Pressure, leakage and energy management in water distribution systems

A fast and efficient method to calculate time schedules for internal and boundary PRVs and flow modulation curves has been developed and implemented. Both time and flow modulation can be applied to a single inlet DMA. The time modulation methodology is based on solving a nonlinear programming problem (NLP). In addition, Genetic Algorithms (GA) has been proposed and investigated to calculate the optimal coefficients of a second order relationship between the flow and the outlet pressure for a PRV to minimize the background leakage. The obtained curve can be subsequently implemented using a flow modulation controller in a feedback control scheme. The Aquai-Mod® is a hydraulic device to control and modulate the outlet pressure of a PRV according to the valve flow. The controller was experimentally tested to assess its performance and functionality in different conditions and operating ranges. The mathematical model of the controller has been developed and solved, in both steady state and dynamic conditions. The results of the model have been compared with the experimental data and showed a good agreement in the magnitude and trends. A new method for combined energy and pressure management via integration and coordination of pump scheduling with pressure control aspects has been created. The method is based on formulating and solving an optimisation NLP problem and involves pressure dependent leakage. The cost function of the optimisation problem represents the total cost of water treatment and pumping energy. Developed network scheduling algorithm consists of two stages. The first stage involves solving a continuous problem, where operation of each pump is described by continuous variable. Subsequently, the second stage continuous pump schedules are discretised using heuristic algorithm. Another area of research has been developing optimal feedback rules using GA to control the operation of pump stations. Each pump station has a rule described by two water levels in a downstream reservoir and a value of pump speed for each tariff period. The lower and upper water switching levels of the downstream reservoir correspond to the pump being “ON” or “OFF”. The achieved similar energy cost per 1 Ml of pumped water. In the considered case study, the optimal feedback rules had advantage of small number of ON/OFF switches, which increase the pump stations lifetime and reduce the maintenance cost as well

The Accuracy Degree of CFD Turbulence Models for Butterfly Valve Flow Coefficient Prediction

Abstract Although engineers are mainly interested in the prediction of mean flow behavior, the turbulence cannot be ignored, because the fluctuations give rise to the extra Reynolds stresses on the mean flow. These extra stresses must be modeled in commercial CFD by selecting convenient turbulence model. The flow inside the control valve is complex and the control valves performance is precisely evaluated by determining the valve coefficient named, flow coefficient. Hence, aim of the present study is to investigate the effect of turbulence model type on the solution accuracy for the valve disk angles 40° and 60° as well as to implement the degree of agreement between experimental and numerical results. The numerical verification has been investigated by FLUENT 6.3 and the valve is meshed by GAMBIT 2. The mesh independent test has been carried out only by standard k-ε to evaluate the mesh effectiveness and attain the best accuracy. Among from these several turbulence models which have been studied here are standard k-ε, realized k-ε, k-ω, and RSM. Butterfly valve, STC model and (DN 50) diameter is chosen to be the test specimen in this research. The results showed that, there is no general turbulent model that can deal successfully with all cases. Numerical and experimental results are in general in good agreement, however are different in details, and showed that, RSM model is the most efficient numerical solver when applied to butterfly valve flow coefficient evaluation. For the future, a significant amount of work still needs to be undertaken in experimental unsteady butterfly valve flow analysis with RSM numerical model

Combined Energy and Pressure Management in Water Distribution Systems

In this paper a method is proposed for combined energy and pressure management via integration and coordination of pump scheduling with pressure control aspects. The proposed solution involves: formulation of an optimisation problem with the cost function being the total cost of water treatment and pumps energy usage, utilisation of an hydraulic model of the network with pressure dependent leakage, and inclusion of a PRV model with the PRV set-points included as a set of decision variables. Such problem formulation led to the optimizer attempting to reduce both energy usage and leakage. The developed algorithm has been integrated into a modelling, simulation and optimisation environment called FINESSE. The case study selected is a major water supply network, being part of Yorkshire Water Services, with a total average demand of 400 l/s

Scenario-based sustainable water management and urban regeneration

Copyright © ICE PublishingDeployable output (source availability) from water resources in north west England is predicted to decrease over the next 25 years. Alternative supply management strategies are planned to help avoid a deficit in the supply–demand balance within the region but have yet to be considered in detail. This paper assesses the contribution of such an alternative supply strategy at local level on the water resource supply–demand balance at regional level based on a proposed urban regeneration site in north west England. Various water conservation and reuse measures are investigated considering local and regional conditions and constraints. Four future scenarios are presented and used to describe how the future might be (rather than how it will be), to allow an assessment to be made of how current ‘sustainable solutions’ might cope whatever the future holds. The analysis determines the solution contributions under each future and indicates that some strategies will deliver their full intended benefits under scenarios least expected but most needed. It is recommended that to help reduce the regional supply–demand deficit and maximise system resilience to future change, a wide range of water demand management measures should be incorporated on this and other sites

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Mathematical modelling of a hydraulic controller for PRV flow modulation.

The main purpose of this paper is to describe a new experimental setup for testing static and dynamic behav-iour of the AQUAI-MOD® hydraulic controller coupled with a standard PRV, as well as to develop mathe-matical models which represent static and dynamic properties of such a system. The controller has been ex-perimentally tested to assess its performance in different conditions and operating ranges. The device in all cases has showed good performance by modulating the outlet pressure as expected between two points corre-sponding to the minimum and the maximum flow. The mathematical models of the controller have been im-plemented and solved using the Mathematical software package to represent both steady state and dynamics conditions. The results of the steady state model have been compared with experimental data and showed a good agreement in the magnitude and trends. The steady state model can be used to simulate the behaviour of a PRV and the AQUAI-MOD® hydraulic controller in typical network applications. It can be also used at the design stage and to compute the required adjustments for the minimum and maximum head set points before installing the controller in the field. Subsequently, a dynamic model of the PRV and the AQUAI-MOD® hy-draulic controller system has been developed and solved. Again the dynamic model showed a good agreement with the experimental data. The main time constant in the system model corresponds to the movement of the main element of the PRV. The research presented here has been carried out within the Neptune project (www.neptune.ac.uk) which is a Strategic Partnership between EPSRC, ABB, Yorkshire Water and United Utilities

Optimal pump scheduling with pressure control aspects: case studies

In this paper a method for combined energy and pressure management via integration of pump scheduling with pressure control aspects is described and applied to a medium scale water supply network. The method is based on formulating and solving an optimisation problem and involves utilisation of an hydraulic model of the network with pressure dependent leakage and inclusion of a PRV model with the PRV set-points included in a set of decision variables. Such problem formulation led to the optimizer attempting to reduce both energy usage and leakage. Case study considered revealed potential for substantial saving in electrical energy cost using the proposed method. This research is sponsored by and is a part of EPSRC Neptune project www.neptune.ac.uk). The authors are grateful to Ridwan Patel of Yorkshire Water Services for providing the data used in this paper