Investigation of Porous Structures for Protection of

Transcription

1 7 Investigation of Porous Structures for Protection of Pipelines against Water Hammer P. Asiaban, M. Fathi Moghadam. PhD Student in Hydraulic Structures, Department of Water Sciences Engineering, Shahid Chamran University of Ahvaz, Iran (Corresponding Author) Prof. of Hydraulic Structures, Department of Water Sciences Engineering, Shahid Chamran University of Ahvaz, Iran (Received Jan. 3, 7 Accepted July 8, 6) To cite this article : Asiaban, P., Fathi Moghadam, M., 8, Using porous structures to protect pipelines against water hammer., 9(5), Doi:.93/wwj (In Persian) Abstract This study was initiated to investigate the use of a porous structure in some parts of a pipeline to protect it against water hammer pressure wave. This study was inspired by the utilization of porous breakwaters which are commonly used to protect coastal areas. To fulfill the main objective of the study, different porous structures were installed in an experimental pipeline fed by a pump. The water hammer was induced by an upstream valve. The homogeneous porous structures were made up of spherical beads or broken rocks in different sizes and filled them in pipes with different lengths and subject them under different water hammer conditions. Results obtained from this study showed that during the first cycle of water hammer wave, the ratio of maximum pressure downstream of porous structure to the corresponding value in upstream is between.6 to.95, respectively. This pressure difference decreased drastically in next cycles. Generally, it can be conclude that an insignificant protection gained from a porous structure in downstream from water hammer; however, the overall pressure fluctuations in the pipe filled with a porous structure was less than a fully open pipe under the same discharge rates and the same water hammer condition. The results showed that porous structures in particular condition could be used to control pressure oscillations in piplines and it is proposed to consider practical aspects of this idea in future researches. Keywords: Porous Structure, Water Hammer, Pressure Fluctuations, Attenuation Rate. Vol. 9, No. 5, 8

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4 75 ρ p d L V µ ε. Re. ). ( D P D.(Abbas, ) ( ). D..(Vereide, 6) (Asiaban et al., 5).....(Erdim et al., 5) (Erdim, 5) p p ρv L 6.8 d p p μvl d p Sphere Packing ε ε 3 ε. Re. ε Re ε.94 ( ) ( ) ( ) Vol. 9, No. 5, 8

5 ..... Fig. Transparent part of the pipe filled with mm spherical beads - Fig. Experimental apparatus (Kim et al., 7) ANSI/API Vol. 9, No.5, 8

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7 Head loss (m) mm sphere packing Discharge (lps) refill trend line erdim carman hicks (a) Porous made of 6 mm spherical beads in two filling conditions (a) Head loss (m) mm sphere packing reverse direction trend line erdim Discharge (lps) (b) Porous made of mm spherical beads in two direction of mounting in flow path (b) Fig 3. Measured and calculated head loss in porous media agains discharge rate based on different filling and flow direction ( ) (Brunone et al., ) Pressure (M H O) upstream homogen mm rev.57lps downstream homogen mm rev.57lps upstream fully open path.59lps downstream fully open path.59lps Time (Sec) Fig 4. Water hammer in pipe with open path and pipe filled with porous -.. / Vol. 9, No.5, 8

8 79.. k...(contractor, 965). / /... (V /g) k a (a(v)+b(v )) b Ratio of max pressures treated data mm sphere pack fully open path 3mm brocken rock mm sphere pack 6mm sphere pack 4mm sphere pack mm borcken rock trend 5 5 k Fig 5. Ratio of maximum pressure against head loss coefficient from downstream to upstream in first cycle of water hammer (Kim et al., 7, Mitosek and Szymkiewicz, 6)....( ).(Tijsseling et al., 8). ( ). Vol. 9, No. 5, 8

9 /. a-. b-. /.. /.. (b- ) (a- ) (Macini et al., ) k.. / /.... (a). (b). (a). (b- ).... Vol. 9, No.5, 8

10 8 Head loss (m H O) mm sphere packing Discharge (lit/sec) a) Head loss in porous made of and 4 mm spherical beads in steady flow (a) mm sphere packing, upstream mm sphere packing, downstream 4mm sphere packing, upstream 4mm sphere packing, downstream 4 3 lit/sec Time (sec) b) Water hammer in a pipe filled with s made of and 4 mm spherical beads in the discharge of lit/sec (b) Fig 6. Comparing water hammer wave in porous media with different head loss factors - Pressure (m H O) Pressure (m H O) Upstream -. lit/sec.5.5 8cm 5cm -5 Time (sec) a) Upstream transmitter,. lit/sec discharge, porous made of mm spherical beads / (a) Pressure (m H O) Time (sec) Downstream -. lit/sec 8cm 5cm.5cm b) ) Downstream transmitter,. lit/secdischarge, porous made of mm spherical beads / (b) Fig 7. Effect of length on water hammer pressure fluctuations during the experiment time Vol. 9, No. 5, 8

11 Time(sec) Fig 8. Dimensionless pressure attenuation envelope during experiment time under different discharge rates in Dimensionless pressure Dimensionless pressure a pipe filled with made of mm spherical beads mm sphere pack mm shphere pack mm spherepack trend Time (sec) Fig 9. Comparison of dimentionless pressure attenuation envelope against experiment time for water hammer in pipe with open path and pipe filled with porous made of mm spheres -.57 lit/sec.34 lit/sec.8 lit/sec.64 lit/sec.... ( ) Vol. 9, No.5, 8

12 / / ( ).. - References Anderson, M.E. & Smith, J.M. 4. Wave attenuation by flexible, idealized salt marsh vegetation. Journal of Coastal Engineering, 83, 8-9. Asiaban, P., Amir, E. & Tahmasebi nasab, M. 5. Simulation of water surface profile in vertically stratified rockfill dams. International Journal of Environmental Research, 9(4), 93-. Vol. 9, No. 5, 8

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