■ Water Supply System Management
Water supply system is an essential infrastructures for human life. The main purpose of water supply system is to supply adequate quantity of fresh water with sufficient pressure. Therefore the design and analysis of water supply systems are very important. Water supply system generally includes drainage basins, raw water collection points, water purification facilities, water storage facilities, water pressurizing components and distribution pipes. Hydrosystems laboratory has been studying on the Design and Analysis of water distribution networks (WDNs) in ‘Design and Construction of Smart DMA in Water Distribution Networks’ project supported by the Ministry of Environment, Korea. WDN, one of the parts in the water supply system, consists of reservoirs, tanks, pipes, pumps, valves and demand areas.
■ Related Research Project
(Design and Construction of Smart DMA in Water Distribution Networks)
● Optimal Design of Water Distribution Networks
In terms of WDNs design, many studies have been carried out in the last three decades to solve least-cost design problems using optimization techniques (Linear Programming, Non-Linear Programming, Meta-heuristic Techniques, etc.). They considered least-cost as well as other design parameters (eg. energy saving, robustness) in the optimal design of water supply network.
In other words, this research develops a multi-objective optimal design model for water distribution networks considering many objectives (e.g., cost, reliability, CO2 emission, and surplus head, etc.). In WDN design process, our research focuses on the determination of pipe size while satisfying hydraulic constraints.
● Analysis Technique for Water Distribution Networks under Abnormal Conditions
In terms of WDNs analysis, hydraulic analysis model of WDN can be served as a useful tool for checking water quantity, pressure, and quality of the systems. A WDN analysis model is developed by using a link-node formulation governed by two conservation laws: conservations of mass and energy. Two hydraulic analysis approaches are available for WDNs; demand-driven analysis (DDA) and pressure-driven analysis (PDA). In DDA, it is assumed that nodal demand is fully supplied regardless of nodal pressure, which is mainly suitable for normal operating conditions. However, in abnormal conditions, such as pipe failures or unexpected increase in demand, the DDA approach could result in unrealistic results (e.g., negative pressure). To address the shortcomings of DDA, PDA has been considered in a number of studies. However, head-outflow relation (HOR) should be defined for PDA, which is system-specific and uncertain.
In this project, Hydrosystems laboratory developed two softwares (Opti-HSNet, SB-PDA).
■ Research Achievements
Opti-HSNet is a multi-objective optimal design software for water distribution networks capable of considering up to four objectives (i.e., cost, reliability, CO2 emission, and surplus head).
In the developed software, Harmony Search Algorithm is used as the optimization technique. In the optimization process, design objectives are minimized / maximized as the objective functions. Design objectives are to minimize cost, maximize reliability, minimize CO2 emission, and maximum surplus head while satisfying hydraulic constraints on nodal pressure and pipe flow velocity. Pipe diameters are to be determined from the optimization.. The developed software was demonstrated through the design of many real WDNs considering two objectives at a time (e.g., cost and reliability, cost and surplus head, CO2 emission and reliability, CO2 emission and surplus head) . It was confirmed that the resultant designs are better than current design with respect to the two design objectives considered. Therefore, a cost-effective WDN design with high reliability/sustainability can be obtained by using Opti-HSNet. Hydrosystems laboratory hosted the public demonstration and workshop of Opti-HSNet for engineers in 2015.
SB-PDA is a hydraulic analysis models for WDNs considering uncertainty in parameters of HOR at the demand nodes using Monte Carlo simulation.
Under pipe break condition, here comes the segment to repair the broken spot depending on the location of adjacent valve. Thus, SB-PDA increased the suitability and effectiveness of analysis results considering these segment factors. In addition, it can quantify the impact of uncertain HOR on the WDN hydraulic calculation.
The developed PDA model was applied to real WDNs and the results showed that the proposed model is superior to other existing models when analyzing abnormal conditions. Hydrosystems laboratory took out a patent on SB-PDA in Korea. Hydrosystems laboratory hosted a public demonstration and workshop of SB-PDA for engineers in 2015.