翻譯原文--利用非恒定流理論分析虹吸式屋面排水系統(tǒng)

1、Building and Environment 36 (2001) 939–948www.elsevier.com/locate/buildenvSiphonic roof drainage system analysis utilising unsteady ?ow theoryS. Arthur ?, J.A. Swa?eldDepartment of Building Engineering and Surveying, Her

2、iot-Watt University, Edinburgh, Scotland, EH14-4AS, UKReceived 17 April 2000; received in revised form 17 April 2000; accepted 12 June 2000AbstractOver the past three years a UK EPSRC research programme has been underway

3、 at Heriot-Watt University investigating siphonic roof rainwater systems. This text aims to report the principle ?ndings of the project to date. A brief description of experimental and numerical aims is given. The primin

4、g 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 d

5、escribed in some detailed. Conclusions are drawn regarding the operational characteristics of siphonic roof rainwater systems as a whole. c ? 2001 Elsevier Science Ltd. All rights reserved.Keywords: Roof drainage; Siphon

6、ic roof drainage system; Method of characteristics1. BackgroundSiphonic roof drainage systems have been in existence for approximately 30 years. In this time, the construc- tion industry has been gradually persuaded by t

7、he bene?ts which these systems o?er when compared to the tradi- tional approach. Much of these bene?ts arise from the fact that systems can become de-pressurised. However, much of the desired bene?ts only arise at the de

8、sign 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 major- ity of rainfall events any siphonic

9、 system would have to drain would be well below the design condition. This, cou- pled with reports of siphonic system failures, convinced the investigators that this was an area worthy of future research.2. Aims and obje

10、ctives of researchSiphonic rainwater drainage depends upon the estab- lishment of full bore ?ow within the pipe network link- ing roof collection outlets to the storm sewer. The re-? Corresponding author. E-mail address:

11、 s.arthur@hw.ac.uk (S. Arthur).placement of conventional multiple downpipes by a net- work of closed conduits o?ers signi?cant advantages to the building designer, as evidenced by the increasing in- stallation of such sy

12、stems in buildings such as airport ter- minals, large warehouses and prestige o?ce developments. However, the establishment of siphonic action depends upon the matching of the network to the expected storm hyetograph and

13、 the maintenance of siphonic conditions throughout the storm event — only one storm matches any particular system. Errors in design may lead to systems operating in an ine?cient, non-siphonic mode, or to insuf- ?cient ca

14、pacity (?ooding). Generation of negative pressure transients may lead to system failure due to pipewall col- lapse [1]. While siphonic systems have been installed in the UK over the past decade, there is no recognised de

15、sign standard, and system design is based on steady state cal- culations which assume a near instantaneous steady full bore entrained air free ?ow. The aim of the work re- ported was to develop an unsteady ?ow model whic

16、h could simulate conditions within an idealised siphonic roof rainwater drainage system driven by a storm hyetograph during priming. This would enable ?ow conditions within the rainwater drainage system to be represented

17、 within a idealised siphonic drainage system, from initial free sur- face ?ow as the storm develops, through a two-phase ?ow stage, while air entertained, or initially present, in the system is ?ushed out, until the full

18、 bore ?ow0360-1323/01/$ - see front matter c ? 2001 Elsevier Science Ltd. All rights reserved. PII: S 0360-1323(00)00049-4S. Arthur, J.A. Swa?eld / Building and Environment 36 (2001) 939–948 941Fig. 1. Schematic diagram

19、of a test rig con?guration illustrating the main dimensions.Fig. 2. Ambient pressures in the system for a steady gutter in?ow rate of 42% of the measured capacity of the system illustrated in Fig. 1. The ?gure illustrate

20、s how, under particular conditions, a cyclic pressure regime may be established in the system. The frequency of the cyclic response of the system is related to the rate of in?ow, and the lengths of the horizontal and ver

21、tical pipework.5. Current design practiceCurrently, siphonic roof drainage systems are designed to accommodate a speci?ed storm which ?lls, and primes, the whole system rapidly with 100% water. This assump- tion means th

22、at the system may be designed easily using elementary steady-state hydraulic relationships. The steady ?ow energy equation is used almost univer- sally [3] as the backbone of the design procedure for siphonic roof draina

23、ge systems. The pressure drop between any two points X and Y can be determinedusing ?H + Q22gA2 +z?Point X ??H + Q22gA2 +z?Point Y = ?HX;Y:(1)The pressure drop between two points, ?HX;Y, is ac- counted for by losses due