تجزیه و تحلیل سیستم زهکشی سقف سیفونی با بهره گیری از تئوری جریان ناپایدار

Over the past three years a UK EPSRC research programme has been underway at Heriot-Watt University investigating siphonic roof rainwater systems. This text aims to report the principle findings of the project to date. A brief description of experimental and numerical aims is given. The priming procedure which occurs in an idealised system is documented. The test procedures employed are described, and experimental results are illustrated. The framework employed to numerically model the ambient hydraulics is described in some detailed. Conclusions are drawn regarding the operational characteristics of siphonic roof rainwater systems as a whole.

Siphonic roof drainage systems have been in existence for approximately 30 years. In this time, the construction industry has been gradually persuaded by the benefits which these systems offer when compared to the traditional approach. Much of these benefits arise from the fact that systems can become de-pressurised. However, much of the desired benefits only arise at the design condition — typically a storm with a return period in excess of 30 years. When the application was being made for the work reported, it was recognised that the overwhelming majority of rainfall events any siphonic system would have to drain would be well below the design condition. This, coupled with reports of siphonic system failures, convinced the investigators that this was an area worthy of future research.

In summary, the following conclusions may be drawn. • Due to the benefits which siphonic systems have, they are draining an increasing proportion of UK commercial roof space. • There are weaknesses in the current design approach employed by designers. • Arguably weaknesses, and installation problems, have resulted in a number of operational failures. • With the aid of the European siphon rainwater drainage industry, a siphonic test facility has been established at Heriot-Watt University. • A method has been established which may be used to quantify the amount of air entering the test rig. • The priming of the siphonic test rig has been described. • Data collected illustrates that when the systems operate below the design capacity the flow regime is unsteady. • A numerical model has been devised which can represent the priming of a siphonic roof rainwater system.