, Ramos H, Graham N, Maksimovic C, Butler Det al., 2004, Water Hammer in Pressurized Polyethylene Pipes: Conceptual Model and Experimental Analysis, Urban Water Journal, Vol: 1, Pages: 177-197

This paper analyzes the dynamic effects of pipe wall viscoelasticity on hydraulic transients. These effects have been observed in transient data collected from two polyethylene (PE) pipe systems. The first is a 270 m pipeline, 50 mm diameter, at Imperial College London, and the second is the world's longest experimental PE pipeline, 1.3 km long, 110 mm diameter, buried underground at Thames Water Utilities (London, UK). A mathematical model has been developed to calculate hydraulic transients in polyethylene pipe systems based on the assumption that the viscoelastic behaviour of pipe walls is linear. An additional term has been added to the continuity equation to describe the retarded deformation of the pipe wall and the resulting governing equations are solved by the Method of Characteristics. The numerical results are compared with both the classic elastic solution and with collected transient data. Good agreement between numerical results for the viscoelastic solution and observed data was obtained by fitting the creep function J(t). Unlike classic water hammer analysis, the developed mathematical model is capable of accurately predicting transient pressures in polyethylene pipes and the circumferential strains in the pipe walls.

Journal article

Covas D, Stoianov I, Mano J, Ramos H, Graham N, Maksimovic Cet al., 2004, The Dynamic Effect of Pipe Wall Viscoelasticity in Hydraulic Transients – Part I. Experimental Analysis and Creep Characterization, Journal of Hydraulic Research, Vol: 42, Pages: 516-530, ISSN: 0022-1686

The mechanical behaviour of the pipe material determines the pressure response of a fluid system during the occurrence of transient events. In viscoelastic pipes, typically made of polyethylene (PE), maximum or minimum transient pressures are rapidly attenuated and the overall pressure wave is delayed in time. This is a result of the retarded deformation of the pipe-wall. This effect has been observed in transient data collected in ahigh-density PE pipe-rig, at Imperial College (London, UK). Several transient tests were carried out to collect pressure and circumferential strain data. The pipe material presented a typical viscoelastic mechanical behaviour with a sudden pressure drop immediately after the fast valve closure, a major dissipation and dispersion of the pressure wave, and transient mechanical hysteresis. The creep-function of the pipe material was experimentallydetermined by creep tests, and, its order-of-magnitude was estimated based on pressure–strain data collected from the pipe-rig. A good agreement between the creep functions was observed. Creep tests are important for the characterization of the viscoelastic behaviour of PE as a material; however,when PE is integrated in a pipe system, mechanical tests only provide an estimate of the actual mechanical behaviour of the pipe system. This is because creep depends on not only the molecular structure of the material and temperature but also on pipe axial and circumferential constraints andthe stress–time history of the pipe system.

Journal article

Stoianov I, Dellow D, Maksimovic C, Graham Net al., 2003, Field Validation of the Application of Hydraulic Transients for Leak Detection in Transmission Pipelines, International Conference on Computing and Control for the Water Industry, Publisher: Abingdon, Balkema

Conference paper

Stoianov I, Maksimovic C, Graham NJD, 2003, Designing a Continuous Monitoring System for Transmission Pipelines (PIPENET), Abingdon, International Conference on Computing and Control for the Water Industry, Publisher: Abingdon, Balkema

Conference paper

Covas D, Stoianov I, Ramos H, Graham N, Maksimovic Cet al., 2003, Dissipation of Pressure Surges in Water Pipeline Systems, Pumps, Electromechanical Devices and Systems Applied to Urban Water Management (PEDS 2003 IAHR), Publisher: Balkema Publishers, Pages: 711-720

Conference paper

Covas D, Stoianov I, Graham N, Maksimovic C, Ramos H, Butler Det al., 2002, Inverse Transient Analysis for Leakage Detection and System Calibration - A Case Study in a Plastic Pipeline, Fifth International Conference on Hydroinformatics: Software Tools and Management Systems, Publisher: IWA Publishing, Pages: 1154-1160

Conference paper

Stoianov I, Chapra S, Maksimovic C, 2002, A Framework Linking Urban Park Land Use with Pond Water Quality (Hyde Park, London), Urban Water Journal, Vol: 2, Pages: 47-62, ISSN: 1462-0758

Journal article

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