Nelson Carriço

Transient vaporous cavitation in viscoelastic pipes

The research focuses on the analysis of transient cavitating flow in polyethylene pipes, which are characterized by a viscoelastic–rheological behaviour. A hydraulic transient solver incorporating the description of the rheological–mechanical behaviour of these pipes and the cavitating pipe flow has been developed. Both the discrete vapour cavity model and the discrete gas cavity model have been used to describe transient cavitating flow. These assume that discrete air cavities are formed at fixed pipe sections and consider a constant wave speed in the pipe reaches between the cavities. An experimental programme was conducted in a pipe-rig composed of a high-density polyethylene (HDPE) pipeline. Numerical results have been compared with collected data resulting in a good agreement. Effects related to the viscoelasticity of HDPE pipes and to the occurrence of vapour pressures during the transient events are also discussed.

Prioritization of rehabilitation interventions for urban water assets using multiple criteria decision-aid methods.

The aim of this paper is to compare sorting and ranking methods for prioritization of rehabilitation interventions of sewers, taking into account risk, performance and cost. For that purpose multiple criteria decision-aid (MCDA) methods such as ELECTRE TRI for sorting and ELECTRE III for ranking are applied in a real case-study and the results obtained are compared. The case study is a small sanitary sewer system from a Portuguese utility located in the metropolitan area of Lisbon. The problem to investigate is the prioritization of the sewer candidates for rehabilitation. The decision maker (a panel group of specialists) has chosen five assessment measures: water level and maximum flow velocity (hydraulic performance indices), sewer importance and failure repair cost (collapse-related consequences of failure) and the risk of collapse. The results show that the outcomes from ELECTRE III are easier to understand than those from ELECTRE TRI method. Two different sets of weights were used, and the sorting and ranking results from both methods were found to be sensitive to them. ELECTRE TRI method is not straightforward as it involves technical parameters that are difficult to define, such as reference profiles and cut levels.

Moving urban water infrastructure asset management from science into practice

iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own infrastructure asset management (IAM) systems and plans in a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, IST (Technical University of Lisbon) and Addition, a software development company. The water utilities get collective as well as one-on-one support and specific training. They benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference methodologies and standards for IAM planning, in a range of utilities of widely diverse size and context, effectively defining an accepted best practice. This paper discusses the projects format and its advantages, and goes on to describe the main outcomes, including selected cases and final products.