High-lift siphon drainage by 4-mm internal diameter siphon hoses is a real-time, free-power, and long-term approach for slope drainage. The conventional hydraulics formula for pressurized pipe flow is generally used t...High-lift siphon drainage by 4-mm internal diameter siphon hoses is a real-time, free-power, and long-term approach for slope drainage. The conventional hydraulics formula for pressurized pipe flow is generally used to calculate the single-phase velocity of siphon flow. However, an intensive cavitation phenomenon occurs in the high-lift siphon hose and then a two-phase flow is formed. Research on the velocity of high-lift siphon flow is a prerequisite for the application of siphon drainage with a 4-mm siphon hose. Few investigations of this subject have been carried out. Hence, experiments on the high-lift （8 m〈H0〈10.3 m） siphon drainage in a 4-mm siphon hose were performed. The characteristics of siphon flow under different conditions were ob- served and test data were obtained. Comparisons between test results and calculated results showed that significant errors were given by the hydraulics formula. It is demonstrated that the effect of gas in a siphon hose should be included in the calculation of flow velocity. The findings can be used to determine the number of siphon hoses and layout of siphon drainage holes, and provide valuable information for geotechnical companies.展开更多
Siphonic roof drainage systems (SRDS’s) have been widespread used now for approximately 40 years and are an efficient method of removing rainwater rapidly from roofs. SRDS’s are designed to run full-bore, resulting ...Siphonic roof drainage systems (SRDS’s) have been widespread used now for approximately 40 years and are an efficient method of removing rainwater rapidly from roofs. SRDS’s are designed to run full-bore, resulting in sub-atmospheric system pressures with high hydraulic driving heads and higher system flow velocities than conventionally guttered systems. Hence, SRDS’s normally require far fewer downpipes, and the depressurised conditions also mean that much of the collection pipework can be routed at a high level, thus reducing the extent of any underground pipework. But, they work properly at only one roof run-off rate and therefore suffer from sizing and operational problems including noise and vibration which limit their performance and adoption rate. Climate change is creating situations where normal ranges of rainfall intensity are being frequently exceeded, so the typical:storm ratios (rTS) are large increasing. Current SRDS’s typically operate within a small rTS range of 2. This may have an impact on the future uptake of SRDS’s. This paper describes the development of a novel SRDS which includes a small mobile cap at the roof of outlet appears to offer benefits and avoids sizing problems associated with current SRDS’s. The cap has the potential to avoid noise associated with making and breaking siphonic action through flow modulation. Laboratory scale tests demonstrate the basic feasibility of the cap system and indicate that the cap functions reliably. This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Basic on sizing and design optimiza-tion factors are suggested. The rTS range is increased from approximately 2 to approximately 6.展开更多
基金Project supported by the National ＂Twelfth Five-Year＂ Plan for Science ＆ Technology Support Program of China （No. 2012BAK10B06） and the National Natural Science Foundation of China （No. 41272336）
文摘High-lift siphon drainage by 4-mm internal diameter siphon hoses is a real-time, free-power, and long-term approach for slope drainage. The conventional hydraulics formula for pressurized pipe flow is generally used to calculate the single-phase velocity of siphon flow. However, an intensive cavitation phenomenon occurs in the high-lift siphon hose and then a two-phase flow is formed. Research on the velocity of high-lift siphon flow is a prerequisite for the application of siphon drainage with a 4-mm siphon hose. Few investigations of this subject have been carried out. Hence, experiments on the high-lift （8 m〈H0〈10.3 m） siphon drainage in a 4-mm siphon hose were performed. The characteristics of siphon flow under different conditions were ob- served and test data were obtained. Comparisons between test results and calculated results showed that significant errors were given by the hydraulics formula. It is demonstrated that the effect of gas in a siphon hose should be included in the calculation of flow velocity. The findings can be used to determine the number of siphon hoses and layout of siphon drainage holes, and provide valuable information for geotechnical companies.
文摘Siphonic roof drainage systems (SRDS’s) have been widespread used now for approximately 40 years and are an efficient method of removing rainwater rapidly from roofs. SRDS’s are designed to run full-bore, resulting in sub-atmospheric system pressures with high hydraulic driving heads and higher system flow velocities than conventionally guttered systems. Hence, SRDS’s normally require far fewer downpipes, and the depressurised conditions also mean that much of the collection pipework can be routed at a high level, thus reducing the extent of any underground pipework. But, they work properly at only one roof run-off rate and therefore suffer from sizing and operational problems including noise and vibration which limit their performance and adoption rate. Climate change is creating situations where normal ranges of rainfall intensity are being frequently exceeded, so the typical:storm ratios (rTS) are large increasing. Current SRDS’s typically operate within a small rTS range of 2. This may have an impact on the future uptake of SRDS’s. This paper describes the development of a novel SRDS which includes a small mobile cap at the roof of outlet appears to offer benefits and avoids sizing problems associated with current SRDS’s. The cap has the potential to avoid noise associated with making and breaking siphonic action through flow modulation. Laboratory scale tests demonstrate the basic feasibility of the cap system and indicate that the cap functions reliably. This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Basic on sizing and design optimiza-tion factors are suggested. The rTS range is increased from approximately 2 to approximately 6.
